A Mathematical Model for Heat Transfer in Combustion Chambers of Steam Generators

1981 ◽  
Vol 103 (3) ◽  
pp. 545-551
Author(s):  
M. G. Gulicˇ ◽  
D. D. Gvozdenac
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Energy Balance ◽  
Combustion Chamber ◽  
Combustion Zone ◽  
Combustion Chambers ◽  
Steam Generators ◽  
Total Heat Transfer ◽  
Hewlett Packard ◽  
Factors Influencing

This paper describes a mathematical model for determining the total heat transfer in combustion chambers of steam generators. The model is based on the energy balance of radiation in a spherical combustion chamber which is divided into a combustion zone and gaseous zone. The model was tested on a Hewlett-Packard Type 9815 A computer with 2008 program memories. Calculations were made for a number of steam generator combustion chambers of different furnace loads for which all important factors were established. The model allows a didactic analysis of factors influencing the process of combustion and heat transfer.

scholarly journals Numerical and Experimental Analysis of Heat Transfer for Solid Fuels Combustion in Fixed Bed Conditions

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 6141
Author(s):  
Wojciech Judt
Keyword(s):  
Heat Transfer ◽  
Combustion Chamber ◽  
Transfer Process ◽  
Heat Load ◽  
Fixed Bed ◽  
Heat Transfer Process ◽  
Biomass Combustion ◽  
Solid Fuels ◽  
Hard Coal ◽  
Combustion Chambers

The paper concerns the analysis of the heat transfer process that occurred during solid fuel burning in fixed bed conditions. The subject of the analysis is a cylindrical combustion chamber with an output of 12 kW heating power equipped with a retort burner for hard coal and biomass combustion. During the research, a numerical and experimental study is performed. The analysis is prepared for various heat load of the combustion chamber, which allowed for the reconstruction of real working conditions for heating devices working with solid fuels combustion. The temperature distribution obtained by the experimental way is compared with results of the numerical modeling. Local distribution of principal heat transfer magnitudes like a heat flux density and a heat transfer coefficient that occurred on the sidewall of the combustion chamber is analyzed. The analysis showed, that the participation of convection and radiation in the overall heat transfer process has resulted from the heat load of the heating device. Research results may be used for improving an analytical approach of design process taking place for domestic and industrial combustion chambers.

Methods for Reducing Emission of Harmful Substances in the Combustion Chambers of GTE and GTP

2018 ◽  
pp. 9-29
Author(s):  
E. M. Komarov
Keyword(s):  
Combustion Chamber ◽  
Residence Time ◽  
Combustion Zone ◽  
Fuel Combustion ◽  
Mixing Zone ◽  
Combustion Chambers ◽  
Lean Mixture ◽  
Flame Tube ◽  
Low Emission ◽  
Harmful Substances

A combustion chamber, as one of the crucial GTE components, plays a significant role in ensuring its environmental characteristics. Therefore, understanding the mechanisms of forming harmful substances (pollutants) and a possibility to predict their emission values, when changing the engine operation parameters and the external conditions, are some of the key issues to ensure ICAO (International Civil Aviation Organization) standards. The solution of these issues allows us to estimate the emission characteristics at the stage of engine design and to develop effective methods for preventing the formation of air pollutants, as well as to increase the efficiency of burning fuels. Since the first limitation introduced by the Committee on Aviation Environmental Protection (CAEP / 1) in 1986 there were several amendments. The (CAEP / 8) standard, which has come into force since January 1, 2014, is already being ready to be replaced by more stringent requirements, i.e. reducing emissions of nitrogen oxides (NOx) by 40% by 2020 (as compared to the (CAEP / 2). As to other pollutants (CO, HC, SN), the trend is similar.Main difficulties in creating combustion chambers with low-emission pollutants arise from the fact that reducing CO and NOx requires mutually opposite measures. A rational combustion chamber design should represent some trade-off between the requirements arising from the task of reducing emissions of these two groups of polluting components. This can be achieved through improving operation of the primary, burnout, and mixing zones, rationally chosen volume of the flame tube (FT), and residence time in the combustion chamber.To have a clearer idea of possible ways to reduce pollutant emission of the GTE combustion chamber, it is necessary to take into account the basic mechanisms of their formation.The main methods of reducing CO emission are based on the physical-and-chemical patterns of its formation:Supporting the mixture composition in the combustion zone to be closer to α = 1.1 ... 1.3;Increasing the combustion zone volume and the residence time in it.The above methods of reducing CO emissions are difficult to implement in low-emission combustion chambers because their using leads to the sharp increase of NOх formation. It is found that only in a very narrow temperature range (flame temperature Тпл = 1650 ... 1900 K) desirable levels of NOх and CO emissions can be simultaneously achieved.To reduce the level of NOх emission, are used the following approaches:-        liquid fuel combustion implemented at a small length of FT with a residence time in the high temperature zone (over 1920 K) 5 ... 6 milliseconds followed by intensive quench in the mixing zone, that is, the principle of "quick burn and quick quench» is used;-        fuel combustion at the temperature of 1750 ± 50 K (i.e. below 1920 K), with an outlet temperature pattern formed through the air feed in the mixing zone or-        from the zone of a combustion chamber flame tube head with no quench of product of combustion.The analytical results of a total scope of developments in reducing pollutant emissions allow us to distinguish the following standard fuel combustion technologies in GTE combustion chambers, which meet the available environmental requirements:1)      use of burning the lean pre-mixed fuel in "dry" combustion chambers (This technology process uses the following schemes: RQL (Rich-Quench-Lean) – rich mixture combustion, followed by rapid air blending and lean mixture afterburning; LPP (Lean Premixed Pre-vaporized) - combustion of a lean premixed and vaporized mixture; LDI (Lean Direct-Injection) - combustion with lean mixture injection directly into the combustion zone;2)      catalytic combustion of a fuel-air mixture;3)      use of "wet" combustion chambers with diffusion flame and water injection (steam);4)      additional use of catalytic cleaning of GTP outlet gases.At present, natural gas combustion chambers with emission of NOx and CO <10ppm are under design. This is almost the lowest achievable level for the operating conditions under consideration. In designing such combustion chambers a main task is to develop and improve methods that allow calculating the combustion kinetics of a gas mixture, improving the software systems for calculating and obtaining reliable data on emission of harmful substances, and also to develop experimental methods for creating and full-scale engineering of the low-emission combustion chambers for stationary units and advanced aircraft engines. The presented methods for reducing emission of harmful substances, namely improving techniques to feed fuel, zone arrangement of combustion, use of catalysts in the combustion chamber and at the outlet of the plant, when used, should result not only to reducing emissions, but also to improving the other important combustion chamber characteristics, especially extension of steady combustion limits. Studies to obtain ultra-low emission levels, based on the burning concept of the lean homogeneous mixture in the combustion chamber, are at an early stage. It is necessary to solve a number of important problems, such as a problem of «lean» flameout, of flash back, and also ensuring a sufficient evaporation of fuel and its mixing with air.

Effect of Vortex Flow on Heat Transfer to Combustion Chamber Wall

2004 ◽  
Author(s):  
S. Jahangirian ◽  
M. Abarham ◽  
A. Ghafourian ◽  
M. H. Saidi
Keyword(s):  
Heat Transfer ◽  
Combustion Chamber ◽  
Wall Temperature ◽  
Wide Spectrum ◽  
Swirl Flow ◽  
Combustion Chambers ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Bidirectional Flow ◽  
Further Development

A new experimental facility was designed, fabricated and tested to model and study the effect of bidirectional swirl flow on the rate of heat transfer to combustion chamber walls in many applications. Heat transfer to combustion chamber walls is an unwanted phenomenon. Reduction of this heat transfer can result in time and cost saving methods in design and fabrication of combustion chambers. The experimental study was performed by using propane and air with oxygen as fuel and oxidizer respectively. The location of injection ports and geometry of combustion chamber are flexible and could be varied. Tests were performed with different mass flow rates of fuel and oxidizer. For the same flow rates and with the presence of bidirectional flow, a wall temperature reduction of up to 50% was observed. In cases where only some of the oxidizer was injected from the chamber end to generate the bidirectional swirl flow, highest efficiency and lowest wall temperature existed. This can be due to better mixing of fuel and oxidizer and absence of hot spots in the combusting core. Further development of this technique enables combustion chamber manufacturers in a wide spectrum of industries such as gas turbine manufacturers to use less expensive and more available material in their production of combustors.

scholarly journals The advisability of using combustion chambers with a toroidal recirculation-mixing zone in small-sized gas turbine engines

2018 ◽  
Vol 209 ◽  
pp. 00019
Author(s):  
Michael Yurievich Orlov ◽  
Oleg Vladimirovich Kolomzarov ◽  
Vladislav Mikhailovich Anisimov ◽  
Nikita Igorevich Gurakov ◽  
Nikolai Sergeevich Mironov
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Combustion Zone ◽  
Gas Turbine Engine ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Mixing Zone ◽  
Combustion Chambers ◽  
Theoretical Justification ◽  
Turbine Engine

The interrelations between the size of the gas turbine engine (GTE) and the size and workflow of the combustion chamber (CC) were considered. On the base of analysis of workflow organization the design of CC with toroidal recirculation mixing zone was proposed. The theoretical justification of chosen design was carried out on the base of comparison of combustion volumes, which formed in traditional CC with swirlers and in proposed CC. The comparison of combustion volumes, schematic display of combustion zones with a discrete flame and a combined combustion zone were given.

scholarly journals Comparison of soot radiation in diesel flame given by mathematical model and by experimental data

2007 ◽  
Vol 29 (3) ◽  
pp. 293-301
Author(s):  
Bui Van Ga ◽  
Tran Van Nam ◽  
Nguyen Ngoc Linh
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mathematical Model ◽  
Combustion Chamber ◽  
Engine Speed ◽  
Soot Formation ◽  
Radiation Heat Transfer ◽  
Formation Model ◽  
Radiation Heat ◽  
Maximum Value

An integral unidirectional model is established to calculate radiation heat transfer of Diesel flame in the open air and in combustion chamber of engine. Based on the temperature and soot fraction given by the flamlet theory and soot formation model of Tesner-Magnussen, radiation of soot particulate cloud at different positions of flame is determined and compared with experimental data obtained by the two-color method.The results show that the radiation given by the model is 203 lower than that produced by experiments on the stationary flame in open air. Soot radiation intensity in the Diesel engine increases in function of load and engine speed regimes and its maximum value (about 2000 kW/m2) is reached when the highest pressure is attained in combustion chamber.

Heat Transfer to Unfrosted Wind Convectors: Mathematical Modeling and Comparison With Experimental Results

1990 ◽  
Vol 112 (4) ◽  
pp. 280-286 ◽  
Author(s):  
D. P. Finn ◽  
P. F. Monaghan ◽  
P. H. Oosthuizen
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Longwave Radiation ◽  
Heat Pumps ◽  
Total Heat ◽  
Simulation Studies ◽  
Optimum Conditions ◽  
Total Heat Transfer ◽  
Mean Square Difference ◽  
The Mathematical Model

Wind convectors are an alternative air source evaporator system for heat pumps. This paper describes a mathematical model that calculates the heat transfer to wind convectors when forced convection conditions prevail and when wind convector surface frost and rainfall are absent. The mathematical model is validated and predicts heat transfer to within 8 percent of experimental data based on a root mean square difference estimation. Further simulation studies show that heat transfer to wind convectors is dominated by sensible convection and latent heat transfer, that longwave radiation contributes less than 5 percent of total heat transfer and that solar radiation can contribute up to 25 percent of total heat transfer under optimum conditions.

scholarly journals New Theoretical and Methodological Approaches to the Study of Heat Transfer in Coal Dust Combustion

Energies ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 136
Author(s):  
Evgeniy Toropov ◽  
Konstantin Osintsev ◽  
Sergei Aliukov
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Coal Dust ◽  
Thermal Characteristics ◽  
Combustion Chambers ◽  
Methodological Approaches ◽  
Methodological Principles

The existing theories of heat transfer in combustion chambers of boiler units fail to take into account a number of important factors that affect the reliability of results, and the methodological approaches to optimizing combustion processes can be revised in view of the spatial and temporal parameters of flame. Hence, the research aimed to improve the fundamental theoretical and methodological principles of studying heat transfer in coal dust combustion in the combustion chambers of industrial steam generators. The authors proposed to extend the theory of heat transfer with the mathematical description of particle size distribution of coal dust. In addition, the authors used the developed mathematical model of coal dust combustion based on a continuous curve of the particle size distribution in the ensemble. The mathematical model is consistent with the aeromechanical and thermal characteristics of flame. This work introduced a concept of flame continuum as a continuous medium, where the processes of combustion and heat transfer are studied. To achieve the research aim, in this paper, the methods of combustion chamber zoning, the equations of stationary and non-stationary heat conduction, radiation, and convective heat transfer, were used. These methods were tested on a number of high-temperature units.

Effect of Vortex Flow on Heat Transfer to Combustion Chamber Wall

2006 ◽  
Vol 129 (2) ◽  
pp. 622-624 ◽  
Author(s):  
A. Ghafourian ◽  
M. H. Saidi ◽  
S. Jahangirian ◽  
M. Abarham
Keyword(s):  
Heat Transfer ◽  
Combustion Chamber ◽  
Wall Temperature ◽  
Hot Spots ◽  
Vortex Flow ◽  
Swirl Flow ◽  
Experimental Facility ◽  
Combustion Chambers ◽  
Flow Rates ◽  
Bidirectional Flow

A new experimental facility was designed, fabricated, and tested to model and study the effect of bidirectional swirl flow on the rate of heat transfer to combustion chamber walls. Reduction of this heat transfer can result in time and cost of design and fabrication methods of combustion chambers. The experimental study was performed using propane and air with oxygen as fuel and oxidizer, respectively. For similar flow rates, in cases where bidirectional flow was present, wall temperature reductions of up to 70% were observed. In cases where only some of the oxidizer was injected from the chamber end to generate the bidirectional swirl flow, the lowest wall temperature existed. This can be due to better mixing of fuel and oxidizer and absence of hot spots in the combustion core.

Factors Influencing Combustion Chamber Wall Temperatures in a Liquid-Cooled, Automotive, Spark-Ignition Engine

1985 ◽  
Vol 199 (3) ◽  
pp. 207-214 ◽  
Author(s):  
I C Finlay ◽  
D Harris ◽  
D J Boam ◽  
B I Parks
Keyword(s):  
Heat Transfer ◽  
Combustion Chamber ◽  
Cylinder Head ◽  
Nucleate Boiling ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Chamber Wall ◽  
Transfer Model ◽  
Factors Influencing ◽  
Good Agreement

The influence on cylinder head temperatures of parameters such as cylinder head material, coolant composition, pressure, temperature and velocity was investigated. Each of these parameters was systematically varied and its influence on combustion chamber wall temperature measured. Good agreement is shown between the measured values and corresponding predictions from a heat transfer model incorporating forced-convective, sub-cooled, nucleate boiling. The results suggest that nucleate boiling can play an important role in the transfer of heat from cylinder head to coolant.

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