Showing papers on "Afterburner published in 1995"

Device for actively controlling combustion instabilities and for decoking a fuel injector

Abstract: A device for actively controlling combustion instabilities and for decokinguel injectors comprises at least one detector for measuring pressure fluctuations in a combustion or afterburner chamber, means for processing the signal output by the detector and providing, in turn, a control voltage, and at least one piezoelectric device which is disposed in a hydraulic line including a fuel injector for the supply of fuel to the combustion or afterburner chamber and which is responsive to the control voltage to generate pulses in the flow of fuel from the outlet of the fuel injector.

Abatement of N2O Emissions from Circulating Fluidized-Bed Combustion Through Afterburning

Abstract: A method for the abatement of N20 emission from fluidized bed combustion has been investigated.The method consists of burning a secondary fuel after the normal circulating fluidized bed combustor. Liquefied petroleum gas (LPG), fuel oil, pulverized coal, and wood, as well as sawdust, were used as the secondary fuel. Experiments showed that the N2O emission can be reduced by 90% or more by this technique. The resulting N20 emission was principally a function of the gas temperature achieved in the afterburner and independent of afterburning fuel, but the amount of air in the combustion gases from the primary combustion also influences the results. No negative effects on sulfur capture or on NO or CO emissions were recorded. In the experiments, the primary cyclone of the fluidized bed boiler was used for afterburning. If afterburning is implemented in a plant optimized for this purpose, an amount of secondary fuel corresponding to 10% of the total energy input should remove practically all N2O. During the present experiments the secondary fuel consumption was greater than 10% of the total energy input due to various losses.

NASA Lewis Research Center's combustor test facilities and capabilities

Abstract: NASA Lewis Research Center (LeRC) presently accommodates a total of six combustor test facilities with unique capabilities. The facilities are used to evaluate combustor and afterburner concepts for future engine applications, and also to test the survivability and performance of innovative high temperature materials, new instrumentation, and engine components in a realistic jet engine environment. The facilities provide a variety of test section interfaces and lengths to allow for flametube, sector and component testing. The facilities can accommodate a wide range of operating conditions due to differing capabilities in the following areas: inlet air pressure, temperature, and flow; fuel flow rate, pressure, and fuel storage capacity; maximum combustion zone temperature; cooling water flow rate and pressure; types of exhaust - atmospheric or altitude; air heater supply pressure; and types of air heaters - vitiated or nonvitiated. All of the facilities have provisions for standard gas (emissions) analysis, and a few of the facilities are equipped with specialized gas analysis equipment, smoke and particle size measurement devices, and a variety of laser systems. This report will present some of the unique features of each of the high temperature/high pressure combustor test facilities at NASA LeRC.

Combustion Oscillation Control by Cyclic Fuel Injection

Abstract: A number of recent articles have demonstrated the use of active control to mitigate the effects of combustion instability in afterburner and dump combustor applications. In these applications, cyclic injection of small quantities of control fuel has been proposed to counteract the periodic heat release that contributes to undesired pressure oscillations. This same technique may also be useful to mitigate oscillations in gas turbine combustors, especially in test rig combustors characterized by acoustic modes that do not exist in the final engine configuration. To address this issue, the present paper reports on active control of a subscale, atmospheric pressure nozzle/combustor arrangement. The fuel is natural gas. Cyclic injection of 14% control fuel in a premix fuel nozzle is shown to reduce oscillating pressure amplitude by a factor of 0.30 (i.e., {approximately}10 dB) at 300 Hz. Measurement of the oscillating heat release is also reported.

Brennstoffversorgungseinrichtung für Turbo-Strahltriebwerke mit Nachbrenner

Abstract: A fuel supply device 1 for a turbo jet engine with afterburner 2 has pipes 9 and 10 bifurcating from a main fuel pipe 7 for the supplying of fuel to the afterburner 2 and the combustion chamber 3. To deliver the fuel at the required rate of flow and at the required pressure, provision is made in the main fuel pipe 7 for a first fuel delivery pump 6, and for a second fuel pump 11 and respectively an afterburner pump 18 in the fuel pipes 9 and 10. In order also to be able to supply the afterburner 2 via the second fuel pump 11 when a suitably free pump capacity exists, downstream of the afterburner pump 18 and the second fuel pump 11 provision is made for a connecting pipe 19 between the two fuel pipes 9 and 10. When operating the turbo jet engine with afterburner, the afterburner 2 can be supplied by the second fuel pump 11 via the connecting pipe 19 when the fuel requirement of the turbo-combustion chamber 3 is reduced, so that its delivered quantity of fuel is high. An undesirably high fuel temperature downstream of the second fuel pump 11 can thus be prevented. An oil cooler 14 may be provided (various positions of correction being disclosed) as well as a 2/4 directional control valve in the connecting pipe (figure 2).

A design perspective on thermal barrier coatings

Abstract: This technical paper addresses the challenges for maximizing the benefit of thermal barrier coatings for turbine engine applications. The perspective is from a customer's viewpoint, a turbine airfoil designer, who is continuously challenged to increase the turbine inlet temperature capability for new products while maintaining cooling flow levels or even reducing them. This is a fundamental requirement to achieve increased engine thrust levels. Developing advanced material systems for the turbine flowpath airfoils is one approach to solve this challenge, for example, high temperature nickel based superalloys or thermal barrier coatings to insulate the metal airfoil from the hot flowpath environment. The second approach is to increase the cooling performance of the turbine airfoil, which enables increased flowpath temperatures and reduced cooling flow levels. Thermal barrier coatings have been employed in jet engine applications for almost 30 years. The initial application was on augmenter lines to provide thermal protection during afterburner operation. However, the production use of thermal barrier coating in the turbine section has only occurred in the past 15 years. The application was limited to stationary parts, and only recently incorporated on the rotating turbine blades. This lack of endorsement of thermal barrier coatings resulted from the poor initial durability of these coatings in high heat flux environments. Significant improvements have been made to enhance spallation resistance and erosion resistance which has resulted in increased reliability of these coatings in turbine applications.

Flow field calculations for afterburner

Abstract: In this paper a calculation procedure for simulating the combustion flow in the afterburner with the heat shield, flame stabilizer and the contracting nozzle is described and evaluated by comparison with experimental data. The modified two-equationk – ɛ model is employed to consider the turbulence effects, and thek – ɛ –g turbulent combustion model is used to determine the reaction rate. To take into account the influence of heat radiation on gas temperature distribution, heat flux model is applied to predictions of heat flux distributions. The solution domain spanned the entire region between centerline and afterburner wall, with the heat shield represented as a blockage to the mesh. The enthalpy equation and wall boundary of the heat shield require special handling for two passages in the afterburner. In order to make the computer program suitable to engineering applications, a subregional scheme is developed for calculating flow fields of complex geometries. The computational grids employed are 100×100 and 333×100 (non-uniformly distributed). The numerical results are compared with experimental data. Agreement between predictions and measurements shows that the numerical method and the computational program used in the study are fairly reasonable and appropriate for primary design of the afterburner.

Two=stage catalytic gas burner

Abstract: The burner gives flameless combustion of a mixture of inflammable gas and air. Where the amount of gas mixture converted in the second stage is excessive, the temperature rise can increase the heat transferred to the first stage, thus increasing conversion of the mixture in the latter. Conversely, where the amount converted in the second stage is too small, it receives more heat from the first stage due to the temperature rise in the latter, thus increasing conversion in it. The first stage can be formed by a gap-type burner (2) enclosing a cylindrical body (3), inside which is an afterburner (4) forming the second stage. Heat-exchange between the burners takes place via the wall of this body.