Statistical and Theoretical Models of Ingestion Through Turbine Rim Seals

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Kunyuan Zhou ◽  
Simon N. Wood ◽  
J. Michael Owen
Keyword(s):  
Experimental Data ◽  
Statistical Model ◽  
Flow Parameter ◽  
Likelihood Estimation ◽  
Theoretical Models ◽  
Operating Conditions ◽  
Data Points ◽  
Effects Of Rotation ◽  
Effectiveness Data ◽  
Good Agreement

In recent papers, orifice models have been developed to calculate the amount of ingestion, or ingress, that occurs through gas-turbine rim seals. These theoretical models can be used for externally induced (EI) ingress, where the pressure differences in the main gas path are dominant, and for rotationally induced (RI) ingress, where the effects of rotation in the wheel space are dominant. Explicit “effectiveness equations,” derived from the orifice models, are used to express the flow rate of sealing air in terms of the sealing effectiveness. These equations contain two unknown terms: Φmin, a sealing flow parameter, and Γc, the ratio of the discharge coefficients for ingress and egress. The two unknowns can be determined from concentration measurements in experimental rigs. In this paper, maximum likelihood estimation is used to fit the effectiveness equations to experimental data and to determine the optimum values of Φmin and Γc. The statistical model is validated numerically using noisy data generated from the effectiveness equations, and the simulated tests show the dangers of drawing conclusions from sparse data points. Using the statistical model, good agreement between the theoretical curves and several sets of previously published effectiveness data is achieved for both EI and RI ingress. The statistical and theoretical models have also been used to analyze previously unpublished experimental data, the results of which are included in separate papers. It is the ultimate aim of this research to apply the effectiveness data obtained at rig conditions to engine-operating conditions.

Statistical and Theoretical Models of Ingestion Through Turbine Rim Seals

2011 ◽  
Author(s):  
Kunyuan Zhou ◽  
Simon N. Wood ◽  
J. Michael Owen
Keyword(s):  
Experimental Data ◽  
Statistical Model ◽  
Flow Parameter ◽  
Likelihood Estimation ◽  
Theoretical Models ◽  
Operating Conditions ◽  
Data Points ◽  
Effects Of Rotation ◽  
Effectiveness Data ◽  
Good Agreement

In recent papers, orifice models have been developed to calculate the amount of ingestion, or ingress, that occurs through gas-turbine rim seals. These theoretical models can be used for externally-induced (EI) ingress, where the pressure differences in the main gas path are dominant, and for rotationally-induced (RI) ingress, where the effects of rotation in the wheel-space are dominant. Explicit ‘effectiveness equations’, derived from the orifice models, are used to express the flow rate of sealing air in terms of the sealing effectiveness. These equations contain two unknown terms: Φmin, a sealing flow parameter, and Γc, the ratio of the discharge coefficients for ingress and egress. The two unknowns can be determined from concentration measurements in experimental rigs. In this paper, maximum likelihood estimation is used to fit the effectiveness equations to experimental data and to determine the optimum values of Φmin and Γc. The statistical model is validated numerically using noisy data generated from the effectiveness equations, and the simulated tests show the dangers of drawing conclusions from sparse data points. Using the statistical model, good agreement between the theoretical curves and several sets of previously-published effectiveness data is achieved for both EI and RI ingress. The statistical and theoretical models have also been used to analyse previously-unpublished experimental data, the results of which are included in separate papers. It is the ultimate aim of this research to apply the effectiveness data obtained at rig conditions to engine-operating conditions.

Modeling and Experimental Validation of the Effective Bulk Modulus of a Mixture of Hydraulic Oil and Air

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Hossein Gholizadeh ◽  
Doug Bitner ◽  
Richard Burton ◽  
Greg Schoenau
Keyword(s):  
Experimental Data ◽  
Bulk Modulus ◽  
Theoretical Models ◽  
Operating Conditions ◽  
Air Bubbles ◽  
Pressure Sensitivity ◽  
Hydraulic Oil ◽  
Effective Bulk Modulus ◽  
Experimental Apparatus ◽  
Major Factors

It is well known that the presence of entrained air bubbles in hydraulic oil can significantly reduce the effective bulk modulus of hydraulic oil. The effective bulk modulus of a mixture of oil and air as pressure changes is considerably different than when the oil and air are not mixed. Theoretical models have been proposed in the literature to simulate the pressure sensitivity of the effective bulk modulus of this mixture. However, limited amounts of experimental data are available to prove the validity of the models under various operating conditions. The major factors that affect pressure sensitivity of the effective bulk modulus of the mixture are the amount of air bubbles, their size and the distribution, and rate of compression of the mixture. An experimental apparatus was designed to investigate the effect of these variables on the effective bulk modulus of the mixture. The experimental results were compared with existing theoretical models, and it was found that the theoretical models only matched the experimental data under specific conditions. The purpose of this paper is to specify the conditions in which the current theoretical models can be used to represent the real behavior of the pressure sensitivity of the effective bulk modulus of the mixture. Additionally, a new theoretical model is proposed for situations where the current models fail to truly represent the experimental data.

Numerical Analysis of the Flow Inside a Centrifugal Compressor’s Vaneless Diffuser and Volute

2001 ◽  
Author(s):  
Hooman Rezaei ◽  
Abraham Engeda ◽  
Paul Haley
Keyword(s):  
Experimental Data ◽  
Numerical Analysis ◽  
Mass Flow ◽  
Operating Conditions ◽  
Vaneless Diffuser ◽  
Flow Angle ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Minimum Medium ◽  
Good Agreement

Abstract The objective of this work was to perform numerical analysis of the flow inside a modified single stage CVHF 1280 Trane centrifugal compressor’s vaneless diffuser and volute. Gambit was utilized to read the casing geometry and generating the vaneless diffuser. An unstructured mesh was generated for the path from vaneless diffuser inlet to conic diffuser outlet. At the same time a meanline analysis was performed corresponding to speeds and mass flow rates of the experimental data in order to obtain the absolute velocity and flow angle leaving the impeller for those operating conditions. These values and experimental data were used as inlet and outlet boundary conditions for the simulations. Simulations were performed in Fluent 5.0 for three speeds of 2000, 3000 and 3497 RPM and mass flow rates of minimum, medium and maximum. Results are in good agreement with the experimental ones and present the flow structures inside the vaneless diffuser and volute.

Dual Role of Nanoparticles in the Thermal Conductivity Enhancement of Nanoparticle Suspensions

2005 ◽  
Author(s):  
Calvin H. Li ◽  
G. P. Peterson
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Brownian Motion ◽  
Theoretical Models ◽  
Conductivity Enhancement ◽  
Nanoparticle Suspensions ◽  
The Difference ◽  
Physical Phenomena ◽  
Good Agreement

Experimental evidence exists that the addition of a small quantity of nanoparticles to a base fluid, can have a significant impact on the effective thermal conductivity of the resulting suspension. The causes for this are currently thought to be due to a combination of two distinct mechanisms. The first is due to the change in the thermophysical properties of the suspension, resulting from the difference in the thermal conductivity of the fluid and the particles, and the second is thought to be due to the transport of thermal energy by the particles, due to the Brownian motion of the particles. In order to better understand these phenomena, a theoretical model has been developed that examines the effect of the Brownian motion. In this model, the well-known approach first presented by Maxwell, is combined with a new expression that incorporates the effect of the Brownian motion and describes the physical phenomena that occurs because of it. The results indicate that the enhanced thermal conductivity may not in fact be due to the transport of energy by the particles, but rather, due to the stirring motion caused by the movement of the nanoparticles which enhances the heat transfer within the fluid. The resulting model shows good agreement when compared with the existing experimental data and perhaps more importantly helps to explain the trends observed from a fundamental physical perspective. In addition, it provides a possible explanation for the differences that have been observed between the previously obtained experimental data, the predictions obtained from Maxwell’s equation and the theoretical models developed by other investigators.

Numerical Simulation and Experimental Study of Particle Dynamics in a Rotating Drum with Flights

2017 ◽  
Vol 899 ◽  
pp. 65-70 ◽  
Author(s):  
Suellen Mendonça Nascimento ◽  
F.P. de Lima ◽  
Claudio Roberto Duarte ◽  
Marcos Antonio de Souza Barrozo
Keyword(s):  
Experimental Data ◽  
Granular Flow ◽  
Numerical Study ◽  
Operating Conditions ◽  
Particle Dynamic ◽  
Multiphase Model ◽  
Theoretical Studies ◽  
Rotating Drum ◽  
Dynamics Of Particles ◽  
Good Agreement

Rotary dryers are widely used in various industries. Although numerous research efforts have focused on characterizing the dynamics of these equipments, the design of rotating dryers is complex, and theoretical studies are necessary to gain an in-depth understanding of the dynamics of particles in these dryers. This paper aims to investigate the particle dynamic behavior in a rotating drum with flights, based on CFD and experimental results. In the numerical study it was used the Eulerian-Eulerian multiphase model along with the kinetic theory of granular flow. The holdups of solids in the flights were compared with experimental data, using a methodology created specifically for this purpose. The simulated results were in good agreement with the experimental data and the present work has shown that the Eulerian approach has been able to predict the fluid dynamics behavior in different operating conditions.

Localized canting model for substituted ferrimagnets. I. Singly substituted YIG systems

1970 ◽  
Vol 48 (23) ◽  
pp. 2857-2867 ◽  
Author(s):  
A. Rosencwaig
Keyword(s):  
Experimental Data ◽  
Magnetic Properties ◽  
Statistical Model ◽  
Magnetic Moments ◽  
Exchange Parameter ◽  
New Model ◽  
Model Based ◽  
Curie Temperatures ◽  
Good Agreement

A statistical model based on the concept of localized canting, originally proposed by Geller and coworkers, is developed to account for the magnetic properties of substituted ferrimagnets. This model is used to determine the exchange parameter ratios Jdd/Jdd and Jaa/Jad in YIG systems by evaluating the magnetic moments and Curie temperatures of two classes of singly substituted YIG over the entire substitution range. Good agreement with experimental data is obtained with the physically reasonable exchange parameter ratios of [Formula: see text] and Jaa/Jad *~ 0.07. It is also shown that both the Yafet-Kittel and the Nowik models may be regarded as particular limiting cases of the new model.

Perturbed Flow Structure in an Annular Seal Due to Synchronous Whirl

1994 ◽  
Vol 116 (3) ◽  
pp. 564-569
Author(s):  
E. A. Baskharone
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Flow Field ◽  
Operating Conditions ◽  
Clearance Ratio ◽  
Perturbation Model ◽  
Eccentric Rotor ◽  
Annular Seal ◽  
The Common ◽  
Good Agreement

This paper provides a thorough examination of the flow field resulting from synchronous whirl of an eccentric rotor in an annular seal under typical operating conditions. A new finite-element-based perturbation model is employed in the analysis, whereby perturbations in the flow thermophysical properties are attributed to virtual distortions in the rotor-to-housing finite element assembly. The numerical results are compared to a recent set of experimental data for a hydraulic seal with typical geometrical configurations and a synchronously whirling rotor. Despite the common perception that perturbation analyses are categorically confined to small rotor eccentricities, good agreement between the computed flow field and the experimental data is obtained for an eccentricity/clearance ratio of 50 percent. The agreement between the two sets of data is notably better at axial locations where the real-rig flow admission losses have diminished, and up to the seal discharge station. This attests to the accuracy of this untraditional and highly versatile perturbation model in predicting the rotordynamic characteristics of this and a wide variety of conceptually similar fluid/rotor interaction problems.

The Vibroacoustic Behavior of a Rotating Annular Complex Plate With Application to the Design of Circular Saws

1995 ◽  
Author(s):  
Noureddine Atalla ◽  
André Côté ◽  
Benoît Cournoyer ◽  
Jean Nicolas
Keyword(s):  
Experimental Data ◽  
Noise Reduction ◽  
Variational Approach ◽  
Annular Plate ◽  
Theoretical Models ◽  
Viscoelastic Damping ◽  
Circular Saw ◽  
Constrained Damping ◽  
Effects Of Rotation ◽  
Circular Saws

Abstract This paper discusses the vibroacoustic behavior of an annular rotating complex plate with application to the design of circular saws. The effects of rotation and constrained viscoelastic damping are investigated both theoretically and experimentally. On the theoretical front, a model based on the variational approach has been developed. Special attention has been devoted to 1) the effects of rotation on both the vibration and the noise radiated by the annular plate and 2) the optimization of viscoelastic constrained damping. On the experimental front, several set ups have been devised to validate the theoretical models and to test some noise reduction avenues. Examples showing predictions from the theoretical models will be presented together with comparisons to experimental data. Finally, application of the above results to the design of a quieter circular saw will be discussed.

Applications of Wavelet Neural Network for Prediction of CHF

2011 ◽  
Vol 58-60 ◽  
pp. 1282-1286
Author(s):  
Hui Ming Wei ◽  
Yuan Tian ◽  
Jun Zhong ◽  
Xuan Zhang
Keyword(s):  
Neural Network ◽  
Experimental Data ◽  
Heat Flux ◽  
Linear Problem ◽  
Wavelet Neural Network ◽  
Data Simulation ◽  
Data Points ◽  
Set Up ◽  
Parameter Ranges ◽  
Good Agreement

In this study, a wavelet neural network (WNN) model for predicting critical heat flux (CHF) is set up. The WNN mode combining the properties of the wavelet transform and the advantages of Artificial Neural Networks (ANN) has some advantages of its globe optimal searching, quick convergence speed and solving non-linear problem. The database used in the analysis is from the 1960’s, including 126 data points which cover these parameter ranges: pressure P=100–1,000 kPa, mass flow rate G=40–500 kgm-2s-1, inlet subcooling ΔTsub=0–35◦C and heat flux Q=20–8,000 kWm-2. The WNN prediction results have a good agreement with experimental data. Simulation and analysis results show that the network model can effectively predict CHF.

Review of Thermal Joint Resistance Models for Non-Conforming Rough Surfaces in a Vacuum

2003 ◽  
Author(s):  
M. Bahrami ◽  
J. R. Culham ◽  
M. M. Yovanovich ◽  
G. E. Schneider
Keyword(s):  
Experimental Data ◽  
Thermal Analysis ◽  
Flux Tube ◽  
Thermal Contact ◽  
Theoretical Models ◽  
Size Number ◽  
Data Points ◽  
Contact Models ◽  
The Mean ◽  
Contact Parameters

The thermal contact resistance (TCR) problem is categorized into three different problems: geometrical, mechanical, and thermal. Each problem includes a macro and micro scale sub-problem; existing theories and models for each part are reviewed. Empirical correlations for microhardness, and the equivalent (sum) rough surface approximation are discussed. Suggested correlations for estimating the mean absolute surface slope are summarized and compared with experimental data. The classical conforming rough contact models, i.e elastic and plastic, as well as elastoplastic models are reviewed. A set of scale (dimensionless) relationships are derived for the contact parameters, i.e. the mean microcontact size, number of micro-contacts, density of microcontacts, and the external load as functions of dimensionless separation, for the above models. These scale relationships are plotted; it is graphically shown that the behavior of these models, in terms of the contact parameters, are similar. The most common assumptions of existing thermal analysis are summarized. As basic elements of thermal analysis, spreading resistance of a circular heat source on a half-space and flux tube are reviewed, also existing flux tube correlations are compared. More than 400 TCR data points collected by different re-searchers during last forty years are grouped into two limiting cases: conforming rough, and elasto-constriction. Existing TCR models are reviewed and compared with the experimental data at these two limits. It is shown that the existing theoretical models do not cover both of the above-mentioned limiting cases.

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