A new technique for controlling the tip leakage flow of micro turbine is presented.It uses backward vortex generators（BVGs）to control and reduce the tip leakage flow.The gas is driven by the pressure difference between pressure surface and blade tip,so it flows into BVGs from the pressure side of blade and flows out from the blade tip with high speed in the inverse-direction of leakage flow.Numerical simulations of typical turbine cascade in millimeter scale with and without BVGs are performed.The influence of BVGs on the flow fields and the performance of cascade is analyzed.The results show that the mass of leakage flow decreases by 2.8% and the circumferential load increases by 7.7% under typical entrance condition.Moreover,compared with the case without BVGs,the turbine efficiency grows about 1.2 % in case with BVGs.
Micro-turbine engine has no enough space for measuring impeller characteristics,so the design and the construction of a new test facility of micro-turbo-machinery are presented for micro-centrifugal compressors and radial turbines.The facility is used for the full speed compressor test and the long duration hot turbine test.To rapidly adjust the testing condition,all regulations of the operating state are automatically completed by the control system.The facility is also used for testing the impeller performance with a series of diameter from 55 mm to 180 mm as a result of the modular design.A thermal protection system is designed to avoid the heat distortion caused by the high turbine inlet temperature over 1 100 K and provide a proper experimental environment for the electronic components.A photoelectric torque transducer with the accuracy of 1% is designed to measure the torque of rigid shaft at a high speed of 125 000 r/min.The designing techniques for micro-turbo-machineries are verified by the impeller testing of the facility.
