Research On Turbine Aerodynamic Design System With Optimization Of Film Cooling And Conjugate Heat Transfer

As an important component of the engine, the turbine has a critical influence to thewhole performance of the engine. The current engine requires higher propulsiveefficiency and thrust-weigh radio, the gas turbine thermal cycle theory shows that toachieve this goal the initial temperature before the gas turbine should be increasedsignificantly, as a result the amount of coolant increase which makes it difficult forturbine aerodynamic design and then the performance of cooled turbine has been limited.The traditional design system separates the whole process into several isolateddiscipline which is not conducive to modern cooled turbine design. In the early stages ofdesign, it lacks the consideration of heat transfer design. Also when the heat transferdesign is completed, several factors affect the aerodynamic performance of the originaldesign, such as the structure, the large amount of coolant and the change of boundaryconditions. The problem also appears in the optimization process for cooled turbineaerodynamic performance as it lacks the consideration of heat transfer design, so wecan’t ensure the reliability and practicality of the optimization results. In modern cooledturbine design process, the blade profile design and the cooling structure design shouldbe coupled tightly. With the situation above, this paper improved the cooled turbinedesign system and applied the system to design and optimize several turbines, and thenthe results verify its practicality. In the process of the design system application, thispaper analyzes the aerodynamic performance and heat transfer performance and it alsogives the design idea for a certain sum.This paper improved the design system, the original design system could not assessthe effect of the the cooling structure and film cooling on the aerodynamic performanceof the cooled turbine with large amount coolant accurately in the early stage of thedesign and optimization. To solve these problems, this paper establish thethree-dimensional optimization platform considering film cooling and thethree-dimensional conjugate heat transfer optimization platform. This paper usesone-dimensional program to design, check and optimize the parameters of five turbines,and then the parameters of six turbines are designed, checked and optimized with S2program. Then this paper analyzes and summarizes the design features and designparameters of different types for the subsequent research and development. The workabove also confirmed the practicality of the system for engineering design andoptimization.Before the platform establishment, this paper researches the factors that can affectthe accuracy of aerodynamic efficiency and heat transfer performance for cooled turbinenumerical simulation, including multi-component diffusion, heat radiation, and wall boundary conditions and stacking position adjustment. This paper proposes using thedissipation function as the loss assessment method for cooled turbine. Compared withother loss assessment methods, such as entropy increase, total pressure loss coefficientand the energy loss coefficient, dissipation function can provide a more accurateassessment about the loss distribution, as it eliminates the influence of the coolant.In this paper, turbine design and optimization system is used to complete theaerodynamic design and optimization process of one marine five power turbine. Thefinal design shows a statisfactory performance at the design and off-design conditions,also the test shows that single rotor blade attack angle loss decreased significantly witheach different attack angles, and the test for the first stage shows that the performance ofthe design meets the requirements, in this part the multi-stage turbine design processand design ideas were summarized partly. The design and optimization system is alsoused for a civil aviation high-pressure turbine design, three-dimensional numericalsimulation is used to check and adjust the aerodynamic performance and heat transfereffect preliminary, the results shows that the design is reasonable and this paper alsosummarizes some design features for this turbine. The final design of the turbine isdetermined by three-dimension design. The design which is obtained in the previousmodule is always corrected in the subsequent module.This paper established a three-dimensional platform considering film cooling, alsothis paper disscussed the optimization objective function and variables selectionprinciple, this platform can take full advantage of multi-objective optimization Paretosets to express the optimization results, and then the designer can select differentdesigns to meet different requirements. This platform was used to optimize themodeling parameters of blade profiles and film cooling holes for one stator and onerotor, the aerodynamic efficiency and heat transfer effects were improved a lot. Theaerodynamic efficiency and heat transfer effects of a small flow high-pressure turbinestage were also improved by multi-objective optimization with this platform. Thedecrease of the profile loss and transverse secondary flow loss is the main factor for thesingle blade efficiency improvement. The aerodynamic performance improvement ofthe turbine with small flow, large expansion ratio and low aspect ratio mainly due to twofactors, the first one is the decrease of shock loss, and the second one is the change ofseparation form and position located in the pressure side. This paper summarizes theaerodynamic performance effects of some modeling parameters, analysis theaerodynamic performance and the heat transfer performance impact of film coolingholes with compound angle which is downward along the span wise.Finally, this paper established three-dimensional conjugate heat transferoptimization platform with the same Pareto set to express the optimization results. This platform uses multi-objective optimization method to optimize the modeling parametersof blade profile and stacking line for one stator with simple cooling structure, theaerodynamic performance was improved, while the situation of the trailing edgeablation was alleviated. For the blade with high ratio of diameter to height, thereduction shock losses and secondary flow loss is a major factor which improved theaerodynamic efficiency. In addition to increasing the amount of the coolant, it also canreduce the amount of fluid with low-energy by controlling the profile and stacking lineto improve the heat transfer effect near the end zone. The conjugate heat transfermulti-objective optimization for one rotor and one turbine stage was also carried out inthis paper; the aerodynamic efficiency and heat transfer effect were improved a lot inthe case of flow resistance kept consistent. The establishment of the three-dimensionalconjugate heat transfer optimization platform is the foundation of the multidisciplinaryconcurrent design.