| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2000: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1999: ¥2,900,000 (Direct Cost: ¥2,900,000)
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| Research Abstract |
Flow measurements were made within the passages of the shrouded and unshrouded centrifugal impellers, by using a hot-wire anemometer rotated with the same speed as that of the impeller. The measurements were made for a flow rate corresponding to nearly zero incidence angle and two other flows with reduced and increased flow rates.
In the shrouded impeller, the measurements show that, as the flow rate is reduced, the regions of a low velocity and a dissipation enlarge from the shroud-side to the hub-side near the suction surface and the values of Reynolds normal stresses tend to decrease. The Reynolds shear stresses qualitatively follow the eddy viscosity concept. Near the suction surface, the effects of the flow rate on the shear stresses are remarkable in the cross-component between the passagewise and blade-spanwise directions, but are little in two other cross-components.
In the unshrouded impeller, a low relative velocity, a high dissipation and a high Reynolds stress appear around t
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he region of the middle blade-to-blade to the casing side due to both influences of a blade tip leakage and a secondary flow. As the flow rate is reduced, this region enlarges by nearing the hub and also tends to move toward the suction.
In the increased flow rate, the Reynolds stress is remarkably high near the casing of the suction side since the tip leakage noticeably influences there. In the reduced flow rate, the stress becomes high also on the suction because of the secondary flow strengthened near the casing. For three flow rates, however, the dissipation is remarkably high near the casing of the suction side ; the influence of the flow rate on the position with the highest dissipation seems to be little.
Moreover, the numerical flow analys is made in the passage of the centrifugal impeller using FEM with/without the turbulence model. The turbulence model is low Reynolds k-ε model proposed by Chien. We use the Euler explicit method for the Reynolds averaged Navier-Stokes equations and the transport equations of the turbulent energy and the dissipation rate. All equations are discretized by the Galerkin method. The numerical results qualitatively correspond with those obtained from the experiment. Less
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