"Experimental Investigation on the Effect of Injection Timing and EGR on Performance and Emissions of a Compression Ignition Engine Fueled with Diesel and Blends of Waste Cooking Oil Biodiesel Start of Injection (SOI) or injection timing refers to the crank angle degree (CAD) at which the fuel injection into the combustion chamber commences, typically before Top Dead Center (bTDC) of the compression stroke. The timing of fuel injection plays a critical role in the combustion process, influencing the engine's power output, fuel economy, and emission levels. Diesel engines are widely adopted across defense, transport, power generation, and agricultural sectors due to their high efficiency, durability, and torque characteristics. However, the growing environmental concerns and the scarcity of fossil-based diesel fuels have steered research toward cleaner, renewable alternatives such as biodiesel. Biodiesel, derived from renewable feed stocks such as waste cooking oil (WCO), not only supports energy diversification but also significantly reduces carbon monoxide (CO), unburned hydrocarbons (HC), and particulate matter (PM) emissions when compared to conventional diesel (D100). The only major drawback observed is a tendency for increased nitrogen oxide (NOx) emissions due to higher oxygen content. To mitigate NOx emissions, exhaust gas recirculation (EGR) is employed effectively as an in-cylinder NOx control strategy. In this study, a single-cylinder, four-stroke direct injection diesel engine is tested using pure diesel (D100) and two biodiesel blends: WCOBD20 (20% biodiesel, 80% diesel) and WCOBD40 (40% biodiesel, 60% diesel). The experiments are carried out at a constant injection pressure of 220 bar and at three different injection timings: 21°, 23°, and 25° bTDC. EGR flow rates of 0%, 10%, and 20% are applied at part-load operation to observe their effect on NOx reduction. Engine performance metrics such as brake thermal efficiency (BTE), brake specific fuel consumption (BSFC), and brake power (BP) are measured along with emission characteristics like CO, HC, NOx, smoke opacity, and exhaust gas temperature (EGT). In addition, combustion parameters including ignition delay, peak pressure, combustion duration, and heat release rate are analyzed. The outcomes of this investigation aim to offer deeper insights into optimizing injection timing and EGR strategy for achieving cleaner combustion and better efficiency while using sustainable biodiesel-diesel blends in compression ignition engines.
Batraju et al. (Thu,) studied this question.