Abstract
In order to meet the ever-more stringent emission standards, significant efforts have been devoted to the research and development of cleaner internal combustion engines. Diesel combustion and the formation of pollutants are directly influenced by the spatial and temporal distribution of the fuel injected. This study investigated the effects of dwell angle of split injection on diesel combustion and emissions in a high-speed common rail direct injection optical diesel engine. The fuel injection system was characterized through the measurement of the fuel injection rate and quantity for the tested strategies on a fuel injection test rig. In particular, the interaction between the two injection events was identified. Effects of the split injection dwell angle and the interactions of the two consecutive injection events on diesel combustion and exhaust emissions were then investigated in the single cylinder optical engine using heat release analysis and optical diagnostic techniques. The fuel injection process was illuminated by a high repetition copper vapour laser and recorded synchronously by a high speed video camera. The combustion temperature and soot distribution during the combustion process were measured by a recently developed high speed two-colour system. The results indicated that this injection mode has the potential to improve fuel economy and engine performance while substantially reducing the combustion noise, provided that the injection timings are appropriately selected.
Highlights
Diesel engines are extremely robust and reliable, capable of producing outstanding torque at low speeds, inherent high levels of regulated and unregulated emissions and combustion noise associated with conventional diesel engines have been the foremost reasons for relatively low market share until the late 1990s
Numerous research studies have been conducted aimed at more detailed investigation of fuel-air mixing and combustion processes as well as chemical/physical reactions involved in the production of pollutants, in particular nitrogen oxides (NOx) and particulate matter (PM), the two most perilous emissions produced by diesel engines
The effects of dwell angle of split injection on the fuel injection system performance and in-cylinder mixture formation, combustion and soot distribution were investigated in a single cylinder common rail (CR) fuel injection optical diesel engine
Summary
Diesel engines are extremely robust and reliable, capable of producing outstanding torque at low speeds, inherent high levels of regulated and unregulated emissions and combustion noise associated with conventional diesel engines have been the foremost reasons for relatively low market share until the late 1990s. Recent developments in diesel engine technology, higher fuel prices as well as incentivising tax regimes based on CO2 emission levels have led to a substantial shift in the automotive market with diesel engines claiming approximately 50% of the European car market [1]. In order to meet the ever more stringent emission standards, significant efforts have been devoted to the research and development of cleaner internal combustion (IC) engines. Numerous research studies have been conducted aimed at more detailed investigation of fuel-air mixing and combustion processes as well as chemical/physical reactions involved in the production of pollutants, in particular nitrogen oxides (NOx) and particulate matter (PM), the two most perilous emissions produced by diesel engines
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