Optimal design of a novel ‘S-shape’ impeller blade for a microbubble pump

Abstract

The newly designed impeller blade, a so-called novel ‘S-shape’ blade, used for microbubble pumps has been introduced to enhance pump performance. Unlike a conventional blade having separated blades, like cantilever-shape blades, the newly designed impeller has a continuous blade, thus having a relatively robust structure as compared to a conventional impeller. The optimal blade design of the ‘S-shape’ blade has been demonstrated to obtain a higher pump efficiency. To analyze the three-dimensional flow field inside the pump by numerical simulation, a general analysis code, ANSYS CFX, is employed in the present work. The computed pump efficiency has a maximum error of 4 percent compared to the experimental data. The optimal design of the pump impeller blade is based on geometric constraints considering blade manufacturing, and uses three design variables: the number of blades, the blade thickness and the radius of the blade rib. The response surface method, a global optimization method, is employed to optimize the pump impeller blade. Throughout the blade optimization of the ‘S-shape’ blade, it is found that the chief influence on the pump efficiency is the number of the impeller blades. Pump efficiency, an object function, is increased by up to 35.3 percent, which corresponds to a 3.7 percent increase compared to the reference one. It is no use to say that the ‘S-shape’ blade having a continuously connected blade has more rigid characteristics. The larger pressure increases of the optimized pump along with the volute casing wall is observed from the middle position of the rotational direction, which comes from the increase of momentum energy due to larger circulating flow inside each blade passage as compared to the reference one. The detailed flow field inside the pump blades is also analyzed and compared.