Turbomachinery
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Turbomachinery, in
These two types of machines are governed by the same basic relationships including
History
The first turbomachines could be identified as
The first impulse type turbine was created by Carl Gustaf de Laval in 1883. This was closely followed by the first practical reaction type turbine in 1884, built by Charles Parsons. Parsons’ first design was a multi-stage axial-flow unit, which George Westinghouse acquired and began manufacturing in 1895, while General Electric acquired de Laval's designs in 1897. Since then, development has skyrocketed from Parsons’ early design, producing 0.746 kW, to modern nuclear steam turbines producing upwards of 1500 MW. Furthermore, steam turbines accounted for roughly 45% of electrical power generated in the United States in 2021.[4] Then the first functioning industrial gas turbines were used in the late 1890s to power street lights (Meher-Homji, 2000).
Classification
In general, the two kinds of turbomachines encountered in practice are open and closed turbomachines. Open machines such as
Turbomachines are also categorized according to the type of flow. When the flow is parallel to the
Turbomachines may be further classified into two additional categories: those that absorb energy to increase the
machine type → group ↓ |
machinery | combinations of power and machinery | engines |
---|---|---|---|
open turbomachine | propeller | wind turbines | |
hydraulic fluid machinery (≈ incompressible fluids) |
fans |
) | water turbines |
thermal turbomachinery (compressible fluid) |
compressors |
gas turbines (inlet consists of a compressor) |
steam turbines turbine jet engines |
Turbomachines
Definition
Any device that extracts energy from or imparts energy to a continuously moving stream of fluid can be called a turbomachine. Elaborating, a turbomachine is a power or heat generating machine which employs the dynamic action of a rotating element, the rotor; the action of the rotor changes the energy level of the continuously flowing fluid through the machine. Turbines, compressors and fans are all members of this family of machines.[6]
In contrast to positive displacement machines (particularly of the reciprocating type which are low speed machines based on the mechanical and volumetric efficiency considerations), the majority of turbomachines run at comparatively higher speeds without any mechanical problems and volumetric efficiency close to one hundred percent.[7]
Categorization
Energy conversion
Turbomachines can be categorized on the basis of the direction of energy conversion:[1][2]
- Absorb power to increase the fluid pressure or head (ducted fans, compressors and pumps).
- Produce power by expanding fluid to a lower pressure or head (hydraulic, steam and gas turbines).
Fluid flow
Turbomachines can be categorized on the basis of the nature of the flow path through the passage of the rotor:[8]
A Kaplan turbine is an example of an axial flow turbine.
In the figure:
- U = Blade velocity,
- Vf = Flow velocity,
- V = Absolute velocity,
- Vr = Relative velocity,
- Vw = Tangential or Whirl component of velocity.
Radial flow turbomachines - When the path of the throughflow is wholly or mainly in a plane perpendicular to the rotation axis, the device is termed a radial flow turbomachine.[9] Therefore, the change of radius between the entry and the exit is finite. A radial turbomachine can be inward or outward flow type depending on the purpose that needs to be served. The outward flow type increases the energy level of the fluid and vice versa. Due to continuous change in direction, several radial stages are generally not used.
A centrifugal pump is an example of a radial flow turbomachine.
Mixed flow turbomachines – When axial and radial flow are both present and neither is negligible, the device is termed a mixed flow turbomachine.[9] It combines flow and force components of both radial and axial types.
A Francis turbine is an example of a mixed-flow turbine.
Physical action
Turbomachines can finally be classified on the relative magnitude of the pressure changes that take place across a stage:[2][5]
Impulse Turbomachines operate by accelerating and changing the flow direction of fluid through a stationary nozzle (the stator blade) onto the rotor blade. The nozzle serves to change the incoming pressure into velocity, the enthalpy of the fluid decreases as the velocity increases. Pressure and enthalpy drop over the rotor blades is minimal. Velocity will decrease over the rotor.[1][9]
A Pelton wheel is an impulse design.
Reaction Turbomachines operate by reacting to the flow of fluid through aerofoil shaped rotor and stator blades. The velocity of the fluid through the sets of blades increases slightly (as with a nozzle) as it passes from rotor to stator and vice versa. The velocity of the fluid then decreases again once it has passed between the gap. Pressure and enthalpy consistently decrease through the sets of blades.[1]
Most turbomachines use a combination of impulse and reaction in their design, often with impulse and reaction parts on the same blade.
Dimensionless ratios to describe turbomachinery
The following dimensionless ratios are often used for the characterisation of fluid machines. They allow a comparison of flow machines with different dimensions and boundary conditions.
- Pressure range ψ
- Flow coefficient φ (including delivery or volume number called)
- Performance numbers λ
- Run number σ
- Diameter number δ
Applications
Power Generation
Hydro electric - Hydro-electric turbomachinery uses potential energy stored in water to flow over an open impeller to turn a generator which creates electricity
Steam turbines - Steam turbines used in power generation come in many different variations. The overall principle is high pressure steam is forced over blades attached to a shaft, which turns a generator. As the steam travels through the turbine, it passes through smaller blades causing the shaft to spin faster, creating more electricity.
Gas turbines - Gas turbines work much like steam turbines. Air is forced in through a series of blades that turn a shaft. Then fuel is mixed with the air and causes a combustion reaction, increasing the power. This then causes the shaft to spin faster, creating more electricity.
Windmills - Also known as a
Marine
Steam turbine - Steam turbines in marine applications are very similar to those in power generation. The few differences between them are size and power output. Steam turbines on ships are much smaller because they don't need to power a whole town. They aren't very common because of their high initial cost, high specific fuel consumption, and expensive machinery that goes with it.
Gas turbines - Gas turbines in marine applications are becoming more popular due to their smaller size, increased efficiency, and ability to burn cleaner fuels. They run just like gas turbines for power generation, but are also much smaller and do require more machinery for propulsion. They are most popular in naval ships as they can be at a dead stop to full power in minutes (Kayadelen, 2013), and are much smaller for a given amount of power.
Water jet - Essentially a water jet drive is like an aircraft turbojet with the difference that the operating fluid is water instead of air.[10] Water jets are best suited to fast vessels and are thus used often by the military. Water jet propulsion has many advantages over other forms of marine propulsion, such as stern drives, outboard motors, shafted propellers and surface drives.[11]
Auto
Turbochargers - Turbochargers are one of the most popular turbomachines. They are used mainly for adding power to engines by adding more air. It combines both forms of turbomachines. Exhaust gases from the engine spin a bladed wheel, much like a turbine. That wheel then spins another bladed wheel, sucking and compressing outside air into the engine.
Superchargers - Superchargers are used for engine-power enhancement as well, but only work off the principle of compression. They use the mechanical power from the engine to spin a screw or vane, some way to suck in and compress the air into the engine.
General
Pumps - Pumps are another very popular turbomachine. Although there are very many different types of pumps, they all do the same thing. Pumps are used to move fluids around using some sort of mechanical power, from electric motors to full size diesel engines. Pumps have thousands of uses, and are the true basis to turbomachinery (Škorpík, 2017).
Air compressors - Air compressors are another very popular turbomachine. They work on the principle of compression by sucking in and compressing air into a holding tank. Air compressors are one of the most basic turbomachines.
Fans -
Aerospace
Gas turbines - Aerospace gas turbines, more commonly known as jet engines, are the most common gas turbines.
Turbopumps - Rocket engines require very high propellant pressures and mass flow rates, meaning their pumps require a lot of power. One of the most common solutions to this issue is to use a turbopump that extracts energy from an energetic fluid flow. The source of this energetic fluid flow could be one or a combination of many things, including the decomposition of hydrogen peroxide, the combustion of a portion of the propellants, or even the heating of cryogenic propellants run through coolant jackets in the combustion chamber's walls.
Partial list of turbomachine topics
Many types of dynamic continuous flow turbomachinery exist. Below is a partial list of these types. What is notable about these turbomachines is that the same fundamentals apply to all. Certainly there are significant differences between these machines and between the types of analysis that are typically applied to specific cases. This does not negate the fact that they are unified by the same underlying physics of fluid dynamics, gas dynamics, aerodynamics, hydrodynamics, and thermodynamics.
- Axial compressor
- Axial fan
- Centrifugal compressor
- Centrifugal fan
- Centrifugal pump
- Centrifugal type supercharger
- Exoskeletal engine
- Francis turbine
- Gas turbine
- Industrial fans
- Jet engine
- Mechanical fan
- Mixed flow compressor
- Radial turbine
- Steam turbine
- Turbocharger
- Turboexpander
- Turbofans
- Turbojet
- Turboprop
- Turbopump
- Turboshaft
- Turbines
- Water turbine
See also
- Blade solidity
- Secondary flow in turbomachinery
- Slip factor
- Three-dimensional losses and correlation in turbomachinery
References
- ^ a b c d e f g h i Logan, Earl. "Handbook of turbomachinery". 1995. Marcel Deckker.
- ^ a b c d e f Vandad Talimi (Original author unknown). "Mechanical Equipment and Systems". 2013. Memorial University of Newfoundland. http://www.engr.mun.ca/~yuri/Courses/MechanicalSystems/Turbomachinery.pdf
- ISBN 978-0-07-247236-3.
- ^ "How electricity is generated - U.S. Energy Information Administration (EIA)". www.eia.gov. Retrieved 2023-08-06.
- ^ a b Baskharone, E. A. "Principles of Turbomachinery in Air-Breathing Engines". 2006. Cambridge University Press. 580 pages.
- ISBN 81-224-1493-1
- ISBN 978-3-319-07995-0
- ISBN 0-8247-6976-7
- ^ ISBN 0-7506-7870-4
- ^ "Waterjet drives propulsion systems". www.castoldijet.it. Retrieved 2017-10-12.
- ^ "WaterJet Overview". HamiltonJet. 2015-03-18. Retrieved 2017-10-12.
Sources
- S. M. Yahya. "Turbines Compressors and Fans". 1987. McGraw Hill.
- Meher-Homji, Cyrus B. (2000). The Historical Evolution Of Turbomachinery. Turbomachinery Laboratory Turbomachinery and Pump Symposia. pp. 281–322. hdl:1969.1/163364.
- Nagpurwala, Q. (n.d.). Steam Turbines. Retrieved April 10, 2017, from http://164.100.133.129:81/eCONTENT/Uploads/13-Steam%20Turbines%20%5BCompatibility%20Mode%5D.pdf[dead link][unreliable source?]
- Soares, C. M. (n.d.). GAS TURBINES IN SIMPLE CYCLE & COMBINED CYCLE APPLICATIONS. 1-72. Retrieved April 10, 2017, from https://www.netl.doe.gov/File%20Library/Research/Coal/energy%20systems/turbines/handbook/1-1.pdf
- Perlman, U. H. (2016, December 2). Hydroelectric power: How it works. Retrieved April 10, 2017, from https://water.usgs.gov/edu/hyhowworks.html
- Škorpík, J. (2017, January 1). Lopatkový stroj-English version. Retrieved April 9, 2017, from http://www.transformacni-technologie.cz/en_11.html
- Kayadelen, H. (2013). Marine Gas Turbines. 7th International Advanced Technologies Symposium. Retrieved April 15, 2017.