Pressure Diagram Research Articles

Phase equilibria and cloud-point behavior for the poly(2-phenylethyl methacrylate) in supercritical CO2 with monomers as co-solvent

This work focuses on the non-ideal phase equilibrium of methacrylate and acetate groups with weak polar. Phase behavior measurements were performed using a synthetic method by observing the bubble-point and cloud-point in a variable volume high-pressure view cell. The cloud-point and vapor-liquid experimental data at various temperatures and several pressures are obtained for two-component and three-component mixtures of supercritical CO2 + P(2-PEMA) [poly(2-phenylethyl methacrylate)] + co-solvents [2-phenylethyl methacrylate (2-PEMA), phenyl acetate (PAe), and 2-phenylethyl acetate (2-PEAe)] and CO2 + monomers (2-PEMA, PAe, and 2-PEAe) systems. The product data for the P(2-PEMA) + co-solvents mixture under supercritical CO2 are measured at up to 474.8 K and up to 200.86 MPa. The product sources for the CO2 + P(2-PEMA) + x wt.% 2-PEMA solutions were reported in changes of the p–T (pressure vs temperature) diagram, and with 2-PEMA weight fractions of (29.7, 35.1, 39.1, 44.5, and 52.2) wt.%. To obtain a two (vapor + liquid) region and three (liquid1 + liquid2 + vapor) region, the CO2 + P(2-PEMA) + 56.0 wt.% 2-PEMA, CO2 + P(2-PEMA) + 58.2 wt.% PAe, and CO2 + P(2-PEMA) + 57.6 wt.% 2-PEAe phase segregation curve bisects a supercritical liquid region → (liquid + vapor) region at ∼410 K and ∼23 MPa (2-PEMA), ∼365 K and ∼14 MPa (PAe), and ∼385 K and 18 MPa (2-PEAe), respectively.The equilibria data for the 2-PEMA, PAe, and 2-PEAe in CO2 are a significant in determining their suitability as organic solvent in various chemical processes. The equilibrium curves of the two-component solution for 2-PEMA, PAe, and 2-PEAe in compressed CO2 are examined using a synthetic method at (313.2 ≤ T ≤ 393.2) K and pressure of p ≤ 26.66 MPa. The three CO2 + 2-PEMA, CO2 + PAe, and CO2 + 2-PEAe two-component systems have mixture-critical loci that show the highest in the (p–T) space between the Tc of CO2 and 2-PEMA, PAe, or 2-PEAe. The CO2 + 2-PEMA, CO2 + PAe and CO2 + 2-PEAe mixtures display type-I curves. The product data for the CO2 + 2-PEMA, CO2 + PAe, and CO2 + 2-PEAe binary mixtures are correlated with the Peng–Robinson equation of state by a mixing rule with adjustable parameters of kij, and ηij.

Experimental comparative assessment of butanol or ethanol diesel-fuel extenders impact on combustion features, cyclic irregularity, and regulated emissions balance in heavy-duty diesel engine

Abstract This work studies the impact of using n-butanol or ethanol in blends with diesel fuel (extenders) on combustion, cyclic irregularity, and exhaust emissions trade-off (balance). Experiments were conducted at two speeds and three loads in a fully-instrumented, six-cylinder, four-stroke, heavy-duty direct injection (HDDI), turbocharged, ‘Mercedes-Benz’ bus diesel engine. Measured combustion chamber pressures and their heat release rate diagrams provide motivating features of the combustion process. Since low-ignition quality fuels as ethanol and n-butanol may instigate unstable engine operation, this work centers also into the examination of cyclic combustion variations (irregularity) strength as mirrored in the cylinder pressure diagrams, by analyzing for maximum pressures and mean effective pressures, employing statistical analysis tools for averages and coefficients of variation. The n-butanol or ethanol diesel fuel blends present stronger cyclic variations than the corresponding neat diesel fuel cases, with the ethanol ones being a bit stronger for the same value of fuel-bound oxygen. The above results and the different physical and chemical properties of biofuels assist the elucidation of engine stability differences, as well as the balance of all measured regulated exhaust emissions: smoke, nitrogen oxides (NOx), carbon monoxide (CO), and unburned hydrocarbons (HC). Defeat of smoke-NOx and CO-HC adverse trade-offs is revealed.

Influence of Fuel Injection, Turbocharging and EGR Systems Control on Combustion Parameters in an Automotive Diesel Engine

Indicated pressure diagrams were measured during experimental campaigns on the control of fuel injection, turbocharging and hybrid exhaust gas recirculation systems in an automotive downsized diesel engine. Three-part load operating conditions were selected for four test sets, where strategies aimed at the reduction of NOX emissions and fuel consumption, limiting penalties in soot emissions and combustion noise were applied to the selected systems. Processing of in-cylinder pressure signal, its first derivative and curves of the rate of heat release allowed us to evaluate seven parameters related to the combustion centre and duration, maximum values of pressure, heat release and its first derivative, heat released in the premixed phase and a combustion noise indicator. Relationships between these quantities and engine operating, energy and environmental parameters were then obtained by referring to the four test sets. In the paper, the most significant links are presented and discussed, aiming at a better understanding of the influence of control variables on the combustion process and the effects on engine behaviour. The proposed methodology proved to be a consistent tool for this analysis, useful for supporting the application of alternative fuels or advanced combustion modes.

Artificial neural network assisted two-phase flash calculations in isothermal and thermal compositional simulations

Flash calculations are widely employed in compositional simulations in the determination of a number of phases, phase amount and phase composition at each grid block. The efficiency and robustness of a flash algorithm is critical to saving simulation run time and producing reliable simulation results. Traditional flash calculation methods that consist of a stability test and phase splitting calculations often require tremendous computational time to iteratively solve nonlinear equations. In general, the stability test is the most time-consuming part as it aims at calculating the compositions of an unstable trial phase from various empirical initial estimates. For the phase splitting calculations, their convergence behavior highly depends on the quality of initial guesses of K-values. Good initial guesses can significantly reduce the number of iterations, avoid converging to an incorrect solution and, therefore, enhance the efficiency and robustness of a flash algorithm. Conventionally, initial guesses for the phase splitting calculations come from the values at the previous time step, the neighboring grid blocks or the stability test, but sometimes they do not work well.In this work, we use artificial neural networks (ANNs) to assist the traditional flash calculations in achieving their fast and robust convergence. ANN models are built standalone prior to a simulation and can be considered as a preparation stage. Once the ANN models are successfully built, they can benefit a large number of simulation runs during history matching and production optimization. There are two ANN models developed in this work: an ANN-STAB model and an ANN-SPLIT model. The ANN-STAB model is built to fit a saturation pressure diagram and the ANN-SPLIT model is generated to regress mole fractions and K-values. At given pressure, temperature and feed composition, the ANN-STAB model is first used to label the stability of a system; if it shows instability, the ANN-SPLIT model is then used to predict the mole fractions and K-values, which are to be used as initial guesses in the following phase splitting calculations. Compared with the traditional stability test algorithms, the ANN-STAB model gives almost the same accuracy but consumes much less computational time. The ANN-SPLIT model provides thoroughly reliable initial guesses for phase splitting calculations. As a result, it requires far fewer Newton iterations.

Research on HONDA NHX 110 fueled with biogas, CNG and E85

The work presents research on HONDA NHX 110 fueled with biogas, compressed natural gas – CNG, and the mixture of bioethanol with gasoline –E85. The experiment study was conducted on the author’s test bench which contained: internal combustion engine ICE – HONDA NHX 110, electrical machine, electrical loading unit, control chain which contain NI cards and prepared application in LabVIEW software for data acquisition. In herein work, the influence of different angles of the ignition advance on value change of an indicated pressure diagram(for a single cycle and average value), the electric power value, vibration acceleration of internal combustion body for biogas have been presented. The results discussed in this work convey practical information about the vibroacoustic activity, maintenance of internal combustion engine as distribution generation source (electricity generation state) which have been powered by alternative fuels.

Effect of Reduction in Number of Data Samples on Pressure Diagram Measurement during Transient Operation

Effect of Reduction in Number of Data Samples on Pressure Diagram Measurement during Transient Operation

Estimation of strut forces for braced excavation in granular soils from numerical analysis and case histories

Construction work of many projects in urban areas requires deep braced excavations, under which circumstances, appropriate design method to assure both the safety and economy of the retaining walls and supporting systems is therefore of paramount importance. For multi-propped retaining walls, Apparent Pressure Diagram (APD) method developed by Peck (1969) is commonly adopted to determine the forces acting on the struts. Unfortunately, most previous studies focused on the performance of braced excavations in soft to stiff clays, where limited publications involve braced excavations in dense sand and gravel with medium rigid walls. In this study, both 2D and 3D finite element analyses were carried out to examine the strut forces for braced excavations in granular soils. Subsequently, based on the numerical results as well as the field measurements from a number of reported case histories, empirical charts have been proposed to determine strut loads for deep excavations in granular soils with medium rigid walls.

Shock temperature and reflectivity of precompressed H2O up to 350 GPa: Approaching the interior of planets** Project supported by the National Key Research and Development Program of China (Grant No. 2017YFA0403200) and the Science Challenge Project (Grant No. TZ2016001).

Using a combination of static precompression and laser-driven shock compression, shock temperature and reflectivity of H2O have been measured up to 350 GPa and 2.1 × 104 K. Here, two calibration standards were applied to enhance temperature measurement reliability. Additionally, in temperature calculations, the discrepancy in reflectivity between active probe beam wavelength and self-emission wavelength has been taken into account to improve the data’s precision. Precompressed water’s temperature–pressure data are in very good agreement with our quantum molecular dynamics model, suggesting a superionic conductor of H2O in the icy planets’ deep interior. A sluggish slope gradually approaching Dulong–Petit limit at high temperature was found at a specific heat capacity. Also, high reflectivity and conductivity were observed at the same state. By analyzing the temperature–pressure diagram, reflectivity, conductivity and specific heat comprehensively at conditions simulating the interior of planets in this work, we found that as the pressure rises, a change in ionization appears; it is supposedly attributed to energetics of bond-breaking in the H2O as it transforms from a bonded molecular fluid to an ionic state. Such molecular dissociation in H2O is associated with the conducting transition because the dissociated hydrogen atoms contribute to electrical properties.

Diagnostic of results of hydro-dynamical studies of reservoirs

At present, the technique of interpreting the pressure diagrams obtained in the wells logging achieved such a high level that in many qualitatively conducted hydro-dynamical studies, it is possible, in addition to the basic parameters of the reservoir permeability, hydro-conductivity, reservoir pressure and skin effect, to determine even the most important characteristics of the drainage area, such as, for example, the filtration properties of a fracture obtained during reservoir hydraulic fracturing, the presence and characteristics of the pore-fracture environment composing the reservoir, performance feature of layers and interlayers, types of reservoir heterogeneity and others.

A Study on Combustion Parameters in an Automotive Turbocharged Diesel Engine

A wide experimental database on indicated pressure diagrams measured on a turbocharged diesel engine, equipped with high and low pressure exhaust gas recirculation (EGR) circuits and a variable nozzle turbine (VNT), was processed to evaluate a large set of combustion parameters. Available data were referred to different tests in three part load operating conditions, focused on High Pressure EGR trade-off and the development of integrated control strategies for EGR and turbocharging systems aiming at NOX and fuel consumption reduction. According to their definition, combustion parameters were derived from pressure diagrams, its first derivative and heat release curves. Their calculation allowed enlarging the information content of measured in-cylinder pressure diagrams. Several linear correlations were then defined, linking engine operating, energy and environmental quantities to combustion parameters, useful for the analysis and modeling of in-cylinder processes and engine behavior. The influence of testing conditions on these relationships was also analyzed, referring to the investigated operating modes and the adoption of open and closed loop scheme for VNT management. Finally, general correlations were defined, linking NOX and soot emissions to selected quantities.

Isopiestic measurements of thermodynamic properties for the aqueous system LiBr–CaBr2–H2O at 373.15 K

The isopiestic molalities for the systems LiBr–H2O, CaBr2–H2O and LiBr–CaBr2–H2O were measured at 373.15 K with the isopiestic method using the Oak Ridge National Laboratory (ORNL) high–temperature gravimetric isopiestic apparatus. The osmotic coefficients were determined based on the lithium chloride and sodium chloride reference standards. The vapor pressure diagrams and osmotic coefficient diagrams at different mole fraction for LiBr were plotted. The calculated vapor pressure with water activities agree well with the experimental data. On the basis of Pitzer original and its extended model, the Pitzer binary parameters β(0), β(1)C(0) and C(1) for the systems LiBr–H2O and CaBr2–H2O and mixing parameters of θLi,Ca and ψLi,Ca,Br were fitted with the measured osmotic coefficients. The calculated osmotic coefficients for systems LiBr–H2O and CaBr2–H2O agree well with the experimental data. The agreement between the calculated water activities and experimental results for the ternary system indicates that the parameters obtained in this work are reliable for water activity calculation. The thermodynamic data obtained in this study are essential for development of universal thermodynamic models for brine systems containing lithium bromide and calcium bromide.

Influence of physical & chemical properties of natural and plant fuels on fuel spray process in compression ignition engine

Tests results of the fuel injection process and measurement in engine PERKINS 1104C-44 working per external velocity characteristic and feeding natural fuel and plant fuel were presented in this article. Analysis of the obtained results allowed to find differences in the course of the injection process and its combustion in engine fuelled with the above-mentioned fuels. Using fuels of different physical & chemical properties to compression-ignition engines requires high accuracy of selected parameters measurements in order to learn differences in processes of injection and combustion. Necessity of fulfilling more and more strict standards concerning emission of toxic components of exhaust gases forces users of diesel engines to possess quick and precision methods of their technical state assessment and particularly of a combustion process and of injection equipment technical state. Analysis of the fuel pressure in the injection pipe and injection nozzle lift allows for determining fuel outflow rate from the atomizer and fuel spray disintegration into droplets. Experimentally obtained indicator diagrams of cylinder pressure were also applied. The aim of the work is to evaluate, on the basis of a simple mathematical model, the parameters of a stream of atomized fuel, including plant fuels. In the calculations, the experimentally measured opening pressure of the sprayers and the lift of the sprayer needle were used.

Simulation of combustion process in the forced transport diesel engine with the prescribed law of mixture formation

There was developed a new single-zone model of the fuel combustion process, based on the equations of chemical kinetics, which takes into account in more detail the features of the internal chamber processes of internal combustion engines. The combustion process is considered as a set of successive oxidation reactions to carbon dioxide and water of groups of active fuel molecules proceeding according to the Arrhenius law. The number of active molecules of fuel entering into the reaction depends on the total number of fuel molecules, the current mixture temperature and the conditional activation energy, varying depending on the fraction of burned fuel. The conditional duration of oxidation of this group of active molecules is assumed to depend not only on the total number of fuel molecules, but also on the volume of the combustion chamber, the number of oxygen molecules, the number of molecules of inert components and turbulence inside the combustion chamber. The heat released during the oxidation of each group of active fuel molecules is determined through the lower heat of combustion of the fuel and is expended to increase the temperature and pressure of the mixture in the combustion zone. At each step of the calculation, the number of molecules of all substances is corrected as a result of fuel burn-out. A special feature of the model is the introduction of a new parameter that takes into account the time factor at the molecular level, the conventional duration of the oxidation reaction of the active molecules of the fuel. A new mathematical model is used as the basis for the algorithm for the developed program for calculating the operating cycle of an accelerated diesel engine with a prescribed law of mixture formation. Calculations of the influence of the temperature of the fresh charge after the charge air cooler on the duty cycle of the forced diesel in the range from 360 to 430 K are performed. According to the results of the calculation, it is established that the best indicator characteristics of the working cycle are reached at a temperature of 360 K. Indicator diagrams of pressure in the cylinder and the laws of heat generation, obtained by calculation correspond with known experimental data.

Finite element analysis of lateral earth pressure on sheet pile walls

Sheet pile walls providing lateral earth support are widely employed as excavation supporting systems for cutting slopes along the high-speed railway. In this study, a validated three-dimensional finite element (FE) model based on field measurements was used to explore lateral earth pressure distribution on sheet pile walls, aiming to provide guidelines and recommendations for design of the sheet pile walls. To this end, the influence of pile length, sheet's location, pile's stiffness, and soil properties on the pile performance were investigated. The results showed that the optimum pile length was about 14 m for the sheet pile walls at a China high-speed railway. The sheet's location could affect the formation of soil arching and the mechanism of earth pressure distribution. The moment of inertia of sheet pile walls was found to be effective in controlling pile displacement and earth pressure, compared to Young's modulus of the pile. Variations of soil parameters led to negligible changes in the earth pressure distribution. Furthermore, a proposed simplified straight-line form for earth pressure diagram based upon the FE analysis was developed. Compared with traditional earth pressure methods, the proposed diagram considers the sheet effect. Overall, the conducted study provided useful help toward the process of safer design and more economical sheet pile walls.

Simulations on two holes drainage for cleat coal gas

Gas drainage from seam is the main technical measure to prevent and control gas accident. The mathematical model and the numerical analysis method can be used to study the gas flow, and the more accurate results can be achieved. The LB method is a simplified computational model based on the microscopic scale and can be used for solving the problem of gas seepage. This paper based on LB method, simulated the gas pressure, flow track and speed vector diagram in terms of the topic for cleat coal gas drainage through symmetrical holes. It analyzed the depth of the holes influence the gas leakage; summarized and concluded the drainage performance under the controllable subjective factors during the cleat coal gas drainage process.

Influence Factors of Two Holes Dranage for Cleat Coal Gas

Coal occupies a very important position in the national energy strategy. Gas drainage from seam is the most effective technical measure to prevent gas accident. Mathematical model and numerical analysis method are new methods for the study of gas flow. The LB method can be used for solving the problem of gas seepage, which is a simplified computational model based on the microscopic scale. This paper based on LB method, simulated the gas pressure, flow track and speed vector diagram in terms of the topic for cleat coal gas drainage through symmetrical holes. It analyzed the position of the holes influence the gas leakage; summarized and concluded the drainage performance under the controllable subjective factors during the cleat coal gas drainage process.

Investigation on the Relationship between Wellhead Injection Pressure and Injection Rate for Practical Injection Control in CO2 Geological Storage Projects

The existing investigations on the maximum allowable wellhead injection pressure have found the upper limit of wellhead injection pressure, which, however, cannot provide a practical operational designing scheme of wellhead injection parameters for CO2 geological storage projects. Therefore, this work firstly proposes the complete constraint conditions of wellbore injection to realize the whole process of forward and inverse calculations of wellbore pressure and then applies it to explore the relationship between wellhead injection pressure and injection rate. The results show that the wellhead injection pressure and the injection rate are a pair of mutually constrained physical quantities. For a certain injection project, the allowable wellhead injection pressure and injection rate separately form a continuous interval. Change of one quantity within its allowable interval will also change the other within its interval, both jointly forming a closed region. Thus, controlling the wellhead injection parameters in this closed region can simultaneously ensure the effectiveness and safety of injection. Subsequently, this work further studies the factors of impacting the relationship between wellhead injection pressure and injection rate and finds that all the temperature of injected fluid, the parameters of saturation, and the characteristic parameters of reservoirs only change their upper and lower limits to some extent but have no essential effects on their relationship. Application of this theory and method in Shenhua CCS demonstration project obtained the relationship diagram of wellhead injection pressure and injection rate, which found that its actual injection parameters just fall into the closed region of the relationship diagram, effectively verifying the reliability of this work.

Investigating the EGR rate and temperature impact on diesel engine combustion and emissions under various injection timings and loads by comprehensive two-zone modeling

The impact of exhaust gas recirculation (EGR) on combustion and emissions in direct injection (DI) diesel engine is examined in a predominately computational study, where the influence of EGR rate and temperature at various injection timings and loads is addressed using an in-house, comprehensive, two-zone model of diesel combustion, which divides the cylinder contents into a non-burning zone (air) and another in which fuel is supplied from the injector and burned with entrained air from the air zone. The validity of model computations is assessed favorably against pertinent experimental data, such as cylinder pressure and HRR diagrams, and NO and soot emissions, generated in this laboratory with tests on experimental, single-cylinder, ‘Hydra’ diesel engine, and also with relevant literature data. Various EGR rates and temperatures at different injection timings and loads were undertaken in the analysis. The numerical results provide insight into the local combustion and emissions formation mechanisms, and improve the understanding of important parameters dictating their behavior under various operating conditions. These results may be used for optimizing the NO – Smoke trade-off and efficiency, and pave the way for discussing the implications on the use of diesel fuels with diverse properties when fueling EGR-equipped diesel engines.

The Solution of the Spatial Hydrodynamic Problem in a Wedge-Shaped Clearance

A solution of the generalized Reynolds equation has been obtained and the pressure diagrams in the two-dimensional wedge-shaped clearance have been constructed based on mathematical modeling. The obtained results allow one to take into account the influence of the width of the wedge-shaped clearance on the parameters of the hydrodynamic contact.

A method developed to calculate lateral earth pressure on a sheet pile wall with counterforts

A method has been developed for calculating the lateral earth pressure on a sheet pile wall with counterforts of various shapes – rectangular, trapezoidal with downward expansion, and trapezoidal with upward expansion. Moreover, in the design scheme, two characteristic areas are distinguished along the height of the wall – with and without a counterfort. As a result of considering the equilibrium conditions for elementary volume, equations for determining the lateral earth pressure along the height of the wall have been obtained in the considered sections. The study has produced a mathematical modeling of the system “a sheet pile wall with counterforts plus the soil environment”. Diagrams of the lateral earth pressure are considered for a sheet pile with counterforts. A quantitative evaluation of the relief action of counterforts of various shapes has been obtained.The conducted tests show that the use of counterforts in a sheet pile wall with the considered parameters reduces the pressure of the filling soil to 26 % due to the friction forces along the lateral surface of the counterforts.The introduction of the developed calculation method into engineering practice will allow designing hydraulic engineering structures such as a sheet pile wall with various shapes of counterforts. This will enable the construction of new deepwater hydraulic structures with an increased bearing capacity.