Авіаційно-космічна техніка та технологія (Dec 2018)
FEATURES OF HEAT TRANSFER IN THE GAS TURBINE ENGINE BEARING CHAMBER
Abstract
The issue of ensuring the thermal regime of the rotor support, which guarantees reliable operation of the power plant, is particularly important in designing oil systems of aviation gas turbine engines, as well as ground-based GTEs. The exact calculation of the heat flux from the engine to the GTE bearing chamber is necessary to determine the required oil pumping through the GTE rotor support. The complexity of the mathematical description of thermo-hydraulic processes is associated with the presence of a multiphase mixture in the bearing chamber, consisting of oil, which is applied to lubricate and cool the support elements, and the air applied to pressurize the seals. The current practice of designing oil systems is based on the experimental data and technology that has been established more than 20 years ago. The development trends of aircraft engines, aimed at reducing specific fuel consumption and harmful emissions, suggest higher loads and temperatures in the engine while reducing power take-off for reliable operation of its main systems. This adds demands for oil systems and leads to the need to improve their circuits and elements using modern methods of modeling and design, accumulated knowledge of work-flows. The article deals with the features of the heat exchange process between the walls of the bearing chamber and the multi-phase oil-air flow applying the developed three-dimensional CFD-model of the oil-air flow in the cavity of the rotor support of a gas turbine engine. The developed CFD model is verified and the results of a numerical study of thermal-hydraulic processes are presented by the example of a bearing chamber with simplified geometry applying experimental open access data. It is presented the effect of gravity and shear forces (shear stress) on the distribution of the flow and heat transfer in the bearing chamber, which is reflected in the nonuniform distribution of the oil film and the heat transfer coefficient around the circumference of the cavity. It is determined the influence of the size on oil droplets moving in the oil-air flow on the distribution of the oil film and the heat transfer coefficient in the bearing chamber
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