Performance Curves, and Other Measurements in Jet Systems

Calculations, Performance Curves, and Other Measurements in Jet Systems 

We have discussed the American system inches of mercury (in Hg) in Chap. 6, How Instruments Work. Of more immediate interest is Table 16.1. To do any sort of vacuum calculation, we need to convert to the absolute system, in millimeters of mercury (mm Hg). Unfortunately, we also need to correct measurements made with an American-type, (in Hg) vacuum gauge, for atmospheric pressure. You can interpolate between the two sets of data in Table 16.1, to correct for almost the entire range of typical atmospheric pressures. 

Actual atmospheric pressure = 29.97 in Hg Actual atmospheric pressure = 25.00 in Hg  

We will need to use this table to calculate a jet s compression ratio, when we measure vacuum pressures with an American-type (in Hg) gauge. 

When considering the performance of a vacuum jet, we must first consider the jet s overall compression ratio. To calculate a jet s compression ratio  

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