Chapter 1329 Seek inspiration from the mistakes of others
Although it suffered a huge impact during the disintegration and subsequent falling into the water surface, perhaps due to the location of the location, there was not much irreversible air -proofing tablets made of light alloy. The bizarre change.
After scaning its shape into the database, the technicians did not carry out too much "rationalized deduction", and basically restored its original appearance.
This is undoubtedly a huge benefit for subsequent analysis -
The rationalized deduction certainly has sufficient theoretical basis to support it, but the problem is that the American design may not be as reasonable as imagined.
"Academician, further analysis has proven that the reason why this thing can be drifted on the sea for a long time. In addition to the appearance is more suitable, another important reason is that the interior of the wall surface is also designed as a hollow structure." < br>
Xing Muchun pointed to the 3D modeling of most of the inlet roads on the screen, and introduced it to Chang Haonan:
"However, because there is no further specific information, it is impossible to judge whether these spaces are used for cooling liquid runways or designs simply for weight loss."
The latter moved closer to the monitor and stared at the series of triangular cross-sectional shapes on the cross-section diagram for a while:
"Unlikely is a coolant ..."
Chang Haonan shook his head:
"If the aircraft adopts liquid cooling, it will basically use fuel directly as the heat exchange medium. However, some water samples collected on the sea surface have been analyzed before. It is based on JP7 aviation fuel and mixed with some flammable metals. The... mixture made with metal oxide particles has poor fluidity. I'm afraid it needs a special fuel circulation system to maintain normal supply. It's hard to imagine that we have to go through such a winding flow path again..."
This analysis is quite reasonable, and Xing Muchun has not expressed opposition, but just shows a slightly confused expression:
"But there is currently no evidence that the Americans have mastered the same plasma heat dissipation technology as we do... If no additional cooling methods are needed, the aerodynamic heating of hypersonic flight alone is enough to cause the aircraft to expand due to thermal expansion and contraction. Stretched a few centimeters or more..."
Chang Haonan was quite reasonable about this. After all, he only had part of the wreckage in his hands. He couldn't dig into such technical details and had to focus on the key parts.
So I simply answered:
"After all, the design speed of the X51A is only about 6 Mach, and the pneumatic heating situation is not particularly serious. If you can calculate the distribution of thermal heat, you can still rely on structural design to resist ... In short Let the one -yard over the hospital manufacture the full -proportion of the pneumatic model according to this parameter, prepare the wind tunnel. "
Xing Muchun immediately stood up and left the computer room to return to the office to make a call.
And Jiang Zonglin, who was responsible for the operation of the wind tunnel and had been sitting on the side without speaking just now, also joined in now:
"There are many possibilities that may lead to the failure of testing. I don't know which part you are going to start testing from?"
Regarding this issue, Chang Haonan has planned to have a long time ago.
Therefore, he analyzed it almost without thinking:
"Judging from the characteristic flight parameters obtained by the radar, the X51A maintained normal flight for about 143 seconds, reached a final speed of Mach 5.45 and maintained it for about 9 seconds, and then almost without warning... at least on the flight trajectory Disintegrated suddenly without warning.”
"In this case, it is unlikely what cumulative problem is. The probability is that the working parameters of the ultra-combustion stamping engine are not normal from the beginning. After accumulating a critical point between Mach 5.4-5.5 Or cause of the sudden enhancement of the waves, which leads to a completely disrupted work cycle and eventually induced structured damage. "
"So, starting from the gas heating amount and inlet overflow resistance corresponding to different characteristic Mach numbers, if this is really the problem, the abnormality should be found quickly..."
Jiang Zonglin stood up after hearing this:
"Then I'll get ready right away!"
...
It should be said that Chang Haonan's luck is quite good.
Although the most likely cause of the accident has been preliminarily analyzed, qualitative analysis and quantitative calculation are always two different levels of difficulty.
Originally, he only prepared to take a look at the entire process of testing a few days ago. It was considered a preliminary understanding of the design level of the American peers on the other side of the ocean, and then put the main energy on the detailed design of the gliding type.
As a result, just a few starts on the first day, it blown out a set of side -by -side data ...
"Are you sure...the airflow entering the combustion chamber can exceed the speed of sound?"
Chang Haonan looked at the work cycle curve in front of him and asked the letter suspected to the two people beside him.
This question was so basic that the air in the wind tunnel control room was silent for a moment.
"Of course ..." Jiang Zonglin nodded:
"There is no way to do a complete wind tunnel test for a single airway compression surface, so we picked up a standard kiss cutter anterior body and an equivalent area of a standard The minimum conditions for stamping engines have been simulated to 5.5 Mach at the time of disintegration ... "
While he described, he brought out the organized wind tunnel running log from the computer:
"It can be seen that near the speed corresponding to the critical point of disintegration, the thermal congestion disappears, the intensity of the shock string in the isolation section decreases, the shock string in front of the combustion zone moves toward the entrance of the combustion chamber, and the airflow in the combustion chamber must have reached supersonic speed. ”
Indeed, there seems to be no problem from the running records.
"But these phenomena can only show that the exit of the ropper string has reached the supersonic speed. Because the border layer fails to fully attach the effect, the situation in the burning room is not necessarily ..."
"..."
Chang Haonan analyzed himself to himself, and the expression on his face became confused first, and then he quickly turned into a bright enlightenment.
"You see, at the critical point, the working cycle of the burning room is 0-3-4*-9*. The airflow that is compressed by the intake tract is first heated within the equivalent segment to 1 The heating of 1 until the fuel heat is completely released, the stuff disappears, which does meet the characteristics of the supersonic modulus. "
"But after crossing the critical point and reaching Mach 5.5, the working cycle in the combustion chamber instead became 0-3-3'-9'-9*, and the process from 3' to 9' is still a limit situation. The actual expansion The degree cannot reach the ideal value, that is, when the area is heated to congestion, the fuel heat has not had time to be completely released..."
There is no mistake in every song, one post, one content, one 6 one, one book, one book, take a look!
Actually, as early as the end of the first half of the sentence, the other two had found something wrong.
"Is this a typical subsonic expansion process?"
Xing Muchun exclaimed.
Chang Haonan was also quite surprised by this conclusion, so he did not rush to a conclusion, but went back and checked it again.
It is finally determined that there is no problem with the analysis process just now.
"So, as the speed gradually approached Mach 5.5, the scramjet engine of the X51A abnormally returned to the working state of sub-ramjet, causing the cycle to become abnormal, thermal congestion to reappear, and ultimately leading to structural problems somewhere. Disintegration..."
He initially surmised the entire process.
Of course, this is not the "cause" of the accidental accident, but it is also very close.
"If so, it can explain why the aircraft is limited by a 5.5 Mach speed wall for so long under the premise of the normal start of the ultra -burning stamping engine."
Xing Muchun's tone gradually became confused:
"But it's so strange...how could this happen?"
"This cannot be inferred from the shape of a section of the air intake..."
Chang Haonan gave the report gently on the table:
"It is possible that the scramjet engine took some tricks during the design process and wanted to obtain the highest possible pressure ratio in the isolation section through the transition mode. As a result, due to a small error, the cycle stability was insufficient, and the scramjet engine eventually broke away from the scramjet engine. status, it is also possible that the engine starting speed has not reached the preset value, causing a problem at the beginning of the cycle, or..."
Before talking about the third possibility, his voice stopped abruptly.
"What is possible ... what?"
Jiang Zonglin looked over curiously.
"It's not important."
Chang Haonan pulled the report in front of him again, took a pen from the side, and drew a few arrows on the cyclic parameter curve diagram:
"I suddenly thought that if we reverse this process, it was to allow the engine to be in the sub -speed cycle mode at the low speed section, and the high -speed section entered the supersonic cycle modal. Two features "
(End of this chapter)