29 International Journal of Automotive Engineering Vol. 1, Number 1, January 2011 1. INTRODUCTION Conventional compression ignition (CI) engines are known for their high thermal efficiency in comparison with spark ignited (SI) engines. This makes CI engines a potential candidate for the future prime source of power for transportation sector to reduce greenhouse gas emissions and to shrink carbon foot print. However, CI engines produce high levels of NO x and soot emissions. Conventional methods to reduce NO x and soot emissions often result in the infamous NO x -soot trade-off [1]. One of the attractive methods for lowering emissions is low temperature combustion (LTC). Different kinds of low temperature combustion have been explored in the recent years, such as homogeneous charge compression ignition (HCCI), premixed charge compression ignition (PCCI) and high equivalence ratio combustion based on extensive use of high cooled EGR rates. Homogenous charge compression ignition (HCCI) based on the simultaneous ignition of a highly diluted premixed air-fuel mixture throughout the combustion chamber [2-4]. In this combustion, globally and locally lean mixture produces low soot owing to low local equivalence ratios and low NO x from low combustion temperatures. However, the control of combustion phasing and hence overall engine control is very difficult in HCCI combustion. Premixed Charge Compression Ignition (PCCI) is a further possibility for low emission combustion [5, 6]. This concept uses more advanced injection timing than for conventional CI engines. In this strategy, low NO x and soot emissions achieved by providing a better vaporized air-fuel mixture, which forms mixture conditions close to a homogenous charge at low temperature combustion condition. Although both the control of combustion phasing and reduction of pollutant emissions can be achieved in the PCCI regime, increase the amount of fuel injected beyond a certain level is resulted in knock that this is limiting the operating range of PCCI combustion. The use of high cooled EGR rate is other way to gain low temperature combustion condition. The use of EGR is very effective to mitigate NO x levels by reducing oxygen concentration in the intake system as well as chemical effects of added CO 2 and H 2 O [7]. Also, at low engine load condition, lower combustion Effect of Injection Characteristics on Emissions and Combustion of a Gasoline Fuelled Partially-Premixed Compression Ignition Engine A. Nemati 1,* , Sh. Khalilarya 2 , S. Jafarmadar 3 , H. Khatamnezhad 4 and V. Fathi 5 1,* MSc. Student, Department of Mechanical Engineering, Urmia University, Urmia, Iran. Email: arash.nemati.mech@gmail.com 2 Associated Prof, Department of Mechanical Engineering, Urmia University, Urmia, Iran 3 Assistant Prof, Department of Mechanical Engineering, Urmia University, Urmia, Iran 4 MSc. Student, Department of Mechanical Engineering, Urmia University, Urmia, Iran 5 MSc. Student, Department of Mechanical Engineering, Urmia University, Urmia, Iran Abstract Conventional compression ignition (CI) engines are known for their high thermal efficiency compared to spark ignited (SI) engines. Gasoline because of its higher ignition delay has much lower soot emission in comparison with diesel fuel. Using double injection strategy reduces the maximum heat release rate that leads to NO x emission reduction. In this paper, a numerical study of a gasoline fuelled heavy duty Caterpillar 3401 engine was conducted via three dimensional computational fluid dynamics (CFD) procedures and compared with experimental data. The model results show a good agreement with experimental data. To have a better design the effect of injection characteristics such as, the main SOI timing, injection duration and nozzle hole size investigated on combustion and emissions and an optimized point find. The results suggest an optimization in injection characteristics for simultaneous reduction of NO x and soot emissions with negligible change in IMEP. Keywords: Compression ignition engine, Gasoline fuel, Emission reduction, Combustion, Injection characteristics [ Downloaded from www.iust.ac.ir on 2021-12-05 ] 1 / 9