Structural Reliability and Analysis of Turbine Blades

Table of Contents

CHAPTER-1
Introduction
Feasibility Study of Turbine Blade Failure Prevention and Its Reliability
Legislation and Ethics

CHAPTER-2
Tasks related to Expected Gantt chart
Planned Gantt Chart/Expected Gantt Chart
Actual Gantt Chart
Critical Path Analysis
CPA & Actual vs Planned Gantt Chart
Improvements to be made
Logbooks
Methods to monitor and meet project milestones
SWOT Analysis based on Project Plan:

CHAPTER-3 GAS TURBINE BLADE
Rolls Royce Trent 7000
Development:
Specifications:
Turbine Blades:
Classification: Pressure
Classification: Flow Direction
Axial Flow Turbine:
Radial Flow Turbine:
Classification: Function
Impulse Turbine Blade
Reaction Turbine Blade
Production of Turbine Blades
Turbine Blade Materials
Stainless Steel Alloy
Aluminum Alloy
Titanium Alloy

CHAPTER-4 TURBINE BLADE ANALYSIS
Aerodynamics and Fatigue Analysis
Accident Investigation and Turbine Blade Failure
Enhance Internal Cooling of Turbine Blades
Impingement Cooling of Turbine Blades
Pin-Fin Cooling of Turbine Blades
Dimple Cooling of Turbine Blades
Structural & Thermal Analysis Based on Turbine Blade:
Reliability Study of Turbine Blades
Reliability Calculations:
Failure Rate/Probability of Failure of Turbine Blades
Reliability Calculations
MTTR Calculation Reliability Method
MTBF Calculation Reliability Method
Reliability Calculation based on Vibrational Diagnosis:
Analysis and Evaluation of Project Findings
Evaluation Matrix:
Weight Decision Matrix:
How the research increased the Reliability of Turbine Blades
Coolant Feeding
Material technology
Advanced cooling technology
Winglet blade tip design
Project Improvement

CHAPTER-1 INTRODUCTION

Introduction

Engines according to study, has a limited life cycle of 60 thousand. In circumstances that are unknown it shows that blades tend to show signs of fatigue cracks at 20 thousand cycles which leads to detrimental effects on the aircraft at its 60 thousand cycle. With this problem, airliners replace their aircraft blades when signs of cracks begin to show which makes turbine blades not cost effective and reliable to reach its life limit of 60 thousand cycles as it may cause the aircraft to fail in unprecedented circumstances to fatal accidents. In the past decades, the TET or the turbine entry temperature of aircrafts have significantly increased. The improvement of the turbine ability, efficiency represents a challenge blades as studied, at a certain life cycle and with this drawback could make the entire engine fail.

The reason I choose this Turbine blade-based scenario is because engine failures in Aviation have been rising due to fatigue. The turbines are considered to be exposed to fluctuating loads that result in high cyclic fatigue and stress that propagates through loads of tension. Crack spread by 2 forms Low & High Loop Fatigue has to do the deformations because the LCF is defined by repetitive plastic deformation in each process in which elastic deformation characterizes the HCF.The amount of cycles loss is small for LCF and high for HCF, thus low and high cycle fatigue, LCF and HCF transformation is dependent on stress rates between plastic and elastic deformations. Where the stress applied is below the material's elastic limit and the number of cycles to failure is large. In a fairly significant amount of periods, the structure exists at breakdown, and pressures and strains remain beyond the material's elastic spectrum to adjust. However, engine failures are mainly attributed to part malfunctions, turbine blade fatigue leads to this as well as triggering systemic failure. While engines have a dispatch rating between 99.99 percent and 99.89 percent, it will not correctly classify the faults during the trip, with this the loss between 0.01 or 0.11 percent may prove lethal to the aircraft's reputation and efficiency. I should then be likely to conclude from this work about how to boost the strength of blades based about their architecture or through preventive methods.

Feasibility Study of Turbine Blade Failure Prevention and Its Reliability

Aircrafts have multiple components in its Engine. The most common detrimental factor in turbine blades are cyclic fatigue corrosion, and like all components they have a service life. In accordance to aircraft certification necessary requirements their life cycle or service life is determined by thorough analysis of fatigue propagation. There are two approaches in fatigue failure in turbine blades. Before formation, is when inspecting the aircraft turbine blade and asses the fatigue depth before it reaches 0.4 to 0.8 mm crack propagation. Metallalurgical defects, technological defects and operational defects mas be considered to obtain life values of the turbine blade. This method increases the longevity of parts that predicts the presence of the initial defects of propagation. To combat sulphidation of the turbine blade root, the High-Pressure Turbine Blades must follow the AMM and require nitric acid bath in order to remove sulfidation deposits. This method prevents root fracture propagation, in some cases a ferric chloride etches and an abrasive blast is done to recondition the root area. The increase of load intensity on the engines, causes high-cycle fatigue in aircrafts, this increases the engine running time thus makes the turbine blades reach its cycles faster, The main course of action to prevention of fatigue failure, is through the use of vibrational diagnosis. This can be seen in Figure 2. The Engine used for this systematic prevention is the Rolls Royce Trent 7000, and is optimized for the aircraft Airbus A330 neo. This engine delivers a thrust of 68 thousand to 72 thousand lbs and contributes a 12% fuel burn efficiency compare to its previous counterpart the Rolls Royce Trent 700. The general tests carried out in this engine system are shown in the table below:

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Figure 1 Turbine Blade Analysis Vibrational Diagnosis

In this diagnosis, it revolves Gas Pressure Pulsation. Vibration Sensor, Radial Clearance. The signal generation is utilized by the 2 transformation methods which are Fourier and Wavelet transformation. A method used in this prevention is Prony, where systems will have non-contact diagnosis on the turbine blades through the use of an amplifier, the turbine blade will be subjected to its operational rpm but it is connected with sensors, the signals received by the amplifier are sent to the Computer and produces a Signal wave. ANSYS software would be implemented into this solution for aerodynamic conditions experienced by the engine itself that allows that affects the reliability of the turbine blade. However, if the root fracture has extended to its allowable limits, the turbine blade must be replaced immediately.

Legislation and Ethics

In aviation project management there are regulatory bodies which legislate the aircraft components. They employ Enhance Global Civil Aviation Safety; these is a strategic objective implemented by ICAO or International Aviation Organization. These regulatory bodies are EASA, FAA and UKCAA. Airbus is a manufacturing company which employs this, as an Engineering Intern following legislations from these regulatory bodies are required for Project management. This is where Ethics and Human Factors are associated with Management.

An implementation of Program Management and Accountability is the accountability of the ethical behaviour of employees in order to reduce the waste, the increase of transparency and creating success. This establishment is applied to all companies including the industry. Ethics increases the following characteristics in the Aviation Industry:

- Reduction of risks in proj ects
- Increase chances of success
- Reduces Stress and Anxiety
- Faith and Trust would increase in the workplace
- Profession and future standards would elevate in the workplace
- An improvement of relationship in all business levels

There are 4 core ethical values in Project management. This is Thrust worthiness, responsibility, fairness and respect. Thrust worthiness in a project concerns with the honesty in which we have to convey the truth when it comes to situations to avoid misleading or deceiving your team and consumers, where in reliability would be affected as well as this imposes commitments that is dealt with your consumer or customer that you must be able to deliver the product at hand. In your team you should honour respect, as you should treat people with equality and should accept individual differences of ideas and morals. You should be also responsible of your actions, as you would be held accountable for such tasks. By being responsible you should have diligence, perseverance, accountability and the pursuit of doing your work effectively. Lastly, fairness is one of the most important ethical value as it is separated into three core values which are:

1. Process
2. Equity
3. Impartiality

The process of fairness should be unbiassed in gathering and evaluating all of the information needed to be intake to make decisions, as a fair person would seek relevant information regardless of conflicting perspectives. Equity is the value of correcting the mistakes of others but not taking advantage of their weaknesses. The last core value is impartiality as a fair person should not be biased and must not have any favouritism.

In the aviation industry, this is important as the needs and safety of the passengers are the upmost importance. Employees of the organization in this industry must have this quality in order to ensure that they can fulfil/comply to the regulations and have the customers to ensure that they are always safe at all times. In the aviation industry, all personnel must strive to maintain their professionalism and take responsibility as well for all action and must be aware of how each individual contributes to the overall safety of a company and the aircraft. Professionalism in us begins with being fit for duty, this means that we are in the proper physical and mental condition to do the task at hand and we must ensure that we have mental and situational awareness. Helping others is a way as well in order for us to guide the employees or co-workers in the company and for them to learn to correct the mistakes that are made. Errors that have been done must be reported though everyone does not want their error to be known about by everyone, this will help the company as a whole and for the personnel to learn from his/her mistake. By having these two qualities, as future engineers we must comply to the rules and regulations as well. By complying to proper procedures this will:

- Avoid violations to be committed by the personnel that works in the company.
- Safety of everyone in the workplace.

The Aviation Maintenance Human Factors or EASA PART 145 discusses the professionalism of a person but is limited due to organizational problems that could affect him/her such as the lack of resources, pressure and other factors that could affect him or her. This Legislation PART 145 embodies the term integrity as him or her must have “A firm adherence to a code of moral values” Complying to procedures is important as this will have a positive effect and a consistent practice to the employees as they will be better individuals and be able to do their jobs with confidence and excellence as well, this will make the organization to work more efficiently and to achieve the goals in a professional and orderly manner. This will make the organization safer as well. However, Engineers in the aviation industry are affected as such limitations as well. Memory is the faculty in which the mind stores and remembers the information at a certain subject or multiple subjects. Aircraft maintenance engineers are always required to follow the proper procedures. However, in some cases engineers tend to rely on their memory due to their experience in a certain task, this mentality can lead to multiple scenarios that can affect the structural integrity of the aircraft that is undergoing maintenance. Such as, they sometimes have difficulty in remembering a certain procedure, this is usually caused due to stress. Stress is the high level of emotional arousal that is associated with an overload of mental and physical activity. Usually in the aviation industry, stress if often caused due to pressure on the engineer so that the work can be done much faster. A person may show signs of stress if he/she feels nausea/headaches, restlessness, poor concentration and forgetfulness. Engineers suffer consequences if they are under stress, since they can make poor judgements, lower standards of accepting work, forgetting the procedural steps and lack of situational awareness. Aviation maintenance engineers or technicians are most likely to make mistakes in their work when they are Fatigued. Fatigue is evident due to the lack of sleep of the engineer, according to FAA the average sleep of an AME is just 5 hours and 5 minutes compared to the recommended eight hours per day. This lack of sleep contributes to multiple mistakes or accidents that may have occurred in the aviation industry. FAA has applied a FRMS or Fatigue Risk Management system in order for engineers to be able to do their task well and to avoid and manage the risk of fatigue related accidents The first step in managing errors is to understand the nature of the errors which occurs and the casual mechanisms behind them, to provide a solution for managing the errors is to have systematic improvements. This includes improving the working conditions, procedures and knowledge in order to reduce the occurrence of error and to improve error detection, to adopt this improvements it requires a global, organizational approach to error management rather than focusing on the individuals who committed the errors. Error Management in the aviation industry is handled by the SMS or Safety Management System is a series of defined, organization-wide processes which provides an effective risk-based decision in the day to day tasks in the aviation industry. The SMS is focuses in maximizing the opportunities to improve the overall safety of the aviation system.

According to the Royal Aeronautical Society, it has codes that are reproduced in RAeS Part A and Part B and is varied and replaced from time to time by the regulations made in accordance with By-Law 5. Ethical practices that the RAeS are:

1. Accuracy and Rigour
2. sustainability Honesty and Integrity
3. Respect for life. Law and the public good
4. Responsible leadership: Listening and informing

The Engineering Council in association with the RAeS has stated the 4 elements of Ethicial principle sin which they believe all engineers and technicians should abide. The professional engineers and technicians should implement this in order to improve their welfare, health and safety of all. Whilst paying due regard to the environment and the of such resources. They have made personal and professional commitments in enhancing the wellbeing of society and thus through the exploitation of knowledge this will allow the members to aspire in their working habits and relationships through it guiding them in meeting the UKSPEC requirement in order to exercise such responsibilities in an ethical manner. The 2 Legislations that RAeS members should follow are:

The Part A Code of Conduct is applied to all Society members and are expected to:

1. Observe the provision of the By-Laws and the Charter of the Society and any regulations which are made under them and so that they would conduct themselves as to uphold the reputation. Standing and the dignity of he society and the members.
2. Treat with courtesy, whether it is in person on the telephone or by the letter or email that is through any means of communication. Society members should be respectful at all times.
3. Behave in Society premises and Events.
4. Pay membership dues by the By-Laws.
5. Accept that no member may speak for the Society on its behalf without a agreement or authority from the board.
6. Abide by the Code of Professional Conduct set out in Part B in the discharge of their professional duties.

The breaches of the code is considered in accordance with the regulations that is made by the board. The Part B Code of Professional Conduct of the society places a personal obligation on its members to act with the integrity and in the public interest. When discharging the professional duties, the members of the RAeS should:

1. Act with due skill, care and diligence and with proper regard for professional standards.
2. Prevent any danger that affects the safety and health of any of the members
3. Act accordingly with the principles of sustainability and prevent avoidable adverse impact on the environment and society.
4. Maintain their competence, undertake only professional tasks for which they are competent and disclose any relevant limitations of competence.
5. The acceptance of the appropriate responsibility for work that is carried out under their supervision.
6. Treat all persons fairly with high respect, and encourage others to have an advance learning and competence.

Error Management in the Aviation Industry has 5 Strategies:

- Prevention - Prevention of errors aims to avoid the error completely by providing systems to counteract errors that may occur during a certain condition
- Reduction - Reduction of errors minimizes the likelihood and the magnitude of the error itself. A perfect example for reducing is by applying good ergonomics in the cockpit design to reduce the errors and overall, the design of the aircraft.
- Detection - Detection of errors aims to make the errors as apparent as possible in order to fix the errors that have been made.

- Detected by the person who committed the error
- Detected by co-worker
- Detected by System Hardware

- Recovery - Recovery of error is achieved by making the system to recover to its safe state after the error has been committed.
- Tolerance - aims at making the system to better able to sustain itself despite the errors. Management of Errors is important as it provides a more informed decision making in an organizational level, improves the safety by reducing the risk of accidents, It provides better resource allocation which will result in an increase in efficiency and reduced costs and strengthens the Organization as a whole. The management of errors or the Safety Management System helps in providing the essential hazards and risks that impacts the whole organization which in turn manages the risk. Shown below is the Gantt Chart of the Structural Reliability and Analysis of Turbine Blades Project.

CHAPTER-2 PROJECT MANAGEMENT

Tasks related to Expected Gantt chart

In order for the project to go through as expected it to be, we have to generate a Gantt Chart. The project “Structural Reliability and Analysis on Turbine Blades” revolves on 10-week project outline. Where each week consists of multiple tasks to be accomplished within the specific time period. A Gantt Chart poses a complex data analysis that evolves charts and diagrams. However, this provides an idea to dive the tasks at hand into constituent section in order easily finish them and allocating the time. The tasks will be based on the weeks. The tasks that have generated for “Structural Reliability and Analysis of Turbine Blades” are:

Project Task 1

In the first task of the project, I have to create a Preliminary Research based on the Turbine Blades. The preliminary research was based on the company Roll-Royce which provides high bypass turbo fans commonly known as the Rolls Royce Trent Engine Series. Objectives generated from this research were, Extensive Research, Understanding Turbine Blades, Solution of increasing the service life of a turbine blade, Cost Analysis, producing a 3D Model for Ansys Simulation, Structural Reliability Analysis, Blade Root Analysis, Cyclic Fatigue Analysis, Airline and Manufacturer Business Study and Reliability of Turbine Blades.

Project Task 2

The second task of tasks consists of the Proposal, Research on the Trent Series Engine and Turbine Blade Research. The creation of the proposal was easy due to the fact that the preliminary research gave us the necessary objectives and outline on how the project would undergo.

Project Task 3

The third task of the Structural Reliability and Analysis of Turbine Blades consists of Airline and Rolls Royce Business Study, Turbine Blade 3D modeling of Rolls Royce Trent 7000 and the Material Research of Turbine blades and the feasibility study. The feasibility study contributes on how the project’s viability as a whole.

Project Task 4

The fourth task of the project revolves on the ANSYS simulation for the Rolls Royce Trent 7000.

Project Task 5

The 5th task Revolves on the Trent 700 and 7000 Simulation for further Comparison which Turbine Blade is better. This will allow us to have a reliability analysis on the turbine blades. The formulas for the turbine blade will contribute to the feasibility of the project itself.

Project Task 6

This task focuses on the Blade Root Research of Turbine blades, this goes in depth on the different blade roots and which one is better suited for the Project Scenario.

Project Task 7

Fatigue and Cyclic Fatigue Analysis revolves on how the problem occurs on turbine blades, how this type of corrosion will lead to detrimental effects on the aircraft itself on its 20,000th cycle. The aerodynamic analysis covers on the Computational Fluid Dynamics of the Gas Turbine Engine and how it affects turbine blades.

Project Task 8

An overall analysis of the Turbine Blade Design of the Rolls Royce Trent 7000 would be conducted on why this is the most optimal turbine blade to be used.

Project Task 9

By conducting all of the tasks at hand this will allow me to compile all of the information necessary to formulate the Project Report at hand and finish the entirety of the report. I will be then reviewing all of the information in the Project Report for finalization.

Project Task 10

The final task covers the Presentation of the entirety of the Project to the Project supervisor and would be submitting the project report for review.

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