| With the continuous advancement and development of aviation technology,the thrust and power of aviation engines have become higher and higher.This has led to the continuous increase of gas temperature and greatly exceeded the limit of turbine blade materials,so it needs to be further strengthened cooling measures to ensure the normal operation of the engine.In order to meet the needs of new models,the thrust of existing engines needs to be increased by about 10%.This leads to the increase of the gas temperature by about 140 K,and the corresponding comprehensive cooling effect of the turbine blade needs to be increased by about 10%.With this background,this paper conducts an improvement study on the cooling structure of the first-stage blades of a certain type of high-pressure turbine to achieve the goal of improving engine thrust.Due to the complicated design and improvement process of the turbine blade cooling structure,the technical requirements are very high,and the difficulty is very large.In this paper,the main practices of the industry at this stage are used in the research.For the simplified blade model,the three-dimensional numerical calculation finds its flow and heat transfer characteristics and defects,proposes an improvement plan for the defects,and gradually optimizes to the goal of improving the overall cooling effectiveness by about 10%.After determining the new structure of the simplified blade,use the mid-temperature comprehensive cooling effect experiment to verify the simplified blade of the new structure.When the experimental verification is completed,the static straight blade verified by the experiment is restored to a rotating twisted blade under high temperature conditions.The three-dimensional numerical calculation method of coupled heat transfer is used to verify its cooling effect,which provides support for the subsequent trial operation verification of real blades on the engine.The main conclusions of this study are:1.There are many influencing factors when directly improving the cooling structure of the blade with a more complicated structure under real working conditions,and the uncertainty of the improvement effect is relatively large.The research on the characteristics of the flow heat transfer between the blade rotation and non-rotation,twisting and non-twisting,high-temperature and low-temperature conditions confirms the feasibility of simplifying the blade,and theoretically provides the current research route for simplifying the blade.2.For the mid-string cooling system of original cooling structure,the heat transfer of internal cooling is weak,and there is a flow dead zone between the ribs.It is proposed to change all the turbulent straight ribs in the blade mid-chord cooling system to replace the ribs with stronger heat transfer and reducing the distance between the ribs.It can enhance the heat transfer coefficient of the area where the turbulent ribs exist in the internal cooling channel of the mid-chord cooling system and eliminate the flow dead zone.As the film cooling effect is basically unchanged and the internal heat transfer coefficient is improved,the overall cooling effectiveness in the area of the mid-chord cooling system is improved.3.Through the three-dimensional numerical calculation,it was found that the cold air from the internal structure of the original cooling structure’s leading edge system caused a backflow vortex,which caused the uneven internal flow field and the unevenness of the film outflow along the direction of the blade height.The parallel impact of the on the film hole intake structure was used to eliminate the channel backflow vortex,makes the outflow of film hole in the leading edge more uniform,and strengthens the internal heat transfer,reaching the overall cooling effectiveness of leading edge along the direction of leaf height is improved and evenly distributed.4.According to the calculation and analysis of the coupled heat transfer of the original cooling structure,it is found that the impact cooling structure with a large flow resistance and strong heat transfer is proposed for the leading edge and trailing edge in view of the shortcomings of the mid-chord,which has less cooling air and weaker cooling effect.The mid-chord uses the expanded film hole with low flow resistance and high cooling efficiency,which not only ensures the overall cooling effectiveness of the leading edge and the trailing edge when the amount of cold air is reduced,but also increases the overall cooling effectiveness of mid-chord area.The amount of cold air and the cooling effect make the overall cooling effectiveness of the leading edge and the trailing edge greatly improve the comprehensive cooling effect of the mid-chord area without reducing the cooling effect of leading edge and trailing edge.5.Designed and built a medium temperature overall cooling effectiveness test stand by ourselves,and carried out experimental verification on the simplified blade after improving the cooling structure.It was found that the overall cooling effectiveness on the improved blade surface increased 10.9% under the condition that the flow of cold air was unchanged.The static straight blades verified by the overall cooling effectiveness experiment were restored to rotating twisted blades under high temperature conditions.The three-dimensional numerical calculation method of coupled heat transfer was used to evaluate the cooling effect.It was found that the overall cooling effectiveness of the blade with improved cooling structure increased by 9.7% in the case of a 13% reduction in cooling capacity compared with the original blade.It can be seen from the research in this paper that the process of improving the cooling structure of the blade is more complicated and has many influencing factors.Therefore,in the process of improving the structure of the blade,many factors must be considered at the same time to improve the cooling structure of the blade. |
PDF Full Text Request