J-10 Thread III (Closed to posting)

[delft]

MiG-29, some aircraft with some pressure recovery at some Mach number will have a much higher thrust at 8000 meters than withe the same pressure recovery and Mach number at 16000 meters altitude. Do you understand how a jet engine works?

 

[latenlazy]

Now if you want a fighter that will fly Mach 2.35 like the MiG-29 or F-14 then you need a a multishock ramp.

Correction, you need multiple shock generators, and a plane with a DSI is not mutually excluded from having that.

 

[Engineer]

Mach 1.6-1.8 is a more tolerable and efficient speed, the Rafale for example has a intake capable of Mach 2, however it flies at mach 1.8, the reason is efficiency.
An expert in experimental aerodynamics, he was one of the inventors of the Rafale air intake, the first to be capable of achieving Mach 2 flight without the need for any additional devices

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At 100% pressure recovery the jet has a static thrust of 100%, what does it mean?
It means the Al-31 delivers its 12500kg of thrust, but at .95, that falls between 11900kg thrust to 11700kg of thrust, at .87, that falls even lower between 10900kg thrust and 10400kg of thrust.

It also means that when the force of air drag is lower than the thrust of 10400kg, the aircraft will continue to accelerate. The problem you have cited occurs on all other aircraft as their airspeed increases pass the optimal point on the pressure recovery curve. Your inference of pressure recovery coefficient decreases preventing airspeed from reaching M2.0 is flawed since the aircraft you have cited can reach M2.0 despite having reduce pressure recovery coefficient; you have proven yourself wrong.

Now make the numbers if your J-10B is flying fully loaded, then you need to burn more fuel to get the same thrust of lower speeds, also it means your engine is struggling more.

This has absolutely nothing to do with limitation imposed by DSI. J-10B flying fully loaded would imply exterior loads, and configuration with exterior loads incurs higher drag than a clean configuration. This phenomenon also occurs on other planes such as F-14 and F-15 as well, and these planes won't be able to approach top-speed with exterior mounts either.

Your knowingly attribution of higher drag caused by exterior loads to DSI is rather disingenuous! In simpiler words, you've just lied.

On fighters like F-4 you see relatively low numbers but here is the clue, the F-14 and F-15 that replaced it, fly at almost the same speed but have higher pressure recovery, better performance, payload and agility and more efficient SFC, so they do not spend as much fuel as the F-4.

Yet F-4D has a top speed exceeding M2.0 despite having lower pressure recovery, lower performance, lesser payload, lesser agility and worse SFC. Lower pressure recovery did not prevent F-4D from exceeding M2.0. Since J-10B pressure recovery coefficient at M2.0 is 0.87, and knowing that the aircraft has better performance, better agility, and better SFC than F-4D, there is nothing restricting J-10B from flying at M2.0.

So If you want to get a let us say 1:1 Thrust to weight ratio, you need a lighter jet, but remember as thrust goes down also speed, so you are spending more fuel just to try to keep up with the thrust needs.

A phenomenon that occurs on all fighter. It does not prevent some of these fighters from reaching and exceeding M2.0.

So ideally a fighter has a 100% pressure recovery and that is around Mach 1 or bellow, if you remember the F-16 is a dogfighter designed to fly at Mach 0.8 most of the time.

Rafale as F-18 fly slower than the F-16 simply to save fuel and increase payload that translate into longer range, lower maintainance and cheaper operation for the engine, it means also longer service life.

Your claim that slower airspeed increases engine service life still remains an unsubstantiated claim.

Now if you want a fighter that will fly Mach 2.35 like the MiG-29 or F-14 then you need a a multishock ramp.

False. You only need to generate multiple shocks. For example, SR-71 did not employ ramps. The

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said the following with regards to DSI:

The design principle for the bump is to design a compression surface similar to the cone flow described above and use the known flow fields behind conical shocks to achieve desirable results. The cone flow produces an isentropic compression which is a multi-shock compression (figure 7). The bump has pressure gradients which are spanwise and these help to redirect the boundary layer.

 

[MiG-29]

MiG-29, some aircraft with some pressure recovery at some Mach number will have a much higher thrust at 8000 meters than withe the same pressure recovery and Mach number at 16000 meters altitude. Do you understand how a jet engine works?

pressure recovery is just a ratio, lower altitude have more air density, higher mass flow.

 

[Totoro]

Moderators, is it possible to move all of this discussion to another thread? I come here to read about J-10 news, I hope it's not too much to ask that i don't have to rummage through tons of unrelated posts before i get to J-10 matters?

 

[delft]

pressure recovery is just a ratio, lower altitude have more air density, higher mass flow.

Why did you then mention thrust without mentioning the circumstances under which that thrust was achieved?

 

[MiG-29]

Why did you then mention thrust without mentioning the circumstances under which that thrust was achieved?

because the loses are regardless of altitude, they represent a ratio of loss

 

[delft]

Thrust depends very much on altitude and Mach number.

 

[A.Man]

No Idea At All

 

[SteelBird]

Great find, A.Man.

This J-10 is double seated and the nozzle look definitely not AL-31 to me. So, it is a WS-10 series.