Total Pressure Data Research Articles

Least-Squares evaluation of DMT dissipation test data – some preliminary results

The Flex method does not work if the DMTA total stress dissipation curve is non-monotonic or has no inflexion point. To overcome the problems, various versions of a mathematically precise DMTA total stress dissipation test evaluation method are suggested to be considered. These versions can be classified (i) on the basis of the measured data, as only total stress-based and both total stress and pore water pressure-based methods, (ii) on the basis of the dimension of the model, as oedometer, cylindrical and spherical coupled consolidation models, (iii) as linear models or models with relaxation. In this paper some DMTA dissipation tests made at test sites in Szeged and Ballina test sites are evaluated and the c values identified with various methods are started to be compared. According to the first results, an evaluation method, based on the oedometer relaxation test model and both total stress and pore water pressure data, provided c values about 3 times larger than the Flex method (and could be used to evaluate non-monotonic data). The use of pore water data – generated or measured as C readings – decreased the parameter error.

Physics of thermionic, orificed hollow cathodes: I. Theory and experimental validation

A model aimed at illuminating the physics of thermionic, orificed hollow cathodes is developed and validated with experimental data. The model is intended to describe the variation of total (neutrals, ions, and electrons) static pressure with controllable parameters. That pressure must be properly evaluated because it influences important plasma parameters in the cathode such as the attachment length and the electron temperature, which directly impact the lifetime of thermionic inserts. The model, which combines a zero-dimensional approach to the conservation of energy and momentum for the combined plasma-neutral fluid and a charge-exchange-limited ambipolar diffusion model, allows for the computation of all plasma quantities, including the total fluid pressure. The model depends on the operating conditions (discharge current and mass flow rate), cathode geometry, and the gas species, along with two non-controllable parameters: the neutral gas temperature and the sheath potential. Total pressure data at up to 307 A of cathode discharge current were obtained experimentally and were used, along with data from the literature, to validate the model. Good agreement is obtained for all quantities. The model is used in a companion paper to clarify the role of magnetic and gasdynamic pressure in the scaling of total pressure, to derive scaling laws applicable to thermionic, orificed hollow cathodes, and to propose novel cathode design rules.

Total pressure in thermionic orificed hollow cathodes: Controlling mechanisms and their relative importance

A statistical analysis is conducted to identify which physically relevant non-dimensional parameters influence the total (neutral, ion, and electron) static pressure inside thermionic orificed hollow cathodes. It is critical to uncover and order the importance of the physical mechanisms that affect the pressure inside hollow cathodes because it influences the plasma attachment length, the electron temperature, and the sheath potential. These plasma parameters, in turn, affect the emitter lifetime. A principal component analysis of total pressure data obtained from the literature reveals that four non-dimensional variables can account for most of the variation in the total-to-magnetic pressure ratio over five orders of magnitude. The relevant variables are identified with a backward stepwise selection process and an exhaustive grid search and include, by order of importance: the gasdynamic-to-magnetic pressure ratio, the ratio of the mass flow rate to the discharge current, the orifice-to-insert diameter ratio, and the orifice Reynolds number. It is also shown, using various models and regression analyses, that empirical, Poiseuille, or isentropic flow models should not be used for predictive cathode design work. The data-driven study suggests that, while viscous effects may be important, the variation in those effects between cathodes is negligible compared to the effects of the modification of the gas constant due to the plasma, the transitional flow, the flux of heavy species on the orifice plate, and the Lorentz force.

Measurement of Unsteady Aerodynamic Data in Turbomachi-nery Periodic Flows

The objective of this work is to demonstrate the feasibility and advantage of an alternative approach to aerodynamic data acquisition in high-speed highly-loaded turbine engine rotating components. Two methodologies of data acquisition using fast sensing pressure probes are described here. The conventional approach is based on using separate probes for detection of unsteady total and static pressures and the flow direction. This method is labor intensive, requiring either multiple access ports on the investigated engine or repetitive test runs for each individual probe if only one access port is available. An alternative method, using only one Pitot-cylinder probe, can be used to acquire total pressure and flow direction data. The Pitot-cylinder probe basically functions like a controlled flow direction follower. The data reduction procedure for this probe relies on strict periodicity of the investigated flow during a test run. A detailed explanation of data reduction procedure and examples of achieved results are presented.

New solubility and heat of absorption data for CO2 in blends of 2-amino-2-methyl-1-propanol (AMP) and Piperazine (PZ) and a new eNRTL model representation

New data comprising CO2 partial pressure, total pressure, and the heat of absorption of CO2 for over aqueous solution of 3 mol/dm3 AMP and 1.5 mol/dm3 PZ and total pressure and heat of absorption for different mol ratios of AMP/PZ (3.0/0.0, 0.0/1.5, 0.5/4.0, 1.5/3.0, 2.25/2.25, 3.0/1.5, 4.0/0.5) are presented as functions of CO2 loading and temperature.Measured solubility data and selected data reported in the literature were used in the regression of binary interaction energy parameters in the quaternary system (AMP/PZ/H2O/CO2) using the eNRTL model. The equilibrium constants and binary interaction energy parameters from our previous work on the ternary systems of AMP/H2O/CO2 and PZ/H2O/CO2 were used without refitting.Good agreement with the literature was observed for the total pressure data over aqueous solutions of 3.0 mol/dm3 AMP and 1.5 mol/dm3 PZ, and the CO2 partial pressure and heat of reaction data over aqueous solutions of 3.0 mol/dm3 AMP+1.5 mol/dm3 PZ at different loadings and temperatures. The results reflect that the new data are consistent with reported data from the literature.The modeling results show that the eNRTL model represents the data well with AARD values of 13.1% for total pressure and 20.9% for CO2 partial pressure. The volatility of AMP and PZ as function of loading and temperature and published speciation data for AMP/AMPH+, PZ/PZH+/PZH22+, PZCO2−/PZH+CO2−, PZ(CO2−)2 and HCO3−/CO32− were also well predicted.Only the heat of absorption data over an aqueous solution of 3.0M AMP+1.5M PZ from this work can be compared with literature data, and good agreement is observed. The eNRTL model also predicts satisfactorily the experimentally obtained heat of absorption data for all different ratios of AMP/PZ. Individual reaction contributions show that when the AMP/PZ ratio increases, the predicted total heat of absorption goes toward the single solvent AMP system where only protonated AMP is the main contributor. When the AMP/PZ ratio decreases, the predicted total heat of absorption also approaches the single solvent PZ system where the protonated PZ, PZ-monocarbamate and zwitterion reactions play important roles. In systems with high PZ-concentration, the contribution of the zwitterion, protonated PZ and PZ-carbamate cancel each other at high loadings.

A New Method for Pore Pressure Prediction on Malfunctioning Cells Using Artificial Neural Networks

Embankment rockfill dams are the most common dam construction types used in the world today. One third of all embankment dam failures are caused by dam slope instability. The dam is stable when the slopes are stable. Slope safety of the dam is assessed through pore and total pressure data analysis registered on pressure measurement cells installed in the dam. During the service life of a dam, one or more cells may malfunction after years of operation. Cell replacement implies economically unjustified high costs and is usually technically impossible and high risk. In this paper, the problem of a malfunctioning cell with a small available dataset is analysed. A new method for pore pressure prediction on malfunctioning cells has been developed using several successive artificial neural networks (ANNs) to obtain high accuracy of the predicted values. The results show that these predicted values are more precise than values we could have obtained using only one artificial neural network for prediction.

Total vapor pressure of hydrophobic deep eutectic solvents: Experiments and modelling

Headspace gas chromatography mass spectrometry (HS-GC–MS) was used to determine the volatility of six selected hydrophobic deep eutectic solvents (DESs). The partial pressure of each DES constituent (decanoic acid, thymol, 1-tetradecanol, menthol or lidocaine) was measured from 313.15 to 373.15 K. The activity coefficients of the hydrogen bond acceptor (HBA) and the hydrogen bond donor (HBD) were determined to quantify the interactions between the DES constituents, thereby deepening the understanding of the thermodynamic nature of the DESs. In addition, the activity coefficients for both components in each DES were predicted with the UNIFAC group contribution method. Similar trends and reasonably close values were obtained for the measured and predicted activity coefficients. It has been found that the interactions between the DES constituents tend to become weaker with increasing temperature. Strong interactions occur between thymol and lidocaine, and thymol interacts moderately with menthol. A weak force exists between decanoic acid and menthol. The mixtures of menthol with 1-tetradecanol or lidocaine are not strictly DESs since for each DES constituent both the measured and predicted activity value is close to unity. A viscosity study was also carried out to quantify the interactions and similar results were found. The ideal mixing rule was proven to correctly describe the viscosity for the mixture of menthol with 1-tetradecanol or lidocaine. While compared to the ideal mixture viscosity, an increase in viscosity was observed for other studied DESs indicating stronger interactions. Finally, the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) was shown to accurately describe the thermodynamic properties, where the PC-SAFT pure-component parameters for the DESs were obtained by fitting to pure DES density and total vapor pressure data.

Solubility of CO2 in 0.1M, 1M and 3M of 2-amino-2-methyl-1-propanol (AMP) from 313 to 393K and model representation using the eNRTL framework

This paper presents an experimental and modeling study of the systems pure AMP, AMP/H2O and AMP/CO2/H2O. All available data in the literature is collected and new experimental data for the ternary AMP/CO2/H2O system are presented. Modeling was performed using an Antoine model for the pure component VLE and an NRTL model for the binary AMP/H2O system. The parameters in the two model were fitted together in a combined fit yielding a pure component representation with an AARD of 1.4% for saturation pressure and of 2.6% for vapor-phase mole fraction of all binary data. The individual fits to the various data sets used are also given.For the ternary AMP/CO2/H2O system an e-NRTL model was fitted to the combined sets of new and literature VLE data. The model representation of all ternary data was with an AARD of 23.5% for the CO2 partial pressure data, 21.5% for the total pressure data and 4.7% for the apparent Henry's law constant data. The model covers a range of AMP concentrations from 0.9 to 56 mass %, temperatures from 298 to 393K and CO2 loadings from 0 to about 2.The model is also shown to give good representation of speciation and a reasonable representation of heat of absorption data found in the literature.

Eating away at protected areas: Total grazing pressure is undermining public land conservation

Protected areas are critical for the long-term conservation of biodiversity globally. Across agricultural landscapes, protected areas serve as refuges for threatened and declining species and provide valuable ecosystem services that support broader landscape function. However, increasing pressure on protected areas from a range of sources is undermining their unique conservation values. Much of the native vegetation remaining in southern Australia is now protected from broad-scale clearing, but the management of threats within these areas could be inadequate to maintain their biodiversity. In particular, grazing by domestic and wild mammalian herbivores can have a significant impact on the condition of remnant native vegetation, even if it is formally protected. We evaluated the evidence for grazing-pressure trends in native vegetation in both protected and unprotected areas across an agricultural landscape covering c. 180 000 km2 of South Australia. Using total grazing pressure data from 1298 sites surveyed between 2004 and 2016, we employed Bayesian linear mixed-effects modelling to demonstrate increasing trends in grazing severity in four of five study regions, estimating that 45%–54% of grazed plants were heavily or severely grazed by 2016. Over the 12-year period, grazing severity in protected areas increased to levels closely matching those on private, unprotected land. Our results suggest that abundant native and/or introduced grazing animals are having an increasing impact on native vegetation across large areas of the agricultural zone of South Australia, with a disproportionate impact on protected areas. We recommend that: (1) research is needed to identify sustainable total-grazing-pressure thresholds; and (2) options should be considered for an adaptive, coordinated, and cross-tenure approach to maintaining total grazing pressure in protected areas below these thresholds.

터보차저 압축기 내 유동특성에 관한 연구

This research is to numerically investigate the flow characteristics of the turbocharger compressor. Research concentrates on the flow factors on possible flow noise with local positions with five different rotating speeds. The fluid model of turbocharger compressor which is designed by CATIA V5R21 is analyzed by ANSYS FLUENT V18.0 with SST turbulence model. Flow characteristics are accomplished for four flow factors. The flow velocity increased with rotating speeds of compressor wheel. And total pressure data at outlet was compared with experimental data at same design conditions. The error of two data are 9.94% at 120,000 RPM, 4.09% at 150,000 RPM, 2.05% at 180,000 RPM, 1.90% at 200,000 RPM and 0.95% at 220,000 RPM. Maximum value of vorticity existed locally at almost same positions of wheel with five different rotational speeds, and is also located at tip of blade. Higher value of pressure coefficient also existed at high rotating speeds. And maximum value of pressure coefficient is located at end of wheel. Therefore, the flow noise can possibly generate at tip of blade and end of wheel.

Determination of the Total Vapor Pressure of Hydrophobic Deep Eutectic Solvents: Experiments and Perturbed-Chain Statistical Associating Fluid Theory Modeling

Head-space gas chromatography mass spectrometry (HS-GC-MS) was used for the first time to measure the total vapor pressure of hydrophobic deep eutectic solvents (DESs). The new method was developed as a valid alternative for thermogravimetric analysis (TGA), as TGA did not allow obtaining reliable total vapor pressure data for the hydrophobic DESs studied in this work. The main advantage of HS-GC-MS is that the partial pressure of each DES constituent and the contribution of each DES constituent to the total vapor pressure of the mixture can be measured. The results give a clear indication of the interactions occurring between the DES constituents. Also, activity coefficients, enthalpies of evaporation, and activation energies for fluid displacement were obtained and correlated to the measured vapor pressure data. It was confirmed that the total vapor pressures of the hydrophobic DESs are very low in comparison to vapor pressures of commonly used volatile organic solvents like toluene. The total vapor pre...

EXPERIMENTAL INVESTIGATION OF SHOCK WAVE OSCILLATION ON A THIN AIRFOIL

Experimental results of surface pressure distribution over a thin supercritical airfoil and its wake are presented. All tests were conducted at free stream Mach numbers from 0.27 to 0.85 and at different angles of attacks in a transonic wind tunnel. The model was equipped with static pressure orifices connected to high frequency pressure-transducers. The present paper evaluates variations of shock wave location with both Mach number and angle of attack variation as well as its interaction with the boundary layer leading to the buffet phenomenon. The frequency of the shock wave oscillation and unsteady wake behaviour at a freestream Mach no. of M=0.6 and at different angles of attacks are measured using cross-correlation technique by means of pressure sensors locating on the suction side of the model and via the rake total pressure data that was traversed vertically behind the model respectively. From the analysis of surface pressure distribution and wake data, drag divergence occurred at a certain angle of attack and at a frequency equal to the shock wave oscillation frequency.

An experimental study on the effect of square grooves on decay characteristics of a supersonic jet from a circular nozzle

In this experimental work, the effect of square grooves on the structure of a supersonic jet emanating from a circular nozzle has been investigated at three different nozzle inlet total pressures i.e 360 kPa, 550 kPa and 720 kPa. The nominal exit Mach number is 1.8. A new empirical relation for predicting the supersonic core length for grooved nozzle has been suggested. Further, a new parameter “groove effectiveness” has also been suggested to quantify the effect of the groove by using the total pressure data in the supersonic core length. Experimental results suggest that at higher nozzle inlet total pressure, the groove effectiveness plays a minor role. From the jet centreline total pressure data, supersonic core length, the locations at which 50 % and 90 % decay occurs have been obtained. It has been observed that higher groove effectiveness is associated with smaller values of supersonic core length, L50% and L90%. Schlieren images of the jet structure shows unsymmetrical shock pattern of jets emanating from a single grooved nozzle.

Energy decay characteristics of a non-circular supersonic jet

ABSTRACTIn this paper, we study the energy decay characteristics of the nozzle at supersonic velocity. We have taken three types of configuration: circular, square and elliptical. The results are compared to the circular exit design. The experimental data are compared in relation to the pressure ratio. The throat area assumed to be constant. The supersonic potential core length of the different orientations is calculated. From the results, we have found that the exit geometry plays an important role in mixing promotion. The core length of a non-circular jet is less intense than a circular jet. The core length of the nozzle is the same in both under and overexpanded case. In addition to that, there is no sign of axis switching due to weak shock. The results are obtained in two different categories, total pressure data and numerical simulation. An empirical relation is used to investigate the core length experimentally.

Study of decay characteristics of rectangular and elliptical supersonic jets

Experiments were carried out to study the decay characteristics of non-circular supersonic jets issued from rectangular and elliptical nozzles, and results were compared with circular case. Numerical simulations and Schlieren image study were carried out to validate the experimental results obtained from total pressure data. The supersonic core lengths of the jets were found to be different for different exit shaped geometries and area ratio for those nozzles was same. To avoid the losses in divergent section, the shape of cross-section of throat was maintained same that of as the exit. The exit shape geometry played the important role to enhance the mixing of the jet with ambient air, without requiring secondary method to increase the mixing characteristics. The mixing with ambient air in case of non-circular jets was more intense when compared to that of circular jets, which resulted in reduction of supersonic core length. The behavior of supersonic core length had identical signature for both under-expanded and over-expanded operation. The supersonic core length was characterized by exit shape factor. In literature, the supersonic jet characterization and the related experimental correlation are available for optimum expansion conditions whereas for other expansion (under and over) conditions the experimental correlations are barely available. While investigating experimentally, a new empirical relation was obtained which was the improved form of earlier correlations for supersonic core length. The current results obtained from three different methods (total pressure data, schlieren image and numerical simulation) had shown the reasonable agreement with the experimentally obtained relation.

On the gassing behavior of lithium-ion batteries with NCM523 cathodes

Gas evolution has a profound effect on the functioning of state-of-the-art lithium-ion batteries. On one hand, it is the natural concomitant of solid electrolyte interphase (SEI) formation on the anode (reduction of electrolyte components). On the other hand, because of the demand for high terminal voltages, it is also the consequence of electrolyte and/or cathode material oxidation. Overall, gassing happens on the expense of Coulombic efficiency and additionally raises safety issues. Herein, the gassing behavior of one of the most important commercialized cathode materials, namely Ni-rich Li1 + xNi0.5Co0.2Mn0.3O2 (NCM523 with 0.01 < x < 0.05), is reported for the first time. We analyze the generation pattern of the most typical gases H2, C2H4, CO2, and CO during 30 cycles by means of differential electrochemical mass spectrometry combined with Fourier transform infrared spectroscopy. In a long-term test of an NCM523/graphite cell, we monitor its potential-resolved gas evolution and evaluate the total amount of gas from cycle to cycle. An explanation on the characteristic features of pressure versus time curves during cycling is given by combining the spectrometric and total gas pressure data. With additional information from graphite/lithium cells, the identity of gases formed during SEI formation is revealed.

VLE Modeling of Aqueous Solutions of Unloaded and Loaded Hydroxides of Lithium, Sodium and Potassium

This work focuses on equilibrium modeling of CO2 solubility in aqueous solutions of unloaded (as hydroxides) and loaded (as carbonates) hydroxides containing Li+, Na+ and K+ counter ions. Due to the ionic nature of the LiOH/NaOH/KOH-CO2-H2O solutions, the electrolyte-Non-Random-Two-Liquid (e-NRTL) model, described by Chen and Evans [1], is applied to correct the non-idealities in the liquid phase. The special feature of the equilibrium model employed in this work is the simultaneously regression of Vapor-Liquid Equilibrium (PCO2, Ptotal) and apparent Henry's law constant data selected from literature and Ptotal data for LiOH measured in this work. This approach will give better prediction for the molecular CO2 activity coefficients and the liquid phase activities calculated by use of the resulting e-NRTL model will be consistent with the apparent Henry's law constant. The equilibrium model developed in this work is based on and represented 112 data points for Li+ with 2.7% total AARD, 432 selected data points for Na+ with total 7.2% AARD and 354 selected data points for K+ with total 9.9% AARD. The total pressure data over aqueous LiOH solutions were measured for a range of concentrations (0.25 – 8.5wt. %) and temperatures (40 – 90°C) using an ebulliometer.

Ebulliometric measurement of total pressure in the binary polystyrene + butan-2-one system

Vapour–liquid equilibria – as total pressure data – were determined isothermally in the polystyrene + butan-2-one system at 323.15, 333.15, and 343.15 K using the microebulliometric method. The experimental data were correlated using the UNIQUAC-free volume model, and the applicability of two known predictive models was tested.

Total pressure fluctuations and two-phase flow turbulence in hydraulic jumps

The large-scale turbulence and high air content in a hydraulic jump restrict the application of many traditional flow measurement techniques. This paper presents a physical modelling of hydraulic jump, where the total pressure and air–water flow properties were measured simultaneously with intrusive probes, namely a miniature pressure transducer and a dual-tip phase-detection probe, in the jump roller. The total pressure data were compared to theoretical values calculated based upon void fraction, water depth and flow velocity measured by the phase-detection probe. The successful comparison showed valid pressure measurement results in the turbulent shear region with constant flow direction. The roller region was characterised by hydrostatic pressure distributions, taking into account the void fraction distributions. The total pressure fluctuations were related to both velocity fluctuations in the air–water flow and free-surface dynamics above the roller, though the time scales of these motions differed substantially.

Equilibrium Total Pressure and CO2 Solubility in Binary and Ternary Aqueous Solutions of 2-(Diethylamino)ethanol (DEEA) and 3-(Methylamino)propylamine (MAPA)

Equilibrium total pressures were measured and equilibrium CO2 partial pressures were calculated from the measured total pressure data in binary and ternary aqueous solutions of 2-(diethylamino)ethanol (DEEA) and 3-(methylamino)propylamine (MAPA). The measurements were carried out in a commercially available calorimeter used as an equilibrium cell. The examined systems were the binary aqueous solutions of 5 M DEEA, 2 M MAPA, and 1 M MAPA and the ternary aqueous mixtures of 5 M DEEA + 2 M MAPA (5D2M) and 5 M DEEA + 1 M MAPA (5D1M), which gave liquid–liquid phase split upon CO2 absorption. The total pressures were measured and the CO2 partial pressures were calculated as a function of CO2 loading at three different temperatures 40 °C, 80 °C, and 120 °C. All experiments were reproduced with good repeatability. The measurements were carried out for 30 mass % MEA solutions to validate the experimental method. All the measured data were also compared with the results of 30 mass % MEA as a reference case. 5 M DEEA has shown high cyclic capacity. Both 2 M and 1 M MAPA showed high loading capacities at 40 °C and 120 °C. The aqueous amine mixtures, 5D2M and 5D1M, gave fairly good cyclic capacities and their results depend on the concentration of the promoter (MAPA) in the mixture. Approximate enthalpies of absorption of CO2 in all the tested aqueous amine systems were estimated from the CO2 solubility data. The measured total pressure and the estimated CO2 solubility data can be useful in thermodynamic modeling of the capture systems when aqueous DEEA–MAPA solutions are used as capture solvents.