Three-dimensional Temperature Distribution Research Articles

Analytical solution of three-dimensional temperature field for skin tissue considering blood perfusion rates under laser irradiation and thermal damage analysis

An analytical solution of the three-dimensional transient temperature distribution for skin tissue when heated by a laser heat source is presented in this work. An equation for the three-dimensional bioheat transfer of skin tissue is obtained firstly, and the transient temperature value at any point inside the skin tissue can be solved using the separation variable method and the Newton-Cotes method. Previous research primarily focused on semi-infinite domains, while this work presents an analytical solution for finite domains. A comparison of present analytical solution with simulation software results and numerical solution is given to demonstrate the feasibility of the analytical solution. The three-dimensional temperature distribution of skin tissue irradiated by a laser is theoretically studied. The extent of thermal damage to skin tissue is assessed by substituting the analytical solution of the temperature field for laser-irradiated skin tissue into the thermal damage equation. The calculations in this work reveal that the variation of temperature field in biological tissues is dependent not only on the laser incident light intensity and the optical parameters of the tissues but also on the heat transfer properties of the biological tissues, such as the blood perfusion rates.

Theoretical models for predicting ventilation performance of vertical solar chimneys in tunnels

Solar chimney as a reliable renewable energy system has been primarily utilized for building ventilation, but its application in the tunnel is rarely explored. This study develops theoretical models to predict the ventilation performance of vertical solar chimney in urban tunnel. Five temperature distribution types within the chimney cavity are analyzed, including uniform, vertically linear, horizontally semi-parabolic, two piecewise semi-parabolic in the depth direction, and three-dimensional parabolic profiles. The theoretical models consider the effect of chimney configuration, tunnel geometry, glazing materials, and solar radiation intensity on airflow rate through solar chimney. Validation against experimental data and numerical simulation shows that considering three-dimensional temperature distributions results in an average 11 % deviation from validation data, outperforming assumptions of uniform (29.3 % deviation) or lower-dimensional profiles. The volumetric flow rate through solar chimney exponentially decreased with h/w and h/d that the optimum ratio of h/d is 10. The airflow rate linearly increased with 0.14 power of glazing absorptivity. This analysis provides technical guidance for optimizing solar chimney design in tunnels, enhancing natural ventilation, and reducing energy consumption for mechanical ventilation systems.

Study of thermal properties and stresses in a 1.05 MW molten salt furnace for recovering and storing blast furnace gas waste heat

Utilizing a molten salt furnace to recover waste heat from blast furnace gas and storing it in high-temperature molten salt represents an innovative solution for steel waste heat recovery systems. In this study, a 1.05 MW spiral coil vertical molten salt furnace thermal energy storage system was constructed. During the thermal storage experiment under a 75 % heating load, the system achieved a heating efficiency of 74.57 % and a molten salt temperature of 560.3 °C. To analyze the thermal performance and thermal stress of the molten salt furnace, a three-dimensional transient numerical computational model using ANSYS Fluent and Matlab software was developed. A two-dimensional thermoelastic model was employed to assess the thermal stress of the spiral coil. The deviations between the experiment and simulation for the molten salt outlet and coil temperature were 1.40 % and 1.66 %, respectively. Furthermore, the three-dimensional temperature and thermal stress distributions under the benchmark case were simulated, finding that the maximum coil temperature reached 574.20 °C, while the maximum coil stress was 446.30 MPa. Increasing the heating load, molten salt inlet temperature, and time all lead to increased equivalent thermal stress. However, the location of the coil radius at 16 mm showed a minor sensitivity to heat flow density. Additionally, increasing the molten salt inlet mass flow rate by 0.1 kg/s resulted in a 2.99 MPa reduction in equivalent thermal stress. This paper provided valuable insights into the thermal properties and evolution of thermal stresses during the heating process in molten salt furnaces, offering a promising approach for recycling blast furnace gas in steel plants.

Preflight and Postflight Thermal/Structural Analysis of BOLT II: The Holden Mission

BOLT-2: The Holden Mission, a follow-on to the BOLT experiment, was designed to measure the characteristics of turbulent flow in the hypersonic flight regime. This paper summarizes preflight transient thermal and structural analyses for the predicted flight trajectories that led to the selection of suitable materials for the flight experiment. Following the successful flight in March 2022, the preflight analysis methods, along with temperature measurements from the flight, were used to conduct a postflight thermal analysis based on the as-flown trajectory that attempted to match the flight data. Conservatism in the preflight design analysis was compared to the flight measurements. Databases of computed laminar and turbulent heating were generated as part of this effort that can aid in future analysis of the experimental data. The effects of modeling transitional heating during ascent were quantified when compared to a fully turbulent heating assumption. A set of estimated three-dimensional surface temperature distributions have been computed and were found to be a good match to the available flight data. Postflight structural modeling was used to estimate the differential thermal expansion at the nosetip/frustum joint interface.

The Mantis Network

Context. Using emission lines from metals, we investigate the three-dimensional distribution of temperature and chemistry in ultra-hot Jupiters. Aims. Existing observations of WASP-121 b have suggested an underabundance of titanium and titanium oxide in its terminator region. In this study, we aim to determine whether this depletion is global by investigating the dayside emission spectrum. Methods. We analyzed eight epochs of high-resolution spectra obtained with the ESPRESSO spectrograph, targeting orbital phases when the dayside is in view. We used a cross-correlation method to search for various atoms, TiO, and VO, and compare the results to models. We constrained the velocities and phase function of the emission signal using a Bayesian framework. Results. We report significant detections of Ca I, V I, Cr I, Mn I, Fe I, Co I, and Ni I, but not Ti or TiO. Models containing titanium are unable to reproduce the data. The detected signals are consistent with the known orbital and systemic velocities and with peak emission originating from the substellar point. Conclusions. We find that titanium is depleted from regions of the atmosphere where transmission and emission spectroscopy are sensitive. Supported by recent HST observations of the nightside, we interpret this as evidence for the nightside condensation of titanium, which prevents it from being mixed back into the upper layers of the atmosphere elsewhere on the planet. Species with lower condensation temperatures are unaffected, implying that sharp chemical transitions exist between ultra-hot Jupiters that have slight differences in temperature or dynamical properties. As TiO can act as a strong source of stratospheric heating, cold-trapping creates a coupling between the thermal structures on the dayside and nightside, and thus condensation chemistry needs to be included in global circulation models. Observed elemental abundances in hot Jupiters will not reliably be representative of bulk abundances unless nightside condensation is robustly accounted for or the planet is hot enough to avoid nightside cold traps entirely. Secondary eclipse observations by JWST/NIRISS have the potential to confirm an absence of TiO bands at red-optical wavelengths. We also find that the abundance ratios of metal oxides to their atomic metals (e.g., TiO/Ti) depend strongly on the atmospheric C/O ratio, and that planetary rotation may significantly lower the apparent orbital velocity of the emission signal.

Numerical study on the three-dimensional temperature distribution according to laser conditions in photothermal therapy of peri-implantitis

PurposeDental implants have been successfully implemented as a treatment for tooth loss. However, peri-implantitis, an inflammatory reaction owing to microbial deposition around the implant, can lead to implant failure. So, it is necessary to treat peri-implantitis. Therefore, this numerical study is aimed at investigating conditions for treating peri-implantitis.MethodsPhotothermal therapy, a laser treatment method, utilizes photothermal effect, in which light is converted to heat. This technique has advantage of selectively curing inflamed tissues by increasing their temperature. Accordingly, herein, photothermal effect on peri-implantitis is studied through numerical analysis with using Arrhenius damage integral and Arrhenius thermal damage ratio.ResultsThrough numerical analysis on peri-implantitis treatment, we explored temperature changes under varied laser settings (laser power, radius, irradiation time). We obtained the temperature distribution on interface of artificial tooth root and inflammation and determined whether temperature exceeds or does not exceed 47℃ to know which laser power affects alveolar bone indirectly. We defined the Arrhenius thermal damage ratio as a variable and determined that the maximum laser power that does not exceed 47℃ at the AA’ line is 1.0 W. Additionally, we found that the value of the Arrhenius thermal damage ratio is 0.26 for a laser irradiation time of 100 s and 0.50 for 500 s.ConclusionThe result of this numerical study indicates that the Arrhenius thermal damage ratio can be used as a standard for determining the treatment conditions to help assisted laser treatment for peri-implantitis in each numerical analysis scenario.

Combined flow, temperature and soot investigation in oxy-fuel biomass combustion under varying oxygen concentrations using laser-optical diagnostics

In pulverized oxy-fuel biomass combustion, intricate interaction of complex fluid-mechanical, particle-dynamical, and chemical processes manifests even at intermediate scales. This study performs a comprehensive analysis aimed to understand the processes of flame stabilization, pollutant formation, and combustion behavior of biomass particles, while evaluating the impact of varying oxygen concentration on combustion. The investigation is conducted with a comprehensive data set, encompassing various oxy-fuel operation conditions ranging from 27vol.% to 36vol.% in O2 concentration, along a comparable air flame. These conditions are realized in an optically accessible gas-assisted solid fuel combustor designed to generate flames up to 70kWth. Advanced laser-optical diagnostics are employed to capture the combustion process. These techniques include the use of two-phase PIV/PTV for simultaneous measurements of flow and particle velocities, the application of tomographic absorption spectroscopy to elucidate three-dimensional gas temperature distributions, and the establishment of a quasi-simultaneous LII and LIF experimental setup to capture both PAH and soot occurrences. Additionally, chemiluminescence imaging of CH∗ is incorporated. The analysis extends to both single-phase and two-phase combustion, revealing a pronounced influence of oxygen concentration on both regimes. The inner recirculation zone, characteristic of a swirl flame, decreases with increasing oxygen content, coupled with an acceleration of the main flow downwards due to heightened heat release proximate to the nozzle. In two-phase combustion, a significant combustion delay is observed compared to single-phase combustion. Furthermore, the occurrences of PAHs and soot are clearly separated, and a pronounced influence of local gas composition on soot formation is evident. Comparative examination between oxy-fuel and air combustion show that an oxy-fuel condition with an oxygen concentration just below 33vol.% closely mirrors the flame characteristics of air combustion.

Effect of geometric parameters of electrodes on skin heating for the design of non-ablative radiofrequency device.

Non-ablative radiofrequency (RF) has been widely used in clinical and at-home cosmetics devices. RF electrode geometry can influence the heat distribution in the tissue. This study analyzes the influence of geometric parameters of the electrode on the heat distribution in the layered tissue. The finite element simulation of the electrothermal coupling field was performed to obtain the three-dimensional (3D) temperature distribution of the four-layer tissue. The electrode geometric parameters including the inter-electrode spacing (5-12mm), width (1-3mm), length (3-10mm), shapes (bar, dot and circle), and the coupling gel's electrical conductivity (0.2-1.5 S/m) were simulated. The maximum temperature at 2mm depth (T-2mm ) and the temperature difference (Tdiff ) between the maximum skin surface temperature and T-2mm were obtained to evaluate the effectiveness and safety. The effect of geometric parameters on the effectiveness and safety was mixed. The maximum T-2mm occurred with the 5mm inter-electrode spacing, 3mm width, 10mm length, the circle-shaped electrode, and the 1.5 S/m coupling gel's electrical conductivity. The ratio of inter-electrode spacing to width at around four can achieve rapid temperature rise and skin surface temperature protection. The electrode shape influenced the area of temperature rise in the tissue's cross-section. The coupling gel's electrical conductivity should be close to that of the skin to avoid energy accumulation on the skin surface. The electrode's geometric parameters affect the effectiveness and safety of the RF product. This study has provided the simulation procedure for the electrode design.

3D Thermal Study of Double Partition Brick Drying

In porous media, heat and mass transfer is a classical model of transport and it is one of the most energy-intensive industrial processes with a wide variety of applications. This present paper is developed in order to explain the coupled heat and mass transfer that arise during drying process. A free mesh generator Gmsh is used and a 3-D unstructured Control Volume Finite Element Method (CVFEM) is employed to simulate the transport phenomena with a convective drying. Several simulation results, that depict the transport phenomenon inside a porous brick are presented and analyzed. Indeed, thanks to this numerical model, we can observe the three-dimensional distribution of temperature, liquid saturation and pressure during double partition brick drying.

Quantitative 3D Temperature Rendering of Deep Tumors by a NIR-II Reversibly Responsive W-VO2@PEG Photoacoustic Nanothermometer to Promote Precise Cancer Photothermal Therapy.

Accurately monitoring the three-dimensional (3D) temperature distribution of the tumor area in situ is a critical task that remains challenging in precision cancer photothermal (PT) therapy. Here, by ingeniously constructing a polyethylene glycol-coated tungsten-doped vanadium dioxide (W-VO2@PEG) photoacoustic (PA) nanothermometer (NThem) that linearly and reversibly responds to the thermal field near the human-body-temperature range, the authors propose a method to realize quantitative 3D temperature rendering of deep tumors to promote precise cancer PT therapy. The prepared NThems exhibit a mild phase transition from the monoclinic phase to the rutile phase when their temperature grows from 35 to 45 °C, with the optical absorption sharply increased ∼2-fold at 1064 nm in an approximately linear manner in the near-infrared-II (NIR-II) region, enabling W-VO2@PEG to be used as NThems for quantitative temperature monitoring of deep tumors with basepoint calibration, as well as diagnostic agents for PT therapy. Experimental results showed that the temperature measurement accuracy of the proposed method can reach 0.3 °C, with imaging depths up to 2 and 0.65 cm in tissue-mimicking phantoms and mouse tumor tissue, respectively. In addition, it was verified through PT therapy experiments in mice that the proposed method can achieve extremely high PT therapy efficiency by monitoring the temperature of the target area during PT therapy. This work provides a potential demonstration promoting precise cancer PT therapy through quantitative 3D temperature rendering of deep tumors by PA NThems with higher security and higher efficacy.

A new protocol for radio frequency heating of low-moisture, viscous sauces and its temperature uniformity optimisation

AbstractRadio frequency (RF) heating of agri-food, especially low moisture viscous sauces (LMVS), have obvious advantages. However, uneven heating is one main problem of RF heating technology that has to be solved. Due to the unclear heating mechanism and the difficulty to measure the three-dimensional temperature distribution in the heated object, computer-aided analysis method was adopted. Based on the RF heating numerical calculation model after experimental verification and the characteristics of polyetherimide (PEI) assisted RF heating of peanut butter (PB), this study proposed an improved method for an existing protocol. Meanwhile, parameters of the new protocol were optimised by the Multi-objective Global Optimisation (MGO) of its surrogate model. Results demonstrated that the best size of PEI block in the new protocol was Φ100 × 9.5 mm and the positional height was 12 mm. When the pasteurisation temperature Tp was set to 70 °C and the control temperature Tc was set to 75 °C, the temperature uniformity evaluation indices, Over-shoot Temperature Control Index (OTCI) and Targeted Penetration Depth (TPD), were 0.920% and 3.975 mm, respectively. Compared with 4.845% and 4.940 mm before improvement, the new protocol achieved significant optimisation and improved the temperature uniformity effectively. This also proved the feasibility of MGO method of surrogate model in relevant studies.

Three-dimensional irradiance and temperature distributions resulting from transdermal application of laser light to human knee-A numerical approach.

The use of light for therapeutic applications requires light-absorption by cellular chromophores at the target tissues and the subsequent photobiomodulation (PBM) of cellular biochemical processes. For transdermal deep tissue light therapy (tDTLT) to be clinically effective, a sufficiently large number of photons must reach and be absorbed at the targeted deep tissue sites. Thus, delivering safe and effective tDTLT requires understanding the physics of light propagation in tissue. This study simulates laser light propagation in an anatomically accurate human knee model to assess the light transmittance and light absorption-driven thermal changes for eight commonly used laser therapy wavelengths (600-1200 nm) at multiple skin-applied irradiances (W cm-2 ) with continuous wave (CW) exposures. It shows that of the simulated parameters, 2.38 W cm-2 (30 W, 20 mm beam radius) of 1064 nm light generated the least tissue heating -4°C at skin surface, after 30 s of CW irradiation, and the highest overall transmission-approximately 3%, to the innermost muscle tissue.

Simultaneously retrieving of soot temperature and volume fraction in participating media and laminar diffusion flame using multi-spectral light field imaging

The inner distribution of the flame properties can be retrieved by solving the intractably ill-posed inverse problem from spectral radiation imaging. This study presents a simultaneous retrieving method of the three-dimensional temperature and soot volume fraction distribution in the small-scaled flame by proposing a multi-spectral light field imaging process. The results show that the temperature and soot volume fraction of the participating media and laminar diffusion flame can be reliably retrieved. Specifically, the reconstructed properties of the inner region of lower flame height are moderately affected by the selection of the visible wavelength group. The ray number slightly affects the retrieve, while the deviation is susceptible to measurement error, which is better to be less than 52 dB. The proposed approach can be used for the flame spectral diagnostic and the radiative properties calculation.

Coestimation of SOC and Three-Dimensional SOT for Lithium-Ion Batteries Based on Distributed Spatial–Temporal Online Correction

Energy storage system based on batteries is a key to achieve green industrial economy and the online estimation of its status is critical for the battery management system. Therefore, this paper proposed a distributed spatial-temporal online correction algorithm for state of charge (SOC) -three-dimensional state of temperature (SOT) co-estimation of battery. Firstly, the internal resistance is identified, and state of charge SOC are estimated based on the adaptive Kalman filter. Then, to improve the fidelity of electrical status estimation under the dynamic operation condition, the SOC estimation is coupled with an online restoration algorithm of distributed temperature. An improved fractal growth process is used to achieve the self-organization and convergence during the restoration of three-dimensional temperature distribution. Finally, to validate the fidelity of online co-estimation algorithm for electrical and thermal parameters, dynamic current profiles are used. The co-estimation method raises the fidelity of SOC estimation by 1.5% at most, compared with the SOC estimation algorithm without the SOT estimation. It also keeps the mean relative error of SOT estimation within 8%. Additionally, the robustness of the spatial-temporal online correction method with dual adaptive Kalman filters is validated. The result shows that the co-estimation algorithm still has a good converge performance with disturbance added.

Three-dimensional temperature distribution of aircraft tyre tread at touchdown

PurposeThe aircraft’s tyres are forced to spin up at touchdown. A considerable amount of frictional energy will be converted into heat, raising the tread temperature and leading to thermal wear. This study aims to develop a model to analyse the tread heat and discuss the effectiveness of two wear reduction methods.Design/methodology/approachThe tread temperature is calculated using Laplace’s Equation. The efficiency of pre-rotation and soft landing in reducing tyre heat is studied using a developed three-dimensional heatmap method.FindingsThe result indicates that pre-rotation can significantly lower landing gear’s heat generation at touchdown. The soft landing, instead, has an insignificant or counterproductive effect.Research limitations/implicationsThe pre-rotation can significantly increase the tyre’s lifespan and cut the replacement cost. The emission of tyre particles into the environment can be reduced to protect the planet and human health.Originality/valueFew studies have used a theoretical model to estimate the tread temperature. The existing studies have only dealt with the maximum tread temperature or the tread centreline temperature, which is insufficient to discuss the heat across the entire tread. However, the heatmap method in this paper can do the job.

Three-Dimensional Mechanistic Modeling of Time-Dependent Dielectric Breakdown in Polycrystalline Thin Films

Time-dependent dielectric breakdown (TDDB) is a crucial issue for the dielectric reliability. In this work, we present a full three-dimensional mechanistic model for calculation of the TDDB process in polycrystalline thin films. The model is based on the multiphonon trap-assisted tunneling theory and takes into account the intrinsic three-dimensional discreteness of traps at the dielectric grain boundaries. The leakage current density is calculated by solving coupled three-dimensional master equation and Poisson equation. The net phonon emission associated with each charge trapping and release event is treated as a local point heat source, which then enters the Fourier heat equation for three-dimensional temperature distribution calculation. The generated trap is determined by local temperature and electric field, which is subsequently included in the next round of calculation of electric and thermal properties. A positive feedback loop gradually leads to an increase of trap density, temperature, and leakage current density, and finally the dielectric breakdown. Our model can, to a good approximation, reproduce the experimental leakage current density-voltage characteristics and the Weibull distribution of time to breakdown at different dielectric thicknesses, stress voltages, and environmental temperatures. We find that in realistic devices, the three-dimensional trap-to-trap transport of electrons contributes a non-negligible part to the leakage current when the dielectric approaches breakdown. Our approach of three-dimensional mechanistic simulation is computationally efficient such that evolution of ${10}^{3}$ traps during the TDDB process can be easily performed on a standard desktop computer.

CFD simulation of a full-scale three-dimensional flow and temperature distribution inside a reactor under ocean conditions

A series of three-dimensional full-scale fluid flow simulations are performed based on an integrated thermal marine reactor under ocean conditions. The aim is to understand the effects of ship motions including rolling, heaving, and inclination on flow field and thermal–hydraulic performance. Both forced circulation and natural circulation are taken into account since the abilities of coolant to maintain its original motion under ocean conditions are different. The temperature distribution, velocity field, and flow rate distribution of a static reactor are presented first for comparison. After additional forces or accelerations are introduced, the flow field in the marine reactors subjected to different types of ocean motions is explored. Results show that the rolling motion would have more significant impacts on marine reactors in natural circulation concerning temperature and SG (steam generator) flow rate. In natural circulation, the SG flow rate fluctuation can reach 35 kg/s when the rolling angle increases to 45°, compared to the maximum fluctuation of 8 kg/s under forced circulation. The rolling motion also greatly affects the flow field and flow rate distribution at the core inlet. Obvious vortex flows can be observed in the annulus both for forced circulation and natural circulation. The core channel with the minimum flow rate appears to be randomly located for the reactor subjected to rolling motion. For reactors in heaving motion, the fluid velocity changes periodically, and the flow rate in the SG and core regions increases significantly with the increase of the heaving period and acceleration. As for inclined reactors, the average velocity in the core becomes smaller while the temperature increases as the inclination angle of the reactor increases.

NUMERICAL AND EXPERIMENTAL INVESTIGATION ON TRACKING OF FREEZING FRONT DURING THE CRYOSURGICAL FREEZING OF A TISSUE-MIMICKING MEDIUM

We report a combined numerical and experimental approach to determine the transient three-dimensional temperature distribution in a biogel medium subjected to freezing operation by a single cryoprobe. The cryoprobe tip temperature was measured using thermocouples and imposed as a boundary condition in numerical simulations. Numerical simulations have been supported by optics-based experiments conducted under similar operating conditions wherein the principles of lens-less Fourier transform digital holographic interferometry (DHI) have been employed to map the freezing phenomenon in a completely non-intrusive manner. The combined numerical and experimental findings have been made use of to propose a novel methodology for assessing the cooling performance of the cryoprobe. Three different cryoprobe insertion depths (id) viz., 2, 4, and 6 mm, were considered. The numerical estimations for the freezing front were within ± 1 mm margin when compared with the DHI-based intensity data. In the context of temperature values, the numerical predictions were within a ± 5 K margin as compared to the thermocouple data placed at some select locations inside the freezing medium. In addition to the freezing front, we successfully tracked planning isotherm propagation, a parameter that holds importance during cryosurgical planning. Furthermore, the whole-field temperature data predicted using numerical simulations were used to determine the transient cooling capacity of the cryoprobe. The lens-less Fourier transform DHI, in conjunction with numerical simulations, provided a reliable way to obtain the whole-field temperature, which could potentially be used to investigate the cryoprobe cooling characteristics.

Orthogonal dual-channel single-camera spectral imaging for online measurement of three-dimensional space–time evolution of temperature field in laser melt pool

Current temperature measurement technology in laser manufacturing cannot obtain the internal three-dimensional (3D) temperature distribution of the melt pool. Necessary information for laser-manufacturing process optimization is lacking, including the melt pool depth and depth-to-width ratio. We propose a method for 3D temperature measurement based on orthogonal dual-channel single-camera spectral imaging. The 3D temperature field distribution of the melt pool can be obtained by collecting projected radiation data from two perpendicular angles. Use of a single monochrome camera for spectral imaging at three wavelengths ensures excellent spatial and temporal consistency during measurements. To verify the feasibility of the method, we measured the 3D temperature field in a melt pool of 304 stainless steel irradiated by a Gaussian laser beam (continuous laser, 500 W) with different irradiation times. The results indicate that the temperature field exhibits an approximately axisymmetric distribution on each cross-section at different depths. The temperature is highest in the center and gradually decreases around it. As the depth increases, the high-temperature area (>1730 K) gradually becomes smaller, and the temperature of each cross-section decreases. The maximum temperature, depth, width, and depth-to-width ratio of the melt pool at different times were obtained from the measured 3D temperature distributions. With an irradiation time of 0–80 s, the maximum temperature of the melt pool exhibited three stages: rapid increase (20–2230 K), slow increase (2230–2280 K), and stabilization. The growth of the width and depth of the melt pool indicated a similar process, increasing rapidly at first and gradually slowing. The depth-to-width ratio decreased rapidly at first and gradually stabilized. The proposed method for 3D temperature measurement has potential use in laser manufacturing for process control and quality improvement.

Three-dimensional reconstruction of flame temperature and H2O concentration using water vapor integrated spectral band emission

Efficient and accurate reconstruction of flame temperature and species concentration is very useful for combustion monitoring. In this work, the integrated spectral band ratio (ISBR) method, which uses the ratio of two integrated spectral radiative intensities to infer temperature, is applied to reconstruct three-dimensional flame temperature and H2O concentration distributions. First, the ratio of two integrated spectral radiative intensities is justified by gas radiation theory to only depend on gas temperature, and the influence of gas concentration and pressure on the ratio is negligible. Then, a spectral band pair is carefully selected for the measurement with an atmospheric path between the detector and the flame. In the selected spectral bands, CO2 and CO emissions are negligible compared to H2O emission, and atmospheric absorption can be ignored. Meanwhile, gas temperature is monotonically related to the ratio of integrated spectral radiative intensities. When the uncertainty of the ratio is 2%, the error of reconstructed temperature is less than 38K with gas temperature close to 3000K, and the error decreases as the gas temperature goes down. Finally, numerical experiments on reconstruction of axisymmetric and non-axisymmetric flames are carried out. Results show that three-dimensional distributions of flame temperature and H2O concentration can be reconstructed with high accuracy.