Impact of oxygenated palm-biodiesel on combustion characteristics under various levels of EGR in simulated CI-engine condition

Abstract Diesel engines, known for their high compression ratios, are extensively used in various sectors including industry, transportation, agriculture, and construction. However, they face significant challenges in meeting strict emission standards. Fossil-derived diesel fuel is cited as a major contributor to serious issues like high environmental pollution, harmful health effects, and the energy crisis. Promoting the development of high technology related to clean fuel is crucial. Exploring the impact of combining high-pressure fuel injection with low oxygen concentration as a form of recirculating part of the exhaust gas back into the engine cylinder (EGR) for oxygenated biodiesel, to enhance fuel efficiency and emission mitigation, presents a promising avenue of research. This work focuses on evaluating the impact of various EGR levels on the combustion behaviors of palm biodiesel (B100) and conventional diesel (B0) under a high fuel injection pressure of 1200 bar and a constant injection time of 2.0 ms in a constant-volume vessel. Compression ignition (CI) engine operating conditions, characterized by an in-cylinder ambient pressure of 43 bar, were investigated under three cases of volumetric oxygen concentrations simulating various EGR levels in diesel engines: no EGR (21% O 2 ), medium EGR (15% O 2 ), and heavy EGR (10% O 2 ). A piezoelectric transducer was utilized to record the combustion pressure, from which combustion characteristics were analyzed. The findings revealed that the ignition delay of B100 is shorter than that of B0 under no EGR conditions and prolongs when reducing the oxygen content to 10%. Increasing the EGR ratio leads to a significant decrease in the integral heat release, the summit of the apparent heat release rate, and peak combustion pressure for both fuel types. Nevertheless, a longer diffusion combustion phase was observed compared to conditions with higher ambient oxygen concentrations. Furthermore, the combustion characteristics of B100 are also lower than those of B0 under test conditions.