What is new in CFM LEAP-1A

skywalker92 · Sun Nov 12, 2017 6:44 pm

Hello guys,

Recently I got a chance to work with few brand new A320neo and A321neo aircraft and they were fitted with CFM LEAP-1A engines. I noticed some differences in the LEAP engine when compared to other A320 family engines(mainly CFM 56-5B and V2500). What I noticed is,

1. It has a flag to indicated the locking status of fan cowls connected to the number 1 latch.
2.Less number of fan blades when compared to the other engines(18 to be more specific

).
3. Its FADEC is physically divided in to two channels with a pressure sub system located externally to the EEC.
4.It has some heat sink like protrusions inside the engine just after the fan blades(someone please tell me the name and reason to have them).
5. Sides of the oil tank and IDG has changed from the CFM 56 position.
6. C ducts can't be opened when the Slats are fully deployed(they will collide :lol:

).

This is what I noticed and I want to know what are the major/minor changes has been made in the LEAP engine.

Regards,
Skywalker92

Balerit · Sun Nov 12, 2017 8:21 pm

#4 is probably an oil cooler.

skywalker92 · Mon Nov 13, 2017 12:42 am

Balerit wrote:
#4 is probably an oil cooler.

Thanks Balerit

Is it for ACOC use?

Balerit · Mon Nov 13, 2017 7:55 am

skywalker92 wrote:
Balerit wrote:
#4 is probably an oil cooler.

Thanks Balerit

Is it for ACOC use?

It is used to cool the hydraulic oil in the CSD (constant speed drive that drives the electrical generator). Here is a link to a nice explanation of how they work:

http://www.k-makris.gr/AircraftComponents/CSD/C.S.D.htm

lightsaber · Mon Nov 13, 2017 5:41 pm

Major changes:
#1 is the higher RPM high compressor.
#2 is the two stage high turbine (allowing for a higher pressure ratio high compressor)
#3 is scimitar blades
#4 A completely different fan concept brought on by materials and aerodynamic improvements.
#5 variable cycle cooling of the high turbine (less cooling during cruise)
#6 Higher temperature internal materials (no way to retrofit the CFM-56 to the same temperatures)
#7 Wide cord low turbine blades (far more extreme in the LEAP-1B to cut the number of low turbine stages). A 7 stage low turbine is INSANE! (-1A/-1C only)
#8: 50:1 overall pressure ratio (about the same in the PW1100G, just very different ways to get there)
#9: incredibly short combustor technology (squish the engine shorter and thus lighter)
#10: large fan diameter (78" versus 81.81" in the PW1100G) Hence why the LEAP is 11:1 bypass and PW1100G is 12.5:1
#11: Ability to grow to 35k of thrust (not yet certified, but neither is Pratt)
#12: electric (vs. pneumatic or fuel) driven actuators. A step drop in maintenance costs (and two motor sizes on the engine to simplify spares, IIRC. Instead of one actuator on the TCCV, another on the the nacelle anti-ice, another on the wing anti-ice. Little is done 'old school' except for backpressure regulators that I'm aware of.

For myself, the fan technology is amazing. It allows a far higher RPM low spool than I thought possible. Thus, a far more efficient low spool to compete with the GTF.
The next was the variable cycle technology (variable high turbine cooling). That is someone proposed by Whittle we're finally seeing in engines! Finally!

Yes, there were other changes, but the engine architecture is radically different from the CFM-56.

Yes, a different list.

WIederling · Mon Nov 13, 2017 6:53 pm

lightsaber wrote:
The next was the variable cycle technology (variable high turbine cooling). That is someone proposed by Whittle we're finally seeing in engines! Finally!

Lead me! ... Please :-)

As a jet egine noob I wouldn't first order associate variable cycle with variable cooling.

Balerit · Tue Nov 14, 2017 10:26 am

WIederling wrote:
lightsaber wrote:
The next was the variable cycle technology (variable high turbine cooling). That is someone proposed by Whittle we're finally seeing in engines! Finally!

Lead me! ... Please

As a jet egine noob I wouldn't first order associate variable cycle with variable cooling.

https://www.google.ch/patents/US6931859

WIederling · Tue Nov 14, 2017 10:50 am

Balerit wrote:
WIederling wrote:
lightsaber wrote:
The next was the variable cycle technology (variable high turbine cooling). That is someone proposed by Whittle we're finally seeing in engines! Finally!

Lead me! ... Please

As a jet engine noob I wouldn't first order associate variable cycle with variable cooling.

https://www.google.ch/patents/US6931859

Thanks.

Rather obvious solution, isn't it? ( that is really patentable as late as in 200X ?)
... and this is mostly about reducing losses in the thermodynamic cycle, right?

Balerit · Tue Nov 14, 2017 2:38 pm

It's basically to control the blade tip clearances. The idea is to get the blades to stretch and then shrink the casing, giving tighter tolerances. It's no use shrinking the casing while the blades get too much cooling, allowing them to shrink as well thus causing the turbine to be less efficient.

WIederling · Tue Nov 14, 2017 3:32 pm

Balerit wrote:
It's basically to control the blade tip clearances. The idea is to get the blades to stretch and then shrink the casing, giving tighter tolerances. It's no use shrinking the casing while the blades get too much cooling, allowing them to shrink as well thus causing the turbine to be less efficient.

So you control blade length via temperature? I've seen that used for some gas valves on afair Cassini.
You heat the casing and thereby open the internal valve seating.
( based on that I had a solution at hand that would work as a constant flow valve.)

I'd combine a clearance servo with real time clearance measurements.

lightsaber · Tue Nov 14, 2017 3:58 pm

WIederling wrote:
Balerit wrote:
WIederling wrote:

Lead me! ... Please

As a jet engine noob I wouldn't first order associate variable cycle with variable cooling.

https://www.google.ch/patents/US6931859

Thanks.

Rather obvious solution, isn't it? ( that is really patentable as late as in 200X ?)
... and this is mostly about reducing losses in the thermodynamic cycle, right?

Yes, it is mostly about reducing losses. The implementation is patentable, not the whole concept. Just as liner cooling has details patented, but not the overall concept. e..g, a new formula of thermal barrier coating may be patented, but not the concept. It was a big deal to get rid of the barrier coating for example.

The change in cooling of the blades does lengthen the blades, so the case cooling scheme must adapt. eh...

I found a so-so link noting the cooling to the turbine blades is 'modulated':
http://aviationweek.com/mro/add-another ... -programme

The trick is the implementation, as the cooling air gets very hot at the end of climb. Thus, the modulating mechanism must be able to work over a wide range of temperatures.

Lightsaber

WIederling · Tue Nov 14, 2017 4:50 pm

lightsaber wrote:
I found a so-so link noting the cooling to the turbine blades is 'modulated':
http://aviationweek.com/mro/add-another ... -programme

The trick is the implementation, as the cooling air gets very hot at the end of climb. Thus, the modulating mechanism must be able to work over a wide range of temperatures.

Lightsaber

Super, thanks for that link!

WIederling wrote:
Balerit wrote:

https://www.google.ch/patents/US6931859

Thanks.

This:
“We also separately modulate the cooling to the outside of the HPT case to control [blade-tip] clearance of the HPT; and we separately modulate cooling to the outside of the LPT (low-pressure turbine) case to control LPT [blade-tip] clearance,” says Richards. “All three [systems] are independent and all are controlled by the FADEC.”

Time constants for blades and casing must be vastly different. Rather "interesting" control job :-)

skywalker92 · Tue Nov 14, 2017 5:54 pm

Balerit wrote:
skywalker92 wrote:
Balerit wrote:
#4 is probably an oil cooler.

Thanks Balerit

Is it for ACOC use?

It is used to cool the hydraulic oil in the CSD (constant speed drive that drives the electrical generator). Here is a link to a nice explanation of how they work:

http://www.k-makris.gr/AircraftComponents/CSD/C.S.D.htm

Thanks for the awesome link Balerit, appreciate it. :thumbsup:

lightsaber wrote:
Major changes:
#1 is the higher RPM high compressor.
#2 is the two stage high turbine (allowing for a higher pressure ratio high compressor)
#3 is scimitar blades
#4 A completely different fan concept brought on by materials and aerodynamic improvements.
#5 variable cycle cooling of the high turbine (less cooling during cruise)
#6 Higher temperature internal materials (no way to retrofit the CFM-56 to the same temperatures)
#7 Wide cord low turbine blades (far more extreme in the LEAP-1B to cut the number of low turbine stages). A 7 stage low turbine is INSANE! (-1A/-1C only)
#8: 50:1 overall pressure ratio (about the same in the PW1100G, just very different ways to get there)
#9: incredibly short combustor technology (squish the engine shorter and thus lighter)
#10: large fan diameter (78" versus 81.81" in the PW1100G) Hence why the LEAP is 11:1 bypass and PW1100G is 12.5:1
#11: Ability to grow to 35k of thrust (not yet certified, but neither is Pratt)
#12: electric (vs. pneumatic or fuel) driven actuators. A step drop in maintenance costs (and two motor sizes on the engine to simplify spares, IIRC. Instead of one actuator on the TCCV, another on the the nacelle anti-ice, another on the wing anti-ice. Little is done 'old school' except for backpressure regulators that I'm aware of.

For myself, the fan technology is amazing. It allows a far higher RPM low spool than I thought possible. Thus, a far more efficient low spool to compete with the GTF.
The next was the variable cycle technology (variable high turbine cooling). That is someone proposed by Whittle we're finally seeing in engines! Finally!

Yes, there were other changes, but the engine architecture is radically different from the CFM-56.

Yes, a different list.

Thanks for the fully detailed explanation lightsaber.

#5 I was never knew about that, Very interesting concept by the way.
Hope #6 is due to the use of Ceramic Matrix Ccomposites (CMC) for the Turbine blades.
In #7, hope it should be in the other way, according to my memory LEAP 1A got 7 HPT stages and 2 LPT stages.(IIRC :spin:

)

lightsaber · Tue Nov 14, 2017 6:14 pm

skywalker92 wrote:
Balerit wrote:
skywalker92 wrote:
Thanks Balerit

Is it for ACOC use?

It is used to cool the hydraulic oil in the CSD (constant speed drive that drives the electrical generator). Here is a link to a nice explanation of how they work:

http://www.k-makris.gr/AircraftComponents/CSD/C.S.D.htm

Thanks for the awesome link Balerit, appreciate it.

lightsaber wrote:
Major changes:
#1 is the higher RPM high compressor.
#2 is the two stage high turbine (allowing for a higher pressure ratio high compressor)
#3 is scimitar blades
#4 A completely different fan concept brought on by materials and aerodynamic improvements.
#5 variable cycle cooling of the high turbine (less cooling during cruise)
#6 Higher temperature internal materials (no way to retrofit the CFM-56 to the same temperatures)
#7 Wide cord low turbine blades (far more extreme in the LEAP-1B to cut the number of low turbine stages). A 7 stage low turbine is INSANE! (-1A/-1C only)
#8: 50:1 overall pressure ratio (about the same in the PW1100G, just very different ways to get there)
#9: incredibly short combustor technology (squish the engine shorter and thus lighter)
#10: large fan diameter (78" versus 81.81" in the PW1100G) Hence why the LEAP is 11:1 bypass and PW1100G is 12.5:1
#11: Ability to grow to 35k of thrust (not yet certified, but neither is Pratt)
#12: electric (vs. pneumatic or fuel) driven actuators. A step drop in maintenance costs (and two motor sizes on the engine to simplify spares, IIRC. Instead of one actuator on the TCCV, another on the the nacelle anti-ice, another on the wing anti-ice. Little is done 'old school' except for backpressure regulators that I'm aware of.

For myself, the fan technology is amazing. It allows a far higher RPM low spool than I thought possible. Thus, a far more efficient low spool to compete with the GTF.
The next was the variable cycle technology (variable high turbine cooling). That is someone proposed by Whittle we're finally seeing in engines! Finally!

Yes, there were other changes, but the engine architecture is radically different from the CFM-56.

Yes, a different list.

Thanks for the fully detailed explanation lightsaber.

#5 I was never knew about that, Very interesting concept by the way.
Hope #6 is due to the use of Ceramic Matrix Ccomposites (CMC) for the Turbine blades.
In #7, hope it should be in the other way, according to my memory LEAP 1A got 7 HPT stages and 2 LPT stages.(IIRC )

#5 was top secret by GE. Needed to compete with the GTF. Pratt tried a variable fan nozzle, but decided it wasn't worth the effort this generation. (I disagree, but oh well... I wasn't making the decision).
#6, the higher temperatures, is due to metal research. The current LEAP-1A will benefit from future CMCs. Just as Pratt has promised a CMC PIP for the PW1100G. This sales race is way off.
#7, the HPT is two stages. It is the low turbine that has way more stages than normal for a single isle engine. Much of this is due to a step change in hollowing out the blades, which changes the optimum number of low turbine stages due to less weight (and cost) per stage. Some is due to better blade shapes (more efficient per blade, so the benefit of adding more rows adds up).

Lightsaber

skywalker92 · Wed Nov 15, 2017 1:56 am

lightsaber wrote:
skywalker92 wrote:
Balerit wrote:

It is used to cool the hydraulic oil in the CSD (constant speed drive that drives the electrical generator). Here is a link to a nice explanation of how they work:

http://www.k-makris.gr/AircraftComponents/CSD/C.S.D.htm

Thanks for the awesome link Balerit, appreciate it.

lightsaber wrote:
Major changes:
#1 is the higher RPM high compressor.
#2 is the two stage high turbine (allowing for a higher pressure ratio high compressor)
#3 is scimitar blades
#4 A completely different fan concept brought on by materials and aerodynamic improvements.
#5 variable cycle cooling of the high turbine (less cooling during cruise)
#6 Higher temperature internal materials (no way to retrofit the CFM-56 to the same temperatures)
#7 Wide cord low turbine blades (far more extreme in the LEAP-1B to cut the number of low turbine stages). A 7 stage low turbine is INSANE! (-1A/-1C only)
#8: 50:1 overall pressure ratio (about the same in the PW1100G, just very different ways to get there)
#9: incredibly short combustor technology (squish the engine shorter and thus lighter)
#10: large fan diameter (78" versus 81.81" in the PW1100G) Hence why the LEAP is 11:1 bypass and PW1100G is 12.5:1
#11: Ability to grow to 35k of thrust (not yet certified, but neither is Pratt)
#12: electric (vs. pneumatic or fuel) driven actuators. A step drop in maintenance costs (and two motor sizes on the engine to simplify spares, IIRC. Instead of one actuator on the TCCV, another on the the nacelle anti-ice, another on the wing anti-ice. Little is done 'old school' except for backpressure regulators that I'm aware of.

For myself, the fan technology is amazing. It allows a far higher RPM low spool than I thought possible. Thus, a far more efficient low spool to compete with the GTF.
The next was the variable cycle technology (variable high turbine cooling). That is someone proposed by Whittle we're finally seeing in engines! Finally!

Yes, there were other changes, but the engine architecture is radically different from the CFM-56.

Yes, a different list.

Thanks for the fully detailed explanation lightsaber.

#5 I was never knew about that, Very interesting concept by the way.
Hope #6 is due to the use of Ceramic Matrix Ccomposites (CMC) for the Turbine blades.
In #7, hope it should be in the other way, according to my memory LEAP 1A got 7 HPT stages and 2 LPT stages.(IIRC )

#5 was top secret by GE. Needed to compete with the GTF. Pratt tried a variable fan nozzle, but decided it wasn't worth the effort this generation. (I disagree, but oh well... I wasn't making the decision).
#6, the higher temperatures, is due to metal research. The current LEAP-1A will benefit from future CMCs. Just as Pratt has promised a CMC PIP for the PW1100G. This sales race is way off.
#7, the HPT is two stages. It is the low turbine that has way more stages than normal for a single isle engine. Much of this is due to a step change in hollowing out the blades, which changes the optimum number of low turbine stages due to less weight (and cost) per stage. Some is due to better blade shapes (more efficient per blade, so the benefit of adding more rows adds up).

Lightsaber

Regarding #7 this says it in the other way,
https://www.safran-aircraft-engines.com/commercial-engines/single-aisle-commercial-jets/leap/leap-1a

What I have noticed is RR Trent 700 and IAE V2500 has designed their engines with more stages in the outer spool(s) (LP,IP compressor/Turbine) while CFM 56 and LEAP 1A in the other way arround, they got more stages in the inner most spool.

WIederling · Wed Nov 15, 2017 10:03 am

skywalker92 wrote:
What I have noticed is RR Trent 700 and IAE V2500 has designed their engines with more stages in the outer spool(s) (LP,IP compressor/Turbine) while CFM 56 and LEAP 1A in the other way arround, they got more stages in the inner most spool.

Trent 700 is a three spool design. partitioning will be different in still another way.

Q2: Lightsaber,
is there anything readable around on metrics that determine spool partitioning?

lightsaber · Wed Nov 15, 2017 11:38 am

WIederling wrote:
skywalker92 wrote:
What I have noticed is RR Trent 700 and IAE V2500 has designed their engines with more stages in the outer spool(s) (LP,IP compressor/Turbine) while CFM 56 and LEAP 1A in the other way arround, they got more stages in the inner most spool.

Trent 700 is a three spool design. partitioning will be different in still another way.

Q2: Lightsaber,
is there anything readable around on metrics that determine spool partitioning?

Widebody engines will have more turbine stages and a higher pressure ratio. What is impressive about the LEAP is that the narrowbody engine has the stages.

As to positioning of stages (which spool), that is an art and a science. The higher the mach #, the more effective a stage is. But there is a limit on a high spool as adding more early stages slows the later stages and eventually the efficiency drops. RR having a triple spool had an advantage. The booster compressor (low compressor), was at a much higher RPM than the high compressor. RR previously was limited by how much compression could be done by the work from one turbine row. They are going forward with two row turbines. Although the Trent XWB did two stages in the IP turbine.

Why the changes? The high turbine must be cooled. In prior designs (including the XWB), the Intermediate turbine avoids cooling by aggressive material selection. The next triple spool will have a two stage high turbine. RR is just going for pressure ratios where one more turbine stage requires cooling. Somewhere there is a thread where I predicted the XWB would have a two stage high turbine (it doesn't, it is one stage). But RR figured out how to almost get the same pressure ratio doing the boost on the intermediate turbine.

Right now the limit on the pressure ratio of an intermediate or high turbine is about 29:1. That is slowly creeping up with blade technology improvements. To get today's over 50:1 pressure ratio engines requires a low compressor (often skipped in business jet engines as a cost savings venture).

7673mech · Thu Nov 16, 2017 6:56 pm

Balerit wrote:
skywalker92 wrote:
Balerit wrote:
#4 is probably an oil cooler.

Thanks Balerit

Is it for ACOC use?

It is used to cool the hydraulic oil in the CSD (constant speed drive that drives the electrical generator). Here is a link to a nice explanation of how they work:

http://www.k-makris.gr/AircraftComponents/CSD/C.S.D.htm

Except its an IDG.

Balerit · Thu Nov 16, 2017 7:27 pm

7673mech wrote:
Balerit wrote:
skywalker92 wrote:
Thanks Balerit

Is it for ACOC use?

It is used to cool the hydraulic oil in the CSD (constant speed drive that drives the electrical generator). Here is a link to a nice explanation of how they work:

http://www.k-makris.gr/AircraftComponents/CSD/C.S.D.htm

Except its an IDG.

Old habits die hard,

WIederling · Fri Nov 17, 2017 9:53 am

lightsaber wrote:
...........

Thank you very much!

What is new in CFM LEAP-1A

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