Thermodynamic Method Research Articles

Discovery of Deactivation Phenomenon in NiCo2S4/NiS2 Electromagnetic Wave Absorbent and Its Reactivation Mechanism.

Over the past century, extensive research has been carried out on various types of microwave absorption (MA) materials, primarily emphasizing mechanism, performance, and even toward smart device. However, the deactivation, a crucial concern for practical applications, has long been long-neglected. In this work, an in-depth exploration of the deactivation mechanism reveals a significant competition between metal and oxygen, leading to the replacement of the S-M (M = Ni and Co) bond by a new S─O bond on the surface of absorber. This substitution initiates a series of collapse effect that introduces additional defective sites and diminishes the potential for charge transport. Subsequently, passive and active anti-deactivation strategies are developed to target the deactivation. The passive strategy involved intentionally creating electron-deficient structures at the initial Ni and Co sites in the crystal through the Fe doping engineering, with the objective of preventing the generation of S─O bonds. Furthermore, the active anti-deactivation strategy allows for the precise control of absorber deactivation and reactivation by employing accelerated thermodynamic and kinetic methods, enabling a reversible transformation of S-M through competitive reactions with S─O bonds. Finally, a fast deactivation and reactivation method is first proposed promising to stimulate further innovations and breakthroughs in practical applications.

Mechanochemical synthesis, purification, and optimization studies of Cr boride@MgO particles

Chromium boride, an advanced ceramic material, is commonly produced by powder metallurgy methods using elemental boron and chromium powder, borothermic reactions, or boron carbide reduction of Cr2O3. In this study, a mechanochemical method for the production of chromium boride was developed, subsequent purification was performed, and the whole process was optimized. The amounts of Cr2O3, B2O3, and Mg in the initial powder blends were determined by computational thermodynamic methods based on their equilibrium compositions. Firstly, stoichiometric starting-powder blends were milled at different durations (1, 2, 3, 4, 5, and 8 h). The optimum purification route was determined using acid leaching experiments carried out with different acids, at different temperatures, and concentrations. Secondly, powders prepared in excess amounts were synthesized at the optimum duration (5 h) and leaching condition (0.1 M HCl, 25 °C). For the 100 wt % excess B2O3, 25 wt % excess Mg and 0.8 moles of Cr2O3 composition, annealing was conducted at 1100 °C. Characterization studies, X-ray diffractometry (XRD), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), transmission electron microscopy (TEM), and atomic absorption spectroscopy (AAS) were conducted on the milled and leached powders. After annealing, CrB, CrB2, Cr3B4 and MgO phases were obtained in the XRD patterns. The particle sizes of the resulting materials were also analyzed, and it was found to be nearly 3.11 μm after annealing. Finally, the TEM analysis revealed that the MgO peak evident in the XRD patterns was MgO shell covering the Cr boride particles having submicron sizes; hence, a pure Cr boride@MgO core-shell structure was obtained.

Increasing oil absorption in bearings as a result of ultrasonic exposure to ultrafine particles

The article proposes an approach that ensures an increase in oil absorption by bearings as a result of ultrasonic exposure to ultrafine particles. The approach is based on the method of thermodynamics and kinetics of the formation of inorganic ultrafine particles in liquid-phase processes. The work shows that one of the promising ways to improve the antifriction characteristics of bearing materials is the impregnation of porous hardened materials with oils with the addition of special solid carbon additives. The goal of the work is to develop an antifriction self-lubricating powder material that meets modern requirements for bearing units. The cavitation method is considered taking into account the impact action of liquid microjets. In this case, the ratio of the sizes of the cavitation bubble and the solid particle is taken into account. An increase in the effectiveness of the influence of ultrasonic waves on the oil absorption of the bearing material has been shown.

THERMODYNAMIC PROPERTIES OF COMPLEX COPPER CHALCOGENIDES REVIEW

Complex copper-based chalcogenides are a significant environmental-friendly functional material that has great application potential due to their interesting thermoelectric, photoelectric, optical, and other properties, as well as their ionic conductivity. Analysis of numerous studies shows that improving the application characteristics of these compounds is associated with manipulating their structure and composition. An effective solution for optimizing such processes requires their in-depth thermodynamic analysis, which requires reliable data on the fundamental thermodynamic characteristics of the corresponding compounds. This review summarizes the results of researches, including ours works, on the thermodynamic properties of copper chalcogenides with some p1 -p 3 elements. The majority of these works were carried out using various modifications of the electromotive force (EMF) method. Planning of experiments carried out by this equilibrium method of chemical thermodynamics and processing of their data is impossible without the presence of reliable data on phase equilibria. Taking this into account, in addition to thermodynamic data, the work also presents the solid-phase equilibria diagrams for a number of systems studied by the EMF method. The analysis showed that for the Cu-Tl-X, Cu-Ge(Sn)-X (X-S, Se, Te) and Cu-As(Sb, Bi)-S(Se) ternary systems there are mutually consistent data on the phase equilibria and thermodynamic functions of the ternary compounds. For the Cu-Tl-X and Cu-Sn-Se systems, the thermodynamic functions of ternary compounds are obtained by two modifications of the EMF method by determining the partial molar functions of two different components - copper and thallium (tin). The thermodynamic properties of copper chalcogenides with gallium, indium, and silicon have not been extensively researched, and the data that is available is inconsistent.

Evaluation of a green methanol production system using the integration of water electrolysis and biomass gasification

For a long time, the development of green shipping has been highly valued by countries and organizations. Biomass gasification-based green methanol is seen as a long-term alternative to conventional shipping fuel to reduce greenhouse gas emissions in the maritime sector. While the operational benefits of renewable methanol as a marine fuel are well-known, its cost and environmental performance depend largely on the production method. In this study, a green methanol production system based on the integration of biomass gasification and water electrolysis is proposed and evaluated via the parametric and thermodynamic analysis methods. The water electrolysis is used to increase the hydrogen content in syngas, thereby increasing the production of methanol. The results show that as the S/C ratio increases, the mass flow rate and the calorific value of product gas, the mole flow rate of methanol decreases. The enhancement of the H2/CO ratio can increase the mole fraction of H2, thereby increasing the methanol yield. The mole flow rate of methanol dramatically increases from 925.0 kmol/h to 3725.2 kmol/h. Additionally, the mole flow rate of methanol in the proposed system is 10776.0 kmol/h, larger than the traditional system of 3603.4 kmol/h. The carbon element conversion rate of the proposed system is 94.6%, higher than the 31.5% of the traditional system. This system can significantly provide an efficient green methanol production method for the shipping sector, while also helping to find a feasible solution for the consumption of renewable energy.

Vapor-Liquid Equilibrium Measurement of Systems Containing Glycerol for Separation Process of Glycerol as a By-Product of Biodiesel

The most popular technique to produce biodiesel were uses alcohol as a catalyst to transesterify triglycerides. The biodiesel transesterification process has a by-product in the form of glycerol which has a high selling value. Equilibrium data of glycerol and alcohol mixtures is limited in equilibrium conditions and systems which causes the glycerol purification process may not be designed and operated optimally. This research aims to obtain experimentally isobaric vapor-liquid equilibrium of methanol + glycerol binary system at 31.3, 61.3, and 100.8 kPa. A modified Glass Othmer-Still was utilised to carry out the experiment. Refractometer index type Bausch and Lomb ABBE was used to examine the equilibrium composition of the liquid and vapor phases. Using the L-W thermodynamic consistency test method, the experimental data used in this work were shown to be thermodynamically consistent. The experimental data were correlated well with the Wilson, Non-Random Two Liquid (NRTL), and Universal Quasi-Chemical (UNIQUAC) models with absolute average deviation in temperatures (AADT) and that in vapor compositions (AADy) smaller than 0.3% and 0.2%, respectively. The Universal Chemical Functional Group Activity Coefficient (UNIFAC) in predicting VLE the system studied showed good performance giving AADT and AADy smaller than 7.4% and 0.04%, respectively.

CRITERION METHOD FOR MODELLING THERMODYNAMIC INSTABILITY IN MIXING HEATERS OF TURBO INSTALLATIONS

The relevance of the issue of modelling the conditions and consequences of thermodynamic instability in mixing heaters is confirmed by the analysis of the experience of operating turbo installations and the problem of hydrodynamic shocks and their impact on the functioning of the equipment. A thermodynamic mathematical model of heat and mass transfer processes in the volume of mixing heaters has been developed, which, unlike known approaches, takes into account the influence of fluctuating deviations of thermodynamic parameters from the equilibrium state on the conditions of thermodynamic instability. The analysis of the obtained criteria and conditions of thermodynamic instability and hydrodynamic shocks was carried out. Based on the developed model, an original method of determining the conditions and consequences of thermodynamic instability in the volume of mixing heaters is presented. The criterion of thermodynamic instability in the developed method defines the conditions of simultaneous change of pressure and mass in the two-phase volume of the mixing heater. The conditions for the occurrence of thermodynamic instability in mixing heaters are determined, which significantly depend on the ratio of steam and condensate flow rates. The results obtained in the work can be applied for: development of systems for diagnosing the state of mixing heaters based on the regularly controlled parameters of the turbo installation, substantiating technical solutions for preventing thermodynamic instability and hydrodynamic “shocks” on the design of heaters, substantiating technical solutions for modernization of turbo installation systems. These issues determine the need for further analysis of the feasibility of modernizing thermodynamic instability modelling methods in mixing heaters of NPP turbo-installations. Keywords: thermodynamic instability, mixing heaters of turbo installations

Calculation of Melting Temperature Using Nonequilibrium Thermodynamic Integration Methods

AbstractMelting temperature is a fundamental material property and is defined as the temperature at which the solid and liquid phases have the same free energy. However, there is no systematic study employing atomic simulations to calculate melting temperature using this definition. Here, molecular dynamics simulations and nonequilibrium thermodynamic integration methods are combined to calculate the melting temperature of Al and Cu. Results show that to accurately obtain the melting temperature, the model size should be considered carefully because the free energies of both solid and liquid phases are inversely proportional to the model size, causing a model size dependence on the calculated melting temperature. In addition, the melting temperature for various (semi‐) empirical potential models for Al and Cu is calculated and verified against experimental values to provide guidelines for the choice of potential models for simulation‐based problems relevant to the solid–liquid phase transformation.

Массопроводность дисперсных и листовых материалов в условиях термодинамического равновесия

The intensification of drying of wet capillary-porous bodies and their structural and deformation transformations is determined by the internal mechanism of moisture transfer in the material being dried. The scientific papers of A.V. Lykova, S.P. Rudobashty, B.S. Sazhina, E.N. Ochneva, N.V. Churaeva are devoted to the study of mass conductivity of various bodies. They confirm the importance to determine the characteristics of internal moisture transfer in the form of liquid and vapor to calculate the intensity of moisture exchange between the surface of a wet material and the coolant and to establish the ratio of moisture and heat flows not only during the drying process, but also during storage of materials. For dispersed and sheet capillary-porous materials of different composition and porous structure, determining the intensity of internal moisture transfer during their interaction with the environment is a relevant area of the research. It determines the drying method, thermal treatment conditions and energy efficiency. Dispersed and sheet capillary-porous materials of various shapes, sizes, structures, and humidity have been used as the objects of the study. To determine the mass conductivity parameters of a wet body during its interaction with a coolant, a thermodynamic method is used. It is based on the use of experimental desorption isotherms and calculated parameters characterizing the porous structure of the material. The authors have applied the method to calculate the mass conductivity coefficients of dispersed and sheet materials based on experimental data obtained under conditions of thermodynamic equilibrium of a wet body and gas. Calculated curves of the dependence of effective mass conductivity coefficients and the moisture content of the dried material are obtained considering environmental parameters. The data obtained on the patterns and the changes in mass conductivity coefficients makes it possible to establish the types of relationships between moisture and the material with the mechanisms of its transfer for a number of dispersed and sheet bodies. The data obtained can be used for the kinetic calculation of the drying process and to determine the conditions of their storage, as well as to identify the conditions for increasing the energy efficiency of dryers with convective supply.

Uniqueness of Nanoscale Confinement for Fast Water Transport: Effect of Nanotube Diameter and Hydrophobicity.

Inspired by the enhanced water permeability of carbon nanotubes (CNTs), molecular dynamics simulations were performed to investigate the transport behavior through nanotubes made of boron nitride (BNNT), silicon carbide (SiC), and silicon nitride (SiN) alongside carbon nanotubes (which have different hydrophobic attributes) considering their implication for reverse osmosis (RO) membranes under different practical environments. According to our findings, not only do CNTs but also other kinds of nanotubes exhibit transition anomalies with increasing diameter. Utilizing the robust two-phase thermodynamic (2PT) methods, the current examinations shed light on thermodynamic origin of favorable water filling of these nanotubes. The results show that regardless of the nanotube material, the filling of water inside small nanopores (d < 10 Å) as well as within pores of diameter larger than 15 Å will always be favored by the entropy of filling. However, the entropic preference for filling nanotubes with a diameter of 10-15 Å depends on the constituent material. In particular, the enhancement in total entropy of confined water was mainly due to the increased rotational freedom of confined water molecules. The thermodynamic origin of water transport was correlated with the structural and fluidic behavior of water inside these nanotubes. The observed data for density, flow, structure correlation functions, water-water coordination, tetrahedral order parameter, hydrogen bonds, and density of states functions quantitatively support the observed entropy behavior. Of critical importance is that the present study demonstrates the effectiveness of RO filtration using nanotubes of boron nitride rather than carbon. Furthermore, it was found that one should avoid the use of silicon nanotubes unless filtration needs to be performed under harsh environments where nanotube of other materials cannot survive. Specifically, the results show that both the structural and dynamic properties of water confined in BNNTs are similar to those of CNT's, and for SiNT it is similar as SiC. Our results show that besides the nanotube material, the chirality index of the nanotube also plays a significant role in determining the structure, dynamics and thermodynamics of confined water molecules.

Cerium Addition Improves Cleanliness and Refines Microstructure of As‐Cast High‐Nitrogen Stainless Bearing Steel

High‐nitrogen stainless bearing steel (HNSBS) is the most representative third‐generation aviation bearing steel, and the cleanliness and microstructure characteristics of bearing steel are crucial to its high performance and long service life. In this work, the effect of cerium addition on the cleanliness and microstructure characteristics of as‐cast HNSBS was systematically studied by combining microstructural characterization and thermodynamic analysis methods. The results show that with increasing Ce content, the cleanliness of steel first improved and then decreased, and Ce2O2S, Ce2O3 and CeN inclusions were generated successively. The Ce content should be controlled to ≈0.012 wt% to ensure that all Al2O3, MgO · Al2O3, and MnS inclusions were modified, and minimize the formation of large‐size Ce‐bearing inclusions. Furthermore, cerium addition refined the dendrite structure due to more nucleation sites for γ‐Fe and the enrichment of Ce in the liquid phase at solidifying front. The finer and more dispersed distribution in precipitates was ascribed to the reduction of growth space and Cr segregation, as well as the increase in effective nucleation sites. These results can offer theoretical guidance for inhibiting the formation of harmful inclusions in high‐nitrogen alloy systems and refining the microstructure of alloy systems containing M23(C, N)6 and M2(C, N) precipitates.

Study of the precipitation trend of asphaltenes and waxes in crude oil using computational chemistry and statistical thermodynamics methods

Asphaltenes aggregation and waxes in petroleum were simulated considering five molecular structures containing functional groups: asphaltenes, resins, and non-polar hydrocarbons in a heavy oil crude. The properties of molecules were calculated using the density functional theory. The van der Waals constants associated with the pairwise interactions and the Hamaker constants for the dispersed phase (formed by asphaltenes and waxes) and the dispersion medium (created by non-polar hydrocarbons) were estimated. Sparse pass size as a function of its composition is calculated using Qyle groups and the Young–Laplace equation. We also assessed the potential colloidal pair corresponding to the interactions between the asphaltene and resin aggregates for different dispersion media, the attractive energies between the asphaltene molecules (−60 10–20 J ≈ ) are more than twice as high as the attractive energies concerning the rest of the molecules present ( × -30–10] 10–20 ≈ × J). It is predicted that attraction energy between the aggregates decreases with the increase of the presence of resin in the dispersed phase, This is explained by the fact that the increase in the concentration n of resin can lead to a decrease in the relative size d of the aggregates by up to 90 % (for n = 0.1, d = 0.1 and for n = 0.9, d = 0.1). This decrease in aggregate size is manifested in a theoretically calculated effective viscosity reduction of up to 50 %.

Harmonic models and molecular dynamics simulations of isomorph behavior of Lennard-Jones fluids: Excess entropy and high temperature limiting behavior

Henchman’s approximate harmonic model of liquids is extended to predict the thermodynamic behavior along lines of constant excess entropy (“isomorphs”) in the liquid and supercritical fluid regimes of the Lennard-Jones (LJ) potential phase diagram. Simple analytic expressions based on harmonic cell models of fluids are derived for the isomorph lines, one accurate version of which only requires as input parameters the average repulsive and attractive parts of the potential energy per particle at a single reference state point on the isomorph. The new harmonic cell routes for generating the isomorph lines are compared with those predicted by the literature molecular dynamics (MD) methods, the small step MD method giving typically the best agreement over a wide density and temperature range. Four routes to calculate the excess entropy in the MD simulations are compared, which includes employing Henchman’s formulation, Widom’s particle insertion method, thermodynamic integration, and parameterized LJ equations of state. The thermodynamic integration method proves to be the most computationally efficient. The excess entropy is resolved into contributions from the repulsive and attractive parts of the potential. The repulsive and attractive components of the potential energy, excess Helmholtz free energy, and excess entropy along a fluid isomorph are predicted to vary as ∼T−1/2 in the high temperature limit by an extension of classical inverse power potential perturbation theory statistical mechanics, trends that are confirmed by the MD simulations.

A comparative study of thermodynamic equations and artificial neural networks in modeling the behavior of glycerol+methanol+CO2 and glycerol+ethanol+CO2 systems in biodiesel production

Classical thermodynamic methods often encounter challenges when applied to model the intricate behavior of liquid-liquid equilibria within biofuel production systems. To overcome these limitations, Artificial Neural Networks (ANNs) have emerged as a promising avenue for effectively describing such complex systems. This study developed and evaluated ANNs to predict the behavior of two key systems, glycerol+ethanol+CO2 and glycerol+methanol+CO2, employing diverse configurations and parameters. A total of 516 distinct ANNs were methodically crafted and evaluated. Notably, the Cascade Feed-Forward architecture exhibited optimal performance in predicting the CO2+glycerol+ethanol system, while the Elman networks excelled in predicting the CO2+glycerol+methanol system. The optimized ANNs were subsequently benchmarked against analogous systems in the literature by applying established thermodynamic equations. Remarkably, the results of this research work underscore the superior predictive accuracy of the ANN approach, yielding significantly diminished error values. Specifically, the mean squared error (MSE) values of 0.1283 and 0.0892 were achieved for the methanol and ethanol systems, respectively. This study contributes substantively by showcasing the ability of ANNs to surpass classical methods for accurate prediction within the intricate domain of biofuel production systems.

Synergistic effect of arsenic removal from petroleum condensate via liquid-liquid extraction: Thermodynamics, kinetics, DFT and McCabe-Thiele method

This work presents the purification of petroleum condensate by removing arsenic ions via liquid-liquid extraction (LLE). Influence of pure and synergistic extractants is investigated. In terms of the practicability, following parameters are examined: the type of extractant, operating time, and temperature. Response surface methodology is used to design parameters such as organic-aqueous ratio and extractant concentration. Under optimal conditions; a mixture of 1 mol/L HCl and 0.02 mol/L thiourea with an organic/aqueous ratio of 1:4 at 323.15 K for 60 min, the extraction of arsenic reached 78.2 %. Further, batch simulation via two-stage counter-current extraction, and estimation by McCabe-Thiele diagram proved to be enhanced arsenic extraction to 95.3 %. Analysis by FTIR show that arsenic ions in petroleum condensate are formed as triphenylarsine compound ((C6H5)3As). The process of arsenic removal proved to be zero-order endothermic, irreversible and spontaneous reaction. The results obtained from the density functional theory (DFT) confirm that arsenic ions react with the synergistic extractant: effectively forming a covalent bond (As–S).

Thermodynamic assessment of La–Fe–Si systems

The phase equilibria of the La–Fe–Si system were investigated using a combination of experimental and thermodynamic modeling methods. The isothermal cross-section of the La–Fe–Si ternary system in the (Fe, Si)-rich region at 1373 K was experimentally investigated using electron probe microanalysis (EPMA) and X-ray diffraction (XRD). Based on the experimental results and literature reports of the La–Fe–Si system, the thermodynamic model parameters of the system were optimized using the CALPHAD method. The intermediate compounds in the La–Si binary system and ternary compounds in the La–Fe–Si ternary system were described via sublattice models. The calculated thermodynamic and phase equilibria data were in good agreement with the experimental data, providing a foundation for the development of a multi-component thermodynamic database for LaFeSi-based alloys.

An innovative S–CO2 recompression Brayton system and its thermodynamic, exergoeconomic and multi-objective analyses for a nuclear spacecraft

An innovative layout of a recompression supercritical carbon dioxide (S–CO2) cycle for nuclear spacecraft was proposed in this work. Thermodynamic and exergoeconomic analysis of the innovative cycle have been performed to study the effect of essential operating parameters on the split ratio, maximum operating pressure ratio, minimum operating temperature, maximum operating temperature, and compressor C4 inlet pressure based on the first and second laws of exergoeconomics and efficiency. Finally, the innovative power cycle is optimized with high efficiencies, low cost and lightweight. The results show that the optimization progress is based on the thermodynamic and exergoeconomics method; the minimum operating temperature can significantly improve efficiencies and reduce circular investment cost; then after the multi-objective optimization progress, the thermal efficiency (ηth), exergy efficiency (ηex) and mass of Brayton turbomachinery unit (MBTU) improved by 2.71 %, 3.69 %, and 2.8 %; total capital cost rate (total) and levelized cost of electricity (LCOE) reduced by 0.88 % and 4.55 %, respectively.

FED evaluation in a small double-suction reversible pump turbine considering sediment erosion

Double-suction pump-turbines are a special type of reversible pump-turbine which serves the pumped storage hydro power plant. Enhancing the energy conversion efficiency of the power station can be effectively achieved by reducing the internal Flow Energy Dissipation (FED) within the pump-turbine. The key to addressing this challenge lies in the identification of high FED regions and conducting visualized analyses. In this study, computational fluid dynamics (CFD), thermodynamic calculation methods and the Finnie erosion model are combined to perform two-phase flow numerical simulations of a specific double-suction pump-turbine model under both pump and turbine operating modes. We analyzed the FED in different regions off wall. The energy loss distribution is provided within these five regions for the volute casing, suction chamber, and impeller separately, and conducted an analysis of component wear. The research findings revealed that, in the pump mode, FED primarily concentrates within the volute casing, while in the turbine mode, it is concentrated within the suction chamber, with both regions accounting for over 70 % of the total energy dissipation. The proportion of internal FED in five regions at varying distances from the wall for each component showed significant disparities under different operating conditions, closely related to the internal flow characteristics of the components. In pump mode, wear primarily occurs in the volute casing, while the wear in the suction chamber and impeller can be considered negligible. In turbine mode, each component experiences some level of wear. This provides a foundation for reducing flow energy losses and preventing sediment erosion.

Influence of the method of inputing a cobalt-containing emitter on the depth of the diffusion layer of chrome

The results of thermal diffusion chromium plating of samples of steel 35CrNi2-3 in technological back filling containing oxide-emitters of oxygen anions in the separating part, which create a thermionic field during heating, are presented. In one variant of saturation, powder of metallic cobalt was added to the metal part, in the second case, to accelerate diffusion processes, a cumulative lattice made of cobalt sheet was installed near the saturating surface. The saturation was carried out at a temperature of 1000 °C for 24 hours. The elemental composition of the diffusion layer was monitored using a JEOL JSM-6460LV universal scanning (scanning) electron microscope. The microhardness of the coatings was measured using an FM-800 microhardness tester. Microstructural analysis was carried out on an opti-cal microscope Axio Observer D1.m. It has been established that the presence of cobalt both in the form of a powder and in the form of a cumulative lattice contributes to the acceleration of the diffusion of chromium by 1.2–1.5 times compared with saturation without the addition of cobalt. The results obtained are experimental confirmation of the hypothesis about the mechanism of acceleration of chromium diffusion during thermal diffusion chromium plating by a thermionic flux of charged particles. The phase composition of the saturated surfaces consists of a solid solution of Cr–Fe, carbide ((Cr,Fe)7C3) and nitride ((Cr,Fe)2N and CrN) phases. Cobalt, being a non-carbide-forming element, is present in insignificant amounts in the Cr–Fe solution and does not form separate phases. It has been established that the oxide and metal components of the mixture upon heating have a complex nature of interaction, which determines the gas formation of the saturated surface and requires investigation by thermodynamic modeling methods.

Thermodynamic analysis of a high Mach number scramjet engine with secondary combustion for thrust enhancement

Intending to augment the thrust of air-breathing vehicles operating at high flight Mach numbers, especially under extreme flight conditions, this study introduced a pioneering methodology predicated on secondary combustion. This innovative scheme uses the product of combustion of hydrocarbon fuel and air to further react with metal fuel to obtain thrust gain. This study was mainly based on theoretical calculation. A preliminary parametric design and performance analysis of a Mach 8 scramjet engine with an afterburner was carried out based on the thermodynamic cycle analysis method, considering the gas component changes. The engine model design with an inward two-dimensional inlet was adopted, along with an oblique injection of hydrocarbon fuel and two combustors in series. In addition, the expansion of gas in a supersonic nozzle was modeled with quasi-one-dimensional flow equations. By maintaining an equivalence ratio of 1.0 for the hydrocarbon fuel in the primary combustor, meticulous exploration of the powder-to-gas ratio in the afterburner, ranging from 0.04 to 0.2, was conducted. Similarly, an investigation into the temperature ratio at the outlet of the inlet, spanning the range of 3.8 to 7, was performed. Through a judicious optimization process involving both the inlet compression temperature ratio and the magnesium powder's powder-to-gas ratio, the engine designed can obtain a maximum thrust gain of 57.3%. The analysis underscores the advantageous correlation between heightened powder-to-gas ratios and augmented thrust production. Setting the upper limit of the powder-gas ratio to 0.16 is recommended to maintain optimal performance. This research also provided a new idea for expanding the application of hydrocarbon fuels in higher flight Mach number scramjet engines.