Simulation and Experimental Research on Fuel Spray Characteristics of a Self-pressurized Injector

自增压式喷油器的燃油喷雾特性仿真及试验研究

As a miniaturized direct injection(DI)solution,a self-pressurized injector is of great significance for small aviation piston engines,such as spark-ignited two-stroke heavy-fuel engines.The spray characteristics of DI injectors are an important application prerequisite.In this paper,the computational fluid dynamics(CFD)software AVL Fire is employed to study the spray characteristics.Two types of spray models are established based on the Han Sheet model and the KH-RT model,and simulation works are carried out according to two types of spray tests in the literature.The comparison results show that in the constant volume bomb test,the spray patterns obtained by simulation under the two sets of environmental pressures are similar to those in the experiment,and the simulation spray using the KH-RT model can fit the spray contraction of the near nozzle field and the vortex of the far nozzle field better.In the tube test,the spray patterns obtained by simulation under the five sets of flow velocity are similar to those in the experiment,and the simulation spray using the KH-RT model can fit the spray expansion and the vortex of the far nozzle field better.The RP-3 kerosene spray characteristics of the self-pressurized injector are also experimentally studied,and the results demonstrate that due to the higher viscosity of kerosene,the spray shrinks more easily,resulting in a smaller spray cone angle and larger penetration.Therefore,changes in environmental pressure have greater impact on the kerosene spray pattern.

自增压式喷油器作为一种小型化的直接喷射方案,对于以点燃式二冲程重油发动机为典型的小型航空活塞发动机具有重要意义。直喷喷油器的喷雾特性是一个重要的应用先决条件。本文采用计算流体动力学软件AVLFire对其喷雾特性进行研究。在HanSheet和KH‑RT两种破碎模型的基础上分别建立了两种喷雾模型,并根据文献中的两种喷雾试验条件进行了模拟工作。对比结果表明,在定容弹试验中,两组环境压力下模拟得到的喷雾形态与试验相近,其中采用KH‑RT模型模拟的喷雾可以更好地拟合喷雾在近场收缩现象以及远场的涡环现象。在管道试验中,5组流场流速下模拟得到的喷雾形态与试验相近,其中采用KH‑RT模型模拟的喷雾可以更好地拟合喷雾的扩张现象以及远场的涡环现象。本文还试验研究了自增压式喷油器应用RP‑3航空煤油的喷雾特性。试验结果表明,由于煤油粘度较高,中空锥形喷雾易收缩,导致喷雾锥角减小,贯穿距离增大大。因而,环境压力的变化对煤油喷雾形态的影响更大。