Diesel Injector Fuel Injector 0445120061 Bosch for Man TGA TGS TGX 10.5L D2066

Dynamic cavitation inside a high performance diesel injector – an experimental and CFD investigation （part 2）

In CFD simulation, resolving large scale turbulent structures using Large Eddy Simulation (LES) based models shows transient modelling benefit over RANS simulations [3] [4] [5]. The serious disadvantage of LES based CFD in an industrial environment is the huge computing resource required,of the order of several hundred dedicated cores. Without such a resource, the run time for a single case can take months, making serious investigations impossible in a sensible time frame.

Significant developments have been made within CFD modelling which attempt to combine the benefits of both LES and RANS turbulence modelling [6]. These models are often termed hybrid models and give greater potential for LES to be utilised within an industrial environment.

A hybrid LES-RANS CFD model, using a mixture multi-phase method for cavitation was created to simulate the performance of the control orifice. Turbulence modelling using a hybrid LES-RANS method allows significant computational gains over full LES, especially in the high Reynolds number (Re) wall-bounded flow geometries within a diesel injector.

2. Experimental Work

Transparent models were created of hydraulic control parts from within a diesel injector, including a high pressure control orifice, between the needle top and control valve. Due to the small scale of real injectors the model was created at 40 times real-size, as it has been shown in previous studies that orifice flow performance is reasonably independent of scale [1]. This increased scale allowed much greater ease of visualisation using a high speed camera, a Vision Research Phantom V1210. Such a camera with appropriate lighting captures detail of the flow not visible to the human eye, and allows the hydraulic behaviour to be tracked via the cavitation process.