Study of the effect of inlet guide vane (IGV) prewhirl angles on impeller/diffuser interaction

Under different inlet-guide-vane (IGV) prewhirl angles and by using an unsteady approach, a numerical simulation was conducted of the unsteady interactions among the following three components: IGV, impeller and diffuser, moreover, a comparison with the test results was performed. Studied was the effect of IGV prewhirl angles on the flow and unsteadiness inside the impeller and diffuser. Meanwhile, the mechanism of interactions among the above-mentioned three moving and stationary components was also explored. The results show that the calculation results are in good agreement with the test ones. At a same flow rate, the wake flow of the IGV and the unsteady function of a large-sized vortex cluster will weaken the unsteadiness of the impeller and diffuser with the changing radian being only about 1/4 of the original magnitude . When the IGV assume a negative prewhirl angle, the unsteady influence brought about by the wake flow of the IGV is much smaller than that when the IGV take on a positive prewhirl angle. The unsteady effect arising from the wake flow of the impeller and potential-repercussion action of the diffuser, however, will be somewhat bigger than the case when the IGV have a positive prewhirl angle.