Numerical Investigation of the Impact of Fuel Flow Rate on Combustion in a Heavy-Duty Diesel Engine with a Multi-Row Nozzle Injector

Diesel engines are one of the most popular combustion systems used in different types of heavy-duty applications because of higher efficiencies compared to the spark ignition engines. Combustion phasing and the rate of heat release in diesel engines are controlled by the rate at which the fuel is injected into the combustion chamber near top dead center. In this work, computational fluid dynamics (CFD) was employed to simulate the combustion behavior of a heavy-duty diesel engine equipped with a 16-hole injector, in which the nozzles were arranged in two individual rows. The two rows of nozzles have differential flow rate due to the geometrical construction of the injector. Combustion and performance characteristics of the engine were compared with and without considering the differential flow rate of the nozzle rows at a range of injection timing values. The rate of injection of the two nozzle rows was obtained from a combination of in-nozzle flow simulations and constant volume chamber simulations. The engine operates at a speed of 1000 rev/min, and at a compression ratio of 20.5. KH-RT model was used to model the spray break up, while the finite rate chemistry approach was used to model combustion. Simulation results were also compared with experimental results to analyze the impact of the differential flow rate of the two nozzle rows. The developed CFD methodology was found to capture combustion and performance trends very well and shed light on the importance to take injector nozzle geometry details into account.