Actually...that determines acceleration, not top speed. Top speed for a propulsion based engine is determined by the exhaust velocity, since motion is derived from momentum. If you're gaining velocity by means of action-reaction momentum transfer limits your top speed. You can't go faster than the how fast you're throwing out the matter you're pushing off of.
SDF Aerospace and Aerodynamics Corner
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Engineer
Major
Surge and flame outs can occur on all aircraft including the F-14 and F-15. These are not phenomenons that only occur on J-10 and J-20.
An aircraft that does not usually fly at Mach 2.0 but can fly at Mach 2.0 is still an aircraft that can reach Mach 2.0, period. F-4D uses inlets that have a pressure recovery ratio of 0.87, the same ratio that DSI is quoted to have in 2005. Hence, F-4D can reach Mach 2.0 means an aircraft with DSI discussed by the paper can fly at Mach 2.0. Note that in obtaining the pressure recovery ratio, the inlet design and airflow within is already taken into account. There is no need to bring them up a second time for consideration. From your own :
Nasa said:
That's blatantly false. F-14's pressure recovery ratio is at 0.98 only when the aircraft is flying at Mach 0.6. As speed increases, the ratio decreases just as it would on any other aircraft. At Mach 1.8, you see no aircraft in the graph as a ratio of higher than 0.95.
F-22 only flies at a maximum quoted speed of Mach 2.25, so there is no reason why J-20 needs to fly faster than this speed. However, whether J-20 can actually reach Mach 2.5 has no relevance whatsoever as to the discussion at hand, as J-20 flying at Mach 2.2 will still be faster than Mach 2.0 and debunk your claim.
Note that the quoted pressure recovery in that 2005 paper is 0.91 at Mach 1.8. Looking up the above graph, the performance at this speed is same at F-104, another fighter that can fly in excess of Mach 2.0.
Engineer
Major
No. Drag vs. thrust determines acceleration. When thrust is greater than drag, then the aircraft accelerates. When thrust equals to drag, aircraft stops accelerating. Top-speed is limited by the , and when it is equal to the aircraft's airspeed, no thrust can be produced.
The thrust of engines that you see are measured with respects to sea-level at zero airspeed. It changes depending on altitude and airspeed.
MiG-29
Banned Idiot
Surge and flame outs can occur on all aircraft including the F-14 and F-15. These are not phenomenons that only occur on J-10 and J-20.
An aircraft that does not usually fly at Mach 2.0 but can fly at Mach 2.0 is still an aircraft that can reach Mach 2.0, period. F-4D uses inlets that have a pressure recovery ratio of 0.87, the same ratio that DSI is quoted to have in 2005. Hence, F-4D can reach Mach 2.0 means an aircraft with DSI discussed by the paper can fly at Mach 2.0. Note that in obtaining the pressure recovery ratio, the inlet design and airflow within is already taken into account. There is no need to bring them up a second time for consideration. From your own :
That's blatantly false. F-14's pressure recovery ratio is at 0.98 only when the aircraft is flying at Mach 0.6. As speed increases, the ratio decreases just as it would on any other aircraft. At Mach 1.8, you see no aircraft in the graph as a ratio of higher than 0.95.
F-22 only flies at a maximum quoted speed of Mach 2.25, so there is no reason why J-20 needs to fly faster than this speed. However, whether J-20 can actually reach Mach 2.5 has no relevance whatsoever as to the discussion at hand, as J-20 flying at Mach 2.2 will still be faster than Mach 2.0 and debunk your claim.
Note that the quoted pressure recovery in that 2005 paper is 0.91 at Mach 1.8. Looking up the above graph, the performance at this speed is same at F-104, another fighter that can fly in excess of Mach 2.0.
Look you do not understand a bit of what is pressure recovery, the fighter with the highest pressure recovery has the highest thrust, lowest fuel consumption and less distortion, this means it has the lowest surge and engine stall probability.
In a F-104 versus a F-14 example, the F-104 will have higher risk of a flame out, higher risk of engine stall and surge, higher fuel consumption, lower thrust and higher engine maintainance per flight hours than the F-14 or F-15.
So what do engineers do? simple they designed multishock intakes and when they wanted Mach 3.2 well mixed compression intakes.
So to put it in perspective a B-70 or Sukhoi T-4 at Mach 3 fly efficiently while the F-4 at Mach 2,2 might experience an engine malfunction, a F-14 at Mach 2.2 will fly more efficiently, and the same is a MiG-31, in fact a MiG-31 can fly at Mach 2.3 around 15 minutes while the F-4 hardly will fly 1 or 2 minutes.
Максимальная скорость, км/ч:
на высоте 17500 м 3000 (М=2.82) max speed for MiG-31
Боевой радиус действия, км
при полете к на сверхзвуковой скорости 720 max range at supersonic speed, of course the speed is not Mach 2.8 but 2.3
на сверхзвуковой скорости (М=2.35) без ПТБ 720
around 19 minutes at Mach 2.35, but of course you have to consider landing time so probably 15-16 minutes at Mach 2.35
Of course a F-16 can achieve Mach 2, but at the expense of lower thrust, so it will reduce payload, range will also reduce due to higher fuel consumption and safety will reduce, it can have an accident more likely than a F-35 of JF-17 flying at Mach 1.6
Ah! by the way lockheed martin say :Speed Mach 2 class
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to branch off from the J-20 thread, an interesting topic
i haven't seen any forum talk about this in depth, because there is not many data, but we are brave souls ready to challenge the frontiers of the unknown
is the J-20 designed to be carrier capable with minor modification? is it a viable for carrier operations?
discuss
i haven't seen any forum talk about this in depth, because there is not many data, but we are brave souls ready to challenge the frontiers of the unknown
is the J-20 designed to be carrier capable with minor modification? is it a viable for carrier operations?
discuss
MiG-29
Banned Idiot
to branch off from the J-20 thread, an interesting topic
i haven't seen any forum talk about this in depth, because there is not many data, but we are brave souls ready to challenge the frontiers of the unknown
is the J-20 designed to be carrier capable with minor modification? is it a viable for carrier operations?
discuss
It is hard to know, but in my opinion and i say opinion meaning is not a fact just a mere opinion of mine, well if it is too heavy maybe not, Su-33 is a 33 tonnes machine but F-111 was a 44 tonnes, the US Navy cancelled the naval F-111 variant due to its weight, however if it can be lightened at around 30 tonnes and with very economical engines perhaps, because if it weighs 36 tonnes now naval modification might add weight.
So in my personal opinion, it is hard to make it naval.
JSF F-35 is lighter and naval but the US navy is not happy flying a single engined fighter from the deck.
But of course McNamara politics got their way so they will stick with it.
But my opinion they should have designed a 30 tonnes twin engine stealth fighter.
Engineer
Major
Likewise, DSI has a higher ratio than F-104 inlets at Mach 2.0. At Mach 1.8, the quoted ratio for DSI is 0.91, which is better than the ratio for F-4D. Like you said, better pressure recovery ratio allows for higher thrust, lower fuel consumption, less distortion, lower probability of engine surge and stall than an inlet design with lower ratio. Thus at Mach 1.8, DSI exceeds the performance of the variable-geometry intakes found on F-4D, while having slightly better performance at Mach 2.0. Therefore, given the inlets of F-104 and F-4D allow both aircraft to achieve Mach 2.0, there is no reason why DSI with better pressure recovery ratio cannot reach Mach 2.0. Your theory that DSI has an absolutely speed limit of Mach 2.0 is therefore debunked.
You also need to read up on what pressure recovery is. From :
NASA said:
An inlet that causes engine surge or stall more easily would be given a lower pressure recovery ratio. You were already proven wrong as comparing pressure recovery ratio does not show DSI or fixed-geometry intake as absolutely inferior. Trying to drag in the issues of engine surge and stall into the discussion is nothing more than restating a wrong theory.
Which is irrelevant because neither J-10B or J-20 needs to achieve Mach 3.2. Showing that X intake can achieve speed of Mach 3.2 does not constitute as proof that Y intake cannot reach or exceed Mach 2.0.
This doesn't negate the fact that F-4D's inlets allow the aircraft to reach Mach 2.0. The quoted figure of pressure recovery ratio for DSI in 2005 was 0.87 at Mach 2.0, similar to that to F-4D's inlets. Thus, there is no reason to believe that DSI cannot reach or exceed Mach 2.0.
Duration of flight has a lot to do with airframe design as well as thrust-to-weight ratio. It is not solely determined by pressure recovery ratio of the inlet(s). In any case, aircraft don't fly at maximum speed anyway, so your point on duration of flight at maximum speed is moot.
There is no indication that F-16 can actually achieve Mach 2.0, but I digress. This statement of yours says more about F-16's inlet than DSI. Just because one inlet design cannot reach Mach 2.0, that does not mean a completely different inlet design cannot reach Mach 2.0.
Any aircraft capable of flying in the range of Mach 2.0 to Mach 3.0 is Mach 2 class. It doesn't mean that to fly at or exceed Mach 2.0, one must employ variable-geometry intake as your theory says. In fact, the very example of F-22 proved your theory as incorrect, because F-22 doesn't use variable-geometry intakes.
Using bold letters and large font size is not going to magically turn your opinions into facts.
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MiG-29
Banned Idiot
To start i have not said DSI can not achieve Mach 2, the DSI used on the F-16 was tested up to Mach 2, what i said and is a fact on your own graph is trhe F-14 and F-15 intakes are better than the DSI at any speed, that includes the MiG-29 and Su-27.
So my point has been that the F-14 will operate its engine in a more efficient way than the JF-17 at Mach 2, which your own graph says.
i can prove you the MiG-31 has a very complex intake so efficient that the jet flies at a cruise speed of Mach 2.35 for theoretically speaking 19 minutes and practically 15-16 minutes.
DSI has only advantages over conventional designs in the transonic area, so a F-16 with is pitot intake will be slightly less efficient than J-10B at speeds of Mach 0,9-1.2, however at speeds of Mach 1.7 the intake suffers greatly.
Now saying to me DSI is super good for everything because it is used on J-20, J-10B or JF-17 and these are chinese jets and you like them shows you can not understand the DSI design limits and advantages, the DSI has lower weight, requieres less RAM in terms of gaps, it is simplier to build, has good performance at transonic speeds, that is true, but beyond Mach 1.7 intakes like those of B-70, F-14 or MiG-31 are superior in pressure recovery, thus are better fitted for such speeds than DSI
Of course you get upset with size why? because lockheed martin says F-22 flies at Mach 2, not Mach 2.5 or mach 2+, yeah that is your trouble.
What you are not understanding is the chinese paper is comparing the F-16 and J-10B in terms of performance with DSI and pitot tube, basicly saying F-16 with pitot tube intake gets lower pressure recovery at Mach 2. but it does not mean DSI will be better than an intake like those seen in F-14 or B-70 wich have 4 shock in the former and mixed compression on the later.
So i can not expect the MiG-29 will have lower pressure recovery at Mach 2.35 than a J-10B, simply because the intakes seen on MiG-29 or F-14 with 2D horizontal ramps of 3 or 4 shocks have a design limit of Mach 2.5, beyond that speed mixed compression is used as a more efficient design.
JF-17 and F-35 are designs where the designers know the more efficient and safe operation is at a max speed of Mach 1.7, Mach 2 is achieveable but it is not recommendable
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Engineer
Major
You are backtracking. Observe what you've said:
So I take this backtracking as your admittance that you are wrong? If so, then I am happy that we are finally moving forward in the discussion.
This is a strawman argument. Never have I contended the fact that F-14 inlets have higher pressure recovery ratio than DSI, if that's what you are implying. I have been consistently providing evidences to debunk your theory and showed that variable-geometry intakes do not have absolute superiority over DSI (or fixed inlets for that matter). Claiming that I have made a point which I didn't make is a strawman and isn't going to hide the fact that you were wrong in the first place. Furthermore, I have never used JF-17 in my argument; not even once. I have however, said that J-10B and J-20 can reach and exceed Mach 2.
Having a more complex inlet does not automatically implies more efficiency, since more complexity results in more weight. This means the engine has to work harder to push the aircraft forward -- to generate the lift that needs to maintain the aircraft's altitude. MiG-31's lack of maneuverability indicates that most of the lift goes into keeping the aircraft up with little margin to make the aircraft turns.
More complexity does not automatically means better, since the more complex variable-geometry intake on the F-4D has lower pressure recovery ratio at Mach 1.8 than the DSI discussed by the paper. In otherwords, DSI has more superior performance in this case.
Not only is this your own opinion, it is completely and blatantly false. The quoted pressure recovery ratio for DSI at Mach 1.8 is 0.91, which is higher than that of F-4D, and the ratio of F-4D's intake at this speed is in turn higher than that of an F-16. In otherwords, DSI is better than the variable-geometry intakes on the F-4D, that are in turn is better than the pitot intake on the F-16.
My challenge of your theory that variable-geometry intake is good for everything, and that DSI is not good for anything, does not automatically makes me claim that DSI is good for everything. What I have been doing is debunking your theories with facts and figures.
So far, we have seen DSI having superior pressure recovery ratio to F-4D's intakes at Mach 1.8, and having similar ratio at Mach 2.0. This already means variable-geometry inlets do not have absolute superiority in speed and efficiency over DSI, and your attempt to bring in Mach 3.0 inlets isn't going to alter that fact. So far, we have not seen any figures or facts on your part to back up your claim that DSI cannot reach/exceed Mach 2.0.
No where did Lockheed Martin say F-22 has a speed limit at Mach 2. F-15 can fly at Mach 2.0 as well, but that doesn't make F-15 top speed to be Mach 2.0.
Wikipedia said:
You assume your opinions as facts and you do not use logic. When you are proven wrong you get upset, start pulling random numbers out of thin air and use bold and large font size that don't add any value to your arguments. Well, that is your trouble.
LOL! This is entirely your own opinion. The didn't compared F-16 with J-10B. The abstract says it all:
Chinese Paper Abstract said:
If you are referring to , it made more comparison than just with F-16.
We do not know the pressure recovery ratio of the inlets from J-10B and MiG-29, but we do know that from quoted figures that DSI has better pressure recovery ratio than F-4D's intakes, and F-4D's intakes are of type 2D horizontal ramps with 3 shock waves. You cannot deny this.
JF-17 was designed with fixed inlets in the first place, and is meant to have similar speed performance with F-16. F-35 cannot go faster than Mach 1.7 because it uses an engine with higher bypass ratio. Claiming DSI has to stay below Mach 1.7 to have safe operation is just your opinion. Nothing indicates DSI cannot be used at Mach 2.0.
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MiG-29
Banned Idiot
You are backtracking. Observe what you've said:
So I take this backtracking as your admittance that you are wrong? If so, then I am happy that we are finally moving forward in the discussion.
This is a strawman argument. Never have I contended the fact that F-14 inlets have higher pressure recovery ratio than DSI, if that's what you are implying. I have been consistently providing evidences to debunk your theory and showed that variable-geometry intakes do not have absolute superiority over DSI (or fixed inlets for that matter). Claiming that I have made a point which I didn't make is a strawman and isn't going to hide the fact that you were wrong in the first place. Furthermore, I have never used JF-17 in my argument; not even once. I have however, said that J-10B and J-20 can reach and exceed Mach 2.
Having a more complex inlet does not automatically implies more efficiency, since more complexity results in more weight. This means the engine has to work harder to push the aircraft forward -- to generate the lift that needs to maintain the aircraft's altitude. MiG-31's lack of maneuverability indicates that most of the lift goes into keeping the aircraft up with little margin to make the aircraft turns.
More complexity does not automatically means better, since the more complex variable-geometry intake on the F-4D has lower pressure recovery ratio at Mach 1.8 than the DSI discussed by the paper. In otherwords, DSI has more superior performance in this case.
Not only is this your own opinion, it is completely and blatantly false. The quoted pressure recovery ratio for DSI at Mach 1.8 is 0.91, which is higher than that of F-4D, and the ratio of F-4D's intake at this speed is in turn higher than that of an F-16. In otherwords, DSI is better than the variable-geometry intakes on the F-4D, that are in turn is better than the pitot intake on the F-16.
My challenge of your theory that variable-geometry intake is good for everything, and that DSI is not good for anything, does not automatically makes me claim that DSI is good for everything. What I have been doing is debunking your theories with facts and figures.
So far, we have seen DSI having superior pressure recovery ratio to F-4D's intakes at Mach 1.8, and having similar ratio at Mach 2.0. This already means variable-geometry inlets do not have absolute superiority in speed and efficiency over DSI, and your attempt to bring in Mach 3.0 inlets isn't going to alter that fact. So far, we have not seen any figures or facts on your part to back up your claim that DSI cannot reach/exceed Mach 2.0.
No where did Lockheed Martin say F-22 has a speed limit at Mach 2. F-15 can fly at Mach 2.0 as well, but that doesn't make F-15 top speed to be Mach 2.0.
You assume your opinions as facts and you do not use logic. When you are proven wrong you get upset, start pulling random numbers out of thin air and use bold and large font size that don't add any value to your arguments. Well, that is your trouble.
LOL! This is entirely your own opinion. The didn't compared F-16 with J-10B. The abstract says it all:
If you are referring to , it made more comparison than just with F-16.
We do not know the pressure recovery ratio of the inlets from J-10B and MiG-29, but we do know that from quoted figures that DSI has better pressure recovery ratio than F-4D's intakes, and F-4D's intakes are of type 2D horizontal ramps with 3 shock waves. You cannot deny this.
JF-17 was designed with fixed inlets in the first place, and is meant to have similar speed performance with F-16. F-35 cannot go faster than Mach 1.7 because it uses an engine with higher bypass ratio. Claiming DSI has to stay below Mach 1.7 to have safe operation is just your opinion. Nothing indicates DSI cannot be used at Mach 2.0.
MiG-31 has a more effective intake for speeds beyond Mach 2, in fact if you read what the page says
Боевой радиус действия, км
operational radius km
при полете к на сверхзвуковой скорости 720
at flight at supersonic speed 720km
So its range is around 1420km at a speed of 2500km/hr, that is around 35 minutes flight, however considering landing it might 30 minutes.
This is the closest aircraft to a F-22, however MiG-31 uses afterburner and carries at least 20000kg in fuel.
Масса, кг:
пустого самолета 21820 empty weight 21820
нормальная взлетная 41000 normal take off 41000
максимальная взлетная 46200 max yake off weight 46200
боевая нагрузка - 3000 кг weapons load 3000kg
Try to catch a MiG-31, is a pretty hard thing specially now that it is armed with AA-12 and (R-37) AA-13.
Now DSI is well designed to reduce manufacturing and maintainance costs.
And you are pretty wrong, by achieving lower pressure recovery, it will have increased risks of engine failure and limit the flight time at top speed.
The F-104 and F-4D won`t fly as long as a MiG-31 at Mach 2.35 simply because their lower pressure recovery implies higher fuel comsuption and higher risk of engine damage, surge or flame outs.
On the F-104 by being a single engine aircraft, will meant fatal crashes if the only engine fails, on the F-4D it will mean less risk, but it will mean more maintainance, in fact you are so illogical as to claim for the US navy the F-4 was as good as the F-14! the F-14 was better simply because it meant higher reliability, in fact the F-14D was years ahead of Any F-4D or E but of course you want to prove at any cost.
DSI intakes are designed for speeds bellow Mach 2, Mach 2 is the upper limit of that intake type, for single engine fighters with DSI Mach 1.7 is the ideal top speed
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