Analysis Of Flow And Heat Transfer Characteristics Of Swirl Cooling Based On Thermal-Fluid-Structure Coupling Method

As an important heat engine,gas turbines play a key role in aviation,aerospace,ships and other fields.The advanced gas turbines gas temperature has far exceeded the heat resistance limit of turbine blade materials,and the development of efficient cooling methods is critical to the safe and stable operation of turbine blades.Swirl cooling has attracted more and more scholars’ attention due to its higher heat transfer performance and better thermal uniformity.The thermal-fluid-structure coupling analysis method has been widely used in the field of turbine blades,but it is not fully utilized in the process of swirl cooling analysis.It is of great engineering practical significance to study the complete process of high temperature gas scouring blades,blade heat conduction,and coolant convection cooling blades,so as to accurately determine the boundary conditions of the swirl cooling heat transfer target surface.Firstly,a three-dimensional model composed of high temperature gas cascade channel region,blade leading edge solid region and swirl cooling region is constructed.Six swirl chamber heights of 15,19,23,27,31 and 35 mm are selected to explore the influence of swirl chamber height on cooling performance.The results show that as the swirl chamber height decreases,the flow area decreases and the coolant density increases.The swirl coolant scouring effect on the target wall is enhanced,the heat transfer performance is improved,and the corresponding flow resistance coefficient is gradually increased.The flow resistance and heat transfer performance are comprehensively evaluated by comprehensive heat transfer factors.The results show that when the swirl chamber height is 19 mm,the swirl cooling flow and heat transfer characteristics are the best.As the swirl chamber height decreases,the swirl cooling heat transfer effect gradually increases,and the blade solid temperature,thermal stress and thermal strain gradually decrease.Secondly,the ellipse with the ratio a/b of the vertical axis and the horizontal axis of 0.48,0.72,1.00,1.31,and 1.73 is used to construct the swirl chamber leading edge profile,forming the target wall with different curvature.The swirl cooling flow and heat transfer characteristics and the blade solid region stress and strain characteristics are analyzed under different target wall curvature.The results show that with the decrease of a/b value,the target wall high Nusselt number region changes from a long strip to an ellipse.When a/b=0.72,the target wall average Nusselt number is the highest,and the flow resistance coefficient is small,so the optimal comprehensive heat transfer factor is obtained.As the value of a/b decreases,the blade solid region temperature and thermal stress gradually decrease.Because the change of a/b value causes the blade solid thickness to change,the thermal strain change trend is more complicated.Turbine rotor blades are in high-speed rotating motion.In order to explore the application of swirl cooling in rotor blades,five rotation numbers of 0,0.183,0.339,0.457 and 0.512 are finally selected,and the thermal-fluid-structure coupling analysis is carried out on the swirl cooling under rotation conditions.The influence of centrifugal force,centrifugal buoyancy force,Coriolis force and Coriolis buoyancy force generated by blade rotation on swirl cooling is discussed.And a measure to improve the swirl cooling performance under rotation conditions is proposed.The results show that at the high rotation speed,the centrifugal force drives the coolant to flow swirl chamber downstream.A large amount of coolant accumulates in the chamber downstream,and the pressure rises,resulting in a higher centrifugal buoyancy.The centrifugal buoyancy force causes the coolant to flow back and flow out from the upstream nozzle.The upstream target wall cannot be flushed well by the coolant,and the heat transfer effect is poor.The thermal load has the most significant influence on the blade stress and strain characteristics.Due to the insufficient cooling performance of swirl chamber upstream,the blade root region temperature is higher,resulting in higher thermal stress concentration.In addition,by improving the intake chamber into a convergent form,it promotes the coolant flow to the nozzle side and reduces the influence of back flow coolant,thereby obtaining better swirl cooling performance.