Steady-State Theoretical Model of an Electro-Hydraulic Single-Disk Pilot Valve

1992 ◽  
Vol 114 (2) ◽  
pp. 293-298 ◽  
Author(s):  
Y. Sun ◽  
G. A. Parker
Keyword(s):  
Steady State ◽  
Theoretical Model ◽  
Experimental Verification ◽  
Control Device ◽  
Null Condition ◽  
Electromagnetic Model ◽  
Disk Valve ◽  
Single Disk ◽  
Electromagnetic Characteristics ◽  
Pilot Valve

The paper describes an electro-hydraulic single floating-disk valve suitable for use as a pilot control device. For this type of application proportional action involving small movements of the disk for the null condition is required. The theory for the steady-state linearized analysis of both the fluid and electromagnetic characteristics is developed. Experimental verification of the electromagnetic model is also described.

A Mechatronic Approach to Compact Fluid Disc Valve Design

1995 ◽  
Vol 209 (2) ◽  
pp. 115-125
Author(s):  
G A Parker ◽  
Y B Sun
Keyword(s):  
Low Cost ◽  
Dynamic Performance ◽  
Operating Mode ◽  
Industrial Applications ◽  
Test Results ◽  
Valve Design ◽  
Electromagnetic Characteristics ◽  
High Control ◽  
Fail Safe ◽  
Pilot Valve

The work presented in this paper deals mainly with a mechatronic approach to compact disc valve design and concentrates on improvements to the disc valve electromagnetic characteristics, the diaphragm design and the dynamic performance. A novel diaphragm-disc force motor has been successfully developed incorporating a pair of permanent ring magnets. It has the advantages of low electric power consumption at the null position, dual-lane electrical structure for fail-safe operation, high control accuracy and should be competitive with existing torque motors due to its low cost and simple construction. The research involved designing and testing a prototype disc pilot valve with a dual-lane operating mode. The test results showed that the valve has satisfactory static and dynamic characteristics for industrial applications.

A theoretical model of the knee and ACL: Theory and experimental verification

1992 ◽  
Vol 25 (1) ◽  
pp. 81-90 ◽  
Author(s):  
Deb A. Loch ◽  
Zongping Luo ◽  
Jack L. Lewis ◽  
Nathaniel J. Stewart
Keyword(s):  
Theoretical Model ◽  
Experimental Verification

scholarly journals Modelling the light-ion densities in the ionosphere

1996 ◽  
Vol 39 (6) ◽  
Author(s):  
S. M. Stankov
Keyword(s):  
Steady State ◽  
Theoretical Model ◽  
Satellite Measurements ◽  
Middle Latitudes ◽  
Analytical Functions ◽  
Density Ratios ◽  
Upper Ionosphere ◽  
Existing Data

A steady-state theoretical model is used to obtain variations of the H+/O+ and He+/O+ density ratios in the upper ionosphere at middle latitudes. The model results are compared with the existing data from satellite measurements. Analytical functions are constructed approximating the latitude and altitude variations of these ratios.

Analytical approach for transient photoconductivity in undoped a-Si:H

1995 ◽  
Vol 377 ◽  
Author(s):  
M. Goerlitzer ◽  
P. Pipoz ◽  
H. Beck ◽  
N. Wyrsch ◽  
A. V. Shah
Keyword(s):  
Steady State ◽  
Theoretical Model ◽  
Analytical Approach ◽  
Room Temperature ◽  
Free Electrons ◽  
Recombination Time ◽  
Sample Quality ◽  
Transient Photoconductivity ◽  
Light Intensities ◽  
Good Agreement

ABSTRACTTransient photoconductive response of undoped a-Si:H has been studied; the changes were analysed between two slightly different steady-state illumination conditions, at room temperature. A theoretical model is developed to describe transient photoconductivity; it yields good agreement with the measured curves for a whole range of light intensities. Numerical evaluations allows one to extract the recombination time of electrons. Comparison with steady-state photoconductivity yields a band mobility of free electrons between 0.1 and 6 cm2V−1s−1, depending upon sample quality.

Dynamic Analysis of a Planar SOFC Stack Fuelled by Biogas

2010 ◽  
Author(s):  
A. Salogni ◽  
D. Alberti
Keyword(s):  
Steady State ◽  
Dynamic Behaviour ◽  
Gaseous Mixture ◽  
Control Device ◽  
Organic Substrate ◽  
Pig Manure ◽  
Biological Degradation ◽  
Internal Reforming ◽  
Pure Methane ◽  
Catalytic Burner

This paper analyzes the dynamic behaviour of a 50 kW stack using planar co-flow solid oxide fuel cells with direct internal reforming fuelled by a biologically derived gaseous mixture of methane and carbon dioxide. The system modelled is composed by the SOFC stack, a catalytic burner, the heat recovery system and the control device aimed to keep the air temperature at the stack exit and the fuel utilization near to the set values. The model has been implemented using standard and user-defined components of an a-causal software based on the open-source Modelica modelling language. After a brief introduction to the production of the gaseous fuel derived from the anaerobic digestion of pig manure, data obtained from a case study on a pig farm situated in Lombardia (Italy) are presented, focusing on the yield of methane which can be exploited. The steady-state performance of the SOFC system fuelled by pure methane are compared with those obtained for the biogas working conditions, showing that the stack voltage is affected by greater concentration losses. Then, starting from a steady-state delivered current of 750 mA cm−2, the dynamic behaviour of the system when a load change of −150 mA cm−2 occurs is investigated for both pure methane and biogas fuelling hypothesis. The results of the simulations show that the transient phase is only marginally affected by the composition of the fuel, which causes a delay of about 50 s in the voltage transient. Finally, the effect obtained by imposing a linear variation in the fuel composition, which can be representative of a modification in the biological degradation of the organic substrate within the anaerobic digester, is discussed. After an initial transient, which is comparable with that obtained for a variation in the load current, the SOFC system is capable to restore the initial delivered power, provided that the required amount of fuel can be supplied to the anode.

Computational analysis of the steady state performance of an adjustable/controllable multi-pad bearing profile under LBP orientations

2020 ◽  
pp. 095440622095770
Author(s):  
Girish Hariharan ◽  
Raghuvir Pai
Keyword(s):  
Steady State ◽  
Theoretical Model ◽  
Theoretical Analysis ◽  
Film Thickness ◽  
Computational Analysis ◽  
Fluid Film ◽  
Adjustable Mechanism ◽  
State Behaviour ◽  
Steady State Behaviour ◽  
Steady State Performance

A theoretical model of a four-pad bearing profile with unique adjustable or controllable features is simulated in the present study by considering load directed between the pads. Radial and tilt adjustable mechanism of the four bearing pads can effectively control and modify the rotor operating behaviour. Inward and outward motions of the bearing pads result in the generation of narrow and broader convergent regions, which directly influences the fluid film pressures. In the theoretical analysis, load-between-pad (LBP) orientations and pad adjustment configurations are taken account of by employing a modified film thickness equation. The effect of load position in influencing the steady state behaviour of the four-pad adjustable bearing under varied pad displaced conditions is analysed in this study. The outcome of the analysis highlighted the effectiveness of four-pad adjustable bearing in improving the steady state performance by operating under negative adjustment conditions and with load acting on the bearing pads.

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