Experimental Investigation on Performance and Emission Characteristics of CI-DI VCR Engine using Biodiesels and their Blends

Abstract

The development of any nation depends on the energy availability and consumption. As per Indian scenario the fuel consumption is increasing year by year because of improved economy. The researchers and technocrats are striving hard to find the energy sources which can be a substitute for petroleum derived fuels. The biofuels are gaining importance as a substitute fuel for petroleum derived diesel fuel. Biodiesels are renewable, biodegradable, non toxic, environmental friendly fuels which could be used in present day automobiles with or without modification. The biodiesels used in the present experimental investigation are Pongamia, Jatropha and Simarouba. These biodiesel are prepared with their respective oils by transesterification method. The three biodiesels considered are mixed two at a time and in the different volume ratios i.e. 75:25, 50:50 and 25:75. The Pongamia and Jatropha are mixed in the ratio 75% Pongamia+25% Jatropha (P75+J25) and designated as M1, similarly the mixture (P50+J50) as M2, and (P25+J75) as M3 respectively. In the same way Pongamia and Simaruoba are mixed in different volume ratio and designated as M4, M5, and M6. The Jatropha and Simarouba are mixed and designated as M7, M8 and M9. These prepared mixtures are blended with diesel in different volume ratio. The B20M1 is the blend of 20% of M1 +80% of diesel fuel, similarly B40M1, B60M1, B80M1 and B100M1 which is mixture of two biodiesel. Fuel properties play an important role in the combustion, performance and emission characteristics of engines. Properties of biodiesel are within ASTM and European standards and comparable with diesel fuel. The flash and fire points are higher, having lesser heating value and higher viscosity. New correlations are developed to find the density and viscosity of mixture of two biodiesel at elevated temperatures. Using these correlations the density and viscosity of the mixture of two biodiesel can be found for any temperature and for any volume fraction of biodiesel in the blends. The mathematical correlations are established to find the density and viscosity of Simarouba biodiesel and diesel blends at different temperatures for any volume fraction of biodiesel. The mathematical correlations are also established for the density, flash point and heating values with viscosity of fuels used. The aim of the present study is to experimentally investigate the combustion, thermal performance and emission characteristics of single cylinder, four stroke, DI VCR diesel engine using the mixture of two biodiesel in blend with diesel fuel. The investigation is carried out by operating the engine at different compression ratios of 16, 17 and 18 using ii the various blends. The load on the engine is varied from zero to the rated load increasing in the interval of 20% of rated load. The combustion characteristics investigated and analysed are cylinder pressure, maximum cylinder pressure using P-V plot, net and cumulative heat release, mass fraction burned and rate of pressure rise. The thermal performance parameters evaluated are BTE, BSFC, EGT. The various exhaust emissions measured are CO, HC, NOx and Smoke intensity. The cylinder pressure increases with increase in CR and maximum at the rated load for all the blends and diesel fuel. For all the compression ratios used cylinder pressure increases with increase in load. The start of injection and combustion are advanced for the blends compared to diesel fuel. The ignition delay for the all the blends is shorter in duration compared to diesel fuel. The heat releases are lesser for blends compared to the diesel fuel at the rated load for all the CR. The MFB are higher for diesel fuel. The combustion duration increases for the blends. The rate of pressure rise is higher for the blends. The BTE increases with increase in load for the compression ratios used. The engine tests revealed that BTE is lower to a maximum of about 4% for the blends compared to diesel fuel at CR18. The blends up to 40% have comparable BTE with diesel fuel. The BSFC of biodiesel blends are increased to a maximum of about 6% compared to diesel fuel. The exhaust gas temperatures are increases with increase in load for the fuels used. The exhaust gas temperatures are lower by about 5% for the blends for the CR used. The various exhaust emissions are measured using the five gas analyser and smoke meter. The exhaust emissions increases with increase in load for the all the fuels and CR used. The CO, HC and smoke emissions are decreased to a maximum of about 45%, 50% and 15% respectively for the various blends at higher CR for the rated load compared to the diesel fuel. The NOx emissions increase for higher CR for the blends to a maximum of about 25% compared to the diesel fuel. The CO, HC and smoke emissions are increases at lower CR which may be due to lower combustion temperature. Artificial Neural Network (ANN) model is used to get the output parameters for the optimised input parameters. ANN modelling is a complex technique capable of modelling the various functions and methods. The different softwares can be used for the ANN model. The MATLAB® 2014 software is used for the analysis. The parameters predicted by ANN model are found to be quite close to experimental values with reasonable accuracy. From the experimental investigation, it is summarised that the engine can be operated at various compression ratios without problem. The mixture of two biodiesel in blend with diesel fuel can be used as an alternative fuel in VCR diesel engine. The combustion iii characteristics are reasonably comparable with diesel fuel at various compression ratios. Performance of the engine is marginally lower for the lower blends. The CO, HC and particulate emissions are decreases for the blends compared to diesel fuel whereas NOx emission increases. Based on combustion analysis, thermal performance and emission analysis, it is experienced that CR18, combination of any of the mixture, the blend B40 is a better substitute for the diesel fuel