The Effect of Coning on Radial Forces in Misaligned Radial Face Seals

1980 ◽  
Vol 102 (2) ◽  
pp. 139-144 ◽  
Author(s):  
I. Etsion ◽  
A. Sharoni
Keyword(s):  
Radial Force ◽  
Seal Ring ◽  
Angular Misalignment ◽  
Face Seals ◽  
Radial Forces

The effect of coning on radial forces in face seals having angular misalignment is analyzed. Both the hydrostatic and hydrodynamic components of the resultant radial force are presented. It is shown that the displacement of the primary seal ring due to the action of radial forces is always in a direction which may cause inward pumping. However, in most cases the radial force is very small.

scholarly journals Radial Forces in a Misaligned Radial Face Seal

1979 ◽  
Vol 101 (1) ◽  
pp. 81-85 ◽  
Author(s):  
I. Etsion
Keyword(s):  
Analytical Solution ◽  
Radial Force ◽  
Radial Variation ◽  
Seal Ring ◽  
Face Seal ◽  
Angular Misalignment ◽  
Radial Forces ◽  
Hydrodynamic Effects

Radial forces on the primary seal ring of a flat misaligned seal are analyzed, taking into account the radial variation in seal clearance. An analytical solution for both hydrostatic and hydrodynamic effects is presented that covers the whole range from zero to full angular misalignment. The net radial force on the primary seal ring is always directed so as to produce a radial eccentricity which generates inward pumping. Although the radial force is usually very small, in some cases it may be one of the reasons for excessive leakage through both the primary and secondary seals of a radial face seal.

Squeeze Effects in Radial Face Seals

1980 ◽  
Vol 102 (2) ◽  
pp. 145-151 ◽  
Author(s):  
I. Etsion
Keyword(s):  
Reynolds Equation ◽  
Radius Ratio ◽  
Fluid Film ◽  
Seal Ring ◽  
Face Seal ◽  
Angular Misalignment ◽  
Damping Coefficients ◽  
Wide Range ◽  
Face Seals ◽  
Hydrodynamic Effects

Squeeze effects in a liquid lubricated radial face seal are analyzed. The analysis considers face misalignment with both axial and angular vibrations of the primary seal ring. Translational, rotational, and cross-coupled damping coefficients of the fluid film are derived analytically from a solution of the Reynolds equation utilizing the narrow seal approximation. Results are given for a wide range of practical radius ratios. At each radius ratio, the complete range of angular misalignment—from parallel faces to touch down—is covered. It is shown that squeeze effects in face seals are usually larger than the more familiar hydrodynamic effects. These effects play an important role in the seal’s mechanism of operation and therefore have to be considered in any realistic seal model.

scholarly journals ‘Pave-and-crack’ technique for the recanalization of severely calcified occlusive aorto-ilio-femoral disease in type-III Leriche syndrome: a case report

2021 ◽  
Vol 5 (2) ◽  
Author(s):  
Sorin Giusca ◽  
Andrej Schmidt ◽  
Grigorios Korosoglou
Keyword(s):  
External Iliac Artery ◽  
Covered Stent ◽  
Radial Force ◽  
Covered Stents ◽  
Leriche Syndrome ◽  
Step Procedure ◽  
Technical Advances ◽  
Radial Forces ◽  
Endovascular Approach ◽  
The Right

Abstract Background  Leriche syndrome is the result of the atherosclerotic occlusion of the distal aorta that may also involve pelvic arteries. The standard treatment for this condition is considered surgical with various techniques available for establishing appropriate flow to both limbs. However, due to the technical advances in the last decades, endovascular approaches are now also capable to tackle such lesions. The ‘pave-and-crack’ technique enables the treatment of severely calcified lesions. This two-step procedure consists of firstly placing a covered stent prothesis (VIABAHN) into the severely calcified segment, which is afterwards aggressively dilated with high-pressure balloons. Subsequently, an interwoven nitinol SUPERA stent with high radial forces is placed within the prothesis. Case summary  Herein, we describe the case of an 81-year-old male patient, who presented with critical limb-threatening ischaemia of his right leg. Doppler ultrasound revealed a long occlusion of the right external iliac artery, common femoral, superficial femoral, and deep femoral artery. The lesion was successfully tackled using antegrade and retrograde punctures and the ‘pave-and-crack’ technique. Discussion  The ‘pave-and-crack’ technique is an endovascular approach for the treatment of severe circumferential calcified lesions. Based on this technique covered stents are initially placed to prevent vessel rupture, which might occur during the aggressive balloon dilatation. Subsequently, the covered stents are relined by interwoven Supera stents, which provide high radial force preventing recoil and restenosis.

scholarly journals Design of High-Speed Permanent Magnet Motor Considering Rotor Radial Force and Motor Losses

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5872 ◽  
Author(s):  
Nai-Wen Liu ◽  
Kuo-Yuan Hung ◽  
Shih-Chin Yang ◽  
Feng-Chi Lee ◽  
Chia-Jung Liu
Keyword(s):  
Permanent Magnet ◽  
High Speed ◽  
Radial Force ◽  
Nonlinear Finite Element ◽  
Motor Speed ◽  
Power Losses ◽  
Permanent Magnet Motor ◽  
Element Analysis ◽  
Radial Forces ◽  
Selection Of

Different from the design of conventional permanent magnet (PM) motors, high-speed motors are primarily limited by rotor unbalanced radial forces, rotor power losses, and rotor mechanical strength. This paper aimed to propose a suitable PM motor with consideration of these design issues. First, the rotor radial force is minimized based on the selection of stator tooth numbers and windings. By designing a stator with even slots, the rotor radial force can be canceled, leading to better rotor strength at high speed. Second, rotor power losses proportional to rotor frequency are increased as motor speed increases. A two-dimensional sensitivity analysis is used to improve these losses. In addition, the rotor sleeve loss can be minimized to less than 8.3% of the total losses using slotless windings. Third, the trapezoidal drive can cause more than a 33% magnet loss due to additional armature flux harmonics. This drive reflected loss is also mitigated with slotless windings. In this paper, six PM motors with different tooth numbers, stator cores, and winding layouts are compared. All the design methods are verified based on nonlinear finite element analysis (FEA).

The Rotor Dynamic Coefficients of Eccentric Mechanical Face Seals

1996 ◽  
Vol 118 (1) ◽  
pp. 215-224 ◽  
Author(s):  
J. Wileman ◽  
I. Green
Keyword(s):  
Degrees Of Freedom ◽  
Reynolds Equation ◽  
Equations Of Motion ◽  
Shear Stresses ◽  
Dynamic Coefficients ◽  
Angular Deflection ◽  
Face Seals ◽  
Radial Forces ◽  
Rotor Dynamic ◽  
Additional Coupling

The Reynolds equation is extended to include the effects of radial deflection in a seal with two flexibly mounted rotors. The resulting pressures are used to obtain the forces and moments introduced in the axial and angular modes by the inclusion of eccentricity in the analysis. The rotor dynamic coefficients relating the forces and moments in these modes to the axial and angular deflection are shown to be the same as those presented in the literature for the concentric case. Additional coefficients are obtained to express the dependence of these forces and moments upon the radial deflections and velocities. The axial force is shown to be decoupled from both the angular and radial modes, but the angular and radial modes are coupled to one another by the dependence of the tilting moments upon the radial deflections. The shear stresses acting upon the element faces are derived and used to obtain the radial forces acting upon the rotors. These forces are used to obtain rotor dynamic coefficients for the two radial degrees of freedom of each rotor. The additional rotor dynamic coefficients can be used to obtain the additional equations of motion necessary to include the radial degrees of freedom in the dynamic analysis. These coefficients introduce additional coupling between the angular and radial degrees of freedom, but the axial degrees of freedom remain decoupled.

The NC Mechanism of Reciprocating Rectilinear Movement at High Frequency Based on Two Symmetrical Cranks

2011 ◽  
Vol 201-203 ◽  
pp. 2224-2228
Author(s):  
Ming Di Wang ◽  
Kang Min Zhong ◽  
Zheng Chen
Keyword(s):  
High Frequency ◽  
Radial Force ◽  
Friction Loss ◽  
Reciprocating Motion ◽  
Linear Movement ◽  
Radial Forces ◽  
Scope Of Application ◽  
Vibration Noise

The reciprocating rectilinear moving mechanism is applied widely in the industry, which is now usually driven by the non-symmetrical mechanism. Due to the changing radial force generated by the slider, the big friction loss and the vibration noise are caused. And, the size of travel in reciprocating motion is fixed and can not be adjusted. In order to overcome these defections, the reciprocating rectilinear moving mechanism at high frequency driven by the stepper or servo motors based on two symmetrical cranks is innovated in this paper, in which the linear movement is converted by the two cranks. The radial forces in this innovated mechanism are quite symmetrical and balanced, so the friction loss can be almost ignored and the oscillation noise is very small too. Then, through programming, the angle range of stepper or servo motors can be controlled to output any required displacement and any required force. Thus, the scope of application of this mechanism is expanded extremely.

Hydrodynamic Design of the Volute of a Centrifugal Pump Using CFD

2011 ◽  
Author(s):  
Rouhollah Torabi ◽  
S. Ahmad Nourbakhsh
Keyword(s):  
Viscous Flow ◽  
Centrifugal Pump ◽  
Static Pressure ◽  
Design Method ◽  
Radial Force ◽  
Inverse Design ◽  
Radial Forces ◽  
Low Specific Speed ◽  
Specific Speed ◽  
Inverse Design Method

The objective of this paper is to develop the shape of an existing volute so that the radial forces in off-design condition become minimum. For this purpose 3-D inverse design method based on the 3-D viscous flow calculations was applied to re-design the geometry of the volute of a low specific speed pump. Various aspects of the geometry change independently to achieve the best one which produces less radial force in off design conditions. Measurements included time-averaged values of velocity and static pressure at a large number of locations in the volute.

Radial forces of stents used in thoracic endovascular aortic repair and bare self-expanding nitinol stents measured ex vivo – Rapid rescue for obstruction of the innominate artery using bare self-expanding nitinol stents

Vascular ◽  
2016 ◽  
Vol 25 (1) ◽  
pp. 36-41 ◽  
Author(s):  
Takuya Matsumoto ◽  
Kentaro Inoue ◽  
Shinichi Tanaka ◽  
Yukihiko Aoyagi ◽  
Yutaka Matsubara ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Testing Machine ◽  
Innominate Artery ◽  
Radial Force ◽  
Thoracic Endovascular Aortic Repair ◽  
Endovascular Aortic Repair ◽  
Machine Model ◽  
Aortic Repair ◽  
Nitinol Stents ◽  
Radial Forces

Purpose Our objective was to compare the radial forces of several stents ex vivo to identify stents suitable for rescue of the unexpected coverage of aortic arch branches in thoracic endovascular aortic repair. Methods We measured the radial forces of two types of self-expanding bare nitinol stents (E-luminexx and Epic) used singly or as double-walled pairs, and of three endoprostheses used in thoracic endovascular aortic repair (TEVAR, Gore c-TAG, Relay, and Valiant) by compressing the stent using an MTS Instron universal testing machine (model #5582). We also examined the compressive effects of the TEVAR endoprostheses and the bare nitinol stents on each other. Results The radial force was greater in the center than at the edge of each stent. In all stents tested, the radial force decreased incrementally with increasing stent diameter. The radial force at the center was two times greater when using two stents than with a single stent. In the compression test, only E-luminexx used as a pair was not compressed after compressing a Relay endoprosthesis by 12 mm. Conclusion Two E-luminexx stents are appropriate to restore the blood flow if a TEVAR endoprosthesis covers the innominate artery following innominate–carotid–left subclavian arterial bypass.

Study on Radial Forces of Centrifugal Pumps With Various Collectors

2011 ◽  
Author(s):  
Zhongyong Pan ◽  
Junjie Li ◽  
Shuai Li ◽  
Shouqi Yuan
Keyword(s):  
Numerical Simulation ◽  
Pressure Distribution ◽  
Radial Force ◽  
Time Dependent ◽  
Centrifugal Pumps ◽  
Flow Rates ◽  
Trade Off ◽  
Blade Passage ◽  
Design Choice ◽  
Radial Forces

Numerical simulation is presented to study the steady and unsteady radial forces in a centrifugal pump with various collectors. The radial forces are obtained by integrating the pressure distribution around the impeller circumference. The calculated radial forces both time-dependent and independent at different flow rates caused by the collectors are compared. The results show that some conclusions do not consistent with the conventional experience as the collectors with double volute and vaned volute significantly decrease the radial forces and the radial force close a circle during the period of one blade passage passing. The combination of impeller and double volute is a trade-off design choice as it has significantly decreased the radial forces than that of single volute and its configuration is more compact than that of vaned collector.

Radial Force on the Impeller of Centrifugal Pumps With Volute, Semivolute, and Fully Concentric Casings

1965 ◽  
Vol 87 (3) ◽  
pp. 319-322 ◽  
Author(s):  
H. Joseph Biheller
Keyword(s):  
Experimental Investigation ◽  
Centrifugal Pump ◽  
Radial Force ◽  
Operating Speed ◽  
Centrifugal Pumps ◽  
Operating Range ◽  
Aspect Ratios ◽  
Radial Forces

An experimental investigation of the magnitude and direction of the unbalanced radial force on centrifugal pump impellers was made. Pumps with single volute, semiconcentric and fully concentric casings of several specific speeds, collector aspect ratios, and with both closed and semiclosed impellers were tested over the full operating range. An equation enabling prediction of expected radial forces based only on pump geometry, operating speed, and capacity (expressed as fraction of capacity at best efficiency) is presented.

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