Types Of Turbines
Introduction:-
• “Turbine” is a general term for any device that extracts mechanical energy from a
fluid – generally converting it to rotating energy of a turbine wheel.
• For liquids, we usually call them “hydraulic turbines” or “hydroturbines”.
• For gases, we usually call them “wind turbines”, “gas turbines”, or “steam
turbines”, depending on the type of gas being used.
• Just as with pumps, there are two basic types of turbine:
o Positive displacement turbines – fluid is forced into a closed volume, and then the
fluid is pushed out.
o Dynamic turbines – no closed volume is involved; instead, rotating blades called
runner blades or buckets extract energy from the fluid.
• In general, positive-displacement turbines are used for flow measurement, rather
than for production of power, whereas dynamic turbines are used for both power
generation and flow measurement.
Positive-Displacement Turbines:-
• The nutating disc flowmeter, commonly used to measure the volume of water
supplied to a house, is an example of a positive-displacement turbine.
• a type of turbine that generates power by displacing a fixed volume of fluid, often
used for micro and pico hydro power generation from unconventional sources like
water supply pipelines.
• How it works:
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Unlike traditional turbines that rely on fluid momentum, a PDT uses a mechanism (like gears,
lobes, or vanes) to trap and displace a specific volume of fluid, converting pressure energy
into mechanical energy.
• Examples:-
• Lobe Turbines: These use lobes or gears to displace fluid, similar to lobe pumps.
• Sliding/Rotary Vane Turbines: These use vanes that slide or rotate within a
chamber to displace fluid.
• Bi-rotor Turbines: These use two rotors to displace fluid
Nutating disk
• Other geometries are also used for positive-displacement turbines; e.g., a flowmeter
that uses a double helical three-lobe impeller design, as discussed in Chapter 8:
• A lobe turbine, also known as a rotary lobe pump used as a turbine, is a
positive displacement device that converts pressure energy into rotational
energy, often used in renewable energy applications to generate electricity.
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• Enter the world of in-conduit micro hydroelectric power generation. Think of it as
tapping into the hidden energy within our water infrastructure. Instead of merely
reducing pressure using traditional PRVs, what if we could harness that energy?
That’s where rotary lobe pumps come into play, acting as the unsung heroes in this
renewable energy narrative.
Dynamic Turbines:-
• Dynamic turbines do not have closed volumes. Instead, spinning blades called
runners or buckets transfer kinetic energy and extract momentum from the fluid.
• Dynamic turbines are used for both flow measurement and power production. For
example, turbine flowmeters for air and water are discussed in Chapter 8.
• The design of large wind turbine drivetrain systems is trending towards light weight
and integration. To ensure the safe operation of the drivetrain system, investigating
the electromechanical–rigid–flexible interaction of wind turbine transmission
systems is necessary.
• This study proposed an electromechanical–rigid–flexible coupling dynamic model
that can be used for variable speed and load operating conditions. The model
considered the timevarying mesh stiffness, structural flexibility, magnetic saturation
characteristics, and electromagnetic radial force. The effects of the flexibility of the
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Turbine used for
measurement of air speed
Turbine used for measurement
of volume flow rate of water
flowing in a pipe
housing and high-speed shaft on the electromechanical interaction of the system
under steady and unsteady conditions are discussed.
• There is a strong coupling between the gear system and the generator system. The
resonance speed at the generator is affected by the gear excitation, and the vibration
signal of the gear system is affected by electromagnetic excitation.
There are two main types of dynamic turbines: impulse turbines and reaction turbines.
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• Impulse turbines: Fluid is sent through a nozzle that then impinges on the rotating
blades, called buckets. Compared to reaction turbines, impulse turbines require
higher head, and work with a lower volume flow rate.
• The most common example is the Pelton wheel turbine.
• impulse turbine is a type of turbine that uses the kinetic energy of a high-velocity
fluid to generate mechanical energy. It's often used in hydropower plants and other
applications where high-speed water or steam is available.
• advantages like high efficiency, simple assembly, low maintenance, and suitability
for high-head applications, making them a preferred choice for certain power
generation scenarios.
•
• An impulse turbine is a type of turbine that uses the kinetic energy of a high-
velocity fluid to generate mechanical energy. It's often used in hydropower plants
and other applications where high-speed water or steam is available.
•
• The impulse turbine is the simplest type of turbine. It consists of a row of nozzles
followed by a row of blades. The gas is expanded in the nozzle, converting the high
thermal energy into kinetic energy. This conversion can be represented by the
following relationship: [2.39] V = 2 Δh.
• Impulse Turbines
•
• The impulse turbine is the descendant of the stream wheel. Like the latter, it uses the
impulse or kinetic energy in a stream of water to drive the turbine and provide power.
However while the stream wheel relies on the natural flow of water in a river or stream,
an impulse turbine uses a powerful jet of water that is generated from a high head of
water.
•
• modern Pelton turbine has a set of spoon-shaped buckets mounted on the
circumference of a wheel as shown in Fig. 4.3. The buckets are carefully formed so
that the water from the jet entering the bucket changes direction and exits on the
opposite side, transferring its momentum to the wheel as it does so. The water
imparts most of its momentum to the wheel in the process and leaves the bucket
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• V3=2Δh0
• The high-velocity gas impinges on the blade where a large portion of the kinetic energy
of the moving gas stream is converted into turbine shaft work.
• Figure 9-9 shows a diagram of a single-stage impulse turbine. The static pressure
decreases in the nozzle with a corresponding increase in the absolute velocity. The
absolute velocity is then reduced in the rotor; however, the static pressure and the
relative velocity remain constant. To get the maximum energy transfer, the blades •
• In-between the moving rows of blades are guide vanes that redirect the gas from
one row of moving blades to another as shown in Figure 9-10. This type of turbine
is sometimes called a Curtis turbine.
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• Reaction turbines: Instead of using water jets, reaction turbines fill a volute with
swirling water that rotates the runner blades. Compared to impulse turbines,
reaction turbines
require a lower head, and work with a higher volume flow rate. They are used primarily for
electricity production (hydroelectric dams).
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measured from just upstream of the turbine to just downstream of the draft tube, while gross
head Hgross is measured from the upstream reservoir surface to the downstream tailrace
surface.
A draft tube is a combination
of an elbow and a diffuser.
• Turbine efficiency:
• The efficiency of a turbine is the reciprocal of the efficiency of a pump!
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Vertical Axis Wind Turbines
Vertical axis wind turbines (VAWTs) are a less common type of wind turbine that has its axis
perpendicular to the ground. The primary advantages of VAWTs are as follows:
Advantages:
1. Size: VAWTs are usually smaller than HAWTs, which means they can be installed in
smaller spaces.
2. Less Noise: VAWTs are typically quieter than HAWTs, making them a better option for
areas where noise is a concern.
3. Safer for Birds: VAWTs are less likely to harm birds and bats because their blades move at
a slower speed.
However, VAWTs also have some disadvantages:
Disadvantages:
1. Less Efficient: VAWTs are less efficient than HAWTs because they cannot generate as
much electricity from the same amount of wind.
2. Limited Availability: VAWTs are less common than HAWTs, which means there may be
fewer options available for installation and maintenance.
3. Maintenance Challenges: VAWTs have more complex components, making maintenance
more challenging.
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Other Types of Wind Turbines
In addition to HAWTs and VAWTs, there are other types of wind turbines available, such as
darrieus and savonius turbines. These turbines have unique advantages and disadvantages
that must be considered when deciding which type of turbine to use.
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