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A detailed second law analysis of dual fuel LTC is not yet available in the open literature even though dual fuel low temperature combustion (LTC) has been studied before. To address this gap, a previously validated, closed-cycle, multi-zone, simulation of diesel-natural gas dual fuel LTC was used to perform a second law analysis. In the current study, a 2.4-liter single-cylinder research engine operating at a nominal load of 6 bar BMEP and 1700 rpm was used. Zone-wise thermodynamic irreversibilities as well as total cumulative entropy generated and lost available work over the closed cycle were quantified. Subsequently, two convenient second-law parameters were defined: (1) the “lost available indicated mean effective pressure” (LAIMEP), which can be interpreted as an engine-size-normalized measure of available work that is lost due to thermodynamic irreversibilities (analogous to the relationship between indicated mean effective pressure and indicated work); (2) fuel conversion irreversibility (FCI), which is defined as the ratio of lost available work to total fuel chemical energy input. Finally, parametric studies were performed to quantify the effects of diesel start of injection, intake manifold temperature, and intake boost pressure on LAIMEP and FCI. The results show that significant entropy generation occurred in the flame zone (52-61 percent) and the burned zone (31-39 percent) while packets account for less than 6 percent of the overall irreversibilities. Parametric studies showed LAIMEPs in the range of 645-768 kPa and FCIs in the range of 32.8-39.2 percent at different engine operating conditions. Although the present study focused on dual fuel LTC, the conceptual definitions of LAIMEP and FCI are generally applicable for comparing the thermodynamic irreversibilities of IC engines of any size and operating on any combustion strategy.
It's crucial to use advanced combustion strategies to increase efficiency and decrease engine-out pollutants because of the compelling need to reduce the global carbon footprint. This dissertation proposes dual fuel low-temperature combustion as a viable strategy to decrease engine-out emissions and increase the thermal efficiency of future heavy-duty internal combustion (IC) engines. In dual fuel combustion, a low reactivity fuel (e.g. methane, propane) is ignited by a high reactivity fuel (diesel) in a compression-ignited engine. Generally, the energy fraction of low reactivity fuel is maintained at much higher levels than the energy fraction of the high reactivity fuel. For a properly calibrated engine, combustion occurs at lean and low-temperature conditions (LTC). This decreases the chances of the formation of soot and oxides of nitrogen within the engine. However, at low load conditions, this type of combustion results in high hydrocarbon and carbon monoxide emissions. The first part of this research experimentally examines the effect of methane (a natural gas surrogate) substitution on early injection dual fuel combustion at representative low loads of 3.3 and 5.0 bar BMEPs in a single-cylinder compression ignition engine (SCRE). Gaseous methane fumigated into the intake manifold at various methane energy fractions was ignited using a high-pressure diesel pilot injection at 310 CAD. Cyclic combustion variations at both loads were also analyzed to obtain further insights into the combustion process and identify opportunities to further improve fuel conversion efficiencies at low load operation. In the second part, the cyclic variations in dual fuel combustion of three different low reactivity fuels (methane, propane, and gasoline) ignited using a high-pressure diesel pilot injection was examined and the challenges and opportunities in utilizing methane, propane, and gasoline in diesel ignited dual fuel combustion, as well as strategies for mitigating cyclic variations, were explored. Finally, in the third part a CFD model was created for diesel methane dual fuel LTC. The validated model was used to investigate the effect of methane on diesel autoignition and various spray targeting strategies were explored to mitigate high hydrocarbon and carbon monoxide emissions at low load conditions.
The present manuscript discusses the performance and emission benefits due to two diesel injections in diesel-ignited methane dual fuel Low Temperature Combustion (LTC). A Single Cylinder Research Engine (SCRE) adapted for diesel-ignited methane dual fuelling was operated at 1500 rev/min and 5 bar BMEP with 1.5 bar intake manifold pressure. The first injection was fixed at 310 CAD. A 2nd injection sweep timing was performed to determine the best 2nd injection timing (as 375 CAD) at a fixed Percentage Energy Substitution (PES 75%). The motivation to use a second late injection ATDC was to oxidize Unburnt Hydrocarbons (HC) generated from the dual fuel combustion of first injection. Finally, an injection pressure sweep (550-1300 bar) helped achieve simultaneous reduction of HC (56%) and CO (43%) emissions accompanied with increased IFCE (10%) and combustion efficiency (12%) w.r.t. the baseline single injection (at 310 CAD) of dual fuel LTC.
The second law of thermodynamics is a powerful tool for calculating the amount of energy that can be converted to work (i.e., the exergy or availability of a system), which cannot be predicted using the first law. The objectives of this research project are to quantify the availability during the compression, combustion and expansion processes of a spark-ignited engine fueled with methane; and to highlight differences in the thermo-mechanical availability of the ideal and spark-ignition (SI) engine cycles. A cooperative single-cylinder research engine was used to measure the data required for availability analysis at equivalence ratios ranging between 0.83 and 1.25. The thermo-mechanical availability, normalized by the energy content of the mixture, was found to increase as the equivalence ratio decreases. First and second-law of Thermodynamics efficiencies also increased for fuel-leaner mixtures, but remained within four percent of each other for methane in both the ideal and the SI engine cycles.
Dual fuel combustion is one strategy to achieve low oxides of nitrogen and soot emissions while maintaining the fuel conversion efficiency of IC engines. However, it also suffers from high engine-out carbon monoxide and unburned hydrocarbon emissions, and the incidence of knock at high loads. The present work focused on CFD simulation of diesel-methane dual fuel combustion in a single-cylinder research engine (SCRE). For pure diesel combustion, a load sweep of 2.5 bar brake mean effective pressure (BMEP) to 7.5 bar BMEP was performed at a constant engine speed of 1500 rpm and a diesel injection pressure of 500 bar. For diesel-methane dual fuel combustion, a methane percent energy substitution sweep was performed from 30% to 90 % at 1500 rpm, 3.3 bar BMEP, 500 bar Pinj, and 355 crank angle degrees (CAD) diesel injection timing. Combustion, performance, and emissions results are presented and compared with experimental data where possible.
This book provides a complete description of instrumentation and in-cylinder measurement techniques for internal combustion engines. Written primarily for researchers and engineers involved in advanced research and development of internal combustion engines, the book provides an introduction to the instrumentation and experimental techniques, with particular emphasis on diagnostic techniques for in-cylinder measurements.
This book deals with novel advanced engine combustion technologies having potential of high fuel conversion efficiency along with ultralow NOx and particulate matter (PM) emissions. It offers insight into advanced combustion modes for efficient utilization of gasoline like fuels. Fundamentals of various advanced low temperature combustion (LTC) systems such as HCCI, PCCI, PPC and RCCI engines and their fuel quality requirements are also discussed. Detailed performance, combustion and emissions characteristics of futuristic engine technologies such as PPC and RCCI employing conventional as well as alternative fuels are analyzed and discussed. Special emphasis is placed on soot particle number emission characterization, high load limiting constraints, and fuel effects on combustion characteristics in LTC engines. For closed loop combustion control of LTC engines, sensors, actuators and control strategies are also discussed. The book should prove useful to a broad audience, including graduate students, researchers, and professionals Offers novel technologies for improved and efficient utilization of gasoline like fuels; Deals with most advanced and futuristic engine combustion modes such as PPC and RCCI; Comprehensible presentation of the performance, combustion and emissions characteristics of low temperature combustion (LTC) engines; Deals with closed loop combustion control of advanced LTC engines; State-of-the-art technology book that concisely summarizes the recent advancements in LTC technology. .
Author's Abstract: Restrictions in the allowable exhaust gas emissions of diesel engines has become a driving factor in the design, development, and implementation of internal combustion (IC) engines. A dual fuel research engine concept was developed and implemented in an indirect injected engine in order to research combustion characteristics and emissions for non-road applications. The experimental engine was operated at a constant speed and load 2400 rpm and 5.5 bar indicated mean effective pressure (IMEP). n-Butanol was port fuel injected at 10%, 20%, 30%, and 40% by mass fraction with neat ultra-low sulfur diesel (ULSD#2). Peak pressure, maximum pressure rise rates, and heat release rates all increased with the increasing concentration of n-Butanol. MPRR increased by 127% and AHRR increased by 30.5% as a result of the shorter ignition delay and combustion duration. Ignition delay and combustion duration were reduced by 3.6% and 31.6% respectively. This occurred despite the lower cetane number of n-Butanol as a result of increased mixing due to the port fuel injection of the alcohol. NOx and soot were simultaneously reduced by 21% and 80% respectively. Carbon monoxide and unburned hydrocarbons emissions were increased for the dual fuel combustion strategies due to valve overlap. Results display large emission reductions of harmful pollutants, such as NOx and soot.
This book provides an introduction to basic thermodynamic engine cycle simulations, and provides a substantial set of results. Key features includes comprehensive and detailed documentation of the mathematical foundations and solutions required for thermodynamic engine cycle simulations. The book includes a thorough presentation of results based on the second law of thermodynamics as well as results for advanced, high efficiency engines. Case studies that illustrate the use of engine cycle simulations are also provided.