Case Study On Manufacturing And Repair

Published Date: 02 Nov 2017

Term Project submitted in partial fulfillment of the requirements for the module

MT5612 – COMPUTER AIDED PRODUCT DEVELOPMENT

SEMESTER-2

2012

Approved by

(Assoc. Prof. Lu Wen Feng)

Date

ABSTRACT:

A turbine blade is one of the main components which make up the turbine engine. A Turbine blade design and manufacturing is a complicated process, as the machining is to be very precise in order to be effective, more efficient and quality in turbine operation. This paper is concerned over the comparison of different stages in design and manufacturing of turbine blade technology with typical case studies, also including the cost factor and repair and remanufacturing technique with its advantages and limitation. This paper also provides a typical technology roadmap of the turbine blade including its future advances

Introduction to Turbines :

The needs of industrial nations for electrical power and for modern air, land, and sea transportation increases steadily. Consequently, more powerful and more efficient energy conversions systems, specifically steam turbines, jet engines, and stationary gas turbines

are required in ever increasing quantities. Thus, extremely large quantities of blades of

Various geometries must be produced from various materials. A large number of these blades are either forged with an envelope, or they are precision forged

Turbine is one of the innovative design evolved during the second world war. Turbine had taken shape in various application with aeronautics, Power generators, Sports cars. The turbine is divided into three main parts compressor, combustion chamber & exhaust ( or driving segment)

http://www.allstar.fiu.edu/aero/images/turbo2.gif

 That turbine section is connected to a compressor section. Air is compressed in the compressor which raises the pressure and temperature of the air. As the air passes through the mid fuel injection section where the gasoline or similar fuel is sprayed, the pressure and temperature are then greatly increased by combustion of fuel inside the combustor where the fuel is ignited, The combusted gas will be at a very high temperature and pressure which will pass through the turbine stage, The gas with high kinetic energy and temperature will hit the turbine blade, thereby transferring its kinetic energy by which the blade will be forced to rotate, this indeed is the prime driving force that runs every turbines around the world. The number of turbine stages varies in different types of engines, with high bypass ratio engines tending to have the most turbine stages Many gas turbine engines are twin spool designs, meaning that there is a high pressure spool and a low pressure spool. Other gas turbines used three spools, adding an intermediate pressure spool between the high and low pressure spool.

The advanced aero-engine materials such as superalloys, titanium and its alloys, alloys of nickel with aluminum, stainless steel found wide application in the turbine parts manufacturing. The novel structural materials as well as the jet-engine components after their surface layer modification are harder and harder to machining. The turbine components such as: the turbine blades, turbine vanes, turbine vane rings, turbine nozzles (vane segments), engine and turbine casings needs employing the advanced manufacturing technologies and the modern machine tools and equipment, the suitable cutting and abrasive tools as well as appropriate CNC control systems and software. The difficult-to-machine materials used in aviation and space engineering require especially the new technology of machining and the suitable tools and the machine tools implementation to increase grinding capacities, to lower manufacturing costs per piece, to secure reproducibility of the products quality and to secure the safe conditions of work for an operator. Technologies of the turbine components manufacturing comprise: broaching, milling, grinding with the grinding wheels, grinding with the abrasive belts, deburring with the abrasive brushes and unconventional technologies in the turbine blades and blisks machining (Abrasive Water Jet Machining – AWJM, Abrasive Flow Machining – AFM, Electro-Chemical Machining – ECM, Electro-Discharge Machining – EDM).

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In a precision forged blade, the air foil surface is not machined after forging; thus, the fiber structure is maintained and improved fatigue, corrosion and erosion properties are obtained. (I) In using precision forged blades, machining is reduced to a minimum. Therefore, savings are made fn stock material, and it is not necessary to invest in special-purpose machining equipment. However, the precision forging process is relatively expensive, results in longer lead times, and requires a sophisticated process desiRn and close control of process variables. The design and manufacturing of precision forging dies require particular attention because the local shrinkage and elastic deflection of the dies must be known and the original die surface must be corrected accordingly, so that the airfoil of the forged blade is within specified tolerances.

In most forge plants, blade forging is still an art which requires extensive experience in die design and manufacture. Several companies, particularly Deutsche Edelstahl

In a newly built plant, Westinghouse Electric Corporation uses Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) techniques for die design and manufacture. The forging dies are made by EDM using NC machined graphite electrodes. (4)

Battelle's Columbus Laboratories has also developed, under Air Force sponsorship, computer

programs for designing and NC machining of blade forging dies.

Turbine blades:

A turbine blade is the key component in turbo jet engines and other gas turbines. The main function of the turbine blade is extraction of energy from the high temperature and high pressure combustion gases and converts into mechanical energy, which is the driving force of turbines. The efficiency of the aircraft jet engines mainly depends on the turbine blade efficiency and life, hence the design and manufacturing of turbine blades need more important as it withstands high thermal stresses and shock waves without any compromise in overall function. . The number of turbine stages can have a great effect on how the turbine blades are designed for each stage. The high pressure turbine is exposed to the hottest, highest pressure, air, and the low pressure turbine is subjected to cooler, lower pressure air. That difference in conditions leads the design of high pressure and low pressure turbine blades to be significantly different in material and cooling choices.

Technological Evolution

the design & manufacturing of turbine blades are categorized in to four stages of evolution, they are:

1st Generation (Early 1950s ~ 1980s)

2nd Generation(Mid 1980s ~ 2000)

3rd Generation (Early 2000 ~ Present)

4th Generation (Future)

1st GENERATION

in the early 19th centuary where the jet turbines are just invented, the turbine blades manufacturing is separated into two different categories with computer unavailable at that time, hence the process undergo painful process of design and manufacturing.

DESIGN

Design is very limited to paperwork and the engineers creativity, while the errors are frequent and unavoidable. Moreover the drafting part of the design took much of the manpower and cost, drafting personals need to be highly trained. The drawing produced undergo a through checking by a checker to identify the mistakes

MANUFACTURING PROCESS:

Turbine blades have a complex geometry and contain many areas of double curvature

The Traditional Design Process

The traditional design process accounts for 75% of total production costs. Traditional

design departmentalized as the engineers would develop the product design and any

working and detail drawings associated within the conceptual design [2]. The design is

then passed to other departments within the organization (manufacturing for process and

material selection, marketing, purchasing, etc.). The design may then be sent back to the

design team for rework and revision. The traditional design process tends to be

exceedingly tedious and resource inefficient. This tedious and inefficient nature can lead

to increased lead time and loss of profit. The following figure shows the product life

cycle of a typical product.

Parametric Blade design system:

Scope:

A complete 3-D Parametric Blade geometry design system for Air-craft design project applications is presented.

The system generates a 3-D free-form surface of an turbine blade by means

of individual definition of quasi 2-D stream surface blade profiles.

These profiles are then stacked relative to a reference point for each section along a so-called

"stacking line".

All design properties both for the quasi-2-D profiles and the 3-D stacking line are parameterized in a problem-adapted way to support the understanding of the aerodynamic engineer. These parameters are then transformed into a fully CAD-compatible B-spline representation.

The geometry engine is completed with CFD-code integration, a blade profile optimizing

package, a parametric database and a correlation utility to find good starting solutions for new

design tasks based on existing proven technology.

The complete design systems offers a number of project-related advantages to the user: the

system is fully integrated into gas turbine.

It offers a bi-directional data exchange between different design disciplines such as stress &

mechanical analysis, aerodynamics, checking of mechanical constraints, thermal analysis and

CAD-design for platform, root, shrouds etc.

The system is completed with optimisation strategies based on parametric free-form-solids

generation.

Part I

1. Introduction

2. Basic Principles of the design task

3. Outline on the major system components

4. Experiences with industrial applications

5. Parametric 3-D blade manipulations

6. Recommendations

Part II

1. Technical Details: geometry representation, optimisation, correlation rules, parametric

stacking

2. Curvature distribution

3. Standard profile properties

4. Cloning

5. System integration

6. Profile editor b2d

7. Implementation details

8. Graphical user interface

9. Integration into CAD/CAE environment

10.General remarks

Introduction

Blade design & gas turbine business

The gas turbine business has changed over the last five to ten years. In the seventies and eighties

a large number of advancement in physics-based technology programs were carried out, especially in Gas turbines.

These technologies had led to an essential reduction of design complexities and improved the cost situation for the airlines. In the nineties engine maker have put more emphasis on cost and quality issues.

On the other hand the cost competition has gradually changed into a time- and innovation

Competition (time based competition). Every player in the global aero engines market is trying to

find and strengthen its unique selling proposition to stay in the market and make profit with

reduced time-to-market and innovative engine concepts.

The main condition for that is for a single company to be able to design and certify the right

engine at the right time for the right application. Technology is still very important and will be

developed. But with limited resources, companies must re-think the cost benefit of certain purely

physics-based research programs of the past because further return of investment will be quite

low. „High tech" as the one and only unique selling proposition (USP) is not enough for today’s

customers, they assume it and demand reduced costs for the product as well.

That’s why companies have to focus efforts and technology programs on those things that impact

units cost most: reduction of hardware costs, design & re-design costs and reduction of expensive

test series by numerical simulation and concurrent simultaneous engineering.