Power plants – Internal combustion engine with treatment or handling of... – Material from exhaust structure fed to engine intake
Reexamination Certificate
2001-07-16
2002-10-29
Freay, Charles G. (Department: 3746)
Power plants
Internal combustion engine with treatment or handling of...
Material from exhaust structure fed to engine intake
C060S247000, C060S740000, C060S767000, C239S434000
Reexamination Certificate
active
06470672
ABSTRACT:
FIELD OF THE INVENTION
The invention is a minimally intrusive slender supersonic injector flush mounted to the wall of a combustor through which combustion air flows. When not in use, the invention is substantially nonintrusive. The invention may also be used to control the attitude of a spaceplane above the atmosphere of the earth.
BACKGROUND OF THE INVENTION
A typical scramjet engine includes a combustor having a chamber wherein a fuel-air mixture moving at supersonic speed is burned. At least one fuel injector directs supersonically-moving fuel such as pressurized hydrogen into the chamber. The engine also includes an air inlet, which delivers compressed supersonically-moving air to the combustor chamber and further includes an exhaust nozzle which channels the burning gas out of the combustor chamber to help produce the engine thrust. The fuel injector discharge orifices are the openings in the combustor chamber to which fuel is delivered by a fuel system which may includes tanks, pumps and conduits.
State-of-the-art flush mounted circular and wedge injectors, similar to those proposed for use in scramjet (supersonic combustion ramjets) and rocket-based, combined-cycle (RBCC) air breathing space planes or missiles and liquid oxygen-augmented nuclear thermal rocket (LANTR) proposed Mars space transportation propulsion system, are intrusive when not used (generating significant shock disturbances throughout the system) and when used, create a high heat flux near the origin of injection due to a created separation bubble in front of the jet and/or recirculation eddies just downstream of the jet. Penetration and adequate mixing of exiting jet or jets in the main supersonic flow that supports a burnable/stable combustion process before being discharged is difficult to obtain.
RBCC/Scramjet/LANTR propulsion systems require fuel and/or oxidizer augmentation injectors that fulfill specific penetration, mixing, and uniform stable burning needs within the shortest distance for a wide range of supersonic cross flow Mach numbers when in use, but must be minimally intrusive when not in use. A flush mounted jet in a supersonic cross flow is quickly deflected by aerodynamic effects until the plume becomes parallel to the combustor surface freestream cross flow but does not mix adequately to support stable supersonic combustion. A plyup/ramping in the separated boundary layer occurs in front of the blockage produced by the state-of-the-art jet plume bringing the regional subsonic boundary layer flow nearly to rest. A recirculation pattern occurs withing this region enlarging the angular separated boundary layer plyup. A large bow pressure disturbance wave results as reported in NASA/TM-1999-208893 which is incorporated by reference hereto. This phenomena continues to persist affecting stable RBCC/scramjet/combustion performance to date regardless of the prior art injector angle and/or whether such injector is followed by a high drag mixing cavity.
U.S. Pat. No. 5,202,525 issued to Coffinberry on Apr. 13, 1993 states that the mixing of hydrogen fuel in a scramjet combustor is a difficult process since the compressed airfow is flowing at supersonic velocities with substantial momentum and the fuel injected into the combustor has relatively low momentum. Coffinberry further states that oxygen and nitrogen molecules contained in the air have relatively large mass inertia which typically easily overcome the relatively low mass inertia of molecular hydrogen in the fuel. Accordingly, hydrogen fuel has the tendency to simply follow the stream of supersonic airflow without significant mixing. In order to obtain acceptable combustion in the scramjet combustor, acceptable mixing of the fuel and supersonic airflow must be obtained. See, the '525 patent, col. 1, lns. 29-42. Supersonic combustors face the further challenge that the fuel must be fully mixed within the combustor in a length as short as possible.
U.S. Pat. No. 5,280,705 issued Jan. 25, 1994 to Epstein et al. discloses an intermittent admission of the fuel to the airflow to promote enhanced combustion and to minimize the heat load on the combustor.
U.S. Pat. No. 5,220,787 issued to Bulman Jun. 22, 1993 discloses a locally pressure matched injector. Namely, the exit pressure of the injector is matched to the cross-flow pressure of the combustion air. By matching the exit pressure of the fuel jet to the pressure surrounding the fuel jet, a jet of the narrowest width is produced having the highest momentum. Bulman cites F. S. Billig et al and other researchers (Billig, F. S., Orth, R. C., Lasky, M., “A Unified Analysis of Gaseous Jet Penetration,” American Institute of Aeronautics and Astronautics Journal, Vol. 9, No. 6, Jun. 1971, pp. 1048-1058, that studied the penetration and mixing of fuel jets in cross flows in the 1960's. Billig et al. studied the effects of introducing fuel through both a circular opening and a noncircular opening. According to Bulman, the use of these noncircular openings by Billig did not have the desired effect, namely, improved penetration and mixing because the pressure matching was only performed on an average basis.
The Bulman '787 patent cites the need for better fuel mixing which improves the combustion efficiency of the engine. Bulman recognized prior attempts to get more fuel in the air stream by simply pumping more fuel therein. However, according to Bulman, air/fuel mixing is not well served by having a few large injectors because the result is a large over-fueled region surrounded by underfueled air. See, for example, the Bulman '787 patent at col. 1, lns. 37-45. Bulman cites the need for better mixing in relation to the gap between injectors. In other words, according to Bulman, better penetration and mixing enables the use of multiple injectors spaced closer together which promotes more thorough and consistent combustion in a smaller space within the engine.
Bulman '787 discloses a fuel injector having at least one fuel inlet port, throat and fuel exit port serially connected and which in combination produce the local pressure match as well as a low drag shape. Bulman cites calculation of the throat contour to produce the correct area ratio to achieve the local pressure matching condition in that the fuel jet exiting from the fuel injector from the proximate end is lower in velocity and therefore at a higher pressure while the fuel jet exiting from the injector body near the distal end has a higher velocity and lower local pressure. See, col. 10, lns. 39-48, of the Bulman '787 patent. The ratio of the exit width to the throat width determines the local area ratio. Bulman '787 in
FIG. 13A
thereof cites an example having a 2.25 degree throat area half angle.
The Bulman '787 seven (7) degree half angle wedge and its cascade injector version reduced forward hot spots somewhat and slightly increased penetration. However, as tested this injector consistently produced a non-uniform velocity profile jet (Mach 2.1 to 1.67) from bow to stern over a wide range of injectant pressures. State-of-the-art scramjet engines presently use groups of normal or angled hole injectors (quarter inch diameter) just forward of high drag/step mixing cavities or the Bulman '787 wedge injectors positioned on a strut within the combustor duct geometry.
All prior art supersonic injectors are intrusive when not used, creating a not to be ignored pressure wave and shock disturbances that propagate downstream the combustor duct. When supersonic flush injection is used within or into supersonic crossflow a large pressure wave, shock disturbances and hot spots occur near the jet. See, NASA/TM 107533, NASA/TM 1999-208893, and/or NASA/TM-2001-210951.
State-of-the-art hole injectors exhibit a forward bow wave which tends to separate extensively forward of the bow shock and creates a large disturbance (circulations and hot spots) downstream. Bulman's structure reduces the forward disturbance significantly but does not eliminate it. Downstream of the Bulman injector the disturbance is signifi
Buggele Alvin E.
Gallagher John R.
Belena John F
Freay Charles G.
Stone Kent N.
The United States of America as represented by the Administrator
LandOfFree
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