Xuecheng Wu

• PhD
• Faculty Member at Zhejiang University

The aluminum agglomerate surfaces serve as the essential interfaces for heat and mass transfer processes during combustion, with the attached oxide cap exerting a significant effect on the asymmetrical spatial distribution of agglomerate physical properties. Therefore, understanding the surface characterization and its dynamic evolution during alum...

The study of flow field characteristics inside the tip clearance is essential for understanding tip leakage flow (TLF) generation mechanisms. This paper investigates the TLF flow field in a single-stage axial compressor using a particle image velocimetry visualization system, alongside proper orthogonal decomposition and omega vortex identification...

Flow field visualization techniques, e.g., schlieren and shadowgraphy, are indispensable in fluid mechanics research and application. In this paper, we present a novel technique, named holographic focusing schlieren imaging (HFSI), which takes only a single-camera and single-shot configuration to achieve three-dimensional (3D) flow visualization. T...

Droplet temperature measurement is critically required in the research of icing cloud field, providing empirical data and optimization guidance for models on heat and mass transfer. Rainbow refractometry specializes in online measurement of droplet temperature through refractive index, yet its applications in the cloud field remain challenging. To...

An instrument for characterizing icing cloud particles in wind tunnels is critically required to enhance the understanding of aircraft icing mechanisms. Moreover, measuring multiscale and multiphase icing cloud particles presents significant challenges, particularly under extreme environmental conditions. This work elucidates the development and va...

Atomization of low-temperature fuel is encountered in extreme operating conditions of liquid propulsion systems such as cold start and high-altitude relight for aeroengines. Fuel temperature has a great impact on airblast spray characteristics by influencing fuel viscosity and thus the gas–liquid interaction, which raises the demand to clarify the...

Mandatory safety devices, prevalent in lithium-ion batteries (LIBs), enable current interrupt device (CID)-and vent-activated power-off protection by sensing the electrochemical gas production boost triggered by thermal runaway (TR). For an in-depth understanding of the early warning of safety devices, the thermodynamic and multiphase flow behaviou...

The Letter delves into an approach to holographic image denoising, drawing inspiration from the generative paradigm. It introduces a conditional diffusion model framework that effectively suppresses twin-image noises and speckle noises in dense particle fields with a large depth of field (DOF). Specific training and inference configurations are met...

The ice crystal icing in aero-engines poses a significant threat to aircraft flight safety, and investigating the correlation between ice crystal size and velocity in icing wind tunnels is essential for correlating ground tests with flight conditions. In this paper, a digital holographic particle tracking velocimetry system is developed and integra...

The burning aluminum droplets in composite solid propellants generated from merging and micro-explosion present complicated oscillations. It is essential to characterize this oscillatory process, while it is challenging for the oscillation frequency ranging from several to tens of kHz in a micron-scale region. The oscillation behaviors of micron-si...

Pyrolysis kinetics were used in this study to analyze the pore formation mechanism of coal activated with KOH. Experimental derivative thermogravimetry (DTG) curves were fitted using Achar and Coats–Redfern methods to obtain kinetic parameters, such as activation energies. The effects of heating rate and KOH ratio on the activation energy show simi...

We propose a new, to the best of our knowledge, rainbow technique called three-dimensional rainbow refractometry (TDRR), with a cylindrical lens in the signal collecting system. With a TDRR model based on the ray transfer matrix developed, it is proved that the tilt angle of the rainbow signal is related to the axial position of the droplet, which...

Detecting hydrogen leaks remains a pivotal challenge demanding robust solutions. Among diverse detection techniques, the fiber-optic method distinguishes itself through unique benefits, such as its distributed measurement properties. The adoption of hydrogen-sensitive materials coated on fibers has gained significant traction in research circles, c...

The shape and size of solid fuel particles are significant parameters in combustion process, and have attracted broad attentions in simulation and experiment studies. In this study, X-ray computer tomography (XRCT) and spherical harmonics (SH) were introduced and combined to conduct accurate morphology characterization of micron-sized coal powder i...

A 50 kHz high-speed two-view tomographic digital off-axis holography with pulsed illumination is developed, and applied to measure the 3D positions of burning aluminum droplets in solid propellant combustion with high accuracy.

Instruments for icing cloud particle characterization are prerequisites for icing wind tunnels in icing physics research and aviation certification. Yet, it is challenging to measure the multiple parameters of the multiscale and multiphase icing cloud particles, especially under an extremely hostile environment. To address this issue, a holographic...

Printed gas sensors, predominantly fashioned from flexible materials, are rapidly emerging as pivotal tools for gas detection, holding immense promise for wearable applications. These sensors have carved a niche in gas detection and monitoring by harnessing cutting-edge materials and intricate printing methodologies. They operate based on principle...

The laboratory method used for coal calorific value measurement has a significant hysteresis. In this paper, an on-site measurement method of coal calorific value based on high power laser rapid ignition is proposed. The effects of oxygen transverse passage velocity, thermal insulation crucible bracket and coal samples on the measurement time, unbu...

Process data in contemporary thermal power plants shows the characteristics of large capacity, strong coupling, and high-order nonlinearity, which brings great challenges to process monitoring and fault detection. A deep representation learning fault detection scheme based on stacked sparse denoising autoencoder (SSDAE) is proposed in this paper. S...

Lithium-ion batteries (LIBs) thermal safety issues such as thermal runaway (TR) triggered by thermal or mechanical abuse have been one of the most important factors hindering its development at present. In order to effectively release the excessive pressure caused by TR, a safety vent is used as a reliable safety device in commercial LIBs. However,...

Soot evolution of the ethylene-based laminar coflow diffusion flame doping with methane, propane, and propylene with the blending ratio ranging from 0 to 50% has been investigated experimentally. These fuels were selected for their different fuel structure. Spatially resolved distribution maps of the flame temperature, soot volume fraction, the flu...

It is difficult to track fuel droplets in a swirl spray combustion field due to three-dimensional (3D) movement and turbulent flame influence. The present work carries out an experimental study to investigate and track the dispersed kerosene droplets in a swirl spray combustion field. RP-3 kerosene and air are mixed and burned in open space under d...

It is difficult to measure fuel droplets in cylindrical combustors under combustion conditions, but of significance, since fuel behavior is related to combustion performance. In this study, digital off-axis holography and corresponding data treating algorithms are applied to quantify irregular spray droplets in combustion field inside a thick silic...

High-speed astigmatic dual-beam interferometric particle imaging (HADIPI) is adopted to simultaneously measure the three-dimensional (3D) position, velocity and size of spherical metal droplets. We propose to infer the depth displacement of the droplet directly from the angle shift of the interference fringe. Angular cross power spectral density is...

This work proposed a synthetic aperture rainbow refractometry (SARR) by synthesizing rainbow signals of the same droplet with dual-wavelength laser beams, in order to increase the aperture of rainbow refractometry. In this way, the SARR can apply to long distance and small droplets measurement. An achromatic imaging system, which simultaneously rec...

Wet flue gas desulfurization (WFGD) is a commonly utilized desulfurization technique. A major application of WFGD can be found in the coal-fired power plant, with up to 90% share of its market. Despite the fact that WFGD has been well developed and proven, its negative effects persist, e.g., entrainment pollution stemming from slurry droplet emissi...

Low temperature and low air pressure would cause low fuel inlet temperature and low air flowrate in aero-engine combustion chamber working in the upper atmosphere. A system including a burner normally used in actual aero engines is established to study swirl-stabilized kerosene spray combustion at conditions of low fuel inlet temperature (T < − 16...

Industrial development is an essential foundation of the national economy, but the industry is also the largest source of air pollution, of which power plants, iron and steel, building materials, and other industries emit large amounts of pollutants. Therefore, the Chinese government has promulgated a series of stringent emission regulations, and i...

Rainbow refractometry was used to measure the temperature and size of transparent spherical particles. In practice, however, there are limitations to the application of heating and cooling droplets, as the temperature measured is neither the average nor the surface or core temperature of the droplet. Reported here is an exploitation of this techniq...

Optical characterizations of droplets and sprays at a long stand-off distance are of great demand in large scale facilities. Synthetic aperture rainbow refractometry (SARR) is proposed for long range measurement, via synthesizing rainbow signals of the same droplet illuminated by two crossing laser beams from different channels of a color image sim...

Evaporation characteristics of interacting fuel droplets under the joint effect of ambient pressure, temperature and droplet size and spacing are critical to combustor design and simulation validation. This work reports an experimental study of evaporating monodisperse ethanol droplets at moderately elevated temperature (up to 673 K) and pressure (...

Liquid jet in crossflow (LJCF) has a wide application in the actual engine engineering. This article presents an experimental investigation of a water jet transversely injected into a subsonic crossflow through digital inline holographic imaging, and presents the relationship between the column trajectory and the downstream droplet distribution. A...

The astigmatic interferometric particle imaging (AIPI) model reveals that the fringe orientation shifts with droplet depth displacement, and their relationships are quantitatively formulated. The depth displacement is directly evaluated from the relative angular shift of the fringes with angular cross power spectral density, and this algorithm isol...

This work goes insight into the feasibility of astigmatic dual-beam interferometric particle imaging (ADIPI) to enable the measurement of three-dimensional (3D) positions and sizes of spherical metal droplets at panoramic scattering angle. The ADIPI signal exists at arbitrary angle except the two laser beam axes, defined as backward scattering regi...

Three-dimensional (3D) visualization on droplet splashing characteristics is of great importance in the research of droplet impact on a solid surface. In this study, a high-speed digital in-line holography (DIH) system with 1024×1024\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \u...

The implementation of ultra-low emission (ULE) limits (SO2: 35 mg/m³, NOx: 50 mg/m³, PM: 10 mg/m³) promoted the development of flue gas treatment technologies in China. Pollutant control technology development for Chinese coal-fired power plants was summarized and an analysis of the applicability and cost of pollutant control technologies was condu...

Vessel emissions have contributed a great deal to air quality deterioration in China. Hence, the Chinese government has promulgated a series of stringent emission regulations. It is in this context that vessel emission control technology research is in full swing. In particular, during the 13th Five-Year Plan, the air pollution control technology o...

Considerable interest and demand exists in multi-parameter characterization of colloidal droplets. However, an optical in-situ characterization of such droplets is a particular challenge due to its heterogeneous and multi-scale nature, motivating the investigation of a dual-wavelength extinction rainbow refractometry. An analytical model is propose...

Accurate measurement of droplet size, temperature and concentration in sprays is of great importance but still challenging in applications. The secondary rainbow refractometry is investigated in this work to measure refractive index and size of transparent spherical droplets, with better sensitivity than the first rainbow. Inversion algorithm of th...

The discrimination and measurement of complex particle field mixing spherical liquid droplets and other solid irregular particles are challenging but of significance in industry, e.g., droplets and ice crystals in icing wind tunnel or in mixing phase cloud during airplane icing flight test. An approach is proposed by combining digital inline hologr...

The whole recording and reconstruction processes based on the ABCD transfer matrix of the digital off-axis holography through a pipe are researched. Comparisons of the simulations between inline and off-axis holography are presented.

In various multiphase flows, the characterization of particle dynamics is of great significance to understand the interaction between particles and the surrounding flows. Digital holography (DH) is a versatile 3D imaging technique, which has shown great advantages in quantitative analysis and non-intrusive diagnosis of various particle fields. This...

Rainbow refractometry has been used in the past to measure size and refractive index of spherical particles, typically droplets in a spray. In the present study, conventional optical configurations for point measurements or line measurements have been extended to allow also the particle position in a plane to be determined, and hence, the designati...

Evaporation behavior of nanofluid droplets within a fuel cloud plays an important role in most applications. Reported here is an experimental study on the evaporation characteristics of a monodisperse droplet stream of pure ethanol containing aluminum nanoparticles with varying concentrations (up to 0.3 wt.%) at different environmental temperatures...

Accurate particle detection is a common challenge in particle field characterization with digital holography, especially for gel secondary breakup with dense complex particles and filaments of multi-scale and strong background noises. This study proposes a deep learning method called Mo-U-net which is adapted from the combination of U-net and Mobil...

This work investigates the astigmatic dual-beam interferometric particle imaging (ADIPI) to enable the measurement of the three-dimensional (3D) spatial position and particle size of spherical opaque particles. A general theoretical model based on the generalized Huygens-Fresnel integral and the ray transfer matrix model is established to character...

In this paper, we study the breakup of a circular jet disturbed by wavelength modulation to produce periodic but non-uniform patterns of droplet sizes. Instead of a single wavelength disturbance, a series of perturbations containing two different wavelengths in one cycle was applied to excite the jet. Jet breakup patterns and droplets formation und...

Droplet formation and evaporation are key processes of spray combustion, the mechanism of which is yet not fully understood. In this study, we develop a method based on high-speed (25 kHz) digital off-axis holography (DOH) to visualize and measure burning ethanol droplets in the atomization. Ligaments and fragments from a burning drop internally bl...

A nonlinear dynamic model considering the effect of heat transfer on outlet pulverized coal mass flow is established based on the principles of conservation laws. Raw coal moisture estimation which is connected to coal mass and internal energy in coal mills is included in the model. The model has proved to have good predictions and reflects the dyn...

Sprays generated by atomization processes have been used in a wide range of fields. The size and spatial distribution of volumetric droplets in a spray are critical parameters in industrial applications. Astigmatic interferometric particle imaging (AIPI), an extension of the traditional interferometric particle imaging (IPI), is developed to simult...

Morphology measurement is essential for a better understanding of irregular particle dynamics. Digital holography of side scattering is applied to measure the morphology and 3D position of pulverized coal particles. The digital holographic recording of particle side scattering is modelled and the formula is verified by experiments. A side scatterin...

Ammonia (NH3) is an important base gas in the atmosphere and has received extensive research interest due to its role on secondary aerosol formation. However, the effects of NH3 on the photochemical smog oxidants formation including ozone and secondary aerosol did not attract much attention. In this study, a set of smog chamber experiments was cond...

Coal calorific value is an important indicator in the combustion optimization of power plants and the calculation of operating efficiency. Hence, the in-situ measurement of the coal calorific value is needed. This study developed an in-situ calorific value determination method and established the related model. The feasibility was evaluated by inve...

Oscillation of micron-sized liquid droplet is an interesting and common phenomenon, and is used to measure surface tension and viscosity with the recently developed time-resolved rainbow refractometry. Droplets produced by a monodisperse droplet generator are excited to oscillate at a small amplitude (less than 1%) and high frequency (of the order...

Under the extensive implementation of ultra-low emission facilities, sulfur trioxide (SO3) has received increasing attention. This article reviews the measurement techniques for SO3 in flue gas, which include controlled condensation method (CCM), isopropanol absorption method (IPA), salt method, tunable diode laser absorption spectroscopy (TDLAS),...

Timely monitoring of the calorific value of coal is beneficial to combustion regulation during the operation of coal-fired power plants. An in-situ measurement system applied to power plants was proposed. The related model was described in detail and validated through bomb calorimetry. The influences of multiple model parameters with different ther...

We propose astigmatic dual-beam interferometric particle imaging (ADIPI) to simultaneously measure the three-dimensional (3D) position and size of spherical metal droplets. A theoretical model reveals that the orientation and spacing of the ADIPI fringes generated from the two reflections propagating through an astigmatic imaging system relate to t...