Performance and emissions of hexanol-biodiesel fuelled RCCI engine with double injection strategies

In the present work, an attempt has been made to operate a low-temperature reactivity controlled compression ignition (RCCI) engine using fuel produced from agro/food industry waste. Biodiesel produced from residual cooking oil (RCOB) and n-hexanol has been used as high reactivity fuel (HRF) and low reactivity fuel (LRF) respectively, in a modified diesel engine. The engine was operated at mid-load and 1500 rpm with RCOB injected in-cylinder at higher injection pressures (Pinj) of 400–600 bar whereas hexanol was injected into the inlet manifold at a lower Pinj of 3 bar. The proportion of Hexanol to RCOB was varied from 20% to 50%. Two injection pulses per cycle were used for injection of RCOB and the injection timing, duration, and fuel quantity were varied whereas hexanol injection was maintained at 355° bTDC. The injection parameters, along with exhaust gas recirculation (EGR) were optimized for the lowest smoke and NO emissions. It was observed that smoke and NO emissions reduced with late main injection, whereas smoke increased and NO reduced with advanced pilot injection. The test engine was operated at these optimized conditions and the combustion and emission data were collected and compared to that of a single injection of HRF. A maximum reduction in NO emissions by 96% and smoke emission by 80% were observed with 25% EGR. The increase of 1% in indicated thermal efficiency is an added benefit.