Estimation Of Gas Temperature Research Articles

Measurements and Prediction of Ash Deposition in a Cyclone-Fired Boiler Operating under Variable Load Conditions

Measurements of ash deposition rates were made between the secondary superheater and reheater sections of a 450 MW cyclone-fired lignite boiler as the operational load varied from 33 to 100%. Significant reductions in deposition rates with a decrease in operational load were observed. To uncover the causative mechanisms behind these observations, operational data from the power plant were used to carry out computational fluid dynamic (CFD) simulations of the boiler. After ascertaining that the gas temperatures and velocities at various sections within the boiler were being represented adequately, decoupled simulations of the ash deposition process on the deposit probe were carried out using a finely resolved boundary layer mesh. Fly ash particle size distribution (PSD) and its concentration for the decoupled calculations were determined from stand-alone cyclone barrel simulations. The ash partitioning (mass %) between the fly ash and slag was found to be ~50:50, which was in line with previous field observations, and it did not vary significantly across different cyclone loads. The predicted PSD of the deposit ash was concentrated in the size range 10–30 microns, which was in agreement with cross-sectional images of the deposit obtained from the measurements. At lower loads, sharp variations in the deposition rates were predicted in the gas temperature range 950–1150 K. The particle kinetic energy—particle viscosity-based capture methodology utilized in this study in conjunction with appropriate ash compositions, ash viscosity models and gas temperature estimates can help estimate slagging propensities at different loads reasonably well in these systems.

A step parameters prediction model based on transfer process neural network for exhaust gas temperature estimation after washing aero-engines

The prediction of Exhaust Gas Temperature Margin (EGTM) after washing aero-engines can provide a theoretical basis for airlines not only to evaluate the energy-saving effect and emission reduction, but also to formulate reasonable maintenance plans. However, the EGTM encounters step changes after washing aeroengines, while, in the traditional models, a persistence tendency exists between the prediction results and the previous data, resulting in low accuracy in prediction. In order to solve the problem, this paper develops a step parameters prediction model based on Transfer Process Neural Networks (TPNN). Especially, “step parameters” represent the parameters that can reflect EGTM step changes. They are analyzed in this study, and thus the model concentrates on the prediction of step changes rather than the extension of data trends. Transfer learning is used to handle the problem that few cleaning records result in few step changes for model learning. In comparison with Long Short-Term Memory (LSTM) and Kernel Extreme Learning Machine (KELM) models, the effectiveness of the proposed method is verified on CFM56-5B engine data.

A simplified mathematical model for estimating gas temperature and velocity under natural smoke exhaust in sloping city tunnel fires

In the previous study, the prediction of gas temperature and velocity in the naturally-ventilated inclined tunnels under traffic blockage has been well concerned (Y. Zhou et al., Sustain. Cities Soc. 45, 2019, 258–270). In this paper, we continue to pay attention to the estimation of internal gas temperature and velocity under natural smoke extraction in both single-slope and gable-slope tunnel fires, a more hazardous scenario. A series of simplified mathematical models based on the equations of continuity, energy and pressure balance was proposed to estimate the gas temperature and velocity in sloping tunnel fires, in which the influences of fire source location, tunnel slope and tunnel geometry were taken into account. In addition, corresponding numerical simulations based on full-size tilted urban tunnel fires were performed using Computational Fluid Dynamics (CFD) method. The results show that the variation trends between CFD and analytical results are basically the same, and the iterative values of gas temperature and velocity coincide well with the simulations. A fast and convenient method for the estimation of gas temperature and velocity in sloping tunnel fires has been proposed, and the results of this work can provide a reference for the optimal design and management of natural smoke extraction systems, and help to ensure the fire safety of single-slope and gable-slope city tunnels.

Cylinder Pressure-based Virtual Sensor for Gas State Estimation During Compression Stroke

Abstract The gas state during the compression stroke can vary depending on the operating conditions and cycle-to-cycle variations. In this research, determination of polytropic exponent, trapped mass, and gas temperature are addressed. A golden section search method is applied to cyclic polytropic exponent estimation, and then a statistical filter is employed for cyclic estimation to filter out the estimation noise. A novel iterative-∆p-method is finally presented for the determination of the trapped mass and gas temperature simultaneously during the compression stroke. A sequence of trapped mass estimates and a sequence of gas temperature estimates can be obtained along crank angle position. Experimental validations carried out on a gasoline engine demonstrate the effectiveness of the presented methods.

Cylinder state estimation from measured cylinder pressure traces - A Survey

In the search for improved performance and control of combustion engines there is a search for the sensors that gives information about the combustion profile and the state of the gases in the combustion chamber. A particular interest has been given to the potential use of the cylinder pressure sensor and there is quite a lot of work that has been made in this area. This paper provides a comprehensive list of references and summarizes applications and methods for extracting information from the cylinder pressure sensor about the combustion and the gas state. The summary highlights the following topics related to cylinder pressure: measurement chain, cylinder torque, extraction of the burn profile, combustion placement, knocking, cylinder air mass, air to fuel ratio, residual gas estimation, and cylinder gas temperature estimation. The focus in the summary is on the latter topics about the gas state but thermodynamic analysis of the combustion process also gets a longer treatment since many methods for information extraction rely on the thermodynamic properties.

Neutral gas temperature estimates and metastable resonance energy transfer for argon-nitrogen discharges

Rovibrational spectroscopy band fitting of the nitrogen (N2) second positive system is a technique used to estimate the neutral gas temperature of N2 discharges, or atomic discharges with trace amounts of a N2 added. For mixtures involving argon and N2, resonant energy transfer between argon metastable atoms (Ar*) and N2 molecules may affect gas temperature estimates made using the second positive system. The effect of Ar* resonance energy transfer is investigated here by analyzing neutral gas temperatures of argon-N2 mixtures, for N2 percentages from 1% to 100%. Neutral gas temperature estimates are higher than expected for mixtures involving greater than 5% N2 addition, but are reasonable for argon with less than 5% N2 addition when compared with an analytic model for ion-neutral charge exchange collisional heating. Additional spatiotemporal investigations into neutral gas temperature estimates with 10% N2 addition demonstrate that although absolute temperature values may be affected by Ar* resonant energy transfer, spatiotemporal trends may still be used to accurately diagnose the discharge.

Resonance broadening of argon lines in a micro-scaled atmospheric pressure plasma jet (argon μAPPJ)

Optical emission from atmospheric pressure micro-jet operating with pure argon (argon μAPPJ) flow has been detected with a moderate resolution spectrometer. Large broadening of the several argon (Ar) lines has been observed in the near infrared spectral region. This effect was attributed to resonance broadening of the s2 (Paschen notation) level in 3p54s configuration. In the present work, corresponding line profiles are suggested for plasma diagnostics. For this, a general case of resonance broadening coefficient of noble gases is discussed. As broadening reflects the Ar density, and the static gas pressure of the jet is in equilibrium with the ambient, the local gas temperature can be inferred. An estimation of gas temperature from the width of the 750 nm Ar line is in agreement with rotational temperature of OH radicals determined from the A2Σ+ → X2Π (0, 0) band. At low temperatures (300–600 K) and at partial Ar pressure near atmospheric, the resonance width of the suggested lines is very sensitive to small temperature variations. High temperature sensitivity and large width make the resonance broadened lines very attractive for diagnostics of low temperature discharges at elevated pressure, e.g., as they are used in plasma-medicine.

Evaluating the temperature inside a tank during a filling with highly-pressurized gas

Gas storage of hydrogen in composite pressure vessels at high pressure is attractive for weight reasons. On the other hand, filling in a short time has to be properly controlled to insure safety. Indeed, compression effects during the H2 fast filling of a cylinder induce a temperature rise inside the gas whose level depends on filling rate, thermal properties of the walls and also geometric characteristics of the cylinder. The effect of each parameter must be well understood to optimize filling quality while maintaining safety. This study presents experimental results obtained on a type IV 90.5 L tank for different filling conditions. Temperatures of the gas have been monitored during filling using temperature sensors. A soft sensor (0D model) has been developed for real time gas temperature estimation during filling. Comparisons between numerical simulations derived from this soft sensor and experimental results are discussed in order to prove the validity of the model and provide a deeper understanding of thermal phenomena in the cylinder.

Development of a Virtual Sensor for Estimation of Gas Temperature in a Diesel Engine Exhaust Manifold

Development of a Virtual Sensor for Estimation of Gas Temperature in a Diesel Engine Exhaust Manifold

Diode laser spectroscopic measurements of gas temperature in a pulsed dielectric barrier discharge using collisional broadening and shift of 1s3−2p2and 1s5−2p7argon transitions

The average gas temperature rise within an argon dielectric barrier discharge operating from 50 to 500 Torr excited by 5 kHz repetition rate fast rise time high voltage pulse has been measured. For these measurements within high pressure discharges, we have employed two novel gas temperature measurement techniques based upon tunable diode laser absorption spectroscopy that take advantage of the nonresonant collision line broadening and collisional frequency shifts from relatively strong argon 1s3-2p2 and 1s5-2p7 transitions from the metastable states. An in situ estimate of collisional broadening coefficients for both transitions have been obtained from 5 to 30 Torr data using an independent estimate of gas temperature from Doppler line width measurements. Our measurements show that the effect of the isolated line assumption inherent within the van der Waals collisional impact approximation limit begins to fail for the 1s3-2p2 and 1s5-2p7 spectral lines when collisional line broadening exceeds ∼23 GHz line separation at gas pressure >300 Torr with gas temperature near ambient. A comparison of gas temperature estimates from both line broadening and peak frequency shift shows that the frequency shift provides a more reliable measurement of gas temperature, indicating that the isolated line assumption holds for collisional peak frequency shifts, even for partially overlapping lines.

Determination of gas temperature of high-frequency low-temperature electrodeless plasma using molecular spectra of hydrogen and hydroxyl-radical

In this study we determine gas temperature of He+H2, Ar+H2 and Ne+H2 high frequency electrodeless lamps using intensity distribution in rotational spectra of hydrogen molecule and hydroxyl radical. The measurement results show that OH rotational spectra can be successfully used for estimation of gas temperature of the high-frequency electrodeless lamps at very small amounts of hydrogen present in plasma. The analysis of the measurement results leads to the conclusion that in “pure” plasma the applied energy is used to heat plasma, while for the plasma with hydrogen addition the energy is used in chemical reactions.

Reliability of NH3as the temperature probe of cold cloud cores

The temperature is a central parameter affecting the chemical and physical properties of dense cores of interstellar clouds and their evolution to star formation. The chemistry and the dust properties are temperature dependent and the interpretation of observation requires the knowledge of the temperature and its variations. Measurement of the gas kinetic temperature is possible with molecular line spectroscopy, the ammonia molecule, NH3, being the most commonly used tracer. We want to determine the accuracy of the temperature estimates derived from ammonia spectra. The normal interpretation of NH3 observations assumes that all the hyperfine line components are tracing the same gas volume. In the case of temperature gradients they may be sensitive to different layers and cause errors in the optical depth and gas temperature estimates. We examine a series of spherical cloud models, 1.0 and 0.5 M_Sun Bonnor-Ebert spheres, with different radial temperature profiles. We calculate synthetic NH3 spectra and compare the derived column densities and temperatures to the true values. For high signal-to-noise observations, the estimated gas kinetic temperatures are within ~0.3 K of the real mass averaged temperature and the column densities are correct to within ~10%. When the S/N ratio of the (2,2) spectrum decreases below 10, the temperature errors are of the order of 1K but without a significant bias. When the density of the models is increased by a factor of a few, the results begin to show significant bias because of the saturation of the (1,1) main group. The ammonia spectra are found to be a reliable tracer of the mass averaged gas temperature. Because the radial temperature profiles of the cores are not well constrained, the central temperature could still differ from this value. If the cores are optically very thick, there are no guarantees of the accuracy.

Rotational temperatures of N2(C,0) and OH(A,0) as gas temperature estimates in the middle pressure Ar/O2 discharge

Radiative transitions N2(C–B,0–0) and OH(A–X,0–0) were used in order to estimate rotational temperatures of N2(C,0) and OH(A,0) in the middle pressure Ar/0.5% O2 RF discharge. N2(C,0) and OH(A,0) rotational temperature dependence on power density was determined and quenching/rotational relaxation frequencies of N2(C,0) and OH(A,0) were calculated. It was found that under our conditions rotational temperature of OH(A,0) can be used for estimation of gas temperature while N2(C,0) rotational temperature overestimates the gas temperature.

Energy and water balances using kinetic modeling in a pilot-scale SSF bioreactor

Direct monitoring of bed conditions in large scale solid-state fermentation (SSF) bioreactors is difficult due to lack of reliable and affordable instrumentation. Although, relevant variables such as average bed temperature and water content can be inferred from energy and water balances, these estimations are prone to significant error since the process is complex and measured variables are extremely noisy. Hence, to obtain better estimation of bed conditions, simple and robust models, and effective noise suppression methods should be developed. A kinetic model was applied to obtain noise free CO 2 production rate ( CPR) values, which in turn was used in water and energy balances. The evolution of other relevant variables including total and active biomass, O 2 consumption rate, secondary metabolite production and dry mass degradation were also calculated. The proposed model was calibrated with data obtained in an agitated aseptic SSF pilot-scale bioreactor of 200 kg, growing Gibberella fujikuroi on wheat bran and starch. The calibration was achieved by means of a non-linear optimization routine. With this model better average bed temperature estimates, compared with a model that uses noisy ( CPR) measurements, were attained. Hence, the proposed model can be used on-line to estimate more reliable average bed conditions and to develop model based control strategies. In addition, a predictive model for bioreactor design can be derived from the proposed model, after good outlet gas temperature estimation has been achieved.

Neutral gas temperature estimates in an inductively coupled CF4 plasma by fitting diatomic emission spectra

In this work we examine the accuracy of plasma neutral temperature estimates by fitting the rotational band envelope of different diatomic species in emission. Experiments are performed in an inductively coupled CF4 plasma generated in a Gaseous Electronics Conference reference cell. Visible and ultraviolet emission spectra are collected at a power of 300 W (∼0.7 W/cm3) and pressure of 30 mTorr. The emission bands of several molecules (CF, CN, C2, CO, and SiF) are fit simultaneously for rotational and vibrational temperatures and compared. Four different rotational temperatures are obtained: 1250 K for CF and CN, 1600 K for CO, 1800 K for C2, and 2300 K for SiF. The vibrational temperatures obtained vary from 1750 to 5950 K, with the higher vibrational temperatures generally corresponding to the lower rotational temperatures. These results suggest that the different species have achieved different degrees of equilibration between rotational and vibrational modes and may not be equilibrated with the translational temperatures. The different temperatures also appear to relate to the expected spacial distribution of the molecules, with species expected to form near the electrode (C2, CO, SiF) having higher temperatures than species formed in the bulk.

A wind in the Galaxy

The presence of a wind in the galactic bulge is investigated as the cause of the observed minimum of neutral gas density from 0.5 to 4 kpc. Estimates of gas temperature in the bulge are shown to predict the existence of an outward flow of gas throughout a large portion of the bulge, given current estimates of supernova heating rates and stellar mass-loss rates. A hydrodynamic model of a bulge wind consisting of gas recently shed from evolving stars is then used to investigate the interaction of disk and bulge gas, and it is found that the presence of a disk of gas at any temperature and density does not stop the flow of a wind from the bulge. Cold molecular clouds in the bulge region are argued to be dynamically isolated from the wind; however, if they interact thermally through electron conduction, the wind will be limited to outside of a critical radius from 0.3 to 1 kpc. Calculations of the mass of the molecular gas accumulated within this radius over the Hubble time are found to be in agreement with the observed amount. It is pointed out that although the proposed wind prevents new gas from accumulating in the bulge, mechanisms for the depletion of the original gas from the area and the future evolution of the wind remain unclear.

On the gas temperature in coaxial electric-discharge CO2 flow lasers

An analytic and experimental investigation on the dependence of gas temperature on flow and discharge characteristics is presented. The entire range of slow- to fast-flowing coaxial CO2 electric lasers is considered. As is known, at low flow rates the gas temperature is proportional to the electric power input per unit length, while at high flow rates the gas end temperature is proportional to the ratio of total electric power and gas mass flow rate. In addition, gas pressure and entrance Mach number were found to have a noticeable effect on gas temperature; the temperature tends to increase with increasing pressure and to decrease with increasing Mach number. The agreement between theory and experiment is fairly good, so that estimates of gas temperature at given flow and discharge conditions can be obtained. Also presented is an experimental correlation between laser power output (or efficiency) and gas temperature. Finally, scaling laws for temperature-limited coaxial flow CO2 electric lasers are proposed.

Flow Visualization in a Rotating-Arc Plasma Jet

AbstractKnowledge of the gas flow pattern in a plasma jet exhaust is important in relation to heat transfer and gas temperature estimation. The extreme conditions within the jet, however, have hitherto encouraged the use of water cooled probes for flow measurements to the exclusion of quicker and more convenient optical methods.An optical system has been developed to indicate gas velocities throughout the volume of a transparent water jacket enclosing the exhaust gas by means of particle track photography. The difficulties caused by the size of the test space and the high gas luminosity are overcome by using a bi-focal lens system to utilize a photographic flash bulb source efficiently.