Onset of 12X Vibration and Its Prevention

2009 ◽  
Vol 132 (2) ◽  
Author(s):  
John J. Yu
Keyword(s):  
Parametric Excitation ◽  
Vibration Amplitude ◽  
Operating Conditions ◽  
Experimental Results ◽  
Rotating Machines ◽  
Supply Pressure ◽  
Upward Shift ◽  
Oil Whirl ◽  
Multiple Orders ◽  
Spectrum Data

This paper discusses real cases on three different machines where subsynchronous vibration occurred suddenly at a frequency exactly equal to one-half (12X) of the operational speed of 3600 rpm. In two cases, vibration amplitude increased from around 2 mils (51 μm) pp to over 12 mils (305 μm) pp, causing the machine to trip unexpectedly. The 12X vibration was even sustained during shutdown at speed below 3600 rpm after trip. Unlike other reported experimental results, shaft orbit measured by proximity probes was fairly circular and dominantly composed of the 12X component without significant components at multiple orders of the 12X. The onset of the subsynchronous 12X vibration was sometimes triggered by changes in bearing lube oil temperature and supply pressure, which would typically be believed to be caused by oil whirl that could occur at close to the 12X frequency. An upward shift in shaft centerline plot was observed to occur prior to the onset of the subsynchronous vibration. The 12X vibration was successfully prevented by changing bearing clearance or adjustment of bearing oil temperature and supply pressure. Parametric excitation analysis on 12X vibration is also given in this paper. The main purpose of this paper, unlike previously published papers on analytical or experimental results, is to show shaft orbital and centerline plots as well as spectrum data due to the 12X vibration, including effects of operating conditions in real rotating machines.

Onset of 1/2X Vibration and Its Prevention

2009 ◽  
Author(s):  
John J. Yu
Keyword(s):  
Parametric Excitation ◽  
Vibration Amplitude ◽  
Operating Conditions ◽  
Experimental Results ◽  
Rotating Machines ◽  
Supply Pressure ◽  
Upward Shift ◽  
Oil Whirl ◽  
Multiple Orders ◽  
Spectrum Data

This paper discusses real cases on three different machines where subsynchronous vibration occurred suddenly at a frequency exactly equal to one-half (1/2X) of the operational speed of 3600 rpm. In two cases, vibration amplitude increased from around 2 mils (51 μm) pp to over 12 mils (305 μm) pp, causing the machine to trip unexpectedly. The 1/2X vibration was even sustained during shutdown at speed below 3600 rpm after trip. Unlike other reported experimental results, shaft orbit measured by proximity probes was fairly circular and dominantly composed of the 1/2X component without significant components at multiple orders of the 1/2X. The onset of the subsynchronous 1/2X vibration was sometimes triggered by changes in bearing lube oil temperature and supply pressure, which would typically be believed to be caused by oil whirl that could occur at close to the 1/2X frequency. An upward shift in shaft centerline plot was observed to occur prior to the onset of the subsynchronous vibration. The 1/2X vibration was successfully prevented by changing bearing clearance or adjustment of bearing oil temperature and supply pressure. Parametric excitation analysis on 1/2X vibration is also given in this paper. The main purpose of this paper, unlike previously published papers on analytical or experimental results, is to show shaft orbital and centerline plots as well as spectrum data due to the 1/2X vibration, including effects of operating conditions in real rotating machines.

Optimal Design of Squeeze Film Supports for Flexible Rotors

1983 ◽  
Vol 105 (3) ◽  
pp. 487-494 ◽  
Author(s):  
M. D. Rabinowitz ◽  
E. J. Hahn
Keyword(s):  
Optimal Design ◽  
Vibration Amplitude ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Rotor Vibration ◽  
Design Constraints ◽  
Supply Pressure ◽  
Flexible Rotors ◽  
Wide Range ◽  
Film Lubrication

Assuming central preloading, operation below the second bending critical speed, and full film lubrication, this paper presents a theoretical model which allows one, with minimum computation, to design squeeze film damped rotors under conditions of high unbalance loading. Closed form expressions are derived for the maximum vibration amplitudes pertaining to optimally damped conditions. The resulting vibration amplitude and transmissibility data of design interest are presented for a wide range of practical operating conditions on a single chart. It can be seen that for a given rotor, the lighter the bearing the more easily one can satisfy design constraints relating to allowable rotor vibration levels and lubricant supply pressure requirements. The data presented are shown to be applicable to a wide variety of rotors, and a recommended procedure for optimal design is outlined.

Half-frequency whirl of pistons in axial piston pumps and motors under mixed lubrication

2003 ◽  
Vol 217 (2) ◽  
pp. 93-102 ◽  
Author(s):  
K Tanaka ◽  
T Nakahara ◽  
K Kyogoku
Keyword(s):  
Mixed Lubrication ◽  
Operating Conditions ◽  
Axial Piston Pump ◽  
Piston Motion ◽  
Axial Piston Pumps ◽  
Supply Pressure ◽  
Oil Whirl ◽  
Lubrication Characteristics ◽  
Axial Piston ◽  
Lubrication Conditions

Dynamic lubrication characteristics between a piston and a cylinder in an axial piston pump and motor have been calculated under mixed-lubrication conditions. The calculated results have shown that half-frequency whirling of the piston occurs under some operating conditions and specifications such as low supply pressure, narrow clearance and long sealing length between the piston and the cylinder, in a manner similar to the oil whirl phenomenon in journal bearings. The whirl phenomenon has been confirmed by measurements of piston motion.

scholarly journals Optimal Design of Squeeze Film Supports for Flexible Rotors

1982 ◽  
Author(s):  
M. D. Rabinowitz ◽  
E. J. Hahn
Keyword(s):  
Optimal Design ◽  
Vibration Amplitude ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Rotor Vibration ◽  
Design Constraints ◽  
Supply Pressure ◽  
Flexible Rotors ◽  
Wide Range ◽  
Film Lubrication

Assuming central preloading operation below the second bending critical speed and full film lubrication, this paper presents a theoretical model which allows one, with minimum computation, to design squeeze film damped rotors under conditions of high unbalance loading. Closed form expressions are derived for the maximum vibration amplitudes pertaining to optimally damped conditions. The resulting vibration amplitude and transmissibility data of design interest are presented for a wide range of practical operating conditions on a single chart. It can be seen that for a given rotor, the lighter the bearing the more easily one can satisfy design constraints relating to allowable rotor vibration levels and lubricant supply pressure requirements. The data presented are shown to be applicable to a wide variety of rotors, and a recommended procedure for optimal design is outlined.

Numerical simulation and experimental performance research of cylindrical vane pump

2021 ◽  
pp. 095440622110200
Author(s):  
Yiqi Cheng ◽  
Xinhua Wang ◽  
Waheed Ur Rehman ◽  
Tao Sun ◽  
Hasan Shahzad ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Rotational Velocity ◽  
Geometric Theory ◽  
Mechanical Efficiency ◽  
Operating Conditions ◽  
Experimental Results ◽  
Field Analysis ◽  
Total Efficiency ◽  
Three Dimensional Model ◽  
Vane Pump

This study presents a novel cylindrical vane pump based on the traditional working principle. The efficiency of the cylindrical vane pump was verified by experimental validation and numerical analysis. Numerical analysis, such as kinematics analysis, was performed in Pro/Mechanism and unsteady flow-field analysis was performed using ANSYS FLUENT. The stator surface equations were derived using the geometric theory of the applied spatial triangulation function. A three-dimensional model of the cylindrical vane pump was established with the help of MATLAB and Pro/E. The kinematic analysis helped in developing kinematic equations for cylindrical vane pumps and proved the effectiveness of the structural design. The maximum inaccuracy error of the computational fluid dynamics (CFD) model was 5.7% compared with the experimental results, and the CFD results show that the structure of the pump was reasonable. An experimental test bench was developed, and the results were in excellent agreement with the numerical results of CFD. The experimental results show that the cylindrical vane pump satisfied the three-element design of a positive-displacement pump and the trend of changes in efficiency was the same for all types of efficiency under different operating conditions. Furthermore, the volumetric efficiency presented a nonlinear positive correlation with increased rotational velocity, the mechanical efficiency showed a nonlinear negative correlation, and the total efficiency first increased and then decreased. When the rotational velocity was 1.33[Formula: see text] and the discharge pressure was 0.68[Formula: see text], the total efficiency reached its maximum value.

Steady-State and Dynamic Properties of the Floating-Ring Journal Bearing

1968 ◽  
Vol 90 (1) ◽  
pp. 243-253 ◽  
Author(s):  
F. K. Orcutt ◽  
C. W. Ng
Keyword(s):  
Steady State ◽  
Journal Bearing ◽  
Dynamic Properties ◽  
Calculated Data ◽  
Experimental Results ◽  
Supply Pressure ◽  
Pressure Parameter

Calculated data on steady-state and dynamic properties of the plain cylindrical floating-ring bearing with pressurized lubricant supply are given. The data are for a bearing with L/D of 1, and values of the ratio of inner to outer film clearances of 0.7 and 1.3. One value of dimensionless supply pressure parameter is covered. Experimental results are presented which verify the calculated results and which supplement them, particularly with respect to stability characteristics of the bearing.

The Influence of Lubricant Supply Conditions and Bearing Configuration on the Performance of (Semi) Floating Ring Bearing Systems for Turbochargers

2017 ◽  
Author(s):  
Luis San Andrés ◽  
Feng Yu ◽  
Kostandin Gjika
Keyword(s):  
Heat Flow ◽  
Thermal Energy ◽  
Operating Conditions ◽  
Temperature Fields ◽  
Engine Oil ◽  
Large Temperature ◽  
Oil Viscosity ◽  
Supply Pressure ◽  
The Impact ◽  
Bearing System

Engine oil lubricated (semi) floating ring bearing (S)FRB systems in passenger vehicle turbochargers (TC) operate at temperatures well above ambient and must withstand large temperature gradients that can lead to severe thermo-mechanical induced stresses. Physical modeling of the thermal energy flow paths and an effective thermal management strategy are paramount to determine safe operating conditions ensuring the TC component mechanical integrity and the robustness of its bearing system. On occasion, the selection of one particular bearing parameter to improve a certain performance characteristic could be detrimental to other performance characteristics of a TC system. The paper details a thermohydrodynamic model to predict the hydrodynamic pressure and temperature fields and the distribution of thermal energy flows in the bearing system. The impact of the lubricant supply conditions (pressure and temperature), bearing film clearances, oil supply grooves on the ring ID surface are quantified. Lubricating a (S)FRB with either a low oil temperature or a high supply pressure increases (shear induced) heat flow. A lube high supply pressure or a large clearance allow for more flow through the inner film working towards drawing more heat flow from the hot journal, yet raises the shear drag power as the oil viscosity remains high. Nonetheless, the peak temperature of the inner film is not influenced much by the changes on the way the oil is supplied into the film as the thermal energy displaced from the hot shaft into the film is overwhelming. Adding axial grooves on the inner side of the (S)FRB improves its dynamic stability, albeit increasing the drawn oil flow as well as the drag power and heat flow from the shaft. The predictive model allows to identify a compromise between different parameters of groove designs thus enabling a bearing system with a low power consumption.

scholarly journals Predictive Modelling of Wellhead Corrosion due to Operating Conditions: A Field Data Approach

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Chinedu I. Ossai
Keyword(s):  
Corrosion Rate ◽  
Field Data ◽  
Oil And Gas ◽  
Multiple Linear Regression Model ◽  
Predictive Modelling ◽  
Operating Conditions ◽  
Experimental Results ◽  
Operating Parameters ◽  
Oil And Gas Fields ◽  
The Impact

The flow of crude oil, water, and gas from the reservoirs through the wellheads results in its deterioration. This deterioration which is due to the impact of turbulence, corrosion, and erosion significantly reduces the integrity of the wellheads. Effectively managing the wellheads, therefore, requires the knowledge of the extent to which these factors contribute to its degradation. In this paper, the contribution of some operating parameters (temperature, CO2 partial pressure, flow rate, and pH) on the corrosion rate of oil and gas wellheads was studied. Field data from onshore oil and gas fields were analysed with multiple linear regression model to determine the dependency of the corrosion rate on the operating parameters. ANOVA, value test, and multiple regression coefficients were used in the statistical analysis of the results, while in previous experimental results, de Waard-Milliams models and de Waard-Lotz model were used to validate the modelled wellhead corrosion rates. The study shows that the operating parameters contribute to about 26% of the wellhead corrosion rate. The predicted corrosion models also showed a good agreement with the field data and the de Waard-Lotz models but mixed results with the experimental results and the de Waard-Milliams models.

The Influence of Ambient Pressure on the Dynamic Response of RF MEMS Switches

2010 ◽  
Author(s):  
Avihay Ohana ◽  
Oren Aharon ◽  
Ronen Maimon ◽  
Boris Nepomnyashchy ◽  
Lior Kogut
Keyword(s):  
Rf Mems ◽  
Ambient Pressure ◽  
Actuation Voltage ◽  
Operating Conditions ◽  
Experimental Results ◽  
Release Time ◽  
Q Factor ◽  
Optimal Operating ◽  
Mems Switches ◽  
Rf Mems Switches

A study of the dynamic behavior of an RF MEMS switch is presented at different operating conditions. Experimental results for the actuation and release time and Q-factor as a function of the ambient pressure and actuation voltage are compared to theoretical predictions based on existing model. Optimal operating conditions (ambient pressure and actuation voltage) are determined based on two criterions: minimal actuation and release time and minimal oscillations upon switch release. In light of the experimental results optimal operating conditions determined to be 1.4Vpi at a pressure of a few torrs where actuation and release time are equal and short enough with no release oscillations. Three pressure regimes are identified with characteristic behavior of the Q-factor and actuation and release time in each regime. These behaviors have significant implications in many MEMS devices, especially RF MEMS switches.

Effect of Fuel Injection Strategy on DPF Regeneration in Single Cylinder Diesel Engine

2015 ◽  
Author(s):  
Sungjun Yoon ◽  
Hongsuk Kim ◽  
Daesik Kim ◽  
Sungwook Park
Keyword(s):  
Diesel Engine ◽  
Fuel Injection ◽  
Operating Conditions ◽  
Experimental Results ◽  
Exhaust Gas ◽  
Post Injection ◽  
Gas Temperature ◽  
Injection Strategy ◽  
Dpf Regeneration ◽  
Exhaust Gas Temperature

Stringent emission regulations (e.g., Euro-6) force automotive manufacturers to equip DPF (diesel particulate filter) on diesel cars. Generally, post injection is used as a method to regenerate DPF. However, it is known that post injection deteriorates specific fuel consumption and causes oil dilution for some operating conditions. Thus, an injection strategy for regeneration becomes one of key technologies for diesel powertrain equipped with a DPF. This paper presents correlations between fuel injection strategy and exhaust gas temperature for DPF regeneration. Experimental apparatus consists of a single cylinder diesel engine, a DC dynamometer, an emission test bench, and an engine control system. In the present study, post injection timing covers from 40 deg aTDC to 110 deg aTDC and double post injection was considered. In addition, effects of injection pressures were investigated. The engine load was varied from low-load to mid-load and fuel amount of post injection was increased up to 10mg/stk. Oil dilution during fuel injection and combustion processes were estimated by diesel loss measured by comparing two global equivalences ratios; one is measured from Lambda sensor installed at exhaust port, the other one is estimated from intake air mass and injected fuel mass. In the present study, the differences in global equivalence ratios were mainly caused from oil dilution during post injection. The experimental results of the present study suggest an optimal engine operating conditions including fuel injection strategy to get appropriate exhaust gas temperature for DPF regeneration. Experimental results of exhaust gas temperature distributions for various engine operating conditions were summarized. In addition, it was revealed that amounts of oil dilution were reduced by splitting post injection (i.e., double post injection). Effects of injection pressure on exhaust gas temperature were dependent on combustion phasing and injection strategies.

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