Axial Temperature Distribution Research Articles

High spatial resolution temperature variation detection in one direction with a fiber solenoid and RDTS system

Limited by the large bottom width of the pulsed light and the large sampling spacing of the data acquisition card in conventional Raman distributed temperature sensing (RDTS) systems, short straight fibers cannot acquire temperature measurements with high spatial resolution and high temperature accuracy in a single temperature variation region (TVR). In contrast, winding sensing fiber on a screwed tube as a fiber solenoid for temperature sensing can indirectly improve the spatial resolution of the system. However, as the radius of the screwed tube decreases, the ability of the screwed tube to improve the spatial resolution of the system will deteriorate. To break this limitation, we innovatively propose a signal processing scheme to first construct a three-dimensional surface of the sensing length of screwed tube-temperature-area value, then obtain the length of the TVR and the area value of the temperature rise curve generated from a single TVR, and finally demodulate the temperature of the TVR in the surface. The experimental results show that the proposed scheme improves the spatial resolution of the conventional screwed tube from 8 cm to 1 cm, and the average temperature accuracy of the three TVRs with the interval and length of the TVRs in the order of centimeters is ± 0.63 °C. The screwed tube can be used for axial temperature distribution measurements of liquids as well as solids, and the proposed method can further expand the application prospects of the RDTS system for continuous measurement of multiple TVRs with lengths and intervals of centimeters in one direction without changing the internal hardware.

Numerical study on the characteristics of sodium heat pipes for space application at operation limits

Sodium heat pipes are important thermal conductive components in space nuclear power sources. They efficiently transfer heat within the range of 500–1000 °C by utilizing the latent heat of phase change. However, their maximum heat transfer capacity is limited by various factors. In this study, numerical simulations were conducted to investigate the operating conditions of sodium heat pipes when encountering different heat transfer limits, with a focus on analyzing the vapor–liquid distribution and axial temperature distribution in evaporator section. It is revealed that as reaching the heat transfer limits, sodium heat pipes exhibit wall temperature fluctuations in evaporator section. When encountering the viscous limit, liquid aggregation occurs within the wick, causing discontinuous flow. As reaching the sonic limit, a vapor blockage zone forms at the outlet of evaporator section, disrupting the flow circulation within heat pipe. For the entrainment limit, the liquid inside wick is carried away by vapor flow, reducing the amount of liquid involved in phase change cycle. As in the capillary limit, inadequate liquid reflux leads to thinner liquid layer, weakening the flow circulation. During the transition from the viscous limit to the sonic limit, no significant phenomena of phase distribution occur in the evaporator section. As the sonic limit and the entrainment limit act together, both vapor blockage and liquid entrainment occur, accompanied by liquid accumulation. The phenomena when the entrainment limit and the capillary limit act together differ from those occurring individually. The simulation results provide references for a deeper understanding of heat transfer limit mechanism and other operating characteristics.

Electrohydrodynamic peristaltic microfluidic flow with thermal and molecular analysis featuring sloped configurations

This study examines the simultaneous impacts of thermal and molecular transfer of non-Newtonian fluid propelled by the collective impact of electroosmosis and peristaltic pumping via inclined channel. Internal frictional heating and heat generation are also taken into consideration. The electrohydrodynamic phenomenon is described by the nonlinear Poisson–Boltzmann equation. The problem is modulated mathematically through a system of coupled non-linear differential equations in wave frame of reference. Using the regular perturbation method around a small wave number δ, we obtain sequential solutions for stream function ψ, electric potential ϕ, velocity u, pressure gradient dpdx, temperature θ and concentration Ω distributions. The influences of newly arising parameters such as the electroosmotic parameter me, relaxation time parameter λ1, retardation time parameter λ2, wave number δ, Reynold’s number Re, heat generation parameter β, Prandtl number Pr, Schmidt number Sc, Froude number Fr and Soret number Sr on physical characteristics are analyzed graphically. There is an inverse correlation between the parameters of relaxation time and retardation time and their effects on axial velocity, concentration, and temperature distributions. In particular, the temperature of the fluid increases as the EDL parameter, relaxation time parameter, viscous dissipation parameter, and Reynolds number increase, but decreases as the retardation time parameter increases. Moreover, the axial pressure gradient increases as Reynolds number and inclination angle increase, while it decreases as Froude number increases. The current model has applicability in the chemical industry, reservoir engineering, micro-fabrication, and biomedical applications, where electroosmotic effects on heat and mass movement are crucial.

Fuel fragmentation and relocation (FFR) model in SPACE code PART 1: Development and verification

Ballooning of cladding, which can happen during a loss of coolant accident (LOCA), causes relocation of fragmented fuel. Recently, consideration of fuel fragmentation, relocation, and dispersal (FFRD) phenomena for safety analyses has been requested by a regulatory body. Therefore, new models related to the fuel fragmentation, relocation, and dispersal (FFRD) in SPACE code have been developed. In this study, the FFR model, excluding dispersal, will be discussed. The fuel fragmentation and relocation models, which were developed by Quantum Technology (QT), are modified and developed in SPACE code. In particular, the fuel relocation limitation threshold parameter and the fuel power distribution during relocation are newly developed. The FFR models are also verified with simple known problems. The newly developed and implemented FFR models in SPACE are validated with calculations using Halden IFA-650 test data. The newly developed FFR model in SPACE can reasonably predict the fuel relocation and axial rod temperature distribution due to fuel mass redistribution. However, intensive validation tests including various conditions are necessary to validate the new FFR model in SPACE code.

Characterizing pulverized coal combustion for high-ash content Indian coal

ABSTRACT The present study performs three-dimensional (3D) numerical simulations of coal combustion of four samples with varying ash content in a drop tube furnace (DTF) to mimic the particle heating rates observed in industrial furnaces. The numerical framework adopted is validated with prior experimental and simulation results using a 3D cylindrical geometry and a very good match is obtained for the axial temperature distribution and particle burnout rate. The combustion performance of coal samples with varying ash contents of 2.3, 16.6, 24.1, and 37.2 wt%, is explored through temperature profiles, burnout rates, particle tracking, and mass fractions of various products of combustion. A user-defined function is used to specify the 14 species, 10-step solid particle combustion with a modified eddy dissipation concept model for volatile combustion. The range of ash content considered is for Indian coal which has a high degree of heterogeneity, making the evaluation of its combustion performance, a challenge. The present work aims to provide benchmark set of results showing the evolution of the evaporated, charred, and volatile mass for the three ash contents, which has not been attempted before. It is found that the high-ash content Indian coal samples have a tendency to produce less . A reduction in the is obtained for the coal sample with ash compared to that with ash. The results suggest that the combustion performance is enhanced when the ash content falls within an optimum range of .

Simulation and enhancement of axial temperature distribution in a reactor filled with in-situ electrically heated structured catalyst

The hydrogen production technology based on the in-situ electrically heated structured catalyst (EHSC) has the advantages of compact structure, fast response, and less CO2 emissions. However, there is still a lack of research on the temperature distribution of the reactor filled with EHSC. Based on the problem, a CFD model was established, and the temperature distribution was revealed. To further reduce the large temperature difference in axial direction, the effects of the gradient-pitch design and segmented-voltage-control design for the EHSC on the temperature distribution and methanol conversion were studied numerically. The results showed that segmented-voltage-control design can significantly reduce the maximum axial temperature difference, due to the fact that the reaction heat and corresponding Joule heat supplied at each axial section were flexibly well matched. When reaction temperature was 275 °C, the maximum temperature difference decreased from 84.7 °C to 31.1 °C. Moreover, when GHSV was 13000 ml/(g h), methanol conversion was improved by up to 10.9%. The segmented voltage control method for the EHSC provides an opportunity to design an isothermal endothermic reactor under any reaction conditions in the case of further optimization of segmented-voltage-control design.

Cooling performance of the hot-rolled seamless steel tube with different jet forms

The jet form is closely related to the cooling strength and uniformity of steel tubes, which is the first consideration in the design of quenching equipment. A reasonable choice of jet form will improve product quality and reduce production costs. In this study, the heat transfer behavior of different jet forms is discussed. Two jet forms are considered: planar jet and annular jet. Besides, the size of the steel tube is also an important variable in this simulation. The remaining parameters are fixed values. The axial and circumferential temperature distributions of the steel tube were obtained. The results showed that the annular jet has better performance on cooling intensity and cooling uniformity. The cooling performance of the two jet forms are almost the same when the steel tube size is smaller than 50 mm. As the planar jet quenching equipment is simple to manufacture, low in cost, and convenient in site application, so the planar jet can be considered when the diameter is small.

Consequences of variable wall permeability and magnetic field on non-isothermal flow in converging/diverging tubes

The current article is devoted to the development of a theoretical model investigating heat transfer analysis of MHD blood flow through renal tubules. For this purpose, we consider the transport of Newtonian fluid inside a non-uniform tube whose lateral surface is kept at constant temperature. The walls of tube are considered to admit the variable permeation and the flow is actuated by an externally applied magnetic field. The solution of the problem is formulated analytically in terms of axial and radial velocities and temperature distribution under the presumption of lubrication approximation in the inertia free flow field. Implication of Darcy’s law for fluid seepage across the tubular membrane results in an ordinary differential equation having variable coefficients for the unknown pressure, which is successfully computed numerically using RK45 routine. Performance of velocity, pressure and temperature distributions has been investigated for various values of the physical parameters involving in the model. Moreover, flow rate behavior, fluid reabsorption and the leakage flux has been analyzed through graphs and tables. The characteristics of heat transfer in the flow field is also evaluated for various values of Brinkman number. A significant discovery reported in the results of present model reveals that the axial flow exhaustion and radial flow reversal are significantly influenced by the tube converging/diverging parameter and the Hartmann number as well. By employing a strong magnetic field, exhaustion and reversal phenomena in the flow field can be restrained up to a certain limit. Moreover, with an increasing wall permeability, there is a significant exhaustion of axial flow in a divergent tube and a prominent assistance takes place in the radial flow reversal for convergent tube. It is hoped that the present model will bear the potential to study flow in renal tubules and in hemodialyzer.

The axial temperature distribution of the channel in the linear reactivity model

Employing a linear reactivity burnup-dependent model, we investigate how the new axial flattened power densities (Pontes and Driscoll models) affect the steady-state axial temperature distributions of the sub-channel in pressurized water reactors (PWR). Two approaches were used: analytical, using mean parameters, and numerical, using appropriate empirical correlations. The Pontes distribution showed advantages in all evaluated regions except in the centerline of the fuel rod, outperformed by the Driscoll distribution. The results indicate that the linear reactivity model (LRM) is extremely advantageous in the evaluated reactor, as it reduces axial temperatures on hot spots and has the potential to enhance the reactor’s safety, efficiency, and longevity.

Novel revolving heat pipe cooling structure of permanent magnet synchronous motor for electric vehicle

The high temperature rises and uneven axial temperature distribution of permanent magnet synchronous motors applied in electric vehicles can lead to demagnetization of permanent magnets and turn-to-turn short circuit failures in the windings. Thus, a cooling structure based on revolving and fixed annular heat pipes is proposed. That is the revolving heat pipes are installed in the rotor, which are further increasing the rotor's heat transfer efficiency under the centrifugal force of rotor rotation. The fixed annular heat pipes are installed in the stator to cool the windings, especially the end of the windings. The experiments are designed to derive the equivalent thermal conductivity of the proposed revolving and fixed annular heat pipes on this basis. The effectiveness of the proposed cooling structure is verified by computational fluid dynamics simulations which are conducted in three typical operating conditions of the motor used in electric vehicles. The results show that the temperature rise of the rotor, permanent magnet and winding are decreased by up to 70.39%, 69.4%, and 46.18% respectively by the proposed cooling structure. It indicated that the axial temperature rises distribution of heat generating parts can be effectively equalized, and the operating time under maximum torque condition can be effectively extended, that from 30 s to 100 s.

Heat behavior and axial temperature distribution of a Ti-6Al-4V alloy in a superconducting induction heater with a controllable magnet structure

Ti-6Al-4V (TC4) metal billets can usually be preheated by gases, resistance furnaces, and conventional induction heater powered by alternating current. However, the disadvantages of these heating methods are long heating time and small skin depths. The novel superconducting induction heater has several advantages in terms of heating quality, heating efficiency, heating time and axial temperature control. It has gained successful commercial application in the large aluminum extrusion industry in 2021. However, no studies on TC4 heating behavior using a superconducting induction heater have been reported, and no studies on uniform and gradient temperature characteristics of TC4 in superconducting induction heater. The uniform temperature distribution of TC4 is helpful to reduce the heating residual stress of forgings. The gradient temperature distribution of TC4 billet can obtain different properties in different parts of the same TC4 billet, which is suitable for manufacturing functionally graded materials. In this study, a high-temperature superconducting (HTS) direct-current (DC) induction furnace was firstly used to perform heating experiments for TC4 metal billets of 1250 mm length and 220 mm diameter. The application of the superconducting magnet for induction heating allows for high-power and fast heating of the TC4 billet at an extremely low frequency (4 Hz). The HTS induction heater technology has the advantages of high penetration depth, high energy efficiency (>82%), high heating uniformity, and controllable temperature distribution. Additionally, it improves the metal heating quality and reduces the heating cost. The 10 identical iron pieces of superconducting magnet on both sides of the iron core can be adjusted independently. The gradient and uniform temperature distributions of the thermally optimized TC4 billets were experimentally determined using adjustable electromagnetic heating power. Subsequently, the heating behavior of TC4 billets was modeled and compared using the numerical multiphysical finite element method; the results obtained using this method are in agreement with the experimental results. An expert database has been established for the heating strategy of TC4 billets. The optimized axial temperature distribution was analyzed for three different TC4 billet diameters (Φ220, Φ300, and Φ446 mm). The obtained gradient and uniform axial temperature distributions had an error of less than ±3 °C, and the adjustable difference at two-ends temperature of TC4 billets was in the range 10–100 °C/m. Finally, the maximum thermal stress on the TC4 billet during heating also was analyzed. The results of this study will be useful of the novel HTS induction heater application for TC4 billet heating, and axial temperature control. The uniform temperature distribution control will reduce the heating residual stress of forgings. The gradient temperature distribution of TC4 billet is suitable for manufacturing functionally graded materials.

Thermal and physical impact of viscoplastic nanoparticles in a complex divergent channel due to peristalsis phenomenon: Heat generation and multiple slip effects

In the advance studies, researchers have performed productive research contributions in the field of nanofluid mechanics under various biological assumptions. These contributions are fruitful to understand the applications of nanofluids in the various fields such as hybrid-powered engine, heart-diagnose, to prevent numerous diseases, heat exchanger, pharmaceutical processes, etc. The current analysis explores the combined effects of heat generation and chemical reaction on the peristaltic flow of viscoplastic nanofluid through a non-uniform (divergent) channel. The physical effects of second-order velocity slip, thermal slip and mass slip parameters on the rheological characteristics are also considered. To describe non-Newtonian effects, the Casson fluid is deployed. The greater wavelength assumption and low Reynolds number theory are used to attain the rheological equations. Numerical solutions of these governing equations associated with suitable boundary conditions are obtained via Mathematica symbolic software. The velocity magnitude of Casson fluid is higher than associated with Newtonian fluid. Radiation parameter has a vigorous impact in the reduction (enhancement) of temperature (mass concentration) profile. The porous parameter has a remarkable impact in reduction of temperature and velocity profile. Thermal enhancement is perceived by intensifying the chemical reaction parameter, and opposite inclination is noticed in mass concentration. Temperature has been demonstrated to be increased by increasing the Darcy number. The magnitudes of both axial velocity and temperature distribution are smaller in the presence of second-order velocity slip parameters effect as compared with no-slip condition. The magnitudes of axial velocity and mass (or, nanoparticle) concentration are augmented by accumulating the Prandtl number. A rise in Brownian parameter is noticed to depress the mass concentration. The present study has been used in bio-mechanical processes, nanomaterial devices, heat transfer enhancement, radiators, and electronics cooling systems.

Experimental investigation of nozzle submergence depth on steam cavity thermal characteristics in direct contact condensation

Direct contact condensation has found wide applications in an industrial sector because of its enormous mass and heat transfer capabilities. In the current experimental investigation, effect of submergence depth has been analyzed on the thermal characteristics of steam plume issuing into water tank from two geometrically different steam spray nozzles i.e. converging–diverging (CD) nozzle and straight pipe (SP) nozzle. The steam cavity images were taken using high-speed camera which were processed by MATLAB image-processing tool for the measurement of steam-water interfacial area. It was observed that axial temperature distribution rises with the increase in submergence depth while for radial temperature distributions reverse was found to be true. Additionally, the temperatures at nozzle exit were noted to be independent of submergence depth. The heat transfer coefficient decreases as the steam pressure, water temperature and submergence depth is increased for both the nozzles and found in range of 1.661–2.91 MW/m2·K and 1.472–1.989 MW/m2·K for the CD and SP nozzle, respectively. Moreover, the effect of submergence depth was found to be almost negligible at the higher submergence depth values.

Design and optimization of heat extraction section in energy tunnel using simulated annealing algorithm

Energy tunnel has attracted increasing interest in preventing tunnel frost damage and providing energy for space conditioning through utilizing geothermal energy from ground source heat pump (GSHP) system. The energy lining system, composed of heat pump units, lining buried with geothermal heat exchangers (GHEs), and supply pipes, is one of the most popular energy tunnel systems. Despite their good potential for geothermal energy exploitation, studies on their design approach are still insufficient, particularly for cold region energy tunnels. In this work, we propose an innovative design framework for optimization of the heat extraction section in the energy tunnel by combing numerical simulation and Simulated Annealing (SA). The numerical model reproduces a horseshoe-shaped tunnel segment equipped with an energy lining system, generating heat power activated by circulating heat carrier fluid. And the simulation provides key input parameters, involving heat extraction power, the ground temperature field, and heating demand, for the algorithm, hence the heat extraction section range is optimized using SA. Influences of four design parameters (i.e., ground temperature, inlet fluid temperature, circulating fluid flowrate, and pipe spacing) and three axial temperature distribution characteristics (i.e., overall temperature along the tunnel axis, airflow characteristics, and temperature difference between the tunnel entrance and exit) dominating temperature profiles along the tunnel axis on the optimal range design are investigated. Major findings include: (1) the optimal range is sensitive to the temperature field along the tunnel axis, and the normalized optimal length decreases by 91.3% with the normalized feasible range increases 1099.6% as the average temperature inside the tunnel rises from −2.5 °C to 5 °C; (2) increasing flowrate and lowering the temperature of the inlet fluid can yield a reduction in the optimal length of up to 29.2% and 64.3% separately; (3) a relatively sparse pipe arrangement can save cost without comprising the optimal length. This study presents a smart and efficient approach for designing the heat extraction section of the energy tunnel, which is promising in more complex conditions and capable of guiding practical applications.

Effects of ammonia on combustion of coal in stoichiometric premixed methane–air flames

NH3 has long been considered a promising alternative fuel·NH3 from renewables can be used for energy storage·NH3 is a zero-carbon molecule and can be burned directly and used as a hydrogen carrier. Compared with hydrocarbon fuels, NH3 has several drawbacks, such as an inferior flammability limit, flame temperature, and flame burning velocity, resulting in a lower reactivity rate and the production of pollutants.Therefore, cofiring coal with NH3 is an approach that has been growing in popularity. This study investigated the combustion of coal cofired with NH3 and conducted two-color pyrometry to measure the temperature profiles of coal particles in hybrid flames, that is, methane–coal–air and methane–NH3–coal–air premixed flames. The axial temperature distribution at the center of the flame was measured using two-color pyrometry and a thermocouple. The temperature values obtained were not identical but exhibited similar trends. The results indicated that the temperature at the origin significantly decreased upon ammonia addition, but as the measuring height increased, the final temperatures approached similarity.In addition, the emissions of pollutants such as CO and NOx were also measured. The results indicate that the addition of coal particles without ammonia gas leads to an increase in CO concentration due to the pyrolysis of the pulverized coal. However, there was no significant impact on NOx emissions.In contrast, the addition of coal particles under CH4 − NH3 gas combustion conditions results in a significant decrease in both CO and NOx concentrations. Specifically, under the 80 %CH4 + 20 %NH3 condition and with a coal particle feeding rate increasing from 0 to 0.24 g/min, there was a reduction of approximately 34% in CO concentration and 35% in NOx concentration.In order to confirm the coal consumption rate, coal particles were captured before and after flame sheet using a metal grid, and the particle projected area was determined based on scanning electron microscopy (SEM) images. These results provided evidence that the addition of NH3 to the CH4 − air flame enhances coal combustion, as indicated by a decrease in the particle shrinkage rate and sampling density.

Experimental characterization of TIAGO torch discharges: surface wave discharge behavior and (post-)discharge kinetics

The Torche à Injection Axial sur Guide d’Ondes source—better-known as the TIAGO torch—is a particular type of microwave-induced plasma that has become a focus of technological and scientific interest due to its outstanding features. Moreover, the TIAGO torch device arouses interest thanks to its remarkable performance in many challenging areas, such as green energy generation and graphene production by hydrocarbon decomposition. Although it has not been experimentally demonstrated to date, discharges generated by a TIAGO torch have been theoretically predicted to be surface wave discharges (SWDs), a kind of plasma leading the development of new materials. Therefore, deeper and fundamental research on this device is needed to optimize the implementation of plasma technology in these fields. In this study, the axial distribution of gas temperature, electron density and intensity of the main atomic and molecular emissions have been studied by optical emission spectroscopy when feeding the discharge with different input power values (200, 400 and 600 W). A complete axial characterization of both the dart and the plume regions is depicted and, according to the data obtained for the main plasma parameters, different regions can be identified, with the radiation zone being reported for the first time at atmospheric pressure. The kinetics of both the dart and the plume are discussed and an experimental verification of TIAGO torch behavior as a SWD is presented for the first time.

Experimental study on an open-cycle conical Hampson-type miniature Joule-Thomson cryocooler

Hampson-type miniature Joule–Thomson (J–T) cryocooler is widely used for the fast cooling of infrared detectors. In this work, a conical Hampson J-T cryocooler is designed and fabricated, and an experimental setup is built to test its performance. Accordingly, the cooling capacity, heat transfer coefficient, and efficiency of the cryocooler are analyzed based on the experimental cooling curves, the axial temperature distribution, the mass flow rate, and the pressure of the expansion chamber. The results showed that a minimum cooling temperature of 168 K with cooling capacity of 393.5mW can be attained by employing nitrogen gas as the working fluid at inlet pressure of 10 MPa. In addition, it was found that the axial temperature of the cold finger shell is distributed exponentially in the vertical direction. Also, the comprehensive heat transfer coefficient between the incoming flow and the backflow decreases gradually with the increase in the height. Due to the heat leakage, the heat transfer coefficient is less than 150 W/ (m2· K) and the efficiency of the cryocooler is around 80%. With the increase in the inlet pressure, the minimum stable operating temperature, cooling capacity, mass flow rate, and expansion chamber pressure of the cryocooler are found to increase. On the other hand, this will negatively affect the efficiency of the cryocooler.

Analysis of lead–bismuth eutectic-cooled solid reactor under flow blockage accident by 3D neutronics thermal-hydraulics coupling method

As the most common and serious accident in liquid metal-cooled reactors, the occurrence of a flow blockage accident may threaten the integrity of the cladding and the safety of the core. Therefore, the accurate prediction of fuel and cladding under blockage accidents is particularly important in reactor design and thermal–hydraulic analysis. This paper uses a three-dimensional neutronics thermal-hydraulics coupling method to analyze the blockage accident of a lead–bismuth-cooled solid reactor proposed by the Innovative Nuclear System Laboratory (INSL) of Shanghai Jiao Tong University. Based on the accurate and material models, the solid reactor was modeled, and 15 blockage accidents were carried out. The effects of the blockage's radial position, thickness and axial position on the fuel and cladding temperature were compared. Unlike the conventional open-channel blockage, the results of the closed-channel blockage accident analysis show that the thickness and axial position of the blockage has less influence on the maximum fuel and cladding temperatures but slightly affect the fuel and cladding axial temperature distribution. Meanwhile, the blockage accident in the closed channel is more serious, and the maximum temperature rise of fuel and cladding is higher, but both are lower than the limit value required by the design criteria.

Obtaining plasma parameters by Langmuir probes and optical emission spectroscopy in low-pressure DC plasma

The plasma environment in low-pressure systems allows coating different materials such as glasses, textiles, metals, etc. at the atomic level. Although vacuum coating is one of the best methods for thin film coating, the coating quality is closely affected by the spatial and temporal non-uniformities inside the reactor. Therefore it is quite important to determine the plasma properties within the chamber. The determination of plasma parameters such as electron temperature, electron excitation temperature, electron and ion densities can be realized using Langmuir probe systems, and by Optical Emission Spectroscopy (OES) by using Boltzmann plot method. Knowing such parameters can provide important information about specific reaction mechanisms, as well as it provides invaluable information that can increase reproducibility in various discharge process control in thin film coating. In this study, a homemade single Langmuir probe (s-LP) and a multiple Langmuir probe system (m-LP) were used to calculate electron temperature, electron density, saturation current, and plasma potential of the plasma at different pressures and at different voltages. One of the objectives of this work was to evaluate the electron temperature and ion density inside the plasma during a coating process. The second objective was to find the spatial change of electron temperature in the axial direction between cathode and anode by m-LP system including 8 independent tips. The last objective was to measure the axial plasma electron temperature distribution inside the vacuum chamber by using OES.

Numerical Study of Turbulent Swirling Diffusion Flame Under Lean and Rich Conditions Using Turbulence Realizable k-epsilon Model

ABSTRACT This work investigates numerically a non-premixed swirling flame in a coaxial burner with a radial fuel injection under lean and rich conditions of mixtures. The swirler is placed in the annular part of the burner. The fuel is injected radially through eight holes symmetrically distributed on the periphery of the central tube. All simulations are carried out using the ANSYS-Fluent CFD code. The turbulence is captured using the Reynolds Averaged Navier-Stokes approach. Chemistry/turbulence interaction is resolved using the Eddy Dissipation Model. Simulations are performed with a global equivalence ratio ranging from 0.5 to 1.3. Model validation is achieved by comparing computed results to our experimental data of Stereoscopic Particle Image Velocimetry obtained in the case of the stoichiometric regime. Good agreement between numerical results and experimental measurements is assigned. The central recirculation zone and the swirling jet region due to the presence of the swirl are well predicted by the simulations. The effect of the global equivalence ratio on the profile of axial velocity, temperature distributions and pollutant emissions (CO and NOx) is numerically studied. From dynamic point of view, the equivalence ratio modifies the mean axial velocity of the swirling diffusion flame. The increase of equivalence ratio destabilizes the flame by increasing the liftoff height. NO production decreases by the increasing of the equivalence ratio.