Optimization of Fuel Injection Timing and Pressure in CI Engines Using Waste Cooking Oil Biodiesel with Response Surface Methodology

The global automotive industry is under mounting pressure to adopt highly efficient, low-emission engine technologies due to stringent regulations and increasing environmental awareness. In response, researchers are exploring alternative fuels, such as biodiesel, to enhance energy independence and reduce emissions. Waste cooking oil (WCO) is a particularly promising biodiesel feedstock as it addresses the food-versus-fuel debate, provides a waste management solution, and is widely available. Many countries, both developed and developing, are actively encouraging biodiesel production from WCO. This research looks at a water-cooled farm engine with one cylinder and four strokes that uses WCO instead of diesel. Using diesel and WCO at conventional injection times and pressures, preliminary testing established baseline performance. The engine was then sent through its paces with different fuel pressures (200, 350, and 500 bar) and injection timings (23°, 25°, and 27° crank angle). Experimental results revealed that variations in FIT and FIP with WCO biodiesel significantly improved engine performance. Injection pressure of 350 bar with advanced injection time of 27° CA resulted in the greatest Brake thermal efficiency (BTE) of 31.18%. Compared to a FIP of 350 bar and FIT of 23° CA, BTE increased by 2.93% and 12.21% at FIPs of 200 bar and 500 bar, respectively, with the same FIT at maximum load. Hydrocarbon (HC) emissions were reduced by 1.29% and 6.5% at a FIP of 350 bar and 200 bar, respectively, compared to 500 bar, all with a FIT of 27° CA at maximum load. Carbon monoxide (CO) emissions also showed significant reductions of 12.2% and 5.6% at FIPs of 350 bar and 500 bar, respectively, compared to 200 bar with the same FIT at maximum load. However, nitrogen oxide (NOx) emissions increased with both advanced FIT and higher FIP under maximum load conditions. Smoke emissions decreased by 2.14% and 20.27% at FIPs of 350 bar and 500 bar, respectively, compared to 200 bar, all at a FIT of 27° CA. These findings highlight the potential of optimizing FIT and FIP to enhance performance and reduce emissions when using WCO biodiesel.