The numerical analysis method uses an average S2 flow surface and a number of rotary S1 flow surface cross iterations. The streamline curvature method is used on the average S2 flow surface, and the influence of gas viscosity is considered by entropy increase; the flow function is used on the S1 flow surface. To solve the variables, the flow function governing equations are solved in a finite difference solution in the coordinate system. The aerodynamic parameters obtained by the average S2 flow surface and the rotating S1 flow surface are transmitted between the two flow surfaces, and the flow analysis of the average S2 flow surface provides the flow surface shape and the thickness of the flow sheet for the rotary S1 flow surface, and the flow of the S1 flow surface is rotated. The analysis provides an average S2 shape for the next iteration. Iteratively takes the convergence of the average S2 flow surface shape as a convergence criterion. For detailed numerical methods, see [2].
The aerodynamic equation on the average S2 flow surface is based on the literature. If the variable efficiency pol along the flow line is given, the velocity gradient equation considering the entropy increase on the average flow surface is dWdq=AWpol+Bpol+CW+DW1pol(1) where A =[cos2cosrc-sin2r]drdq-cos2sinrcdzdq+sinsincosddqB=[sincosdWmdm-2sin]drdq+coscos×dWmdmdzdq+rcos[dWdm+2sin]ddqC=dh1stdq-d(rV)1dqD=h{k-1k11-d1dq-[pol- K-1k]1h1dh1dq+ln[h1]dpoldq}-(pol-1)
In addition to the above velocity gradient equation, rdrdq must also satisfy the continuity condition, that is, the mass flow rate through the quasi-orthogonal line is qm=N∫q0Wcoscos(-)[2%rN-t]dq(2)S1 The aerodynamic equation on the turbulent flow surface is assumed to be unable to flow on the S1 turbulent flow surface, and the absolute flow in the impeller is assumed to be a non-rotating flow. The flow function is introduced by the continuity equation in the relative coordinate system: Um=-bWqmU=bWmrqm(3) The governing equation of the flow function on the S1 flow surface is 1r2U2+2Um2-1r21U+ Numerical analysis The Ghost centrifugal impeller was numerically analyzed using the above method. Johnson conducted a detailed measurement of the internal flow field of the Ghost centrifugal impeller and gave the velocity distribution over the five measured sections in the blade. The impeller channel geometry and the measured section position are shown. For comparison, the corresponding calculation results are also given. The main parameters of the impeller are: D2=0.91m, 2A=90°, N=19, n=500r/min, qm=3.3kg/s, and the medium is air. The geometry of the blade path and the measured section are compared with the results of the measurement in the five measurement sections, respectively. The median line represents the mainstream velocity, and the vector arrow represents the secondary flow velocity distribution on the section. It can be seen that, in the first two sections of the impeller channel, the calculation results are in good agreement with the measured results. The calculation results accurately predict the flow distribution of the flow high-speed zone at the impeller inlet on the pressure surface and the wheel cover side; On the upper part of the flow velocity zone, the migration from the pressure surface to the suction surface and the formation of the secondary flow vortex on the side of the wheel and the suction side are also accurately predicted. Relative Velocity Distribution on Section I Relative Velocity Profile Section III is at half the length of the impeller channel. The gas flows through the impeller for a distance, and the accumulation of viscous action begins to appear. The measurement results show that the cross section On the third wheel cover and the suction side, there is a tendency to form a wake area. Compared with the measurement results, the calculation results in the flow high-speed zone migration and secondary flow form can be well matched with the test results, but due to the assumption that the gas in the calculation is non-viscous, the wake region caused by gas viscosity The formation trend is not well predicted. At the cross section IV, the calculation results are inconsistent with the measurement results due to the continued accumulation of gas viscous effects. The calculation results can better reflect the change of the vortex area in the vicinity of the suction side of the center of the gas high-speed zone and the vortex area near the suction surface, and the results are also well matched on the wheel side; but on the wheel cover side, the test The results show that a significant wake region is formed at the intersection of the wheel and the suction surface on the section, and the calculation results still fail to predict the existence of this phenomenon. In addition, the difference between the calculation results and the test results is also reflected in the wheel cover and On the secondary flow distribution at the intersection angle of the pressure surface, the test shows that there is a clockwise turning vortex in this area on the section IV, and the calculation results are not well matched with the experimental results. This further indicates that the viscous effect of the gas is more and more apparent as the leaf path is extended, and the gas flow is greatly affected, resulting in deterioration of the flow in the local area. The section V of the relative velocity profile on section III is the section of the impeller exit. Compared with the experimental results, the calculated aerodynamic parameters are not in good agreement with the experimental results except for the secondary flow distribution from the suction surface to the pressure surface. The test shows that the high-speed zone of the fluid moves to the vicinity of the intersection of the suction surface and the wheel, and the wake region continues to expand. The calculation results show that the fluid high-speed zone only moves to the suction surface, and the wake zone still fails to predict. Relative Velocity Profile on Section IV The relative velocity profile on section V is the cross-sectional mean dimensionless static pressure p and the cross-sectional mean dimensionless rotational stagnation pressure ps along the channel distribution curve, and x/L is the relative position of the section from the inlet of the blade. . It can be seen from the figure that the average dimensionless static pressure p rises along the channel, indicating that the flow in the channel has undergone a boosting process, which reflects the effect of the impeller on the airflow; the dimensionless rotational stagnation pressure ps falls along the leafway, especially in The downward trend at the exit of the near-leaf channel is more obvious, indicating that the entropy increase caused by the viscous action of the gas is reflected in the latter part of the leaf channel, and the accumulation of viscous action appears as the formation of the wake region in the flow form, but on the thermal parameters. It is reflected in the reduction of the dimensionless rotation stagnation pressure ps. The comparison between the calculated results and the experimental results shows that the two agree well. This shows that although the quasi-ternary calculation results cannot predict the more complicated flow phenomena and details of the internal flow of the impeller, the complex flow can be predicted from the macroscopic average aerodynamic parameters. The general trend. Conclusion The Ghost centrifugal impeller was numerically analyzed using the S1/S2 quasi-ternary iteration method and compared with the experimental measurements. The results show that the quasi-ternary iterative solution is close to the measurement result when the flow does not separate; in the case of the flow loss rate, although the quasi-ternary iterative solution can not accurately predict the formation of the detailed flow phenomenon D wake and Development, but there can be a certain degree of prediction in the macroscopic quantity, which can meet the needs of engineering design, and the quasi-ternary iterative calculation is economical, so it is still an indispensable calculation tool for engineering design.
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