On The Aerodynamic Design Method And Flow Control Mechanism Of Highly Loaded Compressors In A Heavy Duty Gas Turbine

The development trend of modern heavy duty gas turbine compressors is to achieve higher pressure ratios in fewer stages.For this reason,the increasing stage loading makes the aerodynamic design method and flow control method of a compressor become the key to the success of a compressor design.In view of a highpressure compressor of a 400 MW G/H-class heavy duty gas turbine,the research of this dissertation was mainly divided into two parts,the aerodynamic design method and the aerodynamic configuration.In order to achieve a rapid and accurate design of a multistage compressor,the design process of a highly automated multistage compressor was set up.In this way,the selection of design parameters in the design process of a compressor and the distribution of aerodynamic loading were studied systematically,and the general rules of the design of a multistage compressor were summarized.Based on the understanding of the design method,to verify the method on purpose,an aerodynamic design of a single-stage low-speed axial compressor has been completed with a pressure ratio of 1.20,and loading coefficient of 0.83.While maintaining the stall margin of 27.1%,the isentropic efficiency was 86.1% at the design condition.Since then,in order to further improve the compressor performance,through the re-distribution of aerodynamic loading and design parameters,as an active flow control technology,boundary layer suction was introduced to explore the design idea of the aspirated compressor.While maintaining the pressure ratio and the stall margin,the isentropic efficiency of the single stage compressor is raised to 88.4% at the design condition.After that,relied on the basic understanding of design parameters,and in-depth analysis of the velocity triangles and Smith charts,an aerodynamic design of a multistage high-pressure compressor in a heavy duty gas turbine has been completed,with 17 stages to realize a pressure ratio of 23,the stage-averaged pressure ratio was 1.20.Among them,the polytropic efficiency of the former six stages was 89.0%,and the stall margin was 25.6%.Since then,through the further analysis of the relationship between the design parameters,the distribution forms of the flow coefficient and loading coefficient of each stage of the multistage compressor were adjusted,the aspiration configuration was concentrated and simplified.The re-design aspirated compressor was designed to be 13 stages with a pressure ratio of 23,the number of stages was decreased by 29.4%,the axial length was reduced by 0.37 m,the number of blades was reduced by about 20%,the stage-averaged pressure ratio was raised to 1.27.To solve the flow problems extracted from the aerodynamic design processes,the mechanism of the compound three-dimensional blading technology and different configurations of boundary layer suction technology have been made a deep exploration.For the thickening of the near-endwall boundary layer in the middle and posterior stages of a multistage compressor,and the flow deterioration the near the corners,compound three-dimensional blading was divided into a locally-bowed blade to match the flow angle between the rows and a globally-bowed blade to re-organize the attached vortex layer on the blade surface.Between the different re-cambered blading methods,to increased the metal angle of the leading edge with the stacking of trailing edge is most effective to reduce the incoming incidence.Meanwhile,combined with blade positive globally-bowing,the blade negative locally-bowing can eliminate the incoming incidence while maintaining the blade loading near the endwalls,to compensate for the increase of the incidence due to the blade positive bowing.By numerical simulations,according to the flow field analysis of different diffusion cascades,the blade globally-bowing has a certain control over the vortex structures in the diffuser cascade,mainly by controlling the distance between the concentrated shedding vortex and passage vortex and the strength of the concentrated shedding vortex to improve the flow in the blade.However,the control of the separation vortex layer is only the appearance of the mechanism of the blade bowing,and the control of the attached vortex layer is the truly effective means of blade bowing.The enhanced radial pressure gradient on the blade former and middle surface of blade bowing is used to migrate the attached vortex layer near the corner to the midspan.Even if the attached vortex layer near the midspan separates und er adverse pressure gradient,due to the longer distance between separation vortex layer and endwall,the flow near the corner will not stall.Thus,the incidence when corner stalls can be increased and the effective operating range of the cascade can be widened by 91.9%.Applying the three-dimensional blading to the designed single-stage lowspeed compressor,the peak efficiency can be rained by 0.29%,the stall margin can be raised to 48.8%.Meanwhile applying to the last two stages of the designed multistage compressor,the problem of narrow work range can be effectively solved,and the left branch of the characteristic line is widened by 439.6%.The introduction of boundary layer suction technique makes it possible to design a higher loaded aspirated compressor.The mechanism of different aspiration configuration is different,and the design idea is different while combined with blade bowing.By numerical simulations,it is found than suction surface aspiration can effectively suppress the development of the boundary layer on the blade suction surface,and has a certain suppressed effect on the concentrated shedding vortex on the blade suction surface.The optimal suction surface aspirated bowed design can effectively reduce the stagnation pressure loss by 37.35%.The mechanism of blade bowing in a suction surface aspirated cascade is similar to that in an unaspirated blade,the attached vortex layer along the span is re-distributed to balance the loss increase near the midspan the loss decrease near the endwalls.Meanwhile,blade bowing has the positive effect on the decrease of entropy rise of the flow in the plenum and the reduction of suction power required.Endwall aspiration can pertinently remove the low momentum fluid near the corners,effectively widen the work range of cascade.The optimal endwall aspirated bowed design can widen the work range by 129.7%.According to the limited control zone of endwall aspiration,blade positive bowing has a negative effect on the endwall aspiration to remove the low momentum fluid near the midspan,meanwhile,it is easier for endwall aspiration to improve the mainflow performance with blade negative bowing.However,the reduction of the mainflow loss is nearly offset by the stagnation pressure loss of the aspirated flow,thus the reduction of the loss of the whole aspirated cascade is not significant.With the applying of combined aspiration configuration to the last stage stator of the multistage compressor,the effective flow in the stator blade under big adverse pressure gradient can be realized.