Abstract
Abstract With greater energy pressure and stricter emission standards, increasing power output and reducing emissions of engines are simultaneously required. To achieve this, considerable researches are motivated. In recent years, key and representative developments in the field of high-efficiency and clean engines have been carried out. Among them, a low temperature combustion concept called gasoline compression ignition (GCI) is widely considered by universities and research institutions around the world, since it has the potential to achieve ultra-low NO X and soot emissions while maintaining high thermal efficiency. However, GCI combustion mode has certain issues to be solved, such as combustion instability under low-load conditions. Therefore, this paper reviews the experimental, computational and optical studies on the combustion stability control of GCI combustion mode during low loads and describes the recent progress to improve combustion stability as well as points out the future work finally.
Highlights
Internal combustion engines, currently the most efficient thermal machines, are widely used in transportation, engineering equipment, agricultural machinery and other fields
The third-generation Gasoline Direct Compression Ignition (GDCI) test engine of Delphi using gasoline compression ignition (GCI) combustion has been achieved without combustion mode switching during the whole operation range using gasoline with octane number (RON) of 91, which meets the Tier 3 emissions standards combined with thermal efficiency up to 42%
To achieve In-exhaust gas recirculation (EGR), negative valve overlap (NVO) strategy was used by Borgqvist et al [83], and the results showed that the trapped hot residual gas had a positive effect on the extension of lower load limit, while a minimum attainable load of 1.75 bar indicated mean effective pressure (IMEP) was achieved
Summary
Currently the most efficient thermal machines, are widely used in transportation, engineering equipment, agricultural machinery and other fields. The quasi-homogeneous premixed gas by early fuel injection is moved to cylinder and can avoid high NOX and soot formation rates This prompted a trend in the engine research community to study Premixed Charge Compression Ignition (PCCI) [23, 24]. The obstacles including high level of unburned fuel, limit of low-load range and difficulty during cold start operation must be overcome before GCI combustion can be fully realised in commercial applications These could be attributed to the fact that the peak burned gas temperature is too low at low loads and cold start in GCI engines to consume much of the unburned fuel, which results in higher levels of HC and CO emissions compared with the conventional combustion. How to improve the combustion stability of GCI combustion under low-load conditions, or rather expand the low-load limit has become acrucial problem to be solved [40]
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