Non-intrusive Temperature Measurement Research Articles

KHz Rate Fs/Ps-CARS Thermometry For Supersonic H_2/Air Combustion Studies

Accurate flow field measurements are essential to probe the phenomena involved in aeronautical engines undergoing high temperature and high turbulences. Indeed, reliable experimental datasets are needed to compare and validate numerical models. Among other laser diagnostics, Coherent Anti-stokes Raman Scattering (CARS) is a well-established non-linear spectroscopic technique used to probe harsh environments, since it provides non-intrusive local point measurements of chemical composition and temperature. We report here hybrid fs/ps Coherent Anti-Stokes Raman Scattering (fs/ps-CARS) thermometry campaign performed on N 2 in a supersonic H2 /air combustion. We used a mobile and compact laser architecture that shapes, synchronize and generates the laser beams necessary for CARS spectroscopy. The instrument was moved to a large-scale facility representative of a scramjet combustor (ONERA LAERTE/LAPCAT-II bench). H2 /air was injected during several burst at 0,12 and 0,15 equivalent ratios. Using kHz single-shot measurements combined with motorized translation stages, spatial and temporal resolution were obtained to probe the flow and the combustion at various positions upstream and downstream the hydrogen injectors. At these positions, horizontal and vertical temperature profiles were retrieved and compared with a numerical unsteady fluid dynamic simulation using delayed detached eddy simulations (DDES) developed at ONERA (CEDRE). The position of the combustion inside the combustion chamber could be identified through several horizontal and vertical profile temperature measurements. The signal-to-noise ratio of the detection was optimized by empirically adjusting the number of averaged laser shots based on the level of flow turbulence. For instance, far downstream the H2 injection, averaging over 10 to 100 pulses was possible as the heated air flow was steady. This was confirmed by the good agreement with numerical simulations although some distortion could still be observed and will be used to adjust the numerical simulation algorithm. However, averaging was no longer possible close to the injectors, where a highly turbulent H2 /air combustion was observed. Nevertheless, taking advantages of the high rate single-shot capacity of the spectroscopic technique, temperature could still be retrieved inside this area. These measurements provided a valuable experimental database for comparing and refining computational fluid dynamics modeling.

KHz Rate Fs/Ps-CARS Thermometry For Supersonic H_2/Air Combustion Studies

Accurate flow field measurements are essential to probe the phenomena involved in aeronautical engines undergoing high temperature and high turbulences. Indeed, reliable experimental datasets are needed to compare and validate numerical models. Among other laser diagnostics, Coherent Anti-stokes Raman Scattering (CARS) is a well-established non-linear spectroscopic technique used to probe harsh environments, since it provides non-intrusive local point measurements of chemical composition and temperature. We report here hybrid fs/ps Coherent Anti-Stokes Raman Scattering (fs/ps-CARS) thermometry campaign performed on N 2 in a supersonic H2 /air combustion. We used a mobile and compact laser architecture that shapes, synchronize and generates the laser beams necessary for CARS spectroscopy. The instrument was moved to a large-scale facility representative of a scramjet combustor (ONERA LAERTE/LAPCAT-II bench). H2 /air was injected during several burst at 0,12 and 0,15 equivalent ratios. Using kHz single-shot measurements combined with motorized translation stages, spatial and temporal resolution were obtained to probe the flow and the combustion at various positions upstream and downstream the hydrogen injectors. At these positions, horizontal and vertical temperature profiles were retrieved and compared with a numerical unsteady fluid dynamic simulation using delayed detached eddy simulations (DDES) developed at ONERA (CEDRE). The position of the combustion inside the combustion chamber could be identified through several horizontal and vertical profile temperature measurements. The signal-to-noise ratio of the detection was optimized by empirically adjusting the number of averaged laser shots based on the level of flow turbulence. For instance, far downstream the H2 injection, averaging over 10 to 100 pulses was possible as the heated air flow was steady. This was confirmed by the good agreement with numerical simulations although some distortion could still be observed and will be used to adjust the numerical simulation algorithm. However, averaging was no longer possible close to the injectors, where a highly turbulent H2 /air combustion was observed. Nevertheless, taking advantages of the high rate single-shot capacity of the spectroscopic technique, temperature could still be retrieved inside this area. These measurements provided a valuable experimental database for comparing and refining computational fluid dynamics modeling.

Non-intrusive temperature measurements for transient freezing in laminar internal flow using laser induced fluorescence

This work presents two color LIF temperature measurements for the transient freezing in a square channel under laminar flow conditions. This is the first time non-intrusive temperature measurements were performed within the thermal boundary layer during the transient growth of an ice layer in internal flow. A combination of a local outlier factor algorithm and a smoothing operation was used to remove the top to bottom striations and reduce the other measurement noise. The temperature uncertainty in our measurements was between σ=0.3∘C and σ=0.5∘C. For the largest temperature difference between the bulk and the melting point of 14.6 °C, good results were obtained. As such, the current campaign demonstrates the potential of LIF as a non-intrusive temperature measurement technique for solid–liquid phase change experiments. However, some artefacts were present within the vicinity of the ice-layer due to the scattering of the laser light, especially near the inlet of the channel where the ice-layer is curved instead of flat. LIF measurements taken within a short time span prior to the onset of ice freezing showed approximately 2 °C of subcooling, consistent with previous findings. In addition, an anomalous behavior within the thermal boundary layer was observed, with a much smaller temperature gradient within the first few mm above the cold plate and a point of inflection in the temperature profile. The anomalous temperature behavior is possibly attributed to enhanced natural convection as a result of the subcooling at the cold plate surface.

A state-of-the-art review on laser-induced fluorescence (LIF) method with application in temperature measurement

Laser-induced fluorescence (LIF) is a robust and vigorous method for non-intrusive measurement of temperature, pressure, concentration, and pH in fluids. The application of LIF for measurement is also extendable to solid and gaseous environments. In this method, the fluorescent molecules are transferred to a higher energy state by absorbing the energy of a laser beam and subsequently undergo spontaneous emission of light in the form of fluorescence during the transition to the ground. The emitted fluorescence is commonly captured using a setup consisting of a solvent, fluorescent material, detecting cameras, lenses, and filters, which enables the determination of the thermophysical parameters of the measuring environment using pertinent mathematical formulae. This method can be used for precise measurements in a wide range of engineering and medical applications. Despite the numerous studies on the utilization of LIF for measurement, there is not a comprehensive review paper with a focus on various types of LIF techniques and their applications in temperature measurement. This paper seeks to address this gap by fully discussing these approaches, demonstrating temperature measurements in different environments and circumstances, and outlining their benefits and drawbacks. Accordingly, one-dye one-color, two-dye two-color, one-dye two-color, one-dye three-color, two-dye three-color, volumetric LIF, and encapsulation techniques are fully discussed as the main LIF approaches and their applications for the temperature measurement in fluid flows, droplets, microfluidics, and gas environments.

A fast sensor for non-intrusive measurement of concentration and temperature in turbine exhaust

Accurate and rapid measurement of water vapor concentration and temperature in the exhaust of gas turbine engines is critical for monitoring their health and operational performance. To monitor the two parameters simultaneously, a non-intrusive sensor based on tunable diode laser absorption spectroscopy is developed using 8 laser beams targeting 3 transitions of water vapor. The sensor has in situ validated on a commercial auxiliary power unit. Seven parallel laser beams at 5000.2 cm−1 are 6.3 mm spaced at the plume boundary to characterize the edge effect between hot exhaust plume and cold surrounding flow. One beam, operating at the dual wavenumbers of 7185.6 cm−1 and 7444.4 cm−1 penetrates the plume through centerline to measure temperature via ratio thermometry. Then, this temperature information is used to obtain the concentration of water vapor. A temporal resolution of 4 ms is achieved for the 8-beam measurement, enabling high-speed and simultaneous quantification of the edge effects and the plume parameters. Results indicate water vapor concentration and temperature in the exhaust measured by the developed sensor are highly consistent with the traditional benchmarks, e.g., extractive sampling and thermocouples, with a difference of 0.02% and 3 °C, respectively. Enabled by its continuous millisecond-level measurements, the sensor, for the first time, reveals hidden engine behaviors and combustion dynamics that are unable to be observed by the traditional methods, thus facilitating next-generation real-time gas turbine engine control towards low emissions.

Toward Gas-Phase Thermometry Using Pure-Rotational Impulsive Stimulated Raman Scattering Spectroscopy with a Low-Energy Femtosecond Oscillator

Femtosecond coherent Raman techniques have significant diagnostic value for the sensitive and non-intrusive measurement of temperature, pressure, and composition of gas mixtures. Due to the low density of samples, however, such measurements make use of high-energy amplified laser sources, with unwieldy and costly experimental setups. In this paper, we demonstrate an experimental setup equipped with a low-energy and low-average-power femtosecond oscillator allowing measurement of the pure-rotational spectrum of nitrogen down to atmospheric pressure using impulsive stimulated Raman scattering. Using a simplified model to analyze the experimental data we were able to derive the gas temperature with reasonable accuracy.

Nonintrusive temperature measurement of a combustion field by femtosecond laser-induced third harmonic generation

We report a comparative experimental investigation of femtosecond laser-induced third harmonic generation (THG) in an ethanol flame and in air. It was found that the third harmonic (TH) signal produced in the presence of a combustion field can be greatly enhanced, in comparison to that generated in air, and that the enhancement factor depends strongly on the experimental parameters, such as the focal length, relative position of the flame and filament, and laser repetition frequency. Moreover, by replacing the flame with a point temperature controller, a similar signal enhancement of THG was observed, and the TH signal exhibited a nonlinear growth with the heating temperature. Further analysis indicated that the observed enhancement of THG originates from the suppression of Gouy-phase-induced destructive interference due to the disturbed gas density under high-temperature heating. The high sensitivity of the TH signal to the combustion temperature helps formulate an effective and straightforward approach to achieve nonintrusive temperature measurements in the combustion field.

A Review on Acoustic Reconstruction of Temperature Profiles: From Time Measurement to Reconstruction Algorithm

Acoustic tomography is a technique widely used in non-intrusive temperature measurement. Times of flight (TOF) of acoustic waves can be used to estimate temperatures of a measurement area. After obtaining TOF of some transmitter-receiver pairs, the temperature profile of the probed area can be estimated by some reconstruction algorithms. Temperature profiles play a critical role in the safe operation and efficient control of thermal-related mechanical systems. This article aims to present a systematic review on the acoustic reconstruction of the temperature profile, including TOF measurements and reconstruction algorithms. First, time-domain, Fourier-domain, and hybrid domain methods for the TOF measurement are revisited and discussed. Second, algorithms for the solution of the reconstruction model are reviewed from three groups of regularization methods. We also discuss how to choose the regularization parameter and to form a good preconditioner for fast calculation. Third, some extensions in TOF measurements and reconstruction methods and potential errors that may affect the acoustic reconstruction are also discussed. Finally, some applications are presented. A framework for the whole reconstruction process can be a useful resource to help researchers select a proper method for specific applications.

Simultaneous velocity profile and temperature profile measurements in microfluidics

Simultaneous non-intrusive temperature and velocity measurements in flows are of high technological interest, e.g. to study the heat transfer in microfluidic environments. However, a measurement system that offers a low velocity uncertainty and micrometre spatial resolution as well as highly accurate temperature measurements in a single device has not been demonstrated so far. In this work, this problem is solved by combining a Laser Doppler Velocity Profile Sensor (LDV-PS) with Laser-Induced Fluorescence (LIF). Seeding particles are employed, that contain the fluorescent dyes uranine and rhodamine B. The multiple dye approach eliminates the influence of the droplet size. Relative velocity uncertainties of down to 0.4% and a temperature uncertainty of down to 0.24∘C with a spatial resolution of 10μm are achieved in a demonstration air flow experiment. The method has the potential to be optimised for different temperature ranges and uncertainty requirements, making it applicable on a wide range of thermal flows like fuel cells or microbioreactors. A better understanding of heat exchange processes can improve the energy efficiency of microfluidic devices.

Fuel cell behavior and energy balance on board a Hyundai Nexo

Hydrogen fuel consumption measuring methodologies of a fuel cell vehicle without modifying the fuel path has been tested and benchmarked. In this work, they are applied to a Hyundai Nexo fuel cell electric vehicle driving different mission profiles on a chassis dynamometer. Three methods respectively based on hydrogen tank pressure, tailpipe oxygen concentration, and IR-shared (infrared) tank data are compared to the reference method relying on fuel cell current measurements. In addition to the hydrogen fuel consumption results, the installed electrical measuring equipment made possible to yield the fuel cell efficiency map at both stack and system levels as well as the energy consumption of its balance-of-plant (BoP) components during steady-state operation. A maximum steady-state efficiency of 66.8% is reported along with a rated system power of 82 kWe involving a 9.1-kWe power consumption for the electric compressor. It is shown that the compressor and the 12-V accessories are the most energy consuming devices among the BoP components accounting for 2%–3% of the total electric energy generated by the fuel cell. Furthermore, the behavior of the powertrain system is monitored and discussed during warm-up phases and during a long idling period. Finally, based on non-intrusive temperature measurements, a short analysis is conducted about the temperature impact on the fuel cell efficiency.

Temperature measurements and high-speed photography of micron-sized aluminum particles burning in methane flat-flame exhaust

This work seeks to investigate the ignition and burning of micron-sized aluminum particles using nonintrusive temperature measurements and high-speed photography. First, the detected emission spectra were used to deduce the particle temperature according to Planck’s laws, and the emissivity dependence on the wavelength was determined. Second, the ratio pyrometer method using a Nikon digital camera was developed to specify the two-dimensional temperature profile. These two methods were preliminarily validated through a B-type thermocouple of known temperature. Further, aluminum particles with controlled sizes of approximately 45 and 125 µm were injected as a well-dispersed stream or discrete single particles, respectively, into the hydrocarbon combustion exhaust with controlled gas temperature and compositions. The temperature evolutions of 45 µm aluminum particles derived from the camera pyrometer are in reasonable agreement with the numerical results predicted by a previously developed model. Regarding 125 µm particles, the temperature contour shows a sharp temperature increase and flame expansion during ignition. It can be attributed to the transition from surface reaction to more vigorous combustion in the vapor phase, which was visualized by a high-speed camera equipped with a long-distance microscopic lens. In this work, the camera pyrometer has demonstrated the capability of measuring the average projected particle temperature and characterizing the combustion process of micron-sized aluminum particles, with promising simplicity and economy.

Identification of the thermo-physical properties of a stratified tissue. Adiabatic hypodermic wall

Biological living tissues possess thermophysical properties that are difficult to measure directly and their estimation is very important in order to decide the appropriate treatment procedure (e.g. place of inoculation and appropriate amount of drug dosage) in case an abnormality is detected. In the present paper, we numerically investigate, for the first time, the determination of several thermo-physical blood-tissue properties of a one-dimensional, multi-layered biological skin tissue subjected to external heating. In contrast to the usual parabolic model that assumes infinitely fast propagation of the heat signal, in the present paper, the bio-heat transfer in such a biological body is mathematically modelled by a hyperbolic partial differential equation, which takes into account that the thermal wave speed is finite. On the skin surface a convective boundary condition holds taking into account the heat exchange with the environment, whilst on the most inner wall of the tissue an adiabatic boundary condition applies. Then, in this framework, the piecewise constant thermo-physical properties of interest given by the thermal conductivity, heat capacity and blood perfusion rate are accurately and stably reconstructed from non-intrusive temperature measurements on the inner and outer boundaries of the multi-layered tissue by minimizing a weighted nonlinear least-squares objective function.

3D printed optofluidic biosensor: NaYF4: Yb3+, Er3+ upconversion nano-emitters for temperature sensing

The nonintrusive, realtime, and accurate measurement of the local temperature has applications in a variety of scenarios. This need has led to significant research to develop novel nanophotonic sensors. In this paper, a 3D-printed optofluidic chip is nano-engineered for local, contactless, and precise optical measurement of temperature in microfluidic channels using lanthanide-doped upconversion nanoparticles. Temperature sensing nano-emitters are doped in a UV-curable matrix and embedded into a microfluidic channel using maskless photolithography. Photoluminescence of NaYF4:Yb3+, Er3+ upconversion nanoparticles have two bands in the green spectrum in which the PL maximums at 521 nm and 541 nm are used for temperature sensing. Thus, enabling ratiometric temperature sensing when excited using near-infrared light, which is desirable for measurements in biological and biomedical settings. The functionality of the temperature sensor for local and nonintrusive measurements in a microalgae culture medium is demonstrated.

Ultrasonic Thermometry Algorithm Based on Inverse Quadratic Function.

At present, there are two ways to obtain temperature information: contact type and nonintrusive type. As a nonintrusive temperature measurement method, ultrasonic thermometry can be used to acquire the temperature distribution of complex fields conveniently. By measuring the time-of-flight (TOF) between ultrasonic transmitters and receivers, and according to the relationship between temperature and ultrasonic velocity, the temperature distribution can be reconstructed. Among the existing algorithms, the least square method (LSM) will lose much information near the edges of the temperature field, and the algebra reconstruction technique (ART) is time-consuming with low reconstruction accuracy. In this article, an improved reconstruction algorithm based on an inverse quadratic function and singular value decomposition (IQ-SVD) is proposed, which can effectively increase the reconstruction accuracy. The simulations of the real temperature data are conducted in ideal and noisy environments, respectively. Moreover, the influence of region division and shape parameters on reconstruction accuracy is discussed. The simulation results indicate that, compared with conventional algorithms, the proposed algorithm can accurately reflect the temperature distribution, and the root mean square error in the central region and the edge region is reduced by 0.49% at least, and 1.28% at most.

Soot temperature measurement within 3D flame by light-field imaging based on wave optics theory

Light-field imaging technique provides a new approach to non-intrusive temperature measurement, which can achieve 3D measurement via single detector equipment. We consider wave characteristics of radiation rays in the light-field imaging model in this work. We propose an improved light-field imaging model of an emitting and absorbing medium by combining wave optics theory and radiation transfer process in semitransparent media. The combination of Fresnel diffraction theory and phase conversion principles of the lens provides a theoretical basis for a description of radiation ray propagation in space and across the lens. The point spread function of the light-field camera can be calculated and used to attain a light-field image in accordance with the convolution imaging model. The light-field image of the flame is regarded as input to reconstruct the soot temperature field of a 3D flame. Inverse problem is formulated as a linear optimization problem and solved by Landweber algorithm. Simulated reconstruction results show that axisymmetric and non-axisymmetric temperature distribution can be reconstructed successfully, thereby verifying the applicability of the presented method. The effect of the measurement noise and the Tikhonov regularization on the reconstructed quality of the temperature are investigated as well. The results show that the temperature can be reconstructed with acceptable accuracy under different noise levels. Tikhonov regularization method is proven available in this problem.

Standard thermography vs free emissivity dual color novel CIRA physics technique in the near-mid IR ranges: Studies for different emissivity class materials from low to high temperatures typical of aerospace re-entry

The dual color infrared thermography is a non-intrusive temperature measurement technique, based on the ratio principle between the signals collected at two near wavelengths in local grey body hypotheses and applicable when a thermal camera is equipped with a suitable pair of narrow band filters. In this work, the applicability at high temperatures has been investigated by using an analytical model based on Planck's Law integration, convoluted with the real response curves of sensors, optics, filters and attenuators. The presented model has been validated at high temperature and used to optimize the hardware set up for dual color measurements both in terms of operative spectral band and also for choosing the best pair of filters. Furthermore, spectral emissivity trend curves for different materials, available in literature, and at different temperatures have been used in the theoretical model in order to simulate and replicate experimental results. The experimental simulations obtained with dual color technique have been compared with those obtained through classical techniques based on the a priori knowledge and setting of the emissivity average values.The aim is to establish in which conditions and for which class of Thermal Protection System (TPS) materials used to protect the inner cold structure of hypersonic space vehicles made of aluminium or metallic alloys, the dual color technique can be used for a more accurate and precise temperature measurement compared to the classical techniques. The applicability study was carried out up to high temperature (2000 °C) which are reached by the TPS surfaces during the re-entry phase from Earth orbit or from interplanetary trajectories due to the high heat flux loads produced by the strong shock wave during the deceleration phase.

A Review of Femtosecond Laser-Induced Emission Techniques for Combustion and Flow Field Diagnostics

The applications of femtosecond lasers to the diagnostics of combustion and flow field have recently attracted increasing interest. Many novel spectroscopic methods have been developed in obtaining non-intrusive measurements of temperature, velocity, and species concentrations with unprecedented possibilities. In this paper, several applications of femtosecond-laser-based incoherent techniques in the field of combustion diagnostics were reviewed, including two-photon femtosecond laser-induced fluorescence (fs-TPLIF), femtosecond laser-induced breakdown spectroscopy (fs-LIBS), filament-induced nonlinear spectroscopy (FINS), femtosecond laser-induced plasma spectroscopy (FLIPS), femtosecond laser electronic excitation tagging velocimetry (FLEET), femtosecond laser-induced cyano chemiluminescence (FLICC), and filamentary anemometry using femtosecond laser-extended electric discharge (FALED). Furthermore, prospects of the femtosecond-laser-based combustion diagnostic techniques in the future were analyzed and discussed to provide a reference for the relevant researchers.

Simultaneous estimation of thermal properties of orthotropic material with non-intrusive measurement

This article presents a simple in-house laboratory experiment method for the simultaneous estimation of principal thermal conductivity and specific heat capacity of an orthotropic composite with non-intrusive temperature measurement. The principle of method involves in symmetrical heating of two identical samples with a planar heater sandwiched in-between them and measuring the temperature of non-heated surface non-intrusively using IR camera. The forward problem that mimics the heat conduction from heater to sample and then to ambient is a 3-D transient conduction equation which is solved using finite volume method whereas inverse problem is solved using Levenberg-Marquardt algorithm. At first numerical estimations are carried out with synthetic temperature data to decide upon the parameters to be identified/fixed as well as to find optimal experimental variables. Then, using measured temperature response of the non-heated surface, the thermal properties of unidirectional fiber reinforced carbon composite are estimated. Induced bias errors in the estimated parameters because of error in the fixed parameters are also approximately quantified. The estimated transverse thermal conductivity is found to be 0.72 W/m K whereas the in-plane conductivities parallel and perpendicular to fiber are 5.43 W/m K, 0.64 W/m K respectively. Also, the estimated specific heat capacity is found to be 1044 J/kg K. A maximum deviation of 10% from the absolute Guarded Hot Plate measurement is found in the estimated thermal conductivity parallel to fiber.

Resolving multiple combustion parameters from a single transition using degraded deconvolution of Voigt lineshape

A novel algorithm to fast deconvolve a molecular transition for its Gaussian and Lorentzian broadening was reported, and was further used to simultaneously measure multiple parameters, i.e. species concentration, temperature, and pressure, for combustion diagnostics. The proposed method was demonstrated by theory simulation and laboratory verification with combustion experiment. Direct absorption spectroscopy of H2O transition at 7185.6 cm−1 in premixed methane/air flames is used to verify the accuracy. The measurement temperature is agreement with that by two-line thermometry and thermocouple. The method is simple and feasible for non-intrusive simultaneous measurements of gas temperature, concentration, and pressure without calibration or other contact sensors. With an appropriately selected spectral line for analysis, the method can be applied to combustion diagnostics and industrial process control applications.

Combined tunable diode laser absorption spectroscopy and monochromatic radiation thermometry in ammonium dinitramide-based thruster

Nonintrusive temperature measurements for a real ammonium dinitramide (ADN)-based thruster by using tunable diode laser absorption spectroscopy and monochromatic radiation thermometry are proposed. The ADN-based thruster represents a promising future space propulsion employing green, nontoxic propellant. Temperature measurements in the chamber enable quantitative thermal analysis for the thruster, providing access to evaluate thermal properties of the thruster and optimize thruster design. A laser-based sensor measures temperature of combustion gas in the chamber, while a monochromatic thermometry system based on thermal radiation is utilized to monitor inner wall temperature in the chamber. Additional temperature measurements of the outer wall temperature are conducted on the injector, catalyst bed, and combustion chamber of the thruster by using thermocouple, respectively. An experimental ADN thruster is redesigned with optimizing catalyst bed length of 14 mm and steady-state firing tests are conducted under various feed pressures over the range from 5 to 12 bar at a typical ignition temperature of 200°C. A threshold of feed pressure higher than 8 bar is required for the thruster’s normal operation and upstream movement of the heat release zone is revealed in the combustion chamber out of temperature evolution in the chamber.