Bearings Influence on the Dynamic Behavior of HSM Spindle

2012 ◽  
Author(s):  
David Noel ◽  
Mathieu Ritou ◽  
Sebastien Le Loch ◽  
Benoit Furet
Keyword(s):  
Dynamic Behavior ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Experimental Tests ◽  
Operating Conditions ◽  
Design Parameters ◽  
Mechanics Model ◽  
Bearing Stiffness ◽  
Rough Milling ◽  
The Impact

The aeronautic industry requires high speed and high power spindles to obtain high material removal rates during long rough milling operations. The weakness of HSM spindle is the bearings, although high precision hybrid ball bearings have been developed to achieve this critical application. Inadequate use of spindles inevitably leads to shortened lifetimes. Choosing the operating conditions is a required step before machining applications. It can be achieved through either experimental tests or numerical modeling that leads to stability lobe diagrams. Stability of cuts relies on the dynamic behavior of the spindle, which is particularly due to the eigenfrequencies of the tool-shaft assembly. The frequencies depend on bearing stiffness that can change under operating conditions. That is why the impact of cutting conditions and bearing parameters on its stiffness are studied in the paper. A five degrees of freedom model of angular ball bearing is briefly presented. A complete bearing model is introduced. The originality of the approach is the complete technological modeling, notably of the radial expansions of inner and outer rings of bearing. A non-linear expression is established from continuum mechanics model. The influence of geometry of bearing, operating conditions and design parameters of spindle on the bearing stiffness are established and analysed. Then, modal analyses of the tool-spindle assembly are carried out in relation to the varying bearing stiffness. Finally, significance of the approach is demonstrated through the analyses of Frequency Response Function.

scholarly journals Dynamic Analysis of Noncontacting Face Seals

1982 ◽  
Vol 104 (4) ◽  
pp. 460-468 ◽  
Author(s):  
I. Etsion
Keyword(s):  
Dynamic Behavior ◽  
Degrees Of Freedom ◽  
Approximate Expression ◽  
Operating Conditions ◽  
Design Parameters ◽  
Seal Ring ◽  
Critical Stability ◽  
Dimensionless Groups ◽  
Stability Maps ◽  
Metal Bellows

The dynamic behavior of a noncontacting coned face seal is analyzed for the case of a rigidly mounted rotating seat and a flexibly mounted stationary ring taking into account various design parameters and operating conditions. The primary seal ring motion is expressed by a set of nonlinear equations for three degrees of freedom. These equations, which are solved numerically, allow identification of two dimensionless groups of parameters that affect the seal dynamic behavior. Stability maps for various seals are presented. These maps contain a stable-to-unstable transition region in which the ring wobbles at half the shaft frequency. The effect of various parameters on seal stability is discussed and an approximate expression for critical stability is offered. The theoretical model assumes frictionless flexible mounting of the seal ring such as in metal bellows. However, the results for critical stability can also be used as an upper limit for cases when friction in the secondary seal is present.

scholarly journals The processes of vaporization in the porous structures working with the excess of liquid

2017 ◽  
Vol 21 (1 Part A) ◽  
pp. 363-373 ◽  
Author(s):  
Alexander Genbach ◽  
Nellya Jamankulova ◽  
Vukman Bakic
Keyword(s):  
Temperature Difference ◽  
High Speed ◽  
Power Plants ◽  
Cooling System ◽  
Thermal Power ◽  
Laser System ◽  
Operating Conditions ◽  
Design Parameters ◽  
Porous Structures ◽  
The Impact

The processes of vaporization in porous structures, working with the excess of liquid are investigated. With regard to the thermal power plants new porous cooling system is proposed and investigated, in which the supply of coolant is conducted by the combined action of gravity and capillary forces. The cooling surface is made of stainless steel, brass, copper, bronze, nickel, alundum and glass, with wall thickness of (0.05-2)?10-3 m. Visualizations of the processes of vaporization were carried out using holographic interferometry with the laser system and high speed camera. The operating conditions of the experiments were: water pressures (0.01-10) MPa, the temperature difference of sub-cooling (0-20)?C, an excess of liquid (1-14) of the steam flow, the heat load (1-60)?104 W/m2, the temperature difference (1-60)?C and orientation of the system (? 0 - ? 90) degrees. Studies have revealed three areas of liquid vaporization process (transitional, developed and crisis). The impact of operating and design parameters on the integrated and thermal hydraulic characteristics was defined. The optimum (minimum) flow rate of cooling fluid and the most effective type of mesh porous structure were also defined.

Impact of Operating Conditions and Design Parameters on Gas Turbine Hot Section Creep Life

2010 ◽  
Author(s):  
S. Eshati ◽  
M. F. Abdul Ghafir ◽  
P. Laskaridis ◽  
Y. G. Li
Keyword(s):  
Gas Turbines ◽  
Performance Model ◽  
Operating Conditions ◽  
Creep Model ◽  
Design Parameters ◽  
Gas Temperature ◽  
Creep Life ◽  
Cooling Effectiveness ◽  
Radial Temperature ◽  
The Impact

This paper investigates the relationship between design parameters and creep life consumption of stationary gas turbines using a physics based life model. A representative thermodynamic performance model is used to simulate engine performance. The output from the performance model is used as an input to the physics based model. The model consists of blade sizing model which sizes the HPT blade using the constant nozzle method, mechanical stress model which performs the stress analysis, thermal model which performs thermal analysis by considering the radial distribution of gas temperature, and creep model which using the Larson-miller parameter to calculate the lowest blade creep life. The effect of different parameters including radial temperature distortion factor (RTDF), material properties, cooling effectiveness and turbine entry temperatures (TET) is investigated. The results show that different design parameter combined with a change in operating conditions can significantly affect the creep life of the HPT blade and the location along the span of the blade where the failure could occur. Using lower RTDF the lowest creep life is located at the lower section of the span, whereas at higher RTDF the lowest creep life is located at the upper side of the span. It also shows that at different cooling effectiveness and TET for both materials the lowest blade creep life is located between the mid and the tip of the span. The physics based model was found to be simple and useful tool to investigate the impact of the above parameters on creep life.

Development of an End-Effector for Mitigation of Collisions

2021 ◽  
Author(s):  
Domenico Tommasino ◽  
Matteo Bottin ◽  
Giulio Cipriani ◽  
Alberto Doria ◽  
Giulio Rosati
Keyword(s):  
Numerical Simulations ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Contact Forces ◽  
Design Parameters ◽  
End Effector ◽  
Linear Behavior ◽  
Stable Mechanism ◽  
Robot Tasks ◽  
The Impact

Abstract In robotics the risk of collisions is present both in industrial applications and in remote handling. If a collision occurs, the impact may damage both the robot and external equipment, which may result in successive imprecise robot tasks or line stops, reducing robot efficiency. As a result, appropriate collision avoidance algorithms should be used or, if it is not possible, the robot must be able to react to impacts reducing the contact forces. For this purpose, this paper focuses on the development of a special end-effector that can withstand impacts and is able to protect the robot from impulsive forces. The novel end-effector is based on a bi-stable mechanism that decouples the dynamics of the end-effector from the dynamics of the robot. The intrinsically non-linear behavior of the end-effector is investigated with the aid of numerical simulations. The effect of design parameters and the operating conditions are analyzed and the interaction between the functioning of the bi-stable mechanism and the control system is studied. In particular, the effect of the mechanism in different scenarios characterized by different robot velocities is shown. Results of numerical simulations assess the validity of the proposed end-effector, which can lead to large reductions in impact forces.

Direct Outer Ring Cooling of a High Speed Jet Engine Mainshaft Ball Bearing: Experimental Investigation Results

2010 ◽  
Author(s):  
Peter Gloeckner ◽  
Klaus Dullenkopf ◽  
Michael Flouros
Keyword(s):  
Power Dissipation ◽  
High Speed ◽  
Ball Bearing ◽  
Operating Conditions ◽  
Outer Ring ◽  
Outer Diameter ◽  
Propulsion Systems ◽  
Jet Engine ◽  
Power Loss Reduction ◽  
The Impact

Operating conditions in high speed mainshaft ball bearings applied in new aircraft propulsion systems require enhanced bearing designs and materials. Rotational speeds, loads, demands on higher thrust capability, and reliability have increased continuously over the last years. A consequence of these increasing operating conditions are increased bearing temperatures. A state of the art jet engine high speed ball bearing has been modified with an oil channel in the outer diameter of the bearing. This oil channel provides direct cooling of the outer ring. Rig testing under typical flight conditions has been performed to investigate the cooling efficiency of the outer ring oil channel. In this paper the experimental results including bearing temperature distribution, power dissipation, bearing oil pumping and the impact on oil mass and parasitic power loss reduction are presented.

scholarly journals Influence of the main operating parameters on the DRPSA process design based on the equilibrium theory

Adsorption ◽  
2020 ◽  
Author(s):  
Ester Rossi ◽  
Giuseppe Storti ◽  
Renato Rota
Keyword(s):  
Pressure Swing Adsorption ◽  
Degrees Of Freedom ◽  
Pressure Ratio ◽  
Complete Separation ◽  
Operating Conditions ◽  
Equilibrium Theory ◽  
Design Parameters ◽  
Reflux Ratio ◽  
Gaseous Mixtures ◽  
Pressure Swing

Abstract Among the adsorption-based separation processes for gaseous mixtures, those exploiting pressure variations, so-called Pressure Swing Adsorption (PSA) processes, are the most popular. In this work, we focus on the specific PSA configuration known as Dual Reflux-Pressure Swing Adsorption (DR-PSA) given its ability to achieve sharp separations. In the case of binary mixtures, an analytical approach based on Equilibrium Theory has been proposed to identify the operating conditions for complete separation under the assumption of linear isotherms. This same approach is not available when the separation is not complete. Accordingly, in this work we study the features of non-complete separations by solving numerically a general DR-PSA model with parameter values suitable to approach equilibrium conditions (no mass transport resistances, no axial mixing, isothermal conditions and no pressure drop), thus reproducing the analytical solution when complete separations are examined. Even for non-complete separations, triangularly shaped regions at constant purity can be identified on a plane whose axes correspond to suitable design parameters. Moreover, we found a general indication on how to select the lateral feed injection position to limit the loss in product purities when complete separation is not established, whatever is the composition of the feeding mixture. Finally, a sensitivity analysis with respect to pressure ratio, light reflux ratio and heavy product flowrate is proposed in order to assess how to recover product purities according to the specific degrees of freedom of a DR-PSA apparatus.

Impact of Impeller Casing Treatment on the Acoustics of a Small High Speed Centrifugal Compressor

2018 ◽  
Author(s):  
Sidharath Sharma ◽  
Jorge García-Tíscar ◽  
John M. Allport ◽  
Martyn L. Jupp ◽  
Ambrose K. Nickson
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Operating Conditions ◽  
Aerodynamic Noise ◽  
Noise Sources ◽  
Casing Treatment ◽  
Active Research ◽  
Ported Shroud ◽  
The Impact

Ported shroud casing treatment is widely used to delay the onset of surge and thereby enhancing the aerodynamic stability of a centrifugal compressor by recirculating the low momentum fluid in the blade passage. Performance losses associated with the use of recirculation casing treatment are well established in the literature and this is an area of active research. The other, less researched aspect of the casing treatment is its impact on the acoustics of the compressor. This work investigates the impact of ported shroud casing treatment on the acoustic characteristics of the compressor. The flow in two compressor configurations viz. with and without casing treatment operating at the design operating conditions of an iso-speed line are numerically modelled and validated with experimental data from gas stand measurements. The pressure fluctuations calculated as the flow solution are used to compute the spectral signatures at multiple locations to investigate the acoustic phenomenon associated with each configuration. Propagation of the frequency content through the ducts has been estimated with the aid of method of characteristics to enhance the content coming from the compressor. Expected tonal aerodynamic noise sources such as monopole (buzz-saw tones) and dipole (Blade Pass Frequency) are clearly identified in the acoustic spectra of the two configurations. The comparison of two configurations shows higher overall levels and tonal content in the case of a compressor with ported shroud operating at design conditions due to the presence of ‘mid-tones’.

Experimental Study of the Effect of Water Spray in the Air on Thermal Transfers Along a Plate of an Exchanger

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Nihel Grich ◽  
Walid Foudhil ◽  
Souad Harmand ◽  
Sadok Ben Jabrallah
Keyword(s):  
Salt Water ◽  
Experimental Tests ◽  
Operating Conditions ◽  
Heated Plate ◽  
Environment Effect ◽  
Single Plate ◽  
Salt Layer ◽  
Turbulent Airflow ◽  
Heat Transfers ◽  
The Impact

Abstract This study is an experimental investigation of the oceanic environment effect on a plate heat exchanger performance. Indeed, an experiment was carried out on a single plate of the exchanger to generate a turbulent airflow in which fine water droplets were injected into a horizontal vein where a heated plate was placed. The experimental tests were conducted for different air velocities and various water concentrations of freshwater and saltwater. In fact, two plate forms were considered: The first one is flat while the second is corrugated. Three main facts were observed in this work: (i) the correlations linking the heat transfer rate to the operating conditions, (ii) the effect of fog addition and the plate form on convective heat transfers, and (iii) the impact of the formation of a salt layer on the surface of the plate in the case of salt water.

The Impact of Modelling Air Compressibility in the Selection of Optimal OWC Design Parameters in Site Specific Wave Conditions

2019 ◽  
Author(s):  
Irene Simonetti ◽  
Lorenzo Cappietti
Keyword(s):  
Fluid Dynamic ◽  
Experimental Tests ◽  
Design Parameters ◽  
Dynamic Simulations ◽  
Regression Approach ◽  
Wave Conditions ◽  
A Site ◽  
The Impact ◽  
Period Wave ◽  
Selection Of

Abstract The importance of properly modelling the effects of air compressibility in the selection of the optimal design parameters for an Oscillating Water Column wave energy converter is investigated. For this purpose, a wide dataset of capture width ratios, obtained from both experimental tests and Computational Fluid Dynamic simulations, is used to formulate an empirical model able to predict the performance of the device as a function of its basic design parameters (chamber width and draught, turbine damping) and of the wave conditions (wave period, wave height). A multiple non-linear regression approach is used to determine the model numerical coefficients. The data used to formulate the model include the effects of air compressibility. The impact of considering such effects on the selection of the optimal geometry of the device is evaluated and discussed by means of the model application for the optimization of a device to be installed in a site located in the Mediterranean Sea (in front of the coast of Tuscany, Italy).

Modeling of a New Crank-Less Rotary Heat Engine Concept for Solar Power Utilization

2018 ◽  
Author(s):  
Muhammad I. Rashad ◽  
Hend A. Faiad ◽  
Mahmoud Elzouka
Keyword(s):  
Degrees Of Freedom ◽  
Unit Cost ◽  
Heat Engine ◽  
Structure Design ◽  
Operating Conditions ◽  
Design Parameters ◽  
Working Fluid ◽  
Heat Engines ◽  
And Performance ◽  
Engine Concept

This paper presents the operating principle of a novel solar rotary crank-less heat engine. The proposed engine concept uses air as working fluid. The reciprocating motion is converted to a rotary motion by the mean of unbalanced mass and Coriolis effect, instead of a crank shaft. This facilitates the engine scaling and provides several degrees of freedom in terms of structure design and configuration. Unlike classical heat engines (i.e. Stirling), the proposed engine can be fixed to the ground which significantly reduce the generation unit cost. Firstly, the engine’s configuration is illustrated. Then, order analysis for the engine is carried out. The combined dynamics and thermal model is developed using ordinary differential equations which are then numerically solved by Simulink™. The resulting engine thermodynamics cycle is described. It incorporates the common thermodynamics processes (isobaric, isothermal, isochoric processes). Finally, the system behavior and performance are analyzed along with studying the effect of various design parameters on operating conditions such as engine speed, output power and efficiency.

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