SDF Aerospace and Aerodynamics Corner

Engineer

Engineer

Major
Re: J-20... The New Generation Fighter III

MiG-29 said:
ii is not that simple, to put you and example 117 is a 14.5 tonnes thrust engine while f119 is a 15+ tonnes engine.

Pressure recovery means which engine will lose more thrust and spend more fuel.

If F-22`s pressure recovery is at Mach 1.7; 0.92, it will reduce its F119 thrust of 15.8 tonnes to something like 13 tonnes, first because the flat nozles reduce thrust around 10% or more and the pressure recovery thrust lose will be another 11%.

So pressure recovery is very important.
Click to expand...

Su-27 has similar intakes with Su-35S as well, and Su-27 cannot supercruise despite having variable-geometry inlets. F-14 and F-15 cannot supercruise either. Yet, F-22 can supercruise and does so using fixed inlets. This says two things. First, pressure recovery ratio isn't everything. Second, aerodynamics theory advanced enough for fixed inlet to function better than some variable-geometry inlets.

MiG-29 said:
If Su-35 has 14.5 tonnes of thrust in each 117 and has pressure recovery of 0.96 at Mach 1.8, it will lose around 6% of thrust and by having no flat nozzles, so the loses of the 117 will be lower at mach 1.8 than F119 at Mach 1.7.
Click to expand...

This is merely your opinion. There is no data about pressure recovery ratio of Su-35S vs. F-22. What we do know is F-22 top supercruise speed is Mach 1.8, whereas the expected supercruise speed of Su-35S with a clean configuration is around Mach 1.5. F-22 performs better and does so without needing variable-geometry inlets.

MiG-29 said:
Speed: The F-22's speed class is Mach 2.

Please, Log in or Register to view URLs content!


Maximal airspeed :
H=200 m, km/h 1,400
H=11,000 m , M 2.25
Please, Log in or Register to view URLs content!


so while it is true F-22 has more thrust, the intake of Su-35S is good to reduce thrust loses and fuel comsuption
Click to expand...

The phrase "speed class" is not the same as "maximal speed". Being in the class of Mach 2 means the aircraft can reach/exceed Mach 2.0. It serves as a nice way to not tell you what the maximum capability of the aircraft is.



Merry Christmas to you too.
 
MiG-29

MiG-29

Banned Idiot
Re: J-20... The New Generation Fighter III

Engineer said:
Su-27 has similar intakes with Su-35S as well, and Su-27 cannot supercruise despite having variable-geometry inlets. F-14 and F-15 cannot supercruise either. Yet, F-22 can supercruise and does so using fixed inlets. This says two things. First, pressure recovery ratio isn't everything. Second, aerodynamics theory advanced enough for fixed inlet to function better than some variable-geometry inlets.



This is merely your opinion. There is no data about pressure recovery ratio of Su-35S vs. F-22. What we do know is F-22 top supercruise speed is Mach 1.8, whereas the expected supercruise speed of Su-35S with a clean configuration is around Mach 1.5. F-22 performs better and does so without needing variable-geometry inlets.



The phrase "speed class" is not the same as "maximal speed". Being in the class of Mach 2 means the aircraft can reach/exceed Mach 2.0. It serves as a nice way to not tell you what the maximum capability of the aircraft is.



Merry Christmas to you too.
Click to expand...

The Su-35 supercruise thanks to several factors, but the more important is the engine, however pressure recovery will reflect the mass flow the engine in using, the thrust to weight ratio the engine it self achieves.

With a fixed intake the F-22 supercruises, true, but the speed the jet gets is still lower than what a MiG-31 or Su-35S can achieve, the su-35S will supercruise and higher pressure recovery will always help it to achieve higher yield at higher speeds thus higher top speed.
 
MiG-29

MiG-29

Banned Idiot
Re: J-20... The New Generation Fighter III

HKSDU said:
I will reply in this is their such thing as official figures for anything regarding PLA inventory numbers. I wasn't evening referencing or talking about WS-10, so don't bring that into play. Saying they are building this amount of number of J-10's based on orders for AL-31. Even if they have that many engines that, you don't look at the amount of engines bought but the capacity of the assembly line. I don't question they can build more J-10's per year, but it does seem to be slowing down a bit.

You even said that not all 500 have been delivered. You argue that ~200 is not right based on the fact that 500 will be acquired eventually once contract has been delivered. ~200 is around current numbers, i didn't say 200 will be built with 500 engines that will be eventually provided. Your assumptions is based of just one variable 500 engines, and you predicted 30-40 J-10 a year. If 30-40 J-10's a year you have just assumed that J-10 will be in production for 12-17 years.

Don't twist my post into an argument that suits yours.
Click to expand...

No do not misunderstand me i guessed my opinion upon the fact they are buying more Al-31s than the J-10 are thought to have been deployed.

Only that it seemed to me a bit wierd the have so many Al-31 and so few J-10s and most J-10 have a few years they are relatively new aircraft.
 
L

latenlazy

Brigadier
Re: J-20... The New Generation Fighter III

MiG-29 said:
No do not misunderstand me i guessed my opinion upon the fact they are buying more Al-31s than the J-10 are thought to have been deployed.

Only that it seemed to me a bit wierd the have so many Al-31 and so few J-10s and most J-10 have a few years they are relatively new aircraft.
Click to expand...
It's called an inventory requirement, which is why we've been pointing out that's it's not 1 new J-10 per new AL-31FN order.
 
Quickie

Quickie

Colonel
They're probably stocking up on the body chassis (plus other accessories) of the AL-31FN. We've heard news of them manufacturing themselves upgrade kits for the AL-31s engines but they would not go the trouble of manufacturing the chassis and some other accessories if it's much cheaper and much less hassle to just buy them rather than to design anew and manufacture them and having to face IP issues.
 
MiG-29

MiG-29

Banned Idiot
Re: J-20... The New Generation Fighter III

latenlazy said:
It's called an inventory requirement, which is why we've been pointing out that's it's not 1 new J-10 per new AL-31FN order.
Click to expand...

that is your personal opinion, which i do respect, but i do not agree time will tell.
 
P

paintgun

Senior Member
Mig29, the days of variable intake for fighter jets is over, no one will use it unless they have to anymore
it was a straightforward/effective solution but also inefficient, being needing a diverter, and ramp mechanism

DSI is 'new' because not everyone has(had) the computational software and hardware to do fluid dynamics simulation

it was all DSI after the F-16 DSI, it is just a coincidence that China is the one that came up with all the new designs lately, and thus become pejoratively associated with crap
the Russians? they have their own ways of doing things

i have no objection of you and Engineer continuing this discussion indefinitely, but i just feel that it's starting to sound like a broken record, with both firmly on their grounds and facts regarding this matter are indeed hard to be found

at least bring new stuffs, like this :

diverterless hypersonic intake
Please, Log in or Register to view URLs content!


does this mean a diverterless intake can work on any mach number it is designed for?
 
Last edited:
L

latenlazy

Brigadier
Re: J-20... The New Generation Fighter III

MiG-29 said:
that is your personal opinion, which i do respect, but i do not agree time will tell.
Click to expand...
I'm not expressing an opinion (I hardly do), but a logistical fact. Militaries are required to have inventory and spare parts for the purpose of maintenance and in the event of supply cutoff. The former is particularly important for regular operations. When an engine needs maintenance work you don't want the rest of the air frame to sit on the side grounded. You circulate a fresh engine from your inventory and install it in the air frame while you perform maintenance work on the originally installed engine. That way your military is always operating at 100% for both mission and training purposes.

paintgun said:
Mig29, the days of variable intake for fighter jets is over, no one will use it unless they have to anymore
it was a straightforward/effective solution but also inefficient, being needing a diverter, and ramp mechanism

DSI is 'new' because not everyone has(had) the computational software and hardware to do fluid dynamics simulation

it was all DSI after the F-16 DSI, it is just a coincidence that China is the one that came up with all the new designs lately, and thus become pejoratively associated with crap
the Russians? they have their own ways of doing things

i have no objection of you and Engineer continuing this discussion indefinitely, but i just feel that it's starting to sound like a broken record, with both firmly on their grounds and facts regarding this matter are indeed hard to be found

at least bring new stuffs, like this :

diverterless hypersonic intake
Please, Log in or Register to view URLs content!


does this mean a diverterless intake can work on any mach number it is designed for?
Click to expand...

Mig-29 doesn't understand that it's not about whether the intake is variable or diverterless that determines performance, but rather the specific shape and design of the variable/diverterless intake. I don't think he understands that different bump shapes and positions combined with different inlet cowls will generate different results...
 
Last edited:
MiG-29

MiG-29

Banned Idiot
paintgun said:
Mig29, the days of variable intake for fighter jets is over, no one will use it unless they have to anymore
it was a straightforward/effective solution but also inefficient, being needing a diverter, and ramp mechanism

DSI is 'new' because not everyone has(had) the computational software and hardware to do fluid dynamics simulation

it was all DSI after the F-16 DSI, it is just a coincidence that China is the one that came up with all the new designs lately, and thus become pejoratively associated with crap
the Russians? they have their own ways of doing things

i have no objection of you and Engineer continuing this discussion indefinitely, but i just feel that it's starting to sound like a broken record, with both firmly on their grounds and facts regarding this matter are indeed hard to be found

at least bring new stuffs, like this :

diverterless hypersonic intake
Please, Log in or Register to view URLs content!


does this mean a diverterless intake can work on any mach number it is designed for?
Click to expand...

DSI can work at any speed however jet engines can not work at any speed, the patent you presented is for a RAMJET or SCRAMJET, Ramjets do not need the flow at Mach 0.5 however turbofans and Turbojets do; Ramjets and scramjets can work at Mach 3, 4.5 or even higher Mach numbers but if you look at figure 1 it has a graph where it shows the turbojet mach limits, SR-71 uses ramjet thrust, this ramjet system allows it to fly at Mach 3 on cruise flight conditions.


As shown in FIG. 1, the performance 11 of aircraft withconventional turbojet engines deteriorates quickly as flight speed approaches Mach 3. Similarly, the performance 13 of conventionally configured ramjets and scramjets is also weak at flight speeds in the vicinity of Mach 3. However, a high speedaircraft configured with a DHI constructed in accordance with the present invention has a performance 15 with a significantly enhanced region of improvement 17 over conventional inlet designs. The turbojet, ramjet, and scramjet engine applications forthe DHI of the present invention include flight speeds of approximately Mach 2.5 to 10.




The DSI can work on a type of modern SR-71, with mixed system of turbojet-ramjet thrust
The engine used on the SR-71 Blackbird is called a turboramjet because it is a combination of a basic turbojet engine and a ramjet. Both of these engines are discussed in greater detail in a previous question on the different types of jet engines.
Please, Log in or Register to view URLs content!
 
Last edited:
MiG-29

MiG-29

Banned Idiot
Re: J-20... The New Generation Fighter III

latenlazy said:
I'm not expressing an opinion (I hardly do), but a logistical fact. Militaries are required to have inventory and spare parts for the purpose of maintenance and in the event of supply cutoff. The former is particularly important for regular operations. When an engine needs maintenance work you don't want the rest of the air frame to sit on the side grounded. You circulate a fresh engine from your inventory and install it in the air frame while you perform maintenance work on the originally installed engine. That way your military is always operating at 100% for both mission and training purposes.



Mig-29 doesn't understand that it's not about whether the intake is variable or diverterless that determines performance, but rather the specific shape and design of the variable/diverterless intake. I don't think he understands that different bump shapes and positions combined with different inlet cowls will generate different results...
Click to expand...

You are wrong i do understand perfectly the bump, what you do not understand how an intake works, they are not only creating shock waves to slow down the flow, but also controling the mass flow, a turbofan needs flow at Mach 0.5 to work, on a DSI you need to slow the flow at such speeds even if outside the inlet the air is flowing at supersonic speeds, you need to control the subcritical and supercritical states where pressure recovery losses can appear, plus flow mass control and bypass is needed for turbofans or any turbine.

These are needed technologies if you use turbines, F-14 and Su-27 for such a reason have bypass doors and SR-71 moves forward and backwards the intake cone.
 
You must log in or register to reply here.
Top