Research on application of asymmetrical Pre-chamber in Air-Assisted direct injection kerosene engine

Abstract

• Effects of asymmetric jet pre-chamber on combustion process of kerosene AADI engines were studied. • The simulation of jet pre-chamber schemes was conducted for combustion optimization. • Engine test on combustion comparison of different ignition schemes was performed. • The asymmetric jet pre-chamber was found to be advantageous to improve combustion performance. Aiming at the power improvement of the aviation kerosene engine caused by the mixture preparation, and slow combustion rate, this paper introduced the design and application of the asymmetric jet pre-chamber on a spark ignition piston-type aviation engine equipped with the kerosene low-pressure air-assisted direct injection (AADI) system. Simulation calculation was conducted on combustion differences between the asymmetric pre-chamber and the traditional symmetrical pre-chamber. Meanwhile, the impacts on the flame combustion duration and heat release process in the main combustion chamber, which was divided into zone A and zone B, by the different jet nozzle orifice diameters and spatial distribution angles in the asymmetric jet pre-chamber were analyzed in the paper; and engine bench tests were performed on the influence of the combustion characteristics and power performance by the asymmetric jet pre-chamber ignition scheme under different control strategies. The simulation results showed that the asymmetric pre-chamber could further improve the combustion reaction rate by 7% and the cumulative heat release rate by 17%, thereby effectively promoting the engine combustion efficiency. And an optimal orifice diameter by 2.00 mm of the two jet nozzle in the zone B existed. Compared with the spatial angle α of these two jet nozzle in zone B by 80°, the spatial angle α of 50° can further be helpful to strengthen the heat transfer between the jet flame in the pre-chamber and the mixture in the main combustion chamber. The test results showed that the asymmetric pre-chamber was beneficial to improve the engine combustion performance by 11.4% under low load and by 16.7% under heavy load conditions. The optimal combustion performance can be obtained by the asymmetric pre-chamber at the condition of λ = 0.7, which resulted in higher jet flame ignition energy and faster combustion progression at the condition of richer mixture. As a conclusion, it is benefit to increase the initial heat release and enhance heat work transfer efficiency in the main combustion chamber of the AADI aviation kerosene engine.