From nozzle-flapper to complex valves: Design based on flow characteristics

In this study, flow models originally developed for nozzle-flapper valves are generalized to investigate the flow dynamics in more complex valve geometries. A method is introduced to compute flow and discharge coefficients, which are crucial for optimizing the efficiency and performance of valves operating under high-speed and highpressure conditions. The proposed models are validated through experimental tests and CFD simulations, providing valuable insights into valve behavior and offering improved design methodologies for highperformance applications. The model accurately captures the peak of the flow coefficient curve and highlights the dominant loss mechanisms within the valve. The results show that flow contraction losses, which contribute to the reduction of the flow coefficient at lower valve lifts, are more significant than expansion losses. Moreover, losses are found to be larger at the gaps between channels or at the inlet ducts, depending on the sealing element configuration. Experimental and CFD results confirm the predictive capability of the proposed flow model, particularly at higher valve lifts. Discrepancies observed at lower lifts are attributed to differences in boundary conditions but are properly accounted for in the fitted models. Overall, the flow coefficient behavior follows a predictable trend, with peak performance occurring at a critical lift, after which the valve transitions from nozzle-like to orifice-like behavior.