Experimental Investigation On Supercritical Adjust Nozzle And High Pressure Stage And Numerical Investigation On Remodification Blades

The supercritical turboset is being developed to save energe and reduce emission. To improve the relative inner efficiency, depress the coal cost, and reduce the harmful gas discharged into the air, several modern design technologies, such as meridian shrink shroud and bowed, swept and twisted blades, and so on, are applied to modify the on-line running supercritical turboset. In addition the re-design and modification could provide technical reserve for developing Chinese supercretical turboset with independent intellectual property rights.To re-design the introduced supercritical turboset, one has to digest and absorb its design theory and experience in the first place. Thus three representative prototype cascades, including the guide vane of the adjusted stage and the eighth stage (stator and rotor), are selected as the test model in the low speed wind tunnel. Although the test conditions don't satisfy the requirement of modeling theory, one could analyse the aerodynamic performance of the prototype cascade and confirm its design idea according to the experiment. What's more, the measured data can be employed to validate the CFD code.The aerodynamic parameters distributions of the three cascades along the blade hight and pitch at different incidences are detailed measured with the five-hole survey probe. And the limited streamline patterns on the endwalls of the cascades are displaced by the ink trace visualization technique. Based on the theretical analysis on the test results, the effects of the blade leading edge shape, load distribution, bowed and swept blade and incidence on the cascades aerodynamic performances are discussed in the following segment.There is an even static pressure distribution along the blade height in the adjusted stage guide vane because of the meridian-shrink shroud. Such pressure distribution could control the radial flow in the boundary layer and decrease the negative influence of the adverse pressure gradient at the suction side exit. The aft-loading characteristic of the vane largely depresses the transverse pressure gradient in the front and at the midst of the passage, and it also decreases the transverse secondary flow at the endwalls and the separation at the suction side corner. The variation of total flow loss is rather small at incidences ranged from -10°to 10°, indicating fine incidence adaptability of the test cascade. For the eighth pressure stage, the aft-loading technique and positive bowed blade profile are employed. Thus the aerodynamic loads on the upper and lower endwalls are remarkably decreased, which leads to reduced local transverse pressure gradient and the lowest flow loss on the endwalls. Due to the positive bowed vane profile, there is"C"type static pressure distributions along blade height on the vane surfaces. Such pressure distributions could decrease corner separation and result in even diffusion of the low energy gas in the corner boundary layer at the suction side into main stream. It is also shown in the test that there is no radial flow in the boundary layer on the blade surface at most of the blade hight.To improve the aerodynamic performance of the supercritical steam turbine and found the design technology with independent intellectual property rights, the modification of the adjusted stage guide vane and the eighth pressure stage are carried out. And the solver is NUMECA, which has been validated by the measured data mentioned above. The effects of bowed, twisted and swept blade on the aerodynamic performance of cascade are investigated by numerical simulations. Then the matching design of the eighth pressure stage with swept blades is carried out to study the performance of the stage with swept blades in the design operation condtions.The numerical results of the modified adjusted stage vane indicate that the positive blade leads to similar flow loss to negative blade dose, and the former one would bring more even distributions of aerodynamic parameters along the radial direction than the latter one. Without preventing abrading measure on the shroud, the positive blade is suggested to be employed. Compared with the results by positive and negative bowed blades, the prototype adjusted vane cascade, with meridian shrink shroud, is with the highest flow efficiency and the most even aerodynamic parameters distributions along the radial directions. Thus the adjusted stage vane with meridian shrink shroud is advised to be ultilized after preventing abrading measure applied to the shroud.The swept techniques, including backward swept one and forward swept one, are applied to the eighth pressure stage. For the backward swept stator and rotor, the fluid flow at radial midst enters into the passage earlier than that near the upper enwall, and greater pressure drop occurs at the passage midst, resulting in the C-type pressure distribution along the radial direction. Such pressure distribution could reduce the low energy fluid at the corner, thus there are slightly decreased and similar flow losses in the stator and rotor, respectively, compared with the prototype stage. For the forward swept stator and rotor, there are opposite effects on pressure distribution and the flow losses. A reverse-C-type pressure distribution occurs along the radial direction, and the low energy fluid flow towards the endwalls, strengthening the corner separation in the corner at the suction side. Therefore the flow loss in the stage is increased.To sum up, the pressure distribution of fluid and the energy loss coefficient could be affected by the swept blades. Since the axial positions of fluid at differet radial position differ from each other, the C-type pressure distribution occurs in the backward swept blade, but the reverse-C-type one in the forward swept blade. In addition, the total energy loss coefficient of the prototype stage is the smallest, but that of the forward swept one is the largest.