5.1 CIMENTACIÓN SUPERFICIAL.

Based on journal bearing parameters and state space technique, Eigen values have been calculated that determine the nature frequencies of the system. As the result of Eigen analysis, the natural frequencies of the shaft and the bearing are around 6 kHz and 13 kHz. The result bellow, in Figure 5.29, presents vibration response of a journal bearing due to multi operating conditions. The operating conditions, speed 1500 rpm, under six different radial loads (1, 5, 10, 20, 40 bar) and three different oil viscosities (5, 15, 46). The vibration model has been simplified based on the value of eccentricity ration. At low eccentricity ratio, the excitation force is only correlated to fluid. At high eccentricity ratio, the excitations become more significant and correlation to both fluid and asperity forces, when the oil film thickness becomes much smaller than the size of the surface roughness.

Figure 5.29 Natural frequency modes of wide operating conditions

Figure 5.30 presents six modes, each mode shows the vibration shapes of the shaft, bearing and house masses in X any Y axis. This also, presents the nature mode of vibration under different loads and oil viscosities. Figure 5.31 presents natural frequency for each mode under different operating conditions. Natural frequencies increase while the load increase and oil viscosity decrease.

Condition Monitoring of Journal Bearings for Predictive Maintenance Management Based on High Frequency Vibration Analysis [Ch.5]

DEGREE OF DOCTOR OF PHILOSOPHY (O. Hassin) 105

Figure 5.30 Natural modes of vibration

Figure 5.31 Natural frequency Vs radial load for three different oil viscosities X-m1 X-m2 X-m3 Y-m1 Y-m2 Y-m3

Cordinates 0 0.2 0.4 0.6 0.8 1 Magnitude Mode 1 56.493Hz - 1bar / oil5 363.17Hz - 5bar / oil5 524.79Hz - 10bar / oil5 743.68Hz - 20bar / oil5 1045Hz - 40bar / oil5 170.38Hz - 1bar / oil15 262.34Hz - 5bar / oil15 488.25Hz - 10bar / oil15 735.41Hz - 20bar / oil15 1045.6Hz - 40bar / oil15 303.84Hz - 1bar / oil37 174.55Hz - 5bar / oil37 310.09Hz - 10bar / oil37 656.13Hz - 20bar / oil37 1028.5Hz - 40bar / oil37

X-m1 X-m2 X-m3 Y-m1 Y-m2 Y-m3 Cordinates 0 0.2 0.4 0.6 0.8 1 Mode 2 229.3Hz - 1bar / oil5 589.17Hz - 5bar / oil5 1006Hz - 10bar / oil5 1713.2Hz - 20bar / oil5 2833.6Hz - 40bar / oil5 274.58Hz - 1bar / oil15 502.84Hz - 5bar / oil15 760.13Hz - 10bar / oil15 1263.8Hz - 20bar / oil15 2136.1Hz - 40bar / oil15 369.52Hz - 1bar / oil37 534.5Hz - 5bar / oil37 711.89Hz - 10bar / oil37 1037.2Hz - 20bar / oil37 1681.6Hz - 40bar / oil37

X-m1 X-m2 X-m3 Y-m1 Y-m2 Y-m3 Cordinates 0 0.2 0.4 0.6 0.8 1 Magnitude Mode 3 5735.8Hz - 1bar / oil5 5737.7Hz - 5bar / oil5 5739.9Hz - 10bar / oil5 5744.1Hz - 20bar / oil5 5752.6Hz - 40bar / oil5 5735.3Hz - 1bar / oil15 5736.8Hz - 5bar / oil15 5739.3Hz - 10bar / oil15 5743.9Hz - 20bar / oil15 5752.6Hz - 40bar / oil15 5734.4Hz - 1bar / oil37 5735.3Hz - 5bar / oil37 5737.2Hz - 10bar / oil37 5742.2Hz - 20bar / oil37 5752Hz - 40bar / oil37

X-m1 X-m2 X-m3 Y-m1 Y-m2 Y-m3 Cordinates 0 0.2 0.4 0.6 0.8 1 Mode 4 5736.5Hz - 1bar / oil5 5741Hz - 5bar / oil5 5751.3Hz - 10bar / oil5 5784.2Hz - 20bar / oil5 5899.6Hz - 40bar / oil5 5736.9Hz - 1bar / oil15 5739.5Hz - 5bar / oil15 5744.5Hz - 10bar / oil15 5760.8Hz - 20bar / oil15 5815.9Hz - 40bar / oil15 5737.8Hz - 1bar / oil37 5740Hz - 5bar / oil37 5743.4Hz - 10bar / oil37 5752.3Hz - 20bar / oil37 5782.2Hz - 40bar / oil37

X-m1 X-m2 X-m3 Y-m1 Y-m2 Y-m3 Cordinates 0 0.2 0.4 0.6 0.8 1 Magnitude Mode 5 14329Hz - 1bar / oil5 14331Hz - 5bar / oil5 14334Hz - 10bar / oil5 14338Hz - 20bar / oil5 14347Hz - 40bar / oil5 14328Hz - 1bar / oil15 14330Hz - 5bar / oil15 14333Hz - 10bar / oil15 14338Hz - 20bar / oil15 14347Hz - 40bar / oil15 14327Hz - 1bar / oil37 14328Hz - 5bar / oil37 14331Hz - 10bar / oil37 14336Hz - 20bar / oil37 14347Hz - 40bar / oil37

X-m1 X-m2 X-m3 Y-m1 Y-m2 Y-m3 Cordinates 0 0.2 0.4 0.6 0.8 1 Mode 6 14330Hz - 1bar / oil5 14335Hz - 5bar / oil5 14346Hz - 10bar / oil5 14380Hz - 20bar / oil5 14480Hz - 40bar / oil5 14330Hz - 1bar / oil15 14333Hz - 5bar / oil15 14339Hz - 10bar / oil15 14356Hz - 20bar / oil15 14410Hz - 40bar / oil15 14331Hz - 1bar / oil37 14334Hz - 5bar / oil37 14337Hz - 10bar / oil37 14347Hz - 20bar / oil37 14378Hz - 40bar / oil37

Figure 5.32 Vibration response of mode 6 at 1500 rpm and under 40 bar

5.8 Summary

A mathematical model is established for carrying out an in-depth of bearing vibration responses. This model considers not only conventional fluid forces but also asperity collision and churn effect, allowing explaining high frequency responses of the lubricated journal bearing to be the effect of micro asperity elastic deformations. The model with six degrees of freedom are solved by using the state space technique, each Eigen value and volume of a certain mass in one direction present natural and shape modes, respectively. The natural frequencies of the system are found to be around 6 kHz and 13 kHz. Additionally, as a result of asperity collisions which increase with higher radial loads or lower viscous oil, the natural frequencies of the journal bearing can shift higher.

CHAPTER SIX

6

TEST SYSTEMS AND METHODS

To verify and evaluate theoretical analysis and fault detection methods proposed, this chapter describes the test rig construction that includes the setup of journal bearing bench, instrumentation and other facilities with specifications of mechanical and electrical components, measurement instrumentations and devices. In addition, different test procedures are also depicted with respect to different bearing fault cases to be tested.

6.1 Introduction

To fulfil the aim and objectives planned, the research began with designing and building a bearing test rig to gain basic understandings of journal vibrations along with their operating characteristics. Moreover, the rig is capable to verify and evaluate techniques developed for fault detection and diagnosis.

The rig consists of an AC motor, a DC generator, a hydraulic system of radial load, two self-aligning spherical journal bearings and measurement instrumentation systems, including a data acquisition, an encoder, thermocouples, a pressure sensor, displacement laser sensors and accelerometers. In this configuration and selection, the bearing undertakes minimal misalignment effect when it operates under different loads, speeds and oil conditions. Simultaneously, bearing vibrations on its housing can be measured at high sampling rate together with other critical operating parameters.

Preliminary experiments were conducted to ensure all equipment and instrumentation to operate as expected and to obtain good measurement repeatability and reliability. Preliminary experiment results showed that all the equipment including the driving, the loading, the data acquisition and the measurement system perform adequately. The test rig is displayed in Figure 6.1 and Figure 6.2.

The motor speed is controlled by a Siemens Micro Master Controller so the drive shaft can be run at different speeds. Also, a manual hydraulic pump is used to apply a defined radial load.

Condition Monitoring of Journal Bearings for Predictive Maintenance Management Based on High Frequency Vibration Analysis [Ch.6]

DEGREE OF DOCTOR OF PHILOSOPHY (O. Hassin) 109

Figure 6.2 Self-journal bearing test system