Increase In Initial Temperature Research Articles

Simulation analysis of soot formation and laminar combustion characteristics of 2,5-dimethylfuran/air at different initial pressures and temperatures

In this research, we studied the soot formation and laminar combustion characteristics of 2,5-dimethylfuran (25DMF) at different initial temperatures and initial pressures, and conducted reactive force field molecular dynamics (ReaxFF MD) simulation and dynamical simulation method with a one-dimensional laminar combustion model through CHEMKIN's PREMIXED Code. The full process of soot formation during 25DMF combustion was revealed by ReaxFF MD simulation. There are three stages from the formation of the initial ring, the growth of polycyclic aromatic hydrocarbons (PAHs) and the formation and growth of the initial soot. The growth mechanism of polycyclic aromatic hydrocarbons was mainly divided into 4 types, which were hydrogen-abstraction-C2H2-addition (HACA), carbon-addition-hydrogen-migration (CAHM), clustering of hydrocarbons by radical-chain reactions (CHRCR) mechanism and internal ring formation. For the dynamical model of 25DMF combustion, the initial temperatures (Tu) were set to 298 K, 358 K, 393 K and 423 K, and the initial pressures (pu) were set to 1 atm, 3 atm, 5 atm and 10 atm. The results showed that the laminar burning velocities (LBVs) increased along with the increase of the initial temperature. The LBVs decreased with the increase of initial pressure. Both the increase of the initial temperature and pressure led to a decrease in flame thickness. Studies on soot precursors showed that C2H2, i-C4H5, C4H2, and C6H6 shift upstream in peak molar fraction with increasing initial pressure. C4H2 and C6H6 moved downstream first, then upstream and finally downstream with the increase of initial temperature. C2H2 and i-C4H5 shifted upstream and then downstream with increasing initial temperature.

Influence of plasma inhomogeneity and ohmic heating on the nonlinear absorption of intense laser pulse in collisional magnetized plasma

AbstractThe nonlinear absorption in the interaction of an intense laser pulse with a collisional magnetized plasma is studied by considering the effects of plasma inhomogeneity, ohmic heating, and ponderomotive force. For this purpose, we obtain the plasma electron density, the effective dielectric permittivity, and the wave equation using the Maxwell and hydrodynamic equations and solve this equation by the Runge–Kutta numerical method. The results are shown that by increasing the plasma inhomogeneity, the inverse bremsstrahlung absorption coefficient is increased, and also the density ramp parameter and its sign can affect more the absorption coefficient than the temperature ramp parameter . However, when the initial electron density and temperature increase, the laser field amplitude and the absorption coefficient are increased and the spatial damping rate of the laser pulse becomes highly peaked inside the plasma. It is shown by increasing laser pulse energy, the nonlinear bremsstrahlung absorption coefficient is decreased significantly. The results also indicate that by increasing the external magnetic field, the dielectric permittivity is decreased while the laser energy spatial damping, and the absorption coefficient are increased. Moreover, it is found that by considering the ohmic heating effect, the electrons absorb further energy from the fields and consequently the nonlinear absorption is increased.

Experimental and Numerical Studies on the Explosion Characteristics of Ethanol–Air Mixtures under Aviation Conditions

As a representative renewable biofuel, ethanol can reduce mankind’s dependence on petroleum resources and the emission of greenhouse gases and other pollutants. In recent years, the application of ethanol in the aviation field has begun to be a concern of scholars. As ethanol is a flammable liquid, it is significant to study its explosion characteristics in aviation conditions from a safety perspective. In this work, at 20 kPa, the explosion characteristics of ethanol–air mixtures (concentration 6~12%) were experimentally and numerically studied under an initial temperature range of 303 K~363 K. The effects of the initial temperature and concentration on the maximum explosion pressure, maximum rate of pressure rise, explosion time, and fast burning time were analyzed. In addition, the heat loss fraction and sensitivity analysis were examined and discussed. The main conclusions are as follows: A linear relationship exists between the maximum explosion pressure and the reciprocal of the initial temperature. The maximum rate of a pressure rise appears to decrease or at least approach a constant value as the initial temperature increases. The explosion time is significantly dependent on the concentration. At a constant concentration, the proportions of heat loss are approximately constant except for 12%. In our sensitivity analysis, R1 (H + O2 <=> O + OH) was the dominant elementary reaction.

Mechanism research on the application of liquid film microencapsulation technology based on natural lotion in strengthening recycled bio‐composite wallpaper material

AbstractLow‐carbon technology is currently one of the main research directions in sustainable research. The purpose of this research is to explore environmentally friendly low‐carbon technologies to apply NL and wastes to the development of bio‐composite. This research can not only inhibit the release of toxic atmosphere from composite wallpaper materials but also propose new perspective for recycling several bulk wastes such as agricultural waste, waste plastics, and waste cooking oil. This study not only conducted an exploratory research on the degree of filling load from a vertical perspective but also conducted comparative experiments to clarify the strengthening effect of NL in a horizontal perspective. Several valuable findings are obtained through the analysis of several measurements such as mechanical performance and scanning electron microscope (SEM) morphology. The heat transfer effect between components inside the bio‐composite is enhanced by the action of NL. A better heat transfer effect can prevent heat from accumulating in local areas of bio‐composite, resulting in an increase in the overall initial pyrolysis temperature of thermogravimetric analysis (TGA) curve. It is found through experiments that when the biomass filler is excessive, the mechanical performance of the sample sharply decreased. These negative phenomena are presented in the specific form of voids and aggregates in the internal structure of bio‐composite from a microscopic perspective. Comprehensive analysis manifested that NL can suppress the negative effect of filler agglomeration and strengthen the filler/matrix interface bonding. The research also found that the type of biomass filler can affect the actual effect of NL. These findings have certain academic significance and can promote the further development of sustainable research on diversified recycle of wastes.

Flash evaporation method for improved desalination and cooling applications: An experimental study

The present study involves the experimental analysis of flash evaporation when sudden depressurization is created into a vertical cylindrical tube having a water volume range of 120 to 180 ml. During experiments, low water pool volumes are used to prevent the impact of gravity on the change of saturation temperature. The investigation is carried out by varying the initial water temperature and back pressure of the vacuum tank in the range of 65 to 80 ∘C and 11.32 to 41.32 kPa, respectively. It is observed that the evaporation rate and cooling rate are both enhanced by increasing the initial pool temperature and decreased by increasing the back pressure. It is reported that the evaporation rate is improved by 29.7 % with an increase in initial water temperature of 5 ∘C and decreases by 152 % with an increase in the back pressure of 10 kPa. It is also found that the cooling rate is improved by 21.6 % with an increase in initial water temperature of 5 ∘C and decreased by 59.2 % with an increase of water volume of 30 ml. It is clear from the visualization procedure that the degree of superheat plays a vital role in flash evaporation.

Dependence evaluation of factors influencing coal spontaneous ignition

AbstractCoal spontaneous combustion is determined by a variety of factors. Testing can describe the changes incoal spontaneous combustion with various factors, however, the dependence of spontaneous combustion on various factors is unclear. Therefore, reliability theory was used to deduce the functional relationship of the dependence of coal spontaneous combustion on various factors, and construct a model algorithm for predicting the probability of occurrence of coal spontaneous combustion, which is adopted to evaluate and rank the degree of influence of various factors on coal spontaneous combustion. Effective prevention methods are proposed by strengthening the role of the most important factors. The results show that, by taking the duration of coal heating to 150°C as the measurement standard of coal spontaneous combustion, the duration of the initial stage of coal heating increases linearly with the increase of specific heat capacity, thermal conductivity, and moisture content of coal. With the increase of oxygen concentration, oxidation rate, and initial temperature of the coal, the duration of the initial stage of coal heating decreases exponentially. With the increase of gas flow seepage velocity in the coal body, the duration of the initial heating stage changes in a parabolic manner. At the same time, the probability of spontaneous combustion decreases exponentially with the increase of specific heat capacity and moisture content of the coal. The probability of coal spontaneous combustion increases linearly with the increase of coal thermal conductivity, oxygen concentration, gas seepage velocity, and rate of oxidation. The dependence of coal spontaneous combustion probability on different factors can be expressed as follows: coal temperature > gas seepage velocity > specific heat capacity > oxidation rate > oxygen concentration > moisture content > thermal conductivity.

Investigating the effect of temperature, pressure, and inert gas on the flammability range of ethane/oxygen mixtures

The flammability limit is a critical parameter used to evaluate the risk of explosions from flammable gases and design appropriate explosion-proof measures. This study employs a combined approach of theoretical analysis and experimental determination to investigate the impact of temperature, pressure, and inert gas on the FL of ethane/oxygen mixtures in an environment of elevated temperatures and pressures. The findings demonstrate that the flammability range of ethane/oxygen mixtures progressively widens at elevated temperature and pressure conditions. At high pressures, the upper flammability limit (UFL) of ethane displays a quadratic-linear relationship with temperature, with a turning point at 200 °C. The impact of temperature and pressure on explosion risk is primarily achieved through their effect on the UFL. A new inerting capacity of added diluting gas, δ, is defined for inert gas, revealing that the inerting effect of diluting gas is enhanced under the influence of temperature or pressure. However, the inerting effect of nitrogen weakens as the initial pressure increases, while it strengthens as the initial temperature increases. The inerting effect of water vapor in the system of ethane/oxygen/nitrogen is superior to that of nitrogen. The combustion reaction kinetics of ethane and nitrogen near the UFL is influenced by high temperature, high pressure, and water vapor. The coupling effect of high initial temperature and pressure on the inerting effect of the two inert gases is less pronounced than that of single factors.

Chemical kinetic analysis on the auto‐ignition characteristics of natural gas–diesel dual‐fuel combustion under engine‐relevant conditions

AbstractWith the advent of energy crisis and stringent emission regulations, natural gas (NG)/diesel dual‐fuel engines have entered the popular view. In this paper, the accurate boundary conditions are determined by the Converge model and the transient parameters were introduced into the chemical kinetics model to make the operating conditions more closely match the actual engine operating conditions. The effects of different methane/n‐heptane ratios, initial temperatures, initial pressures, and equivalence ratios on the IDT of methane/n‐heptane fuel mixtures were analyzed using comprehensive chemical kinetic tools such as mole fraction analysis, ROP analysis, and sensitivity analysis. The IDT of methane/n‐heptane mixture decreased significantly with increasing the equivalence ratio, initial pressure, and the proportion of n‐heptane in the mixture, but the change of temperature was more complicated for the IDT. The NTC behavior of methane/n‐heptane mixture was also affected by the NTC behavior of n‐heptane. With the increase of initial temperature, the consumption of methane and n‐heptane appeared to be significantly accelerated. The peak of radicals and intermediate groups appeared earliest and had the highest radical concentration when the n‐heptane content was 30%. With the increase of initial pressure, the peak moments of the six radicals were further advanced, but the mole concentrations of O, OH, H radicals decreased significantly. This paper not only provides a reference for the design of NG/diesel dual‐fuel engines, but also provides a theoretical basis and data support for improving the ignition and initial condition setting strategies of the engines.

Influence Mechanism of Initial Concreting Temperature and Water-Binder Ratio on Hydration Rate of Fly Ash Concrete.

The hydration exothermic rate of fly ash concrete is significantly affected by the initial concreting temperature and water-binder ratio. Firstly, the adiabatic temperature rise and temperature rise rate of fly ash concrete at different initial concreting temperatures and water-binder ratios were obtained by a thermal test instrument; then, the effects of initial concreting temperature and water-binder ratio on the hydration kinetic parameters of the NG-I-D hydration process of fly ash concrete were analyzed by the theory of hydration kinetics; lastly, the effects of initial concreting temperature and water-binder ratio on chemically bound water and pore bulk of fly ash concrete during hydration were analyzed by applying a thermogravimetric analyzer and industrial CT scanning techniques. The results showed that the increase in initial concreting temperature and the decrease in water-binder ratio accelerated the rate of temperature rise, and the initial concreting temperature had a more significant effect than the water-binder ratio. During the hydration reaction, the I process was significantly influenced by the initial concreting temperature, and the D process was significantly influenced by the water-binder ratio; the content of bound water increased with the increase in water-binder ratio and age and the decrease in initial concreting temperature. The initial temperature had a significant effect on the growth rate of 1 to 3 days bound water, and the water-binder ratio had a more significant effect on the growth rate of 3 to 7 days bound water. The porosity was positively correlated with the initial concreting temperature and water-binder ratio and decreased with age, but 1 to 3 days was the key period of porosity change. Additionally, the pore size was also influenced by the initial concreting temperature and water-binder ratio.

Numerical study on the influence of temperature on CO2-ECBM

CO2-ECBM can not only improve the production of CBM, but also contribute to CO2 geological sequestration, which has multiple economic effects. In this paper, COMSOL simulation software was used to conduct numerical simulation studies on the 3# coal seams in Qinshui Basin. A fully coupled model of coal deformation, gas flow and migration, and thermal transfer was established to evaluate the effect of temperature on the production of CBM by CO2 injection. The results indicates that temperature is a key factor affecting CH4 production and CO2 storage. Increasing injection temperature can significantly accelerate the process of gas displacement and the CO2 storage is more sensitive to temperature than the CH4 production. In contrast, both the CH4 production and the CO2 storage decrease with the increase of initial temperature of coal seam and the permeability will decrease faster. With the increase of injection time, the effective influence radius of displacement increases, but the increment of influence radius decreases gradually. The lower the initial temperature of the coal seam, the larger the influence radius, the influence radius increases as a whole with the increase of time. Low Young's modulus or high Poisson's ratio can effectively increase CO2 storage and CH4 production.

Biosorption of Triphenyl Methane Dyes (Malachite Green and Crystal Violet) from Aqueous Media by Alfa (Stipa tenacissima L.) Leaf Powder.

This study includes the characterization and exploitation of an abundant agricultural waste in Algeria, Alfa (Stipa tenacissima L.) leaf powder (ALP) as a biosorbent for the removal of hazardous triphenylmethane dyes, malachite green (basic green 4) and crystal violet (basic violet 3), from aqueous media under various operating conditions in batch mode. The effect of experimental parameters such as initial dye concentration (10-40 mg/L), contact time (0-300 min), biosorbent dose (2.5-5.5 g/L), initial pH (2-8), temperature (298-328 K), and ionic strength on dye sorption was investigated. The results of both dyes show that the increase in initial concentration, contact time, temperature, and initial pH of solution leads to an increase in biosorbed quantity, unlike the effect of ionic strength. The biosorption kinetics for triphenylmethane dyes on ALP was analyzed by pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models proposed by the Weber-Morris equation. Equilibrium sorption data were analyzed by six isotherms, namely the Langmuir, Freundlich, Harkins-Jura, Flory-Huggins, Elovich, and Kiselev isotherms. The thermodynamic parameters were evaluated for both dyes. The thermodynamic results suggest that both dyes' biosorption is a typical physical process, spontaneous and endothermic in nature.

Physics of molecular deformation mechanism in 6H-SiC

Even though there have been several studies in literature of 6H SiC, a proper physics based understanding of the molecular deformation mechanisms of the material under different loading conditions is still lacking. Experimentally, the brittle nature of the material leads to difficulties associated with in-situ determination of molecular deformation mechanisms of the material under an applied load; whereas, the complex material structure along with the bonding environment prevents proper computational identification of different types of inelasticity mechanisms within the material. Molecular dynamics study (on successful verification of the interatomic potential with experimental results) of pristine single crystals of 6H SiC have been used to probe the physics of molecular deformation mechanisms of the material along with its inherent orientational anisotropy. The study elucidates the experimentally observed mechanisms of defect nucleation and evolution through a detailed analysis of radial distribution functions, x-ray diffraction as well as phonon vibrational studies of the single crystal. Studies have been presented at room temperature, initial high temperature and different types of confinement effects of the material (including hydrostatic and different biaxial loading cases). The confinement resulted in an increase in stress and stiffness whereas increase in initial temperature resulted in a decrease compared to uniaxial stress loading conditions at room temperature.

Developing Reprocessable shape memory thermosetting resins with high thermal resistance and strength through building a crosslinked network based on bismaleimide and epoxy resins

AbstractIt is difficult to endow reprocessable shape memory thermosetting resins with outstanding heat resistance and high mechanical strength. Herein, a new kind of reprocessable shape memory thermosetting resins (DBE) are developed through building a crosslinked network based onN,N′‐4,4′‐diphenylmethane bismaleimide (BDM), bisphenol A epoxy resin and 4,4′‐dithiodiphenylamine. The influence of the composition of DBE resins on their structure and comprehensive properties was studied. Results show that DBE resins have multiple phase structures. With the increase of BDM content of DBE resin, the glass transition temperature (Tg), initial thermal decomposition temperature and flexural modulus increase, the impact strength and reprocessing efficiency decrease, while the flexural and tensile strengths increase initially and then decrease. 0.8DBE cannot be reprocessed, while 2DBE, 1.5DBE and 1DBE are reprocessable, and also have good shape reconfiguration and shape memory performances. Among them, 1DBE has the best integrated performance, which has attractively highTg(210°C), high tensile strength (76 ± 3.2 MPa), good reprocessability and excellent shape memory performance, its shape fixation rate and shape recovery rate reach 100% and 99.6%, respectively, overcoming the bottleneck problems of low heat resistance and insufficient mechanical strength of existing reprocessable shape memory thermosetting resins.

Multimodal Characterization of Crystal Structure and Formation in Rubrene Thin Films Reveals Erasure of Orientational Discontinuities

AbstractMultimodal multiscale characterization provide opportunities to study organic semiconducting thin films with multiple length scales, across multiple platforms, to elucidate crystallization mechanisms of the various microstructures that impact functionality. With polarized scanning transmission X‐ray and 4D‐scanning transmission electron microscopy, hybrid crystalline structures in rubrene thin films in which large crystalline domains surround a common nucleus and transition to a spherulite morphology at larger radii is observed. These high‐resolution techniques reveal how azimuthal orientational discontinuities at smaller radii are erased as spherulite morphology takes hold. In situ crystallization in the films with optical microscopy is also captured, discovering the importance of considering the initial temperature increase of a film during thermal annealing over the crystallization timescale. This kinetic information of the radial crystallization rate and of corresponding film heating kinetics is used to estimate the temperature at which the larger crystalline regions transition into a spherulite. By combining the results obtained from the different characterization modes, it is learned that thermal conditions can sensitively affect the crystallization of rubrene and other organic thin films. The observations suggest opportunities for more complex temperature‐dependent processing to maximize hybrid structures’ functionality in organic thin films and demonstrate that multimodal studies deepen the understanding of structure‐function dynamics.

Effect of ethanol on auto-ignition characteristics and laminar burning velocity of gasoline under elevated temperature and pressure

Gasoline and its surrogate fuels have developed rapidly in recent years, and the study of the theory of multi-fuel mixed combustion is vital to the improvement of power machines. On the basis of the important role of ethanol-gasoline mixtures in oxygenated alternative fuels, Cai and Pitsch’ s mechanism was selected for a numerical study to research the important role of ethanol with respect to combustion of gasoline from a chemical kinetic perspective. It is found that the addition of ethanol accelerates the LBV and shortens the IDTs of gasoline, and the LBV of ethanol-gasoline mixtures goes up as both the initial temperature and the ethanol ratio rise, while the LBV of ethanol-gasoline mixtures declines as the initial pressure increases. The IDTs of ethanol-gasoline mixtures tend to decrease as the initial temperature, ethanol ratio and initial pressure increase. The addition of ethanol increases the production of the intermediates CH3, HCO and CH2O, and the reactive radicals in the system increase with the addition of ethanol. In addition, the addition of ethanol can lead to an earlier surge of OH groups. This study is not only helpful for the design of ethanol-gasoline power engines, but also promotes the development of alternative fuels.

Study on Laminar Combustion Characteristics of Ammonia/ Hydrogen Premixed Based on Chemical Reaction Kinetics

The combustion characteristics of ammonia/hydrogen premixed laminar flow and the effect of hydrogen on the combustion performance of ammonia fuel were studied. First, the corresponding model of ammonia/ hydrogen premixed laminar combustion is established by using GRI3.0 mechanism, Konnov mechanism, Mei mechanism, Okafor mechanism, and Otomo mechanism respectively. Second, the simulation results are compared with the experimental results. It is found that the Mei mechanism and Okafor mechanism are more suitable for ammonia/ hydrogen premixed laminar combustion. On this basis, the effects of equivalent ratio, hydrogen ratio, and initial temperature on laminar flame velocity, maximum combustion temperature, and NO mole fraction were studied. The results show that the laminar flame velocity, the maximum combustion temperature, and the mole fraction of NO first increase and then decrease with the increase of the equivalent ratio, and the laminar flame velocity reaches the maximum when the equivalent ratio is 1.1. At the same time, with the increase of hydrogen ratio and initial temperature, the maximum combustion temperature increases first and then decreases. The mole fraction of NO increased with the increase of hydrogen ratio and initial temperature. The results show that mixing hydrogen in ammonia can improve the combustion characteristics of ammonia.

Exploring influence of MgO/CaO on crystallization characteristics to understand fluidity of synthetic coal slags

The crystallization has significant influence on fluidity of slag and slag discharge of entrained-flow-bed (EFB) gasifier. The crystallization characteristics and fluidity of five synthetic slags with different MgO/CaO ratios prepared on the basis of the range of oxide contents of Zhundong coal ash were investigated in this study. The results show that with the MgO/CaO ratio increase, the initial crystallization temperature increases, and the main temperature range of crystallization ratio growth moves to higher temperature range gradually which causes Tp25 (Tp25 is the temperature corresponding to the viscosity of 25 Pa·s) to increase. Mg-rich crystals are formed preferentially than Ca-rich crystals when adding the same amount of MgO and CaO during cooling. The effective slagging operating temperature range decrease from 217 °C for the slag with a 0:4 MgO/CaO ratio to 44 °C for the slag with a 4:0 MgO/CaO ratio with the MgO/CaO ratio increase. The slags with 2:2 and 1:3 MgO/CaO ratios show similar effective slagging operating temperature range, Tp25 and the temperature corresponding to the viscosity of 2 Pa·s. However, compared with the slag with a 1:3 MgO/CaO ratio, the crystallization ratio and rate of slag with a 2:2 MgO/CaO ratio are lower within lower temperature range (1300–1200 °C), causing its lower critical viscosity temperature and wider actual operating temperature range. Of the five slags, the widest effective slagging operating temperature range and the lowest Tp25 of the slag with a 0:4 MgO/CaO ratio due to its low crystallization ratio, and wider actual operating temperature range of the slag with a 2:2 MgO/CaO ratio make the two slags suitable for slag discharge of EFB gasifier.

The effect of mixing and heat transfer on regression rate of TAGN-based fuel in a segregated AP/TAGN solid motor

The effect of mixing and heat transfer on regression rate of TAGN-based fuel of a segregated AP/TAGN solid motor is studied in the present study. A regression rate model of TAGN-based fuel under coupled combustion is developed and validated based on detailed reaction mechanism. The two-dimensional mixing characteristics in boundary layer and the effect on regression rate of TAGN-based fuel are analyzed in detail. The simulation results show that the increase of initial temperature of oxidizer gas leads to better mixing in the axial direction and higher temperature of burning surface. However, the mass concentration of O2 decreases greatly due to the increasing consumption by primary combustion reactions of AP-derived gaseous species. Therefore, the regression rate of burning surface decreases slightly. With inflow Mach number increasing from 0.32 to 0.75, mixing in the boundary layer is greatly enhanced. Therefore, both the temperature and regression rate increase with inflow Mach number. As pressure increases from 4 MPa to 10 MPa, the primary reactions of AP-derived gas species are also enhanced. Therefore, the mass concentration of O2 decreases rapidly, which leads to oxygen-lean combustion in the combustion chamber. Therefore, the temperature of burning surface decreases while the regression hardly varies despite of the better mixing near the burning surface at high pressure. The results show that the coupled combustion reactions between inflow oxidizer gas and fuel gas mainly occur in a narrow belt-like region of the boundary layer. The results show that the regression rate of solid fuel in the segregated solid motor is controlled by the competition between primary combustion and coupled combustion.

Numerical study of the effect of CO2/H2O dilution on the laminar burning velocity of methane/air flames under elevated initial temperature and pressure

AbstractDiluents have an essential effect during combustion. Discovering the influence of CO2 and H2O as diluents on laminar burning velocity (LBV) is helpful for combustion control and optimization. In this study, CH4/air/CO2/H2O mixtures were investigated and validated using the FFCM‐Mech 1.0 over extensive boundary conditions. The chemical effects of the diluents CO2 and H2O were separated using a decoupling method. It was found that an increase in initial temperature promotes the chemical effects, while an increase in initial pressure does the opposite. In addition, the inhibiting effect of CO2 on LBV is stronger than that of H2O. Sensitivity, mole fraction, and rate of production (ROP) analyses were used to reveal that the sum of the chemical effects of adding CO2 and H2O separately was greater than the chemical effects of adding equal amounts of CO2 and H2O simultaneously. This paper not only investigates the effect of CO2 and H2O on the LBV under wide boundary conditions, but also offers a valuable guide for studying the operating conditions and intensity settings of exhaust gas recirculation (EGR) and theoretical guidance for further research on the combination of EGR and in‐cylinder water injection technology.

EXERGY ANALYSIS OF AN OPEN-MODE ADSORPTIVE HEAT STORAGE UNIT BASED ON COMPOSITE ADSORBENT ‘SILICA GEL – CRYSTALLINE HYDRATE’

Exergy analysis of an open-mode adsorptive heat storage unit has been performed when a composite ‘silica gel – crystalline hydrate’ used as an adsorbent. The crucial factors affecting the exergy efficiency factor are stated to be temperature and initial humidity of airflow supplied to the inlet of adsorbent layer, temperature of external air and methods of air flow humidification. Procedure of calculation of the operating characteristics of an open-mode adsorptive heat storage device was further developed. The suggested procedure involves determination of adsorption, specific adsorption heat and final airflow temperature, useful heat, heat inputs for operating heat storage device and its efficiency factor, then exergy recovered, exergy supplied and exergy efficiency are calculated. Exergy efficiency depends on characteristics of flow of humid air fanned into the adsorbent layer such as temperature and initial absolute humidity which strongly affect the adsorption and final airflow temperatures. Increase of initial temperature of the humid air leads to decreasing of the exergy efficiency. Maximal values of exergy efficiency are determined at the absolute humidity and temperatures of initial airflow within the ranges of 0.03 – 0.04 kg/m3 and 20 – 30ºC, respectively. These characteristics are corresponded to the maximal airflow temperatures after passing through the adsorbent layer which meet to the Sanitary Regulations. Dependence of exergy efficiency vs. external air temperature and initial airflow temperature is shown. The exergy efficiencies of the open-mode adsorptive heat storage unit with steam and ultrasonic humidification were compared. Ultrasonic humidification is shown to allow increasing the exergy efficiency by 7 % against steam humidification. The obtained results can be used when energy-efficient heat and ventilation systems for residential premises developed.