Abstract
Ship ballast pumps have stringent requirements for their transient characteristics. Here, the pneumatic control valve and programmable logic controller (PLC) are applied to realize the rapid reduction in flow rate for ballast pumps, and the dynamic pressure of steady and transient conditions and inner flow for the ballast pump are tested and analyzed. The results show that the dynamic pressure of each study scheme has cyclical increasing trends, however, the larger the amplitude of the flow rate reduction is, the greater the pressure increasing rate of the two measuring points. While the flow rate decreases to 0.4× Qd and 0.2× Qd, the rate of pressure increase is first fast and then slow. The dynamic pressure pulsation intensity is higher than the corresponding steady-state conditions after the transient conditions. With the increase in flow rate reduction, the characteristic frequencies of the dynamic pressure are 1APF (axial passing frequency) and 1BPF (blade passing frequency) and their harmonic frequency. The rapid decrease in flow rate causes the separation vortex in the impeller channel to be generated in advance, and the scale increases, which reduces the pulsation intensity of the pump outlet to prevent an increase in the level of broadband pulsation between 2APF and 1BPF.
Highlights
The ballast pump is used for drainage and injection in the water tanks on ships
Jiang [9] studied the cause of transient conflict head through the analysis of transient hydraulic characteristics of the centrifugal pump during the starting period, and identified the cause as the time of the flow rate closed to the steady state as being longer than the rotating speed closed to the rated rotating speed
The method above was applied by Wu [14] to experimental research on the transient hydraulic performance of a centrifugal pump under different starting accelerations, and the results show that while the rotating speed approaches the maximum, the transient head is lower than the quasi-stable head, and these values have obvious differences among the different starting accelerations
Summary
The ballast pump is used for drainage and injection in the water tanks on ships. The double suction pump is widely applied to ship ballast systems because of its small volume and large flow rate. Shao [20,21] studied the transient characteristics of the closing valve of ultra-low specific speed centrifugal pumps, and found that the impact head appeared at the end of the pump start under different starting accelerations, and the development of the internal flow field generally lags behind the closing dead point of the steady state process. Transient processes, such as start-up and shutdown, have been studied extensively in experiments and numerical simulations. The inner pressure fluctuation of a ballast pump under transient operation is studied to perfect a test method for transient study
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