The BEST TURBOPROP explanation video! By Captain Joe and PRATT & WHITNEY
Summary
TLDRIn this engaging video, Captain Joe delves into the intricacies of the Pratt and Whitney PT6 turboprop engine, renowned for its reliability and power. He explains its unique reverse-flow design, the 'suck, squeeze, bang, blow' principle, and how it differs from standard jet engines. From the cold section's compressor stages to the hot section's combustion and turbine mechanisms, the video offers a detailed look at the PT6's operation. Highlighting its free turbine feature, which aids in handling high torque, Joe also touches on maintenance benefits and the PT6E series' advanced electronic controls, showcasing the engine's enduring legacy in aviation.
Takeaways
- 😀 The Pratt and Whitney PT6 turboprop engine is renowned for its reliability, power, advancement, and widespread sales in its class.
- 🔧 The PT6 operates on a reverse flow free turbine design, which is unique compared to standard jet engines.
- 🌀 It follows the 'suck, squeeze, bang, blow' principle, but unlike jet engines, it lacks a bypass, relying solely on exhaust gases to turn the propeller.
- 🌪️ The engine intakes air from the back, with a low-pressure axial compressor followed by a centrifugal compressor that significantly increases air pressure and temperature.
- 🔥 In the combustion chamber, 14 fuel nozzles inject jet fuel, which ignites and expands, driving the compressor turbine and the gas generator.
- 🔄 The PT6 features a free turbine design where the power turbine spins independently and in the opposite direction of the compressor turbine, which helps manage torque.
- ⚙️ The power turbine transfers energy to the propeller through a reduction gearbox, allowing for large propellers at slower, more efficient speeds.
- 🛫 The PT6's compact design, short power shaft, and counter-rotating elements contribute to a lighter structure with fewer vibration issues, making it ideal for rough runways.
- 🔧 Maintenance is facilitated by the independent shafts, allowing for easy access to the gas generator section when the power section is removed.
- 🌟 The latest PT6E-66XT model introduces a dual-channel integrated electronic propeller and engine control system, enhancing precision, performance, and efficiency.
- 🚁 The PT6 engine is trusted to power a wide range of aircraft, including planes, helicopters, and other vehicles, as evidenced by the extensive list provided in the video.
Q & A
What is the main topic of the video?
-The main topic of the video is an explanation of how the Pratt and Whitney PT6 turboprop engine works, its unique features, and its relevance in the aviation industry.
What makes the PT6 engine unique among other gas turbine engines?
-The PT6 engine is unique as it is a reverse flow free turbine turboprop engine, which means it operates from back to front, unlike standard jet engines, and it does not have a bypass compared to airliner engines.
How does the PT6 engine's cold section function?
-The cold section of the PT6 engine functions by sucking in outside air through the inlet duct, directing it towards the compressor, and then through a series of low-pressure axial compressor stages and stator blades to increase air pressure and temperature.
What is the role of the centrifugal compressor in the PT6 engine?
-The centrifugal compressor in the PT6 engine further increases the air pressure and temperature after the air has passed through the axial compressor stages, acting similarly to a turbocharger's spin wheel in a car.
How does the combustion process in the PT6 engine differ from a typical car engine?
-In the PT6 engine, the combustion process is continuous from engine start until shutdown, and it does not use spark plugs. Instead, it relies on hot compressed air to self-ignite the fuel-air mixture, with spark igniters assisting during cold engine starts.
What is the purpose of the power turbine in the PT6 engine?
-The power turbine in the PT6 engine converts the kinetic energy from the exhaust gases into mechanical power, which then turns the power shaft at a high speed, ultimately driving the propeller through a reduction gearbox.
Why is the PT6 engine considered easy to start, especially in cold weather?
-The PT6 engine is easy to start because it has a free turbine design, meaning the power turbine shaft spins freely and is not connected to the gas turbine shaft. This allows the starter to only accelerate the gas generator during startup.
What is the significance of the accessory gearbox in the PT6 engine?
-The accessory gearbox in the PT6 engine is significant as it reduces the high RPM from the gas generator shaft to a lower speed suitable for running mounted accessories such as the fuel control unit and other systems.
How does the PT6 engine's free turbine design benefit maintenance?
-The free turbine design allows for the entire power section, including the propeller, to be removed for easier access to the gas generator section, simplifying maintenance procedures.
What is the PT6E series engine's new feature in general aviation?
-The PT6E series engine introduces a dual-channel integrated electronic propeller and engine control system, a first in general aviation, enhancing precision, performance, and efficiency.
Why is the PT6 engine suitable for rough runway surfaces?
-The PT6 engine is suitable for rough runway surfaces because its reverse flow design allows foreign objects to be diverted by inertial separators in the inlet, making it ideal for bush planes that often land on uneven terrain.
Outlines
🚁 Introduction to the PT6 Turboprop Engine
The video script introduces viewers to the Pratt and Whitney PT6 turboprop engine at the EAA Air Venture in Oshkosh. It promises an explanation of the engine's workings, its uniqueness, and a connection to Dom Toretto's Dodge Charger from The Fast and the Furious. The PT6 is highlighted as a reliable, powerful, and advanced engine, with a focus on its reverse flow free turbine design, which differs from standard jet engines by propelling air from back to front. The script sets the stage for a detailed exploration of the engine's components and functions.
🔧 Inside the PT6 Engine: Components and Functions
This paragraph delves into the technical aspects of the PT6 engine, detailing its components and their functions. The engine operates on the principle of 'suck, squeeze, bang, blow' but without a bypass, unlike standard jet engines. The unique reverse flow design is emphasized, with air intake from the rear and propulsion via exhaust gases. The cold section includes the low-pressure axial compressor and a centrifugal compressor, which significantly increase air pressure and temperature. The hot section involves combustion with 14 fuel nozzles and a continuous process from startup to shutdown, facilitated by spark igniters during cold starts. The gas generator, consisting of the compressor, combustion chamber, and turbine, is described, along with the power turbine and its role in converting air speed into mechanical power through a reduction gearbox, suitable for large propellers.
🛫 The Advantages of the PT6's Free Turbine Reverse Flow Design
The final paragraph of the script discusses the advantages of the PT6 engine's free turbine reverse flow design. It explains how the counter-rotation of the power turbine helps manage torque forces, especially during high power changes, preventing potential issues like flipping over an aircraft. The design contributes to a shorter and lighter engine, ideal for rough runway surfaces and easy maintenance. The script also mentions the accessory gearbox, fuel control unit, and the electronic propeller and engine control system introduced in the latest PT6E series. The video concludes by listing various aircraft that utilize the PT6 engine, emphasizing its widespread trust and reliability in the aviation industry.
Mindmap
Keywords
💡EAA Air Venture
💡Pratt and Whitney
💡PT6 Engine
💡Reverse Flow
💡Free Turbine
💡Gas Turbine Engine
💡Axial Compressor
💡Centrifugal Compressor
💡Combustion Chamber
💡Torque
💡Reduction Gearbox
💡Propeller
💡Gas Generator
💡Jet Fuel
💡Shaft Horsepower
Highlights
Introduction to the Pratt and Whitney PT6 turbo engine as one of the most reliable, powerful, advanced, and widely sold engines in its class.
Explanation of the unique reverse flow free turbine turbo prop engine design of the PT6.
The PT6 engine's operation principle following 'suck, squeeze, bang, blow' without a bypass, unlike standard jet engines.
Description of the PT6's cold section, including the air intake and low-pressure axial compressor stages.
Details on the centrifugal compressor and its function in heating and pressurizing air to 300 degrees Celsius and 10 bar.
The combustion process in the PT6 engine involving 14 fuel nozzles and controlled, vectored combustion.
How the high-pressure compressor turbine drives the compressor stages at 39,000 RPM.
The energy transfer from hot gas to the compressor turbine and then to the power turbine in the PT6 engine.
The function of the power turbine and its role in converting air speed into mechanical power for the propeller.
The significance of the reduction gearbox in adjusting the power shaft's speed to drive the propeller effectively.
The free turbine design allowing the power turbine to spin independently from the gas generator for better torque management.
Advantages of the PT6's reverse flow design, including a shorter engine length and reduced vibrations.
How the PT6 engine's design makes it suitable for rough runway surfaces and easy maintenance.
Introduction of the PT6E series and its dual-channel integrated electronic propeller and engine control system.
The PT6 engine's broad application in various aircraft, helicopters, and vehicles, emphasizing its reliability.
A summary of the PT6 turboprop engine's components, features, and its status as an iconic engine in the aviation industry.
Closing remarks with a thank you to Pratt & Whitney and a call to action for viewers to engage with the channel.
Transcripts
dear friends and followers welcome back
to my channel and lovely greetings from
the EAA Air Venture here in Oshkosh at
the Pratt and Whitney booth in today's
video we'll be talking about one of the
most reliable most powerful most
advanced and most sold engine in its
class the Pratt and Whitney pt6 turbo
engine I'll explain how the engine works
why it's so unique and what Dom
toretto's Dodge Charger from The Fast
and Furious movie has to do with it
clear probe and let's get started
today's video is brought to you by Pratt
Whitney powering sustainable Aviation
with Dependable engines let's first get
a fundamental understanding of the pt6
engine now the pt6 works like most other
gas turbine engine but is in one aspect
uniquely different as it is a reverse
flow free turbine turbo prop engine what
that means you'll see in a minute as
I'll mention each section individually
now it follows the same principle of
suck squeeze bang blow but the pt6 does
not have a bypass compared to the
standard jet engine on an airliner which
makes up more than 80 percent of the
forward pushing thrust now within the
pt6 it's only the exhaust gases that
make the propeller turn and instead of
pushing the air through the engine from
front to back the pt6 does it from back
to front so we're not starting thing
here instead we have to start at the
back of the engine right here so
initially the outside air gets sucked in
via the inlet duct which on many pt6
driven planes you see below the
propeller now the air is directed below
the engine towards the inlet screen
where the steel mesh protects the engine
from large debris entering so in this
part known as the cold section the
outside air gets sucked in and then
directed towards the compressor now the
first part is the low pressure axle
compressor which comprises three stages
for the small pt6 engines or four stages
for the larger pt6 engines but why low
pressure now very basically speaking the
inlet sucks in the outside air more or
less like a powerful vacuum cleaner the
first stage has the largest compressor
blades which accelerate the air or put
kinetic energy into it and right after
the rotary blades are a set of stator
veins meaning they are stationary or
fixed in place and Aid in increasing the
air pressure this accelerating and
increasing of air pressure process
repeats itself two or three more times
as the air gets forced further inwards
now at the same time the diameter
Narrows with each axial compressor stage
each followed by a set of stator blades
now to give you a perspective the air
entered at let's say 15 degrees Celsius
at the inlet with one bar outside
pressure and once it passed through the
first four compressor stages the air got
heated to 180 degrees Celsius and
increased to 4 Bar in air pressure
think of your bicycle pump remember how
warm it gets as you pump air into your
tires after the last set of stator veins
the heated compressed and accelerated
air enters the single stage centrifugal
compressor now compare this to the spin
wheel of the turbocharger in your car if
you don't have a Turbocharger in your
car this is what it looks like now at
this point the air has a temperature of
approximately 300 degrees Celsius and a
pressure of roughly 10 bar that means it
went in with one bar at the inlet and
forcing it through a compressor which is
not longer than 30 centimeters the
pressure is 10 times higher now the
already relatively hot and compressed
air then gets guided around this Bend
via a pipe diffuser which makes sense
because initially the flow Direction was
parallel along the compressor shaft then
the centrifugal compressor changed its
direction by 90 degrees to the shaft and
after the diffuser it is yet again
parallel as it enters the combustion
chamber liner so this completes the end
of the Cold section OD compressor stage
we've sucked in the air squeezed it
together and now the air enters the hot
section as the air exits the diffuser
and enters the combustion chamber liner
it passes by the 14 fuel nozzles which
inject jet fuel into the combustion
chamber now the fuel air mixture then
ignites instantly which leads to a
controlled and vectored combustion
meaning the hot expanding gases are
confined in the combustion chamber and
want to vacate the chamber as quickly as
possible it is then guide around this
Bend so briefly into the opposite
direction it came from and then flows
directly onto the high pressure
compressor turbine so this is a single
stage axial flow turbine and as you can
clearly see here the turbine is the
driving force of the compressor stages
as they are both mounted on the same
shaft spinning at approximately 39 000
revolutions per minute or 650 rounds per
second so the three components I just
mentioned the compressor the combustion
chamber and the compressor turbine
complete the gas generator does that
make sense now two more things I need to
mention in regards to the combustion
chamber the combustion of the fuel air
mixture is continuous from the engine
start until shutdown meaning because of
the hot compressed air entering the
combustion chamber it will also
self-ignite the mixture as long as fuel
flow is given also there are no spark
plugs as you would have in your car to
ignite the fuel air mixture but during
engine start you can hear that Infamous
clicking sound those are a set of spark
igniters on both sides of the combustion
chamber assisting the engine's startup
when the core is still relatively cold
on to the next stage so we can estimate
that a little more than half of the
energy from the hot gas exiting the
combustion chamber was absorbed or used
to spin the compressor turbine now the
remaining Gas Energy is then guided into
the power turbine the gas passes yet
again a set of stator veins which
accelerate the gas velocity and then
hits the first axial power turbine very
simply speaking think of a hair dryer
being the gas generator blowing onto a
windmill which is our power turbine that
converts air speed into kinetic or
mechanical Power the extracted energy
from the gas stream then turns the power
shaft and Spins it up to 33 000
revolutions per minute the exhaust gases
then Escape through these two side
mounted ducts in the power turbine
housing which are somewhat of the
signature of the pt6 engine letting
other Pilots know what this plane is
powered by so now we have 33 000
revolutions per minute which is way too
fast to drive a propeller now instead
the power shaft is then connected to a
two-stage planetary output reduction
gearbox which turns the propeller at a
speed of 1700 to 2200 revolutions per
minute outputting a reduction ratio of
approximately 15 to 1 which allows for
the largest propellers within the
general aviation industry to be mounted
for example the Pilates Porter comes
with a 2.7 meters in diameter propeller
and at 1700 pounds of torque so the
power turbine blades the power turbine
shaft and the reduction gearbox make up
the power section of the pt6 an
important note I mentioned at the
beginning that it's a free turbine what
is meant by that now if you haven't
noticed it yet the power turbine turns
in the opposite direction of the
compressor turbine why is that if you
look closely in between the first axial
power turbine and the compressor turbine
you'll notice they are not connected
with each other meaning the power
turbine shaft spins freely and is not
connected with the gas turbine shaft yet
again think of a hairdryer blowing onto
a windmill now the counter rotation also
serves its purpose remember when Dom
Toretto revved the engine of his tuned
up Dodge Charger now the immense torque
nearly bent the frame of his car so
during excessive power changes for
instance during takeoff and go around
the excess torque could if the power
turbine the gas generator and the
propeller would all spin in the same
direction potentially flip over your
plane and all pilots flying the pt6
engine in a single-engine aircraft know
how strong the torque forces still are
despite the counter rotation
but there are some great advantages that
come with the free turbine reverse flow
turbo prop engine design the overall
length of only 1.8 meters of the power
unit is relatively short compared to
others and keep in mind the pt6 and
various models can output from 550 up to
1700 shaft horsepower the reverse flow
also allows for a shorter power shaft
resulting in a lighter structure and
fewer vibration problems and due to the
fact that a compressor intake is at the
back of the engine foreign objects can
be diverted by inertial separators in
the inlet making the engine ideal for
rough Runway surfaces hence the Cessna
Caravan or the Pilates Porter which are
well known as Bush planes because they
hardly ever land on a Tarmac Runway also
the three turbine allows for both shafts
to run at different speeds and during
engine startup the starter has to
accelerate only the gas generator making
the engine easy to start particularly in
cold weather also because both shafts
are independent it aids in maintenance
by allowing the entire power section to
be removed along with the propeller
exposing the gas generator section for
easier access okay now that we've spoken
about the main engine components I would
like to direct your attention to the
rear and front part of the engine at the
rear part we have the accessory gearbox
directly connected to the gas generator
shaft reducing 39 000 RPM to as low as
4000 RPM to run the mounted accessories
for instance the fuel control unit which
controls the amount of fuel needed in
accordance with the thrust and propeller
lever position right in front of that is
the high pressure fuel pump bringing up
the necessary pressure for the fuel
nozzles on the other side we have two
scavenge oil pumps responsible for
proper lubrication of the reduction
gearbox both shafts and the accessory
gearbox and the large thing here is the
starter and Generator which is connected
to the airplane's battery and then spins
up the gas generator for engine start
and then acts as an electric power
generator once the engine is running
then at the front we have the propeller
interface unit which respectively
controls the propellers RPM now here we
have a glimpse of the Pratt and
Whitney's latest
p26e66x T engine model it's part of the
pt6e series engine family the first to
offer a dual Channel integrated
electronic propeller and engine control
system in general aviation in summary it
has all the trusted components that have
made the pt6 the iconic engine it is
today plus many new features for the
optimal combination of precision
performance and efficiency and lastly
this is a list of planes helicopters and
other vehicles that trust the power and
reliability of this engine and as you
can see this is long and growing and
this sums up my explanation of how the
pt6 turbo pulp engine works I really
hope you enjoyed this video and got a
few takeaways from this incredible
engine a huge thank you to Pratt Whitney
and their team here at the standard
Oshkosh for allowing us to record this
video and on that bombshell here's your
checklist for today subscribe to my
channel and check activate the
notification Bell check follow my
Instagram account check and perform a
touch and go at my website check and
don't forget a good pilot is always
learning especially at the air Venture
here in oscos wishing you all the best
your Captain Joe
[Music]
thank you
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