Abstract: The method of energy conversion consists in burning a fuel in an oxidizing gas in order to admit the combustion gases into an expansion machine for delivering mechanical energy, in previously compressing the oxidizing gas in a positive-displacement compressor driven by the expansion machine, in injecting into the compressor a sealing and/or lubricating auxiliary liquid which is continuously cooled and separated from the compressed gas, then re-injected into the compressor. The auxiliary liquid is cooled by vaporization of water and the steam produced is entrained in the stream of compressed oxidizing gas.