Experimental And Numerical Study On Variable Inlet Guiding Vane Trailing Edge Blowing

In order to ensure the performance of most industrial centrifugal compressors under variable working conditions,the variable inlet guiding vane is often installed.When the variable inlet guiding vane is at a large opening,it will generate a large attacking angle,causing pressure loss that cannot be ignored.At the same time,the wake generated by the variable inlet guiding vane will increase the aerodynamic load of the impeller,decrease the aerodynamic performance of the compressor and reduce the efficiency.Via active flow control technology of trailing edge blowing,the velocity loss and pressure loss in the wake can effectively be reduced.So that,aerodynamic loading of the downstream blade,along with the separation of the boundary layer and the loss caused by the mixing of the wake and the main flow will be reduced.Therefore,it is of great significance to study the flow in the wake region of centrifugal compressors with variable inlet guiding vanes with different openings to reduce loss and improve efficiency.In this paper,the annular cascade experiment and numerical study are combined to study the aerodynamic characteristics of variable inlet guiding vanes with different opening and different sections under different blowing conditions.In terms of experiment,according to the similarity theory,the variable inlet guiding vanes with double slits and without slits were designed and processed.Based on the large-flow transonic cascade wind tunnel laboratory in Dalian University of Technology,an experimental bench for blowing air at the trailing edge of the full-circle variable inlet guiding vanes was designed and built.And a high-precision test system is used for experimental measurement.Moreover,handling method of seven-hole probe is improved.The results show that the flow field in front of the blades is uniform and the turbulivity is low.Under unblown condition,with the increase of opening,the wake area of the flow field behind the guide cascade deviates along the circumferential direction,and the pressure loss and velocity loss in the wake area can also be clearly observed.Under blowing condition,one of the test sections behind the blades was taken as an example for the main analysis,and the same rule was verified in the other two cases: under the condition of zero opening,the flow pattern of the w-shaped wake region was obtained;under the condition of 10 opening and 20 opening,the flow pattern of the inverted z-shaped wake region was obtained.In the numerical simulation part,by comparing the experimental results with the numerical simulation results,it is found that the two are in good agreement,which verifies the reliability of the experimental results.In addition,the flow field behind the variable opening gate of the variable inlet guiding vanes under the condition of no blowing air is analyzed,and the internal flow details such as throttling phenomenon and tip vortex are observed.The formation mechanism of non-momentum-deficit wake under blowing state is explained.On this basis,through the comparison of central single-slit blowing,asymmetric single-slit blowing and double-slit blowing,it is found that different blowing methods can achieve the form of wake without momentum loss,but the distribution of wake flow field and blowing effect are greatly different,and the blowing amount required by each blowing method is also different.