Xiaohan Wang

Chinese Academy of Sciences | CAS · Guangzhou Institute of Energy Conversion

A thermal cracking experimental equipment of hydrocarbon fuels was built to study n-heptane pyrolysis and the effect of reaction conditions on this reaction process. The main species were measured and the change rules were analyzed on the range of temperature 873–1073 K and pressure 0.1–3.5 MPa. The total content of alkenes products was more than a...

Based on the optimization of the recently proposed gas phase mechanism for n-heptane pyrolysis, mechanisms for polycyclic aromatic hydrocarbon (PAH) formation and a detailed wall surface reaction, a basic gaseous pyrolysis mechanism with 1127 steps and a simplified surface reaction mechanism with 34 steps were developed, respectively. After perform...

A model was established to describe the effects of inorganic matter on the char-CO2 gasification reactivity. The effects of seven inorganic elements on the char-CO2 reactivity were considered: K, Na, Ca, Mg and Fe, which play a catalytic role, and Si and Al, which play an inhibitory role. A catalytic/inhibitory index factor model and a saturated ca...

The chemical catalytic performance of functional ceramics materials of rare earth is of great technological and scientific significance to actively regulate the flame-wall interaction in high-temperature combustion. The premixed methane-air flames in a slot burner with different wall materials were characterized by OH-PLIF technique to gain an insi...

The effects of channel curvature on the flame propagation are examined for premixed flames in micro channels. Previous studies have shown that curved channels can enhance the flame stretching, which can significantly increase the flame propagation speed. In this study, the effect of flame stretching was excluded by the narrow channel limit in order...

The present study investigates the combustion performance of pure ammonia in a stratified vortex-tube reactive flow (SVRF) concerning stability limits, flame topology, pressure fluctuations, and emissions. The results demonstrate that the SVRF enables efficient and stable combustion of ammonia, characterized by uniform flame topology, low NO emissi...

The combustion intensification mechanism was revealed in a stratified vortex-tube combustor. The results show that a triple-flame structure is formed in this combustor and the peak heat release is located exactly at the triple-point position. The peak heat release rates in the five selected representative cases studied in this paper are all over [F...

Technically, using catalytically active coatings regulate flame-wall interactions to enhance flame stability in small-scale burners, such as the common ZrO 2-based ceramics with doping CeO 2 which benefit to improve the high-temperature mobility and reactivity of lattice oxygen as an oxygen source to promote gas phase combustion. Probing by OH-PLIF...

Sewage sludge is a major by-product of wastewater treatment, and its unfavorable properties are frequently a key restriction of disposal technologies, resulting in high costs and ineffective waste management. Smoldering combustion is a new technique for disposing of organic solid waste with high moisture content, which efficiently recovers energy w...

Aerodynamic and thermo-acoustic stability were systematically analyzed to reveal the underlying cause of the super-steady performance found in a strong rotating reactive flow, which is achieved using a stratified vortex-tube combustor (SVC) employing methanol as fuel. Results show that the SVC possesses a wide stability limit and weak pressure fluc...

The hydrogen-enrichment combustion performance was investigated numerically by employing methane mixed with different volume proportions of hydrogen, wherein a vortex-tube combustor was employed to achieve a steady combustion process. Results show that this combustion technique indicates good adaptability to hydrogen-enrichment combustion together...

An experimental study on flame acceleration (FA) of hydrogen–air premixed gas in a millimeter-scale Archimedean spiral channel is presented in this paper. Experiments were performed in a transparent rectangular cross-section channel and the flames were recorded by high-speed photography. The flame propagation characteristics under different equival...

In this work, an ultra-steady combustion technique was attempted to achieve fuel adaptability combustion. The combustion performances of five representative gaseous fuels in a stratified vortex-tube combustor were investigated in terms of the stability limit, pressure fluctuation, and flame topology. Results show that the lean stability limit of th...

The objective of this study is to investigate the effects of inorganic element catalysis and basic fuel properties of sewage sludge on pyrolysis kinetics and self-sustained smoldering characteristics. The sludge pyrolysis process was explored by thermogravimetric and iso-conversion methods, and it was found that the pyrolysis process can be divided...

A kinetic model of char-CO2 gasification reaction with the influence of inorganic elements was established based on gas-solid simple collision theory. In the modeling process, the effects of the content of seven inorganic elements, the catalytic/inhibitory factor, and the fully catalytic ratio of single inorganic element on the char-CO2 reactivity...

The objective of this study is to investigate the effects of inorganic element catalysis and basic fuel properties of sewage sludge on pyrolysis kinetics and self-sustained smoldering characteristics. The sludge pyrolysis process was explored by thermogravimetric and iso-conversion methods, and it was found that the pyrolysis process can be divided...

Methylcyclohexane (MCH) and n-heptane (nC7) were used to perform experimental studies in high-temperature oxidation pretreated STS304 reactor (ϕ2 × 0.5 × 1000 mm) at 873–1073 K, 1.0 MPa, and 1.0 mL/min feed rate. The heat sinks of the two fuels were calculated based on the conversion and product distribution. MCH was found to have difficulty in ach...

The flame propagation processes involving deflagration-to-detonation transition (DDT) and detonation propagation in a novel millimetre-scale spiral channel (MSDC) are studied experimentally. The channel is of 3.0 mm in width and 5.2 m in length, embedded in a stainless-steel plate. In particular, a tiny gap of 0.02-mm width is reserved between the...

In this study, a theoretical model of biomass char gasification reactivity was developed, focusing on the catalytic effect of inorganic elements on the char gasification process. A comparison with previous research results shows that the catalytic ability of K in a fixed bed reactor is stronger than that of Ca, while the catalytic ability of Ca in...

The laminar burning velocities (LBVs) of n-decane/toluene/air mixtures were measured at elevated temperatures using externally heated diverging channel (EHDC) method. The effects of initial temperature (up to 650 K), toluene blending ratio (RC7H8 = 0 to 1.0 by liquid volume) and equivalence ratio (ϕ = 0.6 to 1.4) on the LBVs of n-decane/toluene/air...

In order to study the new cracking process characteristics of hydrocarbon feedstock to light olefins by direct flue gas heating, the pyrolysis experiments of n-heptane in CO2 and H2O atmosphere were performed in pretreated STS316L flow reactor (ϕ10 mm × 2.5 mm × 700 mm) at a temperature range of 1073–1373 K, pressure range of 0.1–1.0 MPa. By changi...

Four different types of solid waste samples were selected for pyrolysis experiments to explore the distribution law of solid，liquid，and gas products under the influences of different pyrolysis temperature，residence time，carrier gas flow and heating rate. Based on the back propagation(BP)neural network principle and the Matlab neural network toolbox...

The paper revealed the in-depth stabilization mechanisms of a novel vortex-tube combustion technique by using ethanol as fuel, which is implemented by a stratified vortex-tube combustor (SVC). The stability properties of the SVC are investigated, showing that the SVC has a wide stability limit and low-pressure fluctuation amplitudes with a uniform...

Wall coating modification has been a potential solution to organize the combustion process in space-constrained system. For this purpose, CeO2 doping effects on the flame stability of premixed methane/air mixtures confined within an adjustable-gap narrow channel with coating ZrO2-based ceramics are experimentally investigated. A series of character...

The effect of wall thickness on the combustion characteristics of nonpremixed hydrogen micro-jet flames was studied by two-dimensional numerical computation with a detailed reaction kinetics for the development of hydrogen micro-burner. The hydrogen jet diffusion flames achieved by micro-tubes with the same inner diameter and length but different w...

The combustion characteristics of laminar non-premixed CH 4 jet flame in an O 2 /CO 2 coflows with different oxygen mole fractions were studied experimentally. The flame heights at different oxygen concentrations and fuel jet velocity were obtained. The experimental observation shows that the luminosity of the CH 4 jet flame in O 2 /CO 2 coflow is...

From the perspective of the thermal/chemical performance management of a slot burner, three kinds of blended coatings with the low thermal conductivity and certain chemical activities, including 30wt.%Y2O3/ZrO2, 30wt.%MgO/ZrO2 and 30wt.%Al2O3/ZrO2, were prepared on stainless steel walls plated by atmospheric plasma spraying. The effects of coating...

This study was performed to analyse the adaptability of the self-developed char reactivity model and reveal the influence of preparation conditions on the char gasification reactivity. Firstly, six coal samples were selected for the step-by-step extraction of the metal elements. The forms of K elements in the different coal samples were quite diffe...

Coke deposition is considered a challenging problem during hydrocarbon pyrolysis. To get more insights into pyrolysis coking characteristics in the regenerative cooling channels, the unsteady-state experiments of n-heptane were performed in a 2.0 mm (internal diameter) passivated STS304 tube at 873–1073 K and 1.0 MPa with a feeding flow rate of 1.0...

A miniature constant-volume chamber setup was utilized to carry out experimental study of ignition and combustion characteristics of injected n-butane/air mixtures. Results indicate that the flame of the injected n-butane/air mixture forms at the hot wire surface and then spreads outwards. In the following stage，the injected n-butane/air mixtures a...

Palladium encapsulated in zeolite is a promising kind of catalysts for the removal of trace methane emissions due to their unique mass transfer channel and high thermal stability as well as good application prospects. Herein, well-dispersed PdO nanoparticles with suitable surface chemical state are in situ confined in Beta through seed-directed and...

In order to develop a burner with uniform temperature field, the combustion characteristics and thermal performance of partially premixed methane/air jet flames were experimentally studied by using micro jet array burners. The circular tubes of 1.0-mm inner diameter and 1.5-mm outer diameter were used as nozzles. The effects of nozzle spacing and e...

The oxygen-deficient combustion characteristics of methane in a localized stratified vortex-tube combustor (LSVC) are studied by diluting combustion air with nitrogen. The influences of oxygen mole fraction (0.13 ~ 0.21) on flame configuration, combustion stability, combustion efficiency, and NOx emission characteristics are experimental investigat...

This paper presents a novel method to accelerate flame propagation and transition to detonation in a coiled channel. The objective is to bring to light the basic understanding of the phenomenon and to show its potential in the fields of highly efficient combustion or propulsion. It was found that the flame evolution in the coiled channel is signifi...

As a clean gaseous fuel, methane (the main constituent of natural gas) has been widely used in the lives of residents and industrial processes. The oxy-fuel combustion technology for methane/carbon dioxide is an effective way to reduce the pollutant emissions of NOx, which is also beneficial to the capture of carbon dioxide. Herein, the stretch ext...

Four solid wastes including sludge, watermelon rind, corncob, and eucalyptus and their demineralized samples were selected to conduct pyrolysis experiments under different experimental conditions, including temperature, residence time, carrier gas flow rate, and heating rate, respectively. The co‐pyrolysis experiment was carried out after mixing di...

The premixed flame propagation with conductive heat loss in millimeter-scale narrow closed cells of different gap widths is investigated experimentally and numerically. The flame evolution is observed in a disc-shaped cell of which the width is varied from 2.0 mm to 5.0 mm. A non-monotonic relation between the flame propagation velocity and the gap...

The pyrolysis experiments of n-heptane in the CO2/H2O atmosphere were carried out in a millimeter-sized tube reactor. Mass yields and molar concentrations of gaseous products, including C2H4, C3H6, H2, CO, CH4, and C2H6, were obtained at a temperature range of 1073−1373 K, and atmospheric pressure. The pyrolysis characteristics of n-heptane under d...

A new quasi-direct numerical simulation (q-DNS) solver named combustionFoam, capable of simulating reacting flows at arbitrary Mach number with a detailed chemical reaction mechanism, has been developed. This solver is implemented based on reactingFoam-solver from OpenFOAM-v7. The main improvements are a mixture-averaged formula transport model and...

In this work, the structural function of char gasification is modelled theoretically. Considering that different components will have different pore characteristics after pyrolysis, char is divided into different micro-structures according to its corresponding components, and then a structural equation is constructed to realize the theoretical calc...

h i g h l i g h t s Quenching limits of small-scale H 2 diffusion flames are measured by using OH-PLIF. Quenching limits of the H 2 flames are obtained by 2-D numerical computation. The near-quenching small-scale H 2 flames have similar combustion characteristics. The conductive heat loss is the primary reason for the quenching of small H 2 flame....

The combustion of AC 10 H 20 droplets was investigated to explore the combustion performance of liquid fuels in localized stratified vortex-tube combustor (LSVC). The evaporation ratio, flame structure, stability limit, heat loss, and combustion efficiency in the LSVC were investigated under various equivalence ratios and fuel mass fluxes numerical...

Experimental study on the combustion characteristics of CH 4 /CO 2 non-premixed jet flames in a coflow air at normal and elevated temperatures was conducted for the development of biogas-fueled regen-erative burner. The CH 4 /N 2 non-premixed jet flame was also investigated for comparison. The laminar flame height, lift-off height and blow-out limi...

The liftoff height and blowout limit of CH4/CO2 non-premixed jet flames in co-flow air were investigated experimentally. The temperatures of co-flow air were set at 300 K and 600 K. The CH4/N2 non-premixed jet flames were also studied for the comparison. The premixed flame model was employed in analyzing flame liftoff heights and blowout velocities...

A novel vortex-tube combustor with axial fuel injection for NOx reduction was proposed to overcome the instability of ultra-lean combustion. The stability limit, flame configuration, NOx and CO emissions, and flame structure were investigated experimentally under various global equivalence ratios and fuel flow rates. The mechanisms of NOx emission...

In order to overcome the instability of ultra-lean combustion, a novel vortex-tube combustor with axial fuel injection was proposed. The stability limit, flame configuration, NOx emissions, and burn-off rate of the combustor were investigated experimentally under various global equivalence ratios (φg) and fuel flow rates (qf). Results show that the...

The stabilization performance and mechanisms in a diffusion‐like vortex‐tube combustor is investigated for oxygen‐enriched combustion. The stability limit, flame configuration, and pressure fluctuation are investigated under various conditions. Results show that a diffusion‐like flame structure is established in the combustor and the nonpremixed pe...

The operating limit and pressure fluctuations of a localized stratified vortex-tube combustor (LSVC) are investigated experimentally by taking methane as fuel at the inlet temperature of 300 K and the combustor pressure of 1 atm over a range of equivalence ratios (0.1-1.0). The combustion modes are distinguished according to the properties of press...

The combustion characteristics in a localized stratified tubular flame burner (LSTFB) were experimentally studied under lean conditions. The stability limit and pressure fluctuation were obtained under various global equivalence ratios and fuel flow rates. The mechanisms driving the combustion instability were analyzed with the combination of numer...

A new skeletal mechanism of n-butane is developed for describing its ignition and combustion characteristics applicable over a wide range of conditions: initial temperature 690–1430 K, pressure 1–30 atm, and equivalence ratio 0.5–2.0. Starting with a detailed chemical reaction kinetic model of 230 species and 1328 reactions (Healy et al., Combust....

Experimental studies on premixed flame propagation characteristics in a sub-millimeter-scale closed chamber are performed. Propane/air mixtures are ignited in the center of the visualized chamber and the subsequent flame front evolution process is recorded. The effects of the gap size of the chamber and the initial pressure of the mixture on the fl...

Flame propagation pictures of a propane/air mixture are captured by a high-speed camera in a visualized constant volume combustion chamber with a diameter of 150 mm, a parallel plate height of H = 1.45 mm, and an initial pressure of P0 = 1.25 ~ 3.00 bar, in the range of flammable equivalence ratios. The results show that when H of the combustion ch...

The extinction characteristics and lean fuel limits of methane oxy-fuel diffusion flames with oxygen mole fractions of 0.35 and 0.4 were numerically studied by using two different radiation models, namely optically thin radiation model (OTM) and discrete ordinates method (DOM). Experimental studies on extinction limits of the oxy-fuel diffusion fla...

Aimed to intensify the ignition and combustion process of n‐butane fuel in micro internal combustion (IC) engines, ignition delay characteristics of n‐butane/air mixtures with tert‐butyl hydroperoxide (TBHP) addition ratios below 10% were investigated numerically by CHEMKIN‐PRO software. Results show that ignition delay times of n‐butane can be sho...

Experimental and computational results on the combustion performances and their formation mechanisms were presented and compared in two types of tubular flame burners by using methane as fuel. Results corroborate that the localized stratified tubular flame burner (LSSTFB) can achieve a large stability limit as a consequence of the edge-like flame s...

To improve the lifetime and the flame stability of combustion-based micro devices, two coating materials (AlCrN and alumina)are deposited on STS 304 substrate to investigate the interactions between the premixed n-butane/air flame and the solid walls heated to different temperatures in a slit burner. The flame-wall interaction is characterized by t...

An OpenFOAM based turbulence combustion solver with flamelet generated manifolds (FGMs) is presented in this paper. A series of flamelets, representative for turbulent flames, are calculated first by a one-dimensional (1D) detailed chemistry solver with the consideration of both transport and stretch/curvature contributions. The flame structure is...

A three-dimensional numerical simulation of a localized stratified tubular flame burner is carried out by using propane as fuel. The characteristics of the flow field, species distribution, flame structure, and stability limit are investigated. Results show that in the cold flow field, a specific distribution of species is formed due to the unique...

The laminar flame propagation in narrow confined disc-shape chambers of millimeter scale is investigated, concerning the flame front displacement speed and the influences from the changes of the gap width and radius. An asymptotic analysis treating the flame front as a discontinuity successfully predicts the velocity profiles of the flame front and...