The Compressed Air Engine
Using compressed air to drive an engine is not a new concept. Compressed air motors are widely used in hazardous areas and these tend to be a sliding vane mechanism that exhaust air to atmosphere thereby providing a simple rotary engine. The overall efficiency does not have to be high, the important issue is avoiding the potential for an ignition source.
However, there is a growing interest in the use of compressed air to propel motor vehicles. This allows a vehicle to be used in a densely populated area with the minimum of local emission. Generating the compressed air in the first place does consume energy and this energy is usually obtained from a fossil fuel source. Therefore the concept of a clean engine that runs on compressed air is a misnomer, all that is happening is the conversion from fossil fuel to motive power is one step removed from where the motive power is being used.
The generation of compressed air remains an expensive process, however it is possible to increase the overall efficiency of a compressed air driven engine by adopting fundamental design strategies. To this end, Cashflo Limited produced (on paper) the basis for a compressed air driven engine that has the potential to provide a high specific efficiency. First and foremost we are compressor design engineers and have simply looked at the problem from a lateral perspective. Like many problems, the solution was fairly simple but the application remains complex. The next step that involves producing the engine, is still a short way away.
In our opinion compressed air driven motor cars will not reduce our increasing demands for fossil fuel. This type of engine uses a tertiary form of energy conversion with associated losses through each stage of conversion. Our research indicates that one of the most important issues is energy control and energy recovery during both the compression and expansion stages. However, vehicles that use compressed air driven engines may have a place in society, where they will reduce local atmospheric pollution within large towns and city centres.