Mechanical Systems Reliability Essay Example

Mechanical Systems Reliability

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Lecturer:

Monitoring techniques Evaluation

Rotating gears in a wind turbine gearbox has several defects that must be examined. Several methods are used in analyzing the wind turbine defects. Amongst these, the two principal techniques used are acoustic emission and vibration that ought to be taken into consideration in examining the errors in the turbine. When the two methods are considered together, they tend to have their unique importance in varying working conditions. With the different sensors installed in the wind turbine gearbox, they have sensors that record acoustic emissions and vibration signatures (Sharon and Terry, 2005, 16). Vibration analysis and acoustic emission are termed as well proven and low-cost making them more feasible techniques for monitoring wind turbine gear box faults. Additionally, combining the two methods may be applicable in in developing wind turbine monitoring system. However, in the current age in technology, vibrational analysis is widely used in wind turbine to trace growth of the bearing and gearbox faults compared to oil particle counters.

Vibrational analysis

On obtaining the vibrational signals, they are converted to the electrical signal using a traducer installed in the system. The transducers are of three main categories, which include acceleration, relative displacement and velocity.

Accelerometers, which are part of the acceleration transducers have a very high impedance that can be lowered by the use of transistorized preamplifiers (Yongqiang, et al., 2011, 100). The preamplifiers convert the high impedance to low impedance, which can be used at the same time as integration and amplification.

Vibration signals that are complex have a combination of the sinusoidal waveform with varying amplitude, phase difference and frequencies that are broken down to form frequency components from the vibrational signals.

Acoustic emission

This technique is a class of process in which transient flexible waves are yielded by the nippy release of energy originating from sources such as relaxation transient of strain and stress fields. Some of the phenomenal occurrences that are associated with the AE include plastic deformation, fracture, crack initiation, and growth (Nosonovsky, and Bharat, 2012, 525). This dynamical nature of Acoustic Emission renders this technique has a technique with high integrity for monitoring critical components and structures.

Condition monitoring system

Vibrational analysis is used in the control of the wind turbine gearbox, main bearing and nacelle (noise and temperature), which is additionally monitored by the combination of the acoustic analysis. This way data is collected at fixed intervals while the results are remotely sent to a server used for diagnostics (Yongqiang, L., et al., (2011, 100). When the results are in the server, they are accessible at any given time in case there is a need for analysis.

Measurement and analysis

Vibration Frequency Domain Analysis

Once the accelerometer acquires the signal, it indicates a reading of the produced voltage corresponding to the vibration level. The Data Acquisition system then collects the analog signals given by the accelerometer Card and translates them into signals that are digital. Then it makes it easier for it to read the data and analyze it in the given interface (Norton, and Karczub, 2003, 561). The software used in the analysis uses the analysis method to perform the data analysis.

Characteristics of a temperature sensor

Compared traditional rotating machines, wind turbines have low rotating speed and varying loads. Therefore, WT signals like temperature depend on operating condition of the turbine as well as its surrounding ambient. Changes in temperature do not necessary mean there is the fault in the gearbox (Sharon and Terry, 2005, 16). Nevertheless, if there is an error in the gearbox, it may lead to change in temperature. Similarly, temperatures of the component like the gearbox oil temperature do relate to the load of the wind turbine and the nacelle temperature. This correlation is simulated in a demonstration of the generator ambient temperature and generator power versus the generator bearing temperature shown in fig 1. When the generator bearing fault can result in an increase in bearing temperature, which could correlate with varying generator power and ambient temperature experience throughout the generator cooling system see fig 2.

Therefore, it is easy to conclude that, regardless of the fact that fault generator bearing may result in an increase in temperature increase for the bearing, this rise in temperature can correlate to varying generator power and ambient temperature despite the fact that the cooling the system is in good working condition.

Evaluation of Improvement Proposal

In wind turbines, there several power dissipation losses that the turbine undergoes. Therefore, it is necessary to comprehend the efficiency and power loss of the gearbox. To some extent the experiences power has a significant influence on the performance of the gearbox, which include;

Load dependent loss: this account for the frictional power losses resulting from the gear tooth sliding. To reduce power losses related to friction of the gear tooth, it is necessary to ensure that that the gearbox lubrication system is well maintained to ensure the gear tooth have little resistance that may lead to load losses.

Churning power loss: this is the power loss in the WT resulting from the mechanical elements, which occurs due to the friction developed from the fluid that the elements are immersed. Thus, to lower the losses related to mechanical elements and the lubrication fluid; it is necessary to ensure that in future the lubrication oil is heated to temperatures higher than -150D, maintain high temperature for the lubrication fluid helps in the maintenance of the system to operate optimally (Stamboliska, Rusiński, and Moczko, 2014, 5).

When the power losses in the gearbox casing are equal to the dissipated heat flow from the gearbox.

Proposal to reduce false alarm

Consideration to increase wind turbine monitoring is earning consideration as the wind turbines tend to become larger and moved to locations that are inaccessible like offshore. Monitoring that is based on consideration in the industries tend to be more successful for larger wind turbines when attention is given on the data collection. Based on the comparison of the conventional condition monitoring and wind turbine condition monitoring, such signal like energy or load are convectional condition monitoring. Therefore, capitalizing on a multi parameter approach, independent signal tend to give confidence to deal with fault signals. Applying this method helps to reduce the potential false alarm.

References

Norton, P.M. and Karczub, D. G. (2003) Fundamentals of Noise and Vibration Analysis for Engineers. Cambridge:
Cambridge University Press. 561

Nosonovsky, M. and Bharat, B. (2012) Green Tribology: Biomimetics, Energy Conservation and Sustainability. New York: Springer Science & Business Media. 525

Sharon A. and Terry, E. (2005) Beginning Relational Data Modeling. New York, NY: Apress. 16

Stamboliska, Z., Rusiński, E. and Moczko, P., (2014) Proactive Condition Monitoring of Low- Speed Machines. New York: Springer. 4-6

Yongqiang, L., et al., (2011) Power Conversion and Control of Wind Energy Systems. New York: John Wiley & Sons. 100

Appendices

Lecturer:

Figure 1: Temperature of generator bearing against ambient temperature and generator power

Lecturer: 1

Figure 2: Correlation between wind turbine output power and generator bearing temperature

Lecturer: 2

Figure 3: vibration-based wind turbine condition monitoring system (CMS

1-Fiber optic transducers, 2 and 8-speed transducers, 3,4,5,6,7,9,10,11- accerelometers, 12-oil debris counters, 13-online CMS, 14- control center PC

Total power in the gearbox equation

Lecturer: 3

Lecturer: 4Dissipated friction power from gears

Lecturer: 5Bearings dissipated friction power

Lecturer: 6Gear dissipated churning power

Lecturer: 7Bearings dissipated churning power

Lecturer: 8Seals dissipated churning power

Lecturer: 9

Figure 4: thermocouple responseroged

Gearbox calculations

Having two gears, one has been used as gear A and the other Gear B

Lecturer: 10

Where acceptableLecturer: 11

Bearing frequency inner and outer diameters

Ball spinLecturer: 12

Outer diameter
Lecturer: 13