Method of improving the efficiency of a supercharged diesel engine
AssigneeSociete d'Etudes de Machines Thermiques S.E.M.T.
InventorRemi Curtil
Life of this patent
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Abstract
The invention relates to a method and a device for improving the efficiency of a four-stroke-cycle internal combustion engine. The main purpose of the invention is to obtain an effective compression ratio that is capable of automatic variation without introducing additional elements whatever the load, but only by adapting the engine cycle timing diagram. Said timing diagram includes an overlap stage between the lifts of at least one exhaust valve and at least one intake valve, said intake valve being closed near or before the bottom dead center of the piston, and said exhaust valve being closed beyond the instant of fixed closing of the intake valve.
Claims6
A method for improving the efficiency of a four-stroke-cycle supercharged diesel engine of constant pressure type, having a timing diagram which is constant in the engine cycle, including an overlap stage between the lift of at least one intake valve and at least one exhaust valve, the method comprising
- closing tbe intake valve, in accordance with the Miller cycle, at a crankshaft rotation angle between 40.degree. before bottom dead center and 10.degree. after bottom dead center in order to automatically modulate the trapping efficiency of the engine cylinders,
- at the end of said overlap stage partially closing the exhaust valve,
- maintaining a partial lift of said exhaust valve during a major part of the intake stage, and
- closing said exhaust valve beyond the instant of said intake valve closing, in order during gradual increase in engine load, to automatically and gradually reduce, from starting to nominal power, the effective compression ratio and the temperatures at the end of compression by concomitantly reducing the amount of gas or fresh air present in the exhaust conduit and consisting of burned gases or air reintroduced into the cylinder near bottom dead center, according to the natural variation of the relationship between the supercharging air pressure and the counter-pressure at the cylinder exhaust.
A method for improving the efficiency of a four-stroke-cycle supercharged diesel engine of constant pressure type, having a timing diagram which is constant in the engine cycle, including an overlap stage between the lift of at least one intake valve and at least one exhaust valve, the method comprising
- closing the intake valve, in accordance with the Miller cycle, at a crankshaft rotation angle between 40.degree. before bottom dead center and 10.degree. after bottom dead center in order to automatically modulate the trapping efficiency of the engine cylinders,
- at the end of said overlap stage closing the exhaust valve,
- maintaining the exhaust valve closed during a major part of the intake stage,
- partially reopening the exhaust valve before the intake valve closing, and
- reclosing the exhaust valve beyond the instant of said intake valve closing, in order during gradual increase in engine load, to automatically and gradually reduce, from starting to nominal power, the effective compression ratio and the temperatures at the end of compression by concomitantly reducing the amount of gas or fresh air present in the exhaust conduit and consisting of burned gases or air reintroduced into the cylinder near bottom dead center, according to the natural variation of the relationship between the supercharging air pressure and the counter-pressure at the cylinder exhaust.
Dependencies are inferred from the claim text.