Kaveri NG Engine : Developmental Gas Turbine Engines upto 130 kN thrust class at GTRE, Bangalore

[Olaf One-Brow]

• Lastly consider one more case like EJ200 versus M88 case. The EJ200 gives a much higher T/W, a very high climbing rate and a superb acceleration. But doing so, it lights up a lot more due to heat emissions. Like this below

What type of camera was the Rafale shot caught on?

This one was on a typical day/night camera and not an IRST, FLIR or any other specialized optics.

It looks "cool" doesn't it? If you didn't know better you'd say this Rafale's IR signature is significantly suppressed. But it's not, it's just that a different type of camera is playing a nice trick.

We see in a hovering F-35 that its signature is brightest near the F135, so that a Rafale is brightest near its active engine isn't to be unexpected, but the airframe of this F-35 itself isn't moving a whole lot and isn't generating a lot of friction either, so the body remains cool by comparison.

The EOTS is quite hot, might want to invest in better cooling for the electronics.

A maneuvering aircraft like the Rafale in that photo you posted seems exaggerated and I suspect it's more camera trickery then anything else.

 

[Aero]

@Eminent Mainstream Media @Nilgiri

• We must be very careful when computing the T/W ratio.
• In general airframes and engines are produced by different manufacturers and the same engine can go into different airframes, thus T/W ratio of the engine alone is normally found in open literature sources.
• High T/W is an indication surely but when determining the performance of the aircraft, the important factor is the overall T/W of the aircraft, not just the engine alone.
• Another point to note is the thrust of an engine decreases with altitude while the weight remains constant, so this ratios for engines are often quoted at sea level static conditions, which give the maximum value that the engine will produce.
• Lastly consider one more case like EJ200 versus M88 case. The EJ200 gives a much higher T/W, a very high climbing rate and a superb acceleration. But doing so, it lights up a lot more due to heat emissions. Like this below
• 
• 
  
  
• The first one is EF versus second one rafale
• This is where it was discussed - https://defence.pk/threads/dassault...ussions-thread-2.351407/page-299#post-8567642
• Also dont forget the SFC angle for fuel consumption versus thrust needed.

So it has advantages as well disadvantages ...

Why in case of rafale (even it is flying with AF burners ) doesn't seem to be any heat present at points directly under attack from air.
These points like leading edge, nose should be somewhat hot?
Do you really believe they can provide so much better cooling in any case to appear like that in thermal vision?

Its not only about thrust. A significant consideration are issues like creep which affect MTBO (serviceability of the engine). I mean there is a real qualitative difference between western and russian engines of the same thrust and T/W class for exactly that reason.

For that difference better metallurgical techniques & materials are needed. If we needed to increase mean time b/w overhauls. In case of Russian engines we should have procured parts for regular consumption in large quantities to keep higher up time.

 

[Malik Alashter]

So, when we going to see kaveri?.

 

[PARIKRAMA]

Why in case of rafale (even it is flying with AF burners ) doesn't seem to be any heat present at points directly under attack from air.
These points like leading edge, nose should be somewhat hot?
Do you really believe they can provide so much better cooling in any case to appear like that in thermal vision?

The above picture shows how dual cooling channel of M88 engine reduces the thermal effect and how it reduces the heat signature in the exhaust system by cooling it

Compare it with EF EJ200 engine above where it shows a single cooling channel and high TWR resulting in the engine exhaust and fuselage glowing IR signature.


https://defence.pk/threads/dassault...ussions-thread-2.351407/page-299#post-8567642

The cooling channel cools the area and see how temperature drops from red to green yellow zone in the area highlighted

So basically its a combination of extra cooling channel and thermal signature reduction techniques.

The F35 VTOL is massive engine in terms of thrust.. Of course reduction techniques are used there but such a thermal signature cant be negated completely. .. FLIR captures this perfectly even though its much closer. EJ200 in EF with single cooling channel , maximum thrust focus, reduced weight of the engine already to retain such a high number.

 

[Aero]

The above picture shows how dual cooling channel of M88 engine reduces the thermal effect and how it reduces the heat signature in the exhaust system by cooling it

Compare it with EF EJ200 engine above where it shows a single cooling channel and high TWR resulting in the engine exhaust and fuselage glowing IR signature.


https://defence.pk/threads/dassault...ussions-thread-2.351407/page-299#post-8567642

The cooling channel cools the area and see how temperature drops from red to green yellow zone in the area highlighted

So basically its a combination of extra cooling channel and thermal signature reduction techniques.

The F35 VTOL is massive engine in terms of thrust.. Of course reduction techniques are used there but such a thermal signature cant be negated completely. .. FLIR captures this perfectly even though its much closer. EJ200 in EF with single cooling channel , maximum thrust focus, reduced weight of the engine already to retain such a high number.

But my question was about entire body/external surface of the plane being almost being invisible to FLIR.

Air will strike many areas of plane and then run over from rest when flying (HBL/TBL formation & friction will be there). This will result heating of these component/parts from outside but still Rafale was nearly invisible. You can control and coll internal heat but how you overcome heat generated outside or on plane exterior as that will tend to head external surface.

>>I checked that Rafale thread beforehand when you pointed someone previously in this thread to go there but still had doubt about it so asked.

PS: Will you be kind enough to tag me in your new threads as they are rich in content and particularly of my interest.

 

[Nilgiri]

But my question was about entire body/external surface of the plane being almost being invisible to FLIR.

Not sure about the picture in question exactly.....but there are filters you can run FLIR data through to take out the effects of skin heating etc.

I still have my doubts as to how much improvement there is in the cooling of the whole system by dual channel as opposed to single channel. Its pretty closely guarded stuff overall....so the pictures may be more influenced by PR basis than straight up neutral comparison.

 

[Aero]

@Nilgiri
But we can agree that heating of skin/external surface will be there. (In pic Rafale is using Afterburners)

I still have my doubts as to how much improvement there is in the cooling of the whole system by dual channel as opposed to single channel. Its pretty closely guarded stuff overall....so the pictures may be more influenced by PR basis than straight up neutral comparison.

I also think they will not supposedly leak/give away any real data about actual Thermal signatures. So, this may be somewhat modified or taken under supervised conditions.

 

[Nilgiri]

@Nilgiri
But we can agree that heating of skin/external surface will be there. (In pic Rafale is using Afterburners)

Sure it will be there....but it depends on

a) how much delta T occured since afterburners turned on etc

b) you can play around with the overall gain settings and make the skin friction level appear relatively grey

Like I said its a bit dishonest to compare stuff like this picture to picture. We have no idea about the conditions the pics were taken in and what processing they may have been subject to.

 

[Aero]

a) how much delta T occured since afterburners turned on etc

In case of fractional ΔT we will see a jump for thermal readings however in case of higher ΔT curve will tend to stabilize (For a fixed altitude & Speed). So,if quite of time is elapsed we may get a average heating of surface.

b) you can play around with the overall gain settings and make the skin friction level appear relatively grey

With higher speed,flow will be turbulent around contact surfaces that means higher Reynold's No. directly affecting Skin Friction Coefficient. ====>> heat
http://adg.stanford.edu/aa241/drag/skinfriction.html
General Relation (For a flat plate though)

Like I said it's a bit dishonest to compare stuff like this picture to picture. We have no idea about the conditions the pics were taken in and what processing they may have been subject to.

I was also thinking the same.

 

[Nilgiri]

In case of fractional ΔT we will see a jump for thermal readings however in case of higher ΔT curve will tend to stabilize (For a fixed altitude & Speed). So,if quite of time is elapsed we may get a average heating of surface.

Yah and that average heating can be gained out by filters.

I have had to do so myself (different system though) by using filters to play around with what a thermal picture looks like (to make certain things stand out/contrast etc).

 

[Aero]

by filters.

Sorry, i may require a bit of explanation here, if you can spare time

 

[randomradio]

What have you got to say about weight- I presume Its the dry weight- 2170 kg

With 130 kN full thrust- T/W is 6.1
With 90 kN dry thrust- T/W is 4.2

As per current specifications Kaveri with dry weight of 1235 kg

With 52 kN dry thrust- T/W is 4.3
With 80 kN dry thrust- T/W is 6.6

Kaveri in present form seems to be a better performing engine when It comes to T/W ratio in comparison with this so called next Gen- Kaveri-

Another wastage of Public money I see here- unless there is some misprinting about the weight-

Those are just the upper limits. Nothing special there.

 

[Nilgiri]

Sorry, i may require a bit of explanation here, if you can spare time

http://link.springer.com/chapter/10.1007/978-3-319-11331-9_15#page-1

There are much more brutal filters than just noise-reduction ones explained here (click look inside for a synopsis)....that follow the same concept but skew entire bands of temperature. Its mostly used in low delta T environments (for science/research)....but someone can easliy use it for a large delta T environment for PR purposes/manipulation.

 

[PARIKRAMA]

@Aero

• What you are pointing is Airframe Heating - the heating due to skin friction is a function of the Mach number especially with afterburners pushing the plane to max speed
• The wavelength of IR energy given out due to this heating is about 8.6 x 10-6 metres (m). This wavelength is absorbed by atmospheric gases and minute suspended particles. Its transmittance increases at higher altitudes as the density of the air reduces. Thus, this IR signature is of greater importance at higher altitudes and high Mach numbers.
• The airframe heating due to friction increases as the speed of the aircraft increases. In earlier times due to relatively lower speeds of aircraft and the then less sophisticated IR seeker technology this heating was ignored.
• However, with development of more advanced IR detectors and seekers that are able to pick up the longer IR wavelengths emitted by airframe heating and the increase in aircraft speeds of operation it has become necessary to address this aspect of the IR signature also.
• All parts of the airframe do not heat up uniformly. It has been found that maximum heating occurs on the sharper parts of the aircraft that face into the airflow such as wing leading edges, air intake lips and sharp nose sections.
• One way of reducing this signature is by careful design to eliminate potential heating hot spots.
• Requirements to design in adequate manoeuvrability are likely to impose limits on the amount of elimination of heating hot spots that would be possible through reshaping of the aircraft.
• Another method is to conduct heat away from hot spots giving a more uniform and lower temperature over the airframe and thus pushing the IR wavelengths higher.
• Fuel flowing in a network of fine pipelines below the skin of the aircraft in hotspots may be used for this purpose as may Radar Ablative Paints, which by their nature are able to conduct heat, and some composite materials.
• The Lockheed A-12/SR-71 “Blackbird” at its highest speeds, of close to Mach 3.0, subjected its airframe to temperatures as high as 500° C. In this aircraft fuel flowing in pipelines running under the skin was used to conduct heat away from its friction heated surface in addition to radar ablative paints in order to reduce the heating and the IR signature.
• In F35 its basically the same fuel technique learned from SR-71 timeline.

Source:
Stealth technology and its effect on Aerial warfare by V Kapur

Edit: I cannot confirm what filters are used in that image as its beyond our capability to know atm.. Its not apples to apples comparison but just a rough estimate/guesstimate. Thats the gist of what you and @Nilgiri are discussing

 

[Aero]

http://link.springer.com/chapter/10.1007/978-3-319-11331-9_15#page-1

There are much more brutal filters than just noise-reduction ones explained here (click look inside for a synopsis)....that follow the same concept but skew entire bands of temperature. Its mostly used in low delta T environments (for science/research)....but someone can easliy use it for a large delta T environment for PR purposes/manipulation.

Image filters,duh, i thought they used something ,that i am completely aware of ,on aircraft structure, Silly me.
Thanks