Experimental investigation on the characteristics and performance of homogeneous charge induced ignition(HCII) on a multi-cylinder heavy-duty engine

Abstract

This paper is focused on the characteristics and performance of HCII in conditions close to practical engine operating. For this purpose, extensive experiments have been conducted on a modified six-cylinder heavy-duty diesel engine, with six-cylinder HCII, high pressure exhaust gas recirculation(EGR) loop and appropriate pressure rise rate. The experiments mainly include two aspects. Firstly, gasoline ratio(GR), EGR ratio and start of injection(SOI), are studied to summarize the combustion and emission characteristics of HCII. Secondly, European steady state cycle(ESC) test is conducted to evaluate HCII performance over the whole engine map.Results suggest that large GR is beneficial to effective thermal efficiency(ETE) or/and nitrogen oxide(NOx) and smoke emissions, however, it is limited by maximum pressure rise rate at low load and uncontrollable ignition time at high load. Similarly, the application of EGR can improve gasoline combustion and decrease NOx emission, while it cannot be too much because of decreased ETE at low load and uncontrollable ignition time at high load. Meanwhile, SOI can be advanced to 40 crank angle degree(CAD) before top dead center(BTDC) to achieve extremely low NOx and smoke emissions and relatively high ETE. However, this strategy can only be applied to B25 and C25 points. Finally, great success is achieved by HCII in ESC test. Just with diesel oxidation catalyst(DOC), the weighted specific emissions of NOx, particulate matter(PM), hydrocarbon(HC) and carbon monoxide(CO) can be 1.841 g/(kW·h), 0.024 g/(kW·h), 0.115 g/(kW·h) and 0.896 g/(kW·h) respectively.