Various studies have identified the internal combustion engine as a chief contributor to air pollution and Federal Standards have been enacted to sharply reduce the permissible content of nitrogen oxides, carbon monoxide, and unburned hydrocarbons in exhaust gases.
As an alternative to the Otto Cycle engine presently used on most automobiles, various manufacturers have considered the use of a gas turbine engine. In providing gases to operate a gas turbine, it has been thought necessary to burn at a relatively high temperature to obtain complete combustion and to oxidize the hydrocarbon fuel to carbon dioxide and water. It has also been thought necessary to conduct the combustion either under stoichiometric conditions or on the rich side of stoichiometric on the theory that this would use up the available oxygen through reaction with the fuel to provide stable combustion and to reduce formation of nitrogen oxides.
During combustion, a number of competing chemical reactions take place, such as reaction of oxygen in the air with carbon atoms in the fuel to form carbon monoxide, reaction of carbon monoxide with additonal oxygen to form carbon dioxide, reaction of hydrogen with oxygen to form water, and reaction of oxygen with nitrogen to form nitric oxide. It has been reasoned that the controlling chemical reaction governing the use of oxygen in the combustion is the reaction of hydrogen, hydrocarbons and carbon monoxide with oxygen. By having an excess quantity of fuel, or an insufficient amount of air for complete combustion, it was reasoned that the oxygen would be consumed in reacting with carbon and hydrogen would, thus, not be available to form oxides of nitrogen.
Previous approaches to combustion in reducing air pollution have, in general, not proved satisfactory. It has been found that formation of nitrogen oxides in the exhaust gases is very difficult to control. When conditions are employed which promote complete combustion by using high combustion temperatures and excess oxygen, it has been found that substantial quantities of nitrogen oxides are formed. Thus, the conditions required for complete oxidation of carbon to carbon dioxide with suppression of carbon monoxide and unburned hydrocarbon formation are apparently contradictory to the conditions required for reducing formation of nitrogen oxides. The use of excess fuel in an attempt to reduce formation of nitrogen oxides has also proven unsatisfactory. With excess fuel present, the formation of carbon monoxide and unburned hydrocarbons is increased. Also, seemingly contrary to theory, nitrogen oxides are formed even though the fuel is used in excess quantities.
There is a need for a combustion process to generate usable power in which the carbon monoxide, unburned hydrocarbon and nitrogen oxide contents of the exhaust gases are reduced. Also, there is a need for such a combustion process and an apparatus utilizing the principles of the process in providing power for automobiles.