A steady state approach to calculation of valve pressure rise rate ...

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TechSoft Engineering & SVS FEM poppet modeled at 3 stroke positions detail of hexahedral mesh in control passage area pressure outlet (p case) velocity inlet Fig. 3. CFD model limits are set manually Fig. 4. Pressure contours and streamlines in control passage region (1 mm stroke, 70 lmin -1 flow)
Konference ANSYS 2011 4. Post-processing The post-processing plays big role in this task. We have data from 9 CFD calculations (3 strokes × 3 flow rates per each stroke = 9 calculations) in this specific example. Therefore further data processing in a spreadsheet or other suitable tool is needed. The input and output values can be collected into a table form for further processing. One table proposal is following: stroke flow rate pressure drop flow force Tab. 1. Proposed table for collection of CFD inputs and outputs The visualization of data points can be seen in Fig. 5. The triangle points in graph C represent dependency of the pressure drop on flow rate. The different colors relate to different poppet strokes. Similarly, the square points in graph B represent dependency of the flow force on flow rate. The data points can be approximated by quadratic polynomial trendlines (continuous colored lines in graphs B and C) for each the stroke value. The flow force at constant stroke can be then written in form: where , , and , (4) are polynomial coefficients obtained from the spreadsheet trendline properties. It is obvious the flow force has to be in balance with the spring force (2) at each the point of final pressure rise rate characteristic. Therefore we can write: Solution of this quadratic equation is: ( ) (5) √ ( ) , (6) where the sign plus or minus is chosen in way to obtain physically correct result. So, using (6) we get flow rate at which there is balance between flow force and spring force at constant stroke (compare graphs A and B in Fig. 5 to see balance between spring force and flow force for each the stroke) .
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A steady state approach to calculation of valve pressure rise rate ...

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