Burner Location Research Articles

마이크로 가스터빈용 하이브리드/이중 선회제트 연소기 개발 (Part II: 비반응 유동에 관한 수치해석)

마이크로 가스터빈용 하이브리드/이중 선회제트 연소기의 비반응 유동 및 혼합특성에 관한 수치해석 연구가 수행되었다. 고정된 열부하에서 pilot 버너의 위치, 선회 각 및 방향이 주요 변수로 검토되었다. 결과로서, pilot 버너의 위치, 선회 각 및 방향의 변화는 버너 출구 근처의 난류 유동장, 특히 중앙 재순환영역 및 난류강도의 큰 변화를 초래하며, 화염안정성 및 배기성능의 큰 변화를 동반하게 된다. 실험결과와의 비교를 통해, 하이브리드/이중 선회제트 연소기의 개발을 위하여 화염안정성 및 배기의 측면에서 pilot 버너의 최적 위치, 선회각<TEX>$45^{\circ}$</TEX> 그리고 정방향 선회유동 조건들이 선택되었다. The isothermal flow structure and mixing characteristics of a hybrid/dual swirl jet combustor for micro-gas turbine (MGT) were numerically investigated. Location of pilot burner, swirl angle and direction were varied as main parameters with the identical thermal load. As a result, the variations in location of pilot nozzle, swirl angle and direction resulted in the significant change in turbulent flow field near burner exit, in particular, center toroidal recirculation zone (CTRZ) as well as turbulent intensity, and thus the flame stability and emission performance might be significantly changed. With the comparison of experimental results, the case of swirl angle <TEX>$45^{\circ}$</TEX> and co-swirl flow including optimum location of pilot burner were chosen in terms of the flame stability and emissions for the development of hybrid/dual swirl jet combustor.

Simulation studies on direct ash recycling and reburning technology in a tangentially fired 500 MW pulverized coal boiler

For thermal power generation companies, the use of refined ash (defined as having a loss on ignition (LOI) of less than 6%) has not only made it suitable to produce lightweight aggregate, but has also introduced significant cost benefits through recycling. However, the ash having a high unburned carbon content (greater than 6%) cannot be recycled and still must be disposed of underground and by landfill. In this paper, an ash recycling and reburning technology was examined to improve ash usage in 500MW pulverized coal (PC) boiler and simulation was performed to find the optimal conditions of ash supplying position and its amount that would not affect the boiler condition. Kinetic parameters for the reaction rate of ash were derived from a drop tube furnace (DTF) and adopted to accurately describe the characteristics of high LOI ash. In addition, the simulation results were then validated through real scale tests. Based on the simulation results, this paper suggest that the optimal supply condition for ash reburning is D burner sight window and 4ton/h (with 0.01% of total air) in terms of combustion stability and burnout because the upper burner location has more sufficient oxidizer in the particle pathway as well as maximized mixing effect between coal and oxidizer. The real scale tests evidently represent that ash reburning can be method to make low LOI ash.

Evaluation on cold modeling flow field for a down-fired 600 MWe supercritical boiler with multi-injection and multi-staging: A burner location experimental optimization and its validation by real-furnace measurements

This work presents a burner location optimization by cold modeling experiments and its validation by real-furnace measurements for a new down-fired 600MWe utility boiler with a low-NOx combustion technology. By recording flow field measurements within a 1:20-scaled model of the furnace, cold airflow experiments were conducted at various burner location settings, i.e., the ratio (denoted by Cl) of the distance between the burner centerline and the front (rear) wall to the arch depth is 35%, 39%, 42%, 46%, and 49%, respectively. Meanwhile, at normal full load industrial-size experiments were performed with measurements taken of gas temperatures in the near wing-wall region, carbon content in fly ash, and NOx emissions. At settings of 35% and 39%, flow field and velocity distributions along certain cross-sections as well as penetration depths of downward airflows were well-formed symmetric along the furnace center. At the left three higher settings, a deflected flow field appeared in the lower furnace, with the downward airflow near the rear wall being directed upward earlier than that near the front wall. With increasing the Cl value from 42% to 49%, the flow-field deflection became turbulent. To establish a symmetric flow field along with an appropriate airflow penetration depth, a burner location setup of Cl=39% was finally installed in the furnace. As expected, industrial-size data revealed that with the optimized burner location, excellent furnace performance characterized by symmetric combustion, good burnout, and low NOx emissions, appeared within the furnace.

Numerical Simulation on the Influence of Heating with Different Arrangement of Burners on the High Performance Hydrogen Bell-Type Annealers

The heating bell with burners is an important heating device for the high performance hydrogen bell-type annealers. The arrangement of the burners has an important impact on the heating effect. In this study, we simulated a series of model with different location of burners under the same quantity of burners and the same heating power. The result shows: (1) Under the same quantity of burners and the same heating power, when we increase the number of rows of burners, the maximum temperature inside the furnace could be reduced, and the temperature distribution will become more uniform; (2)When we fixed the number of the row of the burners, if we move the upper burners to higher position to make the arrangement of burners more uniform, the temperature distribution inside the furnace will be more uniform, this will be good for the heat transfer to the higher parts of the annealers, and this will accelerate the heating process, improve the efficiency of annealing, reduce fuel consumption, and extend the life of the inner bell.

On the prediction of fire-induced vent flows using FDS

In an attempt to investigate the accuracy of predictions of fire-induced flow into a compartment by Fire Dynamics Simulator (FDS), a follow-up study was explored by comparing with the Steckler’s experimental data obtained at National Bureau of Standards in 1979. Improvements to the previous study include finer grids, an inclusion of radiative heat in the combustion model, and an increased computational domain. The burner location for the modeling scenarios of fire at corner or against wall are shifted to compensate for the reduced entrainment. The input and set-up changes made to the FDS simulation allowed significant improvements in the prediction of mass flow rates for all three positions of the fire source. However, there is not much improvement for the remaining three parameters being compared: lower layer temperature, smoke layer height, and neutral plane height.

Burnout of pulverized biomass particles in large scale boiler – Single particle model approach

Burning of coal and biomass particles are studied and compared by measurements in an entrained flow reactor and by modelling. The results are applied to study the burning of pulverized biomass in a large scale utility boiler originally planned for coal. A simplified single particle approach, where the particle combustion model is coupled with one-dimensional equation of motion of the particle, is applied for the calculation of the burnout in the boiler. The particle size of biomass can be much larger than that of coal to reach complete burnout due to lower density and greater reactivity. The burner location and the trajectories of the particles might be optimised to maximise the residence time and burnout.

Optimization of coal reburning in a 1 MW tangentially fired furnace

This paper deals with an experimental study on the influence of coal reburn on NO x reduction efficiency, unburned carbon in fly ash and the furnace temperature distribution along the height in a 1 MW (heat input power) tangentially firing furnace with multiple low NO x control technologies. Several variables associated with the reburn system have been investigated in the experiment which includes the air stoichiometry in reburn zone, the location of reburn burner and reburn coal fineness. The optimum location of reburn nozzles has been found where NO x reduction efficiency is highest. With the decrease of reburn coal size (average diameter from 53.69 μm to 11.47 μm), NO x reduction efficiency increases slightly, but the burnout performance of coal is improved noticeably. In the process of coal reburning, the temperature of flue gas is 70–90 °C lower in primary combustion, but 130–150 °C higher at the top of furnace as compared to baseline.

Thermoacoustic Modeling of a Gas Turbine Combustor Equipped With Acoustic Dampers

Abstract In this work, the TA3 thermoacoustic network is presented and used to simulate acoustic pulsations occurring in a heavy-duty ALSTOM gas turbine. In our approach, the combustion system is represented as a network of acoustic elements corresponding to hood, burners, flames and combustor. The multi-burner arrangement is modeled by describing the hood and combustor as Multiple Input Multiple Output (MIMO) acoustic elements. The MIMO transfer function (linking acoustic pressures and acoustic velocities at burner locations) is obtained by a three-dimensional modal analysis performed with a Finite Element Method. Burner and flame analytical models are fitted to transfer function measurements. In particular, the flame transfer function model is based on the time-lag concept, where the phase shift between heat release and acoustic pressure depends on the time necessary for the mixture fraction (formed at the injector location) to be convected to the flame. By using a state-space approach, the time domain solution of the acoustic field is obtained. The nonlinearity limiting the pulsation amplitude growth is provided by a fuel saturation term. Furthermore, Helmholtz dampers applied to the gas turbine combustor are acoustically modeled and included in the TA3 model. Finally, the predicted noise reduction is compared to that achieved in the engine.

Development and Operation Results of Low NOx-High Efficiency Coal Fired New CUF Boiler.

In response to recent demands for effective use of energy and increased awareness of environmental protection, MHI has developed a new CUF boiler capable of ensuring a low NO x emission and burning coal stably at a low air ratio. In the CUF type boiler, its burner is installed at the four surrounding walls having high radiative intensity and the fuel and the air are injected slightly downwards to be fired while they are made to swirl over the entire furnace. Because this boiler type is excellent in fuel ignitability and can maintair a sufficient fuel residence time in its reduction zone, its development has always been oriented towards combustion of hard-to-burn coals such as anthracite. In the CUF boiler newly developed, those features have been adopted towards low NO x and high efficiency. For further decrease of the NO x level, optimum conditions of the burner location and the fuel injection direction were found out using a 1/15 scale cold model test, which made it possible to achieve coal firing at a lower NO x and higher efficiency than ever. Based on these results, a CUF boiler of evaporation 350 t/h was made and this boiler has successfully been operating. Combustion state in the furnace has been found very stable and operation of this boiler using a low air ratio of excess O 2 about 1% is made available. Comparison with the conventional boiler of the same scale shows that there is the effect of NO x decrease by about 30% on a basis of the same unburned carbon ratio in ash.

Compartment fire experiments: Comparison with models

Abstract Twenty full-scale compartment fire experiments suitable for model comparison were conducted. Ceiling jet temperatures, surface heat fluxes and heat transfer coefficients which have not been previously reported are discussed. The ceiling jet temperatures 0·10 m below the ceiling show the effects of compartment ventilation, near-field entrainment conditions and burner location on the ceiling jet. Net and radiant incident heat fluxes to the upper and lower-walls and the floor are estimated. Combined (radiation and convection) interior heat transfer coefficients for the three surfaces are reported. As compartment fire models such as CFAST and FIRST continue to develop in sophistication, it is important that they be compared to experimental data. Data at three heat release rates: 330, 630 and 980 kW, are used to evaluate these comprehensive compartment fire models and two simpler models for the upper-layer gas temperature. CFAST predicts upper-layer gas temperatures 150–260°C hotter than the measured bulk outflow gas temperatures. The increased temperatures appear to be due to insufficient heat transfer through the compartment surfaces. FIRST predicts upper-layer gas temperatures that are slightly cooler (on average, 20C) than the measured bulk outflow gas temperatures. The two simpler models are within 40°C, on average, of the measured upper-layer gas temperatures

A study of thermophoretic transport in a reacting flow with application to external chemical vapor deposition processes

A study has been made of the flow, heat and mass transfer with chemical reactions and thermophoretic transport with application to external chemical vapor deposition processes. The system includes a jet that is emerging from a burner containing fuel (methane), oxygen, nitrogen and silicon tetrachloride which react and form silica soot particles. The flow impinges on a disk which serves as the target for the depositing material. The motion of the particles is determined from the combined effects of thermophoresis, buoyancy and the forced flow leaving the burner. The governing conservation equations, which include the effects of buoyancy, variable properties, chemical reactions and thermophoretic transport have been solved numerically. The effects of the burner location and the disk diameter on particle deposition are studied. The local and average particle deposition, the variation of the deposition efficiency and the heat flux are determined over a range of values of the parameters.

Thermophoretic transport with application to external vapor deposition processes

A study has been made of the flow, heat transfer and thermophoretic transport with application to external vapor deposition processes. In this work the system studied consists of a jet emerging from a burner containing silica soot particles that are impinging on a disk which serves as the target for the depositing material. The motion of the particles is determined from the combined effects of thermophoresis, buoyancy and the forced flow. The governing conservation equations, which include the effects of buoyancy, variable properties and thermophoretic transport have been solved numerically. The effects of the particle distribution at the exit from the burner, the burner location, and the disk dimensions on particle deposition are studied. The local and average particle deposition and heat fluxes and the variation of the deposition efficiency are investigated over a range of values of the parameters.

Room Fire Test for Fire Growth Modeling-A Sensitivity Study

A room test designed according to the ASTM draft standard was used to investigate the effect of various parameters on the contribution of wall and corner fires to compartment fire growth. Location of the burner (against a wall or in a corner), power program of the gas burner ignition source, and com bination of wall linings were varied. An initial series of calibration tests were conducted on ceramic fiber blanket and gypsum board. These tests showed satisfactory instrumentation, good repeatability, and reliable data reduction techniques. The second series were wall and corner tests with Douglas-fir ply wood on the walls in contact with the burner and either ceramic fiber or gyp sum on the ceiling and remaining walls. Notably, fire growth was much faster in the tests with ceramic fiber. We conclude from the data analysis that at least for corner tests, gypsum board should be used for the ceiling and remaining walls as specified in standardized procedures. A burner program of 40 kW for 5 min followed by 160 kW for the next 5 min was the most informative program; it will be used for wall and corner tests in subsequent steps of this ongoing study.

3-D Flow Modeling of a Hazardous Waste Incinerator

A three-dimensional flow model of a hazardous waste incinerator kiln and vertical secondary combustion chamber arrangement was constructed to evaluate critical system parameters. The chamber wall configuration, location and arrangement of burners, and the positioning of the outlet duct were examined to determine the critical secondary combustion chamber gas residence time and mixing of the combustion flows. The scale model consisted of the rotary kiln as a primary combustion chamber, the secondary combustion chamber, two burners, and the exhaust ducting. Flue gas velocities in the model inlets and outlet were maintained to provide a Reynolds numbers equal to the full size unit. Patterns of smoke which were injected into the model inlets were viewed to evaluate flow mixing. Slow motion playback of video tape was used to determine the minimum residence time of flow in the high temperature combustion zone. The results of the model study were used to complete the engineering of a waste incineration system.

Quarter‐scale room‐fire tests of interior finishes

AbstractA technique for estimating fire‐buildup in rooms with combustible interior finish is discussed. Use of the technique resulted in good agreement between fires conducted in one‐quarter‐scale rooms with a doorway opening and those performed in full‐scale rooms. The effects of burner location and heating rate on flashover in a well‐insulated room were also studied to help select a suitable ignition source size and placement for testing of interior‐finish materials.

Interactions of steep-fronted pressure waves with a heterogeneous combustion field

Prcssore-fime-position relations and the simuiitaneous determination of other important combustion parameters have been theoretically and experimentally performed. These results were generated along a rocket combnsior axis during propagation of a strong shock wave running back and forth through an heterogeneous combustion field and reflecting ai the combustor ends. The initial steady*state condition is recognized as being that of a Siquid bipropeiilant droplet spray combustion within the burner, limited by their simultaneous vaporization. Substantial interaction effects between the different axial distributions of mass, impulse, and energy sources, affecting the local energy release and the onset and behavior of a sawtooth-like pressure wave have been investigated. In order to study the pressure-time behavior at different burner locations a short shock tube was mounted in the opposite direction to the combustion gas flow at the downstream end of the combustor. This pulse generator functions as an additional external source of pulse energy to initiate the upstreamrunning shock. Therefore a single steep-fronted pressure pulse could enter the combustor axialiy at any time during the run. The governing unsteady differential equations of the gaseous phase have been solved by applying the numerical Lax-Wendroff two-step procedure, including the simultaneous bipropellant vaporization and the wave reflection at the injector end of the combustor. The initial conditions, as given by solving the steady-state problem at first, were filled to corresponding measurements of the local combustion efficiency. This paper compares some of the recently achieved theoretical results with the corresponding experiments.

Gravitational Diffusion From a Boundary Source in Two-Dimensional Flow

Abstract Convection currents of heated air downwind from a continuous line of gasoline burners at ground level provided an important means of dispersing fog over airfields during the recent war. A study of heat requirements as a function of burner location and cross-wind velocity, conducted by the Iowa Institute of Hydraulic Research in 1943, yielded results which are considered applicable to all similar problems of gravitational diffusion from a boundary source—such, for instance, as the mixing through induced convection of sediment-laden water introduced at the upper surface of a stream. The author presents herewith a general analysis of the problem, based upon solution of the differential equations of energy and diffusion for the assumption of (1) an error distribution of the specific-weight difference over any normal section and (2) a direct proportionality between the mixing length and the standard deviation of the error curve. Experimental results are shown to verify the analysis with good approximation.