GOVERNMENT LICENSE RIGHTS

None.

TECHNICAL FIELD

The present invention relates generally to an internal combustion engine, and more specifically to an internal combustion engine with self-ignition. BACKGROUND

An internal combustion engine, such as one that powers an automobile, includes a combustion chamber with a reciprocating piston that compresses a gas and a spark plug that ignites the compressed gas a fuel mixture to produce combustion. A diesel engine does not make use of a spark plug, but uses the high pressure compressed air to auto-ignite a diesel fuel that is injected into the combustion chamber at near top-dead-center of the piston. A diesel engine cannot burn natural gas because the auto-ignition temperature of natural gas is much higher than the temperature produced in the gas from the compression. For this reason, a diesel engine would also inject a fuel such as diesel fuel into the compressed natural gas to ignite the compressed natural gas to produce combustion.

As pressures increase in an internal combustion engine to produce higher efficient engines, the temperature of the compressed gas also increases. Too high of a pressure results in too high of a temperature, and the compressed gas would ignite prematurely.

High thermal efficiency and reduced emissions, such as NOx, in a

reciprocating internal combustion (IC) engine can be achieved by reducing the fuel/air ratio and increasing the break mean effective pressure. However, traditional ignition methods become unreliable as the mixture ratio becomes too lean, leading to higher coefficient of variation (COV) and spark plugs tend to fail via flash-over caused by the higher voltages required by the higher ignition pressure. These high voltages also reduce spark plug life due to higher erosion rates. As a result, elimination of the spark plug with a more reliable ignition method could improve emissions and enable efficiency gains to be realized with leaner mixtures and higher combustion pressures.

Also, spark plugs need to be replaced at regular intervals due to wear. This generally occurs during regularly scheduled maintenance, not necessarily when the spark plugs actually need to be replaced. When done this way, unforeseen shutdowns due to failures between scheduled maintenance intervals may occur. Therefore, eliminating the need for spark plugs will also reduce maintenance costs and engine down-time.

Us Patent No. 4,969,425 issued to Slee on 11/13/1990 and entitled PISTON WITH A RESONANT CAVITY discloses an internal combustion engine with a resonance cavity formed in the piston of to a side toward an exhaust port of the engine, and where the engine includes a spark plug to ignite the fuel and air mixture.

SUMMARY

The present invention is an internal combustion engine with self-ignition, where the fuel can be a liquid fuel or a gaseous fuel. Resonance tube ignition, where a specially designed cavity in the head of a piston combined with high pressure gas injection is used to induce shock waves which in turn raises the local fuel/air mixture temperature above ignition. This process is very reliable and does not require a spark plug.

In order to ignite a mixture of fuel and air, the temperature must be raised and the air/fuel ratio must be such that the mixture ignites. In a spark-ignition engine, the temperature rise is provided with a localized electrical energy discharge, whereas in a compression ignition (such as diesel) engine the entire air/fuel mixture rises in temperature due to mechanical compression of the gas and the heat of the cylinder wall. Resonance tube ignition occurs because of a rapid localized increase in temperature caused by a sudden increase in pressure from compression waves emanating from the nozzle that is injecting gas into a resonance tube within the combustion chamber cavity at sonic velocities and resonating in the cavity.

In one embodiment, an internal combustion engine includes: a piston movable within a cylinder; a cylinder head with an inlet port and an exhaust port, the piston having a head with a resonance cavity facing the cylinder head; and an injection nozzle within the cylinder head and positioned to discharge a fuel toward the resonance cavity, the resonance cavity and the injection nozzle being positioned such that ignition of the fuel within a combustion chamber occurs due to resonance within the resonance cavity.

In one aspect of the embodiment, the internal combustion engine is without a spark plug.

In one embodiment, a piston for an internal combustion engine, the internal combustion engine being without a spark plug, includes: a piston head; and a resonance cavity opening into the piston head, the resonance cavity having a shape to produce ignition of a fuel within the engine without a spark plug due to a resonance formed within the resonance cavity.

In one aspect of the embodiment, the resonance cavity is rectangular in a cross-sectional side view.

In one aspect of the embodiment, the resonance cavity has a cavity length (1) and a cavity width (w), the cavity length (1) being greater than a cavity width (w).

In one aspect of the embodiment, the fuel is a natural gas.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

FIG. 1 shows a cross section view of a reciprocating piston within a cylinder with a resonance cavity and injection nozzle of the present invention for auto-ignition; and FIG. 2 shows a second embodiment of the present invention in which the resonance cavity is located in the cylinder head as a static part of the cylinder.

DETAILED DESCRIPTION

The present invention is an internal combustion engine with self-ignition, where the fuel can be a liquid fuel or a gaseous fuel. Resonance tube ignition, where a specially designed cavity combined with high pressure gas injection is used to induce shock waves which in turn raises the local fuel/air mixture temperature above ignition. This process is very reliable and does not require a spark plug.

In order to ignite a mixture of fuel and air, the temperature must be raised and the air/fuel ratio must be such that the mixture ignites. In a spark-ignition engine, the temperature rise is provided with a localized electrical energy discharge, whereas in a compression ignition (such as diesel) engine the entire air/fuel mixture rises in temperature due to mechanical compression of the gas and the heat of the cylinder wall. Resonance tube ignition occurs because of a rapid localized increase in temperature caused by a sudden increase in pressure from compression waves emanating from the nozzle that is injecting gas into a resonance tube within the combustion chamber cavity at sonic velocities and resonating in the cavity.

FIG. 1 shows a combustion chamber 18 of the present invention with a piston 11 reciprocating within a cylinder 12. The piston 11 includes a piston head 19 with a resonance cavity 13 that creates shock waves. The resonance cavity 13 has a cavity width (w) and a cavity length (1). In some embodiments, the cavity length (1) is greater than the cavity width (w). Further, the resonance cavity 13 may have any suitable cross-sectional shape, such as rectangular, square, circular, oval, or the like. The combustion chamber 18 is formed between the piston head 19 and a cylinder head 17 that includes an inlet port 14 (for example, a valve) and an exhaust port 15 (for example, a valve) as well as an injection nozzle 16 that opens into the combustion chamber 18.

Air can be drawn into the combustion chamber 18 through the inlet port 14 while the exhaust gas from combustion in the combustion chamber 18 can be discharged through the exhaust port 15. A fuel such as natural gas can be injected into the combustion chamber 18 through the injection nozzle 16. The gaseous fuel (or even air) can be injected into the resonance cavity 13 that will bounce off of the cavity floor and flow back toward the injection nozzle 16 as a bow wave (represented by the concave curve in FIG. 1 above the resonance cavity). Shock waves are formed from the bow waves striking the oncoming waves from the injection nozzle 16, and these shock waves produce patterns of high pressure that result in high temperature. An injection of gaseous oxygen and gaseous hydrogen at 70 degrees F will produce a heated gas in excess of 1,000 degrees F which would be a high enough temperature to auto-ignite the gas mixture and produce combustion within the combustion chamber 18.

As the piston 11 moves up and down within the cylinder 12, the spacing or distance within the combustion chamber 18 between the injection nozzle 16 and the opening of the resonance cavity 13 (nozzle-cavity gap) will change. One desirable feature of the present invention is that combustion should occur at or near to the top- dead-center (TDC) of the piston 11 within the combustion chamber 18. Thus, the nozzle-cavity gap will be near to the minimum when the piston 11 is at or near to the top-dead-center when the auto ignition is desirable. With the auto-ignition device of the present invention, much leaner bulk mixtures and higher pressures can be achieved than in the spark ignited engines of the prior art. The width (w) and length (1) of the resonance cavity 13 can be designed such that the auto-ignition temperature will only occur at the desired location of the piston 11 within the cylinder 12, such as at TDC.

The engine in FIG. 1 can inject a fuel and air into the combustion chamber 18 through the inlet port 14 as in a typical ICE and inject compressed air through the injection nozzle 16 that would create the shock waves that induce an auto-ignition of the compressed fuel and air mixture. Thus, vaporized gasoline could be combusted with compressed air using the resonance cavity 13 that creates the shock waves to ignite the fuel/air mixture within a spark plug. In a diesel engine, the diesel fuel and the air can be injected through the inlet port 14 and then compressed by the piston 11 moving upward in the cylinder 12, and compressed air can be injected through the injection nozzle 16 into the resonance cavity 13 to create the shock waves that produce the ignition of the fuel/air mixture. In either of these embodiments, a gaseous fuel such as natural gas can also be injected through the injection nozzle 16 to produce shock waves in the resonance cavity 13 to produce the combustion without using a spark plug.

In another embodiment of the present invention, a resonance cavity can be formed on the cylinder head that would face toward a side of the cylinder where an injection nozzle would be located that would inject the compressed air or gas into the resonance cavity to produce the shock waves. Because the resonance cavity in this embodiment would not move and thus the nozzle-cavity gap would not change, the compressed air or gas would only be injected when the auto-ignition should occur such as when the piston is at TDC or nearby. FIG. 2 shows a cylinder head 28 having the resonance cavity 26 formed therein, along with fuel and air supply for the combustion chamber 22. US Patent 6,272,845 issued to Kassaev et al. on 08/14/2001 and entitled ACOUSTIC IGNITER AND IGNITION METHOD FOR

PROPELLANT LIQUID ROCKET ENGINE shows a piece than can be formed within the cylinder head of the engine to produce a similar effect at that disclosed in FIG. 1 embodiment. The FIG. 2 embodiment includes piston 21 with a typical flat head, a combustion chamber 22, an outlet orifice 23, an injection nozzle 24, a fuel injector tube 25, an acoustic resonator 26 (which may also be referred to as the resonance cavity), a housing 27, and a cylindrical wall 29 among other structures as described in the Kassaev et al. patent.

In this embodiment, compressed air is provided from an external source to the combustion chamber 22 at, or close to, TDC via the injection nozzle 24. This compressed air travels across the combustion chamber 22, enters the acoustic resonator 26, which reflects back into the combustion chamber 22 creating a shock wave that increases the temperature in the combustion chamber 22. At the appropriate time in the cycle, fuel is introduced into the combustion chamber 22 creating a combustible mixture which is then ignited by the shock wave created. This ignites the fuel/air mixture in the engine via outlet orifice 23.

In one embodiment, an internal combustion engine includes: a piston 11 movable within a cylinder 12; a cylinder head 17 with an inlet port 14 and an exhaust port 15, the piston 11 having a head with a resonance cavity 13 facing the cylinder head 17; and an injection nozzle 16 within the cylinder head 17 and positioned to discharge a fuel toward the resonance cavity 13, the resonance cavity 13 and the injection nozzle 16 being positioned such that ignition of the fuel within a combustion chamber 18 occurs due to resonance within the resonance cavity 13. In one aspect of the embodiment, the internal combustion engine is without a spark plug.

In one embodiment, a piston 11 for an internal combustion engine, the internal combustion engine being without a spark plug, includes: a piston head 19; and a resonance cavity 13 opening into the piston head 19, the resonance cavity 13 having a shape to produce ignition of a fuel within the engine without a spark plug due to a resonance formed within the resonance cavity 13.

In one aspect of the embodiment, the resonance cavity 13 is rectangular in a cross-sectional side view.

In one aspect of the embodiment, the resonance cavity 13 has a cavity length

(1) and a cavity width (w), the cavity length (1) being greater than a cavity width (w).

In one aspect of the embodiment, the fuel is a natural gas.

It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention, which is limited only by the following claims.