Abstract: An annular expansion ring centered on a main axis and suitable for being mounted on a fuel injector coaxial with the ring is disclosed. The ring presents holes that are distributed around the main axis and open out into its upstream face to enable air to pass towards the zone that is downstream from the ring. The ring includes a conical annular groove that converges downstream, that is open downstream, and that has the holes opening out into the upstream portion thereof. The axis of each of the holes makes an angle relative to the main axis that is strictly greater than the angle between the generator line of the cone defining the annular groove and the main axis, such that the air exiting from the holes impacts against the inner wall of the annular groove, i.e. its wall that is closer to the main axis.

Abstract: In a method of operating a scroll compressor at startup, the compressor is rotated in reverse for a brief period of time. The compressor is of a type which does not compress liquid when rotated in reverse. The purpose is to boil off the liquid refrigerant from the oil by heating and agitating the mixture of oil and refrigerant in the oil sump. This results in much more benign forward start as no refrigerant is drawn into the scroll compressor pump and the amount of oil pumped out of the compressor on start up is minimized. Also, the viscosity of oil is increased and lubrication of the bearings is improved. After a short period of time reverse rotation is stopped and the compressor can begin to be driven in the forward direction.