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Empirical results indicated that the engine emission and fuel efficiency of low-temperature combustion (LTC) cycles can be optimized by adjusting the fuel-injection scheduling in order to obtain appropriate combustion energy release or heat-release rate patterns. Based on these empirical results the heat-release characteristics were correlated with the regulated emissions such as soot, hydrocarbon and oxides of nitrogen. The transition from conventional combustion to LTC with the desired set of heat-release rate has been implemented. This transition was facilitated with the simplified heat-release characterization wherein each of the consecutive engine cycles was analyzed with a real-time controller embedded with an FPGA (field programmable gate array) device. The analyzed results served as the primary feedback control signals to adjust fuel injection scheduling. The experimental efforts included the boost/backpressure, exhaust gas recirculation, and load transients in the LTC region.

Simultaneous low NOx (< 0.15 g/kWh) & soot (< 0.01 g/kWh) are attainable for enhanced premixed combustion that may lead to higher levels of hydrocarbons and carbon monoxide emissions as the engine cycles move to low temperature combustion, which is a departure from the ultra low hydrocarbon and carbon monoxide emissions, typical of the high compression ratio diesel engines. As a result, the fuel efficiency of such modes of combustion is also compromised (up to 5%). In this paper, advanced strategies for fuel injection are devised on a modern 4-cylinder common rail diesel engine modified for single cylinder research. Thermal efficiency comparisons are made between the low temperature combustion and the conventional diesel cycles. The fuel injection strategies include single injection with heavy EGR, and early multi-pulse fuel injection under low or medium engine loads respectively.

Extensive empirical work indicates that the exhaust emission and fuel efficiency of modern common-rail diesel engines characterise strong resilience to biodiesel fuels when the engines are operating in conventional high temperature combustion cycles. However, as the engine cycles approach the low temperature combustion (LTC) mode, which could be implemented by the heavy use of exhaust gas recirculation (EGR) or the homogeneous charge compression ignition (HCCI) type of combustion, the engine performance start to differ between the use of conventional and biodiesel fuels. Therefore, a set of fuel injection strategies were compared empirically under independently controlled EGR, intake boost, and exhaust backpressure in order to improve the neat biodiesel engine cycles.

Low temperature combustion (LTC), though effective to reduce soot and oxides of nitrogen (NOx) simultaneously from diesel engines, operates in narrowly close to unstable regions. Adaptive control strategies are developed to expand the stable operations and to improve the fuel efficiency that was commonly compromised by LTC. Engine cycle simulations were performed to better design the combustion control models. The research platform consists of an advanced common-rail diesel engine modified for the intensified single cylinder research and a set of embedded real-time (RT) controllers, field programmable gate array (FPGA) devices, and a synchronized personal computer (PC) control and measurement system.

Engine performance and emission comparisons were made between the use of 100% soy, Canola and yellow grease derived biodiesel fuels and an ultra-low sulphur diesel fuel in the oxygen deficient regions, i.e. full or high load engine operations. Exhaust gas recirculation (EGR) was extensively applied to initiate low temperature combustion. An intake throttling valve was implemented to increase the differential pressure between the intake and exhaust in order to increase and enhance the EGR. The intake temperature, pressure, and EGR levels were modulated to improve the engine fuel efficiency and exhaust emissions. Furthermore, a preliminary ignition delay correlation under the influence of EGR was developed. Preliminary low temperature combustion modelling of the biodiesel and diesel fuels was also conducted. The research intends to achieve simultaneous reductions of nitrogen oxides and soot emissions in modern production diesel engines when biodiesel is applied.

Preliminary empirical and modeling analyses are conducted to evaluate the energy efficiency of in-cylinder and external fuel injection strategies and their impact on the energy required to enable diesel particulate filter (DPF) regeneration for instance. During the tests, a thermal wave that is generated from the engine propagates along the exhaust pipe to the DPF substrate. The thermal response of the exhaust system is recorded with the thermocouple arrays embedded in the exhaust system. To implement the external fuel injection, an array of thermocouples and pressure sensors in the DPF provide the necessary feedback to the control system. The external fuel injection is dynamically adjusted based on the thermal response of the DPF substrate to improve the thermal management and to reduce the supplemental energy. This research intends to quantify the effectiveness of the supplemental energy utilization on aftertreatment enabling.

Common-rail fuel systems have been recognized as an effective means to shape the heat release rate. In this paper measured cylinder pressure and fuel injection data for a common-rail diesel engine were analyzed to develop an empirical heat release rate model. A set of discrete Wiebe functions, one to describe the pilot injection combustion and the other to describe the main injection combustion, have been proposed to model the heat release data. The coefficients in the model were adjusted to match the observed heat release diagram. An expression for ignition delay for pilot injection and main injection has also been suggested for test conditions.

Empirical and analytical investigations are conducted to evaluate the thermal response of exhaust pipe plenums at different levels of exhaust gas recirculation and through a variety of fuel delivery strategies. The effectiveness of different combustion control techniques is evaluated for moderating the engine-out exhaust temperature. Comparison of the external fuel injection with in-cylinder post injection for enabling aftertreatment is provided which indicates the stronger temperature raising potential of the external fuel injection. This research attempts to quantify the thermal response of the exhaust pipe plenums and its effects on the gas temperature at the inlet of the aftertreatment devices. The measurement and modeling of the dynamic thermal response in this research intend to improve the performance of diesel aftertreatment devices.

Exhaust gas recirculation (EGR) is effective to reduce nitrogen oxides (NOx) from diesel engines. However, when excessive EGR is applied, the engine operation reaches zones with higher combustion instability, carbonaceous emissions, and power losses. In order to improve the engine combustion process with the use of heavy EGR, the influences of boost pressure, intake temperature, and fuel injection timing are evaluated. An adaptive fuel injection strategy is applied as the EGR level is progressively elevated towards the limiting conditions. Additionally, characterization tests are performed to improve the control of the homogeneous charge compression ignition (HCCI) type of engine cycles, especially when heavy EGR levels are applied to increase the load level of HCCI operations. This paper constitutes the preparation work for a variety of algorithms currently being investigated at the authors' laboratory as a part of the model-based NOx control research.

The exhaust emission and performance characteristics of a 100% biodiesel fuel was evaluated on a single cylinder direct injection diesel engine that had been modified to allow multi-pulse diesel fuel injection at the intake port and independent control of intake heating, exhaust gas recirculation and throttling. Firstly, conventional single-shot direct injection tests were conducted and comparisons made between the use of an ultra-low sulphur diesel fuel and the biodiesel fuel. Secondly, tests for the premixed combustion of neat biodiesel were performed. Exhaust gas recirculation was applied extensively to initiate the low temperature combustion for the conventional in-cylinder single injection operation and to moderate the timing of the homogeneous charge compression ignition for the intake-port sequential injection. Because of the high viscosity and low volatility of the biodiesel, pilot-ignited homogeneous charge compression ignition was used.

Diesel engine exhausts commonly contain a high level of surplus oxygen and a significant amount of thermal energy. In this study the authors have theoretically investigated a way of utilizing the thermal energy and the surplus oxygen of exhaust gases to produce gaseous fuel in a rich combustor placed in an exhaust gas recirculation (EGR) loop. In the rich combustor, a small amount of diesel fuel will be catalytically reformed on a palladium/platinum based catalyst to produce hydrogen and carbon monoxide. Since the catalytic EGR reformer is incorporated in the EGR loop, it enables the partial recovery of exhaust heat. The gaseous fuel produced in the rich combustor can be brought back into the engine in a pre-mixed condition, potentially reducing soot formation. The preliminary energy efficiency analysis has been performed by using CHEMKIN and an in-house engine simulation software SAES.

The study investigated the characteristics of the combustion, the emissions and the thermal efficiency of a direct injection diesel engine fuelled with neat n-butanol. Engine tests were conducted on a single cylinder four-stroke direct injection diesel engine. The engine ran at 6.5 bar IMEP and 1500 rpm engine speed. The intake pressure was boosted to 1.0 bar (gauge), and the injection pressure was controlled at 60 or 90 MPa. The injection timing and the exhaust gas recirculation (EGR) rate were adjusted to investigate the engine performance. The effect of the engine load on the engine performance was also investigated. The test results showed that the n-butanol fuel had significantly longer ignition delay than that of diesel fuel. n-Butanol generally led to a rapid heat release pattern in a short period, which resulted in an excessively high pressure rise rate. The pressure rise rate could be moderated by retarding the injection timing and lowering the injection pressure.