Dynamic Model for a Dome-Loaded Pressure Regulator

1997 ◽  
Vol 122 (2) ◽  
pp. 290-297 ◽  
Author(s):  
A. Nabi ◽  
E. Wacholder ◽  
J. Dayan
Keyword(s):  
Physical Model ◽  
Lumped Parameter Model ◽  
Pressure Regulator ◽  
Flow Rates ◽  
First Order ◽  
Runge Kutta Method ◽  
Lumped Parameter ◽  
Wide Range ◽  
Fast Acting ◽  
Good Agreement

A generalized physical model describing dynamic behavior of a fast-acting, dome-loaded, gas pressure regulator was developed. The regulator is designed to respond quickly to command changes, and to operate over a wide range of flow rates and pressures. The analytical lumped-parameter model developed consists of a set of nonlinear, first-order, ordinary differential equations with respect to time, accounting for mass and energy conservation at regulator outlet, command dome and internal feedback compartments. It also accounts for the equation-of-motion for the poppet and the control piston-assembly. The numerical solution, based on a Runge–Kutta method, is amenable to an extensive parametric study of regulator performance, and serves as a useful analytical tool for designing new pressure regulators. Several tests were performed on a fast-acting regulator to verify the physical model. Good agreement between predictions and measurements was obtained. The effect of several parameters, geometrical and operational, on regulator performance was studied. [S0022-0434(00)00402-0]

First-Order Pump Surge Behavior

1978 ◽  
Vol 100 (4) ◽  
pp. 459-466 ◽  
Author(s):  
P. H. Rothe ◽  
P. W. Runstadler
Keyword(s):  
Analytical Model ◽  
Flow Instability ◽  
Lumped Parameter Model ◽  
Piping System ◽  
Unstable Flow ◽  
First Order ◽  
Lumped Parameter ◽  
Quantitative Basis ◽  
Flow Oscillations ◽  
Good Agreement

This paper presents the results of an empirical study undertaken to assess the appropriateness and applicability of a simple, analytical model of pump-piping system flow instability. The analysis is used to describe behavior actually observed in a well defined, simple, pump-piping system. The frequency and amplitude of the flow oscillations observed during pump surge and the range of the pump-piping system characteristic parameters for which unstable flow oscillations occurred are in good agreement with the behavior predicted by the analysis. The results of this work provide a quantitative basis for investigating modifications to the lumped-parameter model in order to make it also appropriate for the analysis of more complex pump or compressor system. Although the analytical model displayed here is not new, a direct comparison of model predictions against similar measurements of first-order pump surge has not been published prior to this work.

Estimation of Leak Flow Rates Through Narrow Cracks

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Jae-Heon Lee
Keyword(s):  
Friction Factor ◽  
Gas Flow ◽  
Slip Flow ◽  
Nonlinear Ordinary Differential Equation ◽  
Opening Displacement ◽  
Flow Rates ◽  
Choked Flow ◽  
Runge Kutta Method ◽  
Wide Range ◽  
Leak Before Break

The estimation of the gaseous leak flow rates through a narrow crack is important for a leak-before-break analysis as a method of nondestructive testing. Therefore, the methodology to estimate the gaseous leak flow rates in a narrow crack for a wide range of flow conditions, from no-slip to slip flow and from unchoked to choked flow, by using f⋅Re (the product of friction factor and Reynolds number) correlations obtained for a microchannel, was developed and presented. The correlations applied here were proposed by the previous study (Hong, et al., 2007, “Friction Factor Correlations for Gas Flow in Slip Flow Regime,” ASME J. Fluids Eng., 129, pp. 1268–1276). The detail of the calculation procedure was appropriately documented. The fourth-order Runge–Kutta method was employed to integrate the nonlinear ordinary differential equation for the pressure, and the regular-Falsi method was employed to find the inlet Mach number. An idealized crack, whose opening displacement ranges from 2 μm to 50 μm, with the crack aspect ratio of 200, 1000, and 2000, was chosen for sample estimation. The present results were compared with both numerical simulations and available experimental measurements. The results were in excellent agreement. Therefore, the gaseous leak flow rates can be correctly predicted by using the proposed methodology.

Dynamic Modeling and Analysis of a Planetary Gear Involving Tooth Wedging and Bearing Clearance Nonlinearity

2009 ◽  
Author(s):  
Yi Guo ◽  
Robert G. Parker
Keyword(s):  
Gear Tooth ◽  
Planetary Gear ◽  
Lumped Parameter Model ◽  
Back Side ◽  
Modeling And Analysis ◽  
Bearing Clearance ◽  
Gravity Forces ◽  
Lumped Parameter ◽  
Bearing Failures ◽  
Wide Range

Tooth wedging occurs when a gear tooth comes into contact on the drive-side and back-side simultaneously. Tooth wedging risks bearing failures from elevated forces. This work studies the nonlinear tooth wedging behavior and its correlation with planet bearing forces by analyzing the dynamic response of an example planetary gear based on a real application of a wind turbine geartrain. The two-dimensional lumped-parameter model [1] is extended to include tooth separation, back-side contact, tooth wedging, and bearing clearances. The simulation results show significant impact of tooth wedging on planet bearing forces for a wide range of operating speeds. To develop a physical understanding of the tooth wedging mechanism, connections between planet bearing forces and tooth forces are studied by investigating physical forces and displacements acting throughout the planetary gear. A method to predict tooth wedging based on geometric interactions is developed and verified. The major causes of tooth wedging relate directly to translational vibrations caused by gravity forces and the presence of clearance-type nonlinearities in the form of backlash and bearing clearance.

A mathematical model for measuring blood flow in skeletal muscle with the microdialysis ethanol technique

1995 ◽  
Vol 79 (2) ◽  
pp. 648-659 ◽  
Author(s):  
F. Wallgren ◽  
G. Amberg ◽  
R. C. Hickner ◽  
U. Ekelund ◽  
L. Jorfeldt ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Muscle Tissue ◽  
Theoretical Calculations ◽  
Microdialysis Probe ◽  
Flow Rates ◽  
Perfusate Flow ◽  
Wide Range ◽  
Theory And Experiments ◽  
Good Agreement

A theoretical analysis of the microdialysis ethanol technique in skeletal muscle is presented, and a model governing the transport of ethanol from the microdialysis probe to the capillaries in the muscle tissue is proposed. The model is derived under the assumption of a steady-state situation, and an analytical solution is found for the outflow-to-inflow ratio of ethanol in the perfusate. Theoretically calculated results are compared with experiments, and for at least one of the two probe types used good agreement is achieved in a wide range of blood flow and perfusate flow rates. The main uncertainty factor in the theoretical calculations is the diffusivity of ethanol in muscle tissue, and the value for best agreement between theory and experiments has been used. Error estimates show that for a constant relative error in the outflow-to-inflow ratio of ethanol in the perfusate, low perfusate flow rates give better predictions of the blood flow.

Experimental Measurements of Ingestion Through Turbine Rim Seals—Part II: Rotationally Induced Ingress

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Carl M. Sangan ◽  
Oliver J. Pountney ◽  
Kunyuan Zhou ◽  
J. Michael Owen ◽  
Mike Wilson ◽  
...  
Keyword(s):  
Experimental Results ◽  
Radial Clearance ◽  
Rotating Fluid ◽  
Flow Rates ◽  
Hot Gas ◽  
Wide Range ◽  
The Common ◽  
Axial Clearance ◽  
Better Than ◽  
Good Agreement

Part I of this two-part paper presented experimental results for externally-induced (EI) ingress, where the ingestion of hot gas through the rim seal into the wheel-space of a gas turbine is controlled by the circumferential variation of pressure in the external annulus. In Part II, experimental results are presented for rotationally-induced (RI) ingress, where the ingestion is controlled by the pressure generated by the rotating fluid in the wheel-space. Although EI ingress is the common form of ingestion through turbine rim seals, RI ingress or combined ingress (where EI and RI ingress are both significant) is particularly important for double seals, where the pressure asymmetries are attenuated in the annular space between the inner and outer seals. In this paper, the sealing effectiveness was determined from concentration measurements, and the variation of effectiveness with sealing flow rate was compared with theoretical curves for RI ingress obtained from an orifice model. Using a nondimensional sealing parameter Φ0 the data could be collapsed onto a single curve, and the theoretical variation of effectiveness with Φ0 was in very good agreement with the data for a wide range of flow rates and rotational speeds. It was shown that the sealing flow required to prevent RI ingress was much less than that needed for EI ingress, and it was also shown that the effectiveness of a radial-clearance seal is significantly better than that for an axial-clearance seal for both EI and RI ingress.

scholarly journals Optimization of Lumped Parameter Models to Mitigate Numerical Oscillations in the Transient Responses of Short Transmission Lines

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6534
Author(s):  
Jaimis S. L. Colqui ◽  
Anderson R. J. de Araújo ◽  
Sérgio Kurokawa ◽  
José Pissolato Filho
Keyword(s):  
Power Systems ◽  
Transmission Lines ◽  
Lumped Parameter Model ◽  
Transient Responses ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Spurious Oscillations ◽  
The Time Domain ◽  
Time Transformations ◽  
Good Agreement

The Lumped Parameter Model (LPM) is a known approach to represent overhead transmission lines (TLs), especially when these elements comprehend a few tens of kilometers. LPMs employ a large number of cascaded π-circuits to compute accurately the transient responses. These responses contain numerical spurious oscillations (NSO) characterized by erroneous peaks which distort the transient responses, mainly their peak values. Two modified LPM topologies composed of damping resistances inserted along the longitudinal or transversal branches of the cascaded π-circuits offer significant mitigations in the NSO. In this paper, in an effort to have the maximum mitigation of the NSO and low distortion in the transient responses, two modified topologies with optimized damping resistances are proposed to represent short TLs. Results demonstrate expressive attenuation in the peaks of NSO which reflect good agreement in comparison with the responses computed by the Bergeron’s line model. The mitigation of the NSO is carried out directly in the time domain and it does not require either analog or digital filters.Furthermore, no frequency-to-time transformations are necessary in this procedure. These alternative topologies can be incorporated into any electromagnetic transient program to study switching operations in power systems.

scholarly journals Kinetic regularities of alloying iron-carbon alloys with vanadium

2020 ◽  
Vol 329 ◽  
pp. 02036
Author(s):  
Alexander Klimov ◽  
Michael Zinigrad
Keyword(s):  
Volume Concentration ◽  
Calculated Data ◽  
Slag Viscosity ◽  
Electrochemical Studies ◽  
Process Rate ◽  
Diffusion Mode ◽  
First Order ◽  
Air Atmosphere ◽  
Wide Range ◽  
Good Agreement

The results of the vanadium reduction laboratory investigation are presented. Experiments were conducted with CaO-SiO2 -Al2 O3 -V2 O3 slags in a wide range of compositions in an air atmosphere. A saturated iron- carbon melt was used as a reducing agent. The reduction kinetics was studied by sampling. V2 O3 reduction from slags having a viscosity of more than 0.5 Pa⋅s and containing less than 7.5–8.0% V2 O3 proceeds in a diffusion mode. The reaction is of the first order in vanadium. The process rate is inversely proportional to the square root of slag viscosity. A good agreement between the obtained data and the results of electrochemical studies on the cathodic reduction of vanadium was found. One made possible to deduce the rate equation of vanadium reduction by an iron-carbon melt depending on the volume concentration, temperature and slag viscosity. The calculated data for different slags acceptably check with those found by experiment.

APPROXIMATING THE EFFECT OF VAN DER WAALS FORCE ON THE INSTABILITY OF ELECTROSTATIC NANO-CANTILEVERS

2011 ◽  
Vol 25 (29) ◽  
pp. 3965-3976 ◽  
Author(s):  
ALI KOOCHI ◽  
AMINREZA NOGHREHABADI ◽  
MOHAMADREZA ABADYAN
Keyword(s):  
Van Der Waals ◽  
Convergent Series ◽  
Lumped Parameter Model ◽  
Distributed Parameter ◽  
Analytical Results ◽  
Lumped Parameter ◽  
Fringing Field ◽  
Beam Type ◽  
Nano Electromechanical System ◽  
Good Agreement

Beam-type nano-electromechanical system (NEMS) is one of the most components in constructing nano-devices. Herein, a distributed parameter model is used to study the influence of van der Waals (vdW) attraction on the pull-in performance of the cantilever NEMS. Homotopy perturbation method (HPM) is applied to solve the nonlinear governing equation of the actuators in the form of convergent series. Moreover, analytical results are compared with those of numerical method as well as a lumped parameter model. The pull-in voltage and critical cantilever tip deflection of NEMS are determined. Results depict that vdW attraction decreases the pull-in deflection and voltage of the NEMS. On the other hand, the fringing field increases the pull-in deflection while decreases the pull-in voltage of the system. The analytical results have good agreement with numerical results and those available in the literature.

Impedance Analysis of Silicone Rubber Filled by Electrically Conductive Nanoparticles

2012 ◽  
Vol 729 ◽  
pp. 326-331 ◽  
Author(s):  
Attila Bojtos ◽  
Antal Huba
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Construction Material ◽  
Impedance Analysis ◽  
Tensile Tests ◽  
Lumped Parameter Model ◽  
Lumped Parameter ◽  
Wide Range ◽  
Mechanical Sensors ◽  
Scanning Electron

During the research, scanning electron microscopy, compression, tensile and frequency analysis were performed on silicone rubbers filled with conductive particles , in order to understand the electrical conduction mechanism. The distribution of the conductive nanoparticles and its relationship with the substrate was examined with scanning electron microscopy (SEM). During the SEM studies, the conductive elastomers were investigated in their deformed and original state too. The connection between the deformation and the resistivity was examined with compression and tensile tests. The impedance of the material was examined on a wide range of frequency. The correctness of the lumped parameter model that is mentioned in the literature , was examined and its parameters were determined. The dependence of the resistivity on the aspect ratio of the specimens was also investigated. The aim of this research is to make this construction material intelligent, and to use it to produce hyperelastic mechanical sensors (for strain, force, torque, ect. measuring).

Applicability of an entry flow model of the brachial artery for flow models of the hemodialysis fistula

2017 ◽  
Vol 231 (8) ◽  
pp. 766-773
Author(s):  
Sulav Bastola ◽  
William D Paulson ◽  
Steven A Jones
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Arteriovenous Fistula ◽  
Brachial Artery ◽  
Poiseuille Flow ◽  
Flow Model ◽  
High Flow ◽  
Lumped Parameter Model ◽  
Flow Rates ◽  
Lumped Parameter

The native arteriovenous fistula creates a shunt that provides the high blood flow that is needed for dialysis. Lumped parameter hemodynamic models of the arteriovenous fistula can be used to predict shear stresses and pressure losses and can be applied to help understand unsolved problems such as the high rate of arteriovenous fistula maturation failure. These models combine together flow components, such as arteries, stenosis, anastomoses, arterial compliance, and blood inertia, and each component must be modeled with an appropriate pressure–flow relationship. Poiseuille flow is generally assumed for straight vessels, but the unique high flow rates within the brachial artery of an arteriovenous fistula are expected to induce entry flow effects that are neglected in this model. To estimate the importance of these effects, brachial artery flow was modeled in a low-resistance network, such as the one that occurs when an arteriovenous fistula is constructed, through the lumped parameter model, and the predicted flow rates and pressures were compared to those predicted by computational fluid dynamics. When Poiseuille flow was assumed, the flow rate from the lumped parameter model was consistently larger than that from computational fluid dynamics, with a cycle-averaged error of 36.8%. When an entry flow model (Shah) was assumed, the lumped parameter–based flow was 6% lower than the computational fluid dynamics model at the peak of the flow waveform, and the cycle-averaged error was reduced to 7.8%. Thus, in a low-resistance (high flow) arteriovenous fistula circuit, an entry flow model can account for steeper near-wall velocity gradients. This result can provide a useful guide for designing engineering models of the arteriovenous fistula.

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