Design,analysis And Preliminary Experimental Study Of A Deformable Particle Separator

Particle separator is an important protection component of air intake for helicopter.It is a bifurcated duct with large curvature,which can effectively eliminate the majority of dust within the incoming flow but will inevitably increase its aerodynamic loss.A fixed geometry particle separator has to make a balance between high aerodynamic performance and high separation efficiency.In order to achieve a particle separator with high overall performance,a design method of variable geometry particle separator is proposed in this paper.Numerical simulation and preliminary experiments have been conducted.Firstly,the deformation method of particle separator with flexible and deformable bump is introduced in detail.A test model has been made and the outer contour of the flexible bump is calibrated by schlieren technique.The relationship between charge pressure and the radial deformation of bump is obtained.The calibration results show that the bump deforms continuously and the outer contour remains smooth with the charge pressure.The nonuniformity of the deformation along circumferential direction is within 0.7%,which can be ignored for analysis.Then,numerical simulations of the particle separator with calibrated contours of bump have been carried out.The baseline flow features are analyzed.It’s found that there is a local adverse pressure gradient region downstream of the throat,after that the flow accelerates to the main channel.Due to the existence of horse-shoe vortices induced by the support plate,which have detrimental effects on the circumferential uniformity.A local high and low pressure region can be found downstream of the support plates,which situates right after the plate and deviated 9~°from the centerplane of the plates,respectively.Whereas the flow in the scavenge scroll is more complicated and is dominated by a large scale vortex.Moreover,the impacts of radial deformation of bump and axial position of separator on the overall performance of the particle separator are studied.The results show that though the total pressure recovery coefficient decreases from 0.984 to 0.969 when the radial deformation of bump increases from 0 to 7.5mm,the sand separation efficiency improves greatly,especially the separation efficiency of AC sand increases from 84.17%to 89.42%,indicating the validity of the deformation method.As for the axial position of separator,it can significantly affect the aerodynamic performance of the particle separator,but has little effect on sand separation efficiency.Thus,the deformated bump is the most efficient variable geometry method.In addition,the influence of bump material,i.e.2024aluminum and rubber,on sand separation efficiency has been numerically verified.The results demonstrated that it has tiny effects,the maximum deviation of separation efficiency of C and AC sand is within 1.87%and 0.8%.Thereafter,five metal bumps with different radial deformations have been made.The related experiments have been performed,which have obtained the pressure distributions and the aerodynamic performances with radial deformations.The experimental results are consistent with that from simulation,which validates the effectiveness of the deformation method.At last,the experiments with flexible bump,which deformates continuously,have been conducted.The results show that,by adjusting the radial deformation of bump,the quality of the flow field can be continuously controlled,which verifies the feasibility of the deformation method proposed in the paper.As a result,by adjusting the radial deformation of the bump adaptively,the particle separator can balance the needs of high aerodynamic and particle separation performances under different working environments,resulting in a higher working efficiency and longer life cycle of aero-engine.