Dynamic Coupling Effects in Rotary Face Seal Separation Phenomena

1967 ◽  
Vol 89 (2) ◽  
pp. 296-300 ◽  
Author(s):  
F. D. Hart ◽  
C. F. Zorowski

Dynamic separation phenomena in spring-supported rotary face seals are studied, employing a mathematical model which simulates the dynamic response characteristics of the system. Parameters considered in the model include support resilience, amplitude of shaft pulsation and mating ring wobble, initial preset, operating frequency, and contact surface friction. Inclusion of contact friction necessitates consideration of dynamic coupling in the equations governing the motion of the seal carrier. Combinations of operating conditions and system variables which produce incipient mechanical separation are predicted by examining the behavior of the contact force distribution between the seal and mating ring. Equations and graphs are presented which specify the theoretical preset required to maintain continuous contact as a function of the system parameters considered in the analysis.

1976 ◽  
Vol 98 (3) ◽  
pp. 835-839 ◽  
Author(s):  
F. D. Hart ◽  
B. M. Patel ◽  
J. R. Bailey

Mechanical separation between cam and pick ball in fly-shuttle looms gives rise to impact and vibration which causes significant noise emission. Elimination of separation is analyzed using a mathematical model which simulates the dynamic response characteristics of the system. Parameters considered in the study include equivalent stiffness, mass, and damping of the system, amplitude of excitation, effect of preload provided by a retaining spring, and operating frequency. Combinations of system parameters and operating conditions which give rise to separation are predicted by examining the contact force developed between cam and cam-follower. Equations and graphs are presented that specify the preload required to eliminate separation as a function of the system parameters.


Author(s):  
Franklin D. Hart ◽  
Carl F. Zorowski

The problem of incipient dynamic mechanical separation in bellows-supported rotary face seals is analyzed assuming the bellows to be represented by a series of distributed springs and dampers supporting a rigid seal carrier. An expression is developed for the distribution of contact forces between the seal and mating rings generated by the coupled effects of shaft pulsation and mating-ring wobble. This expression is used to determine the operating conditions which will produce the onset of separation by applying the criterion that the contact force distribution will go to zero at some point on the seal when separation is imminent. Results are presented in the form of equations and graphs which define the minimum initial compression necessary to maintain continuous contact in terms of system resilience and damping, amplitude of mating-ring wobble and shaft pulsation, and operating frequency.


Author(s):  
Ming Zhang ◽  
Dafu Xu ◽  
Shuai Yue ◽  
Haifeng Tao

Landing gear system is a key part of the implementation of reusable vertical takeoff and vertical landing launch vehicle, where its buffing performance is directly related to the vehicle whether it can land safely or stably. According to the reusable launch vehicle general scheme, outrigger landing legs are designed, and the hydraulic absorber is used for the landing gear system. Meanwhile, a scaling principle prototype of landing gear system is developed, and the landing impact test is carried out. A dynamic simulation model of the landing vehicle has been set up, researching the influence of parameters, such as the horizontal velocity, initial inclination, surface friction coefficient, and pitch angular velocity on the landing performance. Four kinds of extreme conditions are identified, and dynamic response characteristics of landing system under each extreme condition are conducted. The simulation results are in good agreement with the experimental data. The buffing performance of the vehicle meets the design requirements, which provides a reference for the design of landing gear system of the vehicle.


Author(s):  
Darina Hroncová

Urgency of the research. Computer models mean new quality in the knowledge process. Using a computer model, the properties of the subject under investigation can be tested under different operating conditions. By experimenting with a com-puter model, we learn about the modelled object. We can test different machine variants without having to produce and edit prototypes. Target setting. The development of computer technology has expanded the possibility of solving mathematical models and allowed to gradually automate the calculation of mathematical model equations. It is necessary to insert appropriate inputs of the mathematical model and monitor and evaluate the output results through the computer output device The target was to describe the mathematical apparatus required for mathematical modeling and subsequently to compile a model for computer modeling. Actual scientific researches and issues analysis. When formulating a mathematical model for a computer, the laws and the theory we use are always valid under more or less idealized conditions, and operate with fictitious concepts such as, material point, ideal gas, intangible spring, and the like. However, with these simplifications, we describe a realistic phenomenon where the initial assumptions are only met to a certain extent. In order for the results not to be different from the modeled reality, it is to be assumed that a good computer model arises gradually, by verifying and modifying it, which is one of the advantages of MSC Adams. Uninvestigated parts of general matters defining. The question of building a real manipulator model. Based on the above simulation, it is possible to build a real model. The research objective. Using MSC Adams to simulate multiple body systems and verify its suitability for simulating ma-nipulator and robot models. In various versions of the assembled model we can monitor its behavior under different operating conditions. The statement of basic materials. In computer simulation, MSC Adams-View is used to simulate mechanical systems. It has an interactive environment for automated dynamic analysis of parameterized mechanical systems with an arbitrary struc-ture of rigid and flexible bodies with geometric or force joints, in which act gravity, inertia, experimentally designed contact, friction, aerodynamic, hydrodynamic or electromechanical forces and have integrated control, hydraulic, pneumatic or elec-tromechanical circuits. Conclusions. Working with a mathematical model on a computer opens space for specific synthesis of empirical and ana-lytical method of scientific knowledge. Working with the computer model carries the characteristic features of classical experi-mentation. It represents a qualitatively new way of solving tasks that can not be experimented with on a real object. The result is the equivalence of the computer model and the object being investigated with the features and expressions chosen as essen-tial, with accuracy sufficient to the exact purpose.


Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3906 ◽  
Author(s):  
Xuesong Zhou ◽  
Mao Liu ◽  
Youjie Ma ◽  
Bao Yang ◽  
Faqing Zhao

The wind power grid-connected inverter system has nonlinear, strong coupling, and is susceptible to grid voltage fluctuations and nonlinear load effects. To achieve satisfactory control results, the voltage outer loop is controlled by an improved linear active disturbance rejection control (LADRC). LADRC has strong adaptability, robustness and operability. It can automatically detect and compensate for internal and external disturbances, and correct complex controlled objects to integrator series. The total perturbation differential signal is introduced in the traditional linear extended state observer (LESO), which improves the dynamic perturbation observation ability of LESO. The frequency response characteristics analysis shows that the new LADRC has better anti-interference performance. The effectiveness of the improved controller under multiple operating conditions is verified by simulation.


Author(s):  
Sitae Kim ◽  
Alan B. Palazzolo

The double-sided fluid film force on the inner and outer ring surfaces of a floating ring bearing (FRB) creates strong nonlinear response characteristics such as coexistence of multiple orbits, Hopf bifurcation, Neimark-Sacker (N-S) bifurcation, and chaos in operations. An improved autonomous shooting with deflation algorithm is applied to a rigid rotor supported by FRBs for numerically analyzing its nonlinear behavior. The method enhances computation efficiency by avoiding previously found solutions in the numerical-based search. The solution manifold for phase state and period is obtained using arc-length continuation. It was determined that the FRB-rotor system has multiple response states near Hopf and N-S bifurcation points, and the bifurcation scenario depends on the ratio of floating ring length and diameter (L/D). Since multiple responses coexist under the same operating conditions, simulation of jumps between two stable limit cycles from potential disturbance such as sudden base excitation is demonstrated. In addition, this paper investigates chaotic motions in the FRB-rotor system, utilizing four different approaches, strange attractor, Lyapunov exponent, frequency spectrum, and bifurcation diagram. A numerical case study for quenching the large amplitude motion by adding unbalance force is provided and the result shows synchronization, i.e., subsynchronous frequency components are suppressed. In this research, the fluid film forces on the FRB are determined by applying the finite element method while prior work has utilized a short bearing approximation. Simulation response comparisons between the short bearing and finite bearing models are discussed.


2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Rupesh Roshan ◽  
Martin Priest ◽  
Anne Neville ◽  
Ardian Morina ◽  
Xin Xia ◽  
...  

Theoretical studies have shown that in severe operating conditions, valve train friction losses are significant and have an adverse effect on fuel efficiency. However, recent studies have shown that existing valve train friction models do not reliably predict friction in boundary and mixed lubrication conditions and are not sensitive to lubricant chemistry. In these conditions, the friction losses depend on the tribological performance of tribofilms formed as a result of surface–lubricant additive interactions. In this study, key tribological parameters were extracted from a direct acting tappet type Ford Zetec SE (Sigma) valve train, and controlled experiments were performed in a block-on-ring tribometer under conditions representative of boundary lubrication in a cam and follower contact. Friction was recorded for the tribofilms formed by molybdenum dithiocarbamate (MoDTC), zinc dialkyldithiophosphate (ZDDP), detergent (calcium sulfonate), and dispersant (polyisobutylene succinimide) additives in an ester-containing synthetic polyalphaolefin (PAO) base oil on AISI E52100 steel components. A multiple linear regression technique was used to obtain a friction model in boundary lubrication from the friction data taken from the block-on-ring tribometer tests. The model was developed empirically as a function of the ZDDP, MoDTC, detergent, and dispersant concentration in the oil and the temperature and sliding speed. The resulting friction model is sensitive to lubricant chemistry in boundary lubrication. The tribofilm friction model showed sensitivity to the ZDDP–MoDTC, MoDTC–dispersant, MoDTC–speed, ZDDP–temperature, detergent–temperature, and detergent–speed interactions. Friction decreases with an increase in the temperature for all ZDDP/MoDTC ratios, and oils containing detergent and dispersant showed high friction due to antagonistic interactions between MoDTC–detergent and MoDTC–dispersant additive combinations.


Author(s):  
Brian Sperry ◽  
Corina Sandu ◽  
Brent Ballew

This research focuses on the dynamic behavior of the three-piece bogie that supports the freight train car bodies. While the system is relatively simple, in that there are very few parts involved, the behavior of the bogie is somewhat more complex. Our research focuses primarily on the behavior of the friction wedges under different operating conditions that are seen under normal operation. The Railway Technologies Laboratory (RTL) at Virginia Tech has been developing a model to better capture the dynamic behavior of friction wedges using 3-D modeling software. In previous years, a quarter-truck model, and half-truck variably damped model have been developed using MathWorks MATLAB®. This year, research has focused on the development of a half-truck variably damped model with a new (curved surface) friction wedge, and a half-truck constantly damped model, both using the MATLAB® based software program. Currently a full-truck variably damped model has been created using LMS Virtual.Lab. This software allows for a model that is more easily created and modified, as well as allowing for a much shorter simulation time, which became a necessity as more contact points, and more complex inputs were needed to increase the accuracy of the simulation results. The new model consists of seven rigid bodies: the bolster, two sideframes, and four wedges. We have also implemented full spring nests on each sideframe, where in previous models equivalent spring forces were used. The model allows six degrees-of-freedom for the wedges and bolster: lateral, longitudinal, and vertical translations, as well as pitch, roll, and yaw. The sideframes are constrained to two degrees-of-freedom: vertical and longitudinal translations. The inputs to the model are vertical and longitudinal translations or forces on the sideframes, which can be set completely independent of each other. The model simulation results have been compared with results from NUCARS®, an industrially-used train modeling software developed by the Transportation Technology Center, Inc. (TTCI), a wholly owned subsidiary of the Association of American Railroads (AAR), for similar inputs, as well as experimental data from warping tests performed at TTCI.


Multi input converters are highly reliable and can be effectively used for hybrid systems. Here the performance of a dual input system is experimentally verified by powering it with a solar and a battery and the whole system is monitored using IOT. A DC to DC converter which can operate with two sources is designed to operate with two input DC sources and the output DC supply is converted to AC by an inverter module. Power IOT based monitoring system is the main scope of this project which is achieved using an ESP8266 Arduino core and GSM technique. High conversion efficiency, soft switching realization and simple architecture are achieved in this system. The simulation results is presented under various values of operating conditions. A scale down model was developed which is powered by a 3Wp solar panel and a 12 V battery. The performance of the system was verified with various input conditions and the system parameters were monitored using IOT and the data samples were obtained.


Author(s):  
Julia Pasternack ◽  
Dan Thayer ◽  
Rohan Bansal ◽  
Ehsan Maleki ◽  
Greg Tao ◽  
...  

This paper describes the development of a feedback controller for rejecting wind disturbances on a crane payload. The goal of this research is to perform in-situ parameter sensitivity testing that is specific to a given crane structure. Through experimentation, this paper evaluates the robustness of a closed-loop controller that implements station keeping on a bridge crane. A set of general trends were developed to describe how altering system parameters and operating conditions affected controller performance. Such findings are not limited to single parameter characterization and can be extended to multiple variables given specific system specifications.


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