Presently numerical simulation of separator is based on the assumption that all the droplets can be separated once they impinge the wall. However, large oil droplets may splash into small particles, which result in lower separation efficiency. A modified simulation model is presented in this paper to model the impact behavior of oil droplet. Some semi-empirical computational models are introduced to calculate the number and diameters of the secondary droplets. Then, the performance of a typical air/oil separator is predicted, including the separation efficiency and the minimum diameter. Results show that about the efficiency may reduce 1~2% due to the splash phenomena. While, no obvious difference is observed.
For aero-engines, high-altitude valve is a key component, which is important to the high-altitude performance of ventilation system. However, theoretical researches or experimental tests of high-altitude valve are rare. To define whether the high-altitude valve can work normally during the whole flight envelope and to offer relational information for the improve design, this article focuses on the operation process and characteristic computation of high-altitude valve. Based on operational principle and structural analysis, using mechanics method, the high-altitude characteristic computation of high-altitude valve was done and the flight height where the valve closes was identified. In the same way, we analysed the static characteristic, getting the inner-cavity pressure in high-altitude flying state. Compared with the experimental results, the analytical methods and calculated values are validated to be accurate. The characteristic curves obtained can be directly used in the check and acceptance or further design of high-altitude valve.
A calculate method based on ε-NTU model for heat transfer characteristics of shell-tube fuel-cooled heat exchanger of aero-engine lubrication system was built. The heat convection coefficient was obtained by a dimensionless curve (Re~StPr2/3), which was detailed introduced as well. A case study was executed at last. The absolute error of the outlet lubrication of the tube side and the shell side between the value of calculation and experiment was less than ±10°C, and the relative error was less than 6.5%. The absolute error of the heat transferred between calculation and experiment was less than ±0.9kW, and the relative error was less than 7.4%. It indicates that the mothod is available for the investigation of heat transfer characteristics of shell-tube fuel-cooled heat exchanger.
With reference to cavitation phenomena in the feed-oil pump of aero-engine, a numerical method is presented in this paper to analyze operating performance of pump. Local re-meshing model is introduced to update the computational mesh when the gear teeth in mesh depart each other. Also, the full cavitation model is applied to simulate the flow field, the mass transfer between oil and vapor at low pressure producing region. The performance of a typical feed-oil pump is predicted to evaluate the altitude influence. Results show that more oil vapor is produced at higher altitude. Meanwhile, the leakage mass is mainly depended on the pressure drop.
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