# Compressed Air Engine Calculations

• karan_s
In summary: NfO2-GfzA&t=145sIn summary, your calculations for power and torque at different rotational speeds for a single cylinder compressed air engine do not seem to match experimental results. You may need to provide more information about what you are planning to do with the calculations. Additionally, you should consider how the engine operates in order to provide an accurate evaluation of expansion and flow.
karan_s
TL;DR Summary
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.

## 1. What is a compressed air engine?

A compressed air engine is an alternative type of engine that uses compressed air as a source of energy to power a vehicle or machinery. It works by storing compressed air in a tank and releasing it to drive a piston or turbine, which then generates mechanical energy.

## 2. How do you calculate the efficiency of a compressed air engine?

The efficiency of a compressed air engine can be calculated by dividing the work output by the energy input. The work output can be calculated by multiplying the force applied by the distance the piston or turbine travels. The energy input is the amount of compressed air used, which can be measured by the pressure and volume of the compressed air tank.

## 3. What factors affect the performance of a compressed air engine?

The performance of a compressed air engine can be affected by several factors, including the pressure and volume of the compressed air, the design and size of the engine, the type of valves and pistons used, and the efficiency of the air compressor used to fill the tank. The temperature and humidity of the air can also affect the performance of the engine.

## 4. How does a compressed air engine compare to a traditional combustion engine?

A compressed air engine is more environmentally friendly compared to a traditional combustion engine because it does not emit any harmful pollutants. It also has a simpler design and requires less maintenance. However, it has a lower energy density and may not be suitable for heavy-duty applications.

## 5. Can a compressed air engine be used in everyday vehicles?

Currently, compressed air engines are not widely used in everyday vehicles due to their lower energy density and limited range. However, they are being explored as a potential alternative for short-distance transportation, such as city buses and delivery trucks. With further advancements in technology, it is possible that compressed air engines could be used in everyday vehicles in the future.

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