Internal-combustion engines – Charge forming device – Heating of combustible mixture
Reexamination Certificate
2002-11-14
2004-05-18
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Charge forming device
Heating of combustible mixture
C123S557000, C123S542000
Reexamination Certificate
active
06736118
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the improvement in combustion efficiency of conventional fluid hydrocarbon fuels, such as natural gas or propane gas and the like when employed as fuel for residential, commercial and industrial space heating or cooling equipment, or for process heating, smelting or generating equipment and turbines, whereby such combustion efficiency improvement is obtained through a change in the mass ratio of fuel versus combustion air such as to effectively increase the available oxygen mass relative to fuel mass during ignition.
BACKGROUND OF THE INVENTION
It is generally recognized that the combustion process of conventional fluid hydrocarbon fuels is improved if additional oxygen is introduced into the combustion air/fuel gas mixture at the time of ignition. It is further recognized that the manipulated infusion of additional oxygen into the combustion air/fuel gas mixture is only possible in connection with additional energy expenditure to perform such task.
The Transportation Technologies/Heavy Vehicles Industry is presently investigating the use of natural gas as an alternative fuel for the transportation sector. To improve the power output of such natural gas engines, it is testing a second-stage intercooler for LNG (liquid natural gas) fueled heavy vehicles. The concept uses the LNG fuel to cool the intake air to increase combustion air density relative to fuel density and thereby achieving better engine performance, but without stating any specific temperature level.
The Power Generation Industry is now starting to provide a way of getting more energy from a gas turbine power plant by cooling down the combustion air. Cooling the gas turbine combustion air makes it denser, increasing the mass flow of oxygen for combustion relative to the fuel mass flow. Employing special evaporative air coolers which are attractive to gas turbine operator. Improvements for gas turbines output are substantial. The Industry quotes that, “at an ambient temperature of 100° F. (38° C.) and 30% relative humidity, it is possible to achieve a power increase of 11% to 24% just by cooling the combustion intake air”, without indicating any specific temperature level
U.S. Pat. No. 6,290,487 discloses an invention of fuel injection which uses the pre-heating of fuel strictly as the means to increase fuel flow velocity without regard for the fuel density/combustion air-oxygen ratio change and related efficiency results.
For the purpose of creating an even higher oxygen enhanced combustion air/fuel mixture, but without the requirement for any additional energy to perform such task, the present invention employs a different set of unique circumstances.
To effect combustion efficiency and a noticeable reduction in harmful flue gas emission, a combustion burner will respond favorably to any increase in ratio of oxygen/combustion air mass versus fuel mass in the mixture which is delivered to its burner nozzle for ignition. The most significant ratio change may be obtained through the combination of constantly elevating the fuel pre-combustion temperature level while at the same time maintaining or even reducing the combustion air temperature level. The increased fuel temperature level must not be as high as to approach the flash point temperature of the fuel, as this would interfere with the function of the burner orifice, resulting in a loss of combustion efficiency which would be contrary to the teaching in this disclosure. The most advantageous operating condition, according to the present invention, would provide the highest possible fuel temperature is in combination with the lowest possible combustion air temperature. This will significantly effect the fuel mass to combustion air mass ratio while maintaining constant fuel volume versus combustion air volume ratio flow rates.
In colder climates, and during periods of the year when space heating appliances are usually in operation, fuel stored in storage tanks and fuel transported in conduits exposed to the elements for considerable distances, remains at a density level well above the optimal contemplated operating density range, and pre-heating fuel economically, together with using combustion air drawn from a cool source, could provide significant combustion advantages for both fuel gas and fuel oil applications. Even appliances operating during the summer period, such as gas fired cooling appliances or residential, commercial and industrial water and process heaters, smelting and refractory furnaces and generator turbines, may operate more efficiently with the fuel/combustion air density ratio change method and device.
It is an established fact that most fluid hydrocarbon fuels may have their density reduced by approximately 1% for each 5 degrees Fahrenheit of fuel temperature increase. Therefore, in a condition where such fuel is delivered to the burner mechanism at a low temperature, especially when reaching levels below 35 degrees Fahrenheit, fuel pre-heating, especially at a temperature reaching 900 degrees Fahrenheit, would automatically result in a significant reduction of fuel density of up to 180% while maintaining the same fuel mass. This would obviously result in a significant increase in the available oxygen in the relative combustion air mass, as both combustion air and fuel flow volumes remain constant.
Therefore, such reduced density fuel delivered to the burner orifice arrangement at equal volume but reduced fuel mass, would produce significantly more intense and complete combustion reactions due to higher flame speed and higher flame temperature, with the expanded lower density fuel allowing for a more improved, rapid and complete fuel/oxygen mix with advanced ignition, especially when the density of the combustion air is further increased through cooling.
It therefore stands to reason that such a simple method and device, which provides economical means for energy efficient fuel density reduction for the purpose of changing the fuel to combustion air density/oxygen ratio mix to improve combustion, would be most desirable.
At present, it is still believed in the gas combustion appliance industry that pre-heating of fuel, as contemplated in this invention, is not affective to cause a fuel ignition improvement and thereby increase combustion dynamics. In fact, a correction formula is always employed in the industry to eliminate any variance in fuel efficiency calculations due to a change in fuel temperature or fuel density. Such correction formula calculation may be found in the “Gas Engineers Handbook”, Ninth Printing, Chapter 8, “Gas Calorimetry”, Pages 6-42.
Therefore, the method and device as disclosed in the present invention is completely contrary to industry norm, and is not at all obvious.
SUMMARY OF THE INVENTION
The invention therefore discloses a method and device providing the present effect of reducing fuel density while at the same time maintaining or increasing combustion air density such as to significantly change the ratio of fuel mass versus combustion air mass. This provides a much improved method over the process considered with automotive natural gas combustion engines, employing only a combustion air intercooler. The present combination effect is generally achieved by pre-heating natural gas or propane gas, or other conventional fluid hydrocarbon fuels, as it is delivered to the mechanism's burner manifold, while at the same time maintaining or reducing combustion air temperature when operation today's typical residential, commercial and industrial combustion mechanisms and appliances incorporating a burner arrangement located in a combustion zone. This method is able to provide a significant amount of combustion dynamics improvement while at the same time reducing harmful flue gas emissions.
The present method incorporates a device, which is able to rely solely on heat, or waste heat, generated by the combustion mechanism as heat source for such fuel density reduction operation, consisting of the following basic components.
It comprises a fuel supply conduit
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