Patent ID: 7225762

Claim:
In a method spraying an aqueous liquid into a duct ( 2 ) to a turbocharger ( 4 ) for intake air of a turbocharged piston engine ( 1 ) for humidifying the intake air, whereby to reduce nitrogen oxide emissions from the engine, the improvements wherein: in a first stage, the intake air is heated by a heat exchanger element ( 5 ′) before the turbocharger and first of the aqueous liquid is first injected as a mist into the heated intake air through at least one first nozzle ( 9 , 10 ); and in a second stage, the first-injected intake air is compressed by the turbocharger ( 4 ), causing its temperature to rise, and second of the aqueous liquid is second injected as a mist into the compressed intake air through at least one second nozzle ( 12 , 13 ).