The Steady Flow And Heat Transfer Characteristics Of The Contra-rotating Turbine Disc Cavity And The Thermal Stress Of The Rotating Disc

The flow and heat transfer inside the counter rotating disk cavities involve several coupled forces and are very important not only from the point of view of engineering application but also for academic value.The flow structure,heat transfer characteristics and the disks stress of the rotating disk cavity were studied by numerical calculation and experiment.The main contents of the article include: a wireless measurement laboratory bench for monitor the surface temperatures of the rotating disk is designed and constructed,and then is corrected;the surface temperatures of the rotating disk are measured at different air inflow rate,and the results are compared with the numerical results to verify the accuracy of the numerical calculation;and numerical calculations are performed to investigate the steady-state flow structure and heat transfer characteristics in the counter-rotating disks cavity system and the stress of the rotating disk,under different rotational speeds,intake air flow rate,outlet clearance size and intake position.The numerical analysis leads to the following conclusions.With the increase of the intake air flow rate,the strength of the anticlockwise swirling cell at the high radius position increases,and it gradually expands toward the low radius position,and the stagnation point continuously moves radially inward.The heat transfer coefficient of the upstream and downstream disks surfaces increase,and the temperature of the upstream and downstream disks surfaces also decreases,and the temperature on the upstream disk changes significantly.The high-stress regions of the rotating disks are distributed in the position where shaft connects with the rotating disk and the disk edge region,and the Von Sises stress of the rotating disc decreases firstly and then increases as the radius increases.With the increase of the rotating speed,the strength of the anticlockwise swirling vortex at the center of the middle disk plane-view surface increases and expands to the periphery,the clockwise vortexes of circumferential distribution are compressed;the stagnation point moves radially outward and finally moves to the peripheral shroud,while the radial velocity near the wall of the upstream disk increases.The temperature at high radius of the upstream disk surface decreases and the one of the low radius disk surface increases with the increase of the rotation speed.When the rotation speed is high,the disk surface temperature decreases as the rotation speed increases.The rotation speed change has a great influence on the thermal stress distribution of the disc rim.In the scope of this paper,the change of outlet clearance has little effect on the flow structure and heat transfer characteristicsThe inlet position determines the boundary of the high radius anticlockwise vortex cells and adjacent vortex cells.As the intake air position becomes higher,a vortex is gradually formed in the center of the disk cavity,and the radial velocity near the wall of the downstream disk reaches the largest in the initial jet-forming area.The sizes of the high radius position counterclockwise cells at the middle gap-view surface and the central counterclockwise vortex cells at the middle disk plane-view surface are determined by the centrifugal force,the radial Coriolis force and the inertial force of the intake air.The former vortex packet is formed by the angular momentum under the action of radial Coriolis force and buoyancy,while the latter is formed by the angular momentum from the peripheral shroud viscous force.The rotating disk heat transfer coefficient is mainly affected by the gas radial velocity near disk,the greater the absolute value of radial velocity,the higher the local heat transfer coefficient.The disk surface temperature of the rotating disk is related to the heat transfer coefficient of the whole disk,and the distribution of the disk surface temperature is affected by the intake position.Aerodynamic stress and centrifugal stress are two and one orders of magnitude lower than thermal stress respectively in the case of the middle and low rotation speeds.So the overall stress level is dominated by thermal stress.With the increase of the air intake radius,the cooling effect of the downstream disk recedes,and the temperature gradient suddenly increases near the air intake radius.When the intake position is located at the middle of the radius,the thermal stress distribution is the most uniform.The thermal load is smallest with the central intake air while maximum value of thermal stress is smallest with the low radius intake position.