In this work a Computational Fluid Dynamic (CFD) analysis was applied to the design and optimization of a novel concept roto-translating (RT) valve.
A Roto-Translating valve is a spool type valve assembled to a moving sleeve. The two parts are controlled by two independent actuators and are placed inside the valve body. The valve features both basic logic functions (AND, OR), and advanced control techniques. From the safety viewpoint it offers a fail-operational characteristic thanks to operational redundancy and functional diversity. Moreover the control flexibility allows to get rid of the need of a specific spool design for each different application. One of the goals of the valve is to enhance the speed and precision achievable by the use of two concurrent actuators; for this reason it is fundamental to study the flow forces effect that could adversely affect both rotating and linear motion.
In the field of hydraulic valves design the Flow Force, generated by the acceleration of fluid flow across the metering edges, is an important phenomenon to be considered for the study of the operation and dynamics of the valve. Differently from common spool valves, in this new kind of valve two types of reaction to fluid flow are present: the Flow Force and the Flow Torque.
The first is the well-known axial Flow Force which is generated from the variation of axial component of momentum of the fluid flow and was studied by several authors. The second type of reaction can be identified as a Flow Torque, a less investigated argument. Basically the Flow Torque, equivalently to Flow Force, is linked to the variation of the component of fluid momentum, but in this case in circumferential direction and effects the mutual rotation of the two metering elements.
A complete map of operative conditions, 5 angular positions and 5 linear displacements have been investigated, simulating all the combinations of 4 different pressure ranges. This approach generates a quite large matrix of 25 results for each of the 4 working pressure conditions. For each run the pressure and velocity gradients have been recorded and the flow and torques forces have been computed. These data allow the validation of the sizing of both electric valve actuators, in order to define the operational limits of the valve in terms of pressure drop and flow rate. This activity could also inspire new solutions for a further geometric optimization of the design.
