Performance, emission and combustion characteristic of a multicylinder DI diesel engine running on diesel-ethanol-biodiesel blends of high ethanol content

Highlights: → Diesel-ethanol-biodiesel blends of high ethanol content are tested for a Multicylinder DI diesel engine. → Brake specific fuel consumption is increased but the brake thermal efficiency is improved for high ethanol content blends. → Combustion process of high ethanol content blend is delayed at low loads but approached to the diesel fuel at high loads. → Smoke reduced remarkably at high loads for steady state but no benefit is observed on peak smoke during free acceleration. → NO emission variation depends on operating conditions while CO emissions drastically increased at low loads. -- Abstract: Feasibility of using high percentage of ethanol in diesel-ethanol blends, with biodiesel as a co-solvent and properties enhancer has been investigated. The blends tested are D70/E20/B10 (blend A), D50/E30/B20 (blend B) D50/E40/B10 (blend C), and Diesel (D100). The blends are prepared to get maximum percentage of oxygen content but keeping important properties such as density, viscosity and Cetane index within acceptable limits. Experiments are conducted on a multicylinder, DI diesel engine, whose original injection timing was 13o CA BTDC. The engine did not run on blends B and C at this injection timing and it was required to advance timing to 18o and 21o CA BTDC to enable the use of blends B and C respectively. However advancing injection timing almost doubled the NO emissions and increased peak firing pressure. The P-θ and net heat release diagrams shows that the combustion process of these blends delayed at low loads but approaches to the diesel fuel at high loads. The comparison of blend results with baseline diesel showed that brake specific fuel consumption increased considerably, thermal efficiency improved slightly, smoke opacity reduced remarkably at high loads. NO variation depends on operating conditions while CO emissions drastically increased at low loads. Blend B which replaced 50% diesel and having oxygen content up to 12.21% by weight has given satisfactory performance for steady state running mode up to 1600 RPM however, it does not showed any benefit on peak smoke emission during free acceleration test.