Efficiency Increase in Centrifugal Compressor With Open Impeller by Using Curvilinear Element Blade

Abstract

The effect of curvilinear element blade on open-type centrifugal impeller is numerically examined in this research. We compared four different open-type centrifugal impellers. Two of them were linear element blade impellers: one has a positive tangential lean to the rotation at the outlet and the other has negative tangential lean. The other two were curvilinear element blade impellers having different tangential lean profiles. Numerical simulation of steady flow was conducted in one-blade path model with inlet, impeller and vane-less diffuser regions. The simulation confirm that impellers with negative tangential lean profiles improve the stage efficiency under the flow rate at the design point and the curvilinear element blade improve the stage efficiency not only at the design point but the lower flow rate regions also. The efficiency increase at the design point is obtained not in the vane-less diffuser region but in the impeller region since the negative lean profile reduce the tip-leakage loss near the impeller outlet region. The negative tangential lean profile changes the pressure distribution in the flow passage between two impeller blades. The pressure difference between the pressure surface and the suction surface of one blade near the tip region decrease because of the pressure distribution change. Hence, the mass flow rate of the tip leakage decreases and reduces the loss generation. In addition, the reason why the stage efficiency increases under the lower flow rate conditions by using curvilinear element blade is the suppression effect of the flow separation in the vane-less diffuser. This result indicates that there is a design criteria both tangential lean angle and the inflection point of the profile from positive to negative to suppress the flow separation at the hub side in the vane-less diffuser.

Influence of blade geometry on secondary flow development in a transonic centrifugal compressor

“…The authors concluded that an efficiency increase of about 1.5% was mainly achieved due to a shock strength reduction in the inducer of the impeller. Another remarkable optimization of a process gas compressor with a shrouded impeller was made by Hiradate et al (2014), which was later experimentally verified by Tsukamoto et al (2015). Due to the use of curvilinear blade stacking and thus a modification of lean, an efficiency improvement of 2.1% could be achieved.…”

Investigation on Aerodynamic Performance of a Centrifugal Compressor with Leaned and Bowed 3D Blades

“…Efficiency and pressure ratios are influenced by various factors, such as the velocity coefficient, energy head coefficient, rotational speed, blade height, inlet radius, and radial distance [19]. A comparative study of different blade types revealed that impellers with a trailing edge bend opposite to the rotating direction reduced the pressure difference near the blade tip, thereby minimizing tip leakage loss and improving compressor performance [20].…”

Effects of impeller blades with bow trailing edge on centrifugal compressor performance

“…However, just as the author said, the static pressure distribution at cross section in blade passage is not enough to support the explanation. Tsukamoto et al (2015Tsukamoto et al ( , 2019 studied the effects of the bow trailing edge on an open-type impeller, and the efficiency improvement of the impeller and vaneless diffuser was attributed to the blade force brought by the positive bow to reduce the tip leakage flow at the impeller outlet. Mosdzien et al (2018) and Wittrock et al (2018) improved the performance of two different centrifugal compressors by using bow impeller blades generating from numerical optimize method.…”