Numercal Study On Secondary Flow Control Of The Low-aspect Ratio Gas Turbine

As the main power machinery in the aerospace and power generation, Gasturbine and steam turbines play the most important role, turbine is the main part ofthese kinds of turbomachinery, turbine efficiency affects the performance of the gasturbine and steam turbine directly. For further improving turbine efficiency shouldfurther research the energy loss mechanism of turbine passage. Turbine cascade lossmainly consists of three parts: profile loss, secondary flow loss and leakage losse,there are various differences of loss in the proportion of different turbine cascade.Generally considered: secondary flow loss>leakage loss> profile loss. Therefore,effective control of the secondary flow loss can improve turbine efficiency.This paper do the research about secondary flow control technology on a gasturbine turboshaft engine by numerical methods, design the guide vane of the firststage of the gas turbine by the bowed-blade theory, and analyse the influence ofbowed-blade under condition of low aspect ratio air cooling blade with complexcooling structures. The results show: positive bowed-blade can reduce the vane’saerodynamic loss by reducing the loss of endwall, however, the bowed-blade greatimpacts on temperature distribution on the blade surface, resulting in decreasedcooling effect, we should joint consideration of both bowed-blade design and filmcooling.The turbine rotor in the first stage of a gas turbine was used as thenon-axisymmetric endwall baseline. Analyze the effect on the rotor aerodynamicperformance of non-axisymmetric endwall, and to explore the physical mechanismof non-axisymmetric endwall improving secondary flow. The results show: Effectsof non-axisymmetric endwall geometric modeling is greater than the magnitude ofthe position, design non-axisymmetric endwall need to be fully integrated flow fieldcharacteristics. The Bezier modeling method can get rich geometric forms, showmore advantages than trigonometric method. Non-axisymmetric endwall caneffectively improve the flow near the lower end of the rotor blades..The second stage of a gas turbine was used as the baseline, analyze the effecton the stage aerodynamic performance of fillet, The results show: it will lead to a large deviation without considering the effect of fillet, should raise more attentionto choose fillet radius in manufacturing process of low aspect ratio blade. The filletstructure affects aerodynamic performance near the hub and shroud area, lead to theincrease boundary layer loss and trailing loss.