Rotordynamic Performance of Shimmed Gas Foil Bearings for Oil-Free Turbochargers

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Kyuho Sim ◽  
Lee Yong-Bok ◽  
Tae Ho Kim ◽  
Jangwon Lee
Keyword(s):  
Diesel Engine ◽  
Test Data ◽  
Compressed Air ◽  
Radial Clearance ◽  
Bench Test ◽  
Test Results ◽  
Passenger Vehicle ◽  
Performance Measurements ◽  
Foil Bearings ◽  
Model Predictions

Oil-free turbochargers (TCs) will increase the power and efficiency of internal combustion engines, both sparking ignition and compression ignition, without engine oil lubricant feeding or scheduled maintenance. Using gas foil bearings (GFBs) in passenger vehicle TCs enables compact, lightweight, oil-free systems, along with accurate shaft motion. This paper presents extensive test measurements on GFBs for oil-free TCs, including static load-deflection measurements of test GFBs, rotordynamic performance measurements of a compressed air driven oil-free TC unit supported on test GFBs, and bench test measurements of the oil-free TC driven by a passenger vehicle diesel engine. Two configurations of GFBs, one original and the other modified with three shims, are subjected to a series of experimental tests. For the shimmed GFB, three metal shims are inserted under the bump-strip layers, in contact with the bearing housing. The installation of shims creates mechanical preloads that enhance a hydrodynamic wedge in the assembly radial clearance to generate more film pressure. Simple static load-deflection tests estimate the assembly radial clearance of the shimmed GFB, which is smaller than that of the original GFB. Model predictions agree well with test data. The discrepancy between the model predictions and test data is attributed to fabrication inaccuracy in the top foil and bump strip layers. Test GFBs are installed into a TC test rig driven by compressed air for rotordynamic performance measurements. The test TC rotor, 335 g in weight and 117 mm long, is coated with a commercially available, wear-resistant solid lubricant, Amorphous M, to prevent severe wear during start-up and shutdown in the absence of an air film. A pair of optical proximity probes positioned orthogonally at the compressor end record lateral rotor motions. Rotordynamic test results show that the shimmed GFB significantly diminishes the large amplitude of subsynchronous rotor motions arising in the unmodified GFB. Predicted synchronous rotor amplitudes and rigid body mode natural frequencies agree reasonably well with recorded test data. Finally, the oil-free TC is installed into a passenger vehicle diesel engine test bench. The TC rotor speed is controlled by the vehicle engine. Speed-up tests show dominant synchronous motion (1X) of the rotor. Whirl frequencies of the relatively small subsynchronous motions are associated with the rigid body natural mode of the TC rotor-GFB system as well as (forced) excitation from the four-cylinder diesel engine. The bench test measurements demonstrate a significant reduction in the amplitude of subsynchronous motions for the shimmed GFB, thus verifying the preliminary test results in the TC test rig driven by compressed air.

Rotordynamic Performance of an Oil-Free Turbocharger Supported on Gas Foil Bearings: Effects of an Assembly Radial Clearance

2010 ◽  
Author(s):  
Tae Ho Kim ◽  
Jangwon Lee ◽  
Chang Ho Kim ◽  
Yong-Bok Lee
Keyword(s):  
Test Data ◽  
Static Load ◽  
Pressure Sensors ◽  
Engine Oil ◽  
Radial Clearance ◽  
Performance Measurements ◽  
Film Pressure ◽  
Foil Bearings ◽  
Wide Range ◽  
Model Predictions

Oil-free turbochargers (TCs) will increase power and efficiency of internal combustion (IC) engines, sparking ignition (SI) and compression ignition (CI), without engine oil lubricant feeding and scheduled maintenance. Implementing gas foil bearings (GFBs) into passenger vehicle TCs enables compact, light weight, oil-free systems along with accurate shaft motions, while engine oil lubricated TCs with floating ring bearings (FRBs) are prone to show severe sub synchronous motions over a wide range of shaft speeds due to instability. The paper presents static load-deflection tests of TC GFB structure, and rotordynamic performance measurements of an oil-free TC unit supported on test GFBs. Three metal shims inserted under the bump-strip layers and in contact with the bearing housing create a mechanical preload, which induces a hydrodynamic wedge in the assembly radial clearance to generate more film pressure for the shimmed GFB. Static load-deflection tests estimate the assembly radial clearances of the shimmed GFB smaller than that of the original GFB. Model predictions agree well with test data. The discrepancy between the model predictions and test data is attributed to fabrication inaccuracy of the top foil and bump strip layers. The rotordynamic TC test rig is driven by pressurized air. The test TC rotor, of 335 gram weight and 117 mm length, is coated using commercially available wear-resistant solid lubricant, Amorphous M, to prevent severe wears during start up and shutdown in the absence of an air film. Pressure sensors measure the driving turbine inlet air pressure and a control valve changes the air mass flow manually. A pairs of optical proximity probes positioned orthogonally at the compressor end record the lateral rotor motions. Rotordynamic test results show that the shimmed GFB attenuates significantly the large amplitude of subsynchronous whirl motions arising for the original GFBs. Mechanical preloads, which determine the assembly radial clearance of the shimmed GFB, causes the increase in the rotor-bearing system natural frequency.

Rotordynamic Performance Measurements and Predictions of a Rotor Supported on Multilayer Gas Foil Journal Bearings for Microturbomachinery

2016 ◽  
Author(s):  
Jongsung Lee ◽  
Young Min Kim ◽  
Moon Sung Park ◽  
Tae Ho Kim ◽  
Kyoung Ku Ha ◽  
...  
Keyword(s):  
Damping Ratio ◽  
Operation Time ◽  
Journal Bearings ◽  
Displacement Sensor ◽  
Radial Clearance ◽  
Performance Measurements ◽  
Displacement Sensors ◽  
Model Predictions ◽  
Type C ◽  
Time Required

This paper presents rotordynamic performance measurements of multilayer gas foil journal bearings (GFJBs) supporting the rotor of oil-free microturbomachinery, and a comparison with the model predictions. A series of rotor coast-down tests from 60 krpm were conducted to compare the rotordynamic performances of three previously developed multilayer GFJBs: types A, B, and C. During the tests, two sets of orthogonally positioned displacement sensors recorded the horizontal and vertical rotor motions, and an axially positioned displacement sensor measured the thrust of the runner axial motion. The test results revealed that the type C GFJBs have a superior rotordynamic capability over the other types. The additional coast-down tests from 100 krpm for the type C showed that the synchronous motions of the rotor are dominant at up to ∼50 krpm, but that large amplitudes of subsynchronous motion associated with the natural frequency of a rotor-GFJB system occur above this speed. Thermal transient response measurements were conducted using four k-type thermocouples at increasing rotor speeds of 20 to 100 krpm with increments of 10 krpm. The operation time required to establish steady-state temperatures was approximately 25 min for each speed. For most of the speeds tested, the front GFJB near the rotor impeller end showed the lowest temperatures, and both the rear GFJB near the thrust runner end and the permanent magnet (PM) motor showed the highest temperatures. The GFTB showed the lowest temperature at low speeds of below 50 krpm, and the highest temperature at the top speed of 100 krpm owing to the increasing axial load caused by the impeller force. The measured impeller pressure and motor output power increased nonlinearly with the increasing rotor speed and fits best with the second-order and third-order polynomial equations, respectively. The measured axial displacement revealed that the rotor moved axially up to ∼ 270 μm toward the impeller side as the speed increased to 100 krpm. Further experiments using a decrease in radial clearance of 30 μm demonstrated a suppression of the large amplitude of the subsynchronous rotor motion to a certain degree. In addition, the onset speed of the subsynchronous motions increased to 80 krpm for the type C GFJBs with the decrease in the radial clearance. Rotordynamic model predictions with the predicted GFJB stiffness and damping coefficients were benchmarked against the test data. The predicted natural frequencies, onset speed of instability (OSI) where the damping ratio became negative, and synchronous rotor response versus speed agreed reasonably with the measured whirl frequencies of the subsynchronous motions, the onset speed of subsynchronous motions (OSS), and the filtered synchronous rotor motion versus speed, respectively. The predictions also showed that the OSI increased from 50 krpm to 80 krpm with a decrease in the radial clearance, thus validating the present rotordynamic model.

Effects of Mechanical Preloads on the Rotordynamic Performance of a Rotor Supported on Three-Pad Gas Foil Journal Bearings

2014 ◽  
Vol 136 (12) ◽  
Author(s):  
Kyuho Sim ◽  
Bonjin Koo ◽  
Jong Sung Lee ◽  
Tae Ho Kim
Keyword(s):  
Test Data ◽  
High Speed ◽  
Experimental Tests ◽  
Journal Bearings ◽  
Test Results ◽  
Performance Measurements ◽  
Displacement Sensors ◽  
Single Top ◽  
Speed Up ◽  
The One

This paper presents the rotordynamic performance measurements and model predictions of a rotor supported on three-pad gas foil journal bearings (GFJBs) with various mechanical preloads. The rotor with its length of 240 mm, diameter of 40 mm, and weight of 19.6 N is supported on two GFJBs and one pair of gas foil thrust bearings (GFTBs), being a permanent magnet rotor of a high speed electric motor. Each bearing pad consisting of a top foil and a bump-strip layer is installed on a lobed bearing housing surface over the arc length of 120 deg along the circumference. Test three-pad GFJBs have four different mechanical preloads, i.e., 0 μm, 50 μm, 70 μm, 100 μm with a common radial nominal clearance of 150 μm. A series of speed-up tests are conducted up to 93 krpm to evaluate the effects of increasing mechanical preloads on the rotordynamic performance. Two sets of orthogonally positioned displacement sensors record the rotor horizontal and vertical motions at the thrust collar and the other end. Test results show that the filtered synchronous amplitudes change little, but the onset speed of subsynchronous motions (OSS) increases dramatically for the increasing mechanical preloads. In addition, test bearings with the 100 μm preload show a higher OSS in load-on-pad (LOP) condition than that in load-between-pads (LBP) condition. A comparison with test results for a one-pad GFJB with a single top foil and bump-strip layer reveals that three-pad GFJB has superior rotordynamic performance to the one-pad one. Finally, the test data benchmark against linear rotordynamic predictions to validate a rotor-GFJB model. In general, predicted natural frequencies of the rotor-bearing system and synchronous rotor motions agree well with test data. However, stability analyses underestimate OSSs recorded during the experimental tests.

Test Comparison of Damping Effect for Engine Damper Based on Rubber and MR Fluid Damper

2013 ◽  
Vol 397-400 ◽  
pp. 581-584
Author(s):  
Chun Lan Liang ◽  
Jian Wei Ma ◽  
Fei Zha
Keyword(s):  
Comparative Analysis ◽  
Diesel Engine ◽  
Test Data ◽  
Bench Test ◽  
Mr Fluid ◽  
Damping Effect ◽  
Fluid Damper ◽  
Mr Fluid Damper ◽  
Rubber Damper

The damping effect of 485 diesel engine is taken as research object, on the same conditions, bench test is conducted respectively to self-developed MR fluid damper and traditional rubber damper, comparative analysis of domain and spectrum are conducted to collected test data using MATLAB, the results show that damping effect of MR fluid damper to engine is significantly superior to effect of traditional rubber damper.

Effects of Mechanical Preloads on the Rotordynamic Performance of a Rotor Supported on 3 Pad Gas Foil Journal Bearings

2014 ◽  
Author(s):  
Kyuho Sim ◽  
Bonjin Koo ◽  
Jong Sung Lee ◽  
Tae Ho Kim
Keyword(s):  
Test Data ◽  
High Speed ◽  
Experimental Tests ◽  
Journal Bearings ◽  
Test Results ◽  
Performance Measurements ◽  
Displacement Sensors ◽  
Single Top ◽  
Speed Up ◽  
The One

The paper presents the rotordynamic performance measurements and model predictions of a rotor supported on three-pad gas foil journal bearings (GFJBs) with various mechanical preloads. The rotor with its length of 240 mm, diameter of 40 mm, and weight of 19.6 N is supported on two GFJBs and one pair of gas foil thrust bearings (GFTBs), being a permanent magnet rotor of a high speed electric motor. Each bearing pad consisting of a top foil and a bump strip layer is installed on a lobed bearing housing surface over the arc length of 120 deg along the circumference. Test three-pad GFJBs have four different mechanical preloads, i.e., 0 μm, 50 μm, 70 μm, 100 μm with a common radial nominal clearance of 150 μm. A series of speed-up tests are conducted up to 93 krpm to evaluate the effects of increasing mechanical preloads on the rotordynamic performance. Two sets of orthogonally positioned displacement sensors record the rotor horizontal and vertical motions at the thrust collar and the other end. Test results show that the filtered synchronous amplitudes change little, but the onset speed of sub-synchronous motions (OSS) increases dramatically for the increasing mechanical preloads. In addition, test bearings with the 100 μm preload show a higher OSS in load-on-pad (LOP) condition than that in load-between-pads (LBP) condition. A comparison to test results for a one-pad GFJB with a single top foil and bump strip layer reveals that three-pad GFJB has superior rotordynamic performance to the one-pad one. Finally, the test data benchmark against linear rotordynamic predictions to validate a rotor-GFJB model. In general, predicted natural frequencies of the rotor-bearing system and synchronous rotor motions agree well with test data. However, stability analyses underestimate OSSs recorded during the experimental tests.

Pemberian Umpan Balik Dalam Meningkatkan Hasil Belajar dan Minat Belajar Mahasiswa

2015 ◽  
Vol 4 (3) ◽  
Author(s):  
Seruni Seruni ◽  
Nurul Hikmah
Keyword(s):  
Information Technology ◽  
Learning Outcomes ◽  
Test Data ◽  
Random Sampling ◽  
Covariance Matrices ◽  
Test Results ◽  
Immediate Feedback ◽  
Statistics Course ◽  
Independent Variable ◽  
Descriptive Statistical Analysis

<p>The purpose of this study is to find and analyze the effect of feedback on <br />learning outcomes in mathematics and an interest in basic statistics course. The <br />population in this study are affordable Information Technology Student cademic Year 2012/2013 Semester II Indraprasta PGRI University of South Jakarta. Sample The study sample was obtained through random sampling. This study used an experimental method to the analysis using the MANOVA test. This study has three variables, consisting of: one independent variable, namely the provision of feedback (immediate and delayed), and two dependent variable is the result of interest in the study of mathematics and basic statistics course. The data was collected for the test results to learn mathematics, and a questionnaire for the interest in basic statistics course. Collected data were analyzed using the MANOVA test. Before the data were analyzed, first performed descriptive statistical analysis and test data analysis requirements (test data normality and homogeneity of covariance matrices). The results show that the learning outcomes of interest in mathematics and basic statistics course for students who are given immediate feedback higher than students given feedback delayed. <br /><br /></p>

Feasibility investigation of a compressor rotor supported by gas foil bearings with inhomogeneous bump foils

2021 ◽  
pp. 135065012110046
Author(s):  
Hao Li ◽  
Haipeng Geng ◽  
Bo Wang ◽  
Wei Zheng
Keyword(s):  
Critical Speed ◽  
Rotor System ◽  
Experimental Result ◽  
Test Results ◽  
Rotating Speed ◽  
Foil Bearings ◽  
Dynamic Coefficients ◽  
High Order Harmonic ◽  
Compressor Rotor ◽  
Operating Points

In this paper, a rotordynamic experiment on a compressor rotor system is presented and the feasibility of gas foil bearings with inhomogeneous bump foils is verified. A push–pull device is designed to obtain the stiffness curve and the nominal clearance of foil bearings. Operating points and dynamic coefficients of the rotor system at each rotating speed are predicted. In rotordynamic analysis, an alternative model of the impeller is proposed and the critical speed is predicted by employing the finite element method, in which the dynamic coefficients of inhomogeneous foil bearings are taken into account. Compared with the experimental result, the accuracy of the prediction for the critical speed is verified to be about 14% error. Two sets of foil bearings with 22 and 41 μm nominal clearance are manufactured and tested. Test results indicate that the vibration amplitude can be greatly reduced by diminishing the bearing clearance. When foil bearings with 22 μm clearance are used, the high-order harmonic frequencies of rotor vibration are significantly inhibited, and the amplitude of the rotating frequency is obviously restricted. Thus, the foil bearing with inhomogeneous bump foils tested in this paper can meet the speed requirement of the compressor when the nominal clearance is set at 22 μm.

Shock Test and Acceleration Analysis Methods of Marine Diesel Engines to Underwater Explosions

2013 ◽  
Vol 345 ◽  
pp. 64-67
Author(s):  
Jian Hua Zhao ◽  
Rui Bo Zhang ◽  
De Bin Zhu ◽  
Hong Bin Gao
Keyword(s):  
Diesel Engine ◽  
Low Frequency ◽  
Vibration Signal ◽  
Test Methods ◽  
Shock Acceleration ◽  
Test Results ◽  
Shock Test ◽  
Marine Diesel ◽  
Reduction Methods ◽  
Acceleration Analysis

Shock test of marine diesel engine is the important content for ship anti-shock research. Plentiful shock tests of equipments have been carried out abroad, but there is no detailed test methods of diesel engine. According to simulation results, 8-channel acceleration test points are determined. Because diesel engine is working, the measured shock acceleration is interfered by vibration signal. Orthogonal wavelet decomposition and wavelet noise reduction methods are used to separate shock component from test results. The seperated shock component consists of two parts. One is the low-frequency part caused by the shock from diesel foundation and then attenuation through the isolator, the other is the high-frequency part caused by the secondary shock of the retainer.

Measurements of Rotordynamic Coefficients of Hybrid Bearings With (a) a Plugged Orifice, and (b) a Worn Land Surface

2002 ◽  
Vol 124 (2) ◽  
pp. 363-368 ◽  
Author(s):  
F. Laurant ◽  
D. W. Childs
Keyword(s):  
Test Data ◽  
Land Surface ◽  
Rocket Engine ◽  
Liquid Rocket Engine ◽  
Test Results ◽  
Rotordynamic Coefficients ◽  
Hybrid Bearing ◽  
Liquid Rocket

Test results are presented for the rotordynamic coefficients of a hybrid bearing that is representative of bearings for liquid-rocket-engine turbopump applications. The bearing is tested in the following two degraded conditions: (a) one of five orifices plugged, and (b) a locally enlarged clearance to simulate a worn condition. Test data are presented at 24,600 rpm, with supply pressures of 4.0, 5.5, and 7.0 MPa, and eccentricity ratios from 0.1 to 0.5 in 0.1 increments. Overall, the results suggest that neither a single plugged orifice nor significant wear on the bearing land will “disable” a well-designed hybrid bearing. These results do not speak to multiple plugged orifices and are not an endorsement for operations without filters to prevent plugging orifices.

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