Showing papers on "Combustion chamber published in 1999"

Large-Eddy Simulation of a Gas Turbine Combustor Flow

Abstract: Large-eddy simulation (LES) of turbulent premixed reacting flows in a gas turbine combustor (General Electric's lean premixed dry low-NOx LM6000) has been carried out to evaluate the potential of LES for design studies of realistic hardware. A flamelet model for the premixed flame is combined with a dynamic model for the subgrid kinetic energy to simulate the propagation of the turbulent flame in this high swirl and high Reynolds number flow. Comparison of the computed results with experimental data indicate good agreement in spite of relatively coarse grid resolution employed in the LES. These results provide significant confidence that LES capability for design studies of practical interest is feasible in the near future.

A Study of the Homogeneous Charge Compression Ignition Combustion Process by Chemiluminescence Imaging

Abstract: An experimental study of the Homogeneous Charge Compression Ignition (HCCI) combustion process has been conducted by using chemiluminescence imaging. The major intent was to characterize the flame structure and its transient behavior. To achieve this, time resolved images of the naturally emitted light were taken. Emitted light was studied by recording its spectral content and applying different filters to isolate species like OH and CH.Imaging was enabled by a truck-sized engine modified for optical access. An intensified digital camera was used for the imaging. Some imaging was done using a streak-camera, capable of taking eight arbitrarily spaced pictures during a single cycle, thus visualizing the progress of the combustion process. All imaging was done with similar operating conditions and a mixture of n-heptane and iso-octane was used as fuel.Some 20 crank angles before Top Dead Center (TDC), cool flames were found to exist. They appear with a faint structure, evenly distributed throughout the combustion chamber. There was no luminosity recorded between the end of cool flames and the start of the main heat release. Around TDC the main heat release starts. Looking at a macro scale, we find that the charge starts to burn simultaneously at arbitrary points throughout the charge. Since the thermal boundary layer is colder than the bulk of the charge, the local heat release is delayed close to the walls. As a result, the total heat release is slowed down. Ensemble averaged1 images show this wall boundary effect clearly when plotted against CAD. The peak intensity at the main combustion event is one order of magnitude greater than that of the cool flame and the structure is a lot more protruding.Since spontaneous emission imaging is a line-of-sight integration, the flame structure appears a bit smeared. The micro scale structure is very similar from one cycle to another, but there are large variations between cycles on the macro scale. (Less)

Performance Increases for Gas-Turbine Engines Through Combustion Inside the Turbine

Abstract: In a conventional gas-turbine engine, fuel is burned in separate combustors before the heated high-pressure gas expands through the turbine to provide shaft power for the compressor, fan, propellers, helicoptor rotors, or an electric generator in a ground-based powerplant application. It is proposed in this paper that combustion be continued purposely inside the turbine to increase the efficiency and specific thrust/power of the engine. We term such a turbine with combustion a turbine-burner. A thermodynamic cycle analysis is performed to demonstrate the performance gains of turbojet engines with the turbine burner over the conventional turbojets. Ground-based gas-turbine engines for power generation are also analyzed, with the results showing even better performance gains compared without conventional engines. A mixing-layer analysis with combustion in an accelarated flow similar to the conditions in the turbine burner shows that there is also potential reduction of NOr by using the turbineburner compared with conventional combustors, where the burning is at a constant pressure. Challenges and related research issues that must be addressed to use the turbine-burner technology are identified in this paper.

Nonlinear heat-release/acoustic model for thermoacoustic instability in lean premixed combustors

Abstract: Lean premixed combustors, such as those used in industrial gas turbines to achieve low emissions, are often susceptible to thermoacoustic combustion instabilities, which manifest themselves as pressure and heat release oscillations in the combustor. These oscillations can result in increased noise and decreased durability due to vibration and flame motion. A physically based nonlinear parametric model has been developed that captures this instability. It describes the coupling of combustor acoustics with the rate of heat release. The model represents this coupling by accounting for the effect of acoustic pressure fluctuations on the varying fuel/air ratio being delivered to the flame, causing a fluctuating heat release due to both fuel air ratio variations and flame front oscillations. If the phasing of the fluctuating heat release and pressure are proper, an instability results that grows into a limit cycle. The nonlinear nature of the model predicts the onset of the instability and additionally captures the resulting limit cycle. Tests of a lean premixed nozzle run at engine scale and engine operating conditions in the UTRC single nozzle rig, conducted under DARPA contract, exhibited instabilities. Parameters from the model were adjusted so that analytical results were consistent with relevant experimental data from this test. The parametric model captures the limit cycle behavior over a range of mean fuel air ratios, showing the instability amplitude (pressure and heat release) to increase and limit cycle frequency to decrease as mean fuel air ratio is reduced.

Effect of Air Preheat Temperature and Oxygen Concentration on Flame Structure and Emission

Abstract: The structure of turbulent diffusion flames with highly preheated combustion air (air preheat temperature in excess of 1150°C) has been obtained using a specially designed regenerative combustion furnace. Propane gas was used as the fuel. Data have been obtained on the global flame features, spectral emission characteristics, spatial distribution of OH, CH, and C 2 species, and pollutant emission from the flames. The results have been obtained for various degrees of air preheat temperatures and O 2 concentration in the air. The color of the flame was found to change from yellow to blue to bluish-green to green over the range of conditions examined. In some cases a hybrid color flame was also observed. The recorded images of the flame photographs were analyzed using coloranalyzing software The results show that thermal and chemical flame behavior strongly depends on the air preheat temperature and oxygen content in the air. The flame color was observed to be bluish-green or green at very high air preheat temperatures and low-oxygen concentration. However, at high-oxygen concentration, the flame color was yellow. The flame volume was found to increase with increase in air-preheat temperature and decrease in oxygen concentration. The flame length showed a similar behavior. The concentrations ofOH, CH, and C 2 increased with an increase in air preheat temperatures. These species exhibited a two-stage combustion behavior at low-oxygen concentration and single-stage combustion behavior at high-oxygen concentration in the air. Stable flames were obtained for remarkably low equivalence ratios, which would not be possible with normal combustion air. Pollutant emission, including CO 2 and NO,, was much lower with highly preheated combustion air at low O 2 concentration than with normal air. The results also suggest uniform flow and flame thermal characteristics with conditioned, highly preheated air. Highly preheated air combustion provides much higher heat flux than normal air, which suggests direct energy savings and a reduction of CO 2 to the environment. Colorless oxidation of fuel has been observed under certain conditions.

Transient Turbulent Gaseous Fuel Jets for Diesel Engines

Abstract: Existing data on transient turbulent jet injection in to large chambers demonstrates self-similar behavior under a wide range of conditions including compressibility, thermal and species diffusion, and nozzle under expansion. The Jet penetration distance well downstream of the virtual origin is proportional to the square root of the time and the fourth root of the ratio of nozzle exit momentum flow rate to chamber density. The constant of proportionality has been evaluated by invoking the concept of Turner that the flow can be modeled as a steady jet headed by a spherical vortex. Using incompressible transient jet observations to determine the asymptotically constant ratio of maximum jet width to penetration distance, and the steady jet entrainment results of Ricou and Spalding, it is shown that the penetration constant is 3 ± 0.1. This value is shown to hold for compressible flows also, with substantial thermal and species diffusion, and even with transient jets from highly under-expanded in which, as in diesel engine chambers with gaseous fuel injection, the jet is directed at a small angle to one wall of the chamber. In these tests, with under expanded nozzles. Observations of transient jet injection have been made in a chamber in which, as in diesel engine chambers with gaseous fuel injection, the jet is directed at a small angle to one wall of the chamber. In these tests, with under-expanded nozzles it was found that at high nozzle pressure ratios, depending on the jet injection angle, the jet penetration can be consistent with a penetration constant of 3. At low pressure ratios the presence of the wall noticeably retards the penetration of the jet.

High efficiency low pollution hybrid brayton cycle combustor

Abstract: A power generating system is described which operates at high pressure and utilizes a working fluid consisting of a mixture of compressed non-flammable air components, fuel combustion products and steam. The working fluid exiting the power generating system is substantially free of NOx and CO. Working fluid is provided at constant pressure and temperature. Combustion air is supplied by one or more stages of compression. Fuel is injected at pressure as needed. Substantially all of the oxygen in the compressed air is consumed when the fuel is burned. Inert liquid is injected at high pressure to produce an inert mass of high specific heat diluent vapor for use for internal cooling of the combustion chamber. The use of non-flammable liquid injection inhibits the formation of pollutants, increases the efficiency and available horsepower from the system, and reduces specific fuel consumption. Control systems allow the independent control of the quantity, temperature and pressure of the air, fuel and non-flammable liquid introduced in the combustion chamber allowing control of the maximum temperature and average temperature within the combustion chamber as well as the temperature of the exhaust from the combustion chamber. Substantially all of the temperature control of the system is provided by the latent heat of vaporization of the inert liquid, which is preferably water, the latent heat of vaporization counteracting the heat generated by combustion of the fuel. If the injected water contains inorganic or organic contaminants, they are collected as a molten or solid residue or, if flammable, ignited by the flame.

Propulsive Performances of Pulsed Detonations

Abstract: The propulsive potential of a reactive mixture that uses detonation as a combustion process is studied. An experimental set up is built up to determine the thrust and the impulse developed in single and multi-operating cycles by the detonation products of a reactive mixture contained in a cylindrical combustion chamber (CC). One end of the CC, called the thrust wall (TW), is closed and supports the thrust. The other end is open into atmosphere for the exhaust of the detonation products. The detailed flow features are experimentally investigated by means of pressure gauges inside the CC and in the immediate vicinity of open-ended of CC. The specific impulse Isp reached in our device, with C2H4 = 3 O2 as a detonative mixture, is about 200 s. The overpressure profiles recorded on the TW show clearly that the flow inside the CC is self-similar. Consequently, a relationship between Isp and the Chapman Jouguet's characteristics of the detonative mixture is established. The maximum operating frequency can be lin...

Effects of thermal barrier coating on a turbocharged diesel engine performance

Abstract: Thermal barrier ceramic coatings are successfully used for applications in diesel engines and in the combustion chamber of gas turbine engines, e.g., for nozzle guide vanes, turbine blades, cylinder liners and heads. An experimental investigation into the effects of ceramic coatings on the performance of a diesel engine and exhaust emissions was conducted. Ceramic coatings can eliminate visible smoke, inhibit the formation of NOx, reduce CO and particulate emissions, and improve combustion efficiency. The performance of the diesel ceramic coating was tested on a hydraulic engine dynamometer. The coatings are being evaluated for their ability to control particulate emissions, for emissions in exhaust gases for smoke, horsepower, speed and fuel rate. CO and hydrocarbon levels were lower than baseline levels.

Dynamic control system and method for catalytic combustion process and gas turbine engine utilizing same

Abstract: A unique and useful dynamic control system for the control of a catalytic combustion system for use on a dynamic plant, preferably, a gas turbine engine (14). The dynamic control system facilitates the replacement of conventional flame combustion systems with catalytic combustion systems. A method of controlling the catalytic combustion process comprises the steps of calculating a mass flow of air introduced into the combustor, monitoring a flow of fuel to be combusted within the combustor (32), monitoring a temperature of the air introduced into the combustor (32), calculating an inlet temperature set point based on the mass flow and fuel flow, and controlling a pre-burner (54) to heat the air based on the inlet temperature set point, the mass flow, and the temperature of the air. Further, the mass flow may be estimated based on ambient air temperature and pressure, and compressor (20) speed. A catalytic combustion gas turbine system is also presented, the operation of which is controlled by a dynamic plant controller (34) which generates a fuel flow rate demand signal to control the flow of fuel to be combusted in response to dynamic plant demands.

Method for ignition of flameless combustor

Abstract: A combustor method and apparatus is provided. The method utilizes flameless combustion with one or more of three improvements to enhance ignition of the flameless combustor. A catalytic surface can be provided within a combustion chamber to provide flameless combustion at least in the vicinity of the catalytic surface at a temperature that is much lower than the autoignition temperature of fuel in air without the presence of the catalytic surface. Nitrous oxide or supplemental oxygen may also be used as an oxidant either instead of air or with air to reduce ignition temperatures. Further, electrical energy can be passed through the fuel conduit, raising the temperature of the conduit to a temperature above which the fuel will ignite when combined with the oxidant.

Integrated power module

Abstract: An integrated power module for generating thermal and electrical power is provided within a housing (110) which includes inlets for fuel (156) and for air (112), a reformer chamber (116), a fuel cell stack (118), and a combustion chamber (120). Oxygen-containing gas, such as air, is introduced into the module along path (114) in one direction in heat-exchange relationship with reaction products produced in the reaction chamber traveling in an adjacent path, preferably in an opposite direction, to preheat the incoming oxygen-containing gas. A nozzle (169) having an injector for the fuel and for the oxygen-containing gas delivers these gases to the interior of the reformer chamber, where the ignition is supplied by a suitable device. The reaction products from the reformer chamber are fed to a fuel cell which will consume certain of the reaction products, such as hydrogen gas, with oxygen provided from the reaction chamber acting as an oxidizing gas. Exchange between a cathode and an anode will effect the generation of current, as well as the production of water, which normally will be absorbed as steam and passed from the fuel cell. The current generated by the fuel cell can be delivered externally to a user, while hydrogen may be combusted downstream in the combustion chamber to provide an added thermal energy source for heating. In alternative embodiments of the power module, the fuel cell is used as a shift reactor and hydrogen purification device. The primary product of this module is purified hydrogen gas in addition to heat.

Active control of combustion instability in a liquid-fueled low-NOx combustor

Abstract: A practical active control system for t nitigation of combustion instability has been designed and demonstrated in a lean, premixed, single-nozzle combustor at realistic engine operating conditions A full-scale engine fuel nozzle was modified to incorporate a simple fuel flow actuator Results indicate that the system was capable of reducing pressure fluctuations by 82 percent (15 dB or 56×) while maintaining or reducing NO x and CO emissions levels

Combustion chamber comprising mixing ducts with fuel injectors varying in number and cross-sectional area

Abstract: A three stage lean burn combustion chamber ( 28 ) comprises a primary combustion zone ( 36 ), a secondary combustion zone ( 40 ) and a tertiary combustion zone ( 44 ). Each of the combustion zones ( 36,40,44 ) is supplied with premixed fuel and air by respective fuel and air mixing ducts ( 76,78,80,92 ). The primary fuel and air mixing ducts ( 78,78 ) comprise first and second radial flow swirlers ( 60,62 ). The primary fuel injectors ( 64,66 ) inject fuel into the first and second swirlers ( 60,62 ). The primary fuel injectors ( 44,66 ) and the first and second swirlers ( 60,62 ) are arranged such the fuel to air ratio of the fuel and air flowing from the passages ( 61 ) of the first swirler ( 60 ) into the primary combustion zone ( 36 ) is different to the fuel to air ratio of the fuel and air flowing from the passages ( 65 ) of the second swirler ( 62 ) into the primary combustion zone ( 36 ). This produces an axial distribution of fuel in the primary combustion zone ( 36 ) which reduces the generation of harmful vibrations in the combustion chamber ( 28 ).

Air separation process integrated with gas turbine combustion engine driver

Abstract: A method for the separation of a feed gas mixture comprising oxygen and nitrogen in which an oxidant gas and fuel are combusted in a combustion engine to generate shaft work and a hot exhaust gas, the feed gas mixture comprising oxygen and nitrogen is compressed, and the resulting compressed feed gas mixture is separated into two or more product gas streams with differing compositions. The shaft work of the combustion engine is utilized to provide at least a portion of the work required for compressing the feed gas mixture, one of the product gas streams by is heated by indirect heat exchange with the hot exhaust gas from the combustion engine, and the resulting heated product gas is work expanded to generate shaft work and yield an expanded product gas stream. The combustion engine may be a gas turbine combustion engine.

Optoelectric measuring device for monitoring combustion processes

Abstract: An optoelectronic measuring device for monitoring combustion processes in a combustion chamber of an internal combustion engine during operation is provided with optical sensors which are connected to an evaluation unit. The optical sensors may be located in a seal element bounding the combustion chamber. To obtain high measuring quality in a simple manner, the optical sensors each include a lens assembly having a focusing lens whose flat end opposite the combustion chamber is coincident with the focal plane of the focusing lens and is abutted by an end of at least one optical fiber.

A dual fuel nozzle

Abstract: A dual fuel nozzle is provided with two different size injection holes. The first injection holes have larger diameters and are used only for injecting gaseous fuel into a combustion chamber. On the other hand, the second injection nozzles have smaller diameters and are used for injecting either gaseous fuel or liquid fuel as required. When gaseous fuel is used, if the fuel injection amount is large or medium, both of the first and the second injection holes or first injection holes only are used for injecting gaseous fuel depending upon the required fuel injection amount. When the fuel injection amount is low, only the second injection hole is used for injecting gaseous fuel. Therefore, the pressure drop across the fuel nozzle can be kept at sufficiently high level even when the fuel injection amount is low, and thereby combustion vibration is suppressed. Further, when liquid fuel is used, a premixed fuel and steam mixture is injected from the second injection holes. This also keep the pressure drop across the fuel nozzle at high level in order to suppress combustion vibration when the fuel injection amount is low.

On emerging furnace design methodology that provides substantial energy savings and drastic reductions in CO2, CO and NOx emissions

Abstract: Recent developments in heat recovery systems allow for preheating of combustion air up to temperatures of 1300 °C and, thus, fuel savings up to 60% are achievable. In conventional burner/furnace designs, the higher the combustion air temperature the higher the NO x emissions. However, the most recent developments allow for low NO x combustion using high temperature combustion air. The objective of this paper is to establish conditions under which industrial furnaces should be operated in order to maximize the efficiency and minimize the pollutant emissions including carbon dioxide. To this end, semi-industrial scale experiments have been carried out using natural gas and vitiated air at 1300 °C. A Nippon Furnace Kogyo burner that features a central air jet and two fuel gas injectors was used. Comprehensive in-furnace measurements of velocities, temperature, gas composition (O 2 , CO 2 , CO, H 2 , NO, CH 4 ) and radiation have been carried out. The furnace was operated under conditions resembling a well-stirred reactor; the temperature and chemistry fields were uniform all over the furnace. Almost the whole furnace volume was filled with combustion products containing 2-3% oxygen at temperatures in the range 1350-1450 °C, despite the high temperature (1300 °C) of the vitiated air. The natural gas jets entrained many of the combustion products before they mixed with combustion air. This mode of combustion resulted in high and uniform heat fluxes and low NO x and CO emissions. It was concluded that industrial furnaces of tomorrow are likely to be designed as well-stirred reactors equipped with high efficiency heat regenerators. Conventional burners will be either replaced with individual fuel and air injectors or substantially redesigned to facilitate uniformity of Combustion conditions within the furnace.

Modeling Transfer Matrices of Premixed Flames and Comparison With Experimental Results

Abstract: A combined analytical/experimental investigation of the thermoacoustic properties of a gas turbine burner with a premixed, turbulent, swirl-stabilized flame is presented. In an enclosed flame, an interaction occurs between acoustic fluctuations and non-steady heat release, which may lead to thermoacoustic instabilities. This interaction may be characterized by the transfer matrix of the burner with flame. The transfer matrix describes the coupling between fluctuations of acoustic pressure and velocity on both sides of burner and flame, incorporating also the effects of heat release fluctuations on the acoustic quantities. The transfer matrix has been modeled and validated with experimental results. For the burner, an analytical model is proposed, which is based on the Bernoulli equation for instationary flow through compact elements. The model is based on the Rankine-Hugoniot relations across a thin heat source. The fundamental assumption underlying the model is that acoustic fluctuations cause modulations of fuel concentrations at the fuel injector, which result, after a certain time lag, in a fluctuating heat release rate at the flame. The oscillating heat release couples with pressure and velocity fluctuations in the combustion chamber, thereby creating a feedback loop between combustor acoustics and flame dynamics which may result in self-excited combustion instability.The transfer matrix of the burner with flame has been determined experimentally in an atmospheric combustion test facility. The test rig was equipped with loudspeakers and microphones in order to measure the response to an acoustical excitation. Our new flame model shows to be in agreement with the measured results.Copyright © 1999 by ASME

Method and device producing co2 gas for trapping insects

Abstract: An insect trapping device generates its own insect attractants of carbon dioxide (CO2), heat and water vapor through catalytic conversion (84) of a hydrocarbon fuel in a combustion chamber (68). The hot insect attractants generated in the combustion chamber are diluted and cooled to a temperature above ambient temperature and below about 115 ~F by mixing with air, and then the mixture is exhausted downward through the exhaust tube (48). A counterflow of outside air (52) is drawn into the trap through the suction tube (32) that concentrically surrounds the exhaust tube. Biting insects are captured in a porous, disposable bag (34) connected to the other end (36) of the suction tube. A thermoelectric generator, including thermoelectric modules (102) coupled to the combustion chamber generate power for fans (38, 64) that provide the exhaust flow and the suction flow. Additional chemical attractants may be used with the device to make the trap even more effective. The trap may be adapted for trapping different types of insects by adjusting airflow velocities and attractants.

Control device for direct injection engine

Abstract: A control device for a direct injection engine having a catalyst provided in an exhaust passage for converting exhaust gases and an injector for injecting fuel directly into a combustion chamber, includes a temperature state identifier for judging the temperature state of the catalyst, a load condition detector for sensing engine load conditions, and a fuel injection controller for controlling fuel injection from the injector. The fuel injection controller performs quick light-off control operation by causing the injector to inject fuel in one-time injection mode during a compression stroke in a specific low-load operating range of the engine when the catalyst is in its unheated state where its temperature is below its activation temperature, and switching the mode of fuel injection to intake-compression stroke split injection mode in a specific high-load operating range of the engine.

A Mechanism of Combustion Instability in Lean Premixed Gas Turbine Combustors

Abstract: There has been increased demand in recent years for gas turbines that operate in a lean, premixed (LP) mode of combustion in an effort to meet stringent emissions goals. Unfortunately, detrimental combustion instabilities are often excited within the combustor when it operates under lean conditions, degrading performance and reducing combustor life. To eliminate the onset of these instabilities and develop effective approaches for their control, the mechanisms responsible for their occurrence must be understood.This paper describes the results of an investigation of the mechanisms responsible for these instabilities and approaches for their control. These studies found that combustors operating in a LP mode of combustion are highly sensitive to variations in the equivalence ratio (ϕ) of the mixture that enters the combustor. Furthermore, it was found that such ϕ variations can be induced by interactions of the pressure and flow oscillations with the reactant supply rates. The ϕ perturbations formed in the inlet duct (near the fuel injector) are convected by the mean flow to the combustor where they produce large amplitude heat release oscillations that drive combustor pressure oscillations. It is shown that the dominant characteristic time associated with this mechanism is the convective time from the point of formation of the reactive mixture at the fuel injector to the point where it is consumed at the flame. Instabilities occur when the ratio of this convective time and the period of the oscillations equals a specific constant, whose magnitude depends upon the combustor design. Significantly, these predictions are in good agreement with available experimental data, strongly suggesting that the proposed mechanism properly accounts for the essential physics of the problem. The predictions of this study also indicate, however, that simple design changes (i.e., passive control approaches) may not, in general, provide a viable means for controlling these instabilities, due to the multiple number of modes that may be excited by the combustion process. This conclusion indicates that active control strategies may be necessary for controlling these instabilities.Copyright © 1999 by ASME

Spark-assist type self-ignition engine

Abstract: An engine comprising a spark plug and a fuel injector in a combustion chamber and a temperature sensor used to judge if the gas temperature in the combustion chamber is a temperature at which self-ignition occurs when a spark is generated. Based on this judgement, a valve timing device is used to control the opening timing of the intake valve and maintain the gas temperature at a temperature at which self-ignition occurs when a spark is generated.

Water injection amount control system for fuel and water injection engine

Abstract: A water injection amount control system for a fuel and water injection engine, comprises running state detecting unit for detecting the running state of the engine; an EGR system for recirculating part of exhaust gas of the engine to a combustion chamber of the engine; EGR system operating state detecting unit for detecting or estimating the operating state of the EGR system; water injection amount regulating unit for regulating an amount of water to be injected to the combustion chamber of the engine; and control unit for controlling the operation of the water injection amount regulating unit: wherein the system is arranged to have water injection amount setting unit for deciding a water injection amount based on information from the running state detecting unit and on the operating state of the EGR system detected by the EGR system operating state detecting unit, so that the control unit controls the operation of the water injection amount regulating unit based on the water injection amount decided by the water injection amount setting unit.

Improved power plant with carbon dioxide capture

Abstract: Method for low pollution power generation by combusting a fuel with a supply of highly concentrated oxygen in a combustion chamber (714), to which recirculated combustion products are introduced for temperature control, characterized in that all or parts of the combustion products are cooled (727) to an appropriate temperature which keeps all or most of the water vapor from condensing from said products, before said products are compressed and recirculated to the combustion chamber.