Allowing for sonic flow in the valve using SVHIM

2 Allowing for sonic flow in the valve using SVHIM 

The full set of the above equations cea.ses to be valid when the flow in the valve goes sonic, since at this point there is a physical decoupling of the conditions upstream and downstream of the valve. In particular, the relationship between the ratios of throat and valve outlet pressures to valve inlet pressure given in equation (10.40) will hold no longer. Hence it will be necessary to detect the onset of sonic flow, which will occur when p,/p,., as calculated from equation (10.39), is equal to the critical pressure ratio, rc = (2/(y+ )) / . We may then use the procedure outlined in Section 10.2.3. to calculate flow and conditions when the flow in the valve has become sonic. This is exactly the same procedure as 

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