gambit
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Wrong. I have always maintain the same position: Wait.Gambit, if I am just hoping that this aircraft is superior to the F-35, then you are just hoping that it's not.
If you wish it to be superior to the F-35, it would have to be in the same category as the F-35, which is a multi-role jack-of-all-trades fighter. It would have to be V/STOL capable, which is unlikely.
The problem for you is that you will find one or two things that this new aircraft is alleged to be 'superior' to the F-35 and you will blow it all out of proportions.
Yours is no 'theory' but merely a hope. And what I posted about the relationship between airframe and propulsion is established. You cannot dispute it.My theory: Aerodynamic differences were intelligently made to improve aerodynamic performance (although some had to be made for the obvious change from 1 to 2 engines). Your theory: Differences were made to compensate for poor engine performance.
Because they set the foundation on how to make an aircraft 'stealthy'.I don't know why you posted all those diagrams again of an un-stealthy aircraft. Clearly, the J-31 does not feature a single vertical stabilizer. Stop hiding behind your diagrams. If you say I don't understand something, then explain it. If you don't then it's not that I didn't understand; it's that saying I don't understand is your last ditch effort to confuse people who aren't sure if I'm right in calling your BS.
Think about it for a moment. How do you know to avoid something if you do not know how the thing works/behave/looks? The fact that you said that mean my attempt to explain things to you have failed. I presented the same materials to plenty of other people in training, on aircraft and in the classroom, and they get it. Why not you?
Too bad you do not understand. And yet you dare to participate...You just showed a picture of a civilian jet engine for no reason at all.
Yours is flawed is that YOU can make an assumption about a supposedly 'superior' airframe based upon looks alone. Mine is -- Not.
And here is why...
A turbine jet engine have four major sections:
- Compressor
- Combustion (Burner)
- Turbine
- Exhaust
Turbine Engines
The turbojet engine contains four sections: compressor, combustion chamber, turbine section, and exhaust.
This is a basic application of compressing air (Compressor), igniting the fuel-air mixture (Combustion), producing power to self-sustain the engine operation (Turbine), and exhaust for propulsion (Exhaust).
The first graphic in the above source illustrate all of the four sections in sequence of operations. Words in parentheses mine for clarity.
Refer back to that source...
The compressor types fall into three categories—centrifugal flow, axial flow, and centrifugal-axial flow. Compression of inlet air is achieved in a centrifugal flow engine by accelerating air outward perpendicular to the longitudinal axis of the machine. The axial-flow engine compresses air by a series of rotating and stationary airfoils moving the air parallel to the longitudinal axis. The centrifugalaxial flow design uses both kinds of compressors to achieve the desired compression.
The highlighted last sentence is significant: The centrifugalaxial flow design uses both kinds of compressors to achieve the desired compression.
Why is there a hybrid of the centrifugal and axial compressor types -- unless there are advantages and disadvantages for each? It is the compressor section, the physically foremost and first of four sections, that have a direct influence on airframe design.
Centrifugal compression works by 'flinging' pockets of air outward or perpendicular to the machine's longitudinal axis. We have the same thing on hot rods. The path or channel that these pockets of air travels to the combustion chamber gets increasingly narrower, creating higher pressure by the time the air pocket reached the combustion chamber. Centrifugal compressor is also known as 'radial' type compressor.
Axial compressor works by moving a continuous flow of air thru several stages of fan blades. Each fan stage is slightly different in blade airfoil aerodynamics to achieve compression thru the stages. Axial compressor can also be found in hot rods.
The differences between the two are illustrated here...
Compressors
Centrifugal compression method is much more tolerant of inlet airflow distortion/disruption than axial compression method. The disadvantage is that the centrifugal compression engine will have a much larger engine front face, which in turn will determine intake sizing, which in turn will affect fuselage dimension, which in turn will affect drag, which in turn will affect maneuverability and overall performance in all flight conditions.Centrifugal compressors, which were used in the first jet engines, are still used on small turbojets and turboshaft engines and as pumps on rocket engines. Modern large turbojet and turbofan engines usually use axial compressors.
Axial compression method produces a superior increase and constant rate of increase of pressurized air flow, instead of air pockets, than centrifugal compression method. The axial compression engine have a much smaller engine front face, which in turn will determine a smaller intake sizing, which in turn will affect fuselage dimension, and so on...The disadvantages are the intolerance of airflow distortion/disruption which limits inlet/intake design options to those that will minimize airflow distortion/disruption, and high reliance on precision blade aerodynamics and blade material durability.
ch10-3
And that explains the highlighted sentence in the NASA source, more so for the military fighter class aircraft where we want high maneuverability and are willing to expend resources to produce high quality engine blades.Especially in modern fighters that may have thrust-to-weight ratios in the order of 1, the inlet and its integration with the airframe exert a powerful influence on the overall aircraft design. The aim in engine-airframe integration is to minimize airplane drag, weight, and complexity and to maximize propulsion-system efficiency while, at the same time, ensuring that the aircraft mission requirements have not been compromised.
The axial turbine engine is smaller in diameter, which give us smaller inlet system regarding geometries of the cowl and boundary layer separation mechanism, which produces less drag because propulsion system induced drag is counted AGAINST installed thrust, or to put it another way, propulsion system induced drag equals to a reduction in installed thrust.
So now we have a conflict...
Uninstalled thrust is when the engine is standalone and have as much air as its diameter will allow. Installed thrust is when the engine is installed into the aircraft with an intake system which inevitably restricts air volume. Installed thrust is always less than uninstalled thrust. The greater we enlarge the intake system to give the axial turbine engine as much air volume as possible, the more complex and higher weight penalty the inlet system must be in order to slow inlet air down to .5 Mach for the engine to use, inevitably this will affect fuselage dimensions and contribute to radar cross section (RCS). If we design the intake system with drag and RCS as primary considerations, then we must reduce the intake system size, which will reduce installed thrust even more.
On the design team, the Propulsion side is going to argue for things that will get the engine to as close to theoretical output as possible. The Airframe and Radar sides, which will include aerodynamicists, are going to argue for things that will give the aircraft maneuverability and low RCS. There will be conflicting demands and with time constraints like any other business ventures, a decision has to be made that will compromise all sides.
Do you still think you can credibly divorce propulsion from airframe design? I do not use the word 'divorce' in jest. A 'marriage' is a union of two individuals, that while each can function alone, together they can accomplish much more. A 'divorce' is the separation that destroys whatever it is that they became that worked and was productive. A jet engine is useless if it not coupled to an airframe and an airframe is worthless if it cannot fly for lack of propulsion.
Ever heard of the term 'rubber engine'? No, it has nothing to do with the material called 'rubber' except in reference to elasticity.
An aircraft manufacturer is usually not an engine manufacturer. So when he design a new aircraft, given how integral is propulsion to airframe, despite your dismissal of this fact, he will contact the engine maker for the performance specs of the most up to date engine on the market. If the physical dimension of the real engine does not logically fit into his new airframe design, he will then logically scale up or down its physical dimensions to fit. But what if his inlet system reduces air flow into this hypothetical engine? Thrust is roughly proportional to intake air flow which is directly related to engine's cross sectional area. Sorry, but generally at the current technology level, reduced engine size naturally reduces thrust. Hence, the term 'rubber engine' because of its hypothetical elasticity before a physical airframe is actually made.
We even have software to help us in that task and is called a 'parametric deck'.
For examples...
Computer Deck - The GasTurb Program
The data describing the engine are created with GasTurb as an Engine Model File which is loaded during the deck initialization process. The Engine Model File contains all data necessary for doing off-design simulations, both for steady state and transient operation. Transient simulations can employ the control system as defined in the GasTurb model or run to a specified fuel flow or spool speed.
www.dtic.mil/dtic/tr/fulltext/u2/680013.pdf
Better parametric decking software can logically alter the engine's physical dimensions on the fly depending on the operator's inputs to alter things like airflow quantity or fuselage dimensions or even engine accessories relocation on the engine itself.The CARPET Deck is a computer program that simulates a basic parametric turbojet or turbofan. It can also be used to analyze the performance of a specific engine at discrete operating points if the total airflow is input along with the component characteristics of the engine.
The airframe-propulsion integration is so important that we want to do it as early into the design phase as possible and with today's CAD/CAM technology, we can have a reasonably accurate forecast on what we must do for the new aircraft even before the first piece of metal is struck.
SAC can copy the F-22 down to the exact millimeter but if there is not a PW-F119 equivalent in China and SAC installs something inferior, then this F-22 copy will fly like sh1t. So if SAC altered this copy or 'hybridized' it from something else in any way, it does not automatically mean the alterations are for improvements as you baselessly assumed. WE DO NOT KNOW. But the relationship between propulsion and airframe design is indisputably established and not just merely another 'theory' on equal footing to your baseless assumptions.
I do not expect you to understand anything I presented above. I do not even expect you to read them. The logical arguments and their sources are more to prove to the readers why you are wrong in your convenient assumptions than to change your mind that you are wrong. In your need to save face in front of fellow Chinese on this forum, you MUST dismiss NASA and other sources whereas I am committed to the truth: That you cannot divorce propulsion from airframe design and that you cannot simply look at this new Chinese fighter and make baseless assumptions alleging superiority of its design without considering its engine sources. Yours is the typical behavior of the Chinese members here: Proven wrong but refuses to admit it out of childish pride.
Looks like this 'Gramps' has better research skills and more credibility than you, young ignorant pup.