Abstract: A fuel cell system having a stack of proton exchange membrane fuel cells is operated in sub-freezing temperatures by draining any liquid water from the fuel cell water flow passages upon or after the previous shut-down of the stack before freezing can occur, and, thereafter a) starting-up the stack by directing fuel and oxidant reactants into the cell and connecting a load to the stack; b) using heat produced by the stack to increase the operating temperature of the stack to melt ice within the stack; and, c) upon the stack operating temperature reaching at least 0° C., circulating anti-freeze through stack coolers to maintain the temperature of the stack low enough to maintain a sufficiently low water vapor pressure within the cells to prevent cell dry out for at least as long as there is insufficient liquid water to circulate through the water flow passages.

Abstract: A streamlined body has oppositely facing external pressure and suction surfaces that meet to form a leading edge region. Passageways within the body direct pressurized fluid from passageway outlets over the pressure surface toward the leading edge region at a shallow angle with respect to the pressure surface. The pressurized fluid travels around the leading edge region to the suction surface, energizing the boundary layer on the suction surface.

Abstract: Volatile organic compounds are removed from contaminated soil by introducing one or both a water soluble peroxygen compound, such as a persulfate, and a permanganate into the soil, either in situ or ex situ, in amounts and under conditions wherein both the soil oxidant demand is satisfied and volatile organic compounds in the soil are oxidized. In a preferred embodiment, when both are used the peroxygen satisfies the soil oxidant demand and the permanganate oxidizes the volatile organic compounds. Sodium persulfate is the preferred persulfate and potassium permanganate is the preferred permanganate. The persulfate and the permanganate may be added to the soil sequentially, or may be mixed together and added as an aqueous solution.

Abstract: In a combustion process streams of fuel, oxidant or combinations of fuel and oxidant pass simultaneously through a combustion region over opposite sides of a plate disposed therein having downstream extending convolutions which create pairs of large scale oppositely rotating vortices. These vortices cause the fuel and oxidant to mix rapidly with each other. A recirculation zone is disposed immediately downstream and adjacent the edge of the convoluted plate, and in one embodiment is created by a step-wise discontinuity in the flowpath. The mixing occurs without introducing large momentum losses and, when the mixture is ignited immediately downstream of the convoluted plate, the flame propagates with a larger than normal spreading angle.

Abstract: To reduce noise, an automotive exhaust tailpipe has a convoluted surface at or near its outlet to generate pairs of counterrotating axial vortices within the exhaust gases just before or just as the gases exit the tailpipe. The convoluted surface may be the internal surface of the tailpipe, or a thin-walled convoluted member may be disposed within the tailpipe near its outlet end.

Abstract: A control system, such as for a gas turbine engine, prevents a parameter from exceeding a maximum, steady state limit using a topping loop. The topping loop compares the actual value of the parameter to a transient limit which is initially somewhat lower than the steady state limit, but can vary, at a selected rate, up to a maximum of the steady state limit. The difference between the actual value and transient limit may be used to control the system as the parameter approaches the transient limit. The transient limit, and how it varies, is selected to allow a sufficiently rapid approach of the parameter toward and up to the steady state limit, without overshooting such limit.

Abstract: A fluid dynamic pump, such as an ejector, has a common wall which separates a primary high energy fluid flow passage and a secondary low-energy fluid flow passage. The common wall includes a plurality of adjoining lobes extending in the direction of flow to the outlets of the passages at the downstream end of the common wall. A lobe on one side of the wall forms a corresponding trough on the other side. The common wall therefore has a wave-like shape at its downstream end. Primary and secondary fluid flow from the trough outlets on their respective sides of the common wall and are mixed together rapidly in a mixing region downstream of the outlets. A diffuser is located at the downstream end of the mixing region and enhances the pumping ability of the ejector. Secondary fluid is thereby drawn or pumped into the mixing region as a result of this transfer of energy from the primary stream to the secondary stream. Viscous losses are low during the process.

Abstract: An airfoil-shaped body has a relatively thin trailing edge with a series of alternating, adjoining, downstream extending troughs and ridges in its suction surface which form wave-like surface undulations terminating at the trailing edge. The ridges in the suction surface form corresponding troughs in the pressure surface near the trailing edge; and the troughs in the suction surface form corresponding ridges near the trailing edge of the pressure surface. The resulting airfoil-shaped body has a trailing edge with a wave-like shape. The trough and ridge construction delays or prevents two-dimensional boundary layer separation without creating an undesirable drag penalty.

Abstract: A seal assembly secured to the downstream end of a gas turbine engine combustor liner forms a gas path seal at the upstream facing platforms of turbine inlet guide vanes and also cools the vane platforms. The seal assembly includes an annular coolant compartment which feeds cooling air to a plurality of circumferentially spaced apart, axially extending open-ended channels formed between a conical portion of the downstream-most combustor liner and an annular baffle member disposed on the non-gas path side of the conical liner. The seal assembly is supported and axially located on a cylindrical surface which permits locating the seal assembly such that the downstream end of the conical liner is closely spaced from the turbine inlet guide vane platforms to reduce leakage from the gas path.

Abstract: In a heat exchanger, a convoluted plate disposed in a fluid stream flowing in an axial direction generates adjacent counterrotating, large scale axial vortices downstream thereof adjacent a wall over which the fluid flows. The convoluted plate is constructed to produce minimum pressure losses, while the vortices increase the heat transfer rate between the fluid and the wall.

Abstract: An airfoil has a plurality of spaced apart, U-shaped troughs in either or both its suction or pressure surface in the trailing edge region. Each trough extends in a direction generally parallel to the bulk fluid flow in its vicinity near the airfoil surface and has an outlet at the trailing edge. The troughs increase in depth from their inlets toward their outlets, the maximum depth being no more than half the trailing edge thickness. The troughs are spaced apart, sized and configured to flow full over their entire length and to cause fluid to flow into the space immediately behind the trailing edge, thereby reducing base drag.

Abstract: A projectile having a downstream extending surface of revolution which terminates as a blunt base has a plurality of circumferentially spaced apart U-shaped, downstream extending troughs in its surface. Each trough is essentially aligned with the direction of the bulk fluid flow adjacent the surface in the vicinity of the trough, and intersects the blunt base to form a trough outlet therein. The troughs are appropriately spaced apart, sized and configured to flow full over their entire length and to cause fluid to flow into the space immediately behind the blunt base, thereby reducing base drag on the projectile.

Abstract: A body adapted to move downstream through a fluid has a downstream extending smooth surface terminating at a blunt base. A plurality of adjacent U-shaped, downstream extending troughs in the smooth surface intersect the blunt base to form trough outlets. The troughs are appropriately spaced apart, sized and configured to flow full over their entire length and cause fluid to flow into the space immediately behind the blunt base, thereby reducing base drag on the body.

Abstract: A casing surrounding a fluid stream over which an unbounded fluid flows in a downstream direction has a plurality of alternating, adjoining troughs and ridges in its external surface, extending in the downstream direction to a thin trailing edge of the casing, which will thereby have a wave-like shape.

Abstract: A body adapted to move downstream through a fluid has a downstream extending smooth surface terminating at a blunt base. Extending transversely across the smooth surface and disposed upstream of the blunt base is a thin, downstream extending plate closely spaced from the smooth surface. At least the downstream end portion of the plate is convoluted such that its downstream end is wave shaped. The convolutions are designed to generate pairs of counterrotating vortices which delay boundary layer separation from the smooth surface and cause fluid to flow into the space immediately behind the blunt base, reducing base drag on the body. The device generates very little drag of its own.

Abstract: A combustion chamber, such as for a gas turbine engine, includes a protective liner comprised of a plurality of arcuate panels attached to the combustion chamber wall by means of hook-like hangers or lugs integral with and extending radially from the panels through slots in the combustion chamber wall. The lugs hang from retaining strips disposed across a portion of the slots through which the hangers pass. The strips prevent the lugs from being withdrawn from the slots, thereby, positioning the panels radially. Axial and circumferential positioning of the panels is accomplished by means of a close fit between the hangers, slots, and retaining strips. The free floating or nonrigid manner in which the liner panels are attached to the combustion chamber prevents undue stresses from developing in the combustion chamber wall due to the differential thermal growth rates of the combustion chamber wall and the liner panels during engine operation.

Abstract: A gas turbine engine control system operates based upon a synthesized value of a parameter upon loss of the actual measured value of the parameter. To provide smooth engine operation upon switchover to the synthesized parameter a fixed trim is applied to the synthesized parameter which, upon switchover, makes the synthesized parameter equal to the last known measured value of the parameter. Thus, the engine will see no sudden change in operation at the instant of switchover. Thereafter the trimmed synthesized parameter changes in value by the same amount as does the untrimmed synthesized parameter.

Abstract: A hollow, cooled airfoil has a pair of nested, coolant channels therein which carry separate coolant flows back and forth across the span of the airfoil in adjacent parallel paths. The coolant in both channels flows from a rearward to forward location within the airfoil allowing the coolant to be ejected from the airfoil near the leading edge through film coolant holes.

Abstract: A pressure and temperature measuring probe with a low drag, airfoil shaped cross section includes a longitudinally extending pressure cavity adjacent the leading edge and a separate longitudinally extending temperature cavity immediately downstream thereof. Longitudinally spaced apart passages extend downstream from their inlets at pressure measuring stations along the leading edge and intersect the pressure cavity. At temperature measuring stations along the leading edge passages extend downstream adjacent the pressure cavity to intersect the temperature cavity and direct a high velocity flow of gases over a thermocouple junction disposed within the temperature cavity. Stagnation devices at the leading edge reduce gas velocity to zero at the passage inlets.

Abstract: A gas turbine engine control system which regulates fuel flow based upon a schedule which is a function of a primary parameter, such as engine pressure ratio, switches to a schedule based upon a secondary parameter, such as compressor speed, upon the inability to function in the primary parameter mode. Upon switchover to the secondary parameter mode the scheduled value of the secondary parameter is down-trimmed to make it equivalent to the last known good value of the primary parameter so that the engine will not experience a sudden change in power level upon switchover. The down-trim is limited. When the primary mode failure occurs during a transient the down-trim is limited to the difference between a scheduled reference value of the secondary parameter and a value of the secondary parameter calculated immediately preceeding loss of the primary parameter mode and based upon a known relationship between the primary and secondary parameter.