In this study, the effects of fuel injection discharge curve and injection pressure onpower upgrade of heavy-duty diesel engine by simulation of combustion process in AVL-Fire software are discussed simultaneously. Hence, the fuel injection discharge curve is changed from semi-triangular to rectangular which is usual in common rail fuel injection system. Injection pressure with respect to amount of injected fuel and nozzle hole diameter are changed. Injection pressure is calculated by an experimental equation which is developed for heavy duty diesel engines with common rail fuel injection system. Power upgrade for 1000 and 2000 bar injection pressures are discussed. For 1000 bar injection pressure with 188 mg injected fuel and 3 mm nozzle hole diameter, power is upgraded about 19% in comparison to original state which is semi-triangular discharge curve with 139 mg injected fuel and 3 mm nozzle hole diameter, with no special change in cylinder pressure. On the other hand, both the NOX and the Soot emissions decreased about 30 and 6%, respectively. Compared with the original state, in the case of 2000 bar injection pressure, with injected fuel and nozzle diameter, 196 mg and 2.6 mm respectively, the power is upgraded about 22%, whereas cylinder pressure has been fixed, and the NOX and the Soot emissions are decreased to 36 and 20%, respectively.
Key words: Computational fluid dynamics (CFD) simulation, heavy-duty (HD) diesel engine, upgrading power, injection pressure, fuel injection discharge curve, combustion process.