Experimental investigation of the control strategy of high load extension under iso-butanol/biodiesel dual-fuel intelligent charge compression ignition (ICCI) mode

Abstract

Advanced combustion modes have shown the great advantages to achieve high thermal efficiency and low pollution emissions. However, lack of sufficiently control over combustion phasing of heat release under high and ultra-high engine load limits the commercial application. In this paper, an experimental investigation had been conducted to explore the control strategy under iso-butanol/biodiesel dual-fuel intelligent charge compression ignition (ICCI) mode for achieving the high engine load extension. The criteria is used to identify clean combustion under high load expansion, which the indicated thermal efficiency is 45% or higher, and nitrogen oxides (NOx) emissions should be below 400 ppm. The results show that stable and controllable ICCI operation is obtained under high and ultra-high engine load. An iso-butanol single direct injection in the intake stroke, biodiesel double direct injection strategy in the compression stroke and near top dead center, respectively, offers a very competitive pathway to expand the engine load with clean and highly efficient combustion, in which the maximum indicated thermal efficiency reaches 49.9% and NOx emissions below 100 ppm at the indicated mean effective pressure (IMEP) of 12 bar, and the maximum engine load reaches 18 bar IMEP (96% engine load). At higher engine load, lower iso-butanol energy ratio is used to reduce the in-cylinder pressure and maximum pressure rise rate, while punishes the engine thermal efficiency and emissions. With the iso-butanol energy ratio increase, the lower in-cylinder reactivity leads to the increase of incomplete combustion products. In addition, the exhaust gas recirculation (EGR) is essential on the reduction of NOx emissions, and the second biodiesel injection duration is increased with the engine load increase for the purpose of the load expansion.