15th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
Authors
Abstract
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.
ETC2023-203