+publisher:"University of Michigan" +contributor:("Martz, Jason Brian")

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University of Michigan

1. Triantopoulos, Vasileios. Experimental and Computational Investigation of Spark Assisted Compression Ignition Combustion Under Boosted, Ultra EGR-Dilute Conditions.

Degree: PhD, Mechanical Engineering, 2018, University of Michigan

URL: http://hdl.handle.net/2027.42/147508

► Low temperature combustion (LTC) engines that employ high levels of dilution have received increased research interest due to the demonstrated thermal efficiency improvements compared to… (more)

▼ Low temperature combustion (LTC) engines that employ high levels of dilution have received increased research interest due to the demonstrated thermal efficiency improvements compared to the conventional Spark-Ignited (SI) engines. However, control of combustion phasing and heat release rate still remains a challenge, which limits the operating range as well as the transient operation of LTC engines. The work presented in this dissertation uses experimental and computational methods to investigate Spark Assisted Compression Ignition (SACI) combustion under boosted, stoichiometric conditions with high levels of exhaust gas recirculation in a negative valve overlap engine. Highly controlled experimental studies were performed to understand the impact of intake boosting and fuel-to-charge equivalence ratio (φ') on SACI burn rates, while maintaining constant combustion phasing near the optimal timing for work extraction. Previously unexplored conditions were targeted at intake pressures ranging from 80 kPa to 150 kPa and φ' ranging from 0.45 to 0.75, where LTC engines promise high thermodynamic efficiencies. The use of intake boosting for load expansion and dilution extension achieved up to 10% gross thermal efficiency improvement, respectively, mainly due to reduced relative heat transfer losses and better mixture thermodynamic properties. For a given spark advance, higher pressure and/or higher φ' mixtures necessitated lower unburned gas temperatures (TU) to match autoignition timing. While the overall effect of intake boost was minor on the initial flame burn rates, end-gas autoignition rates were found to approximately scale with intake pressure. Higher φ' mixtures exhibited faster initial flame burn rates but also led to a significant increase in end-gas autoignition rates. As a result, the high load limits shifted to lower φ' at higher intake pressures, creating a larger gap between the SI and SACI operating limits. Reducing the mass fraction unburned at the onset of autoignition by advancing the spark timing and lowering TU was, to some extent, effective at alleviating the excessive peak pressure rise rates. Under relatively high φ' conditions, cyclic heat release analysis results showed that the variability in autoignition timing is determined early in the cycle before any measurable pressure-based heat release. Combustion phasing retard was shown to be very effective at limiting the maximum pressure rise rates until the stability limit, primarily due to slower end-gas autoignition rates. CFD modeling results showed good trendwise agreement with the experimental results, once autoignition timing and mass fraction burned at the onset of autoignition were matched. The pre-ignition reactivity stratification of the mixture at higher intake pressures was shown to be narrower, due to both lower thermal and compositional stratification, which explained the increase in end-gas burn rates observed experimentally. The boost pressure effect on SACI end-gas burn rates using intake manifold heating was trendwise similar… Advisors/Committee Members: Boehman, Andre L (committee member), Gamba, Mirko (committee member), Assanis, Dionissios N (committee member), Bohac, Stani V (committee member), Borgnakke, Claus (committee member), Martz, Jason Brian (committee member).

Subjects/Keywords: engines; thermodynamics; energy; efficiency; automotive; power; Mechanical Engineering; Engineering

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APA (6^th Edition):

Triantopoulos, V. (2018). Experimental and Computational Investigation of Spark Assisted Compression Ignition Combustion Under Boosted, Ultra EGR-Dilute Conditions. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/147508

Chicago Manual of Style (16^th Edition):

Triantopoulos, Vasileios. “Experimental and Computational Investigation of Spark Assisted Compression Ignition Combustion Under Boosted, Ultra EGR-Dilute Conditions.” 2018. Doctoral Dissertation, University of Michigan. Accessed April 14, 2021. http://hdl.handle.net/2027.42/147508.

MLA Handbook (7^th Edition):

Triantopoulos, Vasileios. “Experimental and Computational Investigation of Spark Assisted Compression Ignition Combustion Under Boosted, Ultra EGR-Dilute Conditions.” 2018. Web. 14 Apr 2021.

Vancouver:

Triantopoulos V. Experimental and Computational Investigation of Spark Assisted Compression Ignition Combustion Under Boosted, Ultra EGR-Dilute Conditions. [Internet] [Doctoral dissertation]. University of Michigan; 2018. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/2027.42/147508.

Council of Science Editors:

Triantopoulos V. Experimental and Computational Investigation of Spark Assisted Compression Ignition Combustion Under Boosted, Ultra EGR-Dilute Conditions. [Doctoral Dissertation]. University of Michigan; 2018. Available from: http://hdl.handle.net/2027.42/147508

University of Michigan

2. Shingne, Prasad Sunand. Thermodynamic Modeling of HCCI Combustion with Recompression and Direct Injection.

Degree: PhD, Mechanical Engineering, 2015, University of Michigan

URL: http://hdl.handle.net/2027.42/113499

► Homogeneous Charge Compression Ignition (HCCI) engines have the potential to reduce pollutant emissions while achieving diesel-like thermal efficiencies. The absence of direct control over the… (more)

▼ Homogeneous Charge Compression Ignition (HCCI) engines have the potential to reduce pollutant emissions while achieving diesel-like thermal efficiencies. The absence of direct control over the start and rate of auto-ignition and a narrow load range makes implementation of HCCI engines into production vehicles a challenging affair. Effective HCCI combustion control can be achieved by manipulating the amount of residual gases trapped from the previous cycle by means of variable valve actuation. In turn, the temperature at intake valve closing and hence auto-ignition phasing can be controlled. Intake charge boosting can be used to increase HCCI fueling rates and loads, while other technologies such as direct injection provide means for achieving cycle to cycle phasing control. Thermodynamic zero-dimensional (0D) models are a computationally inexpensive tool for defining systems and strategies suitable for the implementation of new HCCI engine technologies. These models need to account for the thermal and compositional stratification in HCCI that control combustion rates. However these models are confined to a narrow range of engine operation given that the fundamental factors governing the combustion process are currently not well understood. CFD has therefore been used to understand the effect of operating conditions and input variables on pre-ignition charge stratification and combustion, allowing the development and use of a more accurate ignition model, which is proposed and validated here. A new empirical burn profile model is fit with mass fraction burned profiles from a large HCCI engine data set. The combined ignition model and burn correlation are then exercised and are shown capable of capturing the trends of a diverse range of transient HCCI experiments. However, the small cycle to cycle variations in combustion phasing are not captured by the model, possibly due to recompression heat release effects associated with variable valve actuation. Multi-cycle CFD simulations are therefore performed to gain physical insight into recompression heat release phenomena and the effect of these phenomena on the next cycle. Based on the understanding derived from this CFD work, a simple model of recompression heat release has been implemented in the 0D HCCI modeling framework. Advisors/Committee Members: Martz, Jason Brian (committee member), Assanis, Dionissios N. (committee member), Borgnakke, Claus (committee member), Driscoll, James F. (committee member), Boehman, Andre L. (committee member), Bohac, Stani V. (committee member).

Subjects/Keywords: HCCI; Combustion; Thermodynamics; 0D Modeling; Stratification; NVO heat release; Mechanical Engineering; Engineering

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APA (6^th Edition):

Shingne, P. S. (2015). Thermodynamic Modeling of HCCI Combustion with Recompression and Direct Injection. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/113499

Chicago Manual of Style (16^th Edition):

Shingne, Prasad Sunand. “Thermodynamic Modeling of HCCI Combustion with Recompression and Direct Injection.” 2015. Doctoral Dissertation, University of Michigan. Accessed April 14, 2021. http://hdl.handle.net/2027.42/113499.

MLA Handbook (7^th Edition):

Shingne, Prasad Sunand. “Thermodynamic Modeling of HCCI Combustion with Recompression and Direct Injection.” 2015. Web. 14 Apr 2021.

Vancouver:

Shingne PS. Thermodynamic Modeling of HCCI Combustion with Recompression and Direct Injection. [Internet] [Doctoral dissertation]. University of Michigan; 2015. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/2027.42/113499.

Council of Science Editors:

Shingne PS. Thermodynamic Modeling of HCCI Combustion with Recompression and Direct Injection. [Doctoral Dissertation]. University of Michigan; 2015. Available from: http://hdl.handle.net/2027.42/113499

University of Michigan

3. Ortiz-Soto, Elliott Alexander. Combustion Modeling of Spark Assisted Compression Ignition for Experimental Analysis and Engine System Simulations.

Degree: PhD, Mechanical Engineering, 2013, University of Michigan

URL: http://hdl.handle.net/2027.42/102314

► Advanced combustion strategies provide significant efficiency and emissions benefits compared to conventional spark ignited (SI) combustion, but challenges related to combustion control and load limits… (more)

▼ Advanced combustion strategies provide significant efficiency and emissions benefits compared to conventional spark ignited (SI) combustion, but challenges related to combustion control and load limits have made these technologies difficult to implement in practical systems. Until now, low cost reduced order models necessary for large parametric and multi-cycle studies capable of accurately capturing the full range of combustion modes from homogeneous charge compression ignition (HCCI) and spark-assisted compression ignition (SACI) to SI have not been available. This important computational gap for advanced combustion engine research was the primary motivation for this doctoral work. The outcomes of this study include powerful new tools to evaluate advanced combustion strategies as well as novel methods to incorporate important advanced combustion characteristics into reduced order models. A reduced order thermodynamic model of advanced SACI combustion was first proposed. The model was used with available experimental data and previous high fidelity simulation results to develop a new empirical auto-ignition burn rate model that captures the effects of ignition timing, composition, temperature, pressure, engine speed, stratification and flame propagation. A complete engine model was then developed and incorporated into the commercial simulation software GT-Power. The model included chemical kinetics for low temperature heat release and auto-ignition detection and the empirical burn rate model for post-ignition heat release, as well as a new flame propagation model with improved physical groundings. The calibrated engine model showed good agreement with experimental trends of HCCI, SACI and SI combustion modes. The engine model was then used to assess practical strategies for accessing the advanced combustion regime and improving engine efficiency. The results showed HCCI and SACI provide a pathway for significant efficiency benefits compared to throttled SI, with efficiency improvements between 15-25% across a range of loads from 1-7 bar BMEP. Further efficiency gains appear possible beyond the experimentally observed SACI limit. As a further exercise, the load extension potential of boosted SACI combustion was conceptually investigated using a simple thermodynamic framework incorporating the empirical burn rate model and practical operating constraints. The results indicate boosted SACI can nearly double the maximum engine load compared to naturally aspirated operation. Advisors/Committee Members: Wooldridge, Margaret S. (committee member), Assanis, Dionissios N. (committee member), Fidkowski, Krzysztof J. (committee member), Martz, Jason Brian (committee member), Lavoie, George A. (committee member), Babajimopoulos, Aristotelis (committee member), Borgnakke, Claus (committee member).

Subjects/Keywords: Spark Assisted Compression Ignition, Saci; Homogeneous Charge Compression Ignition, Hcci, Spark Ignition, Si, Knock; Advanced Combustion Engines; Combustion Modeling; Engine Simulation; Efficiency, Fuel Economy, Load Extension, Load Expansion; Mechanical Engineering; Engineering

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

APA (6^th Edition):

Ortiz-Soto, E. A. (2013). Combustion Modeling of Spark Assisted Compression Ignition for Experimental Analysis and Engine System Simulations. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/102314

Chicago Manual of Style (16^th Edition):

Ortiz-Soto, Elliott Alexander. “Combustion Modeling of Spark Assisted Compression Ignition for Experimental Analysis and Engine System Simulations.” 2013. Doctoral Dissertation, University of Michigan. Accessed April 14, 2021. http://hdl.handle.net/2027.42/102314.

MLA Handbook (7^th Edition):

Ortiz-Soto, Elliott Alexander. “Combustion Modeling of Spark Assisted Compression Ignition for Experimental Analysis and Engine System Simulations.” 2013. Web. 14 Apr 2021.

Vancouver:

Ortiz-Soto EA. Combustion Modeling of Spark Assisted Compression Ignition for Experimental Analysis and Engine System Simulations. [Internet] [Doctoral dissertation]. University of Michigan; 2013. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/2027.42/102314.

Council of Science Editors:

Ortiz-Soto EA. Combustion Modeling of Spark Assisted Compression Ignition for Experimental Analysis and Engine System Simulations. [Doctoral Dissertation]. University of Michigan; 2013. Available from: http://hdl.handle.net/2027.42/102314

4. Olesky, Laura Katherine. An Experimental Investigation of the Burn Rates of Naturally Aspirated Spark Assisted Compression Ignition Combustion in a Single Cylinder Engine with Negative Valve Overlap.

Degree: PhD, Mechanical Engineering, 2013, University of Michigan

URL: http://hdl.handle.net/2027.42/99979

► The implementation of homogeneous charge compression ignition (HCCI) in an engine remains a challenge due to the limited operating range and lack of a direct… (more)

▼ The implementation of homogeneous charge compression ignition (HCCI) in an engine remains a challenge due to the limited operating range and lack of a direct ignition timing control mechanism. Spark assisted compression ignition (SACI) has been shown by several research groups, including the work presented here, to provide such a mechanism, helping to control the phasing and stability of a primarily auto-igniting charge, as well as provide a means of extending the high load limit of HCCI while maintaining high thermal efficiency. The approach used in this study is unique in that flexible engine valve timing allowed for independent control of the thermal/compositional stratification associated with a large internal residual fraction, allowing its effect to be isolated from other thermophysical parameters. In these experiments, a single-cylinder engine equipped with fully-flexible valve actuation was used to explore the effects of spark assist in controlling peak heat release rates. With spark assist, a small portion of the heat release occurred via flame propagation, increasing the overall duration of the combustion event and dramatically reducing peak rates of heat release. At constant engine load and combustion phasing, peak heat release rates were reduced by 40% by controlling spark timing and unburned gas temperature via changes in internal and external EGR rates. Internal EGR was adjusted by varying the duration of negative valve overlap (NVO); for the range of NVO investigated, potential variations in in-cylinder mixing and thermal/compositional stratification were found to have a weak effect on burn characteristics, confirming the notion that temperature and spark timing are the primary variables affecting SACI burn rates for a fixed mixture composition. In the experiments, heat release analysis showed that the behavior of SACI was consistent with the theoretical kinetics associated with turbulent flame propagation and auto-ignition, supporting the hypothesis that SACI is essentially two distinct energy release events coupled by compression heating from an expanding flame front. The results of this work provide new insights into the physical and chemical mechanisms important during low temperature combustion. The results confirm proposed representations of SACI, and thereby provide direction for developing new advanced low temperature engine strategies. Advisors/Committee Members: Assanis, Dionissios N. (committee member), Wooldridge, Margaret S. (committee member), Driscoll, James F. (committee member), Boehman, Andre L. (committee member), Lavoie, George A. (committee member), Martz, Jason Brian (committee member).

Subjects/Keywords: Spark Assisted Compression Ignition Combustion; Low Temperature Combustion; Mechanical Engineering; Engineering

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APA (6^th Edition):

Olesky, L. K. (2013). An Experimental Investigation of the Burn Rates of Naturally Aspirated Spark Assisted Compression Ignition Combustion in a Single Cylinder Engine with Negative Valve Overlap. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/99979

Chicago Manual of Style (16^th Edition):

Olesky, Laura Katherine. “An Experimental Investigation of the Burn Rates of Naturally Aspirated Spark Assisted Compression Ignition Combustion in a Single Cylinder Engine with Negative Valve Overlap.” 2013. Doctoral Dissertation, University of Michigan. Accessed April 14, 2021. http://hdl.handle.net/2027.42/99979.

MLA Handbook (7^th Edition):

Vancouver:

Olesky LK. An Experimental Investigation of the Burn Rates of Naturally Aspirated Spark Assisted Compression Ignition Combustion in a Single Cylinder Engine with Negative Valve Overlap. [Internet] [Doctoral dissertation]. University of Michigan; 2013. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/2027.42/99979.

Council of Science Editors:

Olesky LK. An Experimental Investigation of the Burn Rates of Naturally Aspirated Spark Assisted Compression Ignition Combustion in a Single Cylinder Engine with Negative Valve Overlap. [Doctoral Dissertation]. University of Michigan; 2013. Available from: http://hdl.handle.net/2027.42/99979

5. Middleton, Robert John. Simulation of Spark Assisted Compression Ignition Combustion Under EGR Dilute Engine Operating Conditions.

Degree: PhD, Mechanical Engineering, 2014, University of Michigan

URL: http://hdl.handle.net/2027.42/107052

► Spark Assisted Compression Ignition (SACI) combustion has been shown to provide highly efficient, potentially low NOx operation similar to Homogeneous Charge Compression Ignition (HCCI) combustion.… (more)

▼ Spark Assisted Compression Ignition (SACI) combustion has been shown to provide highly efficient, potentially low NOx operation similar to Homogeneous Charge Compression Ignition (HCCI) combustion. Direct control over ignition timing and burn rate through SACI operation has the ability to overcome shortcomings of HCCI operation allowing an increase in power density. Detailed SACI models capable of capturing the charge preparation process and impact of dilution method on combustion are currently limited. The current work addresses this need by developing such a model and investigating SACI combustion in an engine simulation. Modeling requires valid predictions of laminar flame speeds under SACI conditions which are not available in the literature. To address this need under highly EGR dilute, high preheat temperature SACI conditions, laminar reaction front simulations were conducted. Moderate burning velocities were observed for EGR dilutions typical SACI operation, provided that preheat temperatures were elevated and burned gas temperatures exceeded 1450K. For a given preheat and burned gas temperature, EGR dilution suppressed burning velocities relative to air dilution, behavior attributed to decreases in mixture oxygen. Correlations of laminar burning velocity and thickness were developed from these data. An existing model for HCCI, SI, and SACI combustion in KIVA-3V was extended to capture engine breathing and charge preparation by direct injection under conditions utilizing EGR dilution. The model was capable of predicting trend-wise agreement with metal engine cylinder pressure measurements for HCCI, SI, and SACI combustion. Analysis showed that during SACI operation, compression heating from reaction front heat release increased the end-gas temperature to initiate end-gas auto-ignition, providing control over the combustion process. Manipulation of the flame heat release by varying intake temperature, spark timing, and dilution composition allowed control over heat release rates independent of combustion phasing, reducing peak heat release rates while increasing load and efficiency. The influences on end-gas heat release rate were the total end-gas mass and the temperature stratification prior to auto-ignition, which evolved significantly during the flame propagation phase. Insights from this work can be used to guide SACI operating strategies to enable high efficiency engine operation at higher power density than with HCCI combustion. Advisors/Committee Members: Assanis, Dionissios N. (committee member), Wooldridge, Margaret S. (committee member), Fidkowski, Krzysztof J. (committee member), Im, Hong (committee member), Martz, Jason Brian (committee member), Lavoie, George (committee member).

Subjects/Keywords: Combustion; Spark Assisted Compression Ignition; Mechanical Engineering; Engineering

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APA (6^th Edition):

Middleton, R. J. (2014). Simulation of Spark Assisted Compression Ignition Combustion Under EGR Dilute Engine Operating Conditions. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/107052

Chicago Manual of Style (16^th Edition):

Middleton, Robert John. “Simulation of Spark Assisted Compression Ignition Combustion Under EGR Dilute Engine Operating Conditions.” 2014. Doctoral Dissertation, University of Michigan. Accessed April 14, 2021. http://hdl.handle.net/2027.42/107052.

MLA Handbook (7^th Edition):

Middleton, Robert John. “Simulation of Spark Assisted Compression Ignition Combustion Under EGR Dilute Engine Operating Conditions.” 2014. Web. 14 Apr 2021.

Vancouver:

Middleton RJ. Simulation of Spark Assisted Compression Ignition Combustion Under EGR Dilute Engine Operating Conditions. [Internet] [Doctoral dissertation]. University of Michigan; 2014. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/2027.42/107052.

Council of Science Editors:

Middleton RJ. Simulation of Spark Assisted Compression Ignition Combustion Under EGR Dilute Engine Operating Conditions. [Doctoral Dissertation]. University of Michigan; 2014. Available from: http://hdl.handle.net/2027.42/107052

6. Lillo, Peter. Topological Development of Homogeneous-Charge and Stratified-Charge Flames in an Internal Combustion Engine.

Degree: PhD, Mechanical Engineering, 2016, University of Michigan

URL: http://hdl.handle.net/2027.42/135897

► No technology can currently replace fossil fuel powered internal combustion engines as the primary source of transportation power. For better or worse, the next generation… (more)

▼ No technology can currently replace fossil fuel powered internal combustion engines as the primary source of transportation power. For better or worse, the next generation of automobiles will continue to be powered by combustion. As such, it is in our best interest to learn how to burn fuel in the smartest manner. There are many advanced combustion strategies that promise efficiency improvements over conventional strategies, most of which have failed to make it onto the road due to technical deficiencies. Many of these strategies, such as spray-guided stratified-charge combustion, rely upon the precise partial mixing of fuel with oxidizer inside the combustion chamber. Advanced computational tools are being developed to aid such challenging designs. However, a lack of understanding of in-cylinder flame physics and computational power limitations continues to hinder the predictive abilities of engine models. In this work, engine flame topological development is studied. Flame wrinkled-ness is both one of the most important and poorly understood engine combustion phenomena. Generally, a flame may wrinkle for two reasons: (i) its own naturally instabilities and/or (ii) through interaction with turbulent flow. The relative contribution of these two causes towards flame wrinkled-ness in the engine environment was unclear so targeted experiments were performed to provide some clarity. The development of flame wrinkled-ness within an optically accessible engine was measured with a combination of planar laser induced fluorescence and stereo particle image velocimetry under homogeneous-charge and stratified-charge conditions. From this, equivalence ratio, charge velocities, and flame wrinkled-ness were quantified and analyzed. For the iso-octane/toluene mixtures studied the flame wrinkling was insensitive to thermo-diffusive flame front instabilities. The relative contribution of wrinkles of various spatial scales towards overall flame wrinkled-ness was also measured. Homogeneous-charge flames generally had lower wrinkling factors than stratified-charge flames. Overall, flame wrinkled-ness increased with flame size under both modes of engine operation. Large flames demonstrated an ability to maintain more large scale wrinkles than small flames, which contributed to their overall higher levels of wrinkled-ness. Based on the observations, suggestions are provided for those who are developing advanced homogeneous and stratified-charge engine models. Advisors/Committee Members: Sick, Volker (committee member), Driscoll, James F (committee member), Boehman, Andre L (committee member), Martz, Jason Brian (committee member), Reuss, David L (committee member).

Subjects/Keywords: Internal Combustion Engine; Engine Flame Topology; Homogeneous Charge Combustion; Stratified Charge Combustion; Optical Diagnostics; Flame Wrinkling; Mechanical Engineering; Engineering

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APA (6^th Edition):

Lillo, P. (2016). Topological Development of Homogeneous-Charge and Stratified-Charge Flames in an Internal Combustion Engine. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/135897

Chicago Manual of Style (16^th Edition):

Lillo, Peter. “Topological Development of Homogeneous-Charge and Stratified-Charge Flames in an Internal Combustion Engine.” 2016. Doctoral Dissertation, University of Michigan. Accessed April 14, 2021. http://hdl.handle.net/2027.42/135897.

MLA Handbook (7^th Edition):

Lillo, Peter. “Topological Development of Homogeneous-Charge and Stratified-Charge Flames in an Internal Combustion Engine.” 2016. Web. 14 Apr 2021.

Vancouver:

Lillo P. Topological Development of Homogeneous-Charge and Stratified-Charge Flames in an Internal Combustion Engine. [Internet] [Doctoral dissertation]. University of Michigan; 2016. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/2027.42/135897.

Council of Science Editors:

Lillo P. Topological Development of Homogeneous-Charge and Stratified-Charge Flames in an Internal Combustion Engine. [Doctoral Dissertation]. University of Michigan; 2016. Available from: http://hdl.handle.net/2027.42/135897

7. Kodavasal, Janardhan. Effect of Charge Preparation Strategy on HCCI Combustion.

Degree: PhD, Mechanical Engineering, 2013, University of Michigan

URL: http://hdl.handle.net/2027.42/99766

► A critical factor determining Homogeneous Charge Compression Ignition (HCCI) combustion characteristics and emissions is preparation of the fuel-diluent charge prior to ignition. The choice of… (more)

▼ A critical factor determining Homogeneous Charge Compression Ignition (HCCI) combustion characteristics and emissions is preparation of the fuel-diluent charge prior to ignition. The choice of charge preparation strategy impacts diluent composition and stratification. Presently, there is a gap in fundamental understanding as to the impact of these strategies on charge distribution within the reaction space and consequent effects on HCCI combustion. In this doctoral work, fully-coupled CFD/chemical kinetics simulations are performed for various competing charge preparation strategies at a typical HCCI operating point to study the differences in burn duration and emissions arising from these strategies. The strategies studied are: air versus external EGR dilution, Negative Valve Overlap (NVO) versus Positive Valve Overlap (PVO) operation, and premixed fueling versus direct injection. The CFD reaction space is analyzed to determine the reactivity stratification prior to ignition arising from each of these strategies. A sequential CFD-multi-zone model is developed as a diagnostic tool wherein CFD simulation is performed over the gas exchange period until a transition point before TDC, after which the CFD reaction space is mapped onto a multi-zone chemical kinetic model. This tool is used to decouple various concurrent effects. For example, by selectively choosing to map thermal stratification from the CFD domain onto the multi-zone model while ignoring compositional stratification, the relative contributions of thermal and compositional stratification arising from NVO operation are isolated. Based on these insights from CFD, a standalone quasi-dimensional HCCI combustion model incorporating kinetics is built, featuring a computationally efficient methodology (developed as part of this work) to capture wall heat loss driven thermal stratification, as an alternative to expensive CFD simulation. It is shown that predictions from this model correspond well with results from detailed CFD/kinetics simulations over a range of operating conditions, for different engine geometries, while being up to two-orders of magnitude faster than CFD, making this model ideal for use in system-level codes. Advisors/Committee Members: Assanis, Dionissios N. (committee member), Im, Hong G. (committee member), Driscoll, James F. (committee member), Martz, Jason Brian (committee member), Babajimopoulos, Aristotelis (committee member), Borgnakke, Claus (committee member), Lavoie, George A. (committee member).

Subjects/Keywords: HCCI; Combustion; Internal Combustion Engine; Stratification; CFD; Negative Valve Overlap; Mechanical Engineering; Engineering

…Figure 6.5 – University of Michigan FFVA engine CFD mesh…

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APA (6^th Edition):

Kodavasal, J. (2013). Effect of Charge Preparation Strategy on HCCI Combustion. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/99766

Chicago Manual of Style (16^th Edition):

Kodavasal, Janardhan. “Effect of Charge Preparation Strategy on HCCI Combustion.” 2013. Doctoral Dissertation, University of Michigan. Accessed April 14, 2021. http://hdl.handle.net/2027.42/99766.

MLA Handbook (7^th Edition):

Kodavasal, Janardhan. “Effect of Charge Preparation Strategy on HCCI Combustion.” 2013. Web. 14 Apr 2021.

Vancouver:

Kodavasal J. Effect of Charge Preparation Strategy on HCCI Combustion. [Internet] [Doctoral dissertation]. University of Michigan; 2013. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/2027.42/99766.

Council of Science Editors:

Kodavasal J. Effect of Charge Preparation Strategy on HCCI Combustion. [Doctoral Dissertation]. University of Michigan; 2013. Available from: http://hdl.handle.net/2027.42/99766

8. Kim, Doohyun. Conventional and Alternative Jet Fuels for Diesel Combustion: Surrogate Development and Insights into the Effect of Fuel Properties on Ignition.

Degree: PhD, Mechanical Engineering, 2016, University of Michigan

URL: http://hdl.handle.net/2027.42/120818

► The use of kerosene-based jet fuels for all military applications has been mandated by U.S. military’s single fuel forward concept. Recently, interest in non-petroleum-derived alternative… (more)

▼ The use of kerosene-based jet fuels for all military applications has been mandated by U.S. military’s single fuel forward concept. Recently, interest in non-petroleum-derived alternative jet fuels has also been increasing as a way to diversify the source of jet fuels. Computational Fluid Dynamics (CFD) simulations with detailed kinetic modeling can be used to model the combustion behavior of real fuel and predict their performance. This thesis revolves around the development of a surrogate mixture for real jet fuels, kinetic models for the surrogate components, and CFD simulations of diesel engines to assess the effects of surrogate’s chemical and physical properties on fundamental combustion processes. Fuel surrogates are mixtures of one or more simple fuels that are designed to emulate key properties of a more complex fuel. For the first time we report on a comprehensive jet fuel surrogates that successfully emulate physical and chemical properties of conventional and alternative jet fuels. To identify the target properties that need to be used to reproduce the diesel combustion, in the first part of this dissertation, a sensitivity analysis was conducted with CFD simulations of pure n-dodecane spray in a constant volume chamber to identify temperature dependent liquid physical properties that are of significance to the diesel ignition process. Out of six physical properties that were tested, density, viscosity, volatility, and specific heat showed major impact on liquid penetration length and ignition delay time. Using a six-component surrogate palette (n-dodecane, n-decane, iso-cetane, iso-octane, decalin, and toluene), the surrogate optimizer generated surrogate mixtures for Jet-A POSF-4658, a petroleum-derived conventional jet fuel, IPK POSF-5642, a coal-derived synthetic jet fuel, and S-8 POSF-4734, a natural-gas-derived synthetic jet fuel. Kinetic modeling of the surrogate fuels were enabled by a detailed chemical mechanism. Numerical experiments were conducted using CFD simulations to evaluate the importance of physical and chemical properties of surrogates on the ignition process of the fuel spray for two fuels. This study indicates that the chemical properties of fuel are much more important to the duration of the ignition delay period than the physical properties, which emphasizes the chemical aspect of the diesel ignition phenomena. Advisors/Committee Members: Violi, Angela (committee member), Martz, Jason Brian (committee member), Gamba, Mirko (committee member), Schihl, Peter Joseph (committee member), Assanis, Dionissios N (committee member).

Subjects/Keywords: fuel surrogate development; diesel combustion; Mechanical Engineering; Engineering

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APA (6^th Edition):

Kim, D. (2016). Conventional and Alternative Jet Fuels for Diesel Combustion: Surrogate Development and Insights into the Effect of Fuel Properties on Ignition. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/120818

Chicago Manual of Style (16^th Edition):

Kim, Doohyun. “Conventional and Alternative Jet Fuels for Diesel Combustion: Surrogate Development and Insights into the Effect of Fuel Properties on Ignition.” 2016. Doctoral Dissertation, University of Michigan. Accessed April 14, 2021. http://hdl.handle.net/2027.42/120818.

MLA Handbook (7^th Edition):

Kim, Doohyun. “Conventional and Alternative Jet Fuels for Diesel Combustion: Surrogate Development and Insights into the Effect of Fuel Properties on Ignition.” 2016. Web. 14 Apr 2021.

Vancouver:

Kim D. Conventional and Alternative Jet Fuels for Diesel Combustion: Surrogate Development and Insights into the Effect of Fuel Properties on Ignition. [Internet] [Doctoral dissertation]. University of Michigan; 2016. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/2027.42/120818.

Council of Science Editors:

Kim D. Conventional and Alternative Jet Fuels for Diesel Combustion: Surrogate Development and Insights into the Effect of Fuel Properties on Ignition. [Doctoral Dissertation]. University of Michigan; 2016. Available from: http://hdl.handle.net/2027.42/120818

9. Nuesch, Sandro Patrick. Analysis and Control of Multimode Combustion Switching Sequence.

Degree: PhD, Mechanical Engineering, 2015, University of Michigan

URL: http://hdl.handle.net/2027.42/116660

► Highly dilute, low temperature combustion technologies, such as homogeneous charge compression ignition (HCCI), show significant improvements in internal combustion engine fuel efficiency and engine-out NOx… (more)

▼ Highly dilute, low temperature combustion technologies, such as homogeneous charge compression ignition (HCCI), show significant improvements in internal combustion engine fuel efficiency and engine-out NOx emissions. These improvements, however, occur at limited operating range and conventional spark ignition (SI) combustion is still required to fulfill the driver's high torque demands. In consequence, such multimode engines involve discrete switches between the two distinct combustion modes. Such switches unfortunately require a finite amount of time, during which they exhibit penalties in efficiency. Along with its challenges, the design of such a novel system offers new degrees of freedom in terms of engine and aftertreatment specifications. Prior assessments of this technology were based on optimistic assumptions and neglected switching dynamics. Furthermore, emissions and driveability were not fully addressed. To this end, a comprehensive simulation framework, which accounts for above-mentioned penalties and incorporates interactions between multimode engine, driveline, and three-way catalyst (TWC), has been developed. Experimental data was used to parameterize a novel mode switch model, formulated as finite-state machine. This model was combined with supervisory controller designs, which made the switching decision. The associated drive cycle results were analyzed and it was seen that mode switches have significant influence on overall fuel economy, and the issue of drivability needs to be addressed within the supervisory strategy. After expanding the analysis to address emissions assuming a TWC, it was shown that, in practice, HCCI operation requires the depletion of the TWC's oxygen storage capacity (OSC). For large OSCs the resulting lean-rich cycling nullifies HCCI's original efficiency benefits. In addition, future emissions standards are still unlikely to be fulfilled, deeming a system consisting of such a multimode engine and TWC with generous OSC unfavorable. In view of these difficulties, the modeling framework was extended to a mild hybrid electric vehicle (HEV) allowing a prolonged operation in HCCI mode with associated fuel economy benefits during city driving. Further analysis on how to reduce NOx while maintaining fuel economy resulted in a counterintuitive suggestion. It was deemed beneficial to constrain the HCCI operation to a small region, exhibiting lowest NOx, while reducing instead of increasing the OSC. Advisors/Committee Members: Stefanopoulou, Anna G (committee member), Kolmanovsky, Ilya Vladimir (committee member), Boehman, Andre L (committee member), Martz, Jason Brian (committee member).

Subjects/Keywords: Internal combustion engine; Supervisory control of a multimode combustion engine; Homogeneous charge compression ignition (HCCI); Drive cycle analysis for fuel economy and emissions; Mechanical Engineering; Engineering

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

APA (6^th Edition):

Nuesch, S. P. (2015). Analysis and Control of Multimode Combustion Switching Sequence. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/116660

Chicago Manual of Style (16^th Edition):

Nuesch, Sandro Patrick. “Analysis and Control of Multimode Combustion Switching Sequence.” 2015. Doctoral Dissertation, University of Michigan. Accessed April 14, 2021. http://hdl.handle.net/2027.42/116660.

MLA Handbook (7^th Edition):

Nuesch, Sandro Patrick. “Analysis and Control of Multimode Combustion Switching Sequence.” 2015. Web. 14 Apr 2021.

Vancouver:

Nuesch SP. Analysis and Control of Multimode Combustion Switching Sequence. [Internet] [Doctoral dissertation]. University of Michigan; 2015. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/2027.42/116660.

Council of Science Editors:

Nuesch SP. Analysis and Control of Multimode Combustion Switching Sequence. [Doctoral Dissertation]. University of Michigan; 2015. Available from: http://hdl.handle.net/2027.42/116660

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