Xi Gao

Xi Gao
Guangdong Technion-Israel Institute of Technology

PhD

About

67
Publications
15,038
Reads
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1,237
Citations
Citations since 2016
51 Research Items
1077 Citations
2016201720182019202020212022050100150200250300
2016201720182019202020212022050100150200250300
2016201720182019202020212022050100150200250300
2016201720182019202020212022050100150200250300
Additional affiliations
June 2021 - present
Guangdong Technion - Israel Institute of Technology
Position
  • Professor (Assistant)
August 2019 - May 2021
Leidos; National Energy Technology Laboratory
Position
  • Researcher
March 2017 - August 2019
National Energy Technology Laboratory, Morgantown, United States
Position
  • PostDoc Position
Education
September 2010 - May 2013
Zhejiang University
Field of study
  • Chemical Engineering
September 2006 - July 2010
Xiamen University
Field of study
  • Chemical Engineering

Publications

Publications (67)
Article
Full-text available
This article presents the development and validation of the Superquadric Discrete Element Method (SuperDEM) for non-spherical particle simulation using a superquadric particle method in open-source CFD suite MFiX. A superquadric particle–particle contact algorithm with accelerating and stabilizing strategy was developed. A superquadric particle–arb...
Article
An efficient biomass pyrolysis process requires a comprehensive understanding of the chemical and physical phenomena that occur at multi‐length and time scales. In this study, a multiscale computational approach was developed and validated for biomass pyrolysis in a packed‐bed reactor by integrating pyrolysis kinetics, a particle scale model, and S...
Article
Full-text available
A SuperDEM-CFD coupled model was developed and validated in open-source MFiX for simulating non-spherical particles fluidization hydrodynamics in fluidized beds. The non-spherical particle was modeled using a superquadric method and shapes can be modeled by only varying five parameters. DPVM-Satellites interpolation scheme was developed to distribu...
Article
Coarse-grid two-fluid simulation of gas-solid fluidized bed reactors based on the kinetic theory of granular flow exhibits a significant dependence on drag models, especially for Geldart A particles. Many drag models are available in the literature, which have been reported to work for different systems. This study focused on the evaluation of an e...
Article
Full-text available
The pyrolysis products of different biomass are difficult to predict due to the complex biomass properties and wide range of operating conditions. In this study, machine learning techniques based on Artificial Neural Networks, Gradient Boosting, Decision Trees, Random Forest, K-Nearest-Neighbors, Bagging Regressor, and Lasso Regression were employe...
Article
Full-text available
Biomass pyrolysis is a promising renewable source instead of fossil fuels. In this study, a multiscale CFD model for high-temperature biomass pyrolysis was developed in open-source MFiX with an intraparticle model and a detailed multistep kinetic scheme. The intraparticle transport phenomena were simulated with a one-dimensional particle model. Th...
Article
Accurate modeling and simulation of irregular shape sand particle fluidization are challenging as particle shape-resolved simulation is complex and time-consuming. In this study, the coarse-grained discrete element model (CG-DEM)-computational fluid dynamics (CFD) was adopted to improve the computational feasibility of traditional CFD–DEM and simpl...
Article
Full-text available
Autothermal operation of fast pyrolysis is an efficient process-intensification technique wherein exothermic oxidation reactions are used to overcome the heat-transfer bottleneck of conventional pyrolysis. The development of accurate, reliable modeling toolsets is imperative to generating a deeper understanding of biomass autothermal pyrolysis syst...
Preprint
Full-text available
The binary fluidization of Geldart-D type non-spherical wood particles and spherical LDPE particles was investigated in a laboratory-scale bed. The experiment was performed for varying static bed height, wood particles count, as well as superficial gas velocity. The LDPE velocity field were quantified using Particle Image Velocimetry (PIV). The woo...
Article
Industrial-scale gasifiers are traditionally designed using performance data from small-scale systems and expert experiences. In this research, the computational fluid dynamics (CFD)-coarse-grained discrete element method (CGDEM) model in open-source software MFiX was employed to assist the design of a 22 MW updraft moving-bed coal gasifier. A quas...
Article
Full-text available
The accuracy of coarse-grained Euler-Lagrangian simulations of fluidized beds heavily depends on the mesoscale drag models to account for the influences of the unresolved sub-grid structures. Traditional filtered drag models are regressed with mesoscale markers such as voidage and slip velocities. In this research, a filtered drag was regressed wit...
Data
Source code for the coupling of MFiX with PyTorch Case files
Code
couple MFiX with PyTorch ANN model
Article
Full-text available
Coupling particle and reactor scale models is as essential as reactor fluid dynamics and particle motion for accurate Computational Fluid Dynamic (CFD) simulations of biomass fast pyrolysis reactors due to intraparticle heat transfer and chemical reactions controlling conversion time and product distributions. Direct online coupling of a particle m...
Article
Full-text available
In fluidized bed biomass fast pyrolysis, the biomass is converted to biochar and elutriated. The elutriation rate is a key parameter in reactor designs and operations. This research presents a video‐based continuous measurement of biochar elutriation rate in a fluidized bed with sands and biomass as bed materials. The fluidized bed is simulated wit...
Article
Full-text available
Multi-scale computational fluid dynamics (CFD) simulation bridges the gaps between particle and reactor scales in the modeling of biomass pyrolysis. Its accuracy depends on the coupling of sub-models in different scales. Recent progress includes (a) detailed kinetics with 32 reactions and 59 species; (b) efficient intra-particle models for thermall...
Article
Full-text available
Between the molecular and reactor scales, which are familiar to the chemical engineering community, lies an intermediate regime, here termed the “mesoscale,” where transport phenomena and reaction kinetics compete on similar time scales. Bioenergy and catalytic processes offer particularly important examples of mesoscale phenomena owing to their mu...
Article
Full-text available
Granular flows are widely encountered in many industrial processes and natural phenomena. Discrete Element Modeling (DEM) is a useful tool for understanding and troubleshooting devices, which handle granular materials. However, its applicability is significantly limited by the huge computational cost associated with detecting and computing collisio...
Article
A detailed biomass pyrolysis kinetic scheme was assessed in the multiscale simulations of a single-particle pyrolyzer with slow pyrolysis and a pilot-scale entrained flow pyrolyzer with fast pyrolysis. The detailed kinetic scheme of biomass pyrolysis developed by the CRECK group consists of 32 reactions and 58 species. A multiscale simulation model...
Article
Full-text available
The shape of biomass particles influences intra-particle heat transfer, particle-particle collisions, interphase momentum, heat transfer, and pyrolysis yield. In this research, the effects of these multi-scale phenomena are captured using a glued-sphere computational fluid dynamic discrete element method (CFD-DEM) with 3-D intra-particle models. Th...
Article
Full-text available
In this research, a glued‐sphere Discrete Element Method (DEM) method was implemented in the open‐source, Computational Fluid Dynamics (CFD) software MFiX. The implementation was verified using a cylinder‐wall collision and then validated by simulating the packing and fluidization of non‐spherical particles. The validated code was applied to simula...
Article
Full-text available
It is notoriously difficult to build an accurate universal model for biomass pyrolysis due to its sensitivity to a wide number of critical material attributes such as chemical species and physical sizes. In this work, a biomass pyrolysis kinetics with 32 heterogeneous reactions and 59 species was implemented in an open-source multiphase computation...
Article
Computational fluid dynamics (CFD) is a powerful tool for prediction and analysis of complex multiphase flow hydrodynamics and residence time distribution (RTD) in chemical reactors. This study presented the validation and application of a filtered drag model for solid RTD prediction in a pilot-scale fluid catalytic cracking (FCC) circulating fluid...
Article
High fidelity three‐dimensional (3‐D) numerical simulations of commercial‐scale coal gasifiers are very time consuming and expensive. This paper proposes a reduced‐order modeling approach that uses quasi one‐dimensional (1‐D) CFD‐DEM simulation results to serve as an accurate initial condition for the 3‐D simulation, which significantly shortens th...
Article
The spatial distribution of solid particles is a key factor affecting the performance of fluidized bed reactors. Non-invasive techniques including radioactive particle tracking (RPT) and positron emission particle tracking (PEPT) are deployed to measure the solids distribution. Different methods to calibrate the particle tracking measurements have...
Article
Efficient utilization of biomass is challenging due to the complexity of the feedstock at molecular, particle, and reactor scales. Direct coupling of particle scale model and reactor scale simulation is computationally infeasible. In this research, the results from a particle resolved simulation were used to calibrate the heat transfer and reaction...
Article
Full-text available
This paper investigated the fluidization of sands and small Geldart A biomass mixtures. The mixture fluidized like Geldart A type particles with a uniform bed expansion regime before bubbling. The video recorded color distance between pure sands and sands‐biomass mixtures was used to estimate the sands‐biomass mixing. The coarse‐grained CFD‐DEM wit...
Article
Accurate prediction of transport phenomena is critical for VPU reactor design, optimization, and scale-up. The current study focused on the validation and application of a multiphase CFD model within an open-source code MFiX for hydrodynamics, temperature field, and residence time distribution (RTD) simulation in a non-reacting circulating fluidize...
Article
Full-text available
The bubbling fluidized bed reactor is widely used in fast pyrolysis of biomass. Discrete simulation of this reactor is challenging due to many sand particles and lack of accurate drag corrections accounting for the interaction of two different solid particles with different properties. In this research, the computational cost is reduced by using th...
Article
Fluidization behavior of biomass and glass beads binary mixtures in a bubbling fluidized bed was experimentally investigated. Mixtures containing different mass fraction of Loblolly Pine white wood and glass beads were fluidized at different fluidization velocities. The particle properties were characterized in a QICPIC that uses a dynamic image pr...
Article
Fluidization behavior of biomass and glass beads binary mixtures in a bubbling fluidized bed was experimentally investigated. Mixtures containing different mass fraction of Loblolly Pine white wood and glass beads were fluidized at different fluidization velocities. The particle properties were characterized in a QICPIC that uses a dynamic image pr...
Article
Full-text available
The segregation of equal volumes of 2-mm and 4-mm particles inside a 14-cm-diameter spherical tumbler is numerically investigated using the Discrete Element Method (DEM). Two types of segregation take place. Initially, radial segregation appears, and then axial segregation occurs. The radial segregation occurs quickly due to percolation, with large...
Article
Full-text available
Biomass gasification is widely recognized as an effective method to obtain renewable energy. It is very challenging to accurately predict the syngas and tar compositions. In this work, a chemical reaction kinetics Model based on comprehensive gasification kinetics is proposed to simulate downdraft biomass gasification. The Kinetic Model is validate...
Article
Multiphase flow hydrodynamics in a novel gas‐liquid‐solid jet‐loop reactor (JLR) were experimentally investigated at the macro‐ and meso‐scales. The chord length distribution was measured by an optical fiber probe and transformed for bubble size distribution through the maximum entropy method. The impacts of key operating conditions (superficial ga...
Article
Full-text available
Widespread cultivation of phototrophic microalgae for sustainable production of a variety of renewable products, for wastewater treatment, and for atmospheric carbon mitigation requires not only improved microorganisms but also significant improvements to process design and scaleup. The development of simulation tools capable of providing quantitat...
Article
This study focused on assessing the effect of mesoscale solid stress in the coarse grid TFM simulation of gas‐solid fluidized beds of Geldart Group A particles over a broad range of flow regimes, including bubbling, turbulent, fast, and pneumatic transport fluidization regimes. Particularly, the impact of mesoscale solid pressure, mesoscale solid v...
Article
A multiphysics model has been developed to predict the effects of fluid mixing and shear stress on microalgal growth in an airlift photobioreactor. The model integrates multiphase flow dynamics, radiation transport, shear stress, and algal growth kinetics using an Eulerian approach. The model is first validated by comparing its predictions with exp...
Article
Full-text available
For a long time, salt tracers have been used to measure the residence time distribution (RTD) of FCC particles. However, and due to limitations in experimental measurements and simulation methods, the ability of salt tracers to faithfully represent RTD’s has never been directly investigated. Our current simulation results using coarse grained CFD-D...
Article
Accurate description of light-limited algal growth, especially under short light/dark (L/D) cycles, is crucial for prediction of photobioreactor performance and for optimization of operating conditions. Here, a variety of widely used photosynthetic unit (PSU)-based models are evaluated to determine their ability to predict algal specific growth rat...
Article
A comprehensive Eulerian approach for integrating a three-phase CFD model, a sophisticated detailed model for radiation transport, and a transport equation for algal growth kinetics is developed and utilized to predict the performance of a Taylor vortex algal photobioreactor. Simulation predictions are compared with corresponding experimental data...
Thesis
Full-text available
Development of more efficient algal photobioreactors (PBRs) is driven by increasing interest in algaculture for the production of fuels, chemicals, food, animal feed, and medicine, as well as carbon capture. While at present, the cost and microalgae production capacity are one of its restrictions when competition with other biodiesel feedstock. The...
Article
A comprehensive quantitative model incorporating the effects of fluid flow patterns, light distribution, and algal growth kinetics on biomass growth rate is developed in order to predict the performance of a Taylor vortex algal photobioreactor for culturing Chlorella vulgaris. A commonly used Lagrangian strategy for coupling the various factors inf...
Article
Bubbly gas-liquid Taylor-Couette vortex flow has been the subject of several recent investigations both because of interest in bubble-induced drag reduction and because such devices have potential applications to a variety of chemical and biochemical processing problems. In order to quantitatively describe the hydrodynamics of highly turbulent two...
Article
Recently it has been demonstrated that algal biomass yield can be enhanced using fluid flow patterns known as Taylor vortices. It has been suggested that these growth rate improvements can be attributed to improved light delivery as a result of rapid transport of microorganisms between light and dark regions of the reactor. However, Taylor vortices...
Article
Gas–liquid Taylor–Couette flow devices have attracted interest for use as chemical and biological reactors, and consequently the accurate prediction of interphase mass transfer coefficients is crucial for their design and optimization. However, gas–liquid mass transport in these systems depends on many factors such as the local velocity field, turb...
Article
Measurement of particle velocity in fluidized beds is always technically difficult. A new method based on cross-correlation principle was proposed to calculate time-averaged velocity of particles. Considering the different reliabilities of signal segments, a cross-correlation coefficient was introduced into the formula for calculating time-averaged...
Article
A bubble–emulsion two-fluid model is proposed for the simulation of gas–solid flow in bubbling fluidized beds. This work proposes an analogous research program, according to the analogies in the flow regime and the mechanism between a gas–solid bubbling fluidized bed and a gas–liquid bubble column. The research includes a complete description of th...
Article
Particle velocity in a 95 mm ID fluidized bed was measured with PV6D reflective optical fiber probes and then the signal analysis was conducted. A self-made disc device for velocity calibration was used to adjust the particle velocity calculated by the cross-correlation method. The effects of object speed and measuring distance on the measured velo...
Article
The transition section between bottom dense zone and top dilute zone is important for fast gas-solids catalytic reactions,such as methanol to olefins(MTO).Solids concentration and fluctuation parameters in the transition section of a fluidized bed with 95 mm i.d.were measured by using reflective optical fiber probe(PV6D).The influences of superfici...
Article
The solid behavior in a turbulent fluidized bed was studied by combination of experimental measurements and computational fluid dynamics (CFD) simulations. Solid fractions were measured by optical fiber probe under three different superficial gas velocities and three different static bed heights at different axial levels. The experimental results s...
Article
A comprehensive two-dimensional (2D) reactor model has been developed to simulate the flow behavior in a fixed-bed reactor for preparing olefins from methanol. An exponent-function kinetic model based on a lumped-species reaction scheme has been incorporated to a commercial computational fluid dynamics (CFD) code Fluent by user defined functions fo...
Article
A comprehensive two-dimensional heterogeneous reactor model was developed to simulate the flow behavior and catalytic coupling reaction of carbon monoxide (CO)–diethyl oxalate (DEO) in a fixed-bed reactor. The two-temperature porous medium model, which was revised from a one-temperature porous medium model, as well as one equation turbulent model,...
Article
A Eulerian–Eulerian model incorporating the kinetic theory of granular flow was applied to describe the gas–solid two-phase flow in fluidized bed polymerization reactors. The model parameters were examined, and the model was validated by comparing the simulation result with the classical calculated data. The effects of distributor shape, solid part...
Article
A three-dimensional (3D) computational fluid dynamics (CFD) model, using an Eulerian-Eulerian two-fluid model which incorporates the kinetic theory of granular flow, the energy balance and heat transfer equations, was developed to describe the steady-state liquid-solid two-phase flow in a loop propylene polymerization reactor composing of loop and...

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