scholarly journals Calculation of acoustic flow-rate measurements error with the help of Fermat’s principle

2018 ◽  
Vol 211 ◽  
pp. 04007
Author(s):  
Alexander Petrov ◽  
Semyon Shkundin
Keyword(s):  
Control Systems ◽  
Cross Section ◽  
Flow Rate ◽  
Three Dimensional ◽  
Air Flow Rate ◽  
Velocity Measurements ◽  
Three Dimensional Flow ◽  
Automatic Control Systems ◽  
A Value ◽  
Flow Changes

The establishment of dispatching and automatic control systems for mine ventilation is impossible without the availability of perfect air flow rate sensors. Existing anemometers (tachometer, heat) do not meet these requirements. The error of average in cross section velocity measurements with such sensors reaches 15-20, sometimes 30%. The reason - the speed measured at one point is interpreted as the average over the cross section. The reliability of the sensors is small, because they are exposed to the damaging effect of a dusty atmosphere. Stationary installed anemometers clutter cross section, which is not always allowed. Fermat’s variational principle is used for derivation of the formula for the time of propagation of a sonic signal between two set points A and B in a steady three-dimensional flow of a fluid or gas. It is shown that the fluid flow changes the time of signal reception by a value proportional to the flow rate independently of the velocity profile. The time difference in the reception of the signals from point B to point A and vice versa is proportional with a high accuracy to the flow rate. It is shown that the relative error of the formula does not exceed the square of the largest Mach number. This makes it possible to measure the flow rate of a fluid or gas with an arbitrary steady subsonic velocity field

Experiments on Gas Ingestion Through Axial-Flow Turbine Rim Seals

2004 ◽  
Author(s):  
R. P. Roy ◽  
J. Feng ◽  
D. Narzary ◽  
P. Saurabh ◽  
R. E. Paolillo
Keyword(s):  
Flow Rate ◽  
Cfd Simulation ◽  
Air Flow ◽  
Three Dimensional ◽  
Axial Flow ◽  
Air Flow Rate ◽  
Three Dimensional Flow ◽  
Turning Angle ◽  
Time Average ◽  
The Many

It has been suggested by researchers that ingestion, through rim seals, of mainstream gas into axial-flow turbine disk cavities is a consequence of the prevailing unsteady three-dimensional flow field. The cause-effect relationship is complex — to help understand it, experiments were performed in a model single-stage turbine rig using two different vane-blade configurations. Selected measurements from one of the configurations were reported earlier (1999–2001). The second configuration is new, featuring smaller numbers of vanes and blades and a larger vane turning angle. Selected measurements are presented and compared to those from the first configuration. The measurements include: unsteady and time-average static pressure spatial distributions, and spatial distribution, in the rotor-stator cavity, of time-average ingestion. The parameters in the experiments were: main air flow rate, purge/seal air flow rate, and rotor speed. Unsteady three-dimensional CFD simulation may be helpful in identifying the roles of the many intertwined phenomena in the ingestion process.

Base-Vented Hydrofoils of Finite Span Under a Free Surface: An Experimental Investigation

1984 ◽  
Vol 28 (02) ◽  
pp. 90-106
Author(s):  
Jacques Verron ◽  
Jean-Marie Michel
Keyword(s):  
Experimental Investigation ◽  
Free Surface ◽  
Flow Rate ◽  
Cavity Length ◽  
Three Dimensional ◽  
Leading Edge ◽  
Pulsation Frequency ◽  
Cavity Pressure ◽  
Air Flow Rate ◽  
Cavity Configuration

Experimental results are given concerning the behavior of the flow around three-dimensional base-vented hydrofoils with wetted upper side. The influence of planform is given particular consideration so that the sections of the foils are simple wedges with rounded noses. Results concern cavity configuration, the relation between the air flow rate and cavity pressure, leading-edge cavitation, cavity length, pulsation frequency, and force coefficients.

scholarly journals Vehicular Quality Biomethane Production from Biogas by Using an Automated Water Scrubbing System

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
R. Chandra ◽  
V. K. Vijay ◽  
P. M. V. Subbarao
Keyword(s):  
Steady State ◽  
Control Systems ◽  
Flow Rate ◽  
Packed Bed ◽  
Operating Pressure ◽  
Absorption Column ◽  
Automatic Control Systems ◽  
Steady State Operation ◽  
Biomethane Production ◽  
Column Pressure

This paper presents the results of an automated water scrubbing system used for enrichment of methane content in the biogas, to produce vehicular grade biomethane fuel. Incorporation of automatic control systems for precisely regulating the water level and maintaining constant operating pressure in the packed bed absorption column of water scrubbing system resulted in steady-state operation of the scrubbing system and a consistent supply of methane-enriched biogas from the gas outlet. The improved automated water scrubbing system was found to enrich 97% methane at an operating column pressure of 1.0 MPa with 2.5 m3/h biogas in-flow rate and 2.0 m3/h water in-flow rate into the scrubbing column unit.

scholarly journals New Methods Used for the Smoothing of the Three-Dimensional Flow Behind the Turbine Nozzle Cascade

2021 ◽  
pp. 38-46
Author(s):  
Subotovich Subotovich ◽  
Alexander Lapuzin ◽  
Yuriy Yudin
Keyword(s):  
Kinetic Energy ◽  
Flow Rate ◽  
Three Dimensional ◽  
Scientific Paper ◽  
Radial Component ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
New Methods ◽  
Complex Criterion ◽  
Velocity Coefficient

To smooth the parameters of the three-dimensional flow behind the nozzle cascade new methods were suggested that allow us to sustain the flow rate, stagnation enthalpy and the axial projection of the moment of momentum for initial-, nonuniform and averaged flows. It was shown that the choice of the fourth integral characteristic (the kinetic energy, the entropy and the quantity of motion) has no particular significance because it has no effect on the complex criterion of the cascade quality, i.e. the velocity coefficient-angle cosine product that characterizes the level of the radial component of velocity. The minimum values of the velocity coefficient and the cosine angle satisfy the method that allows us to sustain the quantity of motion during the smoothing and the maximum values of the specified nozzle characteristics satisfy method 2 that enables the entropy maintenance. To evaluate the aerodynamic efficiency of the nozzle cascade the preference should be given to method 1 that enables the kinetic energy conservation and the velocity coefficient allows for the precise determination of the degree of loss of the kinetic energy that is equal to 3.6 % as for the example given in the scientific paper. As for method 1, the kinematic losses in the cascade are defined by the angle cosine that characterizes the level of the radial component of the velocity behind the cascade. For the example in question, kinematic losses are equal to 1.9 % and the complex criterion of quality equal to 0.972 corresponds to the overall losses of 5.5 %. It was suggested to use the velocity coefficient and the two angles of flow as integral cascade characteristics. The use of these characteristics enables the correct computations of the efficiency factor for the stage within the one-dimensional computation. The incisive analysis was performed for different methods used for the averaging of the parameters of the axially asymmetric flow behind the nozzle cascade. It was suggested to neglect the flow rate factor in the case of thermal computations done for the turbine stage.

Analysis of the Full Flow Field of Torque Converter

2012 ◽  
Vol 468-471 ◽  
pp. 674-677 ◽  
Author(s):  
Yu Long Lei ◽  
Chang Wang ◽  
Zheng Jie Liu ◽  
Xing Zhong Li
Keyword(s):  
Flow Field ◽  
Boundary Conditions ◽  
Flow Rate ◽  
Flow Model ◽  
Three Dimensional ◽  
Calculated Data ◽  
Torque Converter ◽  
Three Dimensional Flow ◽  
Sliding Mesh ◽  
Mesh Method

Establish the full three-dimensional flow model of the torque converter, proper mesh the model, select the appropriate boundary conditions, and use the sliding mesh method to deal with the interactions of the impeller, turbine, and reactor in different rotation speeds. Analysis the flow rate, pressure, and the loss of full flow field passage of the torque converter, elaborate the formation mechanism of the flow field, agreement with the experimental date compare to the calculated data, more accurate than the traditional single passage model compare to the full passage model, provide the direction of design optimization of the torque converter.

The Numerical Simulation Research of Gas Entrainment Based on Three-Dimensional Model

2017 ◽  
Author(s):  
Yilin Zhang ◽  
Shanfang Huang
Keyword(s):  
Experimental Data ◽  
Mass Flow Rate ◽  
Cross Section ◽  
Flow Rate ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Gas Entrainment ◽  
Simulation Results

Two kinds of three-dimensional model are built to simulate the gas entrainment process through a small break in the horizontal coolant pipe at the bottom of the stratified flow. The results were compared with the two-dimensional simulation results and the experimental data. In terms of the two-phase distribution, the simulation results agree well with the experimental data and show much superiority compared with the two-dimensional model. The results verify the reliability of model building, condition setting and calculating method qualitatively and quantitatively. In general, after gas entrainment, the average velocity over cross section increases obviously, but the mass flow rate decreases contrarily. This is because that void fraction meanwhile reduces the fluid density. In addition, it is found that the larger the void fraction of vapor is, the higher the average discharge velocity of the fracture cross-section fluid is. Besides, with the larger internal and external pressure difference, the gas volume fraction and the flow velocity in the break increase, resulting in the mass flow rate increasing along with them. However, since the critical height increases as well, the total loss amount of liquid in the stable effluent stage decreases, and the time before entrainment becomes shorter.

Effects of slowly varying meniscus curvature on internal flows in the Cassie state

2019 ◽  
Vol 872 ◽  
pp. 272-307 ◽  
Author(s):  
Simon E. Game ◽  
Marc Hodes ◽  
Demetrios T. Papageorgiou
Keyword(s):  
Liquid Metal ◽  
Small Parameter ◽  
Cross Section ◽  
Flow Rate ◽  
Pressure Difference ◽  
Liquid Metals ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Local Conditions ◽  
Cassie State

The flow rate of a pressure-driven liquid through a microchannel may be enhanced by texturing its no-slip boundaries with grooves aligned with the flow. In such cases, the grooves may contain vapour and/or an inert gas and the liquid is trapped in the Cassie state, resulting in (apparent) slip. The flow-rate enhancement is of benefit to different applications including the increase of throughput of a liquid in a lab-on-a-chip, and the reduction of thermal resistance associated with liquid metal cooling of microelectronics. At any given cross-section, the meniscus takes the approximate shape of a circular arc whose curvature is determined by the pressure difference across it. Hence, it typically protrudes into the grooves near the inlet of a microchannel and is gradually drawn into the microchannel as it is traversed and the liquid pressure decreases. For sufficiently large Reynolds numbers, the variation of the meniscus shape and hence the flow geometry necessitates the inclusion of inertial (non-parallel) flow effects. We capture them for a slender microchannel, where our small parameter is the ratio of ridge pitch-to-microchannel height, and order-one Reynolds numbers. This is done by using a hybrid analytical–numerical method to resolve the nonlinear three-dimensional (3-D) problem as a sequence of two-dimensional (2-D) linear ones in the microchannel cross-section, allied with non-local conditions that determine the slowly varying pressure distribution at leading and first orders. When the pressure difference across the microchannel is constrained by the advancing contact angle of the liquid on the ridges and its surface tension (which is high for liquid metals), inertial effects can significantly reduce the flow rate for realistic parameter values. For example, when the solid fraction of the ridges is 0.1, the microchannel height-to-(half) ridge pitch ratio is 6, the Reynolds number of the flow is 1 and the small parameter is 0.1, they reduce the flow rate of a liquid metal (Galinstan) by approximately 50 %. Conversely, for sufficiently large microchannel heights, they enhance it. Physical explanations of both of these phenomena are given.

The Calculation of the Quasi-Three-Dimensional Flow in an Axial Gas Turbine

1975 ◽  
Vol 97 (2) ◽  
pp. 283-294 ◽  
Author(s):  
S. Biniaris
Keyword(s):  
Numerical Solution ◽  
Cross Section ◽  
Three Dimensional ◽  
Entire Region ◽  
Three Dimensional Flow ◽  
Total Enthalpy ◽  
Blade Thickness ◽  
Meridional Cross Section ◽  
The Finite Difference Method ◽  
The Stability

The flow is calculated within the entire region from far upstream to far downstream of the blade rows and this not only between the blade rows but especially within the blade passages. It is assumed that the flow is steady, adiabatic, and inviscid. However, compressibility, blade forces in all directions, blade thickness, and total enthalpy gradients are taken into account. The shape of the meridional cross section can be arbitrary. The blades can be either cylindrical or twisted. The numerical solution is based on the finite-difference method. The discretization error, the stability error, and the iteration error of the numerical solution are determined.

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