+publisher:"Indian Institute of Science" +contributor:("Ravikrishna, R V")

Indian Institute of Science

1. Tewari, Sumit. Study Of Liquid Fuel Film Transport And Its Effect On Cold Start Hydrocarbon Emissions In A Carburetted Engine.

Degree: MSc Engg, Faculty of Engineering, 2013, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/1908

► The present work is concerned with fundamental studies on the liquid fuel transport in the intake manifold of small carburetted engines. This work is motivated… (more)

Subjects/Keywords: Automobile Emission Control; Hydrocarbon Emission Control; Carburetted Engines; Automobile Engines; Shadowgraphy; Planar Laser Induced Fluorescence (PLIF); Fuel Film; Gasoline Film; Carburettor; Liquid Fuel Transport; Heat Engineering

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Tewari, S. (2013). Study Of Liquid Fuel Film Transport And Its Effect On Cold Start Hydrocarbon Emissions In A Carburetted Engine. (Masters Thesis). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/1908

Chicago Manual of Style (16^th Edition):

Tewari, Sumit. “Study Of Liquid Fuel Film Transport And Its Effect On Cold Start Hydrocarbon Emissions In A Carburetted Engine.” 2013. Masters Thesis, Indian Institute of Science. Accessed March 04, 2021. http://etd.iisc.ac.in/handle/2005/1908.

MLA Handbook (7^th Edition):

Tewari, Sumit. “Study Of Liquid Fuel Film Transport And Its Effect On Cold Start Hydrocarbon Emissions In A Carburetted Engine.” 2013. Web. 04 Mar 2021.

Vancouver:

Tewari S. Study Of Liquid Fuel Film Transport And Its Effect On Cold Start Hydrocarbon Emissions In A Carburetted Engine. [Internet] [Masters thesis]. Indian Institute of Science; 2013. [cited 2021 Mar 04]. Available from: http://etd.iisc.ac.in/handle/2005/1908.

Council of Science Editors:

Tewari S. Study Of Liquid Fuel Film Transport And Its Effect On Cold Start Hydrocarbon Emissions In A Carburetted Engine. [Masters Thesis]. Indian Institute of Science; 2013. Available from: http://etd.iisc.ac.in/handle/2005/1908

Indian Institute of Science

2. Sinha, Anubhav. Experimental and Numerical Studies on Spray in Crossflow.

Degree: PhD, Faculty of Engineering, 2018, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/3058

► The phenomenon of spray in crossflow is of relevance in gas turbine combustor development. The current work focuses on spray in crossflow rather than liquid… (more)

▼ The phenomenon of spray in crossflow is of relevance in gas turbine combustor development. The current work focuses on spray in crossflow rather than liquid jet in crossflow from the standpoint of enhancing fuel dispersion and mixing. Specifically, the first part of the work involves study of spray structure, droplet sizing, and velocimetry for sprays of water and ethanol in a crossflow under ambient conditions. Laser-based diagnostic techniques such as Particle/Droplet Image Analysis (PDIA) and Particle Tracking Velocimetry (PTV) are utilized. Using spray structure images, trajectory equations are derived by multi-variable regression. It is found that the spray trajectory depends only on the two-phase momentum ratio and is independent of other flow parameters. A generalized correlation for the spray trajectory is proposed incorporating the liquid surface tension, which is found to be effective for our data, with water and ethanol, as well as data on Jet-A from the literature for a wide variety of operating conditions. An interesting phenomenon of spatial bifurcation of the spray is observed at low Gas-to-Liquid ratios (GLRs). The reason for this phenomenon is attributed to the co-existence of large and highly deformed ligaments along with much smaller droplets at low GLR conditions. The smaller droplets lose their vertical momentum rapidly leading to lower penetration, whereas the larger ligaments/droplets penetrate much more due to their larger momentum leading to a spatial separation of the two streams. The second part of the study focuses on evaporating sprays in preheated crossflow. Experiments are conducted using ethanol, decane, Jet-A1 fuel, and a two-component surrogate for Jet-A1 fuel. The crossflow air is heated up to 418 K and the effect of evaporation is studied on spray trajectory and droplet sizes. Measured droplet sizes and velocities at two successive locations are used to estimate droplet evaporation lifetimes. Evaporation constant for the d2 law derived from the droplet lifetimes represents the first-ever data for the above-mentioned liquids under forced convective conditions. This data can be used to validate multi-component droplet evaporation models. The last part of the study focuses on Large Eddy Simulations (LES) of the spray in crossflow. The near-nozzle spray structure is investigated experimentally to obtain droplet size and velocity distributions that are used as inputs to the computational model. For the spray in crossflow under ambient conditions, trajectory and droplet sizes at different locations are compared with experimental results. While the predicted trajectory is found to be in good agreement with data, the predicted droplet sizes are larger than the measured values. This is attributed to the implicit assumption in the secondary breakup model that the droplets are spherical, whereas the experimental data in the near-nozzle region clearly shows presence of mostly ligaments and non-spherical droplets, especially for the low GLR cases. A modified breakup model is found to lead to… Advisors/Committee Members: Ravikrishna, R V (advisor).

Subjects/Keywords: Crossflow Spray; Fuel Injection; Gar Turbine Combustors; Spray Injection; Spray Trajectory; Airblast Sprays; Spray Droplet Sizing; Crossflow Spray Simulation; Droplet Distortion; Large Eddy Simulations (LES); Particle/Droplet Image Analysis (PDIA); Particle Tracking Velocimetry (PTV); Mechanical Engineering

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Sinha, A. (2018). Experimental and Numerical Studies on Spray in Crossflow. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/3058

Chicago Manual of Style (16^th Edition):

Sinha, Anubhav. “Experimental and Numerical Studies on Spray in Crossflow.” 2018. Doctoral Dissertation, Indian Institute of Science. Accessed March 04, 2021. http://etd.iisc.ac.in/handle/2005/3058.

MLA Handbook (7^th Edition):

Sinha, Anubhav. “Experimental and Numerical Studies on Spray in Crossflow.” 2018. Web. 04 Mar 2021.

Vancouver:

Sinha A. Experimental and Numerical Studies on Spray in Crossflow. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2018. [cited 2021 Mar 04]. Available from: http://etd.iisc.ac.in/handle/2005/3058.

Council of Science Editors:

Sinha A. Experimental and Numerical Studies on Spray in Crossflow. [Doctoral Dissertation]. Indian Institute of Science; 2018. Available from: http://etd.iisc.ac.in/handle/2005/3058

Indian Institute of Science

3. Deshmukh, Devendra. Studies On Automization And Sprays Of Plant Oil Biofuels Using Laser-Based Diagnostics.

Degree: PhD, Faculty of Engineering, 2014, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/2419

► Atomization characteristics of liquid fuel sprays control combustion efficiency and emissions in engines. The present work is motivated by the need to study the atomization… (more)

▼ Atomization characteristics of liquid fuel sprays control combustion efficiency and emissions in engines. The present work is motivated by the need to study the atomization and spray structure of vegetable oil biofuels for which no data in the literature exists. In this work, various laser-based diagnostic techniques such as laser shadowgraphy, Particle/Droplet Image Analysis (PDIA) and Laser Sheet Dropsizing (LSD) are applied for studying atomization characteristics, tip penetration, droplet size and liquid volume fraction of Pongamia vegetable oil (SVO) and its blends with diesel. A constant volume high pressure spray visualization chamber is designed and fabricated to study SVO sprays at high gas pressure and temperature conditions. This optical chamber can be used for gas pressures up to 60 bar and temperatures up to 600 K. Optical access inside the chamber is provided through four quartz windows to perform various optical spray diagnostic studies. A high pressure spray injection facility based on components of common rail diesel injection system is designed. This facility can provide an injection pressure of up to 1700 bar with independent control over injection duration and timing. A marked difference is observed between diesel and SVO spray structures under atmospheric gas pressure condition. A very interesting observation related to the behavior of 100% SVO fuel when sprayed into atmospheric pressure is the presence of an intact liquid core even at injection pressure as high as 1600 bar. The presence of liquid core at high injection pressures is attributed to the high viscosity of SVOs and the non-Newtonian behavior of these oils under high pressure and shear. The spray characterization of the oil and its blends at high gas pressure shows that although the atomization is dramatically different from that at atmospheric gas pressure, it is still incomplete even at very high injection pressures. For a gas pressure of 30 bar, it is observed that the Sauter Mean Diameter (SMD) for Pongamia oil is more than twice that of diesel. A new method of simultaneously obtaining two-dimensional droplet size and quantitative liquid volume fraction data in sprays has been developed. Measurements with this method reveal a higher liquid volume fraction at the central axis of spray for Pongamia oil compared to that of diesel indicating potentially poor air-fuel mixing. The experimental data obtained and the spray tip penetration correlations developed for the vegetable oils and blends serve as useful inputs for fuel injection and engine system designers. Advisors/Committee Members: Ravikrishna, R V (advisor).

Subjects/Keywords: Liquid Fuel Sprays; Combustion Efficiency; Laser-based Diagnostics; Vegetable Oil Biofuels - Spray Atomization; Vegetable Oil Biofuels - Spray Structure; Plant Oil Biofuels; High Pressure Spray Visualization Chamber; Straight Vegetable Oil Sprays; Biofuels; Heat Engineering

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Deshmukh, D. (2014). Studies On Automization And Sprays Of Plant Oil Biofuels Using Laser-Based Diagnostics. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/2419

Chicago Manual of Style (16^th Edition):

Deshmukh, Devendra. “Studies On Automization And Sprays Of Plant Oil Biofuels Using Laser-Based Diagnostics.” 2014. Doctoral Dissertation, Indian Institute of Science. Accessed March 04, 2021. http://etd.iisc.ac.in/handle/2005/2419.

MLA Handbook (7^th Edition):

Deshmukh, Devendra. “Studies On Automization And Sprays Of Plant Oil Biofuels Using Laser-Based Diagnostics.” 2014. Web. 04 Mar 2021.

Vancouver:

Deshmukh D. Studies On Automization And Sprays Of Plant Oil Biofuels Using Laser-Based Diagnostics. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2014. [cited 2021 Mar 04]. Available from: http://etd.iisc.ac.in/handle/2005/2419.

Council of Science Editors:

Deshmukh D. Studies On Automization And Sprays Of Plant Oil Biofuels Using Laser-Based Diagnostics. [Doctoral Dissertation]. Indian Institute of Science; 2014. Available from: http://etd.iisc.ac.in/handle/2005/2419

Indian Institute of Science

4. Prabhu, Nishikant Madhusudan. Fuel Filim Visualization And Measurement In The Inlet Manifold Of A Carbureted Spark-Ignition Engine.

Degree: MSc Engg, Faculty of Engineering, 2013, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/2251

► In order to meet future emission norms for small carbureted SI engines, such as those used on motorcycles in India, there is a need to… (more)

▼ In order to meet future emission norms for small carbureted SI engines, such as those used on motorcycles in India, there is a need to study mixture preparation, specifically the two-phase flow exiting the carburetor and entering the inlet manifold. A fully functional, modular experimental rig is designed and erected for performing both qualitative and quantitative flow visualization. The vibrations of the engine are minimized to reduce their effect on the flow. A special, optically accessible tube of square cross-section is added between the carburetor and the inlet manifold, to enable the visualization of flow at the exit of the carburetor. An electronic circuit to obtain a signal for the engine crank angle and convert it to a standard TTL pulse, for use on standard imaging systems to capture cycle resolved-images is also designed. The flow in the optical section is qualitatively visualized using high and low speed cameras. The resulting images and movies show two modes of fuel transport within the inlet manifold, one of which is in the form of a dense cloud of fine fuel droplets during some part of the intake stroke. The second mode is in the form of a film at all times in the cycle, along the lower surface of the inlet manifold during idling and along vertical walls under loaded conditions. Recirculation is seen on the vertical walls of the manifold during idling and under load. Finally, the thickness of the fuel film in the optical section at the exit of the carburetor is measured, using PLIF. This part of the study also reveals that there is a film on upper surface of the optical section, at all loads and speeds. This film is lesser than the resolution of measurement for low loads, and increases to 0.5 mm in the case of highest load and speed attained at full throttle. In contrast to the loaded conditions, during idling, the film occurs on the lower surface of the manifold and its thickness is highest (1 mm.). The film is also present throughout the cycle during idling and all load-speed conditions, suggesting that the mixture that goes into the engine has a significant part of fuel in liquid form. Advisors/Committee Members: Ravikrishna, R V (advisor).

Subjects/Keywords: Spark-Ignition Engine - Inlet; Fuel (Machine Engineering); Motorcycles; Flow Visualization; Carbureted Engines - Fuel Transport; Carbureted Spark-Ignition Engines; Planar Laser Induced Fluorescence Imaging; Engine-Inlet; PLIF; Fuel Filim Visualization; Automobile Engineering

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Prabhu, N. M. (2013). Fuel Filim Visualization And Measurement In The Inlet Manifold Of A Carbureted Spark-Ignition Engine. (Masters Thesis). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/2251

Chicago Manual of Style (16^th Edition):

Prabhu, Nishikant Madhusudan. “Fuel Filim Visualization And Measurement In The Inlet Manifold Of A Carbureted Spark-Ignition Engine.” 2013. Masters Thesis, Indian Institute of Science. Accessed March 04, 2021. http://etd.iisc.ac.in/handle/2005/2251.

MLA Handbook (7^th Edition):

Prabhu, Nishikant Madhusudan. “Fuel Filim Visualization And Measurement In The Inlet Manifold Of A Carbureted Spark-Ignition Engine.” 2013. Web. 04 Mar 2021.

Vancouver:

Prabhu NM. Fuel Filim Visualization And Measurement In The Inlet Manifold Of A Carbureted Spark-Ignition Engine. [Internet] [Masters thesis]. Indian Institute of Science; 2013. [cited 2021 Mar 04]. Available from: http://etd.iisc.ac.in/handle/2005/2251.

Council of Science Editors:

Prabhu NM. Fuel Filim Visualization And Measurement In The Inlet Manifold Of A Carbureted Spark-Ignition Engine. [Masters Thesis]. Indian Institute of Science; 2013. Available from: http://etd.iisc.ac.in/handle/2005/2251

Indian Institute of Science

5. Prasad, Boggavarapu V V S U. Experimental Studies on Biodiesel Spray Characteristics : Effects of Evaporation & Nozzle Cavitation.

Degree: PhD, Faculty of Engineering, 2018, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/3738

► Vegetable oil methyl esters obtained by transesterification of vegetable oils are considered to be suitable alternative fuels for diesel engines. However, higher viscosity, surface tension… (more)

▼ Vegetable oil methyl esters obtained by transesterification of vegetable oils are considered to be suitable alternative fuels for diesel engines. However, higher viscosity, surface tension and boiling temperatures of biodiesels may adversely affect spray characteristics as compared to those of diesel. Thus, spray characteristics of Jatropha Methyl Ester (JME) are studied by comparing them to those of diesel in a high-pressure chamber with optical access to simulate the actual in-cylinder conditions. Also, the effect of inner-nozzle cavitation on JME and diesel sprays is studied by utilizing two nozzles, one with sharp entry-radius and the other with larger entry-radius. Finally, spray characteristics of surrogate fuels such as n-dodecane and n-hexadecane are also studied. The first part of the work concerning precise measurements of inner-nozzle geometry revealed that one of the nozzles has a hole diameter of 190-µm and entry-radius of around 70-µm, while the other has a hole diameter of 208-µm and entry-radius of around 10-µm. Injection rate-shape and coefficient of discharge for JME and diesel flow through the two nozzles were then measured. It was observed that while the coefficients of discharge (Cd) are almost identical for JME and diesel, the nozzle with entry radius of 10-µm exhibited around 20% lower Cd than that of the entry-radius of 70-µm. This observation coupled with insight from complementary CFD simulations of inner-nozzle flow showed that the lower Cd of the nozzle with entry-radius of 10-µm could be attributed to inner-nozzle cavitation. The second part of the work involved measurement of non-evaporating spray characteristics including spray-tip penetration, spray-cone angle and droplet size measurement under realistic operating conditions using techniques such as Shadowgraphy and Particle/Droplet Imaging Analysis (PDIA). The non-evaporating spray of the fuels are studied by injecting them using a common-rail fuel injection system into the high-pressure chamber maintained at room temperature. Experimental results show that JME is associated with a slightly faster spray-tip penetration and narrow spray-cone angle indicating inferior spray atomization which is confirmed by around 5% larger droplet sizes. Slower spray-tip penetration, wider spray-cone angle and around 5% smaller droplet sizes are observed for the spray from the cavitating nozzle. Thus, the inner nozzle cavitation is observed to improve the atomization of diesel and JME sprays. The differences in spray characteristics of JME and diesel reduce as the injection pressure increases. The spray-tip penetrations of both surrogates are observed to almost match that of diesel. The third part of the work involved measurements of evaporating spray liquid length, vapour penetration and spread angle for JME, diesel and surrogates at conditions of 50 bar chamber pressure and 900 K temperature. It is observed that the JME exhibits around 16% longer liquid length than that of diesel. The liquid length of n-dodecane is significantly lower than that of… Advisors/Committee Members: Ravikrishna, R V (advisor).

Subjects/Keywords: Biodiesel Spray - Evaporation Effect; Biodiesel Spray; Jatropha Methyl Ester (JME); Macroscopic Structure - Droplet Size; Inner-Nozzle Geometry; Inner-nozzle Flow; Particle/Droplet Imaging Analysis (PDIA); Biodiesel Spray Characteristics; Nozzel Cavitation Effect; Mechanical Engineering

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Prasad, B. V. V. S. U. (2018). Experimental Studies on Biodiesel Spray Characteristics : Effects of Evaporation & Nozzle Cavitation. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/3738

Chicago Manual of Style (16^th Edition):

Prasad, Boggavarapu V V S U. “Experimental Studies on Biodiesel Spray Characteristics : Effects of Evaporation & Nozzle Cavitation.” 2018. Doctoral Dissertation, Indian Institute of Science. Accessed March 04, 2021. http://etd.iisc.ac.in/handle/2005/3738.

MLA Handbook (7^th Edition):

Prasad, Boggavarapu V V S U. “Experimental Studies on Biodiesel Spray Characteristics : Effects of Evaporation & Nozzle Cavitation.” 2018. Web. 04 Mar 2021.

Vancouver:

Prasad BVVSU. Experimental Studies on Biodiesel Spray Characteristics : Effects of Evaporation & Nozzle Cavitation. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2018. [cited 2021 Mar 04]. Available from: http://etd.iisc.ac.in/handle/2005/3738.

Council of Science Editors:

Prasad BVVSU. Experimental Studies on Biodiesel Spray Characteristics : Effects of Evaporation & Nozzle Cavitation. [Doctoral Dissertation]. Indian Institute of Science; 2018. Available from: http://etd.iisc.ac.in/handle/2005/3738

Indian Institute of Science

6. Sivaprakasam, M. Numerical Simulations Of Two-Phase Reacting Flow In A Cavity Combustor.

Degree: MSc Engg, Faculty of Engineering, 2013, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/2011

► In the present work, two phase reacting flow in a single cavity Trapped Vortex Combustor (TVC) is studied at atmospheric conditions. KIVA-3V, numerical program for… (more)

▼ In the present work, two phase reacting flow in a single cavity Trapped Vortex Combustor (TVC) is studied at atmospheric conditions. KIVA-3V, numerical program for simulating three dimensional compressible reacting flows with sprays using Lagrangian-Drop Eulerian-fluid procedure is used. The stochastic discrete droplet model is used for simulating the liquid spray. In each computational cell, it is assumed that the volume occupied by the liquid phase is very small. But this assumption of very low liquid volume fraction in a computational cell is violated in the region close to the injection nozzle. This introduces grid dependence in predictions of liquid phase in the region close to the nozzle in droplet collision algorithm, and in momentum coupling between the liquid and the gas phase. Improvements are identified to reduce grid dependence of these algorithms and corresponding changes are made in the standard KIVA-3V models. Pressure swirl injector which produces hollow cone spray is used in the current study along with kerosene as the liquid fuel. Modifications needed for modelling pressure swirl atomiser are implemented. The Taylor Analogy Breakup (TAB) model, the standard model for predicting secondary breakup is improved with modifications required for low pressure injectors. The pressure swirl injector model along with the improvements is validated using experimental data for kerosene spray from the literature. Simulations of two phase reacting flow in a single cavity TVC are performed and the temperature distribution within the combustor is studied. In order to identify an optimum configuration with liquid fuel combustion, the following parameters related to fuel and air such as cavity fuel injection location, cavity air injection location, Sauter Mean Diameter (SMD) of injected fuel droplets, velocity of the fuel injected are studied in detail in order to understand the effect of these parameters on combustion characteristics of a single cavity TVC. Advisors/Committee Members: Ravikrishna, R V (advisor).

Subjects/Keywords: Trapped Vortex Combustor (TVC); Cavity Combustor; Trapped Vortex Combustor - Flow Modelling; Ramjet Engines; Trapped Vortex Combustor - Two Phase Reacting Flow; Cavity Combustor - Reacting Flow - Numerical Simulations; Taylor Analogy Breakup (TAB); Heat Engineering

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Sivaprakasam, M. (2013). Numerical Simulations Of Two-Phase Reacting Flow In A Cavity Combustor. (Masters Thesis). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/2011

Chicago Manual of Style (16^th Edition):

Sivaprakasam, M. “Numerical Simulations Of Two-Phase Reacting Flow In A Cavity Combustor.” 2013. Masters Thesis, Indian Institute of Science. Accessed March 04, 2021. http://etd.iisc.ac.in/handle/2005/2011.

MLA Handbook (7^th Edition):

Sivaprakasam, M. “Numerical Simulations Of Two-Phase Reacting Flow In A Cavity Combustor.” 2013. Web. 04 Mar 2021.

Vancouver:

Sivaprakasam M. Numerical Simulations Of Two-Phase Reacting Flow In A Cavity Combustor. [Internet] [Masters thesis]. Indian Institute of Science; 2013. [cited 2021 Mar 04]. Available from: http://etd.iisc.ac.in/handle/2005/2011.

Council of Science Editors:

Sivaprakasam M. Numerical Simulations Of Two-Phase Reacting Flow In A Cavity Combustor. [Masters Thesis]. Indian Institute of Science; 2013. Available from: http://etd.iisc.ac.in/handle/2005/2011

Indian Institute of Science

7. Krishna, S. Laser-based Diagnostics and Numerical Simulations of Syngas Combustion in a Trapped Vortex Combustor.

Degree: PhD, Faculty of Engineering, 2017, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/2768

► Syngas consisting mainly of a mixture of carbon monoxide, hydrogen and other diluents, is an important fuel for power generation applications since it can be… (more)

▼ Syngas consisting mainly of a mixture of carbon monoxide, hydrogen and other diluents, is an important fuel for power generation applications since it can be obtained from both biomass and coal gasification. Clean coal technologies require stable and efficient operation of syngas-fired gas turbines. The trapped vortex combustor (TVC) is a relatively new gas turbine combustor concept which shows tremendous potential in achieving stable combustion under wide operating conditions with low emissions. In the present work, combustion of low calorific value syngas in a TVC has been studied using in-situ laser diagnostic techniques and numerical modeling. Specifically, this work reports in-situ measurements of mixture fraction, OH radical concentration and velocity in a single cavity TVC, using state-of-the art laser diagnostic techniques such as Planar Laser-induced Fluorescence (PLIF) and Particle Image Velocimetry (PIV). Numerical simulations using the unsteady Reynolds-averaged Navier-Stokes (URANS) and Large Eddy Simulation (LES) approaches have also been carried out to complement the experimental measurements. The fuel-air momentum flux ratio (MFR), where the air momentum corresponds to that entering the cavity through a specially-incorporated flow guide vane, is used to characterize the mixing. Acetone PLIF experiments show that at high MFRs, the fuel-air mixing in the cavity is very minimal and is enhanced as the MFR reduces, due to a favourable vortex formation in the cavity, which is corroborated by PIV measurements. Reacting flow PIV measurements which differ substantially from the non-reacting cases primarily because of the gas expansion due to heat release show that the vortex is displaced from the centre of the cavity towards the guide vane. The MFR was hence identified as the controlling parameter for mixing in the cavity. Quantitative OH concentration contours showed that at higher MFRs 4.5, the fuel jet and the air jet stream are separated and a flame front is formed at the interface. As the MFR is lowered to 0.3, the fuel air mixing increases and a flame front is formed at the bottom and downstream edge of the cavity where a stratified charge is present. A flame stabilization mechanism has been proposed which accounts for the wide MFRs and premixing in the mainstream as well. LES simulations using a flamelet-based combustion model were conducted to predict mean OH radical concentration and velocity along with URANS simulations using a modified Eddy dissipation concept model. The LES predictions were observed to agree closely with experimental data, and were clearly superior to the URANS predictions as expected. Performance characteristics in the form of exhaust temperature pattern factor and pollutant emissions were also measured. The NOx emissions were found to be less than 2 ppm, CO emissions below 0.2% and HC emissions below 700 ppm across various conditions. Overall, the in-situ experimental data coupled with insight from simulations and the exhaust measurements have confirmed the advantages of using… Advisors/Committee Members: Ravikrishna, R V (advisor).

Subjects/Keywords: Trapped Vortex Combustor; Gas Turbine Combustion; Biomass Gasification; Syngas Combustion; Particle Image Velocimetry (PVC); Planar Laser Induced Fluorescence; Coal Gasification; Combustion; OH PLIF Diagnostics; Syngas Fired Gas Turbines; Trapped Vortex Combustor Rig; TVC Combustion; Reynolds-averaged Navier-Stokes (URANS); Large Eddy Simulation (LES); Mechanical Engineering

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Krishna, S. (2017). Laser-based Diagnostics and Numerical Simulations of Syngas Combustion in a Trapped Vortex Combustor. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/2768

Chicago Manual of Style (16^th Edition):

Krishna, S. “Laser-based Diagnostics and Numerical Simulations of Syngas Combustion in a Trapped Vortex Combustor.” 2017. Doctoral Dissertation, Indian Institute of Science. Accessed March 04, 2021. http://etd.iisc.ac.in/handle/2005/2768.

MLA Handbook (7^th Edition):

Krishna, S. “Laser-based Diagnostics and Numerical Simulations of Syngas Combustion in a Trapped Vortex Combustor.” 2017. Web. 04 Mar 2021.

Vancouver:

Krishna S. Laser-based Diagnostics and Numerical Simulations of Syngas Combustion in a Trapped Vortex Combustor. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2017. [cited 2021 Mar 04]. Available from: http://etd.iisc.ac.in/handle/2005/2768.

Council of Science Editors:

Krishna S. Laser-based Diagnostics and Numerical Simulations of Syngas Combustion in a Trapped Vortex Combustor. [Doctoral Dissertation]. Indian Institute of Science; 2017. Available from: http://etd.iisc.ac.in/handle/2005/2768

Indian Institute of Science

8. Mohan, Avulapati Madan. Air-Assited Atomization Strategies For High Viscosity Fuels.

Degree: PhD, Faculty of Engineering, 2016, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/2506

► Atomization of fuel is an important pre-requisite for efficient combustion in devices such as gas turbines, liquid propellant rocket engines, internal combustion engines and incinerators.… (more)

▼ Atomization of fuel is an important pre-requisite for efficient combustion in devices such as gas turbines, liquid propellant rocket engines, internal combustion engines and incinerators. The overall objective of the present work is to explore air-assisted atomization strategies for high viscosity fuels and liquids. Air-assisted atomization is a twin-fluid atomization method in which energy of the gas is used to assist the atomization of liquids. Broadly, three categories of air-assisted injection, i.e., effervescent, impinging jet and pre-filming air-blast are studied. Laser-based diagnostics are used to characterize the spray structure in terms of cone angle, penetration and drop size distribution. A backlit direct imaging method is used to study the macroscopic spray characteristics such as spray structure and spray cone angle while the microscopic characteristics are measured using the Particle/droplet imaging analysis (PDIA) technique. Effervescent atomization is a technique in which a small amount of gas is injected into the liquid at high pressure in the form of bubbles. Upon injection, the two-phase mixture expands rapidly and shatters the liquid into droplets and ligaments. Effervescent spray characteristics of viscous fuels such as Jatropha and Pongamia pure plant oils and diesel are studied. Measurements are made at various gas-to-liquid ratios (GLRs) and injection pressures. A Sauter Mean Diameter (SMD) of the order of 20 µm is achieved at an injection pressure of 10 bar and GLR of 0.2 with viscous fuels. An image-based method is proposed and applied to evaluate the unsteadiness in the spray. A map indicating steady/unsteady regime of operation has been generated. An optically accessible injector tip is developed which has enabled visualization of the two-phase flow structure inside the exit orifice of the atomizer. An important contribution of the present work is the correlation of the two-phase flow regime in the orifice with the external spray structure. For viscous fuels, the spray is observed to be steady only in the annular two-phase flow regime. Unexpanded gas bubbles observed in the liquid core even at an injection pressure of 10 bar indicate that the bubbly flow regime may not be beneficial for high viscosity oils. A novel method of external mixing twin-fluid atomization is developed. In this method, two identical liquid jets impinging at an angle are atomized using a gas jet. The effect of liquid viscosity (1 cP to 39 cP) and surface tension (22 mN/m to 72 mN/m) on this mode of atomization is studied by using water-glycerol and water-ethanol mixtures, respectively. An SMD of the order of 40 µm is achieved for a viscosity of 39 cP at a GLR of 0.13 at a liquid pressure of 8 bar and gas pressure of 5 bar. It is observed that the effect of liquid properties is minimal at high GLRs where the liquid jets are broken before the impingement as in the prompt atomization mode. Finally, a pre-filming air-blast technique is explored for transient spray applications. An SMD of 22 µm is obtained with diesel… Advisors/Committee Members: Ravikrishna, R V (advisor).

Subjects/Keywords: Motor Fuels; High Viscosity Fuels - Atomization; Effervescent Atomization; Air Assisted Atomization; Impinging Jet Atomization; Twin Fluid Atomization; Biofuels - Atomization; Pre-Filming Air-Blast; Pure Plant Oils - Atomization; Biofuels - Alternative Fuels; Jatropha Oil; Alternative Fuel-gas Turbines; Mechanical Engineering

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Mohan, A. M. (2016). Air-Assited Atomization Strategies For High Viscosity Fuels. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/2506

Chicago Manual of Style (16^th Edition):

Mohan, Avulapati Madan. “Air-Assited Atomization Strategies For High Viscosity Fuels.” 2016. Doctoral Dissertation, Indian Institute of Science. Accessed March 04, 2021. http://etd.iisc.ac.in/handle/2005/2506.

MLA Handbook (7^th Edition):

Mohan, Avulapati Madan. “Air-Assited Atomization Strategies For High Viscosity Fuels.” 2016. Web. 04 Mar 2021.

Vancouver:

Mohan AM. Air-Assited Atomization Strategies For High Viscosity Fuels. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2016. [cited 2021 Mar 04]. Available from: http://etd.iisc.ac.in/handle/2005/2506.

Council of Science Editors:

Mohan AM. Air-Assited Atomization Strategies For High Viscosity Fuels. [Doctoral Dissertation]. Indian Institute of Science; 2016. Available from: http://etd.iisc.ac.in/handle/2005/2506

Indian Institute of Science

9. Pandey, Sunil Kumar. Exploration And Assessment of HCCI Strategies for a Multi-Cylinder Heavy-Duty Diesel Engine.

Degree: PhD, Faculty of Engineering, 2017, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/2720

► Homogeneous Charge Compression Ignition (HCCI) combustion is an alternative combustion mode in which the fuel is homogeneously mixed with air and is auto-ignited by compression.… (more)

▼ Homogeneous Charge Compression Ignition (HCCI) combustion is an alternative combustion mode in which the fuel is homogeneously mixed with air and is auto-ignited by compression. Due to charge homogeneity, this mode is characterized by low equivalence ratios and temperatures giving simultaneously low nitric oxide (NOx) and soot in diesel engines. The conventional problem of NOx-soot trade-off is avoided in this mode due to absence of diffusion combustion. This mode can be employed at part load conditions while maintaining conventional combustion at high load thus minimizing regulatory cycle emissions and reducing cost of after-treatment systems. The present study focuses on achieving this mode in a turbocharged, common rail, direct injection, four-cylinder, heavy duty diesel engine. Specifically, the work involves a combination of three-dimensional CFD simulations and experiments on this engine to assess both traditional and novel strategies related to fuel injection. The first phase of the work involved a quasi-dimensional simulation of the engine to assess potential of achieving HCCI. This was done using a zero-dimensional, single-zone HCCI combustion model with n-heptane skeletal chemistry along with a one-dimensional model of intake and exhaust systems. The feasibility of operation with realistic knock values with high EGR rate of 60% was observed. The second aspect of the work involved three-dimensional CFD simulations of the in-cylinder process with wall film prediction to evaluate injection strategies associated with Early Direct Injection (EDI). The extended Coherent Flame Model-3Zone (ECFM-3Z) was employed for combustion simulation of conventional CI and EDI, and was validated with experimental in-cylinder pressure data from the engine. A new Uniformity Index (UI) parameter was defined to assess charge homogeneity. Results showed significant in-homogeneity and presence of wall film for EDI. Simulations were conducted to assess improvement of charge homogeneity by several strategies; narrow spray cone angle, injection timing, multiple injections, intake air heating, Port Fuel Injection (PFI) as well as combination of PFI and EDI. The maximum UI achieved by EDI was 0.78. The PFI strategy could achieve UI of 0.95; however, up to 50% of fuel remained trapped in the port after valve closure. This indicated that except EDI, none of the above-mentioned strategies could help achieve the benefits of the HCCI mode. The third part of the work involved engine experimentation to assess the EDI strategy. This strategy produced lower soot than that of conventional CI combustion with very short combustion duration, but led to high knock and NOx which is attributed to pool fire burning phenomenon of the wall film, as confirmed by CFD. An Optimized EDI (OptimEDI) strategy was then developed based on results of CFD and Design of Experiments. The Optim EDI consisted of triple injections with split ratio of 41%-45%-14% and advancing the first injection. This strategy gave 20% NOx and soot reduction over the conventional CI… Advisors/Committee Members: Ravikrishna, R V (advisor).

Subjects/Keywords: Homogeneous Charge Compression Ignition Engines (HCCI); Low Temperature Combustion; Multi-Cylinder Heavy-Duty Diesel Engines; Diesel Motor; Diesel Engines; Early Direct Injection; Air-Assisted Injection; Combustion; Diesel Homogeneous Charge Compression Ignition; Diesel Fuels; Diesel-Fueled Engines; Fuel Injection; Internal Combustion Engines; Computational Fluid Dynamics; Mechanical Engineering

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Pandey, S. K. (2017). Exploration And Assessment of HCCI Strategies for a Multi-Cylinder Heavy-Duty Diesel Engine. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/2720

Chicago Manual of Style (16^th Edition):

Pandey, Sunil Kumar. “Exploration And Assessment of HCCI Strategies for a Multi-Cylinder Heavy-Duty Diesel Engine.” 2017. Doctoral Dissertation, Indian Institute of Science. Accessed March 04, 2021. http://etd.iisc.ac.in/handle/2005/2720.

MLA Handbook (7^th Edition):

Pandey, Sunil Kumar. “Exploration And Assessment of HCCI Strategies for a Multi-Cylinder Heavy-Duty Diesel Engine.” 2017. Web. 04 Mar 2021.

Vancouver:

Pandey SK. Exploration And Assessment of HCCI Strategies for a Multi-Cylinder Heavy-Duty Diesel Engine. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2017. [cited 2021 Mar 04]. Available from: http://etd.iisc.ac.in/handle/2005/2720.

Council of Science Editors:

Pandey SK. Exploration And Assessment of HCCI Strategies for a Multi-Cylinder Heavy-Duty Diesel Engine. [Doctoral Dissertation]. Indian Institute of Science; 2017. Available from: http://etd.iisc.ac.in/handle/2005/2720

Indian Institute of Science

10. Garg, Manish. Studies On Fuel-Air Stratification And Combustion Modelling In A CNG-Fuelled Engine.

Degree: PhD, Faculty of Engineering, 2016, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/2593

► In-cylinder fuel-air mixing in a compressed natural gas (CNG)-fuelled, single-cylinder, spark-ignited engine is analysed using a transient three-dimensional computational fluid dynamic model built and run… (more)

▼ In-cylinder fuel-air mixing in a compressed natural gas (CNG)-fuelled, single-cylinder, spark-ignited engine is analysed using a transient three-dimensional computational fluid dynamic model built and run using STAR-CD, a commercial CFD software. This work is motivated by the need for strategies to achieve improved performance in engines utilizing gaseous fuels such as CNG. The transient in-cylinder fuel-air mixing is evaluated for a port gas injection fuelling system and compared with that of conventional gas carburetor system. In this work pure methane is used as gaseous fuel for all the computational studies. It is observed that compared to the premixed gas carburetor system, a substantial level of in-cylinder stratification can be achieved with the port gas injection system. The difference of more than 20% in mass fraction between the rich and lean zones in the combustion chamber is observed for the port gas injection system compared to less than 1% for the conventional premixed system. The phenomenon of stratification observed is very close to the “barrel stratification” mode. A detailed parametric study is undertaken to understand the effect of various injection parameters such as injection location, injection orientation, start of injection, duration of injection and rate of injection. Furthermore, the optimum injection timing is evaluated for various load-speed conditions of the engine. It is also observed that the level of stratification is highest at 50% engine load with a reduced level at 100% load. For low engine loads, the level of stratification is observed to be very low. To analyse the effect of stratification on engine performance, the in-cylinder combustion is modeled using the extended coherent flame model(ECFM). For simulating the ignition process, the arc and kernel tracking ignition model(AKTIM) is used. The combustion model is first validated with measured in-cylinder pressure data and other derived quantities such as heat release rate and mass burn fraction. It is observed that there is a good agreement between measured and simulated values. Subsequently, this model is use to simulate both premixed and stratified cases. It is observed that there is a marginal improvement in terms of overall engine efficiency when the stoichiometric premixed case is compared with the lean stratified condition. However, a major improvement in performance is observed when the lean stratified case is compared with lean premixed condition. The stratified case shows a faster heat release rate which could potentially translate to lower cycle-to-cycle variations in actual engine operation. Also, the stratified cases show as much as 20% lower in-cylinder NOx emissions when compared with the conventional premixed case at the same engine load and speed, underscoring the potential of in-cylinder stratification to achieve improved performance and lower NOx emissions. Advisors/Committee Members: Ravikrishna, R V (advisor).

Subjects/Keywords: Compressed Natural Gas-Fuelled Engines; Internal Combustion Engine; Combustion Modelling; Port Gas Injection; In-Cylinder Stratification; Computational Fluid Dynamics; Engine Combuation - Modelling; Fuel-Air Stratification; Combustion Models; Compressed Natural Gas (CNG); CNG-Fuelled Engine; Heat Engineering

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Garg, M. (2016). Studies On Fuel-Air Stratification And Combustion Modelling In A CNG-Fuelled Engine. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/2593

Chicago Manual of Style (16^th Edition):

Garg, Manish. “Studies On Fuel-Air Stratification And Combustion Modelling In A CNG-Fuelled Engine.” 2016. Doctoral Dissertation, Indian Institute of Science. Accessed March 04, 2021. http://etd.iisc.ac.in/handle/2005/2593.

MLA Handbook (7^th Edition):

Garg, Manish. “Studies On Fuel-Air Stratification And Combustion Modelling In A CNG-Fuelled Engine.” 2016. Web. 04 Mar 2021.

Vancouver:

Garg M. Studies On Fuel-Air Stratification And Combustion Modelling In A CNG-Fuelled Engine. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2016. [cited 2021 Mar 04]. Available from: http://etd.iisc.ac.in/handle/2005/2593.

Council of Science Editors:

Garg M. Studies On Fuel-Air Stratification And Combustion Modelling In A CNG-Fuelled Engine. [Doctoral Dissertation]. Indian Institute of Science; 2016. Available from: http://etd.iisc.ac.in/handle/2005/2593

Indian Institute of Science

11. Singhal, Atul. Single Cavity Trapped Vortex Combustor Dynamics : Experiments & Simulations.

Degree: PhD, Faculty of Engineering, 2011, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/1123

► Trapped Vortex Combustor (TVC) is a relatively new concept for potential use in gas turbine engines addressing ever increasing demands of high efficiency, low emissions,… (more)

▼ Trapped Vortex Combustor (TVC) is a relatively new concept for potential use in gas turbine engines addressing ever increasing demands of high efficiency, low emissions, low pressure drop, and improved pattern factor. This concept holds promise for future because of its inherent advantages over conventional swirl-stabilized combustors. The main difference between TVC and a conventional gas turbine combustor is in the way combustion is stabilized. In conventional combustors, flame is stabilized because of formation of toroidal flow pattern in the primary zone due to interaction between incoming swirling air and fuel flow. On the other hand, in TVC, there is a physical cavity in the wall of combustor with continuous injection of air and fuel leading to stable and sustained combustion. Past work related to TVC has focussed on use of two cavities in the combustor liner. In the present study, a single cavity combustor concept is evaluated through simulation and experiments for applications requiring compact combustors such as Unmanned Aerial Vehicles (UAVs) and cruise missiles. In the present work, numerical simulations were initially performed on a planar, rectangular single-cavity geometry to assess sensitivity of various parameters and to design a single-cavity TVC test rig. A water-cooled, modular, atmospheric pressure TVC test rig is designed and fabricated for reacting and non-reacting flow experiments. The unique features of this rig consist of a continuously variable length-to-depth ratio (L/D) of the cavity and optical access through quartz plates provided on three sides for visualization. Flame stabilization in the single cavity TVC was successfully achieved with methane as fuel, and the range of flow conditions for stable operation were identified. From these, a few cases were selected for detailed experimentation. Reacting flow experiments for the selected cases indicated that reducing L/D ratio and increasing cavity-air velocity favour stable combustion. The pressure drop across the single-cavity TVC is observed to be lower as compared to conventional combustors. Temperatures are measured at the exit using thermocouples and corrected for radiative losses. Species concentrations are measured at the exit using an exhaust gas analyzer. The combustion efficiency is observed to be around 98-99% and the pattern factor is observed to be in the range of 0.08 to 0.13. High-speed imaging made possible by the optical access indicates that the overall combustion is fairly steady, and there is no major vortex shedding downstream. This enabled steady-state simulations to be performed for the selected cases. Insight from simulations has highlighted the importance of air and fuel injection strategies in the cavity. From a mixing and combustion efficiency standpoint, it is desirable to have a cavity vortex that is anti-clockwise. However, the natural tendency for flow over a cavity is to form a vortex that is clockwise. The tendency to blow-out at higher inlet flow velocities is thought to be because of these two… Advisors/Committee Members: Ravikrishna, R V (advisor).

Subjects/Keywords: Combustion Engineering; Combustion Dynamics - Simulation; Trapped Vortex Combustor (TVC); Computational Fluid Dynamics; Gas Turbine Combustors; Cavity Flow Dynamics; Single Cavity; Gas Turbine; Combustion Efficiency; Gas Turbine Combustors; Heat Engineering

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Singhal, A. (2011). Single Cavity Trapped Vortex Combustor Dynamics : Experiments & Simulations. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/1123

Chicago Manual of Style (16^th Edition):

Singhal, Atul. “Single Cavity Trapped Vortex Combustor Dynamics : Experiments & Simulations.” 2011. Doctoral Dissertation, Indian Institute of Science. Accessed March 04, 2021. http://etd.iisc.ac.in/handle/2005/1123.

MLA Handbook (7^th Edition):

Singhal, Atul. “Single Cavity Trapped Vortex Combustor Dynamics : Experiments & Simulations.” 2011. Web. 04 Mar 2021.

Vancouver:

Singhal A. Single Cavity Trapped Vortex Combustor Dynamics : Experiments & Simulations. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2011. [cited 2021 Mar 04]. Available from: http://etd.iisc.ac.in/handle/2005/1123.

Council of Science Editors:

Singhal A. Single Cavity Trapped Vortex Combustor Dynamics : Experiments & Simulations. [Doctoral Dissertation]. Indian Institute of Science; 2011. Available from: http://etd.iisc.ac.in/handle/2005/1123

Indian Institute of Science

12. Sahu, Amrit Bikram. Quantitative Laser-Based Diagnostics and Modelling of Syngas-Air Counterflow Diffusion Flames.

Degree: PhD, Faculty of Engineering, 2018, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/3654

► Syngas, a gaseous mixture of H2, CO and diluents such as N2, CO2, is a clean fuel generated via gasification of coal or biomass. Syngas… (more)

▼ Syngas, a gaseous mixture of H2, CO and diluents such as N2, CO2, is a clean fuel generated via gasification of coal or biomass. Syngas produced via gasification typically has low calorific values due to very high dilution levels (~60% by volume). It has been recognized as an attractive energy source for stationary power generation applications. The present work focuses on experimental and numerical investigation of syngas-air counterflow diffusion flames with varying composition of syngas. Laser-based diagnostic techniques such as Particle Imaging Velocimetry, Rayleigh thermometry and Laser-induced fluorescence have been used to obtain non-intrusive measurements of local extinction strain rates, temperature, quantitative OH and NO concentrations, respectively, for three different compositions of syngas. Complementing the experiments, numerical simulations of the counterflow diffusion flame have been performed to assess the performance of five H2/CO chemical kinetic mechanisms from the literature. The first part of the work involved determination of local extinction strain rates for six H2 /CO mixtures, with H2:CO ratio varying from 1:4 to 1:1. The extinction strain rates were observed to increase from 600 sec-1 to 2400 sec-1 with increasing H2:CO ratio owing to higher diffusivity and reactivity of the H2 molecule. Numerical simulations showed few mechanisms predicting extinction conditions within 5% of the measurements for low H2:CO ratios, however, deviations of 25% were observed for higher H2 :CO ratios. Sensitivity analyses revealed that the chain branching reactions, H+O2 <=>O+OH, O+H2 <=>H+OH and the third body reaction H+O2 +M<=>HO2 +M are the key reactions affecting extinction limits for higher H2:CO mixtures. The second phase of work involved quantitative measurement of OH species concentration in the syngas-air diffusion flames at strain rates varying from 35 sec-1 to 1180 sec-1. Non-intrusive temperature measurements using Rayleigh thermometry were made in order to provide the temperature profile necessary for full quantification of the species concentrations. The [OH] is observed to show a non-monotonous trend with increasing strain rates which is attributed to the competition between the effect of increased concentrations of H2 and O2 in the reaction zone and declining flame temperatures on the overall reaction rate. Although the kinetic mechanisms successfully captured this trend, significant deviations were observed in predictions and measurements in flames with H2:CO ratios of 1:1 and 4:1, at strain rates greater than 800 sec-1 . The key reactions affecting [OH] under these conditions were found to be the same reactions identified earlier during extinction studies, thus implying a need for the refinement of their reaction-rate parameters. Significant disagreements were observed in the predictions made using the chemical kinetic mechanisms from the literature in flames with high H2 content and high strain rate. The final phase of work focused on measurement of nitric oxide (NO) species concentrations… Advisors/Committee Members: Ravikrishna, R V (advisor).

Subjects/Keywords: Syngas; Diffusion Flame; Coal Gasification; Counterflow Diffusion Flames; Counterflow Syngas Flames; OH PLIF; Rayleigh Thermometry; Mechanical Engineering

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Sahu, A. B. (2018). Quantitative Laser-Based Diagnostics and Modelling of Syngas-Air Counterflow Diffusion Flames. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/3654

Chicago Manual of Style (16^th Edition):

Sahu, Amrit Bikram. “Quantitative Laser-Based Diagnostics and Modelling of Syngas-Air Counterflow Diffusion Flames.” 2018. Doctoral Dissertation, Indian Institute of Science. Accessed March 04, 2021. http://etd.iisc.ac.in/handle/2005/3654.

MLA Handbook (7^th Edition):

Sahu, Amrit Bikram. “Quantitative Laser-Based Diagnostics and Modelling of Syngas-Air Counterflow Diffusion Flames.” 2018. Web. 04 Mar 2021.

Vancouver:

Sahu AB. Quantitative Laser-Based Diagnostics and Modelling of Syngas-Air Counterflow Diffusion Flames. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2018. [cited 2021 Mar 04]. Available from: http://etd.iisc.ac.in/handle/2005/3654.

Council of Science Editors:

Sahu AB. Quantitative Laser-Based Diagnostics and Modelling of Syngas-Air Counterflow Diffusion Flames. [Doctoral Dissertation]. Indian Institute of Science; 2018. Available from: http://etd.iisc.ac.in/handle/2005/3654

Indian Institute of Science

13. Agarwal, Krishna Kant. Experimental And Numerical Studies On Flame Stability And Optimization Of A Compact Trapped Vortex Combustor.

Degree: PhD, Faculty of Engineering, 2013, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/1956

► A new Trapped Vortex Combustor (TVC) concept has been studied for applications such as those in Unmanned Aerial Vehicles (UAVs) as it offers potential for… (more)

▼ A new Trapped Vortex Combustor (TVC) concept has been studied for applications such as those in Unmanned Aerial Vehicles (UAVs) as it offers potential for superior flame stability and low pressure loss. Flame stability is ensured by a strong vortex in a physical cavity attached to the combustor wall, and low pressure loss is due to the absence of swirl. Earlier studies on a compact combustor concept showed that there are issues with ensuring stable combustion over a range of operating conditions. The present work focuses on experimental studies and numerical simulations to study the stability issues and performance optimization in this compact single-cavity TVC configuration. For performing numerical simulations, an accurate and yet computationally affordable Modified Eddy Dissipation Concept combustion model is built upon the KIVA-3V platform to account for turbulence-chemistry interactions. Detailed validation with a turbulent non-premixed CH4/H2/N2 flame from literature showed that the model is sufficiently accurate and the effect of various simulation strategies is assessed. Transient flame simulation capabilities are assessed by comparison with experimental data from an acoustically excited oscillatory H2-air diffusion flame reported in literature. Subsequent to successful validation of the model, studies on basic TVC flow oscillations are performed. Frequencies of flow oscillations are found to be independent of flow velocities and cavity length, but dependent on the cavity depth. Cavity injection and combustion individually affect the magnitude of flow oscillations but do not significantly alter the resonant frequencies. Reacting flow experiments and flow visualization studies in an existing experimental TVC rig with optical access and variable cavity L/D ratio show that TVC flame stability depends strongly on the cavity air velocity. A detailed set of numerical simulations also confirms this and helps to identify three basic modes of TVC flame stabilization. A clockwise cavity vortex stabilized flame is formed at low cavity air velocities relative to the mainstream, while a strong anticlockwise cavity vortex is formed at high cavity air velocities and low L/Ds. At intermediate conditions, the cavity vortex structure is found to be in a transition state which leads to large scale flame instabilities and flame blow-out. For solving the flame instability problem, a novel strategy of incorporating a flow guide vane is proposed to establish the advantageous anticlockwise vortex without the use of cavity air. Experimental results with the modified configuration are quite encouraging for TVC flame stability at laboratory conditions, while numerical results show good stability even at extreme operating conditions. Further design optimization studies are performed in a multi-parameter space using detailed simulations. From the results, a strategy of using inclined struts in the main flow path along with the ﬂow guide vane seems most promising. This configuration is tested experimentally and results pertaining to… Advisors/Committee Members: Ravikrishna, R V (advisor).

Subjects/Keywords: Unmanned Aerial Vehicles (UAVs); Trapped Vortex Combustor (TVC); Flame Stability; Heat Engineering

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Agarwal, K. K. (2013). Experimental And Numerical Studies On Flame Stability And Optimization Of A Compact Trapped Vortex Combustor. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/1956

Chicago Manual of Style (16^th Edition):

Agarwal, Krishna Kant. “Experimental And Numerical Studies On Flame Stability And Optimization Of A Compact Trapped Vortex Combustor.” 2013. Doctoral Dissertation, Indian Institute of Science. Accessed March 04, 2021. http://etd.iisc.ac.in/handle/2005/1956.

MLA Handbook (7^th Edition):

Agarwal, Krishna Kant. “Experimental And Numerical Studies On Flame Stability And Optimization Of A Compact Trapped Vortex Combustor.” 2013. Web. 04 Mar 2021.

Vancouver:

Agarwal KK. Experimental And Numerical Studies On Flame Stability And Optimization Of A Compact Trapped Vortex Combustor. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2013. [cited 2021 Mar 04]. Available from: http://etd.iisc.ac.in/handle/2005/1956.

Council of Science Editors:

Agarwal KK. Experimental And Numerical Studies On Flame Stability And Optimization Of A Compact Trapped Vortex Combustor. [Doctoral Dissertation]. Indian Institute of Science; 2013. Available from: http://etd.iisc.ac.in/handle/2005/1956

Indian Institute of Science

14. Kapadia, Bhavin Kanaiyalal. Development Of A Single Cylinder SI Engine For 100% Biogas Operation.

Degree: MSc Engg, Faculty Of Engineering, 2007, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/283

► This work concerns a systematic study of IC engine operation with 100% biogas as fuel (as opposed to the dual-fuel mode) with particular emphasis on… (more)

▼ This work concerns a systematic study of IC engine operation with 100% biogas as fuel (as opposed to the dual-fuel mode) with particular emphasis on operational issues and the quest for high efficiency strategies. As a first step, a commercially available 1.2 kW genset engine is modified for biogas operation. The conventional premixing of air and biogas is compared with a new manifold injection strategy. The effect of biogas composition on engine performance is also studied. Results from the genset engine study indicate a very low overall efficiency of the system. This is mainly due to the very low compression ratio (4.5) of the engine. To gain further insight into factors that contribute to this low efficiency, thermodynamic engine simulations are conducted. Reasonable agreement with experiments is obtained after incorporating estimated combustion durations. Subsequently, the model is used as a tool to predict effect of different parameters such as compression ratio, spark timing and combustion durations on engine performance and efficiency. Simulations show that significant improvement in performance can be obtained at high compression ratios. As a step towards developing a more efficient system and based on insight obtained from simulations, a high compression ratio (9.2) engine is selected. This engine is coupled to a 3 kW alternator and operated on 100% biogas. Both strategies, i.e., premixing and manifold injection are implemented. The results show very high overall (chemical to electrical) efficiencies with a maximum value of 22% at 1.4 kW with the manifold injection strategy. The new manifold injection strategy proposed here is found to be clearly superior to the conventional premixing method. The main reasons are the higher volumetric efficiency (25% higher than that for the premixing mode of supply) and overall lean operation of the engine across the entire load range. Predictions show excellent agreement with measurements, enabling the model to be used as a tool for further study. Simulations suggest that a higher compression ratio (up to 13) and appropriate spark advance can lead to higher engine power output and efficiency. Advisors/Committee Members: Ravikrishna, R V (advisor).

Subjects/Keywords: Internal Combustion Engine; Biogas; Genset Engine; High Compression Ratio Engine; Spark Ignition Engines; Biogas Generation; Spark-Ignition Engine; Gaseous Fuels; Gasoline; IC Engine; SI Engine; Engines - Performance; Spark-Ignited Engine; Heat Engineering

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Kapadia, B. K. (2007). Development Of A Single Cylinder SI Engine For 100% Biogas Operation. (Masters Thesis). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/283

Chicago Manual of Style (16^th Edition):

Kapadia, Bhavin Kanaiyalal. “Development Of A Single Cylinder SI Engine For 100% Biogas Operation.” 2007. Masters Thesis, Indian Institute of Science. Accessed March 04, 2021. http://etd.iisc.ac.in/handle/2005/283.

MLA Handbook (7^th Edition):

Kapadia, Bhavin Kanaiyalal. “Development Of A Single Cylinder SI Engine For 100% Biogas Operation.” 2007. Web. 04 Mar 2021.

Vancouver:

Kapadia BK. Development Of A Single Cylinder SI Engine For 100% Biogas Operation. [Internet] [Masters thesis]. Indian Institute of Science; 2007. [cited 2021 Mar 04]. Available from: http://etd.iisc.ac.in/handle/2005/283.

Council of Science Editors:

Kapadia BK. Development Of A Single Cylinder SI Engine For 100% Biogas Operation. [Masters Thesis]. Indian Institute of Science; 2007. Available from: http://etd.iisc.ac.in/handle/2005/283

Open Access Theses and Dissertations