Research of dynamic characteristics of start-up of electric driving gas-distributing units

AbstractA low cost, light weight, high performance composite material turbomachinery impeller with a uniquely designed blade patterns is analyzed. Such impellers can economically enable refrigeration plants to use water as a refrigerant (R718). A strength and dynamic characteristics analyses procedure is developed to assess the maximum stresses and natural frequencies of these wound composite axial impellers under operating loading conditions. Numerical simulation using FEM for two-dimensional and three-dimensional impellers was investigated. A commercially available software ANSYS is used for the finite element calculations. Analysis is done for different blade geometries and then suggestions are made for optimum design parameters. In order to avoid operating at resonance, which can make impellers suffer a significant reduction in the design life, the designer must calculate the natural frequency and modal shape of the impeller to analyze the dynamic characteristics. The results show that using composite Kevlar fiber/epoxy matrix enables the impeller to run at high tip speed and withstand the stresses, no critical speed will be matched during start-up and shut-down, and that mass imbalances of the impeller shall not pose a critical problem.

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Experimental Analyses of a First Generation Foil Bearing: Start-Up Torque and Dynamic Coefficients

Volume 6: Structures and Dynamics, Parts A and B ◽

10.1115/gt2010-22966 ◽

2010 ◽

Cited By ~ 2

Author(s):

Laurent Rudloff ◽

Mihai Arghir ◽

Olivier Bonneau ◽

Pierre Matta

Keyword(s):

Dynamic Characteristics ◽

Static Load ◽

Excitation Frequency ◽

Base Plate ◽

Test Rig ◽

Dynamic Coefficients ◽

Foil Bearing ◽

Start Up ◽

Lift Off ◽

Stiffness And Damping

The paper presents the results of the experimental analysis of static and dynamic characteristics of a generation 1 foil bearing of 38.1 mm diameter and L/D = 1. The test rig is of floating bearing type, the rigid shaft being mounted on ceramic ball bearings and driven up to 40 krpm. Two different casings are used for start-up and for measurement of dynamic coefficients. In its first configuration, the test rig is designed to measure the start-up torque. The foil bearing casing is made of two rings separated by a needle bearing for enabling an almost torque free rotation between the foil bearing and the static load. The basic results are the start up torque and the lift off speed. In its second configuration a different casing is used for measuring the impedances of the foil bearing. Misalignment is a problem that is minimized by using three flexible stingers connecting the foil bearing casing to the base plate of the test rig. The test rig enables the application of a static load and of the dynamic excitation on the journal bearing casing, and can measure displacements, forces and accelerations. Working conditions consisted of static loads comprised between 10 N and 50 N and rotation frequencies ranging from 260 Hz to 590 HZ. Excitation frequencies comprised between 100 Hz are 600 Hz are applied by two orthogonally mounted shakers for each working condition. Stiffness and damping coefficients are identified from the complex impedances and enable the calculation of natural frequencies. The experimental results show that the dynamic characteristics of the tested bearing have a weak dependence on the rotation speed but vary with the excitation frequency.

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РЕКОМЕНДАЦИИ ПО ПРОЕКТИРОВАНИЮ ГИДРОСТАТОДИНАМИЧЕСКИХ ПОДШИПНИКОВ СКОЛЬЖЕНИЯ СДВОЕННОГО ТИПА

Aerospace technic and technology ◽

10.32620/aktt.2020.8.13 ◽

2020 ◽

pp. 100-105

Author(s):

Владимир Иосифович Назин

Keyword(s):

Dynamic Characteristics ◽

Fluid Layer ◽

High Reliability ◽

Experimental Studies ◽

Working Fluid ◽

Stable Operation ◽

Static And Dynamic Characteristics ◽

Start Up ◽

Bearing Materials

The task is to develop recommendations for the design of dual-type hydrostatodynamic plain bearings based on the existing experience in designing this type of plain bearings, as well as based on many theoretical and experimental studies performed by the author of this work. The number of the most necessary parameters for the design of dual-type hydrostatodynamic bearings is determined. Particular attention was paid to the development of recommendations for additional parameters specific to the design of double type plain bearings. Attention is paid to the selection of double-type bearing materials and it is shown that the problem of selecting materials for hydrostatic dynamic bearings is not so relevant, however, sometimes in start-up and shutdown modes, as well as in emergencies, to ensure high reliability of the designed machine, it is necessary to pay attention to the choice of bearing materials. The influence of various forms of chambers on the static and dynamic characteristics of hydrostatodynamic bearings is analyzed and it is shown that the greatest distribution in practice, they got rectangular cameras. It is shown that the flow regime of the working fluid also significantly affects both the static and dynamic characteristics of the bearing. It is noted that even with a non-rotating rotor in a hydrostatodynamic bearing, the most turbulent mode of flow of the working fluid is most often observed. The influence of the thickness of the working fluid layer on increasing the rigidity of the supports and expanding the range of stable operation is considered. It is shown that with a decrease in the clearance in the bearing, its bearing capacity increases and the range of stable operation expands, however, this increases the friction power loss, increases the likelihood of clogging of the slit bearing path, and also increases the requirements for the quality of manufacture of the bearing working surfaces. It is recommended that in the double hydrostatodynamic bearing in the outer and inner parts to assign the same clearances. It is shown that in a dual hydrostatodinamic bearing, the existing recommendation on the number of chambers can lead in some cases to large working fluid flow.

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Experimental Analysis of the Dynamic Characteristics of a Foil Thrust Bearing

Volume 7B: Structures and Dynamics ◽

10.1115/gt2014-25550 ◽

2014 ◽

Cited By ~ 1

Author(s):

Franck Balducchi ◽

Mihai Arghir ◽

Romain Gauthier

Keyword(s):

Dynamic Characteristics ◽

Experimental Analysis ◽

Dynamic Models ◽

Thrust Bearing ◽

Dynamic Stiffness ◽

Excitation Frequency ◽

Test Rig ◽

Equivalent Damping ◽

Start Up ◽

Foil Thrust Bearing

The paper deals with the experimental analysis of the dynamic characteristics of a foil thrust bearing (FTB) designed following the specifications given by NASA in 2009. The start-up characteristics of the same foil bearing were investigated in a recently published paper. The test rig used for start-up measurements was adapted for dynamic measurements. The paper presents the test rig in detail as well as its identified dynamic models. Measurements of the dynamic characteristics of the bump foil structure were performed for static loads comprised between 30 N and 150 N while measurements for the FTB were performed at 35 krpm for 30 N, 60 N and 90 N. Excitation frequencies were comprised between 150 Hz and 750 Hz. Results showed that the dynamic stiffness of the FTB increase with excitation frequency while the equivalent damping decreases. Both stiffness and damping increase with the static load but are smaller at 35 krpm compared to 0 rpm.

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Refrigerant Charge Prediction of Vapor Compression Air Conditioner Based on Start-Up Characteristics

Applied Sciences ◽

10.3390/app11041780 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1780

Author(s):

Yechan Yun ◽

Young Soo Chang

Keyword(s):

Experimental Data ◽

Steady State ◽

Test Data ◽

Dynamic Characteristics ◽

Dynamic Models ◽

Prediction Models ◽

Support Vector ◽

Condensation Temperature ◽

Discharge Temperature ◽

Start Up

Refrigerant charge faults, which occur frequently, increase the energy loss and may fatally damage the system. Refrigerant leakage is difficult to detect and diagnose until the fault has reached a severe degree. Various techniques have been developed to predict the refrigerant charge amount based on steady-state operation; however, steady-state experiments used to develop prediction models for the refrigerant charge amount are expensive and time-consuming. In this study, a prediction model was established with dynamic experimental data to overcome these deficiencies. The dynamic models for the condensation temperature, degree of subcooling, compressor discharge temperature, and power consumption were developed with a regression support vector machine (r-SVM) model and start-up experimental data. The dynamic models for the condensation temperature and degree of subcooling can predict the distinct start-up characteristics depending on the refrigerant charge amount. Moreover, the estimated root mean square error (RMSE) of the condensation temperature and degree of subcooling of the test data are 0.53 and 0.84 °C, respectively. The refrigerant charge is one of the predictors that defines the dynamic characteristics. The refrigerant charge can be estimated by minimizing the RMSE of the predicted values of the dynamic models and experimental data. When the dynamic characteristics of the two predictor variables, “condensation temperature” and “degree of subcooling” are used together, the average prediction error of the test data is 2.54%. The proposed method, which uses the dynamic model during start-up operation, is an effective technique for predicting the refrigerant charge amount.

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Experimental Analysis of the Dynamic Characteristics of a Foil Thrust Bearing

Journal of Tribology ◽

10.1115/1.4029643 ◽

2015 ◽

Vol 137 (2) ◽

Cited By ~ 4

Author(s):

Franck Balducchi ◽

Mihai Arghir ◽

Romain Gauthier

Keyword(s):

Dynamic Characteristics ◽

Experimental Analysis ◽

Gas Turbines ◽

Thrust Bearing ◽

Dynamic Stiffness ◽

Excitation Frequency ◽

Equivalent Damping ◽

Start Up ◽

And Performance ◽

Foil Thrust Bearing

This paper deals with the experimental analysis of the dynamic characteristics of a foil thrust bearing (FTB) designed according to specifications given by NASA scientists in 2009 (Dykas et al., 2009, “Design, Fabrication, and Performance of Foil Gas Thrust Bearings for Microturbomachinery Applications,” ASME J. Eng. Gas Turbines Power, 131(1), p. 012301). The present work details the new configuration of the same test rig that was used to test start-up characteristics of the aforementioned bearing (Balducchi et al., 2013, “Experimental Analysis of the Start-Up Torque of a Mildly Loaded Foil Thrust Bearing,” ASME J. Tribol., 135(3), p. 031703). The rig has been reconfigured to test dynamic characteristics. The dynamic characteristics of the bump foil structure were measured for static loads comprised between 30 N and 150 N while measurements for the FTB were performed at 35 krpm for 30 N, 60 N, and 90 N. Excitation frequencies were comprised between 150 Hz and 750 Hz. Results showed that the dynamic stiffness of the FTB increase with excitation frequency while the equivalent damping decreases. Both stiffness and damping increase with the static load but are smaller at 35 krpm compared to 0 rpm.

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