Control and optimization of spark ignition–controlled auto-ignition hybrid combustion based on stratified flame ignition

Abstract

Spark ignition–controlled auto-ignition hybrid combustion, also known as spark assisted compression ignition, is of considerable interest in gasoline engines because of its potential to enlarge the operating range of gasoline diluted combustion. However, it was found that the spark ignition–controlled auto-ignition hybrid combustion process was often characterized with large cycle-to-cycle variations. In this research, a new approach by combining the traditional second-order derivative method and Wiebe function fitting method was proposed to identify different heat release stages of spark ignition–controlled auto-ignition hybrid combustion. The heat release characteristics of the spark ignition–controlled auto-ignition hybrid combustion based on stratified flame ignition strategy and its control methods were investigated in detail. The effect of control parameters, including spark timing, direct injection ratio and dilution strategy, on improving the thermal efficiency and decreasing the variation of heat release trace in spark ignition–controlled auto-ignition hybrid combustion based on stratified flame ignition strategy was analysed. The advance of flame propagation ending point and the increase in the average heat release rate in flame propagation stage benefitted the fuel economy and reduced the variations of heat release in spark ignition–controlled auto-ignition hybrid combustion. Although the increase in direct injection ratio contributed to the stability of heat release in the spark ignition–controlled auto-ignition hybrid combustion based on the stratified flame ignition strategy, the thermal efficiency of spark ignition–controlled auto-ignition hybrid combustion cannot be effectively optimized due to the decrease in combustion efficiency. The application of exhaust gas recirculation and air dilution could decrease the variations of heat release process and increase the thermal efficiency of spark ignition–controlled auto-ignition hybrid combustion based on stratified flame ignition strategy.

Combustion development in a gasoline-fueled spark ignition–controlled auto-ignition engine operated at different spark timings and intake air temperatures

“…When HRR curves develop with the sharp increase, the first points of HRR″ become high values. However, in the case of lower HRR″ value at the transition point, the transition to CAI becomes very smooth and CAI dominated combustion phase decreases, which are similar to the study by Chen et al 45 CAtrans locations were determined by the points corresponding to the first HRR″ maximum points. Thus, MFBtrans, which represents the fraction of fuel mass consumed by flame propagation, was determined by employing the CAtrans locations, as shown in Figure 5(b).…”

Advancements in homogeneous charge compression ignition technology: Efficiency, emissions, and applications in the modern automotive industry

“…The HCCI combustion process is a unique mechanism. At the end of the engine's compression stroke, it utilizes the heat generated by compression to achieve auto-ignition of the homogeneous premixed fuel-air mixture, replacing the traditional spark plug ignition process [4]. During this process, fuel and air are quickly and thoroughly premixed in the intake manifold, forming a mixture.…”

Effects of Methanol Application on Carbon Emissions and Pollutant Emissions Using a Passenger Vehicle

“…These properties of methanol could reduce the local fuel-lean and fuel-rich zones in the cylinder to decrease fuel consumption and emissions caused by frequent acceleration and deceleration. Since the composition of the combustion products and flame propagation speed are significantly different for local fuel-lean and fuel-rich zones [39][40][41]. Moreover, the industrial technology for preparing methanol is very mature, which has low production cost [42], and technology equipment is relatively complete and easy to popularize [43].…”