Showing papers on "Total pressure published in 2015"
TL;DR: In this paper, a numerical study has been performed to investigate the film-cooling heat reduction performance of a single jet (diameter 2mm and 09mm), and an array forward facing of micro-jets of the same effective area (corresponding to the respective single jet).
98 citations
TL;DR: In this paper, the influence of oxygen flow rate and total pressure on the film structure and its preferred orientation has been studied by combining X-ray diffraction and Raman spectrometry.
47 citations
TL;DR: In this article, the authors demonstrate using liquid inertia force in a taper gap microchannel geometry to provide a high level of heat dissipation capacity accompanied by a high heat transfer coefficient and low pressure drop during flow boiling.
Abstract: In this paper, we demonstrate using liquid inertia force in a taper gap microchannel geometry to provide a high level of heat dissipation capacity accompanied by a high heat transfer coefficient and low pressure drop during flow boiling. The high mass flux increases liquid inertia force and promotes vapor removal from the manifold, thereby increasing critical heat flux (CHF) and heat transfer coefficient. The tapered gap above the microchannels provides an increasing cross-sectional area in the flow direction. This gap allows bubbles to emerge from microchannels and expand within the gap along the flow direction. The bubble evaporation and expansion in tapered gap causes pressure recovery and reduces the total pressure drop. The pressure recovery increases with the increased evaporation rate at higher heat fluxes. Using a 6% taper and a moderately high inlet liquid flow Reynolds number of 1095, we have reached a CHF of 1.07 kW/cm2 with a heat transfer coefficient of 295 kW/m2 °C and a pressure drop of 30 kPa.
44 citations
TL;DR: In this article, a directconnect experiment and numerical simulation investigations on combustion mode transition were completed for inflow conditions of Mach number 3.0, total temperature 1500 K and total pressure 2.1 MPa.
41 citations
TL;DR: In this article, the impact of non-steady outflow conditions on the compressor stator flow that is forced through a mimic in the wake of a linear low speed cascade to simulate the conditions that would be expected in a pulsed detonation engine was discussed.
Abstract: This contribution discusses the impact of a non-steady outflow condition on the compressor stator flow that is forced through a mimic in the wake of a linear low speed cascade to simulate the conditions that would be expected in a pulsed detonation engine. 2D/3C-PIV measurements were made to describe the flow field in the passage. Detailed wake measurements provide information about static pressure rise as well as total pressure loss. The stator profile used for the investigations is highly loaded and operates with three-dimensional flow separations under design conditions and without active flow control. It is shown that side wall actuation helps to stabilize the flow field at every phase angle and extends the operating range of the compressor stator. Furthermore, the static pressure gain can be increased by 6% with a 4% loss reduction in time averaged data.Copyright © 2015 by ASME
38 citations
TL;DR: In this article, an analytic model of the heliosheath between the termination shock (TS) and the heliopause (HP) is developed in the limit in which the interstellar flow and magnetic field are neglected.
Abstract: An analytic model of the heliosheath (HS) between the termination shock (TS) and the heliopause (HP) is developed in the limit in which the interstellar flow and magnetic field are neglected. The heliosphere in this limit is axisymmetric and the overall structure of the HS and HP is controlled by the solar magnetic field even in the limit in which the ratio of the plasma to magnetic field pressure, β = 8πP/B{sup 2}, in the HS is large. The tension of the solar magnetic field produces a drop in the total pressure between the TS and the HP. This same pressure drop accelerates the plasma flow downstream of the TS into the north and south directions to form two collimated jets. The radii of these jets are controlled by the flow through the TS and the acceleration of this flow by the magnetic field—a stronger solar magnetic field boosts the velocity of the jets and reduces the radii of the jets and the HP. MHD simulations of the global heliosphere embedded in a stationary interstellar medium match well with the analytic model. The results suggest that mechanisms that reduce the HS plasma pressure downstream of the TS can enhance themore » jet outflow velocity and reduce the HP radius to values more consistent with the Voyager 1 observations than in current global models.« less
37 citations
TL;DR: In this paper, the thermal-hydraulic performance of a 600MW supercritical circulating fluidized bed (CFB) boiler with complex furnace structure is treated as a simplified series-parallel flow network, which consists of parallel flow loops, pressure nodes and connecting tubes.
35 citations
TL;DR: In this article, Extended UNIQUAC model parameters optimized for the CO 2 -MDEA-H 2 O system are presented, which accurately represents thermodynamic and thermal properties of the studied systems.
34 citations
TL;DR: In this article, an experimental study on heat transfer and pressure drop for R417A flow boiling in horizontal smooth and internally grooved tubes was conducted, and the influence of vapor quality and mass flux on the heat transfer performance was analyzed and discussed.
32 citations
Journal Article•
TL;DR: In this paper, an analytic model of the heliosheath between the termination shock (TS) and the heliopause (HP) is developed in the limit in which the interstellar flow and magnetic field are neglected, and the results suggest that mechanisms that reduce the HS plasma pressure downstream of the TS can enhance jet outflow velocity and reduce the HP radius to values more consistent with the Voyager 1 observations than in current global models.
Abstract: An analytic model of the heliosheath (HS) between the termination shock (TS) and the heliopause (HP) is developed in the limit in which the interstellar flow and magnetic field are neglected The heliosphere in this limit is axisymmetric and the overall structure of the HS and HP is controlled by the solar magnetic field even in the limit in which the ratio of the plasma to magnetic field pressure, β = 8πP/B{sup 2}, in the HS is large The tension of the solar magnetic field produces a drop in the total pressure between the TS and the HP This same pressure drop accelerates the plasma flow downstream of the TS into the north and south directions to form two collimated jets The radii of these jets are controlled by the flow through the TS and the acceleration of this flow by the magnetic field—a stronger solar magnetic field boosts the velocity of the jets and reduces the radii of the jets and the HP MHD simulations of the global heliosphere embedded in a stationary interstellar medium match well with the analytic model The results suggest that mechanisms that reduce the HS plasma pressure downstream of the TS can enhance themore » jet outflow velocity and reduce the HP radius to values more consistent with the Voyager 1 observations than in current global models« less
32 citations
TL;DR: In this paper, it was shown that droplets are broken up only in the first orifice, and the second orifice delivers back-pressure being responsible for a change in the cavitation pattern found after the first one.
TL;DR: In this paper, a series of simultaneous measurements of the free-surface fluctuations, jump toe oscillations, void fraction and total pressure variations allowed for an investigation of the interactions between these characteristics.
TL;DR: In this paper, the authors proposed a new theoretical model based on local thermodynamic equilibrium enabling the prediction of gas generation during the reaction of aluminum-based thermites and demonstrated that the model has the capability to predict the total pressure and its partial pressure components as a function of the reaction extent and compaction.
Abstract: The paper proposes a new theoretical model based on local thermodynamic equilibrium enabling the prediction of gas generation during the reaction of aluminum-based thermites. We demonstrate that the model has the capability to predict the total pressure and its partial pressure components as a function of the reaction extent and compaction. Al/CuO, Al/Bi2O3, Al/Sb2O3, Al/MoO3 and Al/WO3 thermites are modeled and their capability to generate pressure compared. Simulation results are also validatedthrough dedicated experiments and showgeneral agreement beyond the state of the art. Mechanisms underlying pressure generation are detailed. A two-stage process for the pressure increase in Al/CuO reaction,also observed experimentally,is shown to be driven by oxygen generation as produced byCuO and Cu2O vaporizationthrough different kinetics. Comparison with experiment stresses the issue of the understanding of the complex chemical processes taking place during vaporization and subsequent gas phase reactions and the need to determine their thermodynamicconstants.
22 Jun 2015
TL;DR: In this paper, the authors focused on the generation and interaction of internal flow structures, jet oscillation process, and pressure drop mechanism of a Sweeping Jet Actuator and performed timedependent numerical analysis over a range of inlet mass flow rates.
Abstract: This study focuses on the generation and interaction of internal flow structures, jet oscillation process, and pressure drop mechanism of a Sweeping Jet Actuator. Timedependent numerical analysis was performed over a range of inlet mass flow rates. The effect of varying inlet mass flow rate on the sweeping jet oscillation frequency was calculated and a strong agreement was found with the experimental measurements. The velocity, temperature and pressure fields are provided. The complex flow field inside the Sweeping Jet Actuator for half an oscillation cycle are presented by velocity magnitude and total pressure contours. Formation of vortices from sharp corners in the actuator core surfaces were observed, and their role in jet oscillation is shown.
TL;DR: In this paper, the effects of total pressure on film density, chemical composition, and TFT characteristics were investigated in the case of a-IGZO thin-film transistors.
Abstract: Amorphous In–Ga–Zn–O (a-IGZO) thin-film transistors (TFTs) are employed in current flat-panel displays. It is known that deposition conditions and post-deposition thermal annealing affect structure and electrical properties of a-IGZO thin films. It was previously reported that total pressure during sputter-deposition deteriorates subthreshold swing, defect density and operation characteristics of a-IGZO TFTs. Here, we provide comprehensive results on effects of total pressure on film density, chemical composition, and TFT characteristics. Rutherford backscattering measurements detected a small amount of argon incorporated in all of the a-IGZO films. We found that increasing the total pressure deteriorated TFT characteristics; i.e., saturation mobility was dropped from 10 to 4 ${\hbox{cm}}^{2}/({\hbox{V}}\cdot {\hbox{s}})$ , subthreshold swing was increased from 0.2 to 0.5 V/dec, and threshold voltage was positive-shifted from 2 to 15 V. It is related to increased oxygen concentration and decreased weight density of the a-IGZO films. Thermal desorption spectra showed that amounts of weakly-bonded oxygen increased as the total pressure increased, which is considered to be related to the TFT deterioration.
TL;DR: In this article, a laser-induced underwater shock wave with a special attention to pressure impulse, the time integral of pressure evolution, was examined with a combined measurement system that obtains high-resolution nanosecond-order image sequences.
Abstract: We experimentally examine a laser-induced underwater shock wave with a special attention to pressure impulse, the time integral of pressure evolution. %total pressure variation associated with the shock wave. Plasma formation, shock-wave expansion, and pressure in water are observed simultaneously using a combined measurement system that obtains high-resolution nanosecond-order image sequences. These detailed measurements reveal a non-spherically-symmetric distribution of pressure peak. In contrast, remarkably, pressure impulse is found to distribute symmetrically for a wide range of experimental parameters even when the shock waves are emitted from an elongated region. The structure is determined to be a collection of multiple spherical shock waves originated from point-like plasmas in the elongated region.
TL;DR: In this paper, a computational fluid dynamics (CFD) model of the filter was developed and validated using experimental data and a new underdrain design and packing strategy was proposed which could reduce the overall pressure drop in the filter by 35%.
TL;DR: In this article, the authors investigated the gasification characteristics of lignite-char with steam, CO2 and their mixture in a pressurized fixed bed (PFB) reactor at different pressures.
TL;DR: In this article, a series of niobium oxide thin films was deposited by reactive magnetron sputtering, and the total pressure of Ar/O 2 was kept constant at 1/Pa, while the O 2 partial pressure was varied up to 0.2
TL;DR: In this article, a kinematic model was developed to predict axial solid holdup profile and the reduced solid flux model developed by Rhodes et al. (1992) was employed to predict the mass fraction of upwards flowing solids.
TL;DR: In this article, a linear relationship between the shear viscosity and the total pressure, a constant single relaxation time for a Maxwell-type viscoelastic fluid, and a unidirectional velocity profile are the major assumptions made in order to study the steady-state isothermal and pressure-driven flows in straight channels and circular tubes.
Abstract: A linear relationship between the shear viscosity and the total pressure, a constant single relaxation time for a Maxwell-type viscoelastic fluid, and a unidirectional velocity profile are the major assumptions made in the present work in order to study the steady-state isothermal and pressure-driven flows in straight channels and circular tubes. Despite their non-linearity the final partial differential equations that govern the flows are solved analytically, and the dependence of all the primary flow variables on the geometrical aspect ratio, the dimensionless pressure-viscosity coefficient and the Weissenberg number is revealed explicitly. It is demonstrated that the pressure-dependent viscosity slightly affects the velocity profile, changes substantially the pressure gradient along the main flow direction, generates another normal to the wall, and it is responsible for significant variations of the extra-stresses along both spatial directions. An exponential increase of the viscosity, relative to its reference value, is predicted as the distance from the exit of the channel/tube increases. As a consequence, the average pressure difference, required to drive the flow and the shear stress at the wall increase substantially compared to that predicted by the classic Hagen–Poiseuille law. Last, it is revealed that the solution of the governing equations ceases to exist when the Weissenberg number reaches a threshold.
TL;DR: In this article, the synergetic benefits of simultaneous formation fluid extraction during CO 2 injection for reservoir pressure management by coupled hydro-mechanical simulations at the prospective Vedsted storage site located in northern Denmark were investigated.
Abstract: We assessed the synergetic benefits of simultaneous formation fluid extraction during CO 2 injection for reservoir pressure management by coupled hydro-mechanical simulations at the prospective Vedsted storage site located in northern Denmark. Effectiveness of reservoir pressure management was investigated by simulation of CO 2 storage without any fluid extraction as well as with 66% and 100% equivalent volume formation fluid extraction from four wells positioned for geothermal heat recovery. Simulation results demonstrate that a total pressure reduction of up to about 1.1 MPa can be achieved at the injection well. Furthermore, the areal pressure perturbation in the storage reservoir can be significantly decreased compared to the simulation scenario without any formation fluid extraction. Following a stress regime analysis, two stress regimes were considered in the coupled hydro-mechanical simulations indicating that the maximum ground surface uplift is about 0.24 m in the absence of any reservoir pressure management. However, a ground uplift mitigation of up to 37.3% (from 0.24 m to 0.15 m) can be achieved at the injection well by 100% equivalent volume formation fluid extraction. Well-based adaptation of fluid extraction rates can support achieving zero displacements at the proposed formation fluid extraction wells located close to urban infrastructure. Since shear and tensile failure do not occur under both stress regimes for all investigated scenarios, it is concluded that a safe operation of CO 2 injection with simultaneous formation fluid extraction for geothermal heat recovery can be implemented at the Vedsted site.
TL;DR: In this paper, the effect of the difference between the advancing and receding contact angles on the pressure drop in capillaries (minichannels and microchannels) for liquid-liquid and gas-liquid systems is analyzed.
Abstract: The effect of the difference between the advancing and receding contact angles (the phenomenon known as contact-angle hysteresis or wetting hysteresis) on the pressure drop in capillaries (minichannels and microchannels) for liquid–liquid and gas–liquid systems is analyzed. It is shown that, in microchannels, for cases of a continuous medium that both does and does not wet the walls, the pressure drop has a positive sign. A relationship is proposed for estimating the dynamic receding contact angle, which is the monotone extension of a similar relationship for the advancing contact angle. The region of the allowable values of the capillary numbers for these equations is found. The fraction of the pressure drop in capillaries due to contact-angle hysteresis in the total pressure drop is estimated.
TL;DR: In this article, a set of time-resolved steam flowfield measurements from the exit of the last two stages of a low pressure (LP) steam turbine under various volumetric massflow conditions were performed in the steam turbine test facility in Hitachi city in Japan.
Abstract: Modern steam turbines need to operate efficiently and safely over a wide range of operating conditions. This paper presents a unique unprecedented set of time-resolved steam flowfield measurements from the exit of the last two stages of a low pressure (LP) steam turbine under various volumetric massflow conditions.The measurements were performed in the steam turbine test facility in Hitachi city in Japan. A newly developed fast response probe equipped with a heated tip to operate in wet steam flows was used. The probe tip is heated through an active control system using a miniature high-power cartridge heater developed in-house.Three different operating points, including two reduced massflow conditions, are compared and a detailed analysis of the unsteady flow structures under various blade loads and wetness mass fractions is presented. The measurements show that at the exit of the second to last stage the flow field is highly three dimensional. The measurements also show that the secondary flow structures at the tip region (shroud leakage and tip passage vortices) are the predominant sources of unsteadiness at 85% span. The high massflow operating condition exhibits the highest level of periodical total pressure fluctuation compared to the reduced massflow conditions at the inlet of the last stage. In contrast at the exit of the last stage, the reduced massflow operating condition exhibits the largest aerodynamic losses near the tip. This is due to the onset of the ventilation process at the exit of the LP steam turbine. This phenomenon results in 3 times larger levels of relative total pressure unsteadiness at 93% span, compared to the high massflow condition. This implies that at low volumetric flow conditions the blades will be subjected to higher dynamic load fluctuations at the tip region.Copyright © 2015 by ASME
TL;DR: In this paper, the authors investigated the effect of total pressure on CO2 absorption and ammonia vaporization in ammonia solutions on a wetted-wall column and found that the elevated pressure absorption process was an effective way to increase CO 2 absorption rate and suppress ammonia vaporisation at the same time.
Abstract: The low CO2 absorption rate and high ammonia volatile loss rate are two major issues for the ammonia-based CO2 capture technology. In this work, we investigated the effect of total pressure on CO2 absorption and ammonia vaporization in ammonia solutions on a wetted-wall column. We found that the elevated pressure absorption process was an effective way to increase CO2 absorption rate and suppress ammonia vaporization at the same time. We also studied the mass transfer mechanism at elevated pressure and found the overall mass transfer coefficients of CO2 absorption in both ammonia and MEA solutions at elevated pressures were lower than that under atmospheric pressure. The overall mass transfer coefficients of CO2 absorption in 3 M NH3 (298 K) at 1, 1.5, 2, 2.5 bar were 0.723 × 10−6, 0.652 × 10−6, 0.591 × 10−6, 0.555 × 10−6 mol/(s m2 Pa) and the corresponding gas side mass transfer coefficients were 13.8 × 10−6, 4.52 × 10−6, 2.61 × 10−6, 2.03 × 10−6 mol/(s m2 Pa), respectively. We also found the gas side mass transfer coefficient in the wetted-wall column was not only dependent on the hydrodynamic conditions of the column but also influenced by the total pressure. © 2014 Society of Chemical Industry and John Wiley & Sons, Ltd
TL;DR: The design methodology presented here combines an evolutionary principle with a three-dimensional CFD flow solver to generate different geometric profiles of the hub systematically to improve the performance of the cascade.
Abstract: This paper describes the design of a non-axisymmetric hub contouring in a shroudless axial flow compressor cascade operating at near stall condition. Although, an optimum tip clearance reduces the total pressure loss, further reduction in the loss was achieved using hub contouring. The design methodology presented here combines an evolutionary principle with a three-dimensional CFD flow solver to generate different geometric profiles of the hub systematically. The resulting configurations were preprocessed by GAMBIT © and subsequently analyzed computationally using ANSYS Fluent ©. The total pressure loss coefficient was used as a single objective function to guide the search process for the optimum hub geometry. The resulting three dimensionally complex hub promises considerable benefits discussed in detail in this paper. A reduction of 15.2% and 16.23% in the total pressure loss and secondary kinetic energy, respectively, is achieved in the wake region. An improvement of 4.53% in the blade loading is observed. Other complimentary benefits are also listed in the paper. The majority of the benefits are obtained away from the hub region. The contoured hub not only alters the pitch-wise static pressure gradient but also acts as a vortex generator in an effort to alleviate the total pressure loss. The results confirm that non-axisymmetric contouring is an effective method for reducing the losses and thereby improving the performance of the cascade.
TL;DR: Results show that coupling of the structural waves scattered by the inhomogeneities plays an important role in modifying the sound absorption and scattering of surface sound pressure, especially at low frequencies and/or the resonance frequencies of the trapped modes of the plate.
Abstract: This paper extends previous work of Zhang and Pan [J. Acoust. Soc. Am. 133(4), 2082–2096 (2013)] on sound scattering and absorption by an underwater coated plate with a single attached distributed-inhomogeneity to that with periodically located distributed-inhomogeneities. A comparison is made among cases of a plate without inhomogeneities, a plate with inhomogeneities, and one with inhomogeneities ignoring the mutual coupling. Results show that coupling of the structural waves scattered by the inhomogeneities plays an important role in modifying the sound absorption and scattering of surface sound pressure, especially at low frequencies and/or the resonance frequencies of the trapped modes of the plate. The sound absorption of the plate is dependent on the distance between the adjacent inhomogeneities, the length of the inhomogeneity, and the angle of the incident sound. On the surface of the inhomogeneities, the scattered/total sound pressure is generally enhanced. On the surface in between the inhomogeneities, the pressure is also enhanced at low frequencies but is nearly unchanged at higher frequencies. Results also show that the coupling-induced variation of scattered/total pressure is significant only at the resonance frequencies of the global modes and trapped modes. The surface normal velocity is presented to explain the coupling-induced variations in the vibration and pressure fields.
TL;DR: The equilibrium magnetopause location on the dayside is determined by the balance of pressure forces as discussed by the authors, and a physics-based global magnetohydrodynamic (MHD) is used to examine contributions of different terms to this balance.
TL;DR: In this paper, the effect of total pressure and mercury to thallium atomic ratio on transports coefficients such as thermal conductivity, viscosity and electric conductivity of a HgTlI discharge lamp was studied.
Abstract: The aim of this paper is the study of the effect of total pressure and mercury to thallium atomic ratio on transports coefficients such as thermal conductivity, viscosity and electric conductivity of a HgTlI discharge lamp. For this, a chemical model under Local Thermodynamic Equilibrium conditions has been developed to compute the plasma composition and transports coefficients using the theoretical approach of Chapman completed by the work of Enskog, Hirschfelder and Devoto. It has been shown that the variation of the two parameters has a significant effect on the transport coefficients.
01 Jan 2015
TL;DR: In this article, a novel Entropy Wave Generator (EWG) is presented to simulate the entropy perturbations originated by gas turbine burners, which is based on the alternated injection of hot/cold air upstream of the turbine, by using a two-way rotary valve.
Abstract: The reduction of core-noise represents a crucial objective for the deployment of low noise propulsion systems. In this context the European Project RECORD - REsearch on COre noise ReDuction - aims at quantifying the impact of the turbine on direct and indirect combustion noise by means of a set of dedicated experiments carried out on an engine representative high pressure turbine, installed in the high-speed test rig of Politecnico di Milano (Italy). The aeroacoustic interaction of pressure, vorticity, and entropy waves with the turbine will be studied. This paper presents a novel Entropy Wave Generator (EWG) to simulate the entropy perturbations originated by gas turbine burners. The device, designed and manufactured by SMCPFA (Romania), is based on the alternated injection of hot/cold air upstream of the turbine, by using a two-way rotary valve. The entropy waves generated by the EWG were experimentally characterized in a dedicated test section at Politecnico di Milano. Tests were performed using different insulation systems, and investigating the propagation of entropy waves in both free-jet and immersed-jet configurations. Tests were performed by means of a fast thermocouple (frequency response ~300 Hz) and a pneumatic total pressure probe (frequency response ~400 Hz), specifically developed for the project. Results indicate that for an optimal feeding pressure the EWG generates circular-shaped spots of hot air characterized by a sinusoidal temperature fluctuation and weak pressure oscillations; the amplitude of the temperature oscillation reduces as the frequency increases, however resulting higher than 10 K at the engine-representative frequency of 100 Hz. This value matches the technical requirements of the EWG, making it suitable for entropy noise studies in the turbine test rig.