Abstract
The multiple injection strategy has been widely used in diesel engines to reduce engine noise, NOx and soot formation. Fuel injection developments such as the common-rail and piezo-actuator system provide more precise control of the injection quantity and time under higher injection pressures. As various injection strategies become accessible, it is important to understand the interaction of each fuel stream and following combustion process under the multiple injection strategy. To investigate these complex processes quantitatively, numerical analysis using CFD is a good alternative to overcome the limitation of experiments. A modified 2-D flamelet model is further developed from previous work to model multi-fuel streams with higher accuracy. The model was validated under various engine operating conditions and captures the combustion and emissions characteristics as well as several parametric variations. The model is expected to be used to suggest advanced injection strategies in engine development processes.
Highlights
The diesel engine has been widely used because of its great torque and high thermal efficiency with direct injection under a higher compression ratio [1]
The objective of this study is to investigate the physical mechanism of the combustion process of multiple injection using the modified 2-D flamelet model with the introduction of the collapse method
The modified 2-D flamelet model was further improved for the simulation of combustion characteristics under various multi-fuel streams injected more than three different times
Summary
The diesel engine has been widely used because of its great torque and high thermal efficiency with direct injection under a higher compression ratio [1]. The multiple injection strategy was suggested as an alternative where a small amount of pilot injections can heat the combustion chamber and alter the turbulent mixing fields that affect the combustion of the main fuel stream and make mixture fields more homogenous [7,8,9,10]. In this situation, development of injection technologies could facilitate more precise control of the injection rate and higher injection pressure [11,12]. Development of the injection system is an ongoing process; it provides more precise control of the fuel quantity with duration and has the potential to simultaneously reduce the emissions under the same torque
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