Turbine Engineering Principles
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What is the primary purpose of the nozzle guide vane in turbine systems?

  • To convert pressure energy to kinetic energy. (correct)
  • To regulate pressure while maintaining velocity.
  • To increase absolute velocity of the gas.
  • To provide structural support to the turbine blade.

    • What characteristic distinguishes reaction turbine blades from impulse turbine blades?

  • They convert pressure energy into kinetic energy. (correct)
  • They extract energy nearly uniformly along the blade.
  • They do not change the gas pressure.
  • They operate solely based on gas velocity.

    • In Impulse-Reaction turbine blades, what is the design feature at the blade tip aimed to achieve?

  • Maximizing work done by gas expansion.
  • Minimizing turbulence in the gas flow.
  • Generating high speed gas for enhanced performance. (correct)
  • Reducing aerodynamic drag on the blade.

    • Which statement best describes the principle of operation for impulse turbines?

    <p>They extract energy from kinetic energy through gas striking the blade.</p> Signup and view all the answers

    Which of the following describes a key feature of impulse-reaction blades?

    <p>They combine characteristics of both impulse and reaction blades.</p> Signup and view all the answers

    How does the reaction turbine blade affect the gas as it passes through?

    <p>It decreases both pressure and absolute velocity.</p> Signup and view all the answers

    What is the advantage of having a large number of holes arranged for impingement cooling?

    <p>To ensure efficient cooling of larger areas.</p> Signup and view all the answers

    Which aspect of impulse turbine blades does NOT change during operation?

    <p>Pressure of the gas.</p> Signup and view all the answers

    What role does the contour of a reaction blade play in its function?

    <p>It facilitates a change in gas pressure and velocity.</p> Signup and view all the answers

    What is the main function of the impulse shape at the root of the Impulse-Reaction blade?

    <p>To efficiently extract energy for work.</p> Signup and view all the answers

    What is the primary role of the Nozzle Guide Vane in turbine operation?

    <p>To guide the gas from the combustor to the turbine rotor</p> Signup and view all the answers

    Which stage is associated with the phenomenon of primary creep in turbine materials?

    <p>When the sample experiences permanent elongation</p> Signup and view all the answers

    What is the purpose of Turbine Case Cooling (TCC) in turbine operation?

    <p>To maintain blade tip clearance between the blades and casing</p> Signup and view all the answers

    In turbine mechanics, what does tertiary creep indicate?

    <p>Rapid elongation leading to mechanical failure</p> Signup and view all the answers

    What type of turbine blade design is primarily affected by creep?

    <p>Reaction blades</p> Signup and view all the answers

    Why is the clearance X important in turbine operation?

    <p>It prevents turbine blades from rubbing against the casing</p> Signup and view all the answers

    Which aspect is critical for ensuring the longevity of turbine blades under thermal and mechanical stress?

    <p>Understanding the phases of creep</p> Signup and view all the answers

    Which cooling method is utilized to manage the temperature of the turbine casing?

    <p>Air bleed from the compressor</p> Signup and view all the answers

    What are the implications of decreased blade tip clearance X in a turbine?

    <p>Increased risk of blades seizing against the casing</p> Signup and view all the answers

    Which of the following best describes 'secondary creep'?

    <p>Stable elongation with minimal changes</p> Signup and view all the answers

    What is the primary function of the nozzle guide vanes in a turbine stage?

    <p>To direct the gas flow towards the rotating blades</p> Signup and view all the answers

    In the context of turbine blade design, what characterizes impulse-reaction blades?

    <p>They combine both impulse and reaction principles for energy conversion.</p> Signup and view all the answers

    Which statement best describes the mechanics of a reaction turbine?

    <p>Both the rotor and stator perform work on the fluid to transform energy.</p> Signup and view all the answers

    What distinguishes an impulse turbine from other turbine types?

    <p>The total pressure drop occurs across the nozzle guide vanes only.</p> Signup and view all the answers

    Which of the following describes a key characteristic of impulse blades?

    <p>They produce thrust primarily through change in velocity.</p> Signup and view all the answers

    What is the primary disadvantage of using reaction blades in turbine design?

    <p>They are more susceptible to thermal fatigue.</p> Signup and view all the answers

    How does the design of a nozzle guide vane affect turbine performance?

    <p>It optimizes the conversion of kinetic energy into useful work.</p> Signup and view all the answers

    What role does the cooling process play for turbine blades?

    <p>It allows the blades to maintain structural integrity at high temperatures.</p> Signup and view all the answers

    What is the main advantage of using film cooling for turbine blades?

    <p>It creates a barrier that reduces thermal loading on the blade surface.</p> Signup and view all the answers

    What transformation occurs as gas flows through stationary vanes in a turbine stage?

    <p>Pressure is converted into velocity.</p> Signup and view all the answers

    Which of the following is NOT a mechanical stress experienced by turbine blades?

    <p>Oxidation.</p> Signup and view all the answers

    In film cooling, what is created to lower the effective gas temperature?

    <p>An insulating sublayer.</p> Signup and view all the answers

    What cooling method directs a high-velocity cold air jet onto the turbine component?

    <p>Impingement cooling.</p> Signup and view all the answers

    Which type of turbine blade is primarily designed to convert kinetic energy of the gas into mechanical energy?

    <p>Impulse blade.</p> Signup and view all the answers

    What primarily characterizes the load experienced by a turbine blade in operation?

    <p>Substantial thermal gradients.</p> Signup and view all the answers

    What distinguishes the type of cooling using forced convection in turbine systems?

    <p>Directed high-velocity air streams.</p> Signup and view all the answers

    Why is blade attachment critical in turbine design?

    <p>It prevents mechanical failure due to load.</p> Signup and view all the answers

    What factor primarily defines the material selection for turbine blades?

    <p>Resistance to thermal cycling and creep.</p> Signup and view all the answers

    What is the role of nozzle guide vanes in the turbine stage?

    <p>To reduce fluid velocity before entering the rotor.</p> Signup and view all the answers

    What occurs during tertiary creep in turbine materials?

    <p>Rapid elongation leading to failure</p> Signup and view all the answers

    What is the expected outcome of decreased blade tip clearance X due to creep?

    <p>Increased risk of blade failure</p> Signup and view all the answers

    Which description best characterizes the behavior of the secondary creep phase?

    <p>A flat curve indicating minimal elongation</p> Signup and view all the answers

    What is the role of Turbine Case Cooling (TCC) in maintaining turbine function?

    <p>To manage blade tip clearance effectively</p> Signup and view all the answers

    In the creep behavior of metals, what happens after the primary creep phase?

    <p>The elongation stabilizes and becomes negligible</p> Signup and view all the answers

    How does the nozzle guide vane influence kinetic energy in turbines?

    <p>It redirects gas flow to enhance kinetic energy</p> Signup and view all the answers

    What is the primary function of the Impulse-Reaction blade design?

    <p>To combine high impact power generation with high-speed gas production</p> Signup and view all the answers

    Which factor primarily determines a metal's resistance to creep?

    <p>Measured elongation under mechanical and thermal stress</p> Signup and view all the answers

    How does the shape of a Reaction blade specifically influence gas behavior?

    <p>It creates a convergent duct that lowers both pressure and velocity</p> Signup and view all the answers

    What is the main cause of turbine blades rubbing against the casing over time?

    <p>Reduction in blade tip clearance due to creep</p> Signup and view all the answers

    Which of the following describes the impact of gas striking an impulse blade?

    <p>It extracts high impact energy without changing pressure</p> Signup and view all the answers

    What is typically released during the Turbine Case Cooling (TCC) process?

    <p>Cool air from atmosphere or compressor bleed air</p> Signup and view all the answers

    What happens during the 'primary creep' stage?

    <p>The elongation process begins and becomes permanent immediately</p> Signup and view all the answers

    What characteristic of the Impulse blade contributes to its efficiency in converting gas energy?

    <p>The center of gravity where gas impacts the blade</p> Signup and view all the answers

    What distinguishes the aerodynamic action of Reaction turbine blades from Impulse turbine blades?

    <p>Reaction blades generate their turning force from blade contour</p> Signup and view all the answers

    What is a common principle governing the design of turbine blades in terms of cooling methodology?

    <p>To arrange numerous holes to facilitate impingement cooling</p> Signup and view all the answers

    Which aerodynamic principle is crucial for achieving high-speed gas output from an Impulse-Reaction blade?

    <p>The variable velocity across blade roots and tips</p> Signup and view all the answers

    What effect does maintaining a high impact power generation in turbine efficiency have?

    <p>It allows for better fuel efficiency and system performance</p> Signup and view all the answers

    What role does the design shape at the blade tip of an Impulse-Reaction blade play?

    <p>It facilitates high-speed gas flow while reducing absolute velocity</p> Signup and view all the answers

    Study Notes

    Turbine Section

    • This chapter covers various aspects of turbine sections, specifically focusing on mechanical and aeronautical engineering principles.

    Introduction

    • Facts on Turbine Stage: Details aspects of turbine assembly, load on turbine blades, and materials used. Different cooling methods (multi-pass, film, and impingement) are also mentioned.
    • Types of turbine blades: Impulse blades, reaction blades, and impulse-reaction blades are discussed.
    • Creep: Describes the behavior of materials under prolonged stress and high temperature.
    • Turbine Case Cooling (TCC) / Active Clearance Control (ACC): Methods for managing blade attachment and maintaining turbine technology are detailed.
    • Blade attachment: Explains fir tree attachment.

    Facts on Turbine Stage

    • Function: The turbine transforms gas kinetic energy into mechanical energy to drive compressors and related machinery. This is done through a series of stationary and rotating components.
    • Stage Components: A turbine stage includes stationary vanes (or nozzle guide vanes) and rotating blades (or rotor).
    • Gas Flow: Gas from the combustion chamber first passes through stationary vanes, converting some pressure to velocity, then flows through the turbine blades where mechanical forces cause the wheel to rotate.

    Turbine Assembly

    • Diagrams illustrate various aspects of turbine assembly, showing turbine vanes, rotors, and cross-sections.

    Load on Turbine Blade

    • Turbine blades experience mechanical forces, creep, thermo-mechanical fatigue, high temperatures, oxidation, and hot corrosion.

    Material Used on Turbine

    • Materials like titanium, nickel, steel, aluminum, and composites are used in turbine components. A diagram shows different materials used in a typical engine.

    Material Strength vs. Temperature

    • The graph demonstrates how the specific strength of different metals varies with temperature, providing insights into material selection for different parts of the turbine.

    Turbine Blade Cooling

    • Different cooling methods (multi-pass, film, and impingement) are presented, highlighting their functionality and effectiveness.

    Multi-pass Cooling

    • Diagrams show the application of different cooling methods using low-pressure (L.P.) and high-pressure (H.P.) cooling air.

    Film Cooling of Turbine Blades (Conduction)

    • Principle: This method draws cooling air from the compressor creating an insulating layer, to lower the effective gas temperature in the boundary layer.
    • Different designs and application examples using film cooling are illustrated in diagrams.

    Impingement Cooling (Forced Convection)

    • Method: High-velocity cold air jets directed onto the component surfaces.
    • Diverted in different directions to ensure effective cooling and prevent overheating/seizing.
    • Impingement jet arrays are shown in a diagram.

    Turbine Blade Cooling

    • Overview of different cooling principles (film, impingement) used in turbine blade designs.
    • These methods are essential for maintaining blade integrity under extreme operating conditions.

    Types of Turbine Blades

    • Impulse, reaction, and impulse-reaction blades.

    Facts on Impulse Turbine Blade

    • Method: Extracts kinetic energy of the gas to do work for accessories.
    • The gas strikes at the center of the blade.
    • Pressure does not change but the velocity does.
    • Impulse blade diagrams are shown schematically.

    Facts on Reaction Turbine Blade

    • Method: Produces turning force by aerodynamic action—using a blade's contour.
    • Pressure decreases through passage; velocity increases; gas is used for turbine rotation.
    • Reaction turbine diagrams show characteristic changes in pressure and velocity.

    Facts on Impulse-Reaction Turbine Blade

    • Design combination of both impulse and reaction blade types.
    • Employed to achieve both high-impact power and high-gas velocity by utilizing the blade tip shape for high-speed gas generation.

    Facts on Nozzle Guide Vane

    • Role: Guides gas from the combustor to the first-stage turbine rotor.
    • Function: Converts pressure energy into kinetic (velocity) energy to enhance the efficiency of turbine rotor operation.
    • Diagram of a nozzle guide vane is provided.

    Creep/Turbine Case Cooling/Blade Attachment/Turbine Technology

    • Creep: A material property.
    • Describes the time-dependent permanent deformation of materials under constant (or gradually changing) stress at elevated temperatures. Three zones of creep (primary, secondary and tertiary) are shown in figures.
    • Consequences: Turbine blade clearance reduction, potential blade damage, and casing issues are some of the consequences.
    • TCC/ACC: Methods for active clearance control.
    • The principle and applications of different cooling methods, and the design considerations to manage the consequences of creep are explored.

    Fir Tree Attachment

    • Diagram of a blade attachment type used in turbines.

    Turbine Technology

    • Advantages: Explains advantages and discusses the latest turbine technology.
    • Different blade design, component characteristics, and cooling designs are included.

    Recap

    • Purpose of turbine sections,
    • Stresses on turbine blades,
    • Cooling methods,
    • Materials,
    • Types of turbines,
    • Blade attachment examples,
    • Creep characteristics and effects,
    • Turbine technology.

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    Chapter 5 Turbine Section PDF

    Description

    Explore the fundamentals of turbine sections in mechanical and aeronautical engineering. This quiz covers turbine assembly, types of blades, material behavior under stress, and advanced cooling methods. Test your knowledge of turbine technology!

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