Research On Flow Control Methods Of Turbomachinery Based On Honeycomb Seal And Synthetic Jet Technology

Turbomachineries such as steam turbine, compressor and so on are very important equipments in industry such as petrochemical, power, metallurgy etc. As the development of turbomachinery with high-power and high-speed, it is an effective method to improve its efficiency by using advanced seal structure and decreasing seal clearance; but the problem of fluid-excited vibration appears when the seal clearance is too small. It is a fluid-structure coupling problem in essence, and the feasible method to solve this problem is to find out the flow field characteristics and to bring flow control into effect. This dissertation includes contents about how to decrease leakage flow rate and solve the problem of fluid-excited vibration as blow:(1) A piezoelectric actuator of synthetic jet is designed, and the main factors which influence jet velocity are analyzed; experiments and numerical calculations are taken to analyze the influence of synthetic jet on blade vibration. The results show that synthetic jet and general jet have the same rule of influence; when the exit is located around blade tip, the blade vibration amplitude is to increase as air-blowing, but decrease as air-bleeding.(2) Leakage flow rate of smooth seal, serrate seal and honeycomb seal is calculated, and the main factors which influence the leakage characteristics are analyzed. The results shows that honeycomb seals have the least leakage flow rate; this is because that since the leakage flow is divided into small vortex flows by the specific hexagon structure of honeycomb seal, the energy of gas can be transferred into heat energy more efficiently which leads to decrease the leakage flow rate; there exists loop flow in the labyrinth seal which weakens the energy translation, the leakage flow rate is more; the least leakage flow rate can be gained by choosing right honeycomb size and depth.(3) The problem of self-excited vibration by seals is calculated, and the main factors which influence the blade vibration amplitudes are analyzed. The results show that the energy of fluid round blade tip is an important factor which inducing blade vibration; since the damp effect of honeycomb seals can decrease the velocity of blade tip clearance flow, kinetic energy of the fluid around the blade is decreased; a good effect of decreasing vibration can be gained when honeycomb seal coorerates with air-bleeding.