Effect of Fuel Temperature on the Performance of a Heavy-Duty Diesel Injector Operating with Gasoline

In this last decade, non-destructive X-ray measurement techniques have provided unique insights into the internal surface and flow characteristics of automotive injectors. This has in turn contributed to enhancing the accuracy of Computational Fluid Dynamics (CFD) models of these critical injection system components. By employing realistic injector geometries in CFD simulations, designers and modelers have identified ways to modify the injectors’ design to improve their performance. In recent work, the authors investigated the occurrence of cavitation in a heavy-duty multi-hole diesel injector operating with a high-volatility gasoline-like fuel for gasoline compression ignition applications. They proposed a comprehensive numerical study in which the original diesel injector design would be modified with the goal of suppressing the in-nozzle cavitation that occurs when gasoline fuels are used. The analysis was carried out at several levels of injection pressure (between 1000 and 2500 bar) and it was found that the new designs could almost completely prevent cavitation occurrence up to 1500 bar. In this study, the best candidate from the previous work was evaluated numerically by varying the fuel’s injection temperature between 20 °C (293 K) and 120 °C (393 K), for a total of four temperature levels. All simulations were performed using an unsteady RANS formulation coupled with the Individual Species Solution method. Relatively short, transient injections (<1.0 ms) with 1500 bar injection pressure and 100 bar ambient pressure were simulated to replicate one of the most demanding operating conditions expected in the engine. The performance of the injector was assessed in terms of mass flow rate and fuel vapor volume fraction within the orifices for both the realistic X-ray geometry and the improved one. This study highlighted the benefit offered by the new injector design in terms of in-nozzle cavitation suppression and helped to quantify the effect of fuel temperature on the amount of injected fuel under short injection duration conditions.