Lubrication and stability enhancement by attaching superconducting magnetic force on non-contacting mechanical seals for reusable rocket turbopump

2021 ◽  
pp. 135065012110397
Author(s):  
Lushuai Xu ◽  
Jiu Hui Wu ◽  
Yunlei Wang ◽  
Faisal Rafique ◽  
Jimin Xu ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Magnetic Force ◽  
Appreciable Effect ◽  
Mechanical Seals ◽  
Time Step ◽  
Turbulence Flow ◽  
Lubrication Performance ◽  
Clearance Flow ◽  
Lubrication Characteristics ◽  
Stability Enhancement

The purpose of this paper is to investigate the lubrication performance and stability improvement of rocket turbopump mechanical seals by attaching superconducting magnetic force. A comprehensive multiphysics numerical model is presented including microscale clearance flow, magnetic field, as well as three degrees of freedom dynamic motion. The Maxwell equation and modified Reynolds equation considering mass-conserving boundary conditions and turbulence flow were solved simultaneously at each time step to obtain the transient response of sealing parameters. Results indicate that the mechanical seal attaching superconducting magnetic force could dramatically improve carrying capacity and lubrication characteristics under heavy loading conditions, and it also has an appreciable effect on dynamic stability. It is worth exploring the application of superconducting magnetic force in reusable rockets and cryogenic equipment combined with its unique advantages.

Influence of Clearances and Thermal Effects on the Dynamic Behavior of Gear-Hydrodynamic Journal Bearing Systems

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
R. Fargère ◽  
P. Velex
Keyword(s):  
Degrees Of Freedom ◽  
Integration Scheme ◽  
Time Step ◽  
Specific Element ◽  
Normal Contact ◽  
Contact Algorithm ◽  
Gear Teeth ◽  
Proposed Model ◽  
Elastic Couplings ◽  
Definition Of

A global model of mechanical transmissions is introduced which deals with most of the possible interactions between gears, shafts, and hydrodynamic journal bearings. A specific element for wide-faced gears with nonlinear time-varying mesh stiffness and tooth shape deviations is combined with shaft finite elements, whereas the bearing contributions are introduced based on the direct solution of Reynolds' equation. Because of the large bearing clearances, particular attention has been paid to the definition of the degrees-of-freedom and their datum. Solutions are derived by combining a time step integration scheme, a Newton–Raphson method, and a normal contact algorithm in such a way that the contact conditions in the bearings and on the gear teeth are simultaneously dealt with. A series of comparisons with the experimental results obtained on a test rig are given which prove that the proposed model is sound. Finally, a number of results are presented which show that parameters often discarded in global models such as the location of the oil inlet area, the oil temperature in the bearings, the clearance/elastic couplings interactions, etc. can be influential on static and dynamic tooth loading.

Vibration analysis of multiple degrees of freedom mechanical system with dry friction

2012 ◽  
Vol 227 (7) ◽  
pp. 1505-1514 ◽  
Author(s):  
SD Yu ◽  
BC Wen
Keyword(s):  
Mechanical System ◽  
Dry Friction ◽  
Degrees Of Freedom ◽  
Simple Procedure ◽  
Mathematical Problem ◽  
Equations Of Motion ◽  
Inequality Constraints ◽  
Integration Scheme ◽  
Time Step ◽  
Multiple Degrees Of Freedom

This article presents a simple procedure for predicting time-domain vibrational behaviors of a multiple degrees of freedom mechanical system with dry friction. The system equations of motion are discretized by means of the implicit Bozzak–Newmark integration scheme. At each time step, the discontinuous frictional force problem involving both the equality and inequality constraints is successfully reduced to a quadratic mathematical problem or the linear complementary problem with the introduction of non-negative and complementary variable pairs (supremum velocities and slack forces). The so-obtained complementary equations in the complementary pairs can be solved efficiently using the Lemke algorithm. Results for several single degree of freedom and multiple degrees of freedom problems with one-dimensional frictional constraints and the classical Coulomb frictional model are obtained using the proposed procedure and compared with those obtained using other approaches. The proposed procedure is found to be accurate, efficient, and robust in solving non-smooth vibration problems of multiple degrees of freedom systems with dry friction. The proposed procedure can also be applied to systems with two-dimensional frictional constraints and more sophisticated frictional models.

Effect of recess depth on lubrication performance of annular recess hydrostatic thrust bearing by constant rate flow

2018 ◽  
Vol 70 (1) ◽  
pp. 68-75 ◽  
Author(s):  
Jun-peng Shao ◽  
Guang-dong Liu ◽  
Xiao-dong Yu ◽  
Yan-qin Zhang ◽  
Xiu-li Meng ◽  
...  
Keyword(s):  
Thrust Bearing ◽  
Simulation Method ◽  
Content Type ◽  
Oil Film ◽  
Constant Rate ◽  
Lubrication Performance ◽  
Optimal Value ◽  
Improved Performance ◽  
Lubrication Characteristics ◽  
Volume Method

Purpose The purpose of this paper is to describe a simulation and experimental research concerning the effect of recess depth on the lubrication performance of a hydrostatic thrust bearing by constant rate flow. Design/methodology/approach The computational fluid dynamics and finite volume method have been used to compute the lubrication characteristics of an annular recess hydrostatic thrust bearing with different recess depths. The performances are oil recess pressure, oil recess temperature and oil film velocity. The recess depth has been optimized. A test rig is established for testing the pressure field of the structure of hydrostatic thrust bearing after recess depth optimization, and experimental results show that experimental data are basically identical with the simulation results, which demonstrates the validity of the proposed numerical simulation method. Findings The results demonstrate that the oil film temperature decreases and the oil film pressure first increases and then decreases with an increase in the recess depth, but oil film velocity is constant. To sum up comprehensive lubrication performance, the recess depth of 3.5 mm is its optimal value for the annular recess hydrostatic thrust bearing. Originality/value The computed results indicate that to get an improved performance from a constant flow hydrostatic thrust bearing, a proper selection of the recess depth is essential.

A study on diesel engine crankshaft bearing failure analysis with consideration of bearing lubrication

2022 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Qi Liu ◽  
Baiqi Huo ◽  
Yunsheng Liu ◽  
Junchao Zhu
Keyword(s):  
Diesel Engine ◽  
Failure Mechanism ◽  
Working Condition ◽  
Mixed Lubrication ◽  
Bearing Failure ◽  
Content Type ◽  
Lubrication Performance ◽  
Lubrication Characteristics ◽  
The Relationship ◽  
Engine Crankshaft

Purpose The edge of diesel engine crankshaft main bearing is more likely to fail in its real working condition. This paper aims to study the bearing failure mechanism by finding the relationship between bearing lubrication characteristics and its working condition. Design/methodology/approach This work builds the mixed lubrication model of crankshaft bearing to analyze the cause of bearing abnormal wear, and the finite difference method was used to solving the average Reynolds equation. During the analysis, journal misaligned angle, external load and roughness are considered. Findings The result shows that the wear of the diesel engine crankshaft bearing happens in engine startup phase and the bottom of the bearing are more prone to be excessively worn. Under the influence of journal misalignment, bearing asperity contact load and speed range of mixed lubrication will increase markedly. The edge of the bearing will be excessively worn. The effect of misalignment on bearing lubrication performance varies under different shaft rotation speed. Originality/value The former research studies on crankshaft bearing either just focused on its lubrication characteristics or interested in its failure types (wear, adhere, cavitation). This paper studies the relationship between bearing failure mechanism and lubrication performance.

scholarly journals Learning data-driven reduced elastic and inelastic models of spot-welded patches

2021 ◽  
Vol 22 ◽  
pp. 32
Author(s):  
Agathe Reille ◽  
Victor Champaney ◽  
Fatima Daim ◽  
Yves Tourbier ◽  
Nicolas Hascoet ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Structural Response ◽  
Data Driven ◽  
Fine Scale ◽  
Time Step ◽  
Large Structures ◽  
Computational Performance ◽  
Local Patch ◽  
The Rich ◽  
Learning Data

Solving mechanical problems in large structures with rich localized behaviors remains a challenging issue despite the enormous advances in numerical procedures and computational performance. In particular, these localized behaviors need for extremely fine descriptions, and this has an associated impact in the number of degrees of freedom from one side, and the decrease of the time step employed in usual explicit time integrations, whose stability scales with the size of the smallest element involved in the mesh. In the present work we propose a data-driven technique for learning the rich behavior of a local patch and integrate it into a standard coarser description at the structure level. Thus, localized behaviors impact the global structural response without needing an explicit description of that fine scale behaviors.

scholarly journals WAVELESS APPROXIMATION THEORIES OF GRAVITY

2008 ◽  
Vol 17 (02) ◽  
pp. 265-273 ◽  
Author(s):  
JAMES A. ISENBERG
Keyword(s):  
Gravitational Field ◽  
Gravitational Radiation ◽  
Elliptic Equations ◽  
Degrees Of Freedom ◽  
Dynamic Instability ◽  
Accurate Approximation ◽  
Time Step ◽  
Einstein Theory ◽  
Physical Systems ◽  
Theories Of Gravity

The analysis of a general multibody physical system governed by Einstein's equations is quite difficult, even if numerical methods (on a computer) are used. Some of the difficulties — many coupled degrees of freedom, dynamic instability — are associated with the presence of gravitational waves. We have developed a number of "waveless approximation theories" (WAT's) which repress the gravitational radiation and thereby simplify the analysis. The matter, according to these theories, evolves dynamically. The gravitational field, however, is determined at each time step by a set of elliptic equations with matter sources. There is reason to believe that for many physical systems, the WAT-generated system evolution is a very accurate approximation to that generated by the full Einstein theory.

Effect of piston clearance on the lubrication performance in axial piston pump

2019 ◽  
Vol 72 (1) ◽  
pp. 146-150
Author(s):  
Bora Lee ◽  
Yonghun Yu ◽  
Yong-Joo Cho
Keyword(s):  
Reynolds Equation ◽  
Design Method ◽  
Contact Region ◽  
Content Type ◽  
Piston Cylinder ◽  
Leakage Flow Rate ◽  
Lubrication Performance ◽  
Secondary Motion ◽  
Lubrication Characteristics ◽  
Axial Piston

Purpose This paper aims to provide a reliable and efficient numerical piston–cylinder design method and assess the effect of clearance on the piston-cylinder lubrication. Design/methodology/approach Numerical analyses of lubrication characteristics were performed for the piston–cylinder interface. The axial piston was numerically modeled, and the film pressure was calculated using the unsteady two-dimensional Reynolds equation. The behavior of the piston was analyzed by calculating the eccentricity satisfying the force and moment balance. Findings The secondary motion of the piston included numerically simulated several cycles until the piston behavior converged, and contact with the inner wall of the cylinder and friction region was estimated. Results showed that the piston–cylinder clearance affected the contact force, length of the contact region and leakage flow rate. Originality/value This result improves the understanding of the piston–cylinder lubrication and suggests considerations in terms of lubrication in clearance design.

Influence of Oil-Returning Slot on Load Capacity of Heavy Constant Flow Hydrostatic Center Rest

2014 ◽  
Vol 494-495 ◽  
pp. 633-636
Author(s):  
Bo Wu ◽  
Zhi Huang ◽  
Xiao Dong Yu ◽  
Hui Jiang ◽  
Chun Zhou Wang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Load Capacity ◽  
Flow State ◽  
Constant Flow ◽  
Heavy Equipment ◽  
Lubrication Performance ◽  
Oil Flow ◽  
Lubrication Characteristics ◽  
Volume Method

In order to increase load capacity of a heavy constant flow hydrostatic center rest, a theoretical study concerning the lubrication performance of the heavy constant flow hydrostatic center rest is described. The Computational Fluid Dynamics and the Finite Volume Method have been used to compute lubrication characteristics, such as the recess pressure and the oil flow state. The influences of oil-returning slot on the load capacity of the heavy constant flow hydrostatic center rest was analyzed based on the computational fluid dynamics and lubrication theory, and the influencing laws were revealed. Through this method, the reasonable data can be provided for optimal design and lubrication performance improving of the constant flow hydrostatic center rest in the heavy equipment.

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