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.

Enhancing the turbomachines characteristic has been always a challenge in the last decades for scientists and industries. It results in passing the conventional single-rotor turbomachines and designing multi-rotor configurations. There are some researches focused on the pump with two independent rotors, mostly on the axial pumps to increase reliability, efficiency, static head, and also reduce the energy consumption. Although there is a huge lack of study in two independent centrifugal rotors and there is no study on the inducer and centrifugal impeller with the ability to independent rotation. The authors designed and investigated the effect of independent rotation of an inducer on the characteristic of centrifugal impeller for the first time both experimentally and numerically. The inducer is an axial impeller with a low head coefficient that can avoid unexpected cavitation at upstream of the centrifugal impeller by increasing the inlet pressure of the impeller. In conventional configuration not only, the distance between inducer and impeller is always fixed but also the inducer is rotated with the same speed and direction as the centrifugal impeller. Whereas, using a new configuration that makes the inducer rotate independently from the main impeller can lead to considering the rotational speed and distance between inducer and impeller. The total static head, efficiency and inlet pressure of the centrifugal impeller are affected by the rotational speed of inducer and distance between the inducer and impeller and controlling these parameters results in more ability to configure the turbopump and reach more efficiency, static head and less chance of cavitation. In this paper, the effect of distance between inducer and centrifugal impeller which rotates independently in both co-rotation and counter-rotation mode in turbopump has been investigated numerically. At first, the numerical results for the centrifugal impeller are validated by an experimental test. Two inducers with the same geometrical characteristic with inverse tip angle are designed duo to rotate in both co-rotation and counter-rotation mode. Three bladed inducer with the outer diameter (Dio) of 78 mm and tip clearance of 1mm is applied upstream of six bladed centrifugal impeller with the inner diameter of 80 mm. The SR is defined as the speed ratio which is the speed of inducer (N1) to the speed of centrifugal impeller (N2) and L is the distance between inducer and impeller. These two parameters are defined as the study parameters. The L is considered as three different values: L≤ 2 mm, L = 0.5Dio and L = 1Dio. The SR is applied as SR= 1 in co-rotational mode and SR=-1 for counter-rotational mode for each distance.

Centrifugal pumps, consisting of an inducer and impeller, are used in various industries such as marine, aerospace, and nuclear. Typically, inducers and impellers in centrifugal pumps are fixed on the same shaft, having the same rotation direction and speed. Thanks to the use of independent rotation technology for the inducer and impeller, each can be rotated simultaneously at different speeds and in different directions. This article investigates the impact of varying the speed ratio between the inducer and impeller on the cavitation performance of centrifugal pumps equipped with an inducer as an innovative concept of allowing the rotors to rotate independently. Two inducers with identical geometry with opposite rotation directions are used to study the impact of speed in both corotation and counter-rotation modes. The cavitation performance of each mode has been analyzed for three different flow rates at varying inducer speeds. The development and structure of different types of cavitation occurring both in the inducer and in the space between the inducer and the impeller have been analyzed using a high speed camera. The findings indicate that the inducer in counter-rotation mode demonstrates enhanced cavitation performance. Increasing the speed ratio of the inducer relative to the impeller in this mode significantly improves the pump cavitation performance at different flow rates, while in the corotation mode, increasing the speed results in the cavitation performance drop.