scholarly journals Dry Friction Damping Mechanisms in Engine Blades

1982 ◽  
Author(s):  
A. V. Srinivasan ◽  
D. G. Cutts
Keyword(s):  
Laboratory Test ◽  
Test Data ◽  
Dry Friction ◽  
Turbine Blades ◽  
Experimental Studies ◽  
Vibration Damping ◽  
Analytical Models ◽  
Jet Engines ◽  
Blade Vibration ◽  
Dry Friction Damping

In the context of jet engines, significant vibration damping due to dry friction can occur at (a) shroud interfaces of fans and (b) the platform of turbine blades fitted with “platform dampers.” Analytical and experimental studies in regard to this important source of nonaerodynamic damping of blade vibration are presented in this paper. Comparisons between results from analytical models and laboratory test data are made and discussed.

Dry Friction Damping Mechanisms in Engine Blades

1983 ◽  
Vol 105 (2) ◽  
pp. 332-341 ◽  
Author(s):  
A. V. Srinivasan ◽  
D. G. Cutts
Keyword(s):  
Laboratory Test ◽  
Test Data ◽  
Dry Friction ◽  
Turbine Blades ◽  
Experimental Studies ◽  
Vibration Damping ◽  
Analytical Models ◽  
Jet Engines ◽  
Blade Vibration ◽  
Dry Friction Damping

In the context of jet engines, significant vibration damping due to dry friction can occur at (a) shroud interfaces of fans and (b) the platform of turbine blades fitted with “platform dampers.” Analytical and experimental studies in regard to this important source of nonaerodynamic damping of blade vibration are presented in this paper. Comparisons between results from analytical models and laboratory test data are made and discussed.

Experimental Study of Dynamic Characteristics of Dry Friction Damping of Turbine Blade Steel

2013 ◽  
Vol 690-693 ◽  
pp. 1979-1982 ◽  
Author(s):  
Peng Fei Zhao ◽  
Qiang Zhang ◽  
Jun Wu ◽  
Di Zhang
Keyword(s):  
Dry Friction ◽  
Turbine Blades ◽  
Initial Pressure ◽  
Relative Displacement ◽  
Radius Of Curvature ◽  
Response Analysis ◽  
Friction Damper ◽  
Friction Damping ◽  
Stick Slip ◽  
Dry Friction Damping

For lot of structures, especially turbine blades, damper can dissipate the vibration energy by friction. Investigating the property of metal dry friction damping can give many usable data for response analysis of damping blade which is important in damped blade designs. The paper constructs an experimental rig and carries out experiment with pieces having radius of curvature 6mm, 12mm and 24mm. The relative displacement between contact surfaces and the friction force changed with time were obtained for different initial pressure and frequency of exciting force. Hysteresis curves of dry friction damper were derived. The variations of friction coefficient of stick-slip area, equivalent stiffness and equivalent damping were calculated based on experimental data.

scholarly journals Influence of the Dry Friction Suspension System Characteristics on the Stick-Slip of Vertical Vibration of a Three-Piece Bogie

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Dali Lyu ◽  
Qichang Zhang ◽  
Kewei Lyu ◽  
Jiaxing Liu ◽  
Yulong Li
Keyword(s):  
Numerical Method ◽  
Dry Friction ◽  
Wedge Angle ◽  
Vertical Vibration ◽  
Vibration Damping ◽  
Suspension System ◽  
Railway Vehicle ◽  
Stick Slip ◽  
System Frequency ◽  
Dry Friction Damping

The dry friction structure is a commonly used vibration-damping method for railway vehicles. Insufficient vibration damping performance will cause excessive vibration of the vehicle, which is not conducive to the safety of the vehicle. However, the mechanism of vibration damping and the cause of clamping stagnation have not been well resolved. This paper uses the analytical method, numerical method, and finite element method to analyze the vertical dynamic characteristics of the simple suspension system with dry friction and demonstrates that the numerical method is an effective method to study the dry model. The conditions for the system to produce sticking events were analyzed by the numerical method. The analysis shows that the system's excitation is too small, which causes clamping stagnation to the system. The reduction of the wedge angle and the friction coefficient are conducive to eliminating sticking. A negative side frame angle is conducive to reducing the high-frequency energy of the excitation. Decreasing spring stiffness or increasing system mass to reduce system frequency can reduce sticking events. The mutual verification of different methods confirms the correctness of the analysis method and analyzes the cause of sticking or clamping stagnation from the mechanism, which provides a new idea for the design and improvement of the dry friction damping system of railway vehicle bogies.

Aerodynamic Excitation Analysis of Radial Turbine Blades due to Unsteady Flow From Vaneless Turbine Housings

2017 ◽  
Author(s):  
Stephan Netzhammer ◽  
Damian M. Vogt ◽  
Stephan Kraetschmer ◽  
Johannes Leweux ◽  
Andreas Koengeter
Keyword(s):  
Test Data ◽  
Turbine Blades ◽  
Resonant Excitation ◽  
Design Parameters ◽  
Blade Vibration ◽  
Baseline Design ◽  
Housing Design ◽  
Radial Turbine ◽  
Turbine Housing ◽  
Generalized Force

Turbocharger turbine blades are subjected to resonant excitation that can lead to High Cycle Fatigue (HCF). In vaneless turbines the excitation primarily stems from asymmetries in the turbine housing such as the volute and the tongue. Given the nature of such asymmetries, the excitation is of a Low Engine Order (LEO) type. The present study deals with the effect of radial turbine housing design on LEO resonant excitation of turbine blades. The study focuses on two geometrical key design parameters of a twin-scroll turbine housing for a radial turbine which is the rotor-tongue distance and the circumferential angle between both tongues. The generalized force approach is used to identify the critical blade surface regions in order to understand the excitation mechanism of each specific design and to assess the differences of design variants with respect to the baseline design. The presented approach is highly practicable, because it is less expensive than full FSI-simulations. This approach is validated on tip timing test data from full-scale experiments. Correlation to test data shows that the presented approach is capable of capturing the relative trends reliably and hence can efficiently be employed in an industrial design process such as to minimize blade vibration amplitudes. It is shown that a reduction of blade vibration amplitudes by a factor of 10 could be achieved.

Twin Shaft Rotor System Vibration Damping Experimental Investigation

2015 ◽  
Vol 752-753 ◽  
pp. 918-921
Author(s):  
M.Sh. Nikhamkin ◽  
S.V. Semenov ◽  
G.V. Mekhonoshin ◽  
I.V. Semenova ◽  
N.A. Sazhenkov
Keyword(s):  
Experimental Investigation ◽  
Model Test ◽  
Dry Friction ◽  
Coulomb Friction ◽  
Vibration Damping ◽  
Friction Damper ◽  
Test Rig ◽  
Rotor Shaft ◽  
System Vibration ◽  
Dry Friction Damping

The influence of dry friction damping on twin shaft model test rig vibration experimental investigation is presented. Experimental investigation method is devised and tested at the work. Dry and Coulomb friction damper is developed. The efficiency of damping is evaluated quantitatively via rotor shaft vibration displacements amplitude determining.

Study of Characteristics of Dry Friction Damping.

1985 ◽  
Author(s):  
A. V. Srinivasan ◽  
B. N. Cassenti ◽  
D. G. Cutts
Keyword(s):  
Dry Friction ◽  
Friction Damping ◽  
Dry Friction Damping

scholarly journals A proposal to determine the distribution of lateral forces from loaded recycled plastic drainage kerbs

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Fin O’Flaherty ◽  
Fathi Al-Shawi
Keyword(s):  
Laboratory Test ◽  
Detailed Analysis ◽  
Test Data ◽  
Lateral Force ◽  
Measuring Device ◽  
Test Methodology ◽  
Lateral Forces ◽  
Test Conditions ◽  
Fit For Purpose ◽  
Construction Product

AbstractThis study presents a detailed analysis of the lateral forces generated as a result of vertically applied loads to recycled plastic drainage kerbs. These kerbs are a relatively new addition to road infrastructure projects. When concrete is used to form road drainage kerbs, its deformation is minimum when stressed under heavy axle loads. Although recycled plastic kerbs are more environmentally friendly as a construction product, they are less stiff than concrete and tend to deform more under loading leading to a bursting type, lateral force being applied to the haunch materials, the magnitude of which is unknown. A method is proposed for establishing the distribution of these lateral forces resulting from deformation under laboratory test conditions. A load of 400 kN is applied onto a total of six typical kerbs in the laboratory in accordance with the test standard. The drainage kerbs are surrounded with 150 mm of concrete to the front and rear haunch and underneath as is normal during installation. The lateral forces exerted on the concrete surround as a result of deformation of the plastic kerbs are determined via a strain measuring device. Analysis of the test data allows the magnitude of the lateral forces to the surrounding media to be determined and, thereby, ensuring the haunch materials are not over-stressed as a result. The proposed test methodology and subsequent analysis allows for an important laboratory-based assessment of any typical recycled plastic drainage kerbs to be conducted to ensure they are fit-for-purpose in the field.

scholarly journals Opportunistic Large Array Propagation Models: A Comprehensive Survey

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4206
Author(s):  
Farhan Nawaz ◽  
Hemant Kumar ◽  
Syed Ali Hassan ◽  
Haejoon Jung
Keyword(s):  
Energy Efficient ◽  
Large Scale ◽  
Performance Metrics ◽  
Experimental Studies ◽  
Cooperative Transmission ◽  
Analytical Models ◽  
Future Research ◽  
Large Array ◽  
Propagation Models ◽  
Comprehensive Survey

Enabled by the fifth-generation (5G) and beyond 5G communications, large-scale deployments of Internet-of-Things (IoT) networks are expected in various application fields to handle massive machine-type communication (mMTC) services. Device-to-device (D2D) communications can be an effective solution in massive IoT networks to overcome the inherent hardware limitations of small devices. In such D2D scenarios, given that a receiver can benefit from the signal-to-noise-ratio (SNR) advantage through diversity and array gains, cooperative transmission (CT) can be employed, so that multiple IoT nodes can create a virtual antenna array. In particular, Opportunistic Large Array (OLA), which is one type of CT technique, is known to provide fast, energy-efficient, and reliable broadcasting and unicasting without prior coordination, which can be exploited in future mMTC applications. However, OLA-based protocol design and operation are subject to network models to characterize the propagation behavior and evaluate the performance. Further, it has been shown through some experimental studies that the most widely-used model in prior studies on OLA is not accurate for networks with networks with low node density. Therefore, stochastic models using quasi-stationary Markov chain are introduced, which are more complex but more exact to estimate the key performance metrics of the OLA transmissions in practice. Considering the fact that such propagation models should be selected carefully depending on system parameters such as network topology and channel environments, we provide a comprehensive survey on the analytical models and framework of the OLA propagation in the literature, which is not available in the existing survey papers on OLA protocols. In addition, we introduce energy-efficient OLA techniques, which are of paramount importance in energy-limited IoT networks. Furthermore, we discuss future research directions to combine OLA with emerging technologies.

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