Abstract
Due to the increasing awareness of environmental protection, limitations on exhaust emissions of diesel engines have become increasingly stringent. This challenges diesel engine manufacturers to find a new balance between engine performance and emissions. Advanced combustion modes for diesel engines, such as homogeneous charge compression ignition (HCCI) and premixed charge compression ignition (PCCI), which can simultaneously reduce exhaust emissions and substantially improve thermal efficiency, have drawn increasing attention. In order to allow enough time to prepare the homogeneous mixture, the early injection strategy has been utilized widely in HCCI and PCCI diesel engines. This paper is aimed at providing a comprehensive review of the effects of early injection parameters on the performance and emissions of HCCI and PCCI engines fueled by both diesel and alternative fuels. Various early injection parameters, including injection pressure, injection timing, and injection angle, are discussed. In addition, the effect of the blending ratio of alternative fuels is also summarized. Every change in parameters has its own advantages and disadvantages, which are explained in detail in order to help researchers choose the best early injection parameters for HCCI and PCCI engines.
Highlights
Due to the advantages of better fuel economy, durability, reliability, and high specific power output compared to gasoline engines, diesel engines are widely used for heavy-duty vehicles such as trucks, construction machines, and generators, and for light-duty ones including passenger cars [1,2,3].the well-known trade-off law of nitrogen oxides (NOx) and soot emissions for conventional diesel combustion makes it difficult to reduce NOx and soot simultaneously while maintaining a high level of thermal efficiency [4]
Though many researchers have used different early injection strategies in order to reduce emissions and improve the performance of homogeneous charge compression ignition (HCCI) and premixed charge compression ignition (PCCI) engines, there is no comprehensive review on the effects of early injection parameters in the literature. From this point of view, the purpose of this paper is to review the effects of various parameters of early injection, including injection pressure, injection timing, injection angle, and blending ratios of alternative fuel on the performance and emissions of HCCI and PCCI engines
The results indicated thermal efficiency and indicated mean effective pressure (IMEP) decreased with advanced injection timing
Summary
Due to the advantages of better fuel economy, durability, reliability, and high specific power output compared to gasoline engines, diesel engines are widely used for heavy-duty vehicles such as trucks, construction machines, and generators, and for light-duty ones including passenger cars [1,2,3]. The well-known trade-off law of nitrogen oxides (NOx) and soot emissions for conventional diesel combustion makes it difficult to reduce NOx and soot simultaneously while maintaining a high level of thermal efficiency [4]. The exhaust emitted from diesel engines, especially soot emission, has been proved to have undesirable effects on human health [5,6,7,8,9,10]. Many advanced combustion technologies have been studied. HCCI and PCCI combustion have proven to be promising strategies.
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