Numerical Simulation Analysis Of Two-phase Flow In Single Stage Transonic Axial Compressor

Wet compression can effectively improve the performance of gas turbine by reasonable spray.Gas-liquid two phase flow formed by coolant droplets and gas in compressor is an important characteristic of wet compression,and different coolant can cause different wet compression effect.So gas-liquid two phase flow in wet compression was numerically analyzed based on single stage transonic axial compressor.Heat and mass transfer between gas and droplets,droplet breakup and impingement effect of droplets were studied.The characteristic of wet compression with ethanol as the coolant was also compared with that of wet compression using water.Gas-liquid two phase flow in wet compression process was investigated.The results showed that:(1)When the concentration of coolant droplets reaches a certain degree,the increase of spray amount goes against evaporation and heat transfer of single water droplet in compressor.Larger slip velocity between water droplets and gas can strengthen the mass and heat transfer.The turbulence of continuous phase can form high frequency pulsation of velocity slip,which can promote the mass and momentum transfer,so that the turbulence evaporation is produced.Viscous resistance exists when droplets are dragged by gas to move,and bigger droplets cause more losses.When droplets are in turbulence of continuous phase,the frequent fluctuation of turbulence will cause more kinetic energy losses of gas and droplets.That whether the cooling effect of coolant evaporation can offset the resistance loss of liquid coolant should be comprehensively considered.(2)Disturbance of blades in compressor enhances the turbulence fluctuation of droplets and strengthens the interaction between gas and liquid phase.The rotor will indirectly transmit input work to droplets by drag and heat transfer effects between gas and coolant droplets.Reynolds number and Weber number of droplets in wet compression are small,and droplets will not break up by aerodynamic force at most positions in compressor.Shock wave and impingement effect can strengthen the particle breakup and motion fluctuation of droplet,but can only make the Web number reach the range of bag breakup.(3)Small flow angle of droplets is a key factor that causes the impact of droplets on blade.The rotation of rotor blade will improve the velocity of coolant droplets when impacting on rotor blade,while the impact of droplets on stator blade causes kinetic energy loss to droplets.The change extent for droplet velocity after impacting on blade indicates that the reactive force of water droplets acting on rotor blade is stronger than that on stator blade,and the impact force adds additional axial torque to the compressor.The impact effect of coolant droplets on blade should not be neglected.(4)The ability of heat and mass transfer for ethanol droplets is stronger than water droplets,and ethanol droplets break up easier than water droplets.The resistance effect to gas and impact strength on blade of ethanol droplets are weaker than water.The inlet mass flow,total pressure ratio and efficiency of compressor in wet compression with ethanol are superior to wet compression with water under the same spray conditions.When the injection particle is as small as 5 microns,water droplets show advantages on cooling effect and reducing specific work over ethanol droplets.According to the effect of different coolant on wet compression,several unresponsive coolants can be mixed and injected into compressor in wet compression to seek better wet compression effect.