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The design and development of cylinder head and crankcase is the most critical activity in a new Engine program. These two components are subjected to complex and cyclic loading as a result of the interaction between fluid flow, heat transfer and mechanical loads. Apart from structural durability, bore distortions, the need of effective sealing at the head and crankcase joint has to be ensured. The physical validation of the structure requires the components to be developed and this is a long phase including the validation itself. Any modification due to failure or optimization at this stage can be a set back in meeting the deliverables within the given time lines. Physical testing does not provide any means of visualization of the flow and the structural deformation modes.

Results of Computational Fluid Dynamic (CFD) analyses of different diesel fuel injector nozzle configurations using a commercial CFD code are presented here. The emphasis of this study is on comparing cavitation models available in the commercial code with respect to their mathematical approach. One of the models is a simple single-phase model based on the Barotropic equation of state, while the other model is a two-phase model based on the bubble dynamic considerations. Results are compared for various 3-D diesel injector nozzles using the two cavitation-modeling approaches. Simulation results are observed to substantiate some of the experimentally established facts like; nozzle efficiency improvements by using techniques like rounded orifice inlets and conical orifices. Also, simulation results agree well with the experimental results. Spray characteristics are predicted based on a primary breakup model.

In diesel injector nozzles, the shape of the orifice entrance and the sac-volume play a significant role in determining the orifice internal flow characteristics and the subsequent spray formation process. The sac-volume of the injector nozzle determines injection characteristics like injection rate shape and discharge coefficients. The sac-volume is also important from emissions point of view, in that it controls the amount of Un-Burnt Hydrocarbons (UBHC). This paper demonstrates the use of commercial dynamic and computational fluid dynamics (CFD) programs in predicting the flow characteristics of various nozzle orifice and sac-volume configurations. Three single orifice nozzle tips with varying sac configurations and orifice entrance shapes are studied. Transient simulations are carried out in order to compare the injection rates, discharge coefficients and internal flow characteristics for the nozzle tips. The simulation results are compared with experimental results.