Abstract: A homogeneous charge compression ignition engine comprising an air intake passage, a combustion chamber connected to the air intake passage, and a partial oxidation device is disclosed. The partial oxidation device comprises a housing including a fuel inlet, an air inlet, an outlet, a mixing chamber and a burning chamber. The air inlet is connected to the air intake passage and the outlet is also connected to the air intake passage. A source of ignition is attached to the housing for causing ignition of a portion of a fuel-air mixture supplied to the housing. A partially oxidized fuel is produced as the combusting fuel-air mixture is rapidly quenched upon exiting the outlet of the housing and entering the air intake passage. Different structures for achieving rapid quenching are discussed and different air supply strategies are also presented. Further, another structure for producing a partially oxidized fuel using a low temperature chain propagating reaction is included.