Preheat Temperature Research Articles

On the role of the preheat temperature in electron-beam powder bed fusion processed IN718

Process parameters optimization in additive manufacturing (AM) is usually required to unlock superior properties, and this is often facilitated by modeling. In electron beam powder bed fusion (E-PBF), the preheat temperature is an important parameter to be optimized as it significantly influences the microstructure and properties. Here we compare the effect of two preheat temperatures (1000 and 950°C, above and below δ-phase solvus temperature) on the microstructural evolution of E-PBF IN718 Ni-based superalloy. Using thermal and thermo-kinetic modeling, we predict microstructural changes and compare them with experimental findings. A decrease of only 50°C in the preheat temperature has a low impact on the solidification microstructure with a slight reduction in columnar grain width. In the solid-state, higher preheating causes intergranular δ-phase precipitation, contributing to a higher γ" precipitation potential, formation of co-precipitates, and higher hardness. The lower preheat temperature induces intergranular and intragranular δ-phase precipitation, reducing the γ" precipitation potential and hardness. The chemical composition of γ' and γ" is largely unaffected by the preheat temperature variation. These insights underscore the importance of preheat temperature optimization in microstructure design and property control during E-PBF.

Electron Beam Additive Manufacturing of SS316L with a Stochastic Scan Strategy: Microstructure, Texture Evolution, and Mechanical Properties

This study examines the microstructure, crystallographic texture evolution, and mechanical properties of stainless steel 316L fabricated through electron beam melting using a stochastic scan strategy at a preheat temperature of 1123 K. X-ray diffraction confirmed the presence of a pure austenitic phase in the fabricated material. Equiaxed cellular structures were observed in the center of the melt pool regions and elongated cellular structures observed at the melt pool overlap regions. A finite element-based numerical model was employed to estimate the thermal gradients and solidification rates within the melt pool of an electron beam spot. Microstructural analysis indicated a generation of columnar grains from the bottom to the top of the build owing to high thermal gradients. A crystallographic texture investigation showed a generation of strong <110> fiber texture along the build direction of the material and reported that the stress distributions within the melt pool led to a strong crystallographic texture driven by the stress evolution observed from thermokinetic computational modelling of the electron beam-melting process. Mechanical properties were assessed using profilometry-based indentation plastometry, demonstrating strain hardening at a high temperature of 773 K.

Multi‐aspect assessment and multi‐objective optimization of preheated tallow biodiesel‐diesel blend as alternate fuel in CI engine

AbstractThis study meticulously examined the impact of preheated tallow biodiesel on the performance and emission characteristics of a diesel engine. Employing a single‐cylinder, water‐cooled diesel engine configured with exhaust gas recirculation in this investigation, exhaust gas temperature (EGT) could be used to preheat the biodiesel, reducing its viscosity and density. This improvement in viscosity and density could enhance the injection process, which is often hindered by the higher density and viscosity of biodiesel compared with diesel fuel. The investigation achieved a peak preheat temperature of 70°C for the biodiesel, leading to notable improvements in brake thermal efficiency and brake power, particularly under high‐load conditions. A significant reduction in emissions was observed, with hydrocarbon and carbon monoxide levels decreasing by 46.87% and 50%, respectively, when using preheated biodiesel. To refine the engine's performance further, this study utilized response surface methodology (RSM) for the optimization of operational parameters, including injection timing, engine load, and biodiesel preheat temperatures. Optimal conditions were identified at an injection timing of 21° before top dead centre, a preheat temperature of 64°C, and an engine load of 45.45% for which output response was 18.68% brake thermal efficiency, 307°C EGT, 0.0247% vol. CO, 15.32 ppm hydrocarbons, and 131.37 ppm nitrogen oxides (NOx). The successful implementation of preheated tallow biodiesel signifies a crucial step forward in the pursuit of a more sustainable and efficient transportation industry. This advancement holds the promise of reducing reliance on traditional fossil fuels, thereby contributing to the global efforts towards achieving a more environmentally friendly energy landscape.

Effect of Temperature Control and Rotational and Traverse Speeds on the Mechanical Properties of Friction Stir-Welded Polypropylene Plates

In the present study, the effects of temperature and rotational and traverse speeds on the mechanical properties of polypropylene joints that are welded by friction stir welding using a non-rotational shoulder and a heat-assisted welding process is investigated. Tensile properties, microhardness measurements, microscopy observations, and thermal analysis are carried out in the present research to evaluate the effect of the welding parameters on the mechanical properties of welded joints. The experiments are conducted and analyzed by means of a central composite design using an analysis of variance (ANOVA). Variations in pre-heating temperature from 60 °C to 80 °C, rotational speed from 800 to 1500 rpm, and traverse speed from 20 mm/min to 100 mm/min are made for observations. A remarkable joint efficiency of 94% is achieved with joints that are free of discontinuities and defects. The fractured surfaces are observed to identify ductile and brittle zones. The crystallinity is measured, and a correlation between crystallinity and joint strength is discussed. The sample with highest efficiency shows 65% crystallinity and a ratio of 37.9% of ductile zone–total fractured area.

Study on properties of pre-alloy powder of TiNiHf high temperature shape memory alloy for additive manufacturing by preheating treatment

In this work, pre-alloyed powder high-temperature shape memory alloy (Ti30Ni50Hf20) for additive manufacturing was preheated at 300–800 °C and thermoscycled at 650 °C to examine the influence of preheating temperature and thermal cycle number on the phase composition and phase transformation behavior. The results showed that the H phase precipitation occurred in the matrix with the rising preheating temperature within 300–600 °C, and the phase transformation temperature of the pre-alloyed powders also increased. When the preheating temperature exceeded 600 °C, the H phase dissolved back into the matrix, and the phase transformation temperature decreased. A total of 50 thermal cycles were conducted on the pre-alloyed powders at 650 °C, and the phase transformation temperature and phase composition remained stable after cycling. It can be concluded that the preheating temperature greatly affected the phase composition and phase transformation behavior of Ti30Ni50Hf20 high-temperature shape memory alloy pre-alloyed powders, while the number of thermal cycles delivered a minor effect.

Study on the mechanical properties of PES-HmA samples printed by selective laser sintering under various pre-heating conditions

The purpose of this study is to investigate the influence of pre-heating characteristics on the mechanical properties and forming process of selective laser sintering (SLS) printed PES-HmA samples. An experimental setup with four heating tubes was designed to study the pre-heating temperature distribution on the powder bed. The pre-heating temperature distribution on the powder bed was captured using a thermal imaging camera. A method for evaluating pre-heating temperature distribution based on the average and standard deviation of surface temperature was proposed. The heating tube installation position was optimized using a response surface experiment study based on the temperature distribution evaluation. By optimizing the installation position of the tubes, the temperature distribution on the powder bed tends to become uniform. The effect of pre-heating temperature value and distribution on the mechanical properties of the SLS printed PES-HmA samples was also experimentally investigated. The cross sectional microstructure of the printed samples were examined by scanning electron microscope to analyze the layer formation process at different pre-heating temperature. By increasing the pre-heating temperature from 70°C to 100°C, the material diffusion at the layers interface was improved, which made the tensile strength of sample increased by 376%, and the flexural strength increased by 224%.

Design and performance analysis of a coupled burner for the Solid Oxide Fuel Cell system

The Solid Oxide Fuel Cell (SOFC) system is characterized by high energy conversion efficiency and low emissions. The energy supply and recovery of the SOFC system are facilitated through the ignition burner and the off-gas burner, respectively. This study proposes a coupled design of the ignition burner and the off-gas burner to reduce the burner volume, thereby enhancing the power density of the SOFC system. The ignition burner employs radially opposed jet combustion with fully premixed natural gas, while the off-gas burner uses swirl diffusion combustion with the anode off gas. When the premixed gas and lean anode off gas are unable to sustain the flame, catalytic combustion is initiated. Simulation and experiment methods are utilized to analyze the performance of the coupled burner in this paper. The results indicate that uniform mixing is achieved with a high swirl number (s1 = 2.6) for the premixed gas, and the maximum excess air coefficient for stable flame combustion at 400 °C is 2.47. As the temperature of the cathode off gas increases, the flameout boundary for the premixed gas gradually increases; conversely, with increasing burner power, the flameout boundary gradually decreases. The intersection cooling effect of mixed air and circumferential high-temperature flue gas is effective, and the flame does not exceed the tolerance temperature of the catalytic carrier. The diffusion combustion of anode off gas with a swirl number (s2 = 0.5) exhibits great gas mixing uniformity without a high-temperature core region. When transitioning from flame to catalytic combustion with premixed natural gas and anode off gas, there is a temperature lag of approximately 60 s. The isotropic cylindrical cordierite catalytic carrier with a 400 mesh and a coating of 60 g/ft3 Pt0.1Pd0.5 achieves stable catalytic combustion in an environment with preheated air temperatures ranging from 400 to 600 °C and H2 concentrations of 0.25–2.91 %.

Assessing the Effect of Specimen Preparation Methods on DSR Test Results of Bitumen Using Factorial Design Analysis.

A two-level three-factor factorial design experiment was conducted to study the influences of three critical specimen preparation parameters on the measurement results of bitumen by a dynamic shear rheometer (DSR). The investigated factors were (1) the pre-heating temperature (HT) for manufacturing the specimen, (2) the bonding temperature (BT) onto the rheometer, and (3) the trimming (Trim) operation for preparing the specimen after bonding. The analysed data were the measured shear modulus |G*|, phase angle δ, and the characteristic temperatures of bitumen's specific stiffness TX with corresponding phase angle δTX according to the European standard EN 14770:2023. Five types of bitumen were tested, including three penetration grades and two modified bitumen specimens (with polymer and wax additives). In addition, a repeatability evaluation of the test results was conducted. We found that the trimming operation for preparing the specimen has a noticeable impact when using smaller plates (PP08) for the DSR measurement. At higher test temperatures when using larger plates (PP25), the trimming operation does not significantly impact the measured parameters, in contrast to the HT and BT. Except for bitumen type 70/100, modified binders are more susceptible to variation in the analysed parameters than unmodified ones. The three-way interaction Trim:BT:HT tends to cause relatively little variation in measured data. Interactions between two factors Trim:BT, Trim:HT, and BT:HT contribute more to the fluctuation in δ value than in TX and |G*|. The variation employed in this study affects the test repeatability of wax-modified bitumen significantly; however, for unmodified binders the repeatability of TX and δTX are within 0.4-2.1 °C and 0.3-3.1°, respectively.

Synthesis of high purity Ti2AlC MAX phase by combustion method through thermal explosion mode: Optimization of process parameters & evaluation of microstructure

Obtaining high-purity MAX-phase powders is a challenging issue. Therefore, in this article, the effects of two key parameters, including mechanical activation time (1, 2, and 3 h), and preheating temperature (800 and 1000 °C) were investigated on the formation mechanism of Ti2AlC MAX phase using mechanically activated (assisted) self-propagating high-temperature synthesis (MA-SHS) combustion method through thermal explosion mode. For this aim, a powder mixture of titanium, aluminum, and carbon with a stoichiometry ratio of (2:1:1) was used. Differential thermal analysis (DTA) was carried out to evaluate the effect of mechanical activation and preheating temperature of the formation temperature of the target MAX phase. Subsequently, the microstructural, phase analysis, chemical composition, and determination of surface chemical states studies were carried out through scanning electron microscopy (SEM), X-ray energy distribution spectroscopy (EDS) transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and X-ray photoelectric spectroscopy (XPS), respectively. DTA results illustrated that applying mechanical activation alters the formation temperature, which leads to an increase in the purity of the MAX phase. The quantitative measurements were carried out using the Rietveld method to determine the purity of the achieved MAX phase. The results indicated that samples subjected to 2 h of mechanical activation at a preheat temperature of 1000 °C exhibited to contain 96.1 % of Ti2AlC MAX phase, which is the highest value among other specimens and the lowest amount of secondary and oxide phases (3.9 % of TiC) during the combustion synthesis process compared to other samples.

Interpass temperature impact on bead geometry of mild steel in wire-arc additive manufacturing

In wire-arc additive manufacturing (WAAM), melt pool dynamics produce variations in bead geometry that create undesired part geometries and can also lead to material defects. In the current state of the art, reducing melt pool and bead variation is still an aspect of WAAM that is underdeveloped. Several factors influence the bead geometry including the type of material that is being deposited and process inputs. In this study, ER70S-3 mild steel was deposited onto steel build plates using a cold metal transfer (CMT) deposition process. Varying plate preheat surface temperatures were used from ambient temperature to 300 °C using different welding travel speeds. To control build plate surface temperature, a preheat stage was designed and implemented to simulate different interpass temperatures. Beads were deposited and subsequently measured to determine their geometric properties such as bead height and bead width. Initial results indicate that as the preheat temperature increases, resulting bead height decreases, bead height variation decreases, and bead width increases. Initial microstructural data also indicates that as preheat temperature increases, the microstructure becomes more equiaxed with decreasing grain sizes.

A Modelling Framework for Rapid Evaluation of Speed Limitations during Extrusion of Aluminium Profiles

Hot tearing is a well-known limitation when trying to maximize the throughput rate in aluminium extrusion. In the present work an analytical modelling framework is presented which can be used to predict the maximum extrusion speed that can be applied in production without formation of this type of surface defect. The modelling framework allows almost instantaneous estimates on the resulting productivity in terms of maximum extrusion speed. This is obtained by developing an analytical model for the maximum temperature at the die exit which incorporate the effect of alloy composition and billet processing. The results are consolidated into extrusion limit diagrams, mapping the maximum allowable extrusion speed as a function of billet pre-heat temperature, alloy composition, and homogenisation heat treatment. The calculated temperatures and extrusion limit diagrams obtained from the analytical model are compared with measured temperatures and critical extrusion speeds from extrusion tests of various 6xxx series alloys for a simple rod-shaped geometry. The comparisons indicate that the presented modelling approach gives sufficiently accurate predictions for future application in optimisation of alloy composition and process parameters in extrusion of profiles.

Mechanism study on rheological response of thermally pretreated waxy crude oil

Pre-heating treatment significantly influences the low-temperature flow characteristics of waxy crude oil, yet its underlying mechanism warrants further investigation. This study explores the effects of pre-heating temperatures (60–110 °C) on the rheological characteristics of waxy crude oil from Nanyang using 1H NMR, DSC, Microscopic Observation, and Rheological Property Test. Findings reveal that asphaltenes increasingly dissolve at the pre-heating temperature of 70 °C, improving their capacity to act as nucleation sites for wax crystals. Consequently, the wax appearance temperature (WAT) increases. Meanwhile, the rheological parameters of the crude oil decrease and wax crystals exhibit smaller and tighter rod-like structures. Further growing the pre-heating temperature to 80 °C induces a comprehensive effect: alterations in asphaltene polarity, hindrance of asphaltene aggregation by alkyl side chains, and self-aggregation of alkyl side chains. This results in decreased WAT, along with the lowest rheological parameter values, with wax crystals appearing as the smallest and tightest dot-like shapes. At 80 °C, the optimal ratio between asphaltene polarity and alkyl side chain characteristics promotes strong nucleation and co-crystallization between asphaltene and wax crystals, maximizing asphaltene's ability to enhance the crude oil's low-temperature flowability. However, as the pre-heating temperature continues to rise, WAT decreases slightly and the rheological response starts to deteriorate.

Optimization of autothermal reforming of ultrasonic methanol sprays over Cu/ZnO catalyst for hydrogen production via a statistical approach

Autothermal reforming (ATR) is a highly efficient process for hydrogen production. This study uses the Taguchi method to optimize the hydrogen production from methanol via the ATR process. The Cu/ZnO particle is used as the catalyst, and an ultrasonic spray system is used to generate aqueous methanol sprays for ATR. A Taguchi L9 orthogonal array is used to assess the effects of preheating temperature, oxygen/carbon (O2/C) ratio, steam/carbon (S/C) ratio, and gas hourly space velocity (GHSV) on H2 yield. The results show that the O2/C ratio has the most significant influence on the objective function, H2 yield, followed by preheating temperature, S/C ratio, and GHSV, with the most negligible impact. The optimal conditions for maximizing the H2 yield from signal/noise ratio analysis are a preheating temperature of 350 °C, an O2/C ratio of 0.65, an S/C ratio of 1.5, and a GHSV of 7000 h−1. The analysis of variance (ANOVA) indicates that the model has a good fit with a high R2 value (=0.9735). The contribution to H2 yield is 40.22 % by the O2/C ratio, 37.80 % by the preheating temperature,19.34 % by the S/C ratio, and 2.54 % by the GHSV. The H2 yields from ATR, steam reforming, and partial oxidation are also compared. The results indicate that ATR is the optimal choice for producing hydrogen from methanol while maintaining the proper reaction temperature range without generating extra energy.

Turbulent Burning Velocity of High Hydrogen Flames

Abstract The turbulent burning velocity (ST) is one of the most important combustion properties controlling combustor operability limits, directly influencing blowoff, flashback, and combustion instabilities. Hydrogen has particularly significant influences on the turbulent flame speed. This paper presents new H2/CH4 data of high pressure, high hydrogen turbulent burning velocities. The datasets were designed to address fundamental questions as well as provide engineering/design relevant insights. This paper presents new scaling analysis of fuel composition, pressure, and preheat temperature effects on turbulent burning velocity. We also discuss the importance of considering what is being held constant (temperature, flame speed, Reynolds number, etc.) when one is analyzing these sensitivities. Data show that hydrogen fraction and pressure cause an increase in turbulent flame speed; whether quantified as raw ST,GC or normalized as ST,GC/SL,0 or ST,GC/SL,max (where SL,0 and SL,max are the unstretched and stretched laminar flame speed, respectively). We also propose that observed increases in ST,GC with pressure are due to increases in Reynolds number and not a kinetics/stretch sensitivity effect. With increasing preheat temperature, ST,GC increases while its normalized value (ST,GC/SL,0 and ST,GC/SL,max) can either increase or decrease, depending upon fuel composition. We also show how these sensitivities vary, depending on whether these comparisons are made at constant raw turbulence intensity urms or at constant normalized urms/SL,0 or urms/SL,max.

Mechanical Properties of Pb–0.7%Sn–0.08%Ca Positive Grid Alloy for Lead-Acid Batteries

The effects of casting procedure and ageing time on the tensile properties of Pb–0.7%Sn–0.08%Ca positive grid alloy for lead-acid batteries were investigated. As a preheating temperature of a mold during casting increases from 40°C to 170°C, ultimate tensile strength decreases, but elongation increases due to the changes in the grain structure of the alloy. Prolongation of ageing time up to 32 days causes the increase in strength and decrease in elongation, with higher ageing rate observed during first 15 days.

Effect of Back Plate Preheating Assistance System and Deep Rolling Process on Microstructure Defects and Axial Force Reduction of Friction Stir Welded AA6061 Joint.

This study investigates the effects of a back plate preheating assistance system and deep rolling (DR) on axial force and tunnel defects during friction stir welding (FSW). Different preheating configurations-advancing side (AS), retreating side (RS), and both sides-were examined to evaluate their impact on axial force reduction, temperature distribution, and defect minimization. Axial force measurements were taken using a dynamometer, and temperature histories were recorded with a thermal camera. The results demonstrate that a preheating temperature of 200 °C is optimal, reducing axial force by 30.24% and enhancing material flow. This temperature also facilitated deeper tool penetration, especially when preheating was applied to both sides. Preheating on the AS resulted in the smallest tunnel defects, reducing defect size by 80.15% on the RS and 96.91% on the AS compared to the non-preheated condition. While DR further reduced tunnel defects, its effectiveness was limited by the proximity of defects to the surface. These findings offer significant insights for improving the FSW process.

Regulating heat-induced fibrous whey protein-wheat starch composite emulsion gels as dysphagia food by preheating temperature: Insights from protein-starch interactions

Heat-induced processes significantly affect the gel behavior of protein and starch, but the mechanism by which preheating temperature affects the quality characteristics of the gel is unclear. Herein, to explore the feasibility of developing texture-modified foods based on proteins, carbohydrates and lipids, the effects of preheating temperatures (40–80 °C) on the texture and starch digestibility of fibrous whey protein (FWP)-wheat starch composite emulsion gels (CEGs) under two-step heating condition were investigated. The rheological and texture properties, protein-starch interactions and microstructure of CEGs were characterized. The results showed that preheating temperature synchronously regulated the texture and starch digestibility of heat-induced CEGs. When preheating temperature is below 60 °C, two-step heated CEGs showed bicontinuous networks with harder texture, similar as one-step heated gels. While temperature exceeds 60 °C, preheating altered FWP conformation and promoted protein-starch interactions, forming protein-starch complexes or protein aggregates. This changed protein distribution and disrupted bicontinuous network, forming more hydrophobic interaction, yielding a soft-textured CEGs. In this case, SDS content increased and RS content decreased. Notably, two-step heating process with high preheating temperature (>60 °C) is universal for softening fibrous whey protein-starch-based composite gels. This study enhances the understanding of traditional heat-induced protein-starch gelation processes and provides a simple and feasible method for developing texture-modified foods.

New chronology evidence of prehistoric human activities indicated by pottery luminescence dating in the humid subtropical mountains of South China

The age of prehistoric human sites serves as a fundamental basis for studying the relationship between human activities and landscape changes in the humid subtropical mountains of South China. The presence of pottery in these archaeological sites is widespread and offers a valuable resource for precise dating purposes. The Longtoushan (LTS) site, located in the northern mountains of Fujian Province, contains a rich variety of pottery types from various periods, representing a rare multi-period stratigraphic overlap in this area and playing a crucial role in constructing the cultural sequence and lineage of prehistoric and ancient times in this region. In this study, we employed thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques to establish the age of pottery samples collected from the LTS site situated in the upper Minjiang River region of southeast China for the first time, while also comparing our findings with other dating methods to construct a chronological framework for the site. The results showed that: (1) The samples analyzed in this study can be classified according to the peak strength of 325 °C TL signal at natural and regenerative doses of quartz. Samples with weak TL signal at 325 °C (type II samples) showed high recuperation and equivalent dose underestimation at a low preheat temperature (220 °C) in OSL test. (2) Conventional SAR procedures employed for type I samples are not suitable for type II samples. Type II samples require additional OSL stimulation towards the end of the cycle and an extended stimulation duration. (3) The application of various dating methods has revealed that the LTS site represents a long-term settlement in the humid subtropical mountains of South China, commencing around 4.6–4.4 thousand years ago (ka). Specifically, the dating of pottery pieces from kiln sites and tombs in the late Neolithic period provides a specific temporal reference for further understanding of prehistoric human culture and production behavior in the humid mountains of Fujian.

Low-NOx thermal plasma torches: A renewable heat source for the electrified process industry

Industrial thermal plasma torches can heat a gas up to 5000–20,000 K, i.e., well above the temperature needed to replace the heat generated from the combustion of traditional fossil fuels (e.g., coal, oil, and natural gas) in large-scale process industry furnaces producing construction materials (e.g., iron, steel, lime, and cement). However, there is a risk for significant NOx emissions when air or N2 are used as plasma-forming gas since the temperature somewhere in the furnace always will be higher compared to the threshold NOx formation temperature of ∼1800 K. Torch NOx forms inside the high temperature region of the plasma torch (>5000 K) when air is used as gas. Process NOx forms instead when the hot gas (when air or nitrogen is used as plasma forming gas) from the plasma torch mixes with process air downstream the torch. By analysing the complex chemistry of both the torch- and process NOx formation with thermodynamic equilibrium and one-dimensional chemical kinetic calculations it was shown that adding H2 to the plasma-forming N2 gas significantly reduces the NOx emissions with more than 90 %. Verifying experiments with air, pure N2, and mixtures of H2 and N2 as plasma-forming gas were performed in a laboratory scale insulated laboratory furnace with different pre-heating temperatures of process air (293, 673, and 1073 K) which the plasma gas mixes with downstream the torch. Depending on the pre-heating temperature the NOx emissions were between 12,000–14,000 mg NO2/MJfuel when air was used as plasma forming gas. Substantial NOx emission reduction occurs both when N2 replaces air, where the NOx emissions was in the span of 8000–11,500 mg NO2/MJfuel and furthermore when H2 was mixed into the N2 gas stream. For the highest degree of H2 mixing (28.6 vol-%), the NOx emissions were between 450–1700 mg NO2/MJfuel depending on the pre-heat temperature of the process air, i.e., a reduction of 88–96 % and 85–94 %, respectively when air or N2 was used as plasma forming gas. The measured NOx emissions are then of the same order of magnitude as would be expected from the combustion of traditional fuels (coal, oil, biomass and pure H2). Finally, by analysing the aerodynamics in an axisymmetric furnace with an experimentally validated computational fluid dynamics (CFD) model using reduced chemistry for the NOx formation (19 species and 70 reactions), further guidelines into the process of NOx reduction from thermal plasma torches are given.

Soot volume fraction measurements in aero-engine model combustor outlet using two-color laser-induced incandescence

Quantitative measurement of Soot Volume Fraction (SVF) is an essential prerequisite for controlling soot particle emissions from aero-engine combustors. As an in-situ and non-intrusive optical diagnostic technique, Laser-Induced Incandescence (LII) has been increasingly applied for soot concentration quantification in various combustion environments such as laminar flame, vehicle exhaust, internal combustion chamber as well as aero-engine combustor. In this work, we experimentally measured the spatial and temporal distribution of SVF using two-color LII technique at the outlet of a single-sector dual-swirl aero-engine model combustor. The effect of inlet pressure and air preheat temperature on the SVF distribution was separately investigated within a pressure range of 241–425 kPa and a temperature range of 292–500 K. The results show that soot production increases with the inlet pressure but generally decreases with the air preheat temperature. Qualitative analysis was provided to explain the above results of parametric studies. The LII experiments were also conducted under 3 designed conditions to evaluate soot emission under practical operations. Particularly, weak soot emission was detected at the outlet under the idle condition. Our experimental results provide a valuable benchmark for evaluating soot emission in the exhaust plume of this aero-engine combustor during practical operations.