Investigation On The Flow Characteristics In Radial Pre-swirl System

In a gas turbine,pre-swirled cooling system has become an important component of the secondary air system.It directs the cooling air to a rotating state prior to injecting the cooling air into cooling passages in turbine blades and other high-temperature components.This reduces the total temperature of the air in the rotating reference frame,hence it was widely applied.In the present paper,the experiments and numerical simulations were carried out on the flow characteristics in radial pre-swirl system.A radial pre-swirl rig with cascade nozzle was designed and constructed to study the effects of rotational Reynolds number,pressure ratio,non-dimensional mass flow rate and the number of receiver holes on total temperature drop and total pressure loss of outflow.Then,calculation models with drilled hole,convergent,ladder-shaped and cascade nozzle of radial pre-swirl system was built,CFD method was applied to research the discharge coefficient of the four types of nozzles and the change of temperature and pressure inside of the radial pre-swirl system.Meanwhile,CFD was done to investigate the influence of different pre-swirl nozzles and receiver holes and rotating-disc vanes on the flow.The difference of outflow and flow field characteristics between the radial pre-swirl and the axial pre-swirl are compared and analyzed.In the research range of this paper,we can find the outlet total temperature drop increases with the increase of rotational Reynolds number,pressure ratio and mass flow rate,the total pressure loss increases with the increase of pressure ratio and mass flow rate,rotational Reynolds number has little influence on total pressure loss.The discharge coefficient of cascade nozzle is 12% higher than drilled hole nozzle,5% higher than convergent and ladder-shaped nozzle.The flow in radial pre-swirl system is quite complicated,the temperature and pressure decrease first and then increase.The total temperature drop of drilled hole nozzle is 20% lower than other three nozzles,but the total pressure loss of four types of nozzles are very close.The performance of radial pre-swirl can be improved by optimizing the nozzle structure,enlarging receiver hole area,tilting receiver hole and adding vanes in rotating cacity.Under the same conditions,radial pre-swirl system has better cooling efficiency than axial pre-swirl system,but greater loss of total pressure.The average error between simulations and experiments result is about 30%.