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Gas cavitation has significant influence on oil jet pump in lubrication system of turbo machinery. This study provides a novel approach for identifying gas cavitation in oil jet pump. Such an approach accounts for the physical process of gas cavitation and its effect on the performance of oil jet pump. The performance of oil jet pump under variable working conditions is systematically measured and quantified from experiment and numerical simulation results. Based on the frequency characteristics of cavitation process and its action mechanism, a novel approach for the identification of gas cavitation is provided. Results shown that gas cavitation emerges at =1.68 and fades away at =1.31 with dissolve air content =110ppm in lubrication oil. Here, the dissolved air content in lubrication oil is 6.3 times larger than that in water, and the oil jet pump is more prone to suffer from cavitation than water jet pump by 16%. This study promotes a deeper understanding on the mechanics of gas cavitation affects fluid machinery in lubrication system.

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The gradient porous materials (GPMs)-filled pipe structure has been proved to be effective in improving the heat transfer ability and reducing pressure drop of fluid. A GPMs-filled pipe structure in which radial pore-size gradient increased nonlinearly has been proposed. The field synergy theory and tradeoff analysis on the efficiency of integrated heat transfer has been accomplished based on performance evaluation criteria (PEC). It was found that the ability of heat transfer was enhanced considerably, based on the pipe structure, in which the pore-size of porous materials increased as a parabolic opening up. The flow resistance was the lowest and the integrated heat transfer performance was the highest when radial pore-size gradient increasing as a parabolic opening down.

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