Flow at partial valve openings

We may define the (fractional) valve opening, y, as the ratio of the current flow, W, to the flow, Wlmax, that would pass at fully open, given the same upstream conditions and throat pressure  

Combining equation (9.3) with equation (9.15), the gas flow through the control valve with limiting gas conductance, Cg (1.4), at the current valve opening is given by  

Figurt 9.7 Maximum differenca between tomb and Up, as a function of friction coefficient, Cigb- 

Substituting from equations (9.34) and (9.36) into equation (9.33) gives the valve opening as the ratio of the current Cj(-value to its value at fully open  

Substituting from equation (9.37) back into equation (9.34) gives the flow at valve opening, y, as  

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