Investigations on load range extension of a homogeneous charge compression ignited light-duty diesel engine operated with diisopropyl ether and gasoline blends

Abstract

A major obstacle for commercial implementation of homogeneous charge compression ignition (HCCI) combustion mode is a narrow operating load range. Several thermal and fuel management strategies have been investigated so far to address the shortcomings of HCCI, among which fuel management strategies are generally more effective. The present study intends to utilize high volatile, optimum reactivity fuel to extend the operating load range of a light-duty diesel engine operated in HCCI mode. Experiments are conducted at the rated engine speed, and varying load conditions. The tested fuels include blends of gasoline and diisopropyl ether and the additive 2-ethyl hexyl nitrate (2-EHN). Diisopropyl ether is a low reactivity, and high volatile renewable fuel that has the potential to replace crude oil derived gasoline. In the fuel blends, the proportion of diisopropyl ether is increased from 10% to 60% by volume with a corresponding decrease in gasoline proportion. The results obtained are compared with diesel HCCI considered as the reference. The engine can operate only up to 38% of rated load (2.02 bar brake mean effective pressure) in diesel HCCI mode, which is increased up to 58% of rated load (3.08 bar brake mean effective pressure) with diisopropyl ether-gasoline-2-EHN fuel blends. An improvement in indicated thermal efficiency is observed upon increasing the diisopropyl ether content in the tested fuel blends. The oxides of nitrogen and smoke emissions are low in HCCI with all the fuel blends, while the unburned hydrocarbon and carbon monoxide emissions increase compared to diesel HCCI. Overall, the present research shows that diisopropyl ether is a potential fuel to achieve desired performance and emission targets in an HCCI engine.