The LDV Measurement Research On The Velocity Of An Axial Flow Impeller Inlet

Axial flow impeller inlet velocity distribution reflects the uniformity of design quality of the inlet passage and the performance of pumps, get the velocity distribution provide the basis for the optimization of the impeller and inlet passage design, verify the pump and pump device numerical simulation results. This study measured the velocity distribution in axial impeller inlet of long straight pipe water inlet conditions with3D-LDV, analyzed the rule of impeller inlet velocity distribution under different flow, and mainly completed the following work:1tested the external characteristics of the axial flow pump measured, obtained the performance curves to determine the five different test conditions such as small flow rate, design flow, large flow rate etc.2used the disk to calibrate the LDV, guaranteed the accuracy of test results in the air, use LDV test the two-dimensional flow velocity of pipe, compare the flow by integral calculation and the flow read by electromagnetic flow meter to verify the velocity results tested by LDV through the window, the maximum error is-1.2%, the accuracy of the result is high, verified feasibility and accuracy of the results of the LDV test through the flat window.3arrange three radial test lines where from the impeller center at the distance of0.12D,0.22D,0.32D, measured the flow of impeller inlet with three-dimensional LDV.4analyzed the velocity distribution result, near wall treat with the power function to integral calculation, compare different program and flow integral calculation method based on velocity-area method was improved.The following conclusions can be drawn from the three-dimensional velocity measured by LDV:1on0.5Qopt～0.7Qopt conditions, axial velocity has the opposite direction near outer wall, tangential velocity is not0, and its direction consistent with the direction of impeller rotation, radial velocity have the reverse direction between the outer wall and hub, the flow condition is poor; on0.8Qopt～1.2Qopt conditions, the axial velocity distribution tends to be uniform, except the tangential velocity at the hub, tangential velocity is near0without rotating, radial velocity at the outer wall and hub have the same direction, flow condition is better.2the test line and test point arrangement based on the velocity-area method:the position of test line should be at the range of0.2D～0.3D from the impeller center, Less than0.7Qopt flow rate condition, the error of flow rate calculated by integral is big, outer wall measuring points should be arranged at0.95(R-R0); larger than or equal0.7Qopt flow rate condition, the measuring points near the outer wall at0.9(R-Ro) is appropriate; measuring point near the hub in0.1(R-R0)-0.2(R-R0) is appropriate.