Design of a miniature pump
Lieu, Chee Fui
Date of Issue2013
School of Mechanical and Aerospace Engineering
The applications of pumps are becoming increasingly extensive and there are more application-specific constraints that are imposed on pump designs, including constraints in size and capacity. Thus, miniature pumps have gained their popularity in many industries such as pharmaceutical, medical, MEMS applications etc. The design and development of a miniature pump is necessary to serve these applications. However, miniaturization process is both difficult and challenging. In this project, a miniature pump with better performance has been designed and developed. Several designs are discussed and explored and the reciprocating ball pump (RBP) is proposed. The working principle of the RBP is presented. The RBP is unique in that it does not require any valves to regulate flow and inherently produce unidirectional flow. In addition, the design of this pump is simple, compact and easy to fabricate. Besides that, this pump has potential in pumping fluid with minimal contamination because the pumping unit is small in size and it does not require a seal and bearing. Furthermore, it has the potential in generating a higher flow rate as compared to the conventional reciprocating pump. The final RBP is 19.5 mm long, has a diameter of 18.8 mm and weighs less than 25 grams. In this research project, a mathematical model has been developed with some assumptions and simplifications to reveal the working principle and to evaluate the performance of the RBP. It also enables the prediction on the instantaneous flow rate and pressure variations upstream and downstream of the RBP. In addition, parametric studies have been conducted to determine the effects of the weight of the ball and thesize of the pumping unit on its performance. In addition, parametric studies show that the optimal RBP has a casing length of 11.5 mm, a ball of diameter 9.6 mm with a rear cap hole diameter of 8.5 mm. CFD simulation with fluid-structure-interaction (FSI) of the RBP has been successfully conducted via ANSYS-FLUENT by using moving and deforming dynamic mesh model with user-defined-function (UDF). Asides from revealing the working principle and the performance of the RBP, CFD simulation also shows the working principle of the RBP in a more comprehensive manner through the pressure distribution and velocity flow field. Subsequently, the functionality of the RBP has been verified by experimental studies. In addition, a modified test rig was used to conduct flow visualization experiments. The mathematical model and CFD simulation have been validated by the experimental performance characteristic and flow visualization studies as they agree qualitatively with the results obtained from both mathematical model and CFD simulation. The three studies show that the RBP generates additional induced flow especially during its backward stroke even though the RBP is operated at a back pressure of as high as 1000 Pa. This proves that the RBP is superior to a conventional reciprocating pump having the same dimensions. The RBP has a flow efficiency of as high as 172.15%, 170.88% and 159.90% which are measured through mathematical model, CFD simulation and experimental studies respectively.
DRNTU::Engineering::Mechanical engineering::Fluid mechanics