Compressed Air Engine Calculations

AI Thread Summary
The discussion focuses on calculating power and torque values for a single-cylinder compressed air engine operating at a constant inlet pressure of 9 bar. The user seeks assistance with their calculations, which appear inconsistent with MATLAB and experimental results. Clarifications are requested regarding the engine type, specifically whether it is a reciprocating engine or a continuous flow machine. The conversation highlights the need for more realistic assumptions in the calculations, particularly regarding the expansion process and the filling and exhaust cycles. Overall, the thread emphasizes the importance of accurate modeling for effective performance predictions in compressed air engines.
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I have done some calculations to obtain power from the engine but don't think they are correct. Also need some help calculating torque at different rpms and air tank emptying time.
Hi, I posted a question a while ago which I have managed to do some more calculations for. I need a bit of help to see if they are correct. I am trying to obtain power and torque values at different rotational speeds of a single cylinder compressed air engine. The inlet pressure into the engine is a constant 9 bar and the air is discharged from the chamber as the piston reached BDC rather than a conventional cam valve design. My calculations below for power do no seem right compared to MATLAB and experimental results.

I have attached screenshot as it will not let me post equations into this.

I would like to get torque values at different rpms and also any formulas to calculate how quickly a air tank would empty at a specific rpm.

Much appreciate the help.
 

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What sort of engine do you have in mind? Is it a reciprocating machine employing a slider-crank mechanism or a continuous flow machine like an air turbine? You need to tell us more about what you are contemplating before much can be said about your calcs.
 
Dr.D said:
What sort of engine do you have in mind? Is it a reciprocating machine employing a slider-crank mechanism or a continuous flow machine like an air turbine? You need to tell us more about what you are contemplating before much can be said about your calcs.
It would like a reciprocating engine
 
You use of the constant k = 1.4 seems to imply an adiabatic expansion. In fact, it will be more nearly a polytropic expansion, k = 1.35 roughly.

The other problem I see is that you have assumed a very idealized cycle, with instantaneous fill and exhaust; this is not how it actually happens.
 

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