Steam Turbine(impulse).pptx

Description of impulse steam turbine

1. Steam Turbine (Impulse)

2. Contents 1 . Introduction 1.1 . Definition 1.2 . Working principle with the help of diagram 1.3 . Application 1.4 . Terms used in your Titles 2 . Main components with clarification 3 . Design consideration 4 . Velocity diagrams with mathematical equation 5 . Derivation of Euler’s equation and work done 6 . Performance characteristics

3. 1. Introduction A steam turbine is a device that converts the thermal energy of pressurized steam into mechanical work by expanding high pressure and high temperature steam . The uniform speed of steam turbine at wide loads makes it suitable for coupling it with generators, centrifugal pumps, centrifugal gas compressors, etc…

4. 1.1. Definition Steam Turbine is a power generating machine in which the potential energy of the steam is transformed into kinetic energy and later in its turn is transformed into the mechanical energy of rotation of the turbine shaft. This conversion of energy is due to the dynamic action of the steam flowing over the blades.

5. Classification of steam turbines Steam turbines are classified in to impulse turbine and reaction turbine (or impulse reaction) Examples of impulse turbine includes De Laval, Curtis, Moore, Zoelly , Rateau , etc… Examples of r eaction turbine includes Parson, Ljungstrom , etc…

6. Impulse Turbines Impulse means sudden tendency of action without reflexes. In simple impulse steam turbine, the expansion of steam takes place in one set of nozzles. High pressure steam at boiler pressure enters the nozzle and expands to law back pressure (condenser pressure) in the nozzle. Thus, the pressure energy is converted in to kinetic energy increasing the velocity of steam and directed on a series of blades. Blades: are a components where the kinetic energy is partialy absorbed and converted in to an impulse force by changing the direction of flow of steam without changing its pressure due to their shape. The pressure at the outlet side of the blade is equal to that at the inlet side. Such turbine is termed as impulse turbine.

7. 1.2. Working principle of impulse turbines The working principle of a steam turbine impulse involves several key components and stages:

8. Steam Inlet Fixed Blades (Nozzle Diaphragm ) Moving Blades (Rotor Blades ) Rotor Rotation Steam Exit Steam Inlet : Pressurized steam enters the turbine through the inlet . Fixed Blades (Nozzle Diaphragm ) : The steam passes through a series of fixed blades or nozzles, where its pressure energy is converted into high- velocity kinetic energy. This is the stage where the impulse force is generated .

9. Moving Blades (Rotor Blades) : The high-velocity steam jets are directed onto a set of rotating blades. These moving blades are attached to the rotor and are crucial for the conversion of kinetic energy into mechanical energy . Rotor Rotation : The impulse force from the high-velocity steam causes the rotor blades to rotate. This rotation is the source of mechanical energy . Steam Exit : After passing through the moving blades, the steam exits the turbine . In some cases, it may be condensed and recycled back into the boiler for reheating. The pressure drop of the steam occurs primarily in the nozzles, while the pressure across the moving blades remains constant. This characteristic maintains relatively high steam pressure throughout the turbine, contributing to the efficiency of energy conversion.

10. Fig. Working principle of impulse steam turbine

11. 1.3. Application of impulse turbine Steam turbine impulse technology finds application in various industries and sectors due to its efficiency and reliability. Some common applications include : Power Generation : Impulse turbines are widely used in power plants to generate electricity. They are employed in small-scale power plants, combined heat and power (CHP) systems, and decentralized power generation units. Impulse turbines are particularly suitable for applications where high-speed rotation is required . Industrial Processes : Many industrial processes require mechanical energy for various operations. Impulse turbines can provide the necessary power for driving pumps, compressors, fans, and other equipment in industries such as oil and gas, chemical, petrochemical, and manufacturing.

12. Marine Propulsion : Impulse turbines are used in marine propulsion systems , especially in smaller vessels. They provide the necessary power to drive the propellers and enable the movement of ships, boats, and submarines. Cogeneration Systems : Impulse turbines are often integrated into cogeneration systems, also known as combined heat and power (CHP) systems . These systems simultaneously produce electricity and useful heat, maximizing energy efficiency. Impulse turbines play a crucial role in converting steam energy into mechanical energy for electricity generation . Renewable Energy : Impulse turbines can be employed in renewable energy systems , such as biomass power plants or concentrated solar power (CSP) plants . These turbines convert the thermal energy from steam generated by renewable sources into mechanical energy for electricity generation.

13. 1.4. Terms There are several important terms used in the context of steam turbines. Here are some key terms: - Blade - Steam Exhaust - Nozzle - Governor - Rotor - Condenser - Stator - Efficiency - Steam Inlet Blade, Nozzle, Rotor, Stator, Steam Inlet, and Steam Exhaust are clarified in the topic “components of the impulse steam turbine”.

14. Governor: The governor is a control system that regulates the speed and output of the steam turbine. It adjusts the steam flow rate to maintain a constant speed or to respond to changes in power demand. Condenser : The condenser is a heat exchanger that cools and condenses the steam exiting the turbine. It converts the steam back into liquid form, allowing it to be recycled and reused in the boiler . Efficiency : Efficiency refers to the ratio of the useful work output of the steam turbine to the energy input from the steam. It is an important measure of the turbine's performance and is typically expressed as a percentage.

15. 2. Main components of impulse turbine The main components of a steam turbine impulse include : - Nozzles (Fixed Blades ) - Stator - Moving Blades (Rotor Blades ) - Steam Inlet - Rotor - Steam Exhaust Nozzles (Fixed Blades ): Nozzles are the stationary components of an impulse turbine. They are designed to convert the pressure energy of the steam into high-velocity kinetic energy. The steam passes through these nozzles, which accelerate the steam flow and generate an impulse force . Moving Blades (Rotor Blades ): Moving blades are the rotating components of an impulse turbine. They are attached to the rotor and are responsible for extracting the kinetic energy from the high-velocity steam jets. The impulse force from the steam causes the moving blades to rotate, converting the kinetic energy into mechanical energy .

16. c. Rotor: The rotor is the central rotating component of the impulse turbine . It consists of a shaft and a set of moving blades attached to it. The rotor rotates as a result of the impulse force generated by the steam flow . The rotation of the rotor is what generates the mechanical energy output of the turbine . d. Stator : The stator is the stationary part of the impulse turbine. It includes the fixed blades (nozzles) and other stationary components that guide and control the steam flow. The stator ensures that the steam flow is directed onto the moving blades in an optimal manner, maximizing energy conversion. e. Steam Inlet : The steam inlet is the point where pressurized steam enters the impulse turbine. It is typically connected to the steam source, such as a boiler. The steam inlet provides the high-pressure steam necessary for the operation of the turbine.

17. f. Steam Exhaust : The steam exhaust is the point where the steam exits the impulse turbine after passing through the moving blades. Depending on the application, the steam may be condensed and recycled back into the boiler for reheating or used for other purposes.

18. 3. Design consideration The design of a steam turbine impulse involves several key considerations to ensure optimal performance and efficiency. Some important design considerations include: Blade Profile and Geometry : The design of the blades, both fixed (nozzles) and moving, is crucial for efficient energy conversion. The blade profiles and geometries are carefully designed to maximize the impulse force and minimize energy losses due to friction and turbulence. The shape, angle, and spacing of the blades are optimized to achieve the desired steam flow characteristics and energy extraction . Steam Flow Path : The design of the steam flow path is critical for efficient energy conversion. The flow path should be designed to minimize pressure losses, turbulence, and flow separation. Smooth and streamlined flow passages are essential to ensure that the steam flows smoothly and uniformly through the turbine, maximizing energy extraction .

19. Material Selection : The selection of materials for the turbine components is important to ensure durability, reliability, and resistance to high temperatures and pressures. The materials should have high strength, good corrosion resistance, and thermal stability. Common materials used for turbine blades include stainless steel, nickel-based alloys, and titanium alloys. Rotor Dynamics : The design of the rotor and its support system must consider the dynamic behavior of the rotating components. Rotor dynamics analysis is performed to ensure that the rotor operates within safe limits, avoiding excessive vibrations, stresses, and potential failures. Proper balancing and alignment of the rotor are crucial to minimize vibrations and ensure smooth operation . Efficiency and Performance : The design of the impulse turbine aims to maximize efficiency and performance. This involves optimizing the blade profiles, steam flow path, and other design parameters to achieve the highest possible energy conversion efficiency. Computational fluid dynamics (CFD) simulations and performance modeling are often used to analyze and optimize the turbine design.

20. Control and Regulation : The design of the control and regulation system is important for maintaining stable operation and responding to changes in load demand. The turbine should be equipped with a reliable governor system that can adjust the steam flow rate to match the power requirements. Proper control mechanisms ensure efficient operation and prevent overspeed or underspeed conditions . Maintenance and Serviceability : The design should consider ease of maintenance and serviceability. Access to critical components, such as blades and bearings, should be convenient for inspection, repair, and replacement. Design features that facilitate maintenance and minimize downtime contribute to the overall reliability and availability of the turbine.

21. 4. Velocity diagrams with mathematical equation In a steam turbine impulse, the velocity diagram is a graphical representation that illustrates the velocity changes of the steam as it passes through the turbine stages . The figure below shows a rotor blade with separate inlet and outlet velocity triangles

22. Due to expansion of steam in nozzles, steam issues with an absolute velocity at an angle with the plane of the moving blades. If the blade peripheral velocity is u , then the relative velocity of steam with respect to the casing is . For smooth surfaced blades, friction losses are small or zero, hence,

23. Fig. Combined velocity diagram

24. 5. Derivation of Euler’s equation and work done The Euler turbine equation relates the power added to or removed from the flow, to characteristics of a rotating blade row. The equation is based on the concepts of conservation of angular momentum and conservation of energy. We will work with the model of the blade row shown in Figure below Control Volume for Euler Turbine Equation

25. Applying conservation of angular momentum, we note that the torque, Angular momentum is moment of linear momentum of angular velocity, For a steady flow through a turbomachine: The Rate of angular momentum at inlet: Rate of angular momentum at exit : Rate of change of angular momentum: This is known as Euler’s Turbomachinery Equation

26. 6. Performance characteristics The performance characteristics of a steam turbine impulse refer to the key parameters that describe its efficiency, power output, and operating conditions . Some important performance characteristics of a steam turbine impulse include: - Efficiency - Power Output - Specific Steam Consumption - Load Variation Capability - Reliability

27. Efficiency: The efficiency of a steam turbine impulse is a measure of how effectively it converts the thermal energy of the steam into mechanical work . It is typically expressed as a percentage and calculated by dividing the actual mechanical work output by the energy input from the steam . Factors that affect turbine efficiency include steam conditions, blade design, and losses due to friction and leakage . Blading or rotor or vane efficiency :

28. Power Output : The power output of a steam turbine impulse is the amount of mechanical work it produces per unit time . It is typically measured in kilowatts (kW) or megawatts (MW ). The power output depends on the steam flow rate, steam pressure, and steam temperature, as well as the turbine's design and efficiency . Increasing the steam flow rate or operating at higher steam pressures and temperatures can increase the power output . Nozzle efficiency :

29. Specific Steam Consumption (SSC): Specific steam consumption (SSC) is a measure of the steam required by the turbine to produce a unit of power output. It is typically expressed in kilograms of steam per kilowatt-hour (kg/kWh) or pounds of steam per horsepower-hour ( lb / hp-hr ) Lower SSC values indicate better steam utilization and higher efficiency . Load Variation Capability : The load variation capability of a steam turbine impulse refers to its ability to operate efficiently and maintain stable performance under varying power demands. Turbines with good load variation capability can quickly respond to changes in load without significant efficiency losses or operational issues.

30. Reliability: The reliability of a steam turbine (impulse) refers to its ability to operate continuously and reliably over an extended period without significant failures or breakdowns. Factors such as material selection, rotor dynamics, and control systems contribute to the reliability of the turbine. These performance characteristics are essential for designing , optimizing, and selecting the appropriate turbine for specific applications by evaluating the efficiency, power output, and operational capabilities of a steam turbine impulse.

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32. Group Members ID N o 1. Brhane Gebrewahd …………….. EITM/UR158122/11 2. Gebreyohans Abera ……………. EITM/UR158106/11 3. Haile Gebreselassie ……………. EITM/UR158134/11 4. Huluf Syum ……………………. EITM/UR158079/11 5. Alem Dejen …………………….. WBU103446/10 Section: 02