Diffusive and convective flow in a hydrogen-atom flow system

1968 ◽  
Vol 46 (24) ◽  
pp. 3899-3902 ◽  
Author(s):  
Philip B. Rudnick ◽  
Sidney Toby
Keyword(s):  
Hydrogen Atom ◽  
Surface Area ◽  
Flow Rate ◽  
Convective Flow ◽  
Total Pressure ◽  
Flow System ◽  
Linear Flow ◽  
Flow Signal ◽  
Concentration Time ◽  
Diffusive Flow

Diffusive and convective flow was studied in a hydrogen-atom flow system using an isothermal calorimetric detector. By varying detector area, total pressure, and linear flow rate, the importance of axial diffusion in the system was investigated. Under conditions of predominantly diffusive flow, signal–distance plots were independent of flow rate. When convective flow predominated, concentration–time plots were independent of flow rate. The efficiency of a detector was clearly dependent on its surface area within wide limits, but diffusion gradients produced by the presence of even large detectors did not appear to be important.

Studies on Downstream Stator With Rotor Re-Staggering and Forward Sweeping in a Subsonic Axial Compressor Stage

2011 ◽  
Author(s):  
P. V. Ramakrishna ◽  
M. Govardhan
Keyword(s):  
Flow Field ◽  
Computational Model ◽  
Flow Rate ◽  
Total Pressure ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Axial Distance ◽  
Compressor Stage ◽  
Numerical Work ◽  
Stagger Angle

The present numerical work studies the flow field in subsonic axial compressor stator passages for: (a) preceding rotor sweep (b) preceding rotor re-staggering (three stagger angle changes: 0°, +3° and +5°); and (c) stator sweeping (two 20° forward sweep schemes). The following are the motives for the study: at the off-design conditions, compressor rotors are re-staggered to alleviate the stage mismatching by adjusting the rows to the operating flow incidence. Fundamental to this is the understanding of the effects of rotor re-staggering on the downstream component. Secondly, sweeping the rotor stages alters the axial distance between the successive rotor-stator stages and necessitates that the stator vanes must also be swept. To the best of the author’s knowledge, stator sweeping to suit such scenarios has not been reported. The computational model for the study utilizes well resolved hexahedral grids. A commercial CFD package ANSYS® CFX 11.0 was used with standard k-ω turbulence model for the simulations. CFD results were well validated with experiments. The following observations were made: (1) When the rotor passage is closed by re-staggering, with the same mass flow rate and the same stator passage area, stators were subjected to negative incidences. (2) Effect of stator sweeping on the upstream rotor flow field is insignificant. Comparison of total pressure rise carried by the downstream stators suggests that an appropriate redesign of stator is essential to match with the swept rotors. (3) While sweeping the stator is not recommended, axial sweeping is preferable over true sweeping when it is necessary.

Transport of Particle-Laden Fluids Through Fixed-Valve Micropumps

1999 ◽  
Author(s):  
Ling-Sheng Jang ◽  
Christopher J. Morris ◽  
Nigel R. Sharma ◽  
Ron L. Bardell ◽  
Fred K. Forster
Keyword(s):  
Surface Charge ◽  
Surface Area ◽  
Flow Rate ◽  
Pure Water ◽  
Maximum Flow ◽  
Total Surface Area ◽  
Maximum Flow Rate ◽  
Number Density ◽  
Polystyrene Microspheres ◽  
Negative Surface

Abstract Micropumps designed for the flow-rate range of 100–1000μl/min have been developed by a number of research groups. However, little data is available regarding the ability of various designs to directly transport liquids containing particles such as cells, microspheres utilized for bead chemistry, or contaminants. In this study the ability of pumps with no-moving-parts valves (NMPV) to transport particles was investigated. The results showed that a NMPV micropump was able to directly pump suspensions of polystyrene microspheres from 3.1 to 20.3μm in diameter. The pump functioned without clogging at microsphere number densities as high as 9000 particles/μl of suspension, which corresponded to over 90,000 particles per second passing through the pump at a flow rate of 600μl/min. Performance with polystyrene microspheres was the same as pure water up to the point of cavitation. Microspheres manufactured with negative surface charge cavitated less readily that other microspheres studied that were manufactured without surface charge. However, cavitation did not appear to be a function of microsphere size, total surface area or number density. Thus pumping polystyrene microspheres was found to be more affected by surface effects than by size, surface area or number density within the range of parameters considered. In the case of charged microspheres, the maximum flow rate was reduced by 30% compared to pure water whereas for uncharged microspheres the maximum flow rate was reduced by approximately 80%.

Effect of Active Modulation of Through-Casing Coolant Injection on Turbine Efficiency

2017 ◽  
Author(s):  
Brian M. T. Tang ◽  
Marko Bacic ◽  
Peter T. Ireland
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Total Pressure ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Turbine Efficiency ◽  
Coolant Injection ◽  
Cooling Air

This paper presents a computational investigation into the impact of cooling air injected through the stationary over-tip turbine casing on overall turbine efficiency. The high work axial flow turbine is representative of the high pressure turbine of a civil aviation turbofan engine. The effect of active modulation of the cooling air is assessed, as well as that of the injection locations. The influence of the through-casing coolant injection on the turbine blade over-tip leakage flow and the associated secondary flow features are examined. Transient (unsteady) sliding mesh simulations of a one turbine stage rotor-stator domain are performed using periodic boundary conditions. Cooling air configurations with a constant total pressure air supply, constant mass flow rate and actively controlled total pressure supply are assessed for a single geometric arrangement of cooling holes. The effects of both the mass flow rate of cooling air and the location of its injection relative to the turbine rotor blade are examined. The results show that all of the assessed cooling configurations provided a benefit to turbine row efficiency of between 0.2 and 0.4 percentage points. The passive and constant mass flow rate configurations reduced the over-tip leakage flow, but did so in an inefficient manner, with decreasing efficiency observed with increasing injection mass flow rate beyond 0.6% of the mainstream flow, despite the over-tip leakage mass flow rate continuing to reduce. By contrast, the active total pressure controlled injection provided a more efficient manner of controlling this leakage flow, as it permitted a redistribution of cooling air, allowing it to be applied in the regions close to the suction side of the blade tip which more directly reduced over-tip leakage flow rates and hence improved efficiency. Cooling air injected close to the pressure side of the rotor blade was less effective at controlling the leakage flow, and was associated with increased aerodynamic loss in the passage vortex.

scholarly journals Effect of the Flame Dome Depth and Improvement of the Pressure Loss in the Dump Diffuser

1998 ◽  
Author(s):  
Shinji Honami ◽  
Wataru Tsuboi ◽  
Takaaki Shizawa
Keyword(s):  
Velocity Profile ◽  
Reynolds Stress ◽  
Flow Rate ◽  
Pressure Loss ◽  
Total Pressure ◽  
Flow Behavior ◽  
Sudden Expansion ◽  
Mean Velocity ◽  
The Mean ◽  
Stress Profiles

This paper presents the effect of flame dome depth on the total pressure performance and flow behavior in a sudden expansion region of the combustor diffuser without flow entering the dome head. The mean velocity and turbulent Reynolds stress profiles in the sudden expansion region were measured by a Laser Doppler Velocitmetry (LDV) system. The experiments show that total pressure loss is increased, when flame dome depth is increased. Installation of an inclined combuster wall in the sudden expansion region is suggested from the viewpoint of a control of the reattaching flow. The inclined combustor wall is found to be effective in improvement of the diffuser performance. Better characteristics of the flow rate distribution into the branched channels are obtained in the inclined wall configuration, even if the distorted velocity profile is provided at the diffuser inlet.

scholarly journals Numerical analysis of axial fan characteristics

Mechanik ◽  
2018 ◽  
Vol 91 (7) ◽  
pp. 606-608
Author(s):  
Stanisław Wrzesień ◽  
Michał Frant ◽  
Maciej Majcher
Keyword(s):  
Numerical Analysis ◽  
Numerical Methods ◽  
Flow Rate ◽  
Total Pressure ◽  
Volumetric Flow Rate ◽  
Total Efficiency ◽  
Axial Fan ◽  
Axial Fans ◽  
Basic Characteristics

The paper presents an analysis and comparison of basic characteristics of axial fans, both analytically and numerically. Such characteristics are: the characteristics of the total pressure, power and total efficiency as a function of the volumetric flow rate. The presented results showed significant quantitative and qualitative differences in the characteristics obtained by two methods. The usefulness of numerical methods in relation to the results of the initial analytical project was confirmed.

scholarly journals Effects of Surface Area and Flow Rate on Marine Bacterial Growth in Activated Carbon Columns

1982 ◽  
Vol 44 (2) ◽  
pp. 471-477 ◽  
Author(s):  
Robert J. Shimp ◽  
Frederic K. Pfaender
Keyword(s):  
Activated Carbon ◽  
Surface Area ◽  
Flow Rate ◽  
Bacterial Growth

Pressure Transient Analysis in an Elongated Linear Flow System

1984 ◽  
Author(s):  
C.A. Ehlig-Economides ◽  
M.J. Economides
Keyword(s):  
Transient Analysis ◽  
Flow System ◽  
Pressure Transient Analysis ◽  
Linear Flow ◽  
Pressure Transient

scholarly journals Effects of CO2 Bubble Size, CO2 Flow Rate and Calcium Source on the Size and Specific Surface Area of CaCO3 Particles

Energies ◽  
2015 ◽  
Vol 8 (10) ◽  
pp. 12304-12313 ◽  
Author(s):  
Jun-Hwan Bang ◽  
Kyungsun Song ◽  
Sangwon Park ◽  
Chi Jeon ◽  
Seung-Woo Lee ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Flow Rate ◽  
Bubble Size ◽  
Calcium Source ◽  
Co2 Flow

scholarly journals Microporosity Development of Herringbone Carbon Nanofibers by RbOH Chemical Activation

2009 ◽  
Vol 2009 ◽  
pp. 1-5 ◽  
Author(s):  
Vicente Jiménez ◽  
Paula Sánchez ◽  
Fernando Dorado ◽  
José Luís Valverde ◽  
Amaya Romero
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Carbon Nanofibers ◽  
Flow Rate ◽  
Chemical Activation ◽  
Micropore Volume ◽  
Structure Development ◽  
Activation Temperature ◽  
Activating Agent ◽  
Activation Conditions

The influence of different activation conditions, including activating agent/CNFs ratio, activation temperature, and He flow rate, on the pore structure development of herringbone carbon nanofibers (CNFs) was studied. The best results of activated CNFs with larger specific surface area can be achieved using the following optimized factors: RbOH/CNFs ratio = 4/1, activation temperature = ,and a He flow rate = 850 ml/min. The optimization of these three factors leads to high CNFs micropore volume, being the surface area increased by a factor of 3 compared to the raw CNFs. It is important to note that only the creation of micropores (ultramicropores principally) took place, and mesopores were not generated if compared with raw CNFs.

Solution Flow System for Hydrothermal-Electrochemical Synthesis: New Opportunities for Multilayered Oxide Films

1998 ◽  
Vol 517 ◽  
Author(s):  
W. Suchanek ◽  
T. Watanabe ◽  
B. Sakurai ◽  
M. Yoshimura
Keyword(s):  
Thin Films ◽  
Flow Rate ◽  
Electrochemical Synthesis ◽  
Single Phase ◽  
Flow System ◽  
Single Layer ◽  
Double Layers ◽  
Solution Flow ◽  
Additional Control ◽  
Multilayered Thin Films

AbstractA solution flow system for hydrothermal-electrochemical synthesis has been constructed in our laboratory. This equipment can operate at 20°-200°C, under the pressure of 1-50 atm., at flow rate of 1-50 cm3/min. Applicability of the flow system for low-temperature, hydrothermalelectrochemical synthesis of single-layer and multilayered thin films has been demonstrated using the BaTiO3-SrTiO3 system as an example. Single phase thin films as well as double layers have been deposited at 150°C, current density of 1 mA/cm2, and flow rates of 1-50 cm3/min. The flow rate is an important parameter allowing additional control of the films' morphology by affecting the growth rate. The multilayers can be prepared in only one experiment by simply changing the flowing solution. Processing using the solution flow cell may serve as an inexpensive and environmentally friendly way of fabricating any multilayered thin films, including magneto-optic films.

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