The following advantages are claimed when using RxP as a fuel additive.
- Increases fuel economy
- Reduces emissions of carblon monoxide (CO) and volatile organic compounds (VOCs)
- Reduces oxides of nitrogen (NOx) emissions
- Removes carbon deposits from engine
The RxP fuel additive contains amongst others, a molecule that is a strong infra-red (IR) absorber. Once in vapor form inside the combustion chamber, it will absorb a large part of the IR radiation that is emitted during the combustion process. It is assumed that this radiation is emitted by the flame front and the hot gas behind it. This radiation would have to travel through the unburned fuel vapor before it reaches the cylinder walls and head, depending on combustion chamber design.
This IR radiation is absorbed by the filter that RxP provides to the fuel mixture and this mixture is preheated prior to combustion. Thus the temperature of the combusted gas is obviously higher, but also the chain reaction (combustion) is promoted so that a more complete combustion takes place (in aircraft engines this allows the mixture to operate leaner than without RxP present).
The increased fuel mileage stems from the fact that, due to the IR absorption, less energy is wasted by escaping to the cylinder walls. Therefore less energy needs to be cooled away by the cooling system and the energy absorbed by the fuel mixture ends up increasing the gas temperature, a part of which is converted to kinetic energy. From the laboratory reports and fleet studies it can be seen that the mileage improvement varies widely depending on engine design. This has to do with the shape of the flame front and the cord length available to the radiation for traveling through the unburned gas mixture.
The preheating of the unburned fuel mixture must have two different advantages. First it is an additional energy input. Second it manipulates the reaction kinetics of the combustion process so that the chain reaction is more complete, meaning fewer unburned fuel molecule escape through the exhaust system.
Note that preheating of the intake air prior to entering the combustion chamber by using waste heat is widely practiced and it seems to be the general agreement that it is worthwhile. This preheating process is accomplished by heat conduction and therefore depends on the temperature gradient that can be imposed on the gas to be preheated. Since this gradient is modest, and the gas flow is fast, there is a limit to what can be achieved. In case of preheating the fuel mixture inside the combustion chamber by IR radiation, a temperature gradient is not an issue as radiation has no temperature, meaning the temperature of a gas having any temperature can still be increased by radiation. In other words, “waste heat” is in this case used before it becomes heat.
From the above, one needs to conclude that the gas temperature inside the combustion chamber runs higher when RxP is applied than it would run without RxP present. At the beginning of the research that lead to RxP, we made spectroscopic measurements on flames and measured an increase of 200 K when the forerunner of RxP was added.
Since the gas temperature in the engine is higher than normal, one would expect an increase in NOx production. What actually is observed is a slight decrease. To explain this, one needs to remember that there are two sources for NOx. The first is the gas inside the combustion chamber and the second is the gas passing through the exhaust valve. In most engine designs the exhaust valve is the hottest solid matter of the engine. We claimed above that the cylinder walls and to some degree also the head, runs cooler when RxP is applied. This also means the exhaust valve will run cooler and therefore produces less NOx. Obviously this effect overwhelms the increase in NOx production due to the higher gas temperatures. The effect of lowering the cylinder head temperature of an engine can be demonstrated nicely with an air cooled aircraft engine that is equipped with a cylinder head temperature gauge. When flying in a cruising configuration (e.g. 75% power), one can switch tanks from untreated fuel to treated fuel and one will notice very soon a drop in cylinder head temperature.
To explain why the carbon deposits are burned off is more involved. Mainly this effect is observed in diesel engines. Gasoline engines start to knock when excessive carbon deposits are present and then usually something is done about it. Whether diesel engines knock due to carbon deposits is debatable since they knock anyway. In both cases, diesel and gasoline, running the engine at higher temperatures helps. In case of treatment with RxP the engine runs indeed at higher temperature (as far as the combusting gas is concerned).
In conclusion one may ask what makes us believe that one ingredient of RxP is an IR absorber. One can of course measure the absorption coefficient of RxP as a vapor, and indeed it absorbs IR radiation. But that does not settle the issue, since in a combustion chamber under high pressure and high temperatures the properties of the RxP vapor may be drastically different. Even if a high absorption coefficient were measured (which undoubtedly would be the case) one could not tell if the effect is sufficient to modify the thermodynamics and if it will indeed reroute the complex chemical chain reactions ongoing in the combustion chamber. One should bear in mind that the influence on the thermodynamics is minimal (2% – 10%). Short time spectroscopic temperature measurements having such a degree of accuracy are a tall order.
RxP would not be such a commercial success, as it is, if it were only the gas mileage improvement. It is rather the indirect effects – rerouting the reaction kinetics and rearranging temperature distribution in the combustion chamber that produce the more desirable effects, namely reduction of volatile hydrocarbon emissions, carbon monoxide emissions and reduced NOx production, that makes the RxP valuable. Nevertheless, we are at present involved in research to shed more light into rerouting the reaction kinetics of the combustion process by certain additives.
Therefore, in absence of more detailed scientific information, we nevertheless like to point to a process that demonstrates this IR absorption. The photographs located at http://www.flamex.com/photos.htm shows that a welding technician, after gouging a steel plate using a gas that contains Flamex (a product specifically blended for the metal cutting industry, which uses the same technology applied to RxP), can touch the cut immediately with his bare hands. Note that steel is cut by combusting part of the material. The combustion process emits IR radiation that heats the wall of the cut. Some of the steel is un-combusted becomes free falling and turns into small spheres. These spheres usually attach themselves to the wall of the cut and need later to be removed by machining. However if the wall is cold, these spheres cannot weld themselves to it since in a welding process both partners need to be hot. We claim that the IR filter prevents the IR radiation from reaching the wall, and as a consequence, the wall is cold enough to touch.
November 16, 1996
Richard T. Schneider, Ph.D.