REDUCTION OF COEFFICIENT OF VARIANCE OF INDICATED MEAN EFFECTIVE PRESSURE IN FUEL COMBUSTION
Publication Date: 2015-Feb-03
The IP.com Prior Art Database
The present invention is a technique to improve injector shot to shot variation when operating at small fuel injection quantities in a combustion engine. The technique includes injection of water and fuel emulsion or neutral liquid and fuel emulsion. If a neutral liquid, water, or lower energy content liquid fuel is injected along with diesel fuel, the injector is operated in such a way that the needle achieves maximum lift even with the injection of low levels of diesel fuel energy. This reduces cycle to cycle variability in the diesel fuel energy supplied to the combustion chamber allowing more stable operation at low diesel fueling levels while maintaining the ability to deliver and control diesel injection quantities as maximum fuel delivery.
The present invention relates generally to diesel engines and more particularly to a technique for reducing variability of high turn down injector in diesel engine and other liquid injection systems intended to supply a broad range of unit fueling.
Generally, when an injector that is designed for injecting high amounts of diesel is used for injecting very low amounts of diesel, the injector needle does not lift completely. With a partial needle lift situation, fuel flow is determined by area between the needle and its seat. Such a condition is highly unstable since the position of the needle, and thus the flow-controlling area, is influenced by any dynamics within the injector. This uncontrolled motion of the injector results in shot to shot variation of injected fuel quantity. The variation in fuel delivery from cycle-to-cycle results in degradation of engine performance. This phenomenon is even more pronounced when a small amount of diesel fuel is injected to ignite a chamber comprising a mixture of natural gas (NG) and air.
These cycle-to-cycle deviations in injection quantity and timing with a normal injector or high turn down injector (HTDI) produce variations in the indicated power (IP) as reflected by coefficient of variation (COV) of induced mean effective pressure (IMEP).
Several conventional techniques are known in the art that potentially help in reducing variability with low quantity of diesel injection. One such technique is to implement two, or more, injectors to provide more consistent injection over a wide range of fuel quantities. However, it is difficult to package multiple injectors and there is generally insufficient space within the chamber to properly locate more than one injector.
Another conventional technique includes a two needle injector. However, complicated architecture and cost of the two needle injector is equivalent to two separate injectors.
Yet another conventional technique includes reducing spring rate of the needle seating spring to allow lower injection pressures at low unit fueling levels. However, low injection pressure requires significant re-design of the injector and presents challenges to the high unit fueling required for full power operation.
It would be desirable to have an efficient technique that reduces variability with low quantity of diesel injection.
The present invention is a technique to improve injector shot to shot variation when operating at small fuel injection quantities in a combustion engine. The technique includes injection of water and fuel emulsion or neutral liquid and fuel emulsion, or using another fuel mixture with lower energy content.
In a conventional or high turn down injector, the needle of the fuel injector does not achieve maximum lift when injecting low quantities of diesel fuels. Operation of an in...