Effects of Throat Shape on Combustion Improvement in a Swirl-Chamber Diesel Engine with Electronically Controlled Multi Hole Injector 2023-01-1819
In-Direct Injection (IDI) system are mainly used in off-road diesel engines with output of less than 19 kW. These engines generally employ a mechanical injection system. Since it is difficult for these engines to flexibly control the injection timing and injection quantity, there are restrictions on improving fuel efficiency and emission performance.
Therefore, we have developed an electronically controlled fuel injection system that is optimal for small diesel engines. We adopted injectors used in relatively inexpensive direct-injection gasoline engines for automobiles, instead of injectors for common rail systems, which are often used in diesel engines. The adopted injector is a multi-hole nozzle, and its spray behavior is different from that of the pintle nozzle used in swirl-chamber diesel engines. In swirl-chamber diesel engines, not only the injector type, but also the shape of the throat connecting the swirl-chamber and main chamber influences the formation of the fuel-air mixture.
In this research, 3D Computational Fluid Dynamics (CFD) was used to understand fuel-air mixture formation and to optimize the shape of throat. A spray model that can express the dynamic behavior of droplets is necessary for proper spray and combustion analysis. The spray behavior from the multi-hole nozzle was measured using a constant volume chamber. The spray model was validated based on the measurement data. The optimum combustion chamber shape for fuel-air mixture formation was investigated by in-cylinder combustion analysis using the calibrated spray model. As a result, it was shown that the diffusion combustion in the main chamber can be improved by adjusting the cone angle and the area of the throat.
Citation: Fujiwara, T., Suematsu, K., Okazaki, T., Kobayashi, Y. et al., "Effects of Throat Shape on Combustion Improvement in a Swirl-Chamber Diesel Engine with Electronically Controlled Multi Hole Injector," SAE Technical Paper 2023-01-1819, 2023, https://doi.org/10.4271/2023-01-1819. Download Citation
