Rolls-Royce brings propeller engines back in vogue

http://www.guardian.co.uk/environmen...ort-rollsroyce

Rolls-Royce brings propeller engines back in vogue
Aviation company claims the design could cut an airline's fuel bills
and greenhouse gas emissions by 30%

* Alok Jha, green technology correspondent
* guardian.co.uk,
* Monday October 20 2008 10.36 BST
* Article history

Charles Lindbergh poses with his plane The Spirit of St Louis in 1927.
Photograph: AP

It evokes images of the vintage days of aviation, when flying around
the world was a luxury few could afford. But propeller-driven
aircraft, inspired by the iconic Spirit of St Louis, could make a
return thanks to innovative fuel-saving designs.

The Guardian has learned that Rolls-Royce recently cleared a major
hurdle in testing its new design for a propeller-driven engine,
involving a double rotor and new blade shape. Engineers have called
Rolls-Royce's design a "tremendously significant" step forward.

The company claims the design could cut an airline's fuel bills and
greenhouse gas emissions by 30%. "We're talking about saving $3m or
10,000 tonnes of CO2 per year per aircraft if you introduce an open-
rotor on to a 100-200-seater aircraft," said Mark Taylor, an engineer
at Rolls-Royce who is leading a project to design the next generation
of aircraft engines.

Modern propeller-driven engines, also known as advanced open rotors or
turboprops, are acknowledged to be more fuel efficient than the
turbofan and turbojet engines used by most aircraft today. But,
despite much research and testing by all the major engine manufaturers
in the early 1980s, they never caught on, partly because they are far
noisier. But with the growth in aviation causing major environmental
concerns, aeronautical engineers believe that the open-rotor engine
could have a new lease of life.

"We believe that, based on our test, we can produce a quiet and
efficient open-rotor engine," said Taylor. The company believes its
design would be quieter than any aircraft in operation today.

Rod Self, an acoustic engineer who works on aircraft engines at
Southampton University said Rolls-Royce's latest work was
"tremendously significant — they are a significant player in this
market. On the noise front, they've got the best models going and … a
lead on others in the field."

Efficiency improvements are sorely needed, said Alice Bows, a climate
scientist at the University of Manchester's Tyndall Centre who
specialises in aviation's environmental impact, said: "The amount of
CO2 from aviation looks to be 2-3%, a relatively small proportion of
the world's total. But you've got annual growth of 6-7% in terms of
passenger kilometres with efficiency improvement only at around 1%."

Turbofan engines work by sucking in air with a enclosed fan at the
front of the engine. Most of this air is pushed out of the back to
produce the thrust needed, with the rest used to burn fuel to drive
the fan. The more air that is pushed out rather than burned, known as
the bypass ratio, the more efficient the engine is. Put simply, open-
rotor engines have a higher bypass ratio than turbofans or turbojets
for an equivalent-sized device.

Another reason for the higher efficiency of open-rotor engines is
that, unlike traditional engines, they do not have a casing around the
propeller. The casing increases weight and drag. "Because you've
removed the [casing], you're able to go to much bigger fan diameters
and not incur the weight and drag penalties," said Taylor.

The airline industry has been here before. The oil crisis in the late
1970s encouraged engineers to design engines inspired by the old
propeller-aircraft of the first half of the 20th century but
incorporating the jet technology used in the more modern aircraft
engines.

American engine manufacturers Pratt & Whitney and General Electric,
both funded by Nasa, flew open-rotor designs for several hundred hours
on McDonnell Douglas and Boeing aircraft. But two factors prevented
open rotors from being used commercially — noise and propeller
designs. In addition, the drop in the price of oil meant there was no
great incentive to save fuel.

But the rise in the price of oil over the past year coupled with
environmental concerns mean that efficient engine designs once again
look attractive.

Rolls-Royce's design uses two sets of propellers near the rear of the
engine, which rotate in opposite directions. This reduces the energy
wasted when propellers twist some of the air, rather than pushing it
all straight backwards. "If you have a second set spinning in the
opposite direction, you untwist it and recover the energy from that
air. That goes into useful force to drive the aircraft forward," said
Self. "But it's even more noisy."

The sources of noise in an open-rotor engine come from different
aspects of the propeller, such as their thickness and whether the tips
spin faster than the speed of sound. Rolls Royce's engineers
specifically tackled these problems by increasing the number of blades
on the rotors, changing their shape from the traditional elongated to
a more squat design and making the blades thinner. The result was,
claims Rolls-Royce, a set of rotors that can turn at a slower speed —
and hence make less noise — while maintaining a high efficiency.

The British-based company is not the only one investigating the open-
rotor concept. General Electric, Pratt & Whitney and French company
Snecma all have open-rotor prototypes under construction, though
commercial secrecy means their progress is unclear.

Taylor said there was a choice for airlines. "You could go for a low-
noise advanced turbofan or you could trade that for some noise and go
for a much more efficient engine and that is the question we're asking
the aviation industry. What would you rather have — a bit better noise
profile or better fuel burn and lower CO2?"

"Sue Veneer" wrote in message
...
http://www.guardian.co.uk/environmen...ort-rollsroyce

Rolls-Royce brings propeller engines back in vogue
Aviation company claims the design could cut an airline's fuel bills
and greenhouse gas emissions by 30%

* Alok Jha, green technology correspondent
* guardian.co.uk,
* Monday October 20 2008 10.36 BST
* Article history

Charles Lindbergh poses with his plane The Spirit of St Louis in 1927.
Photograph: AP

It evokes images of the vintage days of aviation, when flying around
the world was a luxury few could afford. But propeller-driven
aircraft, inspired by the iconic Spirit of St Louis, could make a
return thanks to innovative fuel-saving designs.

The Guardian has learned that Rolls-Royce recently cleared a major
hurdle in testing its new design for a propeller-driven engine,
involving a double rotor and new blade shape. Engineers have called
Rolls-Royce's design a "tremendously significant" step forward.

The company claims the design could cut an airline's fuel bills and
greenhouse gas emissions by 30%. "We're talking about saving $3m or
10,000 tonnes of CO2 per year per aircraft if you introduce an open-
rotor on to a 100-200-seater aircraft," said Mark Taylor, an engineer
at Rolls-Royce who is leading a project to design the next generation
of aircraft engines.

Modern propeller-driven engines, also known as advanced open rotors or
turboprops, are acknowledged to be more fuel efficient than the
turbofan and turbojet engines used by most aircraft today. But,
despite much research and testing by all the major engine manufaturers
in the early 1980s, they never caught on, partly because they are far
noisier. But with the growth in aviation causing major environmental
concerns, aeronautical engineers believe that the open-rotor engine
could have a new lease of life.

"We believe that, based on our test, we can produce a quiet and
efficient open-rotor engine," said Taylor. The company believes its
design would be quieter than any aircraft in operation today.

Rod Self, an acoustic engineer who works on aircraft engines at
Southampton University said Rolls-Royce's latest work was
"tremendously significant — they are a significant player in this
market. On the noise front, they've got the best models going and … a
lead on others in the field."

Efficiency improvements are sorely needed, said Alice Bows, a climate
scientist at the University of Manchester's Tyndall Centre who
specialises in aviation's environmental impact, said: "The amount of
CO2 from aviation looks to be 2-3%, a relatively small proportion of
the world's total. But you've got annual growth of 6-7% in terms of
passenger kilometres with efficiency improvement only at around 1%."

Turbofan engines work by sucking in air with a enclosed fan at the
front of the engine. Most of this air is pushed out of the back to
produce the thrust needed, with the rest used to burn fuel to drive
the fan. The more air that is pushed out rather than burned, known as
the bypass ratio, the more efficient the engine is. Put simply, open-
rotor engines have a higher bypass ratio than turbofans or turbojets
for an equivalent-sized device.

Another reason for the higher efficiency of open-rotor engines is
that, unlike traditional engines, they do not have a casing around the
propeller. The casing increases weight and drag. "Because you've
removed the [casing], you're able to go to much bigger fan diameters
and not incur the weight and drag penalties," said Taylor.

The airline industry has been here before. The oil crisis in the late
1970s encouraged engineers to design engines inspired by the old
propeller-aircraft of the first half of the 20th century but
incorporating the jet technology used in the more modern aircraft
engines.

American engine manufacturers Pratt & Whitney and General Electric,
both funded by Nasa, flew open-rotor designs for several hundred hours
on McDonnell Douglas and Boeing aircraft. But two factors prevented
open rotors from being used commercially — noise and propeller
designs. In addition, the drop in the price of oil meant there was no
great incentive to save fuel.

But the rise in the price of oil over the past year coupled with
environmental concerns mean that efficient engine designs once again
look attractive.

Rolls-Royce's design uses two sets of propellers near the rear of the
engine, which rotate in opposite directions. This reduces the energy
wasted when propellers twist some of the air, rather than pushing it
all straight backwards. "If you have a second set spinning in the
opposite direction, you untwist it and recover the energy from that
air. That goes into useful force to drive the aircraft forward," said
Self. "But it's even more noisy."

The sources of noise in an open-rotor engine come from different
aspects of the propeller, such as their thickness and whether the tips
spin faster than the speed of sound. Rolls Royce's engineers
specifically tackled these problems by increasing the number of blades
on the rotors, changing their shape from the traditional elongated to
a more squat design and making the blades thinner. The result was,
claims Rolls-Royce, a set of rotors that can turn at a slower speed —
and hence make less noise — while maintaining a high efficiency.

The British-based company is not the only one investigating the open-
rotor concept. General Electric, Pratt & Whitney and French company
Snecma all have open-rotor prototypes under construction, though
commercial secrecy means their progress is unclear.

Taylor said there was a choice for airlines. "You could go for a low-
noise advanced turbofan or you could trade that for some noise and go
for a much more efficient engine and that is the question we're asking
the aviation industry. What would you rather have — a bit better noise
profile or better fuel burn and lower CO2?"


************

A staggering article. The Guardian makes a fool of itself yet again.
Turboprops with or without counter-rotating propellers have been used
extensively, in many parts of the world, for many years. Yet The Guardian
report this as a new-found technology which will "save the planet". They
should stick to the arts.

On 20 Okt, 17:13, Sue Veneer wrote:
http://www.guardian.co.uk/environmen...landtransport-...

Rolls-Royce brings propeller engines back in vogue
Aviation company claims the design could cut an airline's fuel bills
and greenhouse gas emissions by 30%

* * * Alok Jha, green technology correspondent
* * * guardian.co.uk,
* * * Monday October 20 2008 10.36 BST
* * * Article history

Charles Lindbergh poses with his plane The Spirit of St Louis in 1927.
Photograph: AP

It evokes images of the vintage days of aviation, when flying around
the world was a luxury few could afford. But propeller-driven
aircraft, inspired by the iconic Spirit of St Louis, could make a
return thanks to innovative fuel-saving designs.

The Guardian has learned that Rolls-Royce recently cleared a major
hurdle in testing its new design for a propeller-driven engine,
involving a double rotor and new blade shape. Engineers have called
Rolls-Royce's design a "tremendously significant" step forward.

The company claims the design could cut an airline's fuel bills and
greenhouse gas emissions by 30%. "We're talking about saving $3m or
10,000 tonnes of CO2 per year per aircraft if you introduce an open-
rotor on to a 100-200-seater aircraft," said Mark Taylor, an engineer
at Rolls-Royce who is leading a project to design the next generation
of aircraft engines.

Modern propeller-driven engines, also known as advanced open rotors or
turboprops, are acknowledged to be more fuel efficient than the
turbofan and turbojet engines used by most aircraft today. But,
despite much research and testing by all the major engine manufaturers
in the early 1980s, they never caught on, partly because they are far
noisier.

What ABSOLUTE bull****. Plenty fo short range commuter flights use
turboprops. They'r enot so efficient for long haul because they can't
reach the high altitudes a jet can (the thrust from a turboprop gets
significantly less the higher it goes, a turbofan has the opposite
effect.

But with the growth in aviation causing major environmental
concerns, aeronautical engineers believe that the open-rotor engine
could have a new lease of life.

"We believe that, based on our test, we can produce a quiet and
efficient open-rotor engine," said Taylor. The company believes its
design would be quieter than any aircraft in operation today.

Rod Self, an acoustic engineer who works on aircraft engines at
Southampton University said Rolls-Royce's latest work was
"tremendously significant — they are a significant player in this
market. On the noise front, they've got the best models going and … a
lead on others in the field."

Efficiency improvements are sorely needed, said Alice Bows, a climate
scientist at the University of Manchester's Tyndall Centre who
specialises in aviation's environmental impact, said: "The amount of
CO2 from aviation looks to be 2-3%, a relatively small proportion of
the world's total. But you've got annual growth of 6-7% in terms of
passenger kilometres with efficiency improvement only at around 1%."

Turbofan engines work by sucking in air with a enclosed fan at the
front of the engine. Most of this air is pushed out of the back to
produce the thrust needed, with the rest used to burn fuel to drive
the fan. The more air that is pushed out rather than burned, known as
the bypass ratio, the more efficient the engine is. Put simply, open-
rotor engines have a higher bypass ratio than turbofans or turbojets
for an equivalent-sized device.

...not as altitude increases, though.



Another reason for the higher efficiency of open-rotor engines is
that, unlike traditional engines, they do not have a casing around the
propeller. The casing increases weight and drag. "Because you've
removed the [casing], you're able to go to much bigger fan diameters
and not incur the weight and drag penalties," said Taylor.

...but you can't go as fast, or as high.



The airline industry has been here before. The oil crisis in the late
1970s encouraged engineers to design engines inspired by the old
propeller-aircraft of the first half of the 20th century but
incorporating the jet technology used in the more modern aircraft
engines.

American engine manufacturers Pratt & Whitney and General Electric,
both funded by Nasa, flew open-rotor designs for several hundred hours
on McDonnell Douglas and Boeing aircraft. But two factors prevented
open rotors from being used commercially — noise and propeller
designs. In addition, the drop in the price of oil meant there was no
great incentive to save fuel.

But the rise in the price of oil over the past year coupled with
environmental concerns mean that efficient engine designs once again
look attractive.

Rolls-Royce's design uses two sets of propellers near the rear of the
engine, which rotate in opposite directions.

Gosh, how innovative. Of course, the Gannet, designed in the 1940s
also had contra-rotating turboprops. The fastes prop aircraft of all
time, the TU 95 too. And that was designed in the 50's.

This reduces the energy
wasted when propellers twist some of the air, rather than pushing it
all straight backwards. "If you have a second set spinning in the
opposite direction, you untwist it and recover the energy from that
air. That goes into useful force to drive the aircraft forward," said
Self. "But it's even more noisy."

The sources of noise in an open-rotor engine come from different
aspects of the propeller, such as their thickness and whether the tips
spin faster than the speed of sound. Rolls Royce's engineers
specifically tackled these problems by increasing the number of blades
on the rotors, changing their shape from the traditional elongated to
a more squat design and making the blades thinner. The result was,
claims Rolls-Royce, a set of rotors that can turn at a slower speed —
and hence make less noise — while maintaining a high efficiency.

The British-based company is not the only one investigating the open-
rotor concept. General Electric, Pratt & Whitney and French company
Snecma all have open-rotor prototypes under construction, though
commercial secrecy means their progress is unclear.

Taylor said there was a choice for airlines. "You could go for a low-
noise advanced turbofan or you could trade that for some noise and go
for a much more efficient engine and that is the question we're asking
the aviation industry. What would you rather have — a bit better noise
profile or better fuel burn and lower CO2?"

Fuel burn is a somewhat misleading criterion if the aircraft is
travelling slower..

"True Blue" wrote:

A staggering article. The Guardian makes a fool of itself yet again.
Turboprops with or without counter-rotating propellers have been used
extensively, in many parts of the world, for many years. Yet The
Guardian report this as a new-found technology which will "save the
planet". They should stick to the arts.

Except they aren't talking about traditional turboprops. They are
describing a propfan, or unducted fan engine, which has the potential for
significant fuel savings compared to a traditional turboprop.

http://en.wikipedia.org/wiki/Propfan

They might also be able to exceed the maximum speed of a traditional
turboprop of about 450 mph.

The technology has been around for about 20 years, but never perfected
enough to be applied to a production aircraft.

wrote:

Modern propeller-driven engines, also known as advanced open rotors or
turboprops, are acknowledged to be more fuel efficient than the
turbofan and turbojet engines used by most aircraft today. But,
despite much research and testing by all the major engine manufaturers
in the early 1980s, they never caught on, partly because they are far
noisier.

What ABSOLUTE bull****. Plenty fo short range commuter flights use
turboprops. They'r enot so efficient for long haul because they can't
reach the high altitudes a jet can (the thrust from a turboprop gets
significantly less the higher it goes, a turbofan has the opposite
effect.

They are talking about propfans. While they are related to turboprops,
design estimates show a significant savings for stage lengths of 1500
miles, in comparison to standard turboprop or turbofan engines.

Another reason for the higher efficiency of open-rotor engines is
that, unlike traditional engines, they do not have a casing around the
propeller. The casing increases weight and drag. "Because you've
removed the [casing], you're able to go to much bigger fan diameters
and not incur the weight and drag penalties," said Taylor.

..but you can't go as fast, or as high.

They have about a 10 percent speed penalty, compared to current turbofans
at top cruising speed. This is not significant for shorter haul flights,
where they are only at cruise for a small part of the overall trip. The
use of propfans might add 5 minutes to a 500 mile flight, for example.

On 21 Okt, 14:31, James Robinson wrote:
wrote:
Modern propeller-driven engines, also known as advanced open rotors or
turboprops, are acknowledged to be more fuel efficient than the
turbofan and turbojet engines used by most aircraft today. But,
despite much research and testing by all the major engine manufaturers
in the early 1980s, they never caught on, partly because they are far
noisier.

What ABSOLUTE bull****. Plenty fo short range commuter flights use
turboprops. They'r enot so efficient for long haul because they can't
reach the high altitudes a jet can (the thrust from a turboprop gets
significantly less the higher it goes, a turbofan has the opposite
effect.

They are talking about propfans.

No, they are not - "Modern propeller-driven engines, also known as
advanced open rotors or turboprops...never caught on, partly because
they are far noisier."

*While they are related to turboprops,
design estimates show a significant savings for stage lengths of 1500
miles, in comparison to standard turboprop or turbofan engines. *

The Guardian article makes it clear they (the Guardian) are talking
about contra-rotating turboprops. I suspect what RR have actually
built is an engine where the turbine stage, rather than the compressor
stage has been replaced with uncased, large diameter blades. ISTR
seeing a MD80 fitted with these in Flight International back in the
early 80's



Another reason for the higher efficiency of open-rotor engines is
that, unlike traditional engines, they do not have a casing around the
propeller. The casing increases weight and drag. "Because you've
removed the [casing], you're able to go to much bigger fan diameters
and not incur the weight and drag penalties," said Taylor.

..but you can't go as fast, or as high.

They have about a 10 percent speed penalty, compared to current turbofans
at top cruising speed. *This is not significant for shorter haul flights,
where they are only at cruise for a small part of the overall trip. The
use of propfans might add 5 minutes to a 500 mile flight, for example.

Well, no, because the Guardian were quite clearly talking about
turboprops. I'm fully prepared to believe that's not what RR were
telling them, though.

On 21 Oct, 15:13, wrote:
On 21 Okt, 14:31, James Robinson wrote:

wrote:
Modern propeller-driven engines, also known as advanced open rotors or
turboprops, are acknowledged to be more fuel efficient than the
turbofan and turbojet engines used by most aircraft today. But,
despite much research and testing by all the major engine manufaturers
in the early 1980s, they never caught on, partly because they are far
noisier.

What ABSOLUTE bull****. Plenty fo short range commuter flights use
turboprops. They'r enot so efficient for long haul because they can't
reach the high altitudes a jet can (the thrust from a turboprop gets
significantly less the higher it goes, a turbofan has the opposite
effect.

They are talking about propfans.

No, they are not *- "Modern propeller-driven engines, also known as
advanced open rotors or turboprops...never caught on, partly because
they are far noisier."

oh yes they are

http://www.aviationweek.com/aw/blogs...7-9ce3c748f976

wrote:

James Robinson wrote:

wrote:

Modern propeller-driven engines, also known as advanced open
rotors or turboprops, are acknowledged to be more fuel efficient
than the turbofan and turbojet engines used by most aircraft
today. But, despite much research and testing by all the major
engine manufaturers in the early 1980s, they never caught on,
partly because they are far noisier.

What ABSOLUTE bull****. Plenty fo short range commuter flights use
turboprops. They'r enot so efficient for long haul because they
can't reach the high altitudes a jet can (the thrust from a
turboprop gets significantly less the higher it goes, a turbofan
has the opposite effect.

They are talking about propfans.

No, they are not - "Modern propeller-driven engines, also known as
advanced open rotors or turboprops...never caught on, partly because
they are far noisier."

Yes, they are. The clues are the comments about advanced open rotors,
and the fact that they are noisier.

*While they are related to turboprops,
design estimates show a significant savings for stage lengths of 1500
miles, in comparison to standard turboprop or turbofan engines. *

The Guardian article makes it clear they (the Guardian) are talking
about contra-rotating turboprops. I suspect what RR have actually
built is an engine where the turbine stage, rather than the compressor
stage has been replaced with uncased, large diameter blades. ISTR
seeing a MD80 fitted with these in Flight International back in the
early 80's

Those are called propfans.

Another reason for the higher efficiency of open-rotor engines is
that, unlike traditional engines, they do not have a casing around
the propeller. The casing increases weight and drag. "Because
you've removed the [casing], you're able to go to much bigger fan
diameters and not incur the weight and drag penalties," said
Taylor.

..but you can't go as fast, or as high.

They have about a 10 percent speed penalty, compared to current
turbofans at top cruising speed. *This is not significant for shorter
haul flights, where they are only at cruise for a small part of the
overall trip. The use of propfans might add 5 minutes to a 500 mile
flight, for example.

Well, no, because the Guardian were quite clearly talking about
turboprops. I'm fully prepared to believe that's not what RR were
telling them, though.

They are talking about propfans, which can be considered a specific type
of turboprop.

Lol michaelnewpoort has a problem : not more than 4 short words to type, or
else copy/paste.

"Sue Veneer" a écrit dans le message de
...
On 21 Oct, 15:13, wrote:
On 21 Okt, 14:31, James Robinson wrote:

wrote:
Modern propeller-driven engines, also known as advanced open rotors
or
turboprops, are acknowledged to be more fuel efficient than the
turbofan and turbojet engines used by most aircraft today. But,
despite much research and testing by all the major engine
manufaturers
in the early 1980s, they never caught on, partly because they are far
noisier.

What ABSOLUTE bull****. Plenty fo short range commuter flights use
turboprops. They'r enot so efficient for long haul because they can't
reach the high altitudes a jet can (the thrust from a turboprop gets
significantly less the higher it goes, a turbofan has the opposite
effect.

They are talking about propfans.

No, they are not - "Modern propeller-driven engines, also known as
advanced open rotors or turboprops...never caught on, partly because
they are far noisier."

oh yes they are

http://www.aviationweek.com/aw/blogs...7-9ce3c748f976

On 21 Okt, 14:04, James Robinson wrote:
"True Blue" wrote:

A staggering article. The Guardian makes a fool of itself yet again.
Turboprops with or without counter-rotating propellers have been used
extensively, in many parts of the world, for many years. Yet The
Guardian report this as a new-found technology which will "save the
planet". They should stick to the arts.

Except they aren't talking about traditional turboprops. *They are
describing a propfan, or unducted fan engine,

"Unducted fan" is a bit of a misnomer. Traditionally the fan refers to
the big cold whirry thing at the front rather than than small hot
whirly thing at the back.