31 May 2009

An idea to increase power/efficiency of a Natural Gas (CH4) Internal Combustion Engine (ICE).

While I was driving to In-N-Out, earlier today, an idea struck me as to how to improve the performance of a Natural Gas powered Internal Combustion Engine...

Essentially, the waste gases of a natural gas engine is water vapor and carbon dioxide with trace amounts of other pollutants.
A major waste product of the engine is heat, especially excess heat in the exhaust gasses. What do I define as excess heat in the exhaust? Quite simply it is heat above the point required to keep the water content of the exhaust in its vapor phase. At standard atmospheric pressure, it would be 100ºC. With an engine with a 12:1 compression ratio, this temperature would be at least 182ºC, plus a bit more for the motive power of the engine - so lets say around 200ºC.

The exhaust gases could be condensed to form mildly acidic but otherwise pure water. This water could be warmed by the engine's cooling system up to equal the temperature of the engine block, which would be a little under 100ºC. At the point of the engine cycle just after the intake valves close at roughly the point where compression begins, a small amount of this warmed water could be injected as a fine aerosol spray. The subsequent combustion of the natural gas could provide enough energy to also change the injected water into its vapor phase, increasing the post-combustion pressure within the engine, providing more motive power.

The key thing to do would be to monitor the temperature of the exhaust from the engine to ensure that there is excess heat within the system to vaporise the injected water so that the water is not injected at a time when there is insufficient energy to support it as it would likely result in reduced engine performance.

How well would this perform? Well, to be honest, I have not run any detailed numbers but I don't think it would be too far fetched to imagine this improving power by as much as 10%, maybe even significantly more. Increased performance would mean less time spent accelerating and perhaps less fuel to maintain steady velocity which both would mean significant gains in fuel efficiency.

What other uses for the condensed water can I think of? Perhaps some form of evaporative cooling system for the intake air? Another idea to entertain.

If only I had the time to play...
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