A Theoretical Study of Ingress for Shrouded Rotating Disk Systems With Radial Outflow

1991 ◽  
Vol 113 (1) ◽  
pp. 91-97 ◽  
Author(s):  
J. W. Chew
Keyword(s):  
Mathematical Model ◽  
Simple Model ◽  
Reasonable Agreement ◽  
Theoretical Study ◽  
Rotating Disk ◽  
Empirical Constant ◽  
Integral Methods ◽  
Momentum Integral ◽  
Radial Outflow ◽  
Good Agreement

Sealing of the cavity formed between a stationary disk and a rotating disk under axisymmetric conditions is considered. A mathematical model of the flow in the cavity based on momentum integral methods is described and this is coupled to a simple model of the seal for the case when no ingress occurs. Predictions of the minimum imposed flow required to prevent ingress are obtained and shown to be in reasonable agreement with the data of Bayley and Owen (1970), Owen and Phadke (1980), Phadke (1982), and Phadke and Owen (1983a, 1983b, 1988). With an empirical constant in the model chosen to match these data, predictions for the minimum sealing flow are shown to be in good agreement with the measurements of Graber et al. (1987). The analysis of Phadke’s data also indicates the measurements for small seal clearances must be viewed with caution due to errors in setting the seal clearance. These errors are estimated to be twice the minimum clearance considered. Seal behavior when ingress occurs is also considered and estimates of the amount of ingress are made from the available data.

scholarly journals A Theoretical Study of Ingress for Shrouded Rotating Disc Systems With Radial Outflow

1989 ◽  
Author(s):  
John W. Chew
Keyword(s):  
Mathematical Model ◽  
Reasonable Agreement ◽  
Theoretical Study ◽  
Rotating Disc ◽  
Empirical Constant ◽  
Integral Methods ◽  
Stationary Disc ◽  
Momentum Integral ◽  
Radial Outflow ◽  
Good Agreement

Sealing of the cavity formed between a stationary disc and a rotating disc under axisymmetric conditions is considered. A mathematical model of the flow in the cavity based on momentum integral methods is described and this is coupled to a simple model of the seal for the case when no ingress occurs. Predictions of the minimum imposed flow required to prevent ingress are obtained and shown to be in reasonable agreement with the data of Bayley and Owen (1970), Owen and Phadke (1982), Phadke (1982), and Phadke and Owen (1982, 1983, 1988). With an empirical constant in the model chosen to match this data predictions for the minimum sealing flow are shown to be in good agreement with Graber et al’s (1987) measurements. The analysis of Phadke’s data also indicates the measurements for small seal clearances must be viewed with caution due to errors in setting the seal clearance. These errors are estimated to be twice the minimum clearance considered. Seal behaviour when ingress occurs is also considered and estimates of the amount of ingress are made from the available data.

Transitional flow between contra-rotating disks

1994 ◽  
Vol 281 ◽  
pp. 119-135 ◽  
Author(s):  
M. Kilic ◽  
X. Gan ◽  
J. M. Owen
Keyword(s):  
Boundary Layers ◽  
Cell Structure ◽  
Rotating Disk ◽  
Transitional Flow ◽  
Free Shear Layer ◽  
Rotating Disks ◽  
Double Transition ◽  
Type Flow ◽  
Radial Outflow ◽  
Good Agreement

This paper describes a combined computational and experimental study of the flow between contra-rotating disks for – 1 ≤ Γ ≤ 0 and Reϕ = 105, where Γ is the ratio of the speed of the slower disk to that of the faster one and Reϕ is the rotational Reynolds number of the faster disk. For Γ = 0, the rotor-stator case, laminar and turbulent computations and experimental measurements show that laminar Batchelor-type flow occurs: there is radial outflow in a boundary layer on the rotating disk, inflow on the stationary disk and a rotating core of fluid between. For Γ = – 1, the laminar computations produce Batchelor-type flow: there is radial outflow on both disks and inflow in a free shear layer in the mid-plane, on either side of which is a rotating core of fluid. The turbulent computations and the velocity measurements for Γ = – 1 show Stewartson-type flow: radial outflow occurs in laminar boundary layers on the disks and inflow occurs in a non-rotating turbulent core between the boundary layers. For intermediate values of Γ, transition from Batchelor-type flow to Stewartson-type flow is associated with a two-cell structure, the two-cells being separated by a streamline that stagnates on the slower disk; Batchelor-type flow occurs radially outward of the stagnation point and Stewartson-type flow radially inward. The turbulent computations are mainly in good agreement with the measured velocities for Γ = 0 and Γ = – 1, where either Batchelor-type flow or Stewartson-type flow occurs; there is less good agreement at intermediate values of Γ, particularly for Γ = – 0.4 where the double transition of Batchelor-type flow to Stewartson-type flow and laminar to turbulent flow occurs in the two-cell structure.

scholarly journals A Momentum Integral Method to Predict the Frictional Torque of a Rotating Disk With Protruding Bolts

1998 ◽  
Author(s):  
W. Gärtner
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Integral Equations ◽  
Critical Review ◽  
Integral Method ◽  
Rotating Disk ◽  
Frictional Torque ◽  
Momentum Integral ◽  
Good Agreement

A momentum integral method was developed to predict the frictional torque of a disk rotating in quiescent air with cylindrical protrusions mounted on its surface. The predicted torque is compared to experimental data taken for the protrusions placed on two different radii on the disk with two different numbers of protrusions on each radius. A critical review of the calculated results reveals that caused by the protrusions the predicted thickness of the boundary layer on the disk is of the same magnitude as the radius of the disk. Since in this case Prandtl’s simplifications for the boundary layer on which the momentum integral equations are based upon are not valid their use appears to be doubtful. However, the predicted frictional torque is in good agreement with the measurements for all configurations tested except for that with the smallest circumferential distance between the protrusions where the torque is overpredicted by the method. The application of the method for a disk rotating in a stationary housing is briefly discussed.

A Combined Experimental and Theoretical Study of Flow and Pressure Distributions in a Brush Seal

1993 ◽  
Vol 115 (2) ◽  
pp. 404-410 ◽  
Author(s):  
F. J. Bayley ◽  
C. A. Long
Keyword(s):  
Experimental Data ◽  
Reasonable Agreement ◽  
Theoretical Study ◽  
Isothermal Flow ◽  
Empirical Constant ◽  
Pressure Distributions ◽  
Brush Seal ◽  
Mass Flows ◽  
Porosity Measurements ◽  
Experimental Rig

A relatively simple theory is presented that can be used to model the flow and pressure distribution in a brush seal matrix. The model assumes laminar, compressible, isothermal flow and requires knowledge of an empirical constant: the seal porosity value. Measurements of the mass flow rate together with radial and axial distributions of pressure were taken on a nonrotating experimental rig. These were obtained using a 122 mm bore brush seal with 0.25 mm radial interference. The experimental data are used to estimate the seal porosity. Measurements of the pressure distributions along the backing ring and under the bristle tips and discussed. Predicted mass flows are compared with those actually measured and there is reasonable agreement considering the limitations of the model.

Numerical Predictions for the Flow Induced by an Enclosed Rotating Disc

1988 ◽  
Author(s):  
John W. Chew ◽  
Craig M. Vaughan
Keyword(s):  
Experimental Data ◽  
Reasonable Agreement ◽  
Mixing Length ◽  
Mean Flow ◽  
Rotating Disc ◽  
Numerical Predictions ◽  
Stationary Disc ◽  
The Mean ◽  
Radial Outflow ◽  
Good Agreement

Finite difference solutions are presented for turbulent flow in the cavity formed between a rotating and a stationary disc, with and without a net radial outflow of fluid. The mean flow is assumed steady and axisymmetric and a mixing length model of turbulence is used. Grid dependency of the solutions is shown to be acceptably small and results are compared with other workers’ experimental data. Theoretical and measured disc moment coefficients are in good agreement, while theoretical and measured velocities are in reasonable agreement. It is concluded that the mixing-length model is sufficiently accurate for many engineering calculations of boundary layer dominated flows in rotating disc systems.

Modelling of Drift Mobility Experiments on a-Si:H

1999 ◽  
Vol 557 ◽  
Author(s):  
Wen Chao Chen ◽  
Louis-André Hamel ◽  
Mathieu Kemp ◽  
Arthur Yelon
Keyword(s):  
Monte Carlo ◽  
Simple Model ◽  
Reasonable Agreement ◽  
Drift Mobility ◽  
Low Field ◽  
Comparison With Experiment ◽  
Multiple Trapping ◽  
Apparent Inconsistency ◽  
High Fields ◽  
Good Agreement

AbstractWe present recent results of a study of the behavior of electronic carriers in a-Si:H, using the model of multiple trapping (MT) in an exponential density of states. In previous publications, using Monte Carlo simulations, we showed that the standard low field MT model gives reasonable agreement with experiment particularly if the Meyer-Neldel effect is included in the model. We report here on the results of including two other effects. First, we have included a simple model of field assisted detrapping, to take account of the effect of high fields. We obtain very good agreement with the results of measurements on both electrons and holes, from a number of laboratories. In addition, we show here that the validity of an effective temperature approach can be checked easily by comparison with experiment. Second, we have presented a simple model of rapid relaxation of trapped carriers. This model offers the possibility of removing the apparent inconsistency between these measurements, and other experiments.

scholarly journals A Combined Experimental and Theoretical Study of Flow and Pressure Distributions in a Brush Seal

1992 ◽  
Author(s):  
F. J. Bayley ◽  
C. A. Long
Keyword(s):  
Reasonable Agreement ◽  
Theoretical Study ◽  
Isothermal Flow ◽  
Empirical Constant ◽  
Pressure Distributions ◽  
Brush Seal ◽  
Mass Flowrate ◽  
Mass Flows ◽  
Porosity Measurements ◽  
Experimental Rig

A relatively simple theory is presented which can be used to model the flow and pressure distributions in a brush seal matrix. The model assumes laminar, compressible, isothermal flow and requires knowledge of an empirical constant: the seal porosity value. Measurements of the mass flowrate together with radial and axial distributions of pressure were taken on a non-rotating experimental rig. These were obtained using a 122 mm bore brush seal with 0.25 mm radial interference. The experimental data are used to estimate the seal porosity. Measurements of the pressure distributions along the backing ring and under the bristle tips are discussed. Predicted mass flows are compared with those actually measured and there is reasonable agreement considering the limitations of the model.

The Use of Fins to Reduce the Pressure Drop in a Rotating Cavity With a Radial Inflow

1989 ◽  
Vol 111 (3) ◽  
pp. 349-356 ◽  
Author(s):  
J. W. Chew ◽  
P. R. Farthing ◽  
J. M. Owen ◽  
B. Stratford
Keyword(s):  
Pressure Drop ◽  
Reasonable Agreement ◽  
Numerical Solutions ◽  
Disk Model ◽  
Linear Solution ◽  
Integral Methods ◽  
Rotating Cavity ◽  
Momentum Integral ◽  
The Mathematical Model ◽  
Plane Disk

A combined theoretical and experimental study of radial inflow through a rotating cavity is reported. It is shown that radial fins attached to one of the disks are effective in reducing the pressure drop across the cavity. The mathematical model, is an extension of earlier plane-disk momentum-integral methods; the fins are treated as rectangular rib elements and a rough-disk model is derived. Numerical solutions of the integral equations are given. An approximate linear solution is also derived. Experiments were conducted when both disks were plane and when one of the disks was fitted with 60 radial fins. Flow visualization revealed the flow structure in the cavity and confirmed some of the assumptions used in the theoretical model. Measurements and predictions of the pressure drop across the cavity were in reasonable agreement.

Explanation of the Influence of Inflow Air Content on the Lift of Cavitating Hydrofoils

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Eduard Amromin
Keyword(s):  
Experimental Data ◽  
Theoretical Study ◽  
Lift Coefficient ◽  
Cavity Surface ◽  
Air Bubbles ◽  
Incoming Flow ◽  
Fluid Density ◽  
Air Content ◽  
Theoretical Results ◽  
Good Agreement

According to several known experiments, an increase of the incoming flow air content can increase the hydrofoil lift coefficient. The presented theoretical study shows that such increase is associated with the decrease of the fluid density at the cavity surface. This decrease is caused by entrainment of air bubbles to the cavity from the surrounding flow. The theoretical results based on such explanation are in a good agreement with the earlier published experimental data for NACA0015.

Optical Vibration and Acceleration Sensor With a Silicon Cantilever

1999 ◽  
Author(s):  
Mitsuteru Kimura ◽  
Katsuhisa Toshima ◽  
Harunobu Satoh
Keyword(s):  
Simple Model ◽  
Optical Fiber ◽  
Resonance Frequency ◽  
Acceleration Sensor ◽  
Frequency Range ◽  
Silicon Cantilever ◽  
All Optical ◽  
New Type ◽  
Good Agreement ◽  
Optical Vibration

Abstract A new type all optical vibration and acceleration sensor using the combination of micromachined Si cantilever and optical fiber is proposed, and its fundamental characteristics are demonstrated. The light emitted from bulb-lens set into the V-groove is reflected at the reflector formed on the Si cantilever and then recoupled into the bulb-lens. Several sensors with different length (0.64–6.0 mm long) of the Si cantilever are fabricated to compare the theoretical resonance frequency fr obtained from the simple model and experimental ones. They had good agreement. From the sensing principle the sensing frequency range of the vibration is suitable below the fr of the Si cantilever of the sensor.

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