As a final section of work, the IVHM framework for rotating machinery and corresponding discussions has been combined with information collated throughout the research. The result of this is a final graphical methodology specific to localising imbalance in rotating machinery. Whilst simplified through necessity (as all notes and recommendations from this thesis cannot fit into a single diagram), this representation still includes key work.
Taking aspects of the literature review, modelling, experimental studies and IVHM discussion, the graphical methodology can be seen in Error! Reference
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and maintenance influences the application of a system. Depending upon this application, a number of constraints may be identified. Those listed are common limitations arising from the existing research (and that conducted within this project).
The ‘core research’ lists the ‘state of the art’ in imbalance localisation identified from the review of literature (along with the novel method developed in this thesis). This provides a quick ‘go to’ list of existing technologies. Once the core constraints and existing research is understood, a system may be designed through a synergy between data-driven and physics-based simulations. Additional testing may then be performed, as described throughout this work, making use of the latest simulations and rotordynamic rigs (before scaling up). A typical method of implementation (as used within this research) then realises the justifications set out at the start. Through this summary chart, combined with the ‘IVHM’ framework, future developments in the field of localising imbalance faults for complex rotating machinery may be performed. Ultimately, it is intended that any future researchers may use this summary to good effect when undertaking such a project. As such, at this point the final novel contribution arising from this project may be concluded.
7.7 Chapter Discussion
Throughout the work performed up to this point, a number of themes can be identified which enable imbalance localisation to be placed in context. It has been noted through the literature review that many imbalance diagnosis and localisation techniques which have been detailed in literature make a number of assumptions. One of these prime assumptions is that the benefit of diagnosing and localising imbalance far outweighs the costs involved. Whilst the importance of imbalance faults should not be underestimated, this assumption in many cases leads to systems which would be impractical in many real world applications. Through this research, working through a new method of fault localisation in joint consideration with the potential implementation and the ‘case study’ described, the following guidance can be highlighted for the future development of IVHM systems for diagnosing and localising common faults: Initially, it is important to state two key points, highlighted from this research:
• A cost/benefit balance should be considered at the initial research stage. • Application relevant constraints have a particularly significant influence
on the design of an IVHM system for localising imbalance.
If these two criteria can be addressed, the following questions aid the design of a system for localising common faults:
General Application:
From power generation to electric machinery and aircraft engines to vehicle turbochargers, a wide range of rotating machines exist, and their design and modes of operation can have significant impact on the type of health monitoring systems which can be implemented. Some key questions for fault localisation include:
• Are operating conditions steady-state or variable?
• Is the rotor rigid or flexible? How many operational modes affect the
• How great is the cost of machine downtime?
• How easily can sensors be integrated within the machine?
• Considering the flow Sense -> Acquire -> Analyse -> Transfer -> Act.
What limitations are present within this, and where is the ‘bottleneck’?
• How easily can benchmark/training data be acquired?
The ‘case study’ highlights that within one broad application (aircraft gas turbines); a number of key limitations exist, which would render many current fault localisation systems impractical. This highlights the importance for application, practicality and cost-benefit to be considered throughout the design of IVHM systems for imbalance localisation. At present these considerations are absent from a large portion of rotordynamics research.
The final graphical methodology for designing an imbalance localisation system uses the latest published research alongside the findings from this thesis to provide a guide which is highly relevant and ‘up to date’ (at point of submission) for future research. This methodology may enable some of the limitations of current imbalance localisation methods to be avoided in future systems.
7.8 Chapter Conclusions
In this chapter, the place of an imbalance localisation system within a future IVHM system for rotating machinery has been discussed. Key concepts, limitations and recommendations are made for future developments based upon the findings from this research. The following aims have therefore been achieved:
• Novel Aspect: Two graphical methodologies for the development of future IVHM systems for locating and diagnosing common rotordynamic faults have been developed. These have been based upon the findings from this research, and have been illustrated together with key points and recommendations for future research.
8 Summary Discussion
The final section of this work contains a discussion of all the research and related findings from this project, aimed at highlighting the novel aspects, discussing the advantages and disadvantages of the research and describing potential future research directions.