Reaearch On Effects Of Abnormal Stagger Angle And Variable-camber Blade On Performance Of Compressor

Variable inlet guide vanes and variable stator vanes are one of the methods that modulate performance and prevent compressor surge methods.However,jammed modulate mechanism and the manufacturing error can cause stagger angle of some blade to be abnormal.Abnormal stagger angle causes blade passage to be blocked.It has great effects on the flow of the blade passage and adjacent blade passage.The flow of the blade passage and adjacent blade passage loses periodity and they have effect on each other,then it causes boundary layer separation and vortex shedding.Boundary layer separation and vortex shedding induce fluctuated unsteady force.The unsteady force fluctuation may cause strong vibration;it even brings about flutter and high cycle fatigue damage.Therefore,investigation the abnormal stagger angle of cascade and compressor is of significant importance to the vibration reduction and fault diagnosis.On the other hand,if stagger angle of variable inlet guide vanes modulates normally but too big,the incidence angle will be too high.Due to high incidence angle,inlet flow deteriorates and loss coefficient increases,then the performance of compressor decreases.Variable-camber inlet guide vane(VIGV)are thereby introduced to improve compressor performance.VIGV can change outlet flow angle and improve flow performance without changing axial inlet flow condition.Firstly,the prediction of abnormal cascade stagger angle is compared with experimental results.Secondly,the flow of compressor is simulated by NUMECA when the stagger angle of variable inlet guide vanes is abnormal.Thirdly,this research analyzes flow of variable camber cascade at different camber and positions of modulating camber.Lastly,the flow of 1.5 stages compressor is analyzed at different camber of VIGV.The researches provide technical reserves for failure diagnosis and high performance of axial flow compressor design.Firstly,it is found by numerical simulation and experiment that when stagger angle of cascade is abnormal.Boundary layer separates on the suction surface with the abnormal stagger angle increasing when the stagger abnormal angle is positive and incidence angle is zero.And shedding frequency of separated vortex increases with the abnormal stagger angle increasing;but frequency of trailing edge vortex decreases with the abnormal stagger angle increasing.Aerodynamic force fluctuation increases and then decreases with the abnormal stagger angle increasing.But aerodynamic force fluctuation increases dramatically and then decreases dramatically with the abnormal stagger angle increasing.While stagger angle is abnormal and incidence angle is positive,boundary layer separated seriously,and shedding frequency of separated vortex is small,but aerodynamic force fluctuation is big.Boundary layer separation is not serious and aerodynamic force fluctuation is small when incidence angle is negative.Because separated vortex and shedding vortex of trailing edge have effect on the flow of cascade,the periodic of aerodynamic force fluctuation is not obvious.Secondly,it researches the 1.5 stages compressor when stagger angle of some variable inlet guide vane is abnormal.It has less effect on the flow of compressor when abnormal stagger angle is small,but the efficiency and total pressure decreases obviously when abnormal stagger angle is big.By analyzing the near stall point,It is found when stagger angle is abnormal the flow of adjacent two passages are affected.And the abnormal stagger angle has great effect on the flow of rotor and stator’s hub;the boundary layer of rotor and stator become thick near trailing edge,which it causes loss.Thirdly,the flow and performance of variable-camber cascade is analyzed in different cambers and different positions of camber modulator.Compared with fixed camber blade,variable camber cascade can reduce loss coefficient.Especially,variable camber cascade can produce big flow turning angle and reduce loss coefficient.Flow turning angle become small gradually when position of camber modulator moves from leading edge to trailing edge.In other words,performance of changing outlet flow become more and more strong with position of camber modulator moving to leading edge.The flow parameter fluctuates at position of camber modulation;but it has less effect on loss coefficient.Considering cascade strength,the best position of camber modulation is at the about 25% chord from leading edge.Lastly,it researches on the flow and performance of 1.5 stages compressor by numerical simulation with different variable-camber inlet guide vanes.Total pressure ratio and stable work range of compressor is small when rotation speed is off design and the camber of VIGV is positive.The performance curve moves right and total pressure ratio become big with camber of VIGV increasing when the camber of VIGV is negative.And the stability margin is wide when camber of VIGV is negative.Especially,the flow is improved obviously and passage vortex becomes small when camber of VIGV is negative and the condition is near stall point.In summary,it can improve the performance of compressor through variable-camber inlet guide vanes.