Fluid sprinkling – spraying – and diffusing – Fluid pressure responsive discharge modifier* or flow... – Fuel injector or burner
Reexamination Certificate
2000-01-12
2001-07-17
Scherbel, David A. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Fluid pressure responsive discharge modifier* or flow...
Fuel injector or burner
C239S088000, C239S095000, C239S132500, C239S124000, C239S533300, C239S533110
Reexamination Certificate
active
06260776
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to fuel injectors, and more particularly high pressure gaseous fuel injectors for internal combustion engines.
BACKGROUND OF THE INVENTION
The natural gas transmission industry and chemical process industries use a large number of large-bore, 2-stroke and 4-stroke natural gas engines for compressing natural gas. For example, industries use these engines for such purposes as maintaining pressure in the extensive network of natural gas pipelines that supply residential housing and commercial businesses. The network of natural gas pipelines typically operate at high pressures in the neighborhood of between 500 psig and 1000 psig.
These large-bore, natural gas engines may be powered by a small portion of the natural gas passing through the pipelines. However, before being injected into the engine, the pressure of the gas is significantly and substantially reduced. Gaseous fuel is typically injected into these cylinders at low pressures (for example, 15 psig to 60 psig by mechanically actuated fuel injectors, such as that disclosed in Fisher, U.S. Pat. No. 4,365,756. The problem with low pressure injection is that the fuel pressure provides little kinetic energy with which to induce cylinder charge mixing. There is ample evidence that the fuel and air in these large bore engines are not well mixed and as such exhibit poor combustion stability, high misfire rates and significant cycle-to-cycle variations in peak pressure. As a result, these engines are not efficient and also are environmentally detrimental, contributing to approximately 10% of the total NO
x
production in the United States from stationary combustion sources according to estimates.
The concept of using high pressure fuel delivery to enhance fuel mixing in these engines has been proposed as a means to improve efficiency and environmental emissions from these engines. However, retrofitting existing engines provides a significant hurdle because these engines are manufactured by different companies and also vary in size. Moreover, injecting fuel at high pressure as opposed to low pressure requires the fuel injectors to operate under extremely high operating pressures which in turn greatly increases stresses and powering requirements for opening and closing the valves. A key requirement for any proposed high pressure fuel injector is reliability. These large-bore, natural gas engines typically run continuously over long time periods, meaning that any suitable fuel injector must be capable of reliably enduring very long operating cycles of the engine. It is desirable for example, that the fuel injectors reliably operate over several hundred million continuous cycles of the engine (about one to two years before replacement). As such, a valve must achieve reliability over this long time period or operating interval. Fuel injectors of the prior art such as that disclosed in Fisher, U.S. Pat. No. 4,365,756 are not capable of reliably sealing and accurately controlling the injection of gas at high pressure. Only recently have economic and environmental pressures on the gas industry resulted in justification for advances in fuel injection technology. For at least the foregoing reasons, commercial large bore 2-stroke and 4-stroke natural gas engines continue to be fueled at low pressure by conventional low pressure fuel injectors.
SUMMARY OF THE INVENTION
It is the general aim of the present invention to provide a commercially reliable and practical fuel injector for injecting high pressure gaseous fuel (eg. around 300-700 psi or more) into combustion engines.
It is an object of the present invention according to one aspect to provide a fuel injector that can withstand the forces of high pressure gaseous fuel and has a long service operation but does not leak either gaseous fuel or hydraulic fluid to the external environment.
It is another object of the present invention according to another aspect to provide a fuel injector that is universal in that the fuel injector assembly can be easily adapted without any or any substantial redesign to fit and operate as desired on the various types and sizes of combustion engines in industry.
It is a another object of the present invention according to another aspect to provide a highly reliable fuel injector, and specifically one that is not susceptible to thermal damage from the engine.
It is another object to provide a fuel injector with increased operating life, whereby gas leakage, eventually expected from O-rings and sliding gas seals, is captured and safely and properly disposed of, on an ongoing basis, not requiring engine shut-down to replace the injector valve.
In accordance with these and other aims and objectives, the present invention is directed toward a gaseous fuel injector cartridge and gaseous fuel injector incorporating the same which is universal in that the cartridge can be adjusted to meet the particular fueling requirements for an engine with no modifications to most of the components in the cartridge. The cartridge includes a valve body (having a variable axial length) in which a fixed length valve is mounted for linear reciprocation. The axial length of the valve body is adjusted by such means as a shim to set and control the stroke of the valve (the distance of movement between open and closed positions).
In the preferred embodiment, the end of the valve body provides a mechanical stop that is adapted to contact and stop movement of the associated actuating mechanism. The shim adjusts the axial distance between the contact surface on the axial end of the valve and the mechanical stop surface.
The preferred form of actuation is hydraulic, in which the valve body is secured to an actuator body. A piston mounted in a bore in the actuator body actuates the valve in response to hydraulic signals. The piston movement toward the open position is stopped by the mechanical stop surface.
In accordance with a further aspect of the present invention, a second shim is used to maintain the overall length of the cartridge body constant, even though the axial length of the valve body is variable. To accomplish this, the axial thickness of the second shim is inversely related to the first shim, with minor compensation in the second shim accommodating tolerance ranges in other cartridge components. The cartridge can be used with a spring mechanism and a metal O-ring for sealing the bottom axial end of the cartridge. According to this feature, a spring mechanism is used to urge the cartridge against a metal O-ring to seal the cartridge against its outer tubular housing. The second shim ensures that the force applied by the spring mechanism is constant thereby providing a highly reliable seal.
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Relative Performance of High-Pressure Fuel Gas Delivery on Large-Bore, Two-Stroke Natural Gas Engines by Willson, et al.—13 pages.
Kim Christopher S.
Leydig , Voit & Mayer, Ltd.
Scherbel David A.
Woodward Governor Company
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