The influence of counter-rotation between the inducer and impeller, along with a newly introduced system for their independent rotation on the pump cavitation characteristics, has been studied experimentally. Remarkably, this pump allows users to select between co-rotation and counter-rotation modes, providing significant operational adaptability. The high-speed camera is used to analyze vaporization structures and closely monitor the stability of the head pressure delivered by the pump during the cavitation testing phase. For both co-rotation and counter-rotation modes, different types of cavitation within the inducer and between the inducer and the impeller at three varied flow rates have been studied using image analysis. The results reveal improved cavitation performance and comparable efficiency at consistent pressure–flowrate combinations, emphasizing the advantages of counter-rotation across the three tested flow rates. In counter-rotation mode, the tangential velocity of the flow at the output of the inducer is opposite to that of the co-rotation mode. Consequently, the tangential velocity of the flow entering the impeller is reduced, leading to enhanced flow stability and increased pump pressure. The findings from image analysis demonstrate that the structure of cavitation varies between co-rotation and counter-rotation modes. Reversing the rotation direction of the inducer not only improves the pump cavitation characteristics but also changes the vapor structure due to changes in the flow pattern.

This article introduces an innovative design for a centrifugal pump featuring an inducer that enables the independent rotation of both the inducer and the centrifugal impeller. Unlike conventional designs, this configuration allows for differential speeds and customizable rotation directions, including co-rotation and counter-rotation modes. These new capabilities offer numerous operational advantages. This study investigates the impact of the speed ratio between the inducer and the impeller on the pump’s performance in both the co-rotation and counter-rotation modes. The results demonstrate that the independent rotation of the inducer expands the pump’s operating range, while counter-rotation significantly enhances the generation of pressure and the pump’s efficiency compared to co-rotation. These findings pave the way for the development of pumps that offer benefits such as a reduced size, reduced vibration, minimized energy consumption, and improved cavitation performance.

The surge limit on automotive turbocharger needs to be avoided to prevent operations with pressure and mass flow oscillations. Mild surge is accompanied by noise which is disturbing. Deep surge can cause significant loss of engine power and severe drivability issues. It is necessary to know the stationary limit in order to match a turbocharger with an engine, ensuring enough surge margin. However, this choice does not guarantee surge free operation during transient functioning. In this paper, the surge onset of a compressor while closing a downstream valve is studied. Various tests have been carried out varying the closing time, the position of the initial operating point and the volume of the circuit. The inlet and outlet signals of physical parameters are analyzed with spectral and temporal methods in order to define the instant of the surge occurrence.

The present study focuses on the inception, the growth, and the potential unsteady dynamics of attached vapor cavities into laminar separation bubbles. A viscous silicon oil has been used in a Venturi geometry to explore the flow for Reynolds numbers ranging from $Re=800$ to $Re=2000$. Special care has been taken to extract the maximum amount of dissolved air. At the lowest Reynolds numbers the cavities are steady and grow regularly with decreasing ambient pressure. A transition takes place between $Re=1200$ and $Re=1400$ for which different dynamical regimes are identified: a steady regime for tiny cavities, a periodical regime of attached cavity shrinking characterized by a very small Strouhal number for cavities of intermediate sizes, the bursting of aperiodical cavitational vortices which further lower the pressure, and finally steady super-cavitating sheets observed at the lowest of pressures. The growth of the cavity with the decrease of the cavitation number also becomes steeper. This scenario is then well established and similar for Reynolds numbers between $Re=1400$ and $Re=2000$.