One-step Global Reaction Research Articles

Influence of the hydrogen transverse injection mode in a scramjet combustor performance

This paper focuses on the numerical investigation of the transverse hydrogen injection technique in the supersonic airflow on the combustor performance of a scramjet technological demonstrator developed at Universidade Federal do Rio Grande do Norte (UFRN). The UFRN's scramjet vehicle was designed to be fully operational at a hypersonic velocity of 2050 m/s (Mach number 6.8), at 30 km of altitude, which provided a temperature of 1156.95 K and supersonic velocity of 1414.39 m/s (Mach number 2.1), at the combustion chamber entrance. Hydrogen was transversally injected into supersonic airflow at a sonic speed of 1318.46 m/s. A set of 2D-RANS simulations of the reactive flow was performed in combination with a simplified chemical kinetics approach based on the finite-rate chemistry model, defined by a one-step global reaction based on Arrhenius expression to combustion modeling. The turbulence was modeled by the k-kl-ω transition model. Different transverse fuel injections with different dimensions and positioning of injectors were evaluated keeping the same inlet conditions: single-injection versus dual-injection modes. A detailed visualization of several flow phenomena, such as the formation of shock waves, and the performance combustion parameters on the combustor surface were discussed. The analyses indicated hydrogen combustion with a predominantly supersonic flow regime. The transversal injection caused the detachment of the boundary layer as indicated by the recirculation flow structures in the neighboring region next to the injectors. Flow analyses indicate that the purely oblique shock trains were established tending to redirect the airflow over the mixing layer and accelerate the hydrogen burning. Nevertheless, the results showed that this was a local effect since the downstream both mixing and combustion efficiency increased. The dual-injection mode proved to be a promising injection method due to the higher global fuel penetration, elevated from 27,9% to 33,8%, and higher combustion efficiency, increased from 10,33% to 21,99%, with reduced addition of total pressure loss, concerning the single-injection case. Additionally, the growth behavior of performance curves showed that an extension of the combustor downstream length can be indicated to maximize combustor performance.

Kinetic studies of ignition of coal char particle suspension in hot air

Coal ignition has been a focal point in the pursuit of improved energy efficiency and reduced emissions. This study focuses on investigating the kinetic characteristics of char ignition within a closed reactor. The combustion process is modeled using a one-step global reaction in a quiescent air environment. The results show that particle ignition time increases with equivalence ratio and particle size, while decreases with gas initial pressure and initial temperature. Particle ignition temperature is minimally affected by the particle size, slightly influenced by the gas initial pressure and initial temperature, but substantially influenced by the equivalence ratio. In the fuel-rich condition, the coal char combustion exhibits a thermal runaway stage, primarily driven by the escalating particle temperature, followed by a decaying stage, mainly influenced by the depleting oxygen mass fraction. The dominant kinetic factors affecting the heat release rate (HRR) peak are detailly investigated: the HRR peak shows an initial increase and subsequent decrease with the equivalence ratio, which is mainly controlled by the total particle number and particle temperature; Particle size affects the HRR peak through altering the total particle specific surface area, i.e., the product of the particle number and the particle diameter squared; the gas initial pressure and temperature all affect the HRR peak through directly altering the gas density. Additionally, larger retention coefficient leads to faster particle ignition and higher HRR peak. These findings provide valuable insights into the regulations of coal combustion processes, particularly in scenarios involving elevated pressure and temperature, such as coal/mine explosions.

A DNS study of pulverized coal combustion in a hot turbulent environment: Effects of particle size, mass loading and preferential concentration

In the present study, pulverized coal combustion in a hot turbulent environment is investigated using direct numerical simulation (DNS). The coal particles are tracked in the Lagrangian framework while the flow is solved in an Eulerian way. A model involving two competing reactions is used for describing the process of coal devolatilization. The volatile matter is treated as a postulated substance (CaHbOc) and a two-step global reaction mechanism for volatile combustion is adopted. The char combustion is modeled using a one-step global reaction model. The effects of various factors, such as particle size, mass loading and preferential concentration, on the combustion process of coal particles were explored. It was found that, the location of reaction zones appears more upstream and the volatile matter concentration is higher for the cases with smaller particles. The combustion modes were examined. It was shown that the contribution of premixed combustion decreases with increasing particle size while non-premixed combustion prevails in all cases. The increase of particle mass loading results in an increase of volatile matter mass fraction, which leads to higher heat release rate and combustion temperature. Through Voronoï analysis, the preferential concentration of particles was examined. It was found that the preferential concentration behavior of particles is more prominent when the particle Stokes number (St) is close to unity. The volatile matter concentration is higher when particles are preferentially concentrated, facilitating coal particles to ignite.

Kinetic parameters and reaction mechanism study of biomass pyrolysis by combined kinetics coupled with a heuristic optimization algorithm

Kinetic reaction mechanism plays a key role in accurately predicting biomass pyrolysis behavior. However, the order-based reaction mechanism is usually defined as the default in the existing kinetic studies. For the purpose of exploring the exact kinetic reaction mechanism of biomass pyrolysis, the combined kinetic method is tried here by coupling two common kinetic models (one-step global reaction and three-parallel reaction). The decomposition rate expressed by the method is related to three key parameters, whose values are corresponding to the establishment of reaction mechanism. The combined kinetic method is further coupled with a heuristic optimization algorithm to obtain more exact kinetic parameters in order to explore the reaction mechanism. The results show that it is hard to infer the reaction mechanism based on one-step global reaction, while based on three-parallel reaction, the respective reaction mechanism of each component can be established as Power law for cellulose, Order-based for hemicellulose and lignin by comparing with the thermogravimetric data. More importantly, the established mechanism and optimized parameters can be used to accurately predict the micro-scale pyrolysis behavior of biomass (beech) at a wider range of heating rates.

Effects of curvature on triple flame propagation in fuel-oxidizer counterflow

In this study, we analyze the propagation of an expanding triple flame in an axisymmetric counterflow of a fuel against an oxidizer. The problem is formulated as a thermo-diffusive model with one-step global reaction. An asymptotic analysis in the limit of large activation energy and weak strain rate is conducted. The study is supported and complemented by numerical simulations carried out for arbitrary values of the strain rate. In addition to the flame front curvature 1/Rt associated with the variation in the reactants concentrations transverse to the mixing layer, the propagation of the expanding triple flame also depends on the azimuthal curvature 1/Rf where Rf is the front leading edge radial distance. As the triple flame expands to large radial distances, its propagation becomes quasi-steady. Under a quasi-steady state assumption, an explicit expression is derived for the displacement speed of the triple flame, which is found to be linearly proportional to the total curvature 1/Rf+1/Rt. Two-dimensional axisymmetric simulations are conducted to validate in particular the quasi-steady assumption. These include transient simulations of the expanding triple flame which are compared to the numerical solution of the steady eigenvalue problem obtained in a frame attached to the propagating front under a quasi-steady assumption. Following a transient ignition phase, the triple flame is found to propagate in a quasi-steady manner when Rf (measured with the stoichiometric planar flame thickness) exceeds 5, approximately. Although the theoretical analysis is performed in the weak strain limit, the linear dependence of the triple flame speed on the curvature 1/Rfis found to be applicable over a wide range of strain rates. Besides, the analysis is extended for inwardly propagating triple flames (flame holes) and similar expressions describing the relationship between displacement speed of the triple flame and curvatures are obtained.

Effect of oblique shock wave induced from a wavy-wall combustor surface for a splitter plate scramjet combustor

The shorter residence period of supersonic air in a scramjet combustor makes mixing and combustion challenging. Mixing augmentation occurs at the fuel-supersonic air interface. Multiple interactions between shock waves and the shear layer may significantly affect this inter surface. In this research, an attempt has been made to analyze how multiple oblique shock waves interact with the shear layer. The primary splitter plate combustor bottom wall is modified with a wavy-wall surface to ensure the development of multiple oblique shock waves. The internal flow field with and without a wavy wall surface has been analyzed by solving the two-dimensional Reynolds averaged Navier-Stokes equations and SST k-ω turbulence model. The reaction between ethylene fuel and the air is modeled with a global one-step reaction mechanism with finite rate eddy dissipation turbulence chemistry interaction. The flow disturbances with the wavy-wall surface have been evaluated by analyzing the numerical results like the flow structure, pressure, velocity, reaction rate, vortices, turbulence intensity, and interactions among shock wave, shear mixing, and boundary layers. The oblique shock waves induced from the wavy-wall surface significantly impact the mixing of fuel and air and successful reaction mechanism from the visualization of flow structure and concern results.

Consideration of the interactions between the reaction zones in the new extended Eddy dissipation concept model

The latest Direct Numerical Simulation (DNS) modeling results in flameless combustion suggest interactions between the combustion reaction zones. The New Extended Eddy Dissipation Concept (NE-EDC) model, where model coefficients are calculated based on local Reynolds and Damköhler numbers, was proposed to improve the standard Eddy Dissipation Concept (EDC) model's accuracy when modeling flameless combustion, but this model does not include the interactions between the reaction zones.In this work, a revised version of the NE-EDC model is presented, called here Generalized NE-EDC model, where the chemical time scale is calculated in detail, considering the reaction rates of CH4, H2, O2, CO and CO2, making the interaction between the reaction zones more realistic (in the NE-EDC only a one-step CH4 global reaction mechanism is considered). A comparative study of four global reaction mechanisms is carried out to select the best mechanism for chemical time scale definition: the adjusted Jones & Lindstedt (JL1); the adjusted Westbrook & Dryer (WD1); the adjusted Westbrook & Dryer (WD2); and the one-step CH4 global mechanism (1-step).The four global reaction mechanisms, in combination with the NE-EDC model, are applied to the Delft lab-scale furnace and the modeling results are compared against those experimental measurements. The NE-EDC modeling results, in combination with WD2, present a slight improvement over the other global mechanisms in flameless modeling.

Hydrogen fueled scramjet combustor with a wavy-wall double strut fuel injector

The demand for the enhancement of scramjet performance is increasing worldwide due to its tremendous and upcoming applications. The major challenge in scramjet engines is the mixing of fuel and air and succeeding combustion at supersonic speed. In a scramjet combustor flow field, the development of high turbulence (flow disturbance), shear-mixing layer, and oblique shock waves are the key factors to magnify the mixing efficiency of fuel and air at the significantly less resident time of air in the combustion chamber. Based on these techniques, an innovative strut fuel injector with a wavy wall surface and double strut has been investigated for possible mixing enhancement of fuel and air. These results are compared with the basic single wedge strut available in the open literature to identify the performance improvement. The computational geometries are modeled with Reynolds-averaged Navier Stokes equations, SST k-ω model, and global one-step reaction mechanism. All the flow modeling has been solved with finite volume and a second ordered upwind discretization scheme. The evaluation of scramjet internal flow structure and numerical results found that the double strut with a wavy-wall shape improved the mixing efficiency and combustion phenomenon significantly. The mixing and combustion profiles reveal that wavy-wall double strut generates an early complete mixing within a distance of 0.17 m with increased mixing and combustion efficiency of 18% and 20%, respectively.

Modeling Hydrogen Chloride and Aluminum Surface Interactions for Spacecraft Fire Safety Applications

Experiments and modeling were performed to determine the surface kinetics of gaseous hydrogen chloride (HCl) with aluminum surfaces subjected to various treatments. HCl and other acid gases are a spacecraft fire safety concern because they are commonly found in products from electrical wire pyrolysis. Three types of aluminum surfaces were considered: surface with chromate conversion coating (iridite), anodized, and untreated. A test cell made of polytetrafluoroethylene was used to measure the difference in the HCl concentration from the inlet to the outlet. A simple one-step global surface reaction model that accounts for active surface sites was proposed. The kinetic constants were calibrated using the measured data. The calibrated model was validated against experiments with different flow rates and HCl inlet concentrations. The results showed that anodized aluminum had the most HCl uptake, followed by the iridite, and then the untreated aluminum. The amount of HCl uptake appeared to correlate well with the thickness of the oxide layer on aluminum. The relevance of these findings is discussed with respect to the design of large-scale fire safety experiments in space and various fire safety application scenarios.

A multiphase SPH framework for solving the evaporation and combustion process of droplets

PurposeThis paper aims to introduce a two-dimensional smoothed particle hydrodynamics (SPH) framework for simulating the evaporation and combustion process of fuel droplets.Design/methodology/approachTo solve the gas–liquid two-phase flow problem, a multiphase SPH method capable of handling high density-ratio problems is established. Based on the Fourier heat conduction equation and Fick’s law of diffusion, the SPH discrete equations are derived. To effectively characterize the phase transition problem, inspired by volume of fluid method, the concept of liquid phase mass fraction of the SPH particles is proposed. The one-step global reaction model of n-hexane is used for the vapor combustion.FindingsThe evaporation and combustion process of single droplet conforms to the law. The framework works out well when the evaporation of multiple droplets involves coalescence process. Three different kinds of flames are observed in succession in the combustion process of a single droplet at different inflow velocity, which agree well with the results of the experiment.Originality/valueTo the best of the authors’ knowledge, this is the first computational framework that has the capability to simulate evaporation and combustion with SPH method. Based on the particle nature of SPH method, the framework has natural advantages in interface tracking.

Large eddy simulation of turbulence-combustion interactions in a stagnation point reverse flow combustor

This study focuses on the interaction between turbulence and combustion in a stagnation point reverse flow (SPRF) combustor. Turbulent activities have been examined with large eddy simulation (LES) technique including k-equation subgrid turbulence modeling. The non-premixed and premixed combustion cases are modeled by using partially stirred reactor (PaSR) combustion model with one-step global reaction chemistry. In the non-premixed operation, a lifted flame is located about the two-thirds of the combustor, while an attached flame is observed for the premixed operation. Results of the complex flow field and combustion dynamics showed that SPRF combustor can operate at low emission conditions. The existence of the shear layer between the coaxial jets resulted with intense mixing, which further increases the efficiency of the combustor. Exhaust gas re-circulation prevented high temperature levels, hence high NOx levels within the combustor. The preliminary thermo-acoustic study showed that noise levels are highly affected by the turbulent production and heat release generation mechanisms. The contribution of the combustion noise to the total noise level is higher in the non-premixed operation as compared to the premixed one.

Effects of Combustion Model and Chemical Kinetics in Numerical Modeling of Hydrogen-Fueled Dual-Stage HVOF System

The present work examines the effect of utilizing different combustion models and chemical kinetics in predicting the properties of gas and particle phases in a hydrogen-fueled, dual-stage high-velocity oxy-fuel (HVOF) thermal spray system. For this purpose, effects of two combustion models, eddy dissipation concept (EDC) and eddy dissipation model (EDM), on the temperature and velocity fields in the system are studied. The computations using EDC model are performed for detailed and reduced chemical kinetics and for a range of mixture from lean to rich. It is found that EDC with multi-step reaction mechanism predicts higher temperatures for the flow and particle in the warm spray system. In contrast to EDC, the EDM with one-step global reaction shows extra heat release outside the HVOF barrel for rich mixtures which leads to unphysical higher prediction of particle temperature. The simulations using EDC model with detailed and reduced chemical kinetics show some exothermic reactions in converging-divergent nozzle of the system. The heat release from these reactions has profound impacts on the flow and particle temperatures and affects the gas dynamic behavior of flow considerably. Finally, it is discussed that moving toward rich mixtures is more reliable way to control the particles temperature.

Effect of inorganic salt and organic acid on the thermal runaway of hydrogen peroxide

Hydrogen peroxide with the presence of catalytic metal ions or incompatible organic matters has caused some fire and explosion accidents in recent years. This work further studied the effect of inorganic salt and organic acid on the thermal runaway behaviour of hydrogen peroxide via rapid screening device (RSD), accelerating rate calorimeter (ARC) and a batch reactor. Experimental results revealed that both the metal ions and their corresponding inorganic acid ions have significant influences on the thermal runaway of H2O2: the catalytic effect of metal ion followed Fe2+ > Fe3+ > Cu2+, and the synergistic effect of inorganic acid ion followed Cl− > SO42−. No explosion was detected under RSD and ARC test conditions. In addition, a one-step global reaction kinetic model characterized as adiabatic temperature increase and final exothermic temperature was briefly described to estimate the kinetic parameters of the mixture of H2O2 with/without organic acid. The analysis showed that the runaway reaction of H2O2 with formic acid or acetic acid is a first order reaction at a low temperature range (<100 °C) and the thermal runaway risk of H2O2/HCOOH > H2O2/CH3COOH, along with the decreasing apparent activation energy and pre-exponential factor.

Symmetric and Nonsymmetric Flame Spread between Parallel Plates of Thick Combustible Solid

ABSTRACT To identify the occurrence conditions of a symmetry-breaking phenomenon, numerical simulations of flame spread along parallel, combustible plates are performed. Two-dimensional, time-dependent conservation equations for gas-phase with a one-step global reaction coupled to one-dimensional heat conduction for the solid-phase are simultaneously solved. The flame spread having two leading edges was successfully simulated and the behaviors were examined under various flow velocities and channel heights. Based on the time histories of the leading edges, the simulated flame behaviors are distinguished into three modes: symmetric, asymmetric and oscillation, in addition to the extinction. The occurrence conditions of those modes are summarized. The results indicate that the local extinction caused by an excess of the scalar dissipation rate is a key process of the symmetry-breaking. Since coexistence of flames in narrow channel is unstable, the local extinction occurs to achieve a stable state for the system to burn.

A computational framework for interface-resolved DNS of simultaneous atomization, evaporation and combustion

A computational framework for interface-resolved direct numerical simulations (DNS) of simultaneous atomization, evaporation and combustion process is proposed. The present work utilizes a level set method to implicitly capture the gas–liquid interface and the ghost fluid method (GFM) to accurately address jump conditions across the interface. Specific care has been devoted to the discretization of the convective term and diffusive term for the species and energy equations. The level set method with a sub-cell resolution of the interface is employed and a semi-Lagrangian scheme for the discretization of the level set equation with an evaporation source term is proposed. The one-step global reaction model of n-heptane is used for the vapor combustion. To the best of our knowledge, this is the first computational framework that has the capability to simulate spray combustion with an interface-resolved method. The present framework has been validated in several cases, including the one-dimensional evaporation and the static droplet evaporation for low ambient temperature, the Stefan problem, the Sucking problem, the evaporation of static and moving droplet for high ambient temperature, and the combustion of static and moving droplet. Finally, the integrated simulation of droplet collision and combustion is performed to evaluate the accuracy and robustness of the present method.

Numerical investigation of a combined solid fuel scramjet combustor

A new scramjet configuration using solid fuel as propellant is proposed, namely, the combined solid fuel scramjet. The combined solid fuel scramjet combustor has been investigated numerically to predict its characteristics. Two-dimensional axisymmetric Reynolds-averaged Navier–Stokes equations and species transport equations are solved numerically. Turbulence closure is achieved using the shear stress transport k-ω model. Three global one-step reaction mechanisms are used in this study. The experimental data in the published literature has been used to validate the accuracy of numerical model. The results of the numerical analysis show that secondary combustion occurs in the supersonic combustor. At the combustor outlet, the total pressure loss is about 0.65 and the combustion efficiency is about 48%. A subsonic recirculation zone is formed near the wall between the air inlet and the fuel-rich gas inlet, which is beneficial to mixing and flame holding. A normal shock wave is generated at the end of the expansion zone after the fuel-rich gas is injected into the combustor, and this is due to the strong pressure downstream induced by secondary combustion.

A Control-Oriented Model for Trajectory-Based HCCI Combustion Control

Previously, the authors have proposed the concept of piston trajectory-based homogeneous charge compression ignition (HCCI) combustion control enabled by a free piston engine (FPE) and shown its benefits on both engine thermal efficiency and emissions by implementing various piston trajectories. In order to realize the HCCI trajectory-based combustion control in practical applications, a control-oriented model with sufficient chemical kinetics information has to be developed. In this paper, such a model is proposed and its performance, in terms of computational speed and model fidelity, is compared to three existing models: a simplified model using a one-step global reaction, a reduced-order model using Jones–Lindstedt mechanism, and a complex physics-based model including detailed chemical reaction mechanisms. A unique phase separation method is proposed to significantly reduce the computational time and guarantee the prediction accuracy simultaneously. In addition, the paper also shows that the high fidelity of the proposed model is sustained at multiple working conditions, including different air-fuel ratios (AFR), various compression ratios (CR), and distinct piston motion patterns between the two end positions. Finally, an example is presented showing how the control-oriented model enables real-time optimization of the HCCI combustion phasing by varying the trajectories. The simulation results show that the combustion phasing can be adjusted quickly as desired, which further demonstrates the effectiveness of the piston trajectory-based combustion control.

Comparison of Numerical Combustion Models for Hydrogen and Hydrogen-Rich Syngas Applied for Dry-Low-Nox-Micromix-Combustion

The Dry-Low-NOx (DLN) Micromix combustion technology has been developed as low emission combustion principle for industrial gas turbines fueled with hydrogen or syngas. The combustion process is based on the phenomenon of jet-in-crossflow-mixing (JICF). Fuel is injected perpendicular into the air-cross-flow and burned in a multitude of miniaturized, diffusion-like flames. The miniaturization of the flames leads to a significant reduction of NOx emissions due to the very short residence time of reactants in the flame. In the Micromix research approach, computational fluid dynamics (CFD) analyses are validated toward experimental results. The combination of numerical and experimental methods allows an efficient design and optimization of DLN Micromix combustors concerning combustion stability and low NOx emissions. The paper presents a comparison of several numerical combustion models for hydrogen and hydrogen-rich syngas. They differ in the complexity of the underlying reaction mechanism and the associated computational effort. The performance of a hybrid eddy-break-up (EBU) model with a one-step global reaction is compared to a complex chemistry model and a flamelet generated manifolds (FGM) model, both using detailed reaction schemes for hydrogen or syngas combustion. Validation of numerical results is based on exhaust gas compositions available from experimental investigation on DLN Micromix combustors. The conducted evaluation confirms that the applied detailed combustion mechanisms are able to predict the general physics of the DLN-Micromix combustion process accurately. The FGM method proved to be generally suitable to reduce the computational effort while maintaining the accuracy of detailed chemistry.

The effect of heat release on the entrainment in a turbulent mixing layer

Direct numerical simulations of a temporally evolving compressible reacting mixing layer have been performed to study the entrainment of the irrotational flow into the turbulent region across the turbulent/non-turbulent interface (TNTI). In order to study the effects of heat release and interaction of the flame with the TNTI on turbulence several cases with different heat release levels,$Q$, and stoichiometric mixture fractions are chosen for the simulations with the highest opted value for$Q$corresponding to hydrogen combustion in air. The combustion is mimicked by a one-step irreversible global reaction, and infinitely fast chemistry approximation is used to compute the species mass fractions. Entrainment is studied via two mechanisms: nibbling, considered as the vorticity transport across the TNTI, and engulfment, the drawing of the pockets of the outside irrotational fluid into the turbulent region. As the level of heat release increases, the total entrained mass flow rate into the mixing layer decreases. In a reacting mixing layer by increasing the heat release rate, the mass flow rate due to nibbling is shown to decrease mostly due to a reduction of the local entrainment velocity, while the surface area of the TNTI does not change significantly. It is also observed that nibbling is a viscous dominated mechanism in non-reacting flows, whereas it is mostly carried out by inviscid terms in reacting flows with high level of heat release. The contribution of the engulfment to entrainment is small for the non-reacting mixing layers, while mass flow rate due to engulfment can constitute close to 40 % of the total entrainment in reacting cases. This increase is primarily related to a decrease of entrained mass flow rate due to nibbling, while the entrained mass flow rate due to engulfment does not change significantly in reacting cases. It is shown that the total entrained mass flow rate in reacting and non-reacting compressible mixing layers can be estimated from an expression containing the convective Mach number and the density change due to heat release.

Numerical investigation of pyrolysis effects on heat transfer characteristics and flow resistance of n-decane under supercritical pressure

Pyrolysis of hydrocarbon fuel plays an important role in the regenerative cooling process. In this article, a Two-Dimensional (2D) numerical model is proposed to investigate the pyrolysis effects on the heat transfer characteristics and flow resistance of n-decane under supercritical pressure. The one-step global pyrolytic reaction mechanism consisting of 19 species is adopted to simulate the pyrolysis process of n-decane. The thermophysical and transport properties of the fluid mixture are computed and incorporated into the numerical model for simulation. Comparisons between the current predictions and the open published experimental data are carried out and good agreement is achieved. In order to better understand the complicated physicochemical process, further investigations on the turbulent flow and heat transfer coupled with pyrolysis in a tube have been performed under various operating conditions. The results indicate that the pyrolysis intensively takes place in the high fluid temperature region. The occurrence of the heat transfer deterioration would lead to increasing n-decane conversion at the beginning of the heated section. It is found that the pyrolysis could improve the heat transfer deterioration and promote the heat transfer enhancement. Meanwhile, pyrolysis gives rise to an abrupt increase of flow resistance. The mechanisms of the physicochemical phenomena are also analyzed in a systematic manner, which would be very helpful in the development of the regenerative cooling technology.