Experimental investigation of performance, emission, and combustion characteristics of a variable compression ratio engine using waste cooking vegetable oils blended with diesel

The availability of crude oil and petroleum products has become scarce and costly over the years leading to a stiff rise in engine fuel. Due to the depletion of conventional fuels; alternative fuels are gaining importance in recent times and Waste Cooking Vegetable Oils (WCVOs) are the viable option for the same. The present study highlights the performance, emission, and combustion characteristics of the Variable Compression Ratio (VCR) engine using three varieties of WCVOs (Ground Nut (GDN), Palm (PM), and Sunflower (SF)). Their inferior fuel features (density, viscosity, calorific value, etc.) are enhanced by blending 30 % of these oils with 70 % Diesel. The experiments are then conducted in the VCR engine using these blended oils under varying loading conditions (0-8 N) and at a constant speed of 1500 (RPM) with a compression ratio (18:1). It is seen that a single blend of Palm oil (PM) increases the engine Brake Thermal Efficiency (BTE) by 5 % in comparison to Diesel and other blended fuels (GDN, SF) owing to its lower calorific value and greater viscosity. The engine Brake Specific Fuel Consumption (BSFC) decreases with the increase in load and the lower loads reduce the BSFC for WCVOs by 9-15 % compared to Diesel. Engine emissions like Carbon Monoxide (CO), Nitrogen Oxide (NOx), and Hydrocarbons (HC) are also reduced significantly (by 12-15 %) using these blended oils compared to Diesel. The surge in both the Peak Cylinder Pressure (PCP) and Heat Release Rate (HRR) is also observed using these blended fuels, especially for Sunflower. Hence, these WCVOs are an appropriate option to advance the VCR engine performance and decrease its emissions.