Study On The Heat Transfer And Flow Characteristics Of Novel Turbulence Generators In Gas Turbine Blades

Aviation gas turbines are the main source of power for modern aircraft,which reflect the advanced level of the aviation industry.As a power component of a gas turbine,the performance of the turbine is critical to the overall performance of the engine.In order to obtain greater thrust and higher aerodynamic efficiency,the gas temperature before the turbine is continuously increasing and has far exceeded the withstand temperature of the advanced blade materials.Therefore,an effective and reliable cooling structure needs to be designed for the blade to ensure the stable operation of the turbine and the entire engine.Ribbed channels and pin-fins channels are typical forms of internal cooling in turbine blades.Ribs and pin-fins are the main factors affecting the performance of the channel and have great potential for improvement.In this paper,the numerical simulation method is adopted to optimize the geometries of the traditional turbulence generators in the cooling channel to further improve the heat transfer performance.The typical Reynolds number of 10 000~60 000 in the turbine blade is selected.Wavy rib is proposed to enhance the heat transfer performance of the cooling channel in the middle of the turbine blade and improve the flow characteristics.A preliminary performance comparison is conducted between the wavy rib with simple structure and the conventional ribs.As a result,it is found that the wavy ribs have the good potential to further improve the ribbed wall heat transfer while reducing the pressure loss of the channels,and are the main research objects below.Among the three common rib turbulators of 45° inclined ribs,45° V-shaped ribs,and 45° W-shaped ribs,the 45° V-shaped ribs with the best heat transfer improvement are selected as the contrast scheme of wavy ribs,to further highlight the advantages in increasing heat transfer and reducing pressure loss.The multi-impingement plates is present to further improve the heat transfer performance of the turbine blade trailing edge.By comparing the heat transfer enhancement and flow loss with those of the traditional pin-fins,the performance of multi-impingement plates is clarified.The characteristics of the multi-impingement plates are clear: the heat transfer improvement performance is excellent,while the pressure loss is great and the geometry structure is complex.Meanwhile,the thermal performance is better than that of pin-fins within the typical Reynolds number range of the wide channel in turbine blade trailing edge.A preliminary study of the jet distance and the plate thickness of the multiimpingement plate is carried out.A variety of typical Reynolds numbers are considered and it is found that both the heat transfer performance and the friction loss are inversely proportional to the values of the two geometrical parameters.The effects of the rib height,rib round radius,rib angle and rib thickness on the performance of wavy ribs is studied in a stationary single-pass channel,taking into account the influence of the Reynolds number.The distributions of the flow field near the ribbed wall and on the cross-section of the channel are selected for analysis,and the pressure loss coefficient of the whole channel is also present.It is found that the diversion effect of the wavy ribs on cooling air is the main reason for effective pressure loss constraint.Ribbed wall is the most important heat transfer surface of the cooling channel,and its heat transfer performance is the main research object.At the same time,the heat transfer performance of smooth side wall has also been studied.According to the boundary condition of the constant wall temperature in numerical simulations,the heat transfer rate or heat flux on the heated wall corresponding to the ribbed wall is the final parameter to measure the heat transfer performance of the turbulence generators.The Nusselt number ratio,thermal performance,and area increment of the ribbed wall,the heat transfer contribution and area ratio of wavy ribs on the ribbed wall,are given to clarify the influences of various geometrical parameters on the heat transfer of the channel walls.In the U-shaped channel,the effects of wavy ribs on the flow of cooling air and heat transfer of all surfaces are studied,and the influence of rotation is considered.By showing the three-dimensional flow field near the ribbed wall,the impacts of wavy ribs,rotation and U-shaped turn on the fluid flow are analyzed.On this basis,the flow characteristics on the ribbed wall,side wall,and top wall are studied,and the reasons that the above three factors affecting the flow loss and the wall surface heat transfer are explored.Combining the distribution of Nusselt number ratios on all surfaces of the channel,the influence of wavy ribs on the rotation effect is clarified.High-performance wavy ribs with better heat transfer performance and almost equal pressure loss than those of the contrast scheme are summed up in the typical statinary singlepass channel,stationary and rotating U-shaped channels of turbine blades.The increments of the heated wall heat flux corresponding to the ribbed wall and the pressure loss coefficient are the two main parameters to measure the heat transfer performance and flow characteristics of the channel.The heat transfer rates on the wavy ribs surface and the end wall,the heat transfer area ratio of the wavy ribs surface,the Nusselt number ratio on the wavy ribs surface and the end wall,are present.The large surface area of high-performance wavy ribs is the root cause of superior ribbed wall heat transfer.High-performance wavy ribs are studied at different Reynolds number and rotation numbers and it is found that they all perofrm well.At the same time,it is determined that the high rib height is the design direction of the wavy ribs,and the large rib round radius and the small rib angle are the further design directions.