Internal-combustion engines – Adjustable combustion chamber – Piston in head adjusted
Reexamination Certificate
1999-10-04
2001-11-20
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Adjustable combustion chamber
Piston in head adjusted
Reexamination Certificate
active
06318308
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to diesel engines and, more particularly, to medium speed diesel engines operated with retarded fuel injection timing relative to conventional fuel injection timing.
In a diesel engine, liquid fuel is injected into a plurality of engine cylinders full of compressed air at high temperature. The fuel is broken up into droplets, which evaporate and mix with the air in the cylinders to form a flammable mixture. Traditional concerns for diesel engine manufacturers include fuel efficiency and smokeless operation, both of which relate to the quality of combustion in the cylinders.
The generation of some engine exhaust emissions, including carbon monoxide (CO), particulate matters (PM), and smoke, is related to a large extent to the ending time of the fuel injection duration during each piston cycle. Generally speaking, the earlier the fuel injection duration ending time, the less smoke and PM are generated in the combustion cycle. In some applications of medium speed diesel engines, such as for diesel locomotive operation, fuel injection timing, i.e., the start of the fuel injection duration, is set early in the cycle for full load smokeless operation. By applying early fuel injection starting time, the fuel injection duration ending time also occurs earlier in the piston cycle, which reduces PM, CO and smoke emissions. However, early fuel injection timing increases engine cycle temperature. Consequently, exhaust emission of nitrogen oxides (NO
x
) is relatively high.
One of the most effective ways to reduce emissions of NO
x
, a major concern to diesel engine manufacturers, is to retard fuel injection timing relative to conventional fuel injection timing, which results in a later fuel injection duration ending time, which, in turn, causes incomplete and untimely combustion in the cylinders, reduces engine efficiency, and increases generation of CO, PM, and smoke. Moreover, retarded fuel injection timing lowers the firing pressure in the cylinders, which under-utilizes the structural capability of the engine.
Decreasing the fuel injection duration time, which results in an earlier fuel injection duration ending time, can alleviate CO, PM and smoke emissions despite retarded fuel injection timing. However, increased fuel consumption will still result due to low cycle efficiency associated with untimely combustion from the retarded fuel injection timing.
Accordingly, it would be desirable to provide a diesel engine for operation at retarded fuel injection timing to reduce the generation of NO
x
without compromising engine efficiency and without incurring reduced cylinder firing pressures, therefore more fully utilizing the structural capability of the engine, and curbing the generation of CO, PM and smoke emissions.
BRIEF SUMMARY OF THE INVENTION
In an exemplary embodiment of the invention, an engine block defines at least one cylinder and a cylinder head. A combustion air intake port and an exhaust gas port extend through said cylinder head for introducing combustion air into the cylinder head through a combustion air intake valve, and for expelling exhaust gases through an exhaust gas valve. A piston is slidably disposed in said cylinder and includes a specially shaped piston crown surface that reduces a clearance between the piston and the cylinder when the piston is at a top-dead-center position, thereby increasing the compression ratio of the engine. A valve cam shaft opens and closes the combustion air intake and exhaust valves within the specially designed combustion air intake and exhaust gas ports within the reduced valve-to-piston crown clearance. Therefore, collisions between the valves and the piston crown surface are avoided while scavenging flow of exhaust gases is enhanced.
More specifically, and in a particular embodiment, a piston crown surface has an outer edge, a depressed portion relative to the outer edge, and an elevated portion relative to the outer edge. The elevated portion is centered with respect to a longitudinal axis of the piston, with the crown surface depressed around the elevated portion. The piston crown surface reduces the clearance between the crown surface and the cylinder head when the piston is in the top-dead-center position, while the depressed portion facilitates a desired fuel injection jet flow behavior and combustion performance. The relative proportions of the convex elevated portion and the concave depressed portion are such that the compression ratio of the cylinder is increased by a specified amount to produce a higher cylinder firing pressure within allowable firing pressures that for which the cylinder was designed.
A specially designed combustion air intake port and exhaust gas port in the cylinder head include passages that decrease in cross-sectional area from the cylinder head through the ports and enhance scavenging flow of exhaust gases. The combustion air intake and exhaust gas ports also allow for combustion air intake valves and exhaust gas valves to be opened and closed with a valve cam shaft adapted for manipulating the valves without contacting the piston crown surface. In different embodiments, the passages are formed by a plurality of tapered bores, a plurality of bores with curved sidewalls, or a combination of tapered bores and bores with curved sidewalls.
The above described engine therefore allows for reduced emissions of NO
x
via operation with retarded fuel injection timing, while improving engine performance and efficiency and utilizing the full structural capability of the engine.
REFERENCES:
patent: 4187823 (1980-02-01), Brown, Jr.
patent: 4660383 (1987-04-01), Leonard
patent: 4791259 (1988-12-01), Pfaffmann
patent: 4873947 (1989-10-01), Ryan, III et al.
patent: 5363820 (1994-11-01), Neitz
patent: 5692464 (1997-12-01), Kimura
patent: 5868112 (1999-02-01), Mahakul et al.
patent: 5873341 (1999-02-01), Smith, Jr. et al.
patent: 5913960 (1999-06-01), Fletcher-Jones
Chen Gong
Hsu Bertrand Dahung
Ali Hyder
General Electric Company
Rowold Carl A.
Spinks Gerald W.
Yuen Henry C.
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