Performance Evaluation of a Low Heat Rejection Diesel Engine with Mohr Oil Based Biodiesel

Aim: Investigations were carried out to evaluate the performance of a high grade low heat rejection (LHR) diesel engine with air gap insulated piston, air gap insulated liner and ceramic coated cylinder head (ceramic coating of thickness 500 microns was done on inside portion of cylinder head] with different operating conditions (normal temperature and pre-heated temperature) of Mohr oil based bio-diesel (MOBD) with varied injection pressure and injection timing.
Study Design: Performance parameters of brake thermal efficiency, exhaust gas temperature and volumetric efficiency were determined at various values of brake mean effective pressure (BMEP).
Methodology: Exhaust emissions of smoke and oxides of nitrogen (NOx) were recorded at different values of BMEP. Combustion characteristics at peak load operation of the engine were measured with TDC (top dead centre) encoder, pressure transducer, console and special pressure-crank angle software package.
Results: Conventional engine (CE) showed deteriorated performance with biodiesel operation, while LHR engine showed improved performance at recommended injection timing and pressure of 27°bTDC (before top dead centre) and 190 bar respectively. The performance of both version of the engine improved with advanced injection timing and at higher injection pressure when compared with CE with pure diesel operation. The optimum injection timing was 31°bTDC for CE while it was 30°bTDC for LHR engine using biodiesel operation. It was also observed that peak brake thermal efficiency increased by 14%, volumetric efficiency decreased by 8%, smoke levels decreased by 6% and NOx levels increased by 47% with MOBD operation on LHR engine at its optimum injection timing, when compared with pure diesel operation on CE at 27°bTDC.