Experimental Pressure Values Research Articles

Field ionization intensity used to measure local pressure in gas flows

A coaxial ion source produces an ion beam via field effect in a gas flow through a coaxial microchannel structure. Measuring the intensity of ion emission under an electric voltage condition reveals the pressure at the tip of the coaxial structure, where ionization occurs. The spatial resolution of the measurements is defined by the volume into which the position of the tip fits, here estimated as a cube with an edge of 10 μm. The pressure at the tip is also obtained analytically as a function of the throughput through the coaxial structure. The theoretical and experimental pressure values reported in the present work are in agreement between them within the geometric uncertainties of the coaxial structure itself.

Research on Numerical Simulation Methods of Cavity Wind Noise Based on Different Turbulence Models

Abstract In order to more accurately simulate the acoustic properties of the fluid in the cavity, this paper uses four different turbulence models, LES, Spalart-Allmaras/LES, Realizable/LES, model, to simulate and calculate the simple cavity, combined with the acoustic experimental data carried out on the cavity model, and found that the simulated experimental values of pulsating pressure from the SST-k-/LES model and the Spalart-Allmaras/LES model have a better agreement with the simulated experimental values of the cavity pulsation pressure, and the calculated sound pressure spectra obtained from the SST-k-/LES model are the closest to the experimental values.

Mathematical modeling of the melt flow in the cone-ring channel of the extruder matrix

The peculiarity of the work is to develop a mathematical model of the melt flow in the cone-annular channel of the extruder die, which will allow you to choose the optimal geometric shape of the annular channel, as well as the angular rotation speed of the extruder screw. The object of the study is the cone-ring channel of the extruder matrix. To solve the three-dimensional problem of turbulent and laminar unsteady motion, the FlowVision software package was used, which allows solving partial differential equations using the finite volume method. The correct choice of the geometric shape of the annular gap made it possible to change the molecular structure of the product by creating a maximum pressure value. The optimally selected angular rotation speed of the extruder screw made it possible to carry out deep melting of the product due to the conversion of the mechanical energy of the screw into thermal energy. In the process of designing the forming of the cone-ring channel, the three volumes of the changing geometry of the stamp were selected, at the borders of the transition of which extreme points were observed. Deviations between the analyzed and experimental values of velocity and pressure were found in the limits of 9–12 % and 17–22 %, respectively. Based on the analysis of the obtained results of modeling, the optimal geometric shape of the annular gap and the recommended angular rotation speed of the extruder screw were revealed. The mathematical model proposed formed the basis of the developed design of the six-zone extruder. In the extruder, the geometric characteristics of the screw (variable pitch of the turns) were substantiated and selected, which provide the maximum effect of dissipation, i.e. autogenous mode of operation

A dual-parameter measuring method for wet steam based on the characteristics of differential pressure under phase-isolation state

To achieve accurate measurement of steam injection volume in the process of steam-driving heavy oil, a low-cost online metering device for wet steam flows is urgently needed. Primarily, the traditional Venturi device has a relative error due to the wet steam flow patterns. Therefore, a new physical model for wet steam measurement composed of a swirler and a Venturi was designed, based on the phase-isolation technology for multi-phase flow measurement. A theoretical explanation of the differential pressures was then proposed. Numerical simulations were conducted to investigate wet steam measurement, specifically under the condition of 10∼20 MPa. A new correlation for the steam quality and mass flow rate with the pressure drop was developed by the multiphase flow model via Eulerian. A novel wet steam dual-differential pressure measurement model was established by considering the effects of temperature and pressure, which predicts the wet steam overall mass flow rate and steam quality of the measurement device. Block P601 and Block P6 of the oilfield located in eastern China were selected as the development test area, and the differential pressure prediction was carried out for 68 different working conditions of two Wells based on the dual-parameter measurement model, which was then calibrated. The experimental fieldwork on Block P601 demonstrated that the feasibility of the dual-parameter measuring method was verified, with relative deviations of ±7% between the predicted and experimental values of differential pressure. After calibration of the measurement model, the predicted values were compared with the experimental values, yielding relative deviations of ±3.5% and ±5% for mass flow rate and steam mass measured online for wet steam, with Mean Absolute Percentage Errors (MAPE) of 1.73% and 2.21%. Thus, the dual-parameter measuring method has a certain engineering significance for the steam injection technology of heavy oil in oilfields.

Study on the Combustion Mechanism of Diesel/Hydrogen Dual Fuel and the Influence of Pilot Injection and Main Injection

Hydrogen is a clean and renewable alternative fuel. In this paper, the combustion mechanism of diesel/hydrogen dual fuel is constructed and verified. The mechanism is combined with three-dimensional numerical simulation to study the effects of pilot injection and main injection on the combustion and emissions of a diesel/hydrogen dual fuel engine. The mechanism uses a 70% mole fraction of n-decane and 30% mole fraction of α-methylnaphthalene as diesel substitutes, and it combines n-decane, α-methylnaphthalene, NOX, PAH, soot and H2/C1-C3 sub-mechanisms to form a diesel/hydrogen dual fuel combustion mechanism. The mechanism was verified by chemical kinetics, including the ignition delay time, JSR (Jet Stirred Reactor) oxidation and laminar flame speed, and then, it was verified by computational fluid dynamics. The results show that the simulated values are in good agreement with the experimental values of cylinder pressure, heat release rate and emissions data. The mechanism can well predict the combustion and emissions of a diesel/hydrogen dual fuel engine. Compared with single injection, the peak heat release rate, peak cylinder pressure and MPIR (Maximum Pressure Rise Rate) increase with the increase in pilot mass percent from 5% to 20%, which makes the phase of CA10 and CA50 advance and reduces CO emissions, but NOX emissions increase. With the advance of pilot injection timing from 10° CA BTDC to 30° CA BTDC, the peak cylinder pressure increases, the peak heat release rate decreases, CA10 and CA50 advance, CO emissions decrease, NOX emissions increase and NOX emissions peak at 30° CA BTDC. When the pilot injection timing is further advanced from 30° CA BTDC to 50° CA BTDC, the peak cylinder pressure decreases, the peak heat release rate increases, CA10 and CA50 are delayed, CO and NOX emissions are reduced, and NOX emissions at 50° CA BTDC are lower than those at 10° CA BTDC. With the advance of main injection timing from 0° CA BTDC to 8° CA BTDC, CO emissions decrease, NOX emissions increase, the peak cylinder pressure increases, the peak heat release rate decreases slightly first and then increases, and the peak cylinder pressure and peak heat release rate corresponding to the overall phase shift forward. When the main injection timing is advanced to 6° CA BTDC, MPIR is 1.3 MPa/° CA, exceeding the MPIR limit of diesel engine 1.2 MPa/° CA.

New analytical model and 3D finite element simulation for improved pressure prediction of elastic compression stockings

Elastic compression stockings (ECSs) are essential for the prevention and treatment of venous disorders of the lower limbs. Finite element modeling (FEM) is an effective method for numerically analyzing ECS pressure performance for guiding ECS material design and pressure dose selection in treatment. However, existing FEM studies have primarily used the two-dimensional (2D) mechanical properties (i.e., properties along the wale and course directions) of ECS fabrics and ignored their three-dimensional (3D) mechanical properties (i.e., those along the thickness direction), causing deviations in pressure predictions. To address this limitation, the present study developed a new approach for determining the 3D mechanical properties of ECS fabrics through orthotropic theoretical analysis, analytical model development, FEM, and experimental testing and validation. The results revealed that the deviation ratios between the experimental and simulated pressure values of ECS fabrics was 19.3% obtained using the 2D material mechanical properties that was reduced to 10.3% obtained using the 3D material mechanical properties. Equivalently, the FEM simulation precision increased by 46.6%. These results indicate that the proposed approach can improve finite element analysis efficiency for ECS pressure prediction, thus facilitating the functional design of elastic compression materials for improving compression therapeutic efficacy.

Testing and analysis of PVC liners under simulated grouting pressure

Sliplining is often selected for rehabilitation of deteriorated culverts and drainage structures, and involves placing a liner pipe within the deteriorated host pipe and filling the gap between the two with grout. However, currently the design of these liners to resist buckling during the critical grouting phase has not been evaluated experimentally. In addition to obtaining test data to evaluate existing buckling models, the tests permit assessment of the influence of buoyancy on liner stability and the influence of the size of the gap between the liner and host pipe. Therefore, this paper presents an experimental study undertaken after adapting an existing test cell. Two tests were conducted, one on a liner within the host pipe with their axes oriented vertically (so not affected by buoyancy) and another where pipe and liner axes were oriented horizontally and so subject to buoyancy. The liners were instrumented with distributed strain and displacement sensors, and subjected to simulated external grouting pressure using water pressure applied to a rubber bladder. Both liners first buckled under hydrostatic pressure and had greatly reduced incremental flexural stiffness until liner deformations brought it into contact with the test cell, at which point the liners took additional pressures until finally failing due to nonlinear buckling. Analytical and numerical estimates of the thrust forces in the liner and the hydrostatic buckling pressure were within 10% of the experimental values of maximum pressure on the liner (at the invert). However, it is not conservative to estimate the critical buckling pressure (the maximum or peak pressure before the pipe fails) using the existing buckling model. For the current tests, the hydrostatic and critical buckling pressures are almost independent of the distance between the axes of the liner and host pipe (i.e. where the contractor positions the liner within the post pipe)

Predicting Compression Pressure of Knitted Fabric Using a Modified Laplace's Law.

The aim of this study is to develop a mathematical model for the prediction of compression pressure based on fabric parameters, such as engineering stress, engineering strain and engineering modulus of elasticity. Four knitted compression fabrics with different fibrous compositions and knit structures were used. Rectangular-cut strips were employed for the force–elongation characterization of the fabrics. The experimental pressure values between the fabric and rigid cylinder were assessed using a Picopress pressure measuring device. The mechanical and physical parameters of the fabric that influence the interface pressure, such as strain, elasticity modulus/stress and thickness, were determined and integrated into Laplace’s law. A good correlation was observed between the experimental and calculated pressure values for all combinations of fabrics, mounted with variable tension on the cylinder. Over the considered range of pressures, the difference between the two datasets was generally less than 0.5 mmHg. The effect of washing after five, ten and fifteen washing cycles on the fabric–cylinder interface pressure was found to be significant.

Pressure-induced 1T to 3R structural phase transition in metallic VSe2 : X-ray diffraction and first-principles theory

We study pressure-induced structural evolution of vanadium diselenide (VSe2), a 1T polymorphic member of the transition metal di-chalcogenide (TMD) family using synchrotron-based powder X-ray diffraction (PXRD) and first-principles density functional theory (DFT). Our XRD results reveal anomalies at P ~4 GPa in c/a ratio, V-Se bond length and Se-V-Se bond angle signalling an isostructural transition. This is followed by a first order structural transition from 1T (space group P-3m1) phase to a 3R (space group R-3m) phase at P ~11 GPa due to sliding of adjacent Se-V-Se layers. We present various scenarios to understand the experimental results within DFT and find that the 1T to 3R transition can be captured only after inclusion of enthalpic correction associated with errors in cell volume with underestimated transition pressure. The abrupt increase in the Debye-Waller factors of Se atoms by a factor of ~4 and hence the anharmonic effects across the structural transition pressure are hitherto not reported so far and hint a possible way to understand the mismatch between the experimental and theoretical transition pressure values.

Investigating the Condensation of Benzene (C6H6) in Titan’s South Polar Cloud System with a Combination of Laboratory, Observational, and Modeling Tools

Abstract We have combined laboratory, modeling, and observational efforts to investigate the chemical and microphysical processes leading to the formation of the cloud system that formed at an unusually high altitude (>250 km) over Titan’s south pole after the northern spring equinox. We present here a study focused on the formation of C6H6 ice clouds at 87°S. As the first step of our synergistic approach, we have measured, for the first time, the equilibrium vapor pressure of pure crystalline C6H6 at low temperatures (134–158 K) representative of Titan’s atmosphere. Our laboratory data indicate that the experimental vapor pressure values are larger than those predicted by extrapolations found in the literature calculated from higher-temperature laboratory measurements. We have used our experimental results along with temperature profiles and C6H6 mixing ratios derived from observational data acquired by the Cassini Composite Infrared Spectrometer (CIRS) as input parameters in the coupled microphysics radiative transfer Community Aerosol and Radiation Model for Atmospheres (CARMA). CARMA simulations constrained by these input parameters were conducted to derive C6H6 ice particle size distribution, gas volume mixing ratios, gas relative humidity, and cloud altitudes. The impact of the vapor pressure on the CIRS data analysis and in the CARMA simulations was investigated and resulted in both cases in benzene condensation occurring at lower altitude in the stratosphere than previously thought. In addition, the stratospheric C6H6 gas abundances predicted with the new saturation relationship are ∼1000× higher than previous calculations between 150–200 km, which results in larger particle sizes.

Calculating pressure with elastic geobarometry: A comparison of different elastic solutions with application to a calc-silicate gneiss from the Rhodope Metamorphic Province

Raman elastic geobarometry has increasingly been used complementary to metamorphic phase equilibria to estimate the conditions of recrystallization in metamorphic rocks. The procedure of applying Raman elastic barometry to host-inclusion mineral systems requires several steps that involve various assumptions. One of the most essential assumptions is that the mineral host-inclusion system behaves in an elastic and reversible manner. We discuss the discrepant results obtained by different authors employing different analytical solutions for elasticity and explore the assumptions lying behind each method. Furthermore, we evaluate numerically linear and non-linear elastic solutions and show their discrepancies. Both formulations are tested against recently published experiments on quartz inclusions in garnet (QuiG) at pressures up to 3 GPa, and we find a very good agreement between calculated and experimental pressure values (within 10% relative error). We subsequently apply our new elastic geobarometer to a calc-silicate gneiss from the Rhodope Metamorphic Province (N. Greece). The results of Raman elastic barometry combined with garnet-clinopyroxene geothermometry yield eclogite-facies conditions (~720 ± 40 °C, ~1.5 ± 0.2 GPa). These results are comparable to a high-temperature metamorphic overprint deduced from phase equilibria modeling in surrounding lithologies (730 ± 40 °C, ~1.2 ± 0.1 GPa). Our findings indicate that the estimated pressure from Raman elastic barometry is consistent with a significant viscous relaxation at high temperatures. We conclude that although Raman elastic barometry is a powerful tool for pressure estimation in metamorphic rocks, its pressure estimates do not necessarily correspond to entrapment conditions. Our results are consequential for the estimates of reaction overstepping in high-grade metamorphic rocks.

Optimization of plasma treatment parameters to improve the wood-coating adhesion strength using Taguchi integrated desirability function approach

The aim of this study is to enhance the coating adhesion strength by optimizing the air plasma application parameters. Air-plasma treatment parameters were selected as working distance, treatment speed and pressure, while material type parameters were determined as low mean density fiberboard (MDF-1) and high-density mean fiberboard (MDF-2). Due to the low adhesion strength in water-based paint applications compared to other types of paint, water-based paint was applied to these samples. Taguchi orthogonal design and analysis of variance (ANOVA) were applied to investigate the significant parameters on the adhesion strength. Desirability function was used to determine the optimum factor levels. According to experimental design results, working distance, treatment speed, and pressure values of 8.82 mm, 60 mm/s, and 1.10 bar were determined as optimum plasma treatment parameters for MDF-1, respectively. Corresponding values for MDF-2 were 9.19 mm, 60 mm/s, and 1.06 bar. The improvement in adhesion strength was evaluated as 22% increase for MDF-1 and 16% increase for MDF-2.

Numerical simulation of diesel engine using waste plastic oil blends

This article is focused on numerical analysis of the combustion and emission parameters on the single-cylinder direct-injection (DI) engine operated in both diesel and distilled waste plastic oil blends. Analyzes of the first stage distilled waste plastic oil blends (D1WPO30) was carried out with 70:30 proportions. Simulated results are compared with experimental values in terms of cylinder pressure, heat release rate, oxides of nitrogen (NOx) and soot particles. The deviation between experimental and simulation values of cylinder pressure is found to be 1.8% with diesel whereas 6.5% with D1WPO30. The apparent heat release rate with D1WPO30 was found to be higher about 13% than diesel in simulation. The simulated NOx with D1WPO30 was found 7% higher than with diesel fuel simulation but found 16% lesser than D1WPO30 experimentation. Similarly, the soot was found higher about 16% with D1WPO30 than diesel simulation and 17% lesser than experimental values. The CFD analysis connected with experimental studies is proven that an effective approach to predict the parameters of the in-cylinder process.

Comparison of Experimental and Numerical Study on Superplastic Forming of Rectangular Box Shape using AZ31 Magnesium Alloy Sheet

Super plastic forming has become a feasible process in manufacturing aircraft and automobile parts. Super-plasticity is a property of certain metallic materials which enable them to attain very high elongations (100% and above) without necking under certain conditions. This is assigned to the viscous behaviour exhibited by certain metals and alloys with very fine and stable grain structure at temperatures above half of the melting point. The experimental setup was developed for finding the parametric influences and their effects on super plastic forming. AZ31 Magnesium alloy is most suitable materials for producing more complex shapes using super plastic forming method. The experimental values of pressure, temperature and the thinning, dome height of the super plastically formed specimens were analysed.

Plastic intensity reduction using thermally insulating coatings for injection molds

The use of plastics in today's world is still increasing despite its enormous burden for environmental sustainability. The urge to reduce plastics impact is driving the development of novel technological solutions. The high viscosity of thermoplastic polymer melts often leads to the design of oversized plastic parts having wall thickness higher than structural requirements. This work proposes a novel approach to wall thickness reduction, exploiting the thermally insulating effect of mold coatings. Four different mold coatings were characterized using inline rheological testing carried out on a PET using a slit-die open mold. The thermal boundary condition of a numerical model was calibrated by fitting the numerical to experimental pressure values. The thickness reduction associated with the use of a specific coating was then quantified for a case study geometry using the calibrated model. The results indicated that it is possible to reduce the thickness of the part by 12%, leading to material consumption and cycle time reduction of 8% and 22%, respectively.

GdFe2 Laves phase intermetallic system under pressure: an ab-initio study

Here we perform abinitio study of Curie temperature TC under hydrostatic pressure for intermetallic compound GdFe2. To calculate TC for GdFe2 we applied mean-field solution of the Heisenberg model for several magnetic sublattices with DFT/LDA calculated values of necessary exchange interaction integrals and local magnetic moments. To compare with available experimental data pressure values were taken from zero up to about 70 Kbar. It corresponds to 2% compression of the volume of the unit cell. In agreement with experimental data TC grows under pressure. It was shown that Fe ions magnetic sublattice alone provides only about 75% of the experimental Curie temperature TCexp. Gd sublattice is found to give very weak contribution to the TCexp. Here we show that the missing 25 % of TCexp comes from Fe-Gd exchange pairs.

Equations for calculation of liquid-vapor equilibrium in binary mixtures containing methane

Equations describing the experimental data on liquid-vapor equilibrium in binary mixtures of methane with argon, carbon dioxide and helium have been compiled. The equations describe the dependence of pressure of liquid or vapor on temperature and composition. When compiling them, the program selected most significant coefficients of the equations. The standard deviations of experimental values of pressure from the calculated values range from 1.8 to 5.0%. The equations make it possible to determine the composition or temperature of the phases at known values of other parameters of phase equilibrium.

Performance analysis of high-temperature water source cascade heat pump using BY3B/BY6 as refrigerants

In this study, a high-temperature water source cascade heat pump (HTWSCHP) system was developed, which could provide heat at a temperature of approximately 170 °C. In order to select the optimum refrigerant, six pairs of refrigerants were compared theoretically when the heating temperature varied from 100 °C to 170 °C and the evaporation temperature was 55 °C. An experimental setup was used to compare the performance of BY3A/R245fa, BY3B/R245fa and BY3B/BY6 in the HTWSCHP with heating temperature in the range 100–140 °C. The theoretical results led to the selection of BY3B/BY6 as the best refrigerants for HTWSCHP, and the experimental results also showed better performance of BY3B/BY6. Moreover, this system using BY3B/BY6 produced hot water with the highest temperature of 168.4 °C. The coefficient of performance (COP) of the system was the best when the temperature lift was 70 °C compared to other heat pump systems, and the maximum temperature lift reached 113.4 °C. The experimental values of heating capacity, input power, COP, and discharge pressure were in good agreement with the theoretically calculated values. In addition, the results showed that the application scope of the HTWSCHP using BY3B/BY6 as refrigerant should be lower than 155 °C, for the safety of equipment and the economic challenges of practical application.

Multizone Model Study for DI Diesel Engine Running on Diesel-Ethanol-Biodiesel Blends of High Ethanol Fraction

A multizone combustion model for closed cycle of a DI diesel engine is developed to interpret the experimental investigations on the utilization of diesel-ethanol-biodiesel blends of high ethanol fraction (DEB blends). A computer-based programming for engine process simulation is developed in MATLAB. The model is validated with the experimental values of cylinder pressure and heat release rate. Important information related to fuel injection and combustion inside the combustion chamber, is revealed through the model prediction which is normally difficult to get from the experiments. Model prediction shows that the rate of fuel evaporation is higher for DEB blends, than diesel fuel at any instant of time. The fuel combustion is started late for DEB blends compared to diesel fuel, however, once the combustion is started the burning rate is higher than the diesel fuel. The droplet size (Sauter mean diameter) is decreased for DEB blends which indicate improved fuel atomization. The mean temperature in the zone is significantly lower for DEB blends compared to diesel fuel. The equivalence ratio in the zone is decreased for DEB blends proving that engine runs leaner. The equivalence ratio trend is not uniform as it depends on the combination of the rate of fuel evaporation, rate of air entrainment and rate of burning. Soot density is remarkably decreased, and NOx formation is also drastically reduced for DEB blends at different instant of time. The predictions help to interpret the experimental results for DEB blends and its comparison with diesel fuel.

Refined Alkali Metal Ion Parameters for the OPC Water Model

Using all‐atom molecular dynamics simulations with Joung–Cheatham ion parameters and the OPC water model, the osmotic pressure values of monovalent alkali metal chloride solutions (KCl and NaCl) were calculated and compared to experimental values. The simulated osmotic pressure data were overestimated at high concentrations. To close the gap between simulation and experiment, we attempted to modify the Lennard–Jones interaction parameters of the cation–water oxygen pairs explicitly using the unequal Lorentz–Berthelot combination rule, such that experimental osmotic pressure values for a range of concentrations were well reproduced. These novel ion parameters could be potentially beneficial to simulation studies of G‐quadruplex DNA molecules, where ions play a key role in their folding process.