Advanced search options

Advanced Search Options 🞨

Browse by author name (“Author name starts with…”).

Find ETDs with:

in
/  
in
/  
in
/  
in

Written in Published in Earliest date Latest date

Sorted by

Results per page:

Sorted by: relevance · author · university · dateNew search

Dates: Last 2 Years

You searched for subject:(release speed). Showing records 1 – 3 of 3 total matches.

Search Limiters

Last 2 Years | English Only

No search limiters apply to these results.

▼ Search Limiters


Universitat Politècnica de València

1. Valero Marco, Jorge. Analysis of the potential of SI lean combustion and CAI combustion in a two-stroke spark-assisted gasoline engine .

Degree: 2020, Universitat Politècnica de València

[EN] Internal combustion engines are in a situation in which they must be cleaner and more efficient than they have ever been. This change is motivated by the global and continuous evolution of the emissions regulations linked to their commercialization, which try to establish the path to protect the human health, and move towards more sustainable energetic models. Framed in this context, the research work developed in this PhD thesis has focused on the way to continue improving the spark ignition engines. To this end, a prototype two-stroke engine has been used, with the idea of studying the Spark Ignited combustion in lean conditions ('lean SI') and the Controlled Auto-Ignition combustion 'CAI'). In this way, the traditional 'SI' operation in stoichiometric conditions of this type of engines is replaced, looking for an improvement in fuel efficiency, and a reduction, at the same time, of the pollutant emissions. This work has been approached mainly from an experimental point of view. Firstly, different works have been performed on the engine: operation of the different combustion modes, definition of the operating strategies, and compilation of experimental data coming from the engine operation in the different regions of the engine map. And, secondly, all this data has been analyzed and studied in detail to define the strengths and weaknesses of each combustion mode applied to the different engine operating conditions. The combination of these two works has led to obtain a large amount of data about the achievable efficiencies and the emissions values obtained in each combustion mode. And, in addition, the influence on the combustion of the burned gases recirculation in the engine ('EGR'), has also been studied as a strategy to reduce emissions, and control the combustion at high loads in both combustion modes. Regarding the analytical part of the work, several problems have been detected. Firstly, the high combustion variability in this engine, and secondly, the coupling of two completely different combustion modes. These issues have generated the need to analyze the data obtained in a more detailed way, in order to get more information about the combustion process. To solve these two aspects, first, a different point of view has been raised when dealing with the combustion diagnosis, the cycle to cycle analysis, and secondly, a combustion analysis methodology has been proposed in order to allow the combustion analysis from a more detailed point of view. In this way the combustion development is studied, and thus, the differentiation between the different combustion events that take place in the engine can be studied. All this work has been useful to define the strategies to operate the whole engine map by combining the 'lean SI' and 'CAI' combustion modes. This solution, compared to the current Euro VI engines, has presented higher efficiency values complying with the established emissions limits, showing in this way, the high potential of these combustion modes applied to 'SI' engines, as well as a real… Advisors/Committee Members: López Sánchez, José Javier (advisor).

Subjects/Keywords: Two-stoke engine; engines developement; CAI (Controlled Auto-Ignition); SI (Spark Ignition); Lean Combustion; advanced combustion modes; combustion analysis; instantaneous cycles; cycle to cycle variation; air-assisted injection; HRL (Heat Release Law); combustion speed.

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

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

APA (6th Edition):

Valero Marco, J. (2020). Analysis of the potential of SI lean combustion and CAI combustion in a two-stroke spark-assisted gasoline engine . (Doctoral Dissertation). Universitat Politècnica de València. Retrieved from http://hdl.handle.net/10251/138556

Chicago Manual of Style (16th Edition):

Valero Marco, Jorge. “Analysis of the potential of SI lean combustion and CAI combustion in a two-stroke spark-assisted gasoline engine .” 2020. Doctoral Dissertation, Universitat Politècnica de València. Accessed January 22, 2021. http://hdl.handle.net/10251/138556.

MLA Handbook (7th Edition):

Valero Marco, Jorge. “Analysis of the potential of SI lean combustion and CAI combustion in a two-stroke spark-assisted gasoline engine .” 2020. Web. 22 Jan 2021.

Vancouver:

Valero Marco J. Analysis of the potential of SI lean combustion and CAI combustion in a two-stroke spark-assisted gasoline engine . [Internet] [Doctoral dissertation]. Universitat Politècnica de València; 2020. [cited 2021 Jan 22]. Available from: http://hdl.handle.net/10251/138556.

Council of Science Editors:

Valero Marco J. Analysis of the potential of SI lean combustion and CAI combustion in a two-stroke spark-assisted gasoline engine . [Doctoral Dissertation]. Universitat Politècnica de València; 2020. Available from: http://hdl.handle.net/10251/138556


University of Illinois – Urbana-Champaign

2. Motily, Austen. Evaluation of hot surface ignition device performance with high-pressure kerosene fuel sprays.

Degree: MS, Mechanical Engineering, 2020, University of Illinois – Urbana-Champaign

Among the range of commercially feasible propulsion systems, compression ignition (CI) engines present many advantages for light-duty vehicle operation. In particular, CI engines remain an optimal choice for unmanned aerial vehicles (UAVs) designed to operate at moderate flight speeds. However, one of the primary limitations of CI engines is that they require well-characterized, highly-reactive diesel fuel to operate properly. As the United States Department of Defense implements the single fuel concept and with global efforts to develop alternatively derived fuels, it is paramount that modern CI engines have the capability to perform with a diverse variety of fuel types. At its core, this challenge can be framed as an ignition problem, where low reactivity fuels and extreme operating conditions result in long ignition delays, engine misfires, and power loss. It is for this reason that novel ignition devices be developed to support reliable CI engine operation. Hot surface energy addition devices are a promising technology to improve ignition behavior, but the mechanisms by which the heating element supports the ignition process are not well understood. This study evaluates the performance and limitations of commercial off-the-shelf (COTS) heating elements in functioning as continuous-use ignition devices for kerosene-fueled CI engines. Furthermore, it examines the interaction between a single high-pressure fuel spray with a hot surface device in order to identify the most important parameters for optimizing ignition behavior. Results of these experiments demonstrate that existing heating elements can accelerate the ignition process for fuels with a wide range of reactivities, assuming a sufficient surface temperature can be achieved. Reaching these temperatures in an engine environment and maintaining these temperatures for long periods of operation, with acceptable heating element durability, will be the primary challenges in developing next-generation ignition systems. Advisors/Committee Members: Lee, Tonghun (advisor).

Subjects/Keywords: Hot surface ignition; Rapid compression machine; Fuel spray ignition; Energy assisted ignition; High-pressure fuel spray; Ignition modes; Ignition device; Fuel spray heat release; Low-reactivity fuels; High-speed chemiluminescence imaging

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

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

APA (6th Edition):

Motily, A. (2020). Evaluation of hot surface ignition device performance with high-pressure kerosene fuel sprays. (Thesis). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/107927

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Motily, Austen. “Evaluation of hot surface ignition device performance with high-pressure kerosene fuel sprays.” 2020. Thesis, University of Illinois – Urbana-Champaign. Accessed January 22, 2021. http://hdl.handle.net/2142/107927.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Motily, Austen. “Evaluation of hot surface ignition device performance with high-pressure kerosene fuel sprays.” 2020. Web. 22 Jan 2021.

Vancouver:

Motily A. Evaluation of hot surface ignition device performance with high-pressure kerosene fuel sprays. [Internet] [Thesis]. University of Illinois – Urbana-Champaign; 2020. [cited 2021 Jan 22]. Available from: http://hdl.handle.net/2142/107927.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Motily A. Evaluation of hot surface ignition device performance with high-pressure kerosene fuel sprays. [Thesis]. University of Illinois – Urbana-Champaign; 2020. Available from: http://hdl.handle.net/2142/107927

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


Universitat Politècnica de València

3. Pagano, Vincenzo. Analysis of a stratified pre-chamber spark ignition system under lean mixture conditions .

Degree: 2020, Universitat Politècnica de València

[EN] In the current work, the characterization of the combustion process inside a stratified pre-chamber spark ignition (PCSI) system is performed. An extensive bibliographical review about the pre-chamber systems developed from the second half of the 20th century until modern times is presented. The review shows that the latest generation systems have the potential to accomplish the emissions limits while providing high performance and low fuel consumption. Nevertheless, many efforts of the scientific community are still needed to allow the large-scale application of the technology. Indeed, based on the outstanding challenges observed, the investigation plan is developed including both experimental and numerical parts. All experiments were performed by means of the rapid compressionexpansion machine (RCEM) in the CMT-Motores Térmicos laboratory. The original cylinder head layout was modified to allow the housing of the prechamber itself, fuel injectors, spark plug, pressure transducers in both chamber, and a thermocouple. The test methodology involved the acquisition of the pressure evolution in both main chamber and pre-chamber, the piston position (used to compute the instantaneous cylinder volume), the duration of the auxiliary injection, and the spark ignition point. These are used as input for the zero-dimensional thermodynamic model which simulates the fundamental parameters aims to characterize the PCSI system working cycle. Therefore, a deeper knowledge of the mass interchanged process, induced turbulence field, heat release rate, combustion speed, and flame regime is generated. Subsequently, to calibrate the zero-dimensional model coefficients under motoring conditions, several 3D CFD simulations were carried out by means of Converge software. Hence, the results of the simulations in terms of interchanged mass and pre-chamber turbulent kinetic energy have been used to calibrate the nozzle discharge coefficient and the turbulence sub-model coefficients for all the pre-chamber geometries. Furthermore, the 3D CFD simulations outputs are analysed to fully understand the flow field structure and the local effect induced by the different nozzles at the spark activation time. The turbulent kinetic energy in terms of intensity and orientation is investigated over several relevant pre-chamber sections. The results reveal a clear relationship between the turbulence developed within the pre-chamber and the orifices structure. Straight orifices or perpendicular jets impact, promote more intense local turbulence due to direct collision while tilted orifices guarantee more homogeneity due to the swirling motion. Additionally, increase the orifice numbers shows benefits on the fluid dynamic homogeneity. Thus, preceding the experimental campaign several fundamental aspects of the system are evaluated. The cycle-to-cycle dispersion is explored by means of the statistical assessment showing low pressure peak deviation. The auxiliary injection pressure and timing are optimized for avoiding wall wetting phenomena while… Advisors/Committee Members: Morena Borja, Joaquín de la (advisor).

Subjects/Keywords: Pre-chamber Spark Ignition System; Torch Jet Ignition; Flame Propagation; Nozzle Geometry; Combustion Speed; Heat Release Rate; Stratified System; Natural Chemiluminescence; Combustion Visualization; Rapid Compression-Expansion Machine; Combustion Efficiency; Turbulent Kinetic Energy; CFD Simulations; 0D Thermodynamic Model

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

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

APA (6th Edition):

Pagano, V. (2020). Analysis of a stratified pre-chamber spark ignition system under lean mixture conditions . (Doctoral Dissertation). Universitat Politècnica de València. Retrieved from http://hdl.handle.net/10251/152486

Chicago Manual of Style (16th Edition):

Pagano, Vincenzo. “Analysis of a stratified pre-chamber spark ignition system under lean mixture conditions .” 2020. Doctoral Dissertation, Universitat Politècnica de València. Accessed January 22, 2021. http://hdl.handle.net/10251/152486.

MLA Handbook (7th Edition):

Pagano, Vincenzo. “Analysis of a stratified pre-chamber spark ignition system under lean mixture conditions .” 2020. Web. 22 Jan 2021.

Vancouver:

Pagano V. Analysis of a stratified pre-chamber spark ignition system under lean mixture conditions . [Internet] [Doctoral dissertation]. Universitat Politècnica de València; 2020. [cited 2021 Jan 22]. Available from: http://hdl.handle.net/10251/152486.

Council of Science Editors:

Pagano V. Analysis of a stratified pre-chamber spark ignition system under lean mixture conditions . [Doctoral Dissertation]. Universitat Politècnica de València; 2020. Available from: http://hdl.handle.net/10251/152486

.