USA As Represented by Secretary of the Navy

Other

The United States of America As Represented by the Department of Health

Klaus C Schadow

Kenneth Jay Wilson

Timothy P Parr

Robert A Smith

Kenneth H Yu

Ephraim Gutmark

Kenneth L Wilson

Larry L Liedtke

William R McBride

Eric D Erickson

Everett M Bens

Thomas L Boggs

James E Crump

H Dean Mallory

Robert Smith

Donna M Hanson-Parr

Richard A Stalnaker

Don J Chieze

This invention relates to air breathing engines, such as ramjets, scramjets and internal combustion, and more particularly to an active combustion control device for a combustor. In more particularity, the present invention relates to a method and apparatus that applies active combustion control technology to advanced propulsion devices and closed-loop fuel injection at sub-harmonic frequencies of the instability frequency of the combustor. The problem of limited actuator frequency response is addressed by injecting fuel pulses at sub-harmonic frequencies of the instability. The fuel may be liquid, solid or gas. To achieve this desired result, a closed loop controller is designed to determine sub-harmonic frequencies using a divider to divide the instability frequency of a combustor, yielding a fraction of the harmonic frequency. Also, this invention also combines open loop injection control with closed loop injection control to obtain enhanced engine performance, which includes extension of the stable combustion zone.

Method and device for modulation of a flame

The present invention relates to a method and device for controlling the solid fuel regression rate of a solid fuel ramjet engine. In a preferred embodiment of the present invention, pressure oscillations are excited using active, closed-loop control to vary the heat transfer, and in turn the regression rate of a solid fuel ramjet engine. The pressure oscillations are excited by introducing small disturbances into the shear layer. The disturbances are amplified in the shear layer and excite pressure oscillations. The disturbances are introduced at a certain phase relative to the pressure oscillations. This is accomplished by closed-loop control. By varying the phase, the amplitude of the pressure oscillations can also be varied, which in turn will vary the heat transfer, regression rate, and thrust level.

Solid fuel regression rate control method and device

This invention involves an improved technique for the modulation of waste in an actively controlled compact waste incinerator afterburner. This improved technique utilizes acoustic driving to affect indirect modulation of waste flow velocities. The waste surrogate gases are modulated indirectly by periodic entrainment created by the roll-up of the main air vortex as well as indirect acoustic excitation of secondary air injection. One of the main advantages of this new configuration is the acoustic drivers used to phase inject the waste into the vortex for proper combustion are not in direct contact with the hot waste and therefore can be less expensive and more durable over the long term.

Apparatus for activity controlled waste incinerator afterburner

This invention involves an improved technique for the modulation of waste an actively controlled compact waste incinerator afterburner. This improved technique utilizes acoustic driving to affect indirect modulation of waste flow velocities. The waste surrogate gases are modulated indirectly by periodic entrainment created by the roll-up of the main air vortex as well as indirect acoustic excitation of secondary air injection. One of the main advantages of this new configuration is the acoustic drivers used to phase inject the waste into the vortex for proper combustion are not in direct contact with the hot waste and therefore can be less expensive and more durable over the long term.

Indirect modulation method for activity controlled waste incinerator

An apparatus for the disposal of solid rocket motors which produce exhaust ases containing flammable and/or explosive products. The solid rocket motor to be burned is first detachably connected to and inserted in one end of an elongated mixing chamber which has, at an opposite end, a multi-step expansion nozzle. The rocket motor is then ignited and the exhaust gas is passed into the mixing chamber, which is sufficiently large to reduce the velocity of exhaust gases from supersonic to subsonic. Air is injected into the mixing chamber to react with flammable and/or explosive products in the exhaust gases and the resultant mixture is then discharged from the mixing chamber through a multi-step expansion nozzle to expand the gaseous mixture and, at the same time, produce substantial turbulence within the gas mixture which is about six times higher than the turbulence levels produced by a constant area circular nozzle. The expansion nozzle has an inner wall with a stair-step shaped surface, having an aspect ratio of not less than 2 and not greater than 10, to create the increased turbulence levels within the multistep nozzle.

Apparatus for after-burning fuel rich rocket exhaust products

The present invention relates to an electric valve capable of producing podic mass-flow modulation of a gaseous, liquid, or mixed-phase medium over wide ranges of frequencies, pressure, and flow rates. Such mass-flow modulation can be used to periodically shed large-scale vortices at the outlet and to manipulate their dynamics allowing the user to actively control fluid mixing and transport further downstream. The device has a piezoelectric wafer that in a relaxed state abuts the upstream end of the outlet tube separating the pressurized fluid in the plenum with the outlet. The device has an apparatus for applying electric field to the wafer, which distorts the wafer and ruptures the seal forming a throat area that controls the fluid mass flux. Due to the fast response of the piezoelectric material to an electric field, the throat area can be modulated rapidly in time making the device operable even at high frequencies. The present invention is particularly useful for actively controlling fuel-air mixing in a combustor. However, it may be utilized in other applications such as in medical drug administration for inhalation therapy.

Mass-flux actuator with high frequency response

A shear layer of a fluid flow has relatively large vortical structures generated by acoustic forcing from oscillations induced in a cavity closely adjacent to the flow so that these structures enhance mixing at the layer. The forcing frequency is selected by varying the dimensions of the cavity, and several cavities of different dimensions may be provided for forcing at different frequencies, including beat frequencies. The cavity provides passive, high amplitude forcing effective with a compressible shear layer due to high speed flow, including supersonic flow. Cavities of differing configuration provide forcing for fluid flow from nozzles of different geometries. The most effective enhancement is provided by particular excitation frequencies generated by a cavity having a size selected in accordance with dimensionless relations between the flow parameters and nozzle geometry.

Enhancement of flow mixing by a frequency tunable cavity

An improved technique for the active control of various combustion devices. This improved technique employs a flame kernel pulse actuator which produces periodic flame kernels by a spark ignition of a stoichiometric air and fuel mixture upstream of the combustion chamber. The discrete flame kernels are convected in a duct of premixed fuel and air which produce discrete pressure oscillations due to the energy release as each discrete flame propagates. Because the source of the energy release is essentially a chemical reaction, the flame kernel pulse actuator is able to produce a substantial amount of energy release even at the high operating pressures which are often encountered in many operational environments. These pressure oscillations may be adjusted to suppress or augment any combustion induced pressure oscillations as well as act to modulate the mixing layer between the fuel and air, thus controlling the downstream combustion process. The flame kernel pulse actuator comprises an actuator housing, a secondary fuel injection system, and an igniter. The combination of the igniter and fuel injection system produces a plurality of discrete flame kernels which are convected downstream toward the combustion chamber. The present flame kernel pulse actuator further includes a pressure sensor which is positioned so as to measure the acoustic oscillations in the combustion chamber and a controller device which uses the output of the sensor to control the frequency, phase shift, and amplitude of the discrete flame kernels.

Method and apparatus for active control of combustion devices

An improved method and apparatus for actively controlling a combustion process such as a waste incinerator by means of a spatial and temporal synchronized injection of fuel. The improved method and apparatus employs an active control system which controls the intentional formation of large scale, coherent vortices and the synchronized injection of the fuel supply at various locations relative to the formation of the vortices. The preferred apparatus comprises an actuator or similar structure that is adapted for producing and stabilizing discrete, large scale vortices in a combustion device. In addition, another device controls or modulates the injection of the fuel into the vortices at the optimal location and timing relative to the vortex cycle. As applied to an incinerator, this method can be optimized to ensures that the fuel and waste are introduced into the highest temperature locations, were extended residence times are obtained by trapping the fuel and waste inside the vortices. A high combustion efficiency may also be achieved by actively synchronizing the periodic fuel injection with the formation of the vortices.

Method and apparatus for the active control of a compact waste

The oscillations found to occur in the cavities of an structural frame moving through a fluid are substantially eliminated by the adoption of perturbation elements located at the leading edge of the cavity and reflecting any remaining oscillations out of the cavity at the trailing edge. The perturbation elements may take the form of multiple pins of various shape and geometrical arrangement which prevents the generation and growth of vortices causing acoustic oscillations. The reflection of remaining oscillations out of the cavity may be accomplished by ramping the trailing edge of the cavity.

Suppressor of oscillations in airframe cavities

A regenerative liquid propellant gun and pertains includes a modified contional fixed bolt extending into a conventional combustion chamber of the regenerative liquid propellant gun. The modified fixed bolt of this invention provides for improved operation of the otherwise conventional regenerative liquid propellant gun and has modified end portion embodiments and internal propellant injection passages, all for the purpose of creating turbulent propellant flow.

Combustion instability suppression in regenerative liquid propellant gun

In a combustor in which a flow area for fuel and air increases suddenly at dump so as to generate vortices which mix the fuel and air for combustion downstream of the dump, the improvement in which the flow cross section upstream of the dump is noncircular, as triangular or rectangular, causing flow downstream of the dump to be noncoherent so that mixing by the vortices is aperiodic with the result that heat release on mixing is uniform in time and does not drive oscillations in the combustor.

Dump combustor with noncoherent flow

In a solid fuel ramjet in which a fluid flow boundary layer extends along a urning fuel grain and receives combustible material liberated from the grain, exciting oscillations in air flowing toward the grain so that oscillations continue in the boundary layer and promote vortices in the layer to mix the air and the combustible material.

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Ridgecrest, CA, United States of America

Klaus C Schadow