Mathematical simulation of a gas flow in the vicinity of the open end of a tube for harmonic oscillations of a piston at the resonance frequency at the other end of the tube

2017 ◽  
Vol 62 (11) ◽  
pp. 1634-1638 ◽  
Author(s):  
S. V. Bulovich
Keyword(s):  
Resonance Frequency ◽  
Mathematical Simulation ◽  
Gas Flow ◽  
The Other ◽  
Harmonic Oscillations

scholarly journals CO Gas-Induced Resonance Frequency Shift of ZnO-Functionalized Microcantilever in Humid Air

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Lia Aprilia ◽  
Ratno Nuryadi ◽  
Dwi Gustiono ◽  
Nurmahmudi ◽  
Arief Udhiarto ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Zinc Oxide ◽  
Water Vapor ◽  
Resonance Frequency ◽  
Frequency Shift ◽  
Hydrothermal Method ◽  
Gas Flow ◽  
Humid Air ◽  
Resonance Frequency Shift ◽  
Co Gas

Resonance frequency shift of a zinc oxide- (ZnO-) functionalized microcantilever as a response to carbon monoxide (CO) gas has been investigated. Here, ZnO microrods were grown on the microcantilever surface by a hydrothermal method. The measurement of resonance frequency of the microcantilever vibrations due to the gas was carried out in two conditions, that is, gas flow with and without air pumping into an experiment chamber. The results show that the resonance frequency of the ZnO-functionalized microcantilever decreases because of CO in air pumping condition, while it increases when CO is introduced without air pumping. Such change in the resonance frequency is influenced by water vapor condition, and a possible model based on water-CO combination was proposed.

Microstructure and Hydrogen Permeability of Duplex Phase M-ZrNi (M=V, Nb, Ta) Alloys

2006 ◽  
Vol 980 ◽  
Author(s):  
Kazuhiro Ishikawa ◽  
Naoshi Kasagami ◽  
Tomoyuki Takano ◽  
Kiyoshi Aoki
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
High Performance ◽  
Gas Flow ◽  
Hydrogen Permeation ◽  
Hydrogen Permeability ◽  
The Other ◽  
Cast State ◽  
X Ray ◽  
Scanning Electron

AbstractIn order to develop non-Pd based high performance hydrogen permeation alloys, microstructure, crystal structure and hydrogen permeability of duplex phase M-ZrNi (M=V and Ta) alloys were investigated using a scanning electron microscope, an X-ray diffractometer and a gas flow meter. These results were compared with those of Nb-ZrNi ones which have been previously published. The hydrogen permeation was impossible in the V-ZrNi alloys, because they were brittle in the as-cast state. On the other hand, duplex phase alloys consisting of the bcc-(Ta, Zr) solid solution and the orthorhombic ZrNi (Cmcm) intermetallic compound were formed and hydrogen permeable in the Ta-ZrNi system. The Ta40Zr30Ni30 alloy shows the highest value of hydrogen permeability of 4.1×10-8 [molH2m-1s-1Pa-0.5] at 673 K, which is three times higher than that of pure Pd.

Direct molecular hydrogen sulphide scrubbing with hollow fibre membranes

2001 ◽  
Vol 44 (9) ◽  
pp. 135-142 ◽  
Author(s):  
N. Boucil ◽  
B. Jefferson ◽  
S.A. Parsons ◽  
S.J. Judd ◽  
R.M. Stuetz
Keyword(s):  
Mass Transfer ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Flow Rate ◽  
Hydrogen Sulphide ◽  
Gas Flow ◽  
Hollow Fibre ◽  
The Other ◽  
Gas Flow Rate

The emission of hydrogen sulphide is a major problem associated with anaerobic treatment of sulphate and sulphite containing wastewaters. Conventional absorbing processes, such as packed towers, spray towers or bubble columns, are all constrained by factors such as flooding and foaming. Membrane systems, on the other hand, enable independent control of the liquid and gas flow rate and a step change order of magnitude increase in the specific surface area of the contact process. The membrane acts as a gas absorber with a design similar to a shell and tube heat exchanger. On the other hand, they are limited by facets of the membrane such as its resistance to mass transfer and permselectivity, as well as its cost. The work presented in this paper refers to an absorption process based on a non-wetted hollow fibre membrane for the scrubbing of hydrogen sulphide from air, with water as the contact solvent. Results presented describe the performance of the unit in terms of overall transfer and outlet liquid concentration as a function of circulation regime, gas flow rate, liquid flow rate and specific surface area. In particular, results are presented using traditional plots of Sherwood number (Sh) against Graetz (Gr) number for the liquid flowing in the lumens, such that experimental and available empirical descriptions of the process performance are directly compared. Results suggest that, as expected, very efficient mass transfer is obtained. However, the mass transfer was found to reach a maximum value against Gr, contrary to available empirical models.

Calculations of Cooled Turbine Efficiency

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
J. H. Horlock ◽  
Leonardo Torbidoni
Keyword(s):  
Film Cooling ◽  
Gas Flow ◽  
Coolant Flow ◽  
The Other ◽  
Turbine Stage ◽  
Isentropic Expansion ◽  
Turbine Efficiency ◽  
Flow Through ◽  
Definition Of ◽  
Industrial Gas Turbine

The efficiency of a cooled turbine stage has been discussed in the literature. All proposed definitions compare the actual power output with an ideal output, which has to be determined; but usually, one of two definitions has been used by turbine designers. In the first, the so-called Hartsel efficiency, the mainstream gas flow, and the various coolant flows to rotor and stator are assumed to expand separately and isentropically to the backpressure. In the second, it is assumed that these flows mix at constant (mainstream) gas pressure before expanding isentropically (sometimes, the rotor coolant flow is ignored in this definition). More recently, it has been suggested that a thermodynamically sounder definition is one in which the gas and coolant flows mix reversibly and adiabatically before isentropic expansion to the backpressure. In the current paper, these three efficiencies are compared, for a typical stage—the first cooled stage of a multistage industrial gas turbine. It is shown that all the efficiencies fall more or less linearly with increase of the fractional (total) coolant flow. It is also shown that the new definition of efficiency gives values considerably lower than the other two efficiencies, which are more widely used at present. Finally, the various irreversibilities associated with the flow through a cooled turbine are calculated. Although all these irreversibilities increase with the fractional coolant flow, it is shown that the “thermal” irreversibility associated with film cooling is higher than the other irreversibilities at large fractional coolant flow.

An analytical and experimental investigation of the trajectories of particles entrained by the gas flow in nozzles

1969 ◽  
Vol 35 (3) ◽  
pp. 549-559 ◽  
Author(s):  
John H. Neilson ◽  
Alastair Gilchrist
Keyword(s):  
Gas Flow ◽  
Particle Trajectory ◽  
Approximate Analytical Solution ◽  
The Other ◽  
Particle Flow ◽  
Conical Nozzle ◽  
Small Particles ◽  
Erosion Damage ◽  
Particle Flows ◽  
The Moment

Among the parameters which determine the erosion damage sustained by the walls of a nozzle in which a mixture of gas and particles is flowing, is the angle between the direction of the particle flow and the wall surface at the moment of impact. In this work an approximate analytical solution is made for a number of gas particle flows to determine broadly the features on which particle trajectory depends and some experimental results are given which confirm the theoretical computations. It is shown that the divergent region of a conical nozzle is unlikely to suffer a severe particle attack but that for parallel flow convergent-divergent nozzles the convex region near the exit may be affected. The choke, on the other hand, is most susceptible to particle attack even by fairly small particles. It may be said, in general, that any particle which enters the choke section with a velocity which, in the absence of effects from the gas would allow the particle to strike the choke wall, will in fact hit the wall at some point along the length of the choke.

The Dynamics of Second Ring Flutter and Collapse in Modern Diesel Engines

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Chao Cheng ◽  
Harold Schock ◽  
Dan Richardson
Keyword(s):  
Diesel Engine ◽  
Gas Flow ◽  
Piston Ring ◽  
Sensitivity Study ◽  
The Other ◽  
Heavy Duty ◽  
Oil Consumption ◽  
Ring Dynamics ◽  
Heavy Duty Diesel Engine ◽  
Heavy Duty Diesel

Second ring fluttering and radial ring collapse are recognized as having significant influences on engine blowby and oil consumption. As the gas flow is coupled with the piston ring motion, understanding the ring dynamics is important for understanding not only the engine blowby mechanism, but also oil consumption mechanisms and how to control them. Only second ring flutter and collapse that occurs around the top dead center (TDC) firing conditions is examined in this paper based on a modern heavy-duty diesel engine. However, the principles described are equally applicable to all engines. First, the authors describe the fundamental mechanisms of how second ring fluttering and radial ring collapse occur. This is described by examining the forces that are acting on the second ring. Then, two cases are shown. One case shows second ring flutter and the other case shows stable second ring motion. The reasons for these two different cases are explained, including the effect of static twist and the end gaps of the rings. A sensitivity study was performed to evaluate the effect of changing the top and second ring end gaps on ring lift. It was shown how the gaps could affect the second ring flutter and ring collapse. It is concluded that the second ring will be more likely to flutter or collapse if it has a negative static twist, if the second ring end gap is large, and/or if the top ring end gap is small. If the second ring does not flutter, it may still be possible to design the ring pack such that there is not any reverse blowby. However, this must be carefully studied and controlled or the second land pressures will be too high, resulting in reverse blowby and/or top ring lifting.

scholarly journals Modeling the conjugate problem of heat transfer at hot jet impingement onto a cooled surface

2021 ◽  
Vol 2119 (1) ◽  
pp. 012157
Author(s):  
V V Lukashov ◽  
V S Naumkin
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Flat Plate ◽  
Gas Flow ◽  
Jet Impingement ◽  
Conjugate Problem ◽  
Heat Fluxes ◽  
The Other ◽  
Local Maxima ◽  
The Impact

Abstract The paper solves the problem of thermal conductivity inside a flat plate under the impact of a hot jet of nitrogen impinging from one side and cooled by a gas flow from the other side. In this formulation of the problem, there may be local maxima and minima of the temperature inside the plate, caused by an uneven distribution of heat fluxes along the plate.

scholarly journals Impact of the Sensor Temperature on Low Acetone Concentration Detection Using AlGaN/GaN HEMTs

2020 ◽  
Vol 2 (1) ◽  
pp. 58
Author(s):  
Ali Ahaitouf ◽  
Yacine Halfaya ◽  
Suresh Sundaram ◽  
Simon Gautier ◽  
Paul Voss ◽  
...  
Keyword(s):  
High Temperature ◽  
Memory Effect ◽  
Gas Flow ◽  
Sensor Response ◽  
The Other ◽  
Acetone Concentration ◽  
Gan Hemt ◽  
Sensor Temperature ◽  
Acetone Detection ◽  
Large Response

In this work, we report on AlGaN/GaN HEMT sensors for acetone concentration below 100ppm and in a broad range of the sensor temperature varying from RT to 300 ∘C. At RT, in the presence of acetone, a smooth and monotonic decrease of the current is observed with a rather large response of 15A/ppm and with a large response time (several minutes) and memory effect. At a high temperature (300 ∘C), a current decrease is first observed just after the acetone injection, then followed by an increase, which saturates and stabilizes at a constant value. In order to clarify this unexpected behaviour, a detailed study of the sensor response versus the temperature and acetone injection flow is carried out. The outcome of this investigation is that a competition between the current variations induced by both the sensor and gas flow temperature difference from one side and the acetone dipolar moment from the other side can explain this transient. Our study highlights that AlGaN/GaN HEMT-based sensors allow for very sensitive acetone detection at both room and high temperatures. Nevertheless, care must be taken during the characterization and operation of such sensors especially at high operating temperatures. On the other hand, the high temperature operation helps to improve the sensor response and suppress the memory effect.

Predicting the temperature distribution and suction gas superheating of an oil-free linear compressor

2016 ◽  
Vol 231 (1) ◽  
pp. 47-56 ◽  
Author(s):  
MJ Oliveira ◽  
MC Diniz ◽  
CJ Deschamps
Keyword(s):  
Temperature Distribution ◽  
Gas Flow ◽  
The Other ◽  
Design Parameters ◽  
Linear Compressor ◽  
Discharge System ◽  
Experimental Calibration ◽  
Compression Cycle ◽  
Volume Method ◽  
Good Agreement

It is well established that the volumetric and isentropic efficiencies of reciprocating compressors used for household refrigeration are significantly reduced by suction gas superheating. Moreover, excessive levels of temperature may affect the reliability of some components, such as the electrical motor. This paper reports a modeling approach to predict the temperature distribution in the gas and solid components of an oil-free linear compressor. A simulation model based on the finite volume method was used to solve the heat conduction in the solid components and gas flow inside the compressor. On the other hand, the compression cycle in the cylinder was solved with a transient lumped formulation, but in a coupled manner with the remainder of the solution domain. The prediction of the suction gas superheating obtained with the model was in good agreement with the measurements, despite discrepancies being observed in some solid components and in the gas path along the discharge system. The model does not require any experimental calibration and hence is suitable to analyze different compressor designs. To illustrate this, the model was applied to predict the temperature distribution with respect to two design parameters.

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