The Effect of EGR Ratios and Ambient Temperatures on Diesel Combustion Characteristics in Constant Volume Combustion Chamber

The objective of this experimental work is to evaluate the effect of simulated exhaust gas recirculation (EGR) ratio and ambient temperature conditions on diesel combustion characteristics in a constant volume combustion chamber (CVCC). The combustion pressure in CVCC of diesel fuel was determined by a piezoelectric transducer sensor under various conditions of ambient oxygen concentrations (21%, 15%, 10%), which are equivalent to EGR ratios on diesel engine in combination with three ambient temperature conditions (800 K, 1000 K, 1200 K) at constant fuel injection pressure of 1000 bar. The pre-combustion technique was applied to the CVCC to generate an ambient compression condition similar to the diesel engine. The heat release rate, and ignition delay seen from the diesel combustion characteristics, were analyzed based on the result of the recording combustion pressure. The results indicated that the heat release rate curves dropped dramatically, as well as longer ignition delay and combustion duration corresponding to lower oxygen concentration conditions owing to the dilution effect, simultaneously, also influenced by lower ambient temperatures. Furthermore, the impact on the combustion characteristics of a high EGR ratio (10% oxygen concentration) is clearly greater than that of a low ambient temperature condition (800 K).