High Temperature Air Combustion (HiTAC) Phenomena and its Thermodynamics

2014 ◽  
Author(s):  
Nabil Rafidi ◽  
Wlodzimierz Blasiak ◽  
Ashwani K. Gupta
Keyword(s):  
High Temperature ◽  
Energy Savings ◽  
Combustion Process ◽  
Point Of View ◽  
Low Oxygen ◽  
High Temperature Air Combustion ◽  
Improve Efficiency ◽  
Thermodynamic Irreversibility ◽  
Combustion Processes ◽  
Low Oxygen Concentration

The fundamentals and thermodynamic analysis of High Temperature Air Combustion (HiTAC) technology is presented with focus on industrial furnaces as they are amongst the major energy users. The HiTAC is characterized by high temperature of combustion air having low oxygen concentration. This study provides a theoretical analysis of HiTAC a process from the thermodynamic point of view. The results demonstrate the possibilities of reducing thermodynamic irreversibility of combustion by considering an oxygen-deficient combustion process that utilizes both gas- and heat-recirculation. Furthermore, combustion with the use of oxygen (in place of air) is also analyzed. The results showed that a system which utilizes oxygen as an oxidizer results in higher 1st and 2nd law efficiencies as compared to the case with air as the oxidizer. This study is aimed at providing technical guidance to further improve efficiency of a combustion process which show very small temperature increases due to mild chemical reactions. The significant of these findings are now widely used in industrial furnaces with singular successes on energy savings, pollution reduction and reduced size of the equipment. The exergy analysis too can be used as a technical tool to improve efficiency in combustion processes.

scholarly journals LASER SYSTEM FOR STUDYING THE DYNAMICS OF HIGH TEMPERATURE COMBUSTION

2019 ◽  
Vol 4 (2) ◽  
pp. 154-162
Author(s):  
Lin Li ◽  
Fedor Gubarev ◽  
Andrei Mostovshchikov ◽  
Alexander Ilyin
Keyword(s):  
High Temperature ◽  
Narrow Band ◽  
Laser System ◽  
Combustion Process ◽  
Visual Observation ◽  
Copper Bromide ◽  
Temperature Combustion ◽  
Temporal And Spatial ◽  
Combustion Processes ◽  
High Temperature Combustion

The paper is devoted to development of methods for studying the dynamics of high-temperature combustion of aluminum nanopowder.The difficulty in studying the combustion of nanopowders is the high temperature and intensity of light emissionduring the combustion process, which makes the visual observation virtually impossible.The paper discusses various schemes using laser radiation to study the combustion processes of metal nanopowders.Particular mentions the use of the laser monitor based on an active medium on copper bromide vapor to study the combustion process of various powders and mixtures.The laser monitor combines the functions of the narrow-band laser illuminator and the brightness amplifier, thereby achieving the visualization at a narrow gain wavelength. Therefore, the laser monitor can be used to observe the changes in the surface of a burning sample with high temporal and spatial resolution.

Thermal Characteristics of Gaseous Fuel Flames Using High Temperature Air

2004 ◽  
Vol 126 (1) ◽  
pp. 9-19 ◽  
Author(s):  
A. K. Gupta
Keyword(s):  
High Temperature ◽  
Energy Savings ◽  
Elevated Temperatures ◽  
Waste Heat ◽  
Uniform Heat Flux ◽  
Chemical Behavior ◽  
High Temperature Air Combustion ◽  
Temperature Combustion ◽  
Combustion Technology ◽  
High Temperature Combustion

Recent advances on high temperature air combustion (HiTAC) have demonstrated significant energy savings, higher and uniform thermal field, lower pollution, and smaller size of the equipment for a range of furnace applications. The HiTAC technology has evolved from the conception of excess enthalpy combustion (EEC) to high and ultra-high preheated air combustion. In the HiTAC method, combined heat regeneration and low oxygen methods are utilized to enlarge and control the flame thermal behavior. This technology has shown promise for much wider applications in various process and power industries, energy conversion, and waste to clean fuel conversion. For each application the flow, thermal, and chemical behavior of HiTAC flames must be carefully tailored to satisfy the specific needs. Qualitative and quantitative results are presented on several gas-air diffusion flames using high-temperature combustion air. A specially designed regenerative combustion test furnace facility, built by Nippon Furnace Kogyo, Japan, was used to preheat the combustion air to elevated temperatures. The flames with highly preheated combustion air were significantly more stable and homogeneous (both temporally and spatially) as compared to the flames with room-temperature combustion air. The global flame features showed the flame color to change from yellow to blue to bluish-green to green over the range of conditions examined. In some cases hybrid and purple color flame was also observed. Under certain conditions flameless or colorless oxidation of the fuel has also been demonstrated. Information on global flame features, flame spectral emission characteristics, spatial distribution of OH, CH, and C2 species and emission of pollutants has been obtained. Low levels of NOx along with negligible levels of CO and HC have been obtained using high-temperature combustion air. The thermal and chemical behavior of high-temperature air combustion flames depends on fuel property, preheat temperature, and oxygen concentration of air. Waste heat from a furnace in high-temperature air combustion technology is retrieved and introduced back into the furnace using regenerator. These features help save energy, which subsequently also reduce the emission of CO2 (greenhouse gas) to the environment. Flames with high temperature air provide significantly higher and uniform heat flux than normal air, which reduces the equipment size or increases the process material throughput for same size of the equipment. The high-temperature air combustion technology can provide significant energy savings (up to about 60%), downsizing of the equipment (about 30%), and pollution reduction (about 25%). Fuel energy savings directly translates to a reduction of CO2 and other greenhouse gases to the environment.

Temporally Resolved Two-Dimensional Spectroscopic Study on the Effect of Highly Preheated and Low Oxygen Concentration Air on Combustion

2002 ◽  
Vol 125 (1) ◽  
pp. 326-331 ◽  
Author(s):  
K. Kitagawa ◽  
N. Konishi ◽  
N. Arai ◽  
A. K. Gupta
Keyword(s):  
High Temperature ◽  
Oxygen Concentration ◽  
Spontaneous Emission ◽  
Flame Temperature ◽  
Diagnostic Technique ◽  
Temperature Profiles ◽  
Low Oxygen ◽  
Time Resolved ◽  
Visible Wavelengths ◽  
Low Oxygen Concentration

Spontaneous emission spectroscopy has been applied to measure the time-resolved temperature profiles of gaseous fuel flames using high temperature and low oxygen concentration combustion air. Two emission peaks of C2 radical species have been observed at visible wavelengths from propane-air flames. The ratio of these two peaks depends on the flame temperature. The relationship between the ratios of these peaks was correlated with the thermocouple output using a premixed flat flame burner and a multichannel CCD spectrometer. Using this relationship, the flame temperature was determined from the ratio of the C2 peaks. Time-resolved emission intensity profiles of the two C2 bands (two-wavelength image) were observed simultaneously with a high sensitivity video camera fitted with an optical system. The time-resolved temperature profiles were constructed from these intensity profiles by utilizing the previously determined relationship at each pixel. To evaluate fluctuations of flame temperatures, the standard deviation profiles for the temperature profiles have been constructed. This spectroscopic diagnostic technique has been used to measure the profiles of mean flame temperature and temperature fluctuation produced from a concentric diffusion flame using propane as the fuel and high temperature and low oxygen concentration combustion air. In this study, the effect of air-preheat and low oxygen concentration in the combustion air on the subsequent flame temperature and temperature fluctuations has been determined by analyzing the spectra of spontaneous emission from the C2 radicals.

scholarly journals An Overview of Advanced Chalcogenide Thermo- electric Materials and Their Applications

2018 ◽  
Vol 2 (2) ◽  
Author(s):  
Fiseha Tesfaye
Keyword(s):  
Power Generation ◽  
High Temperature ◽  
Energy Savings ◽  
Waste Heat ◽  
Clean Energy ◽  
Point Of View ◽  
Thermal Stabilities ◽  
Thermo Electric ◽  
Heating And Cooling ◽  
Recent Developments

Thermoelectricity is a strong scientific and technological interest due to its wide application ranging from clean energy producing to photon sensing devices. Recent developments in theoretical studies on the thermoelectric (TE) effects as well as the newly discovered thermoelectric materials provide new opportunities for several applications. Though the scale of production is limited, thermo-electric technology provides an alternative to traditional methods of power generation, heating and cooling systems. TE technologies can be used in power generation, heating and cooling applications. They potentially offer significant energy savings through waste heat recovery and augmented cooling. This article critically discusses the current progress in chalcogenide TE materials and the advantages and limitations associated with the TE technologies. The need for new materials discoveries from the point of view of achieving higher figure-of-merit combined with thermal stabilities in intermediate- and high- temperature Peltier and Seebeck effects applications is also emphasized. Besides, this article aims to evaluate the main features of recently characterized multicomponent chalcogenide ionic compounds with high thermal stabilities as potential TE materials to harvest electric power from high-temperature heat flux via thermoelectricity.

Study and Design on High Temperature Air Combustion of Hot Blast Stove

2014 ◽  
Vol 496-500 ◽  
pp. 1058-1062
Author(s):  
Fu Ming Zhang ◽  
Zu Rui Hu ◽  
Shu Sen Cheng
Keyword(s):  
High Temperature ◽  
Concentration Distribution ◽  
Cfd Simulation ◽  
Formation Rate ◽  
Flame Temperature ◽  
Combustion Process ◽  
High Temperature Air Combustion ◽  
Blast Stove ◽  
New Type ◽  
Hot Blast

During Hot Blast Stove (HBS) combustion, NOxforms rapidly when the flame temperature above 1420°C. In order to restrain the amount of NOxformation during combustion of HBS, the formation mechanism of NOxis investigated, and the NOxformation rate and amount in HBS are calculated by means of thermodynamic model. A new type of dome combustion HBS is developed based on high temperature air combustion (HTAC) technology. A comparison on the combustion process and characteristic of conventional HBS and HTAC HBS is performed by application of Computational Fluid Dynamics (CFD) simulation model. Temperature and concentration distribution, flame shape and NOxconcentration distribution of two kinds of stove are calculated. The result shows quite symmetrical HTAC stove temperature distribution. Under the same dome temperature, NOxamount is 80ppm only, reduced by approximate 76% in comparison with conventional stove.

Development and Assessment of Combustion Models for Gas Turbine and Aero-Engine Applications

2015 ◽  
Author(s):  
Jan E. Anker ◽  
Dirk Wunsch ◽  
Luigi Romagnosi ◽  
Kilian Claramunt ◽  
Charles Hirsch
Keyword(s):  
Gas Turbine ◽  
Combustion Process ◽  
Measurement Data ◽  
Point Of View ◽  
Navier Stokes ◽  
Flammability Limits ◽  
Combustion Models ◽  
Spray Flames ◽  
Aero Engine ◽  
Combustion Processes

The classical flamelet method, the new Flamelet Generated Manifolds method (FGM), and the hybrid BML/flamelet approach are assessed in the context of the Reynolds-averaged Navier-Stokes (RANS) equations on a large range of configurations for both gaseous and spray flames. The conceptual differences, advantages, and shortcomings of the models are discussed in detail both from a theoretical and a practical point of view. In order to assess the models under gas turbine like conditions, the reactive flow in TU Darmstadt’s Generic Gas Turbine (GGT), DLR Stuttgart’s PRECCINSTA burner, and a premixed industrial combustor are computed. The computational results are compared to available measurement data and are used to discuss the strengths and the weaknesses of each of the aforementioned combustion models. In the current study it is shown that the hybrid BML/flamelet method globally performs well, but that it can be difficult to obtain a burning solution with this method, especially when the combustion process is operated close to the flammability limits. While the flamelet method is very robust, it is outperformed by the FGM method even for purely non-premixed configurations. It is demonstrated that the FGM approach can be used for the whole range of combustion modes, from non-premixed over to premixed combustion processes. Since the model did not lead to any difficulties with attaining a burning solution, and is computationally as efficient as the flamelet approach, the authors recommend the usage of this model over the other models investigated.

Corrosion Behaviors of Al-Steel-Sputtering-Treated Steel and SiC/SiC Composites in High Temperature LBE at Low Oxygen Concentration

2006 ◽  
Author(s):  
Abu Khalid Rivai ◽  
Minoru Takahashi
Keyword(s):  
High Temperature ◽  
Oxygen Concentration ◽  
Low Oxygen ◽  
Base Area ◽  
Treated Steel ◽  
Corrosion Behaviors ◽  
Sic Composites ◽  
Low Oxygen Concentration ◽  
Ss 304 ◽  
Treated Layer

Corrosion tests of Al and SS-304-sputtering-surface treated STBA26 (9Cr.1Mo.0.1Si) and SiC/SiC composites with BN (boron nitide) coating has been conducted in high temperature LBE of 700°C at low oxygen concentration of 6.8 × 10−7 wt% and the behavior was analyzed. The sputtering technique was used to protect the steel from corrosion. The thickness of sputtering-treated layer was 21.45 μm. All specimens were immersed in LBE in a pot for 1000 hours. The STBA26 (9Cr.1Mo.0.1Si) without surface treated were also tested for comparison with sputtering-treated steels. The results showed that sputtering-treated layer still remained on the base of STBA26. No penetration of LBE was observed in this layer. The layer could protect the steel from penetration of LBE. The result also showed that thin layer which contains aluminum oxide and chromium oxide was formed on the surface-treated layer, and it protected the base area. On the contrary, the penetration in base area was observed in the as received STBA26. In SiC/SiC composites, there appeared cracks in a thin surface area and LBE penetrated deeply into the material. The corrosion did not occur in this SiC/SiC composite in the high temperature LBE.

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