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At the initial stage of injection, the inject flow has not yet broken up and in a range of small atmosphere pressure (16∼500KPa), the tip of the inject flow always forms a shape of mushroom. And the umbrella of the mushroom is always very big and the root of it is always very thin, especially when the atmosphere pressure is relatively low (88KPa, or 100mmHg) (1)(2). These phenomena are not known popularly and the reason of mushroom formation is not clear. In this paper, with MARS (Multi-interfaces Advection and Reconstruction Solver) method (3)(4)(5)for simulating free surface, analysis of inject flow is practiced. The phenomena are reproduced and the reason is cleared that the formation of the mushroom is induced by the momentum exchange between the very high speed fuel flow and the very complex air flow.

Heat transfer plays an important role in the conceptual and detail design of cooling system of modern DI engine and has considerable influence over their operational performance and durability. The consequential demand for higher possible heat transfer rates has lead to the very promising concept of providing for a controlled transition from pure single-phase convection to subcooled boiling flow in some high thermal load regions. In order to achieve controlled boiling over a wide range of operation conditions, the detailed flow and heat transfer analysis is essential. CFD simulation incorporating the boiling model is an effective approach for such analysis. Four different boiling heat transfer models are proposed and developed within CFD framework, two based on Division Description Method (DDM), and another two based on Superposition Method (SM).