| The helicopter has excellent takeoff,landing,and hovering performance as well as good low-altitude flight capability.It is an important equipment for post-disaster rescue,material transportation,combat escort and other emergency tasks in plateaus,desert,and coastal areas.The turboshaft engine is the core power plant of the helicopter.The sand particles in the external environment cause erosion damage to the compressor blades under the combined action of the rotor downwash airflow and powerful suction force of the engine.After cumulative expansion of the damage,the structural integrity of the compressor blades is destroyed,causing unbalance fault vibration of the rotor system and further inducing non-linear vibration accidents such as blade-casing rubbing,which seriously endangers the safety of engine operation and helicopter mission execution.However,existing research is unable to accurately characterize the erosion wear mechanisms of compressor blades caused by sand particles properties.The influence of engine operating parameters such as inlet distortion and variable speed conditions on blade erosion wear under airborne conditions and maneuvering flight has not been thoroughly discussed.At the same time,the mechanism and distribution of unbalance faults in the gas generator rotor system caused by blades erosion damage are unclear.And the effects of the distributed unbalance phase and unbalance amplitude on the vibration response of the rotor system are indefinite.Therefore,a certain turboshaft engine is used as the research object in this paper.An in-depth study of erosion damage of the compressor blades and vibration characteristics of the vibration characteristics of the gas generator rotor system are conducted.This can provide theoretical guidance and data support for the unbalance fault diagnosis of turboshaft rotor system and the anti-wear protection design of blades in harsh environment.The main research contents and conclusions of this paper are as follows:(1)Based on the classical erosion wear theory,the expression of the wear rate of particles on the metal surface is derived.The experimental setup of the particle velocity test based on PIV technology and the experimental device of Ti-6Al-4V alloy erosion wear are designed and built.The motion velocity of sand particles under typical particle size and full particle size range are obtained through velocity test.Combined with the erosion wear experiments of Ti-6Al-4V alloy under different impact angles and velocities,it is found that the erosion wear of Ti-6Al-4V alloy surface caused by sand particles is a compound damage mode under the combined action of micro-cutting and extrusion deformation.The key parameters n and k of the erosion wear model related to sand velocity and target material under the typical particle size and full particle size range are determined,and the parametric study of the erosion wear theoretical model is completed.(2)Based on the parametric experimental results of erosion wear model,the finite element model of gas-solid flow of erosion wear f or the pre-1.5 stage compressor blade is established.The calculation accuracy of the finite element model is verified based on the flow field characteristics of the Rotor 37,the literature statistical data and the actual observation results of the compressor blade.The erosion wear distribution and wear rate concentration of rotor blades and stator blades of compressor blade are analyzed.It is found that the particles have complex motion trajectory such as direct collision,collision rebound and re-collision,and free-moving in the flow field.The erosion wear concentration area of the rotor blades and stator blades does not change with the change of the sand particle size,but there are differences in wear rate concentration value.Among them,the maximum concentration values of the wear rate caused by 177 μm sand particles on the rotor blade and stator blade is significantly increased compared with 423 μm sand particles.(3)The finite element model of the full-port compressor blades is established,and the inlet distortion parameters are set according to the engineering practice.The erosion wear characteristics of the blades under the typical inlet distortion angle are studied.It was found that the inlet distortion significantly changed the erosion wear characteristics of the blades.When the inlet distortion angle is expanded from 30° to 90°,compared with the rotor blades in the non-distortion-affected area,the wear degree of the rotor blades affected by the inlet distortion in the front position increases by 32.5% and 68.7%,respectively.The research object is further extended to the whole axial flow compressor of turboshaft engine,and the erosion wear characteristics of blades at ground idle speed,steady-state working speed,design speed and emergency state speed are analyzed and quantified.The results show that the erosion damage degree of rotor blades at the design speed is obviously higher than that at other speeds,while the degree of the blades at the emergency state speed decreases to a certain extent.(4)Based on the research conclusions of the influence of particle properties and operating parameters on blade erosion wear,the erosion damage degree of blade is further calculated.The unbalance excitation of the gas generator rotor caused by erosion damage is characterized.A dynamic model of the gas generator rotor system is constructed,and the accuracy of the modeling is verified by dynamic analysis.The whirl trajectory and unbalance vibration spectrum characteristics of the gas generator rotor system caused by blade erosion damage are analyzed.It is found that the unbalance magnitude of the 1-stage rotor blade disk and the 3-stage rotor blade disk caused by erosion damage is 2.33 times and 1.22 times that of the 2-stage rotor blade disc,respectively.The vortex trajectory of the gas generator rotor system under unbalance excitation is significantly different from the one before delivery.The vibration amplitude of the supporting position is the lowest when the unbalance phase difference caused by blade erosion damage is 0°-180°-180°,and it is the highest when the unbalance phase difference was 0°-0°-0°.At design speed,when the unbalance magnitude increases from 20 g·mm to 120 g·mm,the vibration amplitudes of the left and right sides of the supporting position increase by 97.1% and 263.2%,respectively. |
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