Study on pressure field characteristics of high specific speed axial flow pump under full working conditions based on wavelet transform

Axial flow pumps are widely used in ship jet propulsion units and coastal plain pumping stations. In the actual operation process, axial flow pumps need to operate in extreme working conditions, in order to explore the safety and stability of axial flow pumps operating under special working conditions, this paper adopts a method that combines model experiment and numerical simulation. A full-condition model experiment of the axial flow pump section (AFPS) is carried out on the high-precision axial flow pump system test platform. Meanwhile, a simulation model predicting the full characteristics of the AFPS is constructed. Numerical simulations are carried out for the AFPS at 31 flow rates, and the hydrodynamic characteristics of the AFPS are investigated in depth in 8 conditions, which reveals the internal evolution of the AFPS under the synergistic influence of the water flow direction and the impeller steering in the whole quadrant. The traditional analysis method Fast Fourier Transform is difficult to analyze the dynamic changes of such a complex non-smooth signal in the flow field under full operating conditions of axial flow pumps. In this paper, the wavelet transform is used to analyze the pressure pulsation signals in the time–frequency two-dimensional plane at multiple scales, to capture the time–frequency subtle changes, and the cross wavelet transform reveals the signal relationships at different locations, which comprehensively and deeply reveals the pressure pulsation spatiotemporal transformation characteristics of the pump section. The results show that when the water flow direction is opposite to the rotation direction of the impeller, the internal flow of the AFPS is disordered and the pressure pulsation is strong. Except for the forward flow turbine condition when the impeller is rotating forward (OP4) condition, the wavelet energy at the impeller inlet is greater than that at the impeller outlet with a maximum difference of eight times (OP5). The pressure pulsation between the inlet and outlet of the impeller has a large number of common frequencies.