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Research On The Influence Of Non-axisymmetric Stator In Transonic Compressor With Distorted Inlet Total Pressure

Posted on:2020-07-26Degree:DoctorType:Dissertation
Country:ChinaCandidate:W G FuFull Text:PDF
GTID:1362330572468605Subject:Marine Engineering
Abstract/Summary:PDF Full Text Request
Recently,with the changes in global energy and power demand as well as environmental protection requirements,gas turbines have received great attention from relevant departments such as electric power and power industry.The United States,Europe,Japan,and other countries have successively formulated advanced gas turbine technology research and development plans to promote the development of gas turbines with great enthusiasm.High-performance gas turbines place urgent demands on high-load,high-efficiency,and high-stability margins for compression systems.In practical applications,the compressor operates under non-uniform inlet conditions almost without exception.The inlet distortion leads to a marked change in the original design conditions of the compressor,destroying the axisymmetric flow of the airflow,causing the stability margin of the compressor decreased and the performance deteriorated,and even causing the compressor to stall and surge,which seriously affects the whole machine normal operation.It can be seen that improving the stability of the compressor and resisting the distortion have great practical significance for ensuring the stable operation of the power system.In this paper,a transonic axial compressor designed on the basis of the experimental rig parameters of the Key Laboratory for Small Marine Gas Turbine Technology of Dalian Maritime University is studied by the numerical simulation.In order to simulate the compressor with circumferential total pressure distortion as close to the real prototype as possible,a computational domain including all passages is adopted.The further validation of simulation method shows that the numerical simulation method adopted in this paper meets the requirements of the compressor flow field analysis in this paper.Based on the numerical verification,the influence of different non-axisymmetric stator schemes on the flow field of the compressor under distorted conditions is studied by three-dimensional unsteady numerical simulation method.Firstly,by comparing the flow characteristics of the prototype compressor stage and the single rotor,it is found that the stage stall is closely related to the flow field in the stator,and the stall inceptions of the compressor stage and the single rotor are both"spike" type.By studying the influence of different degrees distortion on the compressor flow field,the transmission of the inlet total pressure distortion in the compressor is systematically obtained in the compressor.The circumferential total pressure distortion of the inlet causes a serious drop in the compressor's performance.The more serious the distortion is,the more obvious the performance degradation is.The inlet total pressure distortion has a greater impact on the flow field of the rotor and stator.In the flow field of the rotor,the amplitude of shock wave movement is increased and tip leakage flow is strengthened.In the flow field of the stator,the large-scale flow separation occurs in the upper corner region.The inlet distortion makes the flow field in compressor show obvious non-axisymmetry.The inlet distortion does not change the stall inception's type of the compressor.Then,the curved and twisted stator is developed based on the prototype compressor,and the influence of the curved and twisted stator on the compressor is analyzed by using steady numerical simulation method.The results show that the boundary layer of the suction surface of the curved and twisted stator is more resistant to the backpressure gradient,and the loss of the blade profile is lower,compared to the original stator.Based on this basis,a non-axisymmetric stator with curved-twisted blades consisting of five curved-twisted stators and 41 prototype stators is constructed.The unsteady numerical simulation results show that the unsymmetrical the curved-twisted stator can effectively improve the distortion resistance and flow stability of the compressor.Under the condition of DA=0.05,the non-axisymmetric stator with curved-twisted blades makes the stability margin of the compressor relatively increased by 11.63%;under the condition of DA=0.1,the non-axisymmetric stator with curved-twisted blades makes the compressor stability margin increased by 16.7%relatively.Non-axisymmetric stator with curved-twisted blades improves the flow capacity in the distortion zone by suppressing the flow separation in the upper corner of the stator blade,thereby reducing the aerodynamic load of the rotor blade,restraining the forward and backward movement amplitude of the shock wave and suppressing the tip leakage flow.However,when the curved and twisted stator improves the flow state in the upper corner,the flow separation in the lower corner is also caused,and the flow loss below 32%of the rotor blade height increases accordingly.A large extent of separation occurred in the lower corners of the nine prototype blades adjacent to the curved and twisted blades.The steady simulation study was carried out for 20%solidity reserved stator.20%solidity reserve of stator did not affect the mass flow rate at choke condition,stability margin is increased slightly.20%solidity reserve of stator could delay the stator corner stall,thus reducing aerodynamic losses of the compressor,but had little effect on the shock wave migration of the rotor blade.20%solidity reserve is used in the distortion zone of stator constituting the non-axisymmetric stator with variable cascade solidity and its flow field is solved.The non-axisymmetric stator with variable cascade solidity can improve the stability margin of the compressor with the distorted inlet.Under the condition of DA=0.05,the non-axisymmetric stator with variable cascade solidity makes the compressor's stability margin increased by 10.07%.Under the condition of DA=0.1,the non-axisymmetric stator with variable cascade solidity makes the compressor stability margin increased by 18.83%relatively.The non-axisymmetric stator with variable cascade solidity can delay the stator corner separation in the distorted region,and then reduce the shock wave motion and tip leakage flow.However,the effect of the non-axisymmetric stator with variable cascade solidity on compressor performance is slightly weaker than that of the non-axisymmetric curved-twisted stator.However,the non-axisymmetric stator with variable cascade solidity will not cause the flow field deterioration in other regions of the stator.Finally,on the basis of the first two non-axisymmetric stator schemes,a composite non-axisymmetric stator scheme is constructed and the flow field is solved.The results show that the composite non-axisymmetric stator can effectively improve the distortion resistance and flow stability of the compressor,while the composite non-axisymmetric stator combines the advantages of the previous two non-axisymmetric stators improving the flow separation in the stator corner region and the flow stability in the flow rotor passage.Under the condition of DA=0.05,the composite non-axisymmetric stator makes the stability margin of the compressor relatively increased by 22.30%;under the condition of DA=0.1,the composite non-axisymmetric stator makes the compressor stability margin increased by 24.87%relatively.In addition,by comparing the effects of composite non-axisymmetric stator on compressor performance at different rotational speeds,it can be found that the composite non-axisymmetric stator has stronger anti-distortion ability at low rotational speeds,and the stability margin of the composite non-axisymmetric stator is increased by 51.74%compared with the prototype compressor at 80%design rotational speeds.
Keywords/Search Tags:Compressor, Total pressure distortion, Non-axisymmetric stator, Corner separation, Stability
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