Stage Count and Interstage Temperature Estimator

Stage count is the largest single cost driver on a high-pressure frame, because every added stage brings another cylinder, cooler and valve set. This estimator works the other way round from a quotation: give it the pressure ratio you need and it shows how many stages that ratio forces, what each stage then has to do, and how hot the air leaves a stage before intercooling.

The estimator splits the overall ratio evenly between stages and uses the adiabatic relation for air with a ratio of specific heats of 1.4, which is the standard textbook idealisation and runs hotter than a real cylinder with cooled walls. It is a planning aid, not a thermal design: real stage splits are set by cylinder sizes, rod loading and valve temperature limits, and the built machine follows the general arrangement drawing issued with your quotation. Our published air frames run three stages at 8 MPa and four stages at 15 MPa, which is what this method predicts at a 4.5 ratio limit.