Experimental And Numerical Investigation On Tip Clearance Leakage Flow In Engine Cooling Fan

The engine cooling fun is one of the key components of engine cooling system, the performance improvement of which can increase the vehicle stability and reliabilityperformance, as well as decrease the energy consumption and the noise. The leakage flow behavior in the blade tip clearance impacts significantly the aerodynamic performance, work efficiency and vehicle smoothness, also becomes the main noise sources of the engine cooling fun.To further improve the work performance of the engine cooling fun, the 3-D complex flow characteristics in the area of blade tip clearancemust be studied detailedly. In order to comprehend the flow mechanism, the flow behavior in the blade tip clearance under the different clearance height, engine speed and the flow structureof clearance were detailed studied by the experimental and numerical approached, respectively. These resultsenriched the understanding to the tip clearance flow phenomena of the engine cooling fun, moreover confirmed the size and structure of the tip, as well as effectively reduced the tip clearance leakage loss, thus enhance the performance of the engine cooling fun, moreover helpful for further engine cooling fun design.On account of the series of problems such as the observably difference of the work pressure and geometry structure in the area of tip clearance between the engine cooling fun with the turbomachinery as compressor, turbine or axial pump, the unclear of the tip clearance flow mechanism, the lack of enough experimental data, the experimental setup of the tip clearance leakage flow for the engine cooling fun is developed, which including of the test model, power driven system, control system, measurement and data acquisition system, flow visualization system. Anaerodynamic performance solution is proposed for the tip clearance flow of the engine cooling fun, so that the characterization method is solved.On the basis of the test scheme, to acquire the air aerodynamic performance curve, the performance of two different kinds of the engine cooling funs with three tip clearance heights were studied based on the fun aerodynamic performance test platform. The key point of this study was analyzing the effects of fun guide ring on the engine cooling fun. After that, the influence investigation of changing the clearance area flow structure to suppress the tip leakage flow on the fun performance was conducted. On the designed work condition, combing the performance curve, the tip leakage flow characteristics was investigated experimentally by changing the work pressure, rotor speed and geometry structure. Moreover, the leakagevortex flow track in the tip clearance areawas measured under three different structures by using the flow visualization test.Accounting the detailed flow condition in the test is unavailable. Therefore, the numerical simulation is adopted for the tip clearance flow in the engine cooling fun using the STAR-CD software. Compared with the experimental results, the accuracy of the simulation is verified. Further analyze the reasons of the leakage reduction under the condition of the lower pressure and higher rotational speed, and the influence of the pressure difference and viscosity force on the leakage flow characteristics. Moreover, the flow mechanism of the engine cooling fun is illuminated.For the problem of the established leakage flow model cannot completely reflect the detailed flow mechanism, the more kinetic energy load effect is considered based on the results of the experiment and numerical simulation. After that, the quantitative expression between the leakage flow characteristics and tip clearance structureis inferred, and the theoretical model is modified, and then the mathematical calculation model which can analyze the flow and heat transfer mechanism in the engine cooling fun is put forward. So thatby evaluating the leakage rate in the tip clearance we can predict the leakage flow loss.