Abstract: An internal combustion engine comprising a piston (1) having a recessed combustion bowl (3) with a raised projection (4) in the floor of the bowl so as to define an annulus with the sides of the bowl, swirl means to cause the inlet air to rotate about said raised projection, and a fuel injector (2) having orifices that spray a plurality of jets into the annulus at spaced points around the projection (4), the cross-sectional area of the annulus being such as to vary around the projection (4) and to have a minimum value in a median plane (D--D) through the axis (C) of the projection (4), and the injector nozzle (2) being located in a central region of the bowl (3) and having orifices orientated so as to direct jets of fuel both sides of said median plane. The cross-section area of the annulus is varied by varying the radial width of the annulus, this being achieved conveniently in a circular bowl by offsetting the axis (C) of the projection (4) radially from the axis of the bowl (A).