Rapid Design and Evaluation of Swing-Type Check Valves
Summary
The Theoretical and Applied Fluid Dynamics Laboratory (TAFLab) at the University of California, Berkeley is investigating several designs for novel shallow water wave energy converters. The common denominator for these prototypes is that they operate with a hydraulic power takeoff (PTO) for the secondary power conversion. A critical component of an hydraulic PTO is one or more check valves creating a unidirectional flow. The research goal of this thesis is the flow optimization of these components. Turbulence in the check valves was assumed to be a major cause for efficiency losses in the current PTO design.
Computer Aided Design (CAD) and rapid prototyping through Fused Deposition Modeling (FDM) were selected as prototyping tools, due to the high customizability and short lead time of components. Experimental analysis and fluid simulations were used to compare and verify the performance of the optimized check valve designs.
One of the performance measures for check valves is the head loss coefficient Kv, which is desired to be low in the flow direction, and high in the reverse direction. We observed that the original check valve had a KvD = 57.2+-1.0 in the flow direction and no flow in the reverse direction (KvR = inf). A minor modification improved KvD to 46.1+-0.9 in the flow direction but decreased KvR = 8.7+-1.7.10E7 in the reverse direction. The first double door design brought KvD
down to 6.4+-0.5, but with a reverse loss coefficient of 738+-11. The final double door check valve had a KvD of 8.4+-0.5 in the flow direction and KvR = 1.4+-0.3.10E6 in the reverse direction, and was selected for a dynamic test.
In a direct application in a pumping setup, we however observed an efficiency decrease from 41.3+-0.5% to 24.7+-0.5%, possibly explained by the closing speeds of the new valve. It is concluded that optimizing losses in a steady state flow experiment cannot guarantee improved results in pulsating or alternating flow.