New Design Method for Spiral Casings Considering the Properties of the Impeller and Spiral Casing at Design and Off-Design Conditions and Numerical Verification With CFD

2018 ◽  
Author(s):  
Philipp Epple ◽  
Manuel Fritsche ◽  
Michael Steppert ◽  
Michael Steber
Keyword(s):  
Design Process ◽  
Flow Rate ◽  
Velocity Component ◽  
Tangential Velocity ◽  
Sectional Area ◽  
Cross Sectional ◽  
Flow Rates ◽  
Tangential Velocity Component ◽  
Design Point ◽  
Spiral Casing

Radial fans for industrial applications are very commonly operated with a spiral casing, also called volute. The function of the volute is to collect the air from the impellers outlet and to transport it to the fans outlet. In the volute the tangential velocity component of the impeller is transformed in a straight velocity component at the volute’s outlet. In the volute the static pressure is increased according to the cross sectional area of the volute. When the flow exits the impeller the flow rate is given basically by the radial velocity component times the outlet area of the impeller. In the volute, however, the flow rate is basically given by the tangential velocity component at the impeller exit and in the volute considering the conservation of angular momentum. Hence, there is only one operating point, i.e. the design point of the volute, where the flow rate in the impeller matches the flow rate in the volute. In the literature the design of the volute is performed at the design point only and the cross sectional area of the volute is usually computed distributing the flow rate linearly from the tongue to the exit of the volute. In this work an extended theoretical approach was developed considering the design point flow rate and off design flow rates. At the design point, the properties of the specific impeller, i.e. it’s radial and its tangential velocity components at the impeller’s exit are considered to design the volute. Furthermore, also the off-design characteristics of the impeller, i.e. its radial and tangential velocity components are considered in the design process of the volute. The flow rates in the impeller and in the volute match only at the design point, at off-design points the flow rates in the impeller and in the volute are different. This has an important impact on the design process of impeller – volute units. Each volute has also to be matched to the specific impeller. In the numerical part a usual volute was designed considering the properties of a particular impeller. The performance of the volute and of complete fan was investigated with the commercial Navier–Stokes Solver ANSYS CFX. A detailed analysis of the results and the flow conditions in volute as well as in the impeller-volute unit and a comparison with the results predicted by the new volute theory is given.

Maximal Expiratory Flow and Lung Volume Changes Associated with Exercise-Induced Asthma in Children and the Effect of Breathing a Low-Density Gas Mixture

1974 ◽  
Vol 46 (3) ◽  
pp. 317-329 ◽  
Author(s):  
S. R. Benatar ◽  
P. König
Keyword(s):  
Flow Rate ◽  
Vital Capacity ◽  
Forced Expiratory Volume ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Lung Volumes ◽  
Flow Rates ◽  
Before And After ◽  
Expiratory Flow

1. Lung volumes and maximum expiratory flow volume (MEFV) curves were measured before and after exercise and after a bronchodilator in eight asthmatic children. 2. Exercise produced significant changes in all volumes and flow rates measured, but the most sensitive measurement was of flow rate at an absolute volume in the terminal portion of the forced vital capacity. Of the more simply obtained measurements maximal flow at 50% of the exhaled vital capacity was the most sensitive, but reductions in forced expiratory volume at 1 s and peak flow rate were almost as marked. 3. The marked reductions in flow rates at low lung volumes after exercise were accompanied by large increases in residual volume and a reduction in the slope of the MEFV curve. These changes suggest functional closure of some lung units and an increase in the time-constant of emptying of other units. 4. The response of flow to breathing helium—oxygen (79:21, v/v) was assessed in the dilated state (before exercise or after bronchodilator) and the constricted state (after exercise) in five of the subjects. 5. An increase in density-dependence of flow rates at all lung volumes during constriction is evidence that, despite the reduction in flow rates, convective acceleration and turbulent flow constitute a greater proportion of the total upstream resistance after exercise than before exercise. The implication is that the cross-sectional area at equal pressure points (EPP) is smaller after exercise than before exercise. This could result from either bronchoconstriction with no change in the location of EPP, or from progression of the EPP further upstream to a region where loss of airways or reduction in their diameter has rendered the total cross-sectional area considerably smaller than under normal circumstances.

A New Method for Performance Measurement of PPV Fans for Fire Fighting Under Realistic Conditions

2020 ◽  
Author(s):  
Michael Steppert ◽  
Philipp Epple ◽  
Michael Steber ◽  
Stefan Gast
Keyword(s):  
Design Process ◽  
Flow Rate ◽  
Volumetric Flow Rate ◽  
Navier Stokes ◽  
Analytical Relation ◽  
Positive Pressure ◽  
Flow Rates ◽  
Free Jet ◽  
Actual Flow Rate ◽  
Coefficient Of Discharge

Abstract PPV Fans (Positive Pressure Ventilation Fans) are used in firefighting to remove smoke from a burning building, so that fire fighters can have a clear view inside the house and injured people do not have to breathe toxic smoke. This can be done by placing a PPV fan in a distance of about two meters in front of a door of the burning building. On another, carefully chosen position in the building, e. g. a window, a door or at the roof an opening has to be created, where the smoke can leave the building. The same volumetric flow rate of gas that is blown into the building by the PPV fan has to leave the building at a chosen opening. Because the gas entering the building is air and the gas leaving the building is a mixture of smoke and air, the smoke concentration in the building can be reduced. To test the performance of such PPV fans, a test building with a door in the first floor and a window in the 3rd floor has been built. To measure the volumetric flow rate of the smoke and air mixture through the window in the 3rd floor that is leaving the building, a flow meter nozzle was designed. The design process was done using the commercial Navier Stokes solver Star CCM+, where three nozzle designs, such as a nozzle with constant velocity increase, a quarter circle nozzle and a non-curved nozzle were investigated for different volumetric flow rates. Also, a rounding at the window, where the nozzle is placed, was investigated to prevent flow detachment and shock losses at the inlet of the nozzle. The volumetric flow rate through the nozzle can be calculated, by measuring the pressure at the nozzle wall (before the contraction) and applying Bernoulli’s law, the continuity equation and assuming atmospheric pressure at the free jet flow at the end of the nozzle. The so calculated volumetric flow rate was compared with the actual flow rate, given by the numerical CFD simulations. With these values, the nozzle specific coefficient of discharge for several volumetric flow rates has been calculated and a function fitting was done to get obtain analytical relation between pressure and volumetric flow rate. The detailed design process of the three nozzles, the numerical results of the CFD studies and the determination of the nozzle specific coefficients of discharge are shown and discussed in detail in this work.

scholarly journals The Influence of Flow Rate on the Wake in a Centrifugal Impeller

1982 ◽  
Author(s):  
M. W. Johnson ◽  
J. Moore
Keyword(s):  
Flow Rate ◽  
Incidence Angle ◽  
Three Dimensional ◽  
Stagnation Pressure ◽  
Centrifugal Impeller ◽  
Suction Surface ◽  
Cross Sectional ◽  
Flow Rates ◽  
Pressure Losses ◽  
Compressor Impeller

Three-dimensional flows and their influence on the stagnation pressure losses in a centrifugal compressor impeller have been studied. All 3 mutally perpendicular components of relative velocity and stagnation pressure on 5 cross-sectional planes, between the inlet and outlet of a 1 m dia shrouded impeller running at 500 rpm were measured. Comparisons were made between results for a flow rate corresponding to nearly zero incidence angle and two other flows, with increased and reduced flow rates. These detailed measurements show how the position of separation of the shroud boundary layer moved downstream and the wake’s size decreased, as the flow rate was increased. The wake’s location, at the outlet of the impeller, was also observed to move from the suction surface at the lowest flow rate, to the shroud at higher flow rates.

Accuracy and precision of MR velocity mapping in measurement of stenotic cross-sectional area, flow rate, and pressure gradient

1993 ◽  
Vol 3 (2) ◽  
pp. 433-437 ◽  
Author(s):  
Lars Søndergaard ◽  
Freddy Ståhlberg ◽  
Carsten Thomsen ◽  
Anders Stensgaard ◽  
Knud Lindvig ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Flow Rate ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Velocity Mapping ◽  
Cross Sectional ◽  
Accuracy And Precision

Investigation of Cross-Sectional Velocity Field Near the Inducer Plane of a Turbocharger Compressor Using 2D Particle Image Velocimetry

2019 ◽  
Author(s):  
Deb Banerjee ◽  
Rick Dehner ◽  
Ahmet Selamet ◽  
Keith Miazgowicz ◽  
Todd Brewer ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Velocity Field ◽  
Flow Field ◽  
Mass Flow ◽  
Particle Image ◽  
Tangential Velocity ◽  
Cross Sectional ◽  
Flow Rates ◽  
Blade Passage ◽  
Image Velocimetry

Abstract Understanding the velocity field at the inlet of an automotive turbocharger is critical in order to suppress the instabilities encountered by the compressor, extend its map and improve the impeller design. In the present study, two-dimensional particle image velocimetry experiments are carried out on a turbocharger compressor without any recirculating channel to investigate the planar flow structures on a cross-sectional plane right in front of the inducer at a rotational speed of 80 krpm. The objective of the study is to investigate the flow field in front of a compressor blade passage and quantify the velocity distributions along the blade span for different mass flow rates ranging from choke (77 g/s) to deep surge (13.6 g/s). It is observed that the flow field does not change substantially from choke to about 55 g/s, where flow reversal is known to start at this speed from earlier measurements. While the tangential velocity is less than 8 m/s, the radial velocity increases along the span to 17–20 m/s near the tip at high flow rates (55–77 g/s). As the mass flow rate is reduced below 55 g/s, the radial component starts decreasing and the tangential velocity increases rapidly. From about 5 m/s at 55 g/s, the tangential velocity at the blade tip exceeds 50 m/s at 50 g/s and reaches a maximum of about 135 m/s near surge. These time-averaged distributions are similar for different angular locations in front of the blade passage and do not exhibit any substantial azimuthal variation.

Turbulence measurements with inclined hot-wires Part 2. Hot-wire response equations

1967 ◽  
Vol 28 (1) ◽  
pp. 177-182 ◽  
Author(s):  
F. H. Champagne ◽  
C. A. Sleicher
Keyword(s):  
Velocity Component ◽  
Wire Array ◽  
Tangential Velocity ◽  
Constant Current ◽  
Hot Wire ◽  
Tangential Velocity Component ◽  
Low Intensity ◽  
Hot Wires ◽  
Current Operation ◽  
Cosine Law

Hot-wire response equations to include the effects of the tangential velocity component as well as the non-linearities caused by high intensity turbulence are derived for linearized constant temperature operation. For low intensity turbulence similar equations are derived for constant current operation. The equations are applied to an X-wire array to determine the errors in selected turbulence quantities which arise from the assumption of cosine law cooling. The error depends upon the quantity measured, the method of operation, and [lscr ]/d. For [lscr ]/d = 200 the error ranges from 0 to 17%.

scholarly journals Hydrology of a segment of a glacier situated in an overdeepening, Storglaciären, Sweden

1994 ◽  
Vol 40 (134) ◽  
pp. 140-148 ◽  
Author(s):  
Roger Leb. Hooke ◽  
Veijo A. Pohjola
Keyword(s):  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Flow Rates ◽  
Video Observations ◽  
Pressure Melting ◽  
Bed Slope ◽  
Energy Dissipated ◽  
Total Discharge ◽  
Tracer Experiments

AbstractTracer experiments, and water-level observations made while drilling 47 boreholes in an overdeepened section of Storglaciären, have demonstrated that nearly all of the water passing through this part of the glacier moves in englacial conduits. Much of the viscous energy dissipated by subglacial water flowing up an adverse bed slope out of such an overdeepening may be needed to warm the water to keep it at the pressure-melting point. If the adverse slope is sufficiently steep, freezing may occur within the conduits. The possibility for enlargement of conduits by melting is thus limited and water pressures become high. We infer that this, combined with possible blocking of conduits by freezing, forces the water to seek englacial pathways.The frequency with which englacial conduits are encountered during drilling suggests that there are several hundred of them in any given cross-section of the glacier. Consequently, each must carry a small fraction of the total discharge, say ∼ 10−3 m3 s−1. Tracer experiments suggest that flow rates in these conduits are < 10− m s−1, so conduit cross-sectional areas must be ∼10−2 m2, a size that is consistent with video observations in boreholes. The observed mean hydraulic gradient through the overdeepening is ∼0.04. If the conduits were of uniform cross-sectional area, the roughness implied by these figures would be unreasonably high and water pressures in them would be lower than observed. Thus, we hypothesize that conduits are locally constricted to only a small fraction of their average cross-sectional area.

scholarly journals EFFECT OF OPERATING PARAMETERS UPON PERFORMANCE OF FUNCTIONAL SPECIMENS OF HIGH EXPANSION FOAM GENERATORS

2020 ◽  
Vol 1 (2) ◽  
pp. 14-21
Author(s):  
V Chuian ◽  
O Тymoshenko ◽  
A Hrachov
Keyword(s):  
Flow Rate ◽  
Cross Sectional Area ◽  
Solution Flow Rate ◽  
Operating Parameters ◽  
Spray Nozzle ◽  
Sectional Area ◽  
Solution Flow ◽  
Cross Sectional ◽  
Foam Expansion ◽  
Expansion Foam

The issues related to application of high expansion foam as flooding fire extinguishing agent as well as necessity of the development of high expansion foam generators in Ukraine are considered. Patent search concerning appropriate devices for generation of high expansion foam from foam solutions was conducted and it showed specific features of the components when generating high expansion foam. The results of the research of operating parameters of prototypes of high expansion foam generators of fan and ejection types are presented. For high expansion foam generators of fan type dependence of foam expansion, foam solution flow rate and amount of spent foam solution on the performance of the spray nozzle at different pressures and ratio of fan performance to the spray nozzle performance was established; the ratio of the cross-sectional area of the fan to the total area of the perforated holes in the foaming grid was studied, too. For high-expansion foam generators of the ejection type dependence of foam expansion, foam solution flow rate and amount of spent foam solution on the capacity of the spray nozzle unit at different pressures, foam solution flow rate to the total area of the holes in the foaming grid, and ratio of the cross-sectional area of the generator to the total area of the perforated holes of the foaming grid were studied. Functional models of the mentioned types of generators (both ejection (aspiration) one and generator equipped with fan (air blowing unit)) were developed, created and tested for the purpose of derivation of appropriate relations between their conditions of use and performance. At the same time, high expansion foam generators of fan type by their weight and size parameters are intended for use in the divisions of the Operative and Rescue Service of Civil Protection of the State Emergency Service of Ukraine as portable firefighting units. Such firefighting units are intended to be installed first of all on any state-of-the-art municipal fire engines equipped with autonomous AC generators. High expansion foam generators of ejection type are intended for use as firefighting units in foam firefighting systems of various facilities with fire hazard.

scholarly journals Analysis of Liquid Flow and Mixing in an Oscillatory Flow Reactor Provided with 2D Smooth Periodic Constrictions

2018 ◽  
Vol 4 (2) ◽  
pp. 1-15 ◽  
Author(s):  
F. Almeida ◽  
F. Rocha ◽  
A. Ferreira
Keyword(s):  
Flow Rate ◽  
Oscillatory Flow ◽  
Flow Reactor ◽  
Cross Sectional Area ◽  
Axial Dispersion ◽  
Mixing Efficiency ◽  
Sectional Area ◽  
Cross Sectional ◽  
Liquid Dispersion ◽  
Fluid Oscillation

In this research paper the residence time distribution (RTD) was monitored for a range of fluid oscillation, frequency, amplitude and flow rate in two oscillatory flow reactors (OFR) provided with 2D smooth periodic constrictions (2D-SPC) with different designs. It was studied the axial liquid dispersion using axial dispersion model and the mixing efficiency using tank-in-series model for continuous mode. Two cases, with and without fluid oscillation, were studied and determined the optimum conditions to ensure a close plug flow, an efficient mixing and a low axial liquid dispersion. The optimum operation conditions for the two 2D-SPC designs were found. Moreover, the effect of open cross-sectional area (a) on mixing and axial dispersion was also investigated. For low cross-sectional area values the mixing is higher. It was observed that fluid oscillation increases the mixing intensity even at lower flow rates, and the axial dispersion increases as the flow rate increases.

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