Nozzle for cooling engine pistons

A cooling jet nozzle for an engine piston, in which the cooling jet nozzle comprises:

• a cooling stream pathway, in which internal cross-sectional dimensions of the pathway vary along a length of the pathway;
• and a plunger located within the cooling stream pathway to impinge a cooling feedstream received within the pathway to provide a cooling jet, characterized in that the plunger is axially moveable in order to adjust the internal cross-sectional dimensions of the cooling jet;
• wherein
• the cooling stream pathway is provided by a first cylindrical pathway portion in communication with a second cylindrical pathway portion, in which the second cylindrical pathway portion provides a jet nozzle outlet, the plunger is moveable between a first open position in which the plunger is located within the first cylindrical pathway portion to provide a first cooling jet, and a second open position in which the plunger is at least partially engaged within the second cylindrical pathway portion to provide a second cooling jet stream,
• wherein the plunger has a first axial end located on a side of the jet nozzle outlet;
• the jet nozzle outlet has an inside diameter, and in the second open position of the plunger, said first axial end is located at a distance from the jet nozzle outside outlet that is less than one-half of said inside diameter, said distance is inferior to one-quarter of said inside diameter wherein said distance is measured in a direction of flow of the cooling jet.