Combustion Temperature Measurements Research Articles

An improved semi-global intrinsic kinetics model for high temperature carbon oxidation

Measurements of the oxidation rates of various forms of carbon (soot, graphite, coal char) have often shown an unexplained attenuation with increasing temperatures in the vicinity of 2000 K, even when accounting for diffusional transport limitations and gas-phase chemical effects (e.g. CO2 dissociation). With the development of oxy-fuel combustion approaches for pulverized coal utilization with carbon capture, high particle temperatures are readily achieved in sufficiently oxygen-enriched environments. In this work, a new semi-global intrinsic kinetics model for high temperature carbon oxidation is created by starting with a previously developed 5-step mechanism that was shown to reproduce all major known trends in carbon oxidation, except for its high temperature kinetic falloff, and incorporating a recently discovered surface oxide decomposition step. The predictions of this new model are benchmarked by deploying the kinetic model in a steady-state reacting particle code (SKIPPY) and comparing the simulated results against a carefully measured set of pulverized coal char combustion temperature measurements over a wide range of oxygen concentrations in N2 and CO2 environments. The results show that the inclusion of the spontaneous surface oxide decomposition reaction step significantly improves predictions at high particle temperatures. Furthermore, the simulations reveal that O atoms released from the oxide decomposition step enhance the radical pool in the near-surface region and within the particle interior itself. Incorporation of literature rates for O and OH reactions with the carbon surface results in a reduction in the predicted radical pool concentrations and a very minor enhancement of the overall carbon oxidation rate.

Combustion Efficiency in a Fluidized-Bed Combustor with a Modified Perforated Plate for Air Distribution

Combustion efficiency is one of the most important parameters especially in the fluidized-bed combustor. Investigations into the efficiency of combustion in fluidized-bed combustor fuels using solid biomass waste fuels in recent years are increasingly in demand by researchers around the world. Specifically, this study aims to calculate the combustion efficiency in the fluidized-bed combustor. Combustion efficiency is calculated based on combustion results from the modification of hollow plates in the fluidized-bed combustor. The modified hollow plate aims to control combustion so that the fuel incorporated can burn out and not saturate. The combustion experiments were tested using palm oil biomass solid waste fuels such as palm kernel shell, oil palm midrib, and empty fruit bunches. The results of the measurements showed that the maximum combustion temperature for the palm kernel shell fuel reached 863 °C for M1 and 887 °C for M2. The maximum combustion temperature measurements for M1 and M2 from the oil palm midrib fuel testing reached 898 °C and 858 °C, respectively, while the maximum combustion temperature for M1 and M2 from the empty fruit bunches fuel was 667 °C and M2 847 °C, respectively. The rate of combustion efficiency with the modification of the hole plate in the fluidized-bed combustor reached 96.2%. Thermal efficiency in fluidized-bed combustors for oil palm midrib was 72.62%, for PKS was 70.03%, and for empty fruit bunches was 52.43%. The highest heat transfer rates for the oil palm midrib fuel reached 7792.36 W/m2, palm kernel shell 7167.38 W/m2, and empty fruit bunches 5127.83 W/m2. Thus, the modification of the holed plate in the fluidized-bed combustor chamber showed better performance of the plate than without modification.

Magnetization of Biodiesel (Cooking Oil Waste) to Temperature and Pressure Combustion in Diesel Engine

Research related to the provision of magnetic field strength in the flow of fuel that can cause more complete combustion has been reported by many researchers and most of these observations were carried out by measuring machine performance using a dynamometer. Given the dynamometer prices are very expensive then another way to prove the occurrence of complete combustion is through the combustion chamber indicator. The hypothesis is the greater magnetic field passed by fuel, the more perfect the combustion is. In addition, the combustion chamber temperature also increases and thermal efficiency increases. The fuel used is biodiesel derived from cooking oil waste, biodiesel 100% (denoted as B0), a blend of biodiesel (20%)-diesel (80%) (denoted as B20), a blend of biodiesel (40%)-diesel (60%) (denoted as B40), a blend of biodiesel (30%)-diesel (30%) (denoted as B70), and diesel 100% (denoted as B100). The magnetic field used is 500 Gauss, 900 Gauss and 1500 Gauss. Measurement of combustion temperature is using R type temperature sensor, which is connected to the NI USB interface to computer and LabVIEW for data acquisition. 13 HP capacity of diesel engine was used. The results obtained is 13 % temperature increase in the combustion chamber of the engine and 7 - 12% thermal efficiency increase equipped with a magnet compared to a non-magnetic engine.

Experiments for combustion temperature measurements in a sugarcane bagasse large-scale boiler furnace

This work presents a numerical and experimental study to measure local combustion temperature from the combustion reactive zone in an industrial sugarcane. A bagasse boiler furnace is utilized preliminary step towards obtaining online three-dimensional temperature measurements. Two different methods were used for in situ measurement of local temperatures in a sugarcane bagasse flame: Spectral Analysis and Image Processing in the Visible Spectrum. The maximum instantaneous temperatures found in the focused reactive zone area of the bagasse flame were 1623 K and 1520 K by the spectrometric and imaging system respectively and the time average maximum flame temperatures measured were 1443 K and 1496 K. Additionally, a set of flame temperature measurement tests was carried out in a laboratory furnace by the spectrometric method and a time average flame temperature of 1569 K was noted. The flame temperatures found in this work show reasonable agreement with results of CFD simulations and results obtained in laboratory tests which were also reported in the literature. Intensity of emission lines of alkali metal (K) were measured in the flame spectra during the bagasse combustion. Spectral flame emissivity was estimated for an industrial level operating condition.

Model-Based Approach for Combustion Monitoring Using Real-Time Chemical Reactor Network

Flame stability and pollution control are significant problems in the design and operation of any combustion system. Real-time monitoring and analysis of these phenomena require sophisticated equipment and are often incompatible with practical applications. This work explores the feasibility of model-based combustion monitoring and real-time evaluation of proximity to lean blowout (LBO). The approach uses temperature measurements, coupled with Chemical Reactor Network (CRN) model to interpret the data in real-time. The objective is to provide a computationally fast means of interpreting measurements regarding proximity to LBO. The CRN-predicted free radical concentrations and their trends and ratios are studied in each combustion zone. Flame stability and a blowout of an atmospheric pressure laboratory combustor are investigated experimentally and via a phenomenological real-time Chemical Reactor Network (CRN). The reactor is operated on low heating value fuel stream, i.e., methane diluted with nitrogen with N2/CH4volume ratios of 2.25 and 3.0. The data show a stable flame-zone carbon monoxide (CO) level over the entire range of the fuel-air equivalence ratio (Φ), and a significant increase in hydrocarbon emissions approaching blowout. The CRN trends agree with the data: the calculated concentrations of hydroxide (OH), O-atom, and H-atom monotonically decrease with the reduction of Φ. The flame OH blowout threshold is 0.025% by volume for both fuel mixtures. The real-time CRN allows for augmentation of combustion temperature measurements with modeled free radical concentrations and monitoring of unmeasurable combustion characteristics such as pollution formation rates, combustion efficiency, and proximity to blowout. This model-based approach for process monitoring can be useful in applications where the combustion measurements are limited to temperature and optical methods, or continuous gas sampling is not practical.

Temperature measurements in combustion of counter jets in burner devices

The investigation of propane-butane counter jets combustion in burners with permeable walls was carried out. The effect of addition of silicon oxide, zircon and carbon powder on combustion regime and temperature of free counter jets was investigated. Temperature measurements were implemented using registration of jets radiation in visible spectral range by means of spectral pyrometry and spectroscopic approaches. The burner devices with permeable porous pipes were demonstrated to be promising for broadening parameters range of stable combustion and increasing energy density in fuel combustion systems.

Experimental investigation on plasma-assisted combustion characteristics of premixed propane/air mixture

A detailed study on the plasma-assisted combustion (PAC) characteristics of premixed propane/air mixture is presented. The PAC is measured electrically, as well as optically with a multichannel spectrometer. The characteristics are demonstrated by stable combustion temperature and combustion stability limits, and the results are compared with conventional combustion (CC). Stable combustion temperature measurements show that the introduction of PAC into combustion system can increase the stable combustion temperature, and the increment is more notable with an increase of discharge voltage. Besides, the rich and weak limits of combustion stability are both enlarged when plasma is applied into the combustion process and the increase of discharge voltage results in the expansion of combustion stability limits as well. The measurements of temperature head and emission spectrum illustrate that the kinetic enhancement caused by reactive species in plasma is the main enhancement pathway for current combustion system.

基于可调谐二极管激光吸收光谱波长调制技术在线测量燃烧场温度

基于可调谐二极管激光吸收光谱波长调制技术在线测量燃烧场温度

Model-Based Method for Combustion Power Stabilisation in Grate-Fired Boilers

Abstract A model-based control strategy for the compensation of combustion power fluctuations in small-scale biomass fired boilers is presented. Delay-free heat output model is obtained by utilising combustion temperature measurements. Local principal component regression models are constructed to cope with changing combustion conditions and redundant input variables found by data analysis. The modelling approach was validated using data from 30 kW and 300 kW boilers. Usability of the discussed monitoring method for compensating fuel power disturbances by the primary air control was tested in practice. The results imply that modelling information can be utilised as a part of the control structure, enabling the cost-effective way to reduce emissions and maintain optimal combustion conditions in the distributed energy production with solid biomass fuels.

Temperature measurements in combustion—not only with CARS: a look back at one aspect of the European CARS Workshop

AbstractTemperature is perhaps the most important quantity in combustion research and technology. The potential and state of the art of various laser‐based diagnostics used for the determination of temperature in laboratory flames and practical combustion devices are discussed and illustrated with a few representative examples from our laboratory. The emphasis is on coherent anti‐Stokes Raman scattering (CARS), the main topic of the European CARS Workshop in the past. As a result, CARS is today the most matured and proven technique for technical applications. In addition to CARS, however, linear laser spectroscopic methods also deliver valuable and supplementary information on temperature in combustion. Copyright © 2003 John Wiley & Sons, Ltd.

Fluidized-bed combustion synthesis of titanium nitride

A detailed experimental study of the self-propagating high-temperature synthesis of titanium nitride was conducted to improve the conversion yield and illustrate the mechanism of formation of titanium nitride. The investigation was performed at atmospheric pressure, room temperature, and normal gravity conditions in a fluidized bed of gaseous nitrogen and solid titanium particles of approximately 50 μm. This fluidized-bed combustion system successfully produced a homogeneous dispersion of titanium particles in the nitrogen stream via a dual-syringe particle injection system, and subsequent particle ignition led to the gradual propagation of a combustion wave. From the combustion reaction, a maximum conversion yield of titanium nitride was obtained of approximately 60%. The high conversion yield was ascribed to increased introgen accessibility to the precursor particle surface by increasing the interstitial distances between particles in fluidization. The composition of the product particles was analyzed both qualitatively and quantitatively by scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), and X-ray diffraction. Based on the measurement of combustion temperature and subsequent calculation of heat transfer, a liquid mechanism is indicated for the formation of titanium nitride obtained in the combustion synthesis system.

Two-Wire Thermocouple for Fluctuating Temperature Measurements in Combustion. Rational Reconstruction of Mean and Fluctuating Time Constants.

A theoretical basis for the application of a comprised of two fine thermocouples of different diameters to fluctuating temperature measurements is established with the aid of the least squares method. Based on this theory, the simultaneous in situ reconstruction of thermocouple time constants and compensated temperatures is realized without using any geometrical features of the two thermocouples such as wire diameters. Thus, introduction of a 'time-constant ratio' into the reconstruction scheme is unnecessary. Consequently, problems in two-wire thermocouple techniques proposed so far can be overcome. In addition, a simple and reliable method for correcting heat loss due to thermal radiation from the thermocouples is devised, which can be incorporated into the reconstruction scheme with little modification. The developed scheme is tested in a fluctuating temperature field with a diffusion flame formed in a two-dimensional wind tunnel, It is shown that the present technique is successful and allows us to investigate the characteristics of time-constant fluctuations in high-temperature turbulent flows.

Magnetic Field Effects on Combustion

Continuous measurement of combustion temperature and speed in a magnetic field was studied to precisely determine the nature of combustion in a field. When methanol was burned in a magnetic field, combustion speed only decreased to a low value at 0.9 T. Combustion reaction speed is inhibited at 0.9 T, and it seems that effectively the combustion temperature is reduced. Also, there is a tendency to large fluctuations of combustion temperature variation amplitude and frequency in the magnetic field.

Application of spatially precise laser diagnostics to fundamental and applied combustion research

Recent applications of spatially precise, spectroscopically based laser diagnostics for measurement of combustion temperature and species are reviewed. Four techniques are analyzed: Rayleigh scattering, spontaneous Raman scattering, laser-induced fluorescence spectroscopy (LIFS), and coherent anti-Stokes Raman spectroscopy (CARS). The impact of these techniques on both fundamental research and applied problems is considered.

Coherent anti-Stokes Raman scattering diagnostics of combustion and other reactive media at ONERA

Coherent anti-Stokes Raman scattering (CARS) is well adapted to the measurement of temperatures and concentrations of molecules in reactive gaseous media. The general principles are given along with the major technical advantages and requirements. Characteristic applications are described in order to present state-of-the-art performance levels: measurement time, spatial resolution, detection sensitivity. Results are presented of instantaneous temperature measurements in combustion and in piston engines, measurements of rotational–vibrational populations of H2 in a magnetic multicusp discharge, and measurements of the vibrational excitation of the prompt H2 formed in H2CO dissociation.

Reliability of Combustion Efficiency Evaluation for Jet Propulsion Based Upon Aerodynamic Measurement of Combustion Temperature

Aerodynamic measurement of combustion temperature relies upon measurement of the total-to-static pressure ratio across the combustor exhaust nozzle, and simul­ taneous measurement of the weight flow. Combustion efficiency computed from this temperature expresses jet propulsion performance characteristics of the combustor, subject to both systematic and random errors. The sources and magnitudes of these errors are examined, as a key to estimation of reliability of combustion efficiency values. Care must be taken to avoid certain potential systematic errors, but in most instances corrections can be made which themselves do not introduce appreciable ran­ dom errors. With such care and with reasonably refined instrumentation, the major source of random error is the evaluation of nozzle exit Mach number. The resulting probable error in combustion efficiency, expressed as either a temperature rise ratio or a ratio of fuel/air ratios to com­ pare theoretical and actual performance, is in the neigh­ borhood of ±5 per cent. When development of thrust for jet propulsion is the point of interest, this is reasonable reliability, considerably less doubtful than offhand esti­ mates which are often made to provide conservative views.

A Modified Sodium-Line Reversal Technique for the Measurement of Combustion Temperatures in Rocket Engines

The application of a modified sodium-line reversal technique to the measurement of combustion temperature at several stations within an open tube rocket combustor was investigated. The measurement technique, experimental apparatus, and results are described and discussed. The effect of oxidant-fuel ratio on axial temperature distribution for a single two-on-one impingement type injector utilizing liquid oxygen and alcohol as propellants was evaluated. The experimental results indicate tha t the technique may be successfully applied to the study of combustion reaction t ime in rocket engines.