This paper covers some of the common and relevant criteria that is considered by engineers when designing gas turbine engines. The thermodynamic and aerodynamic analyses of gas turbine engines is a very important topic in aerospace engineering. Engineers are constantly trying to achieve higher gas turbine efficiencies, by implementing various design configurations, experimenting with new materials, different material combinations, etc.
Table of Contents
Introduction
Gas turbine engine – introduction
Compressor
Centrifugal-flow compressor
Impeller (rotor)
Guide vanes
Diffuser vanes and casing
Axial-flow compressor
Multi-stage axial compressors
Stators and rotors
Engine pressure ratio
Pressure and temperature rise through the compressor
Airflow through the compressor
Stage power and work
Velocity triangles
Benefits vs drawbacks of axial compressors and centrifugal compressors
Gas turbine engine fan modules
High bypass turbofans
Low bypass turbofans
Turbofan fan blades – function and design
Turbofan fan disc – function and design
Turbofan fan casing – function and design
Turbine definition
Types of turbine
Impulse turbine
Reaction turbine
Impulse-reaction turbine
Basic turbine components
Casing
Exploring centrifugal and axial flow compressor thermo-fluid and aerodynamic principles
Boundary layer primary losses
Boundary layer secondary losses
Pressure loss coefficient
Axial-flow and centrifugal-flow compressors
Comparison of between impulse and reaction turbines
Compressor characteristics and performance
Multi-stage compressor stage matching
Overall pressure ratio against inlet mass flow and surge line
Compressor issues outside the operating limits
Compressor stall/surge
Blade stall and flutter
How compressor stall arises
Preventing stall and surge
Variations in absolute velocity
Velocity triangles for an axial-flow turbine stage
Fuel mass flow rate
Characteristic map tuning and efficiency contours
Turbine blades and nozzle guide vanes
Gas turbine disc and blade cooling
Nozzle guide vane (NGV) cooling methods
Safety improvement for compressors
Safety improvement for gas turbine fans
Safety improvement for turbines
Task 2
Aerodynamic performance of air intake sections
Intake types
Circular subsonic intake
Supersonic intakes
Axisymmetric supersonic intake
Rectangular supersonic intake (variable/fixed geometry)
Intake section design and performance
Intake section throat area in subsonic high bypass fan
Intake section throat area in supersonic high bypass fan
Gas turbine exhaust system
Exhaust nozzle
Thrust reversers
Afterburners
Convergent nozzle
Convergent-divergent nozzle
Thrust control and augmentation
Combustion systems
Combustor types and design
Multiple combustion chamber
Annular combustion chamber
Tubo-annular combustion chamber
Fuel nozzles
Fuel atomisation
Combustor performance
Diffuser performance
Combustion losses and efficiencies – performance criteria
Combustion efficiency
System pressure losses
Outlet temperature distribution
Combustion stability and light-up limits
Flame stabilisation – stability performance
Stability factors
Static stability
Dynamic stability
The reasons for instabilities occurring
Fuel types
Fuel-air ratio
Gas pressure, temperature and velocity variation
Airflow pressure variation
Airflow velocity variation
Airflow temperature variation
Flame-holder shape and size
Improving air intake performance
Improving combustion chamber performance
Improving exhaust performance
Conclusion
Bibliography
Research Goals and Thematic Focus
This work provides an in-depth thermodynamic and aerodynamic analysis of gas turbine engines, aiming to evaluate the performance of key components such as compressors, fan modules, and turbines while exploring material and design improvements for enhanced efficiency, stability, and safety.
- Detailed examination of compressor types including axial and centrifugal flow designs.
- Analysis of combustion systems, including fuel atomisation and stability under varying operating conditions.
- Evaluation of exhaust systems, specifically addressing thrust control, augmentation, and nozzle configurations.
- Investigation into advanced materials and cooling techniques for compressors, fans, and turbines.
- Study of aerodynamic performance in both subsonic and supersonic flight regimes.
Excerpt from the Book
Compressor
Gas turbine engines incorporate a compressor section that serves the function of increasing the incoming air pressure prior to the airflow entering the combustor. The combustor section is important because it’s the main section, or component, of a gas turbine engine that directly influences the total engine performance. As shown in the diagram below, there are two types of compressors, namely centrifugal and axial compressors. (grc.nasa.gov, 2015)
As a brief introduction, the centrifugal compressor causes the airflow to propagate perpendicularly to the axis of rotation, whereas the axial compressor causes the airflow to propagate parallel to the rotational axis. Centrifugal compressors aren’t utilised for large gas turbine engines anymore; they’ve been replaced by axial flow compressors. However, they’re still used on small turbojet and turboshaft engines, as well as pumps on rocket engines.
The main reason that axial flow compressors are used rather than centrifugal compressors is due to the fact that axial flow compressors achieve a higher pressure increase; centrifugal compressors increase pressure by a factor of 4, whereas axial flow compressors increase pressure by a factor of 4.3. (grc.nasa.gov, 2015)
Summary of Chapters
Gas turbine engine – introduction: Provides an overview of the role of the compressor section in gas turbine engines, differentiating between axial and centrifugal types.
Compressor: Details the specific mechanisms and design differences between centrifugal-flow and axial-flow compressors, emphasizing pressure rise and structural components.
Gas turbine engine fan modules: Discusses the classification of turbofans based on bypass ratio and describes the functions of fan blades, discs, and casings.
Turbine definition: Defines the turbine as a machine that transforms thermal energy into mechanical work and categorizes them into impulse and reaction types.
Basic turbine components: Examines essential turbine elements like casings, rotors, blades, and nozzles in the context of their operational requirements.
Exploring centrifugal and axial flow compressor thermo-fluid and aerodynamic principles: Analyzes boundary layer losses and the use of particle image velocimetry in studying flow phenomena.
Compressor issues outside the operating limits: Explores the causes and prevention of compressor stall and surge, focusing on the role of FADEC systems.
Combustor performance: Describes various combustor configurations and evaluates performance metrics such as combustion efficiency and temperature distribution.
Keywords
Gas turbine engines, Axial-flow compressor, Centrifugal-flow compressor, Turbofan, Combustion instability, Stall, Surge, Thrust augmentation, Afterburners, Cooling methods, Nozzle guide vanes, Brayton cycle, Aerodynamics, Thermodynamic analysis, Material science
Frequently Asked Questions
What is the fundamental purpose of this work?
The work aims to provide a comprehensive thermodynamic and aerodynamic evaluation of gas turbine engines, covering component behavior and suggesting design improvements.
What are the primary thematic areas covered?
The text focuses on compressors, fan modules, turbines, combustion systems, and exhaust systems, emphasizing their roles in performance and efficiency.
What is the central research question?
The research explores how aerodynamic performance parameters and material configurations can be improved to optimize efficiency and operational safety in gas turbine engines.
Which scientific methods are employed?
The analysis utilizes thermodynamic principles, such as the Brayton cycle and Bernoulli equation, alongside experimental data analysis like Particle Image Velocimetry (PIV).
What topics are discussed in the main section?
The main section covers component-level thermodynamics (compressors, fans, turbines), system losses (boundary layers, stall, surge), intake/exhaust design, and performance enhancement strategies.
What are the characterizing keywords of this work?
The key themes include jet engine aerodynamics, compressor stall dynamics, propulsion efficiency, and advanced composite cooling methods.
How is compressor stall managed in gas turbine engines?
Compressor stall is mitigated using FADEC systems, variable-pitch stators, inlet bleed operations, and advanced casing treatments to maintain stable operating conditions.
What distinguishes impulse turbines from reaction turbines?
Impulse turbines change the direction of fluid primarily through nozzle-driven reflection at high speeds, while reaction turbines extract energy by rotating along with fluid flow passing through multiple blade rows.
- Arbeit zitieren
- Abdusselam Šabić (Autor:in), 2021, Components and Subsystems of Gas Turbine Engines. A Detailed Analysis, München, GRIN Verlag, https://www.grin.com/document/1264839
