Chapter 1330 Dual-Mode Ramjet

Xing Muchun and others were not particularly shocked by Chang Haonan's new idea.

I just feel that this concept is somewhat unfamiliar.

In the entire hypersonic weapons project, except for the double-cone verification missile that was initially used for technical verification and experience accumulation, the boost-glide type, which has relatively low technical difficulty, is given priority, while the progress of the air-breathing type is relatively slow.

At present, only theoretical research and wind tunnel testing are being carried out on the tangent cone waverider used in the flight body, while the power system is still in the independent development stage.

Of course, it is only independent relative to the entire project team.

After all, the specific research and development tasks will still be undertaken by the Aviation Power Group and will not escape the control of Academician Chang.

But even at this point in time, there is still room for change.

Moreover, although the other main leaders of the hypersonic project are from the aerospace industry, aerospace and aviation are ultimately inseparable.

Apart from anything else, most people have heard that the Aviation Power Group is conducting preliminary research on a variable cycle fifth-generation aircraft engine.

Therefore, it is natural to link the two things together:

"Ramjet engines... also need variable cycles?"

Xing Muchun's background is in rocket overall design, so he was unfamiliar with the difficulty of purchasing the air-breathing propulsion technology tree, and used a not very accurate way to describe it.

Fortunately, the meaning is not much different.

"Your understanding should be correct, but the ramjet engine does not have the concepts of gas circulation and internal and external bypass, so it should not be called a variable cycle."

Chang Haonan corrected with a smile:

"Of course, if we can combine ramjet engines with traditional turbojet engines in the future, that's another story..."

As for the second half of the sentence, everyone unanimously chose to ignore it for the time being.

Considering the age of most people here, this current project is almost the battle of their careers, and being able to do it from beginning to end on the front line would be considered a success.

For long-term projects, even if they are willing to participate, it is highly likely that they will not be in their current capacity.

"What should it be named?"

Xing Muchun also became serious at this moment.

Chang Haonan did not give an answer immediately, but just lowered his head and thought for a moment.

He had a flash of inspiration after seeing the working cycle curve that he had just verified, but he didn't have a complete idea yet.

"The most obvious difference between a scramjet and a ramjet is the thermal working process in the combustion chamber... so it can probably be called a dual-mode ramjet, which can switch freely between the two working modes of ramjet and scramjet according to different flight conditions..."

Everyone remained silent, but nodded in approval.

"But Academician Chang..."

After some small talk, Jiang Zonglin got back to the point:

"After all, the variable cycle of a jet engine only requires an additional duct, which is still within the acceptable range of engineering design... This dual-mode ramjet engine is a combustion chamber design, including the compression-isolation section and the inner nozzle. You can't install two combustion chambers in it, right?"

One of the biggest advantages of ramjet engines is that they have a simple structure, do not have too many moving parts, and can withstand extreme flight conditions better.

If an extra combustion chamber is added for the sake of compatibility, it would be better to install two independent engines directly on the aircraft.

Chang Haonan showed a slightly playful smile on his face:

"Originally this was indeed an almost unsolvable problem... But thanks to the Americans' failure this time, it gave me a lot of inspiration."

He said as he quickly turned to a page in the report and then pulled out a few sheets of white paper from the printer next to him.

Seeing this, the others quickly gathered around.

"From a physical point of view, designing two combustion chambers for an engine is definitely not worth the effort, but we can thermodynamically divide the same combustion chamber into two by adjusting the distribution of different shock wave trains and boundary layer separation conditions and by adjusting the inlet duct and forebody cone..."

As Chang Haonan introduced the process, he drew a diagram on paper, but halfway through, his pen suddenly stopped:

"No, we need to divide it into three working states."

"The first is the pure subcombustion mode. In this case, the shock wave train in front of the combustion zone in the isolation section flow field is dominant, the shock wave train exit is subsonic, the boundary layer is completely separated, the diffuser is in normal working condition, and has two geometric throats. Pressure is provided by the normal shock wave system provided by the oblique shock wave of the diffuser."

"Then there is the transition mode, where the shock wave train in front of the combustion zone moves toward the combustion chamber entrance, the shock wave train exits at supersonic speed, and the boundary layer separation weakens, but it is essentially still in the working cycle of the subsonic ramjet."

At this point, he changed the subject and pointed to the test conclusions of the X51A flow channel structure next to him:

"At present, it seems that the Americans' understanding of the ramjet engine's thermal cycle is probably still superficial. In order to improve work efficiency, they chose a relatively high startup speed, but it was not high enough to ignore the transition stage. Instead, it made it more difficult to cross the sonic wall in the combustion chamber, and finally was forced to stay in the sub-combustion mode for a long time, and was stuck in this link."

"The purpose of our development of dual-mode ramjet engines is to reduce the pressure of the rocket booster stage and improve the flexibility of flight conditions. Therefore, the idea should be to induce and pass this stage as early as possible, preferably below Mach number 5.0. Otherwise, as the gas dissociation effect becomes more and more obvious, chemical energy will be difficult to convert into effective work, and it is very likely that we will repeat their mistakes..."

"..."

Apart from Chang Haonan himself, Jiang Zonglin and Chen Hong were the ones who conducted the most in-depth research on high-temperature gas dynamics and were also the first to react.

"As long as we pass this stage, the inlet shock wave will penetrate the entire isolation section/combustion chamber, causing the fluid in the combustion chamber to reach supersonic speed and completely enter the scramjet mode..."

"That's it."

Chang Haonan nodded:

"However, there are still some other details to be resolved... such as reducing the influence of the geometric double-throat structure on the pressure distribution of the super-ramjet mode, and how to transition from the diffuser oblique shock wave to the vehicle forebody oblique shock wave. These are the issues we should focus on first at this stage, and at the same time will not delay the development progress of the boost-glide configuration."

"Can the scramjet work at a Mach number below 5.0?"

Concerns were soon raised.

"Well... the definition of Mach 5.0 as the threshold of hypersonic speed is artificial. In fact, this number is related to many variables. As long as the characteristic Mach number of the organization is greater than 1 and the pressure at the starting position of heating in the working cycle is less than the given shock wave exit pressure, the normal operation of the hypersonic ramjet mode can be ensured."

Chang Haonan explained:

"Of course, this requires calculating the thermal working process of the combustion chamber under the condition of the maximum back pressure at the outlet area of ​​the isolation section and the corresponding performance, required expansion ratio, characteristic Mach number and heat release distribution law before designing, and..."

"..."

“In short, these are all jobs that require a lot of wind tunnel testing.”

He tapped the table lightly and began to summarize:

"The road ahead is long and arduous, comrades..."

……

After briefly arranging the follow-up testing work, Chang Haonan quickly sorted out the test and analysis results of the X51A, and then quickly drove to the Air Force Headquarters.

"Why so many?"

It has only been about a month since the Long March 9 returned. When Zheng Liangqun received the call just now, he thought that Chang Haonan had only told him some preliminary judgments verbally and had not even changed today's schedule.

After opening the file bag, I found a thick stack of conclusion reports inside. I was dumbfounded:

"I remember you said before that it might not be possible to get a particularly rich conclusion?"

At a certain moment, he felt that there seemed to be something wrong with his understanding of the word "rich".

"It was mainly due to good luck. The degree of restoration of the compressed isolation section was very high, and some useful conclusions were also drawn from the analysis..."

Chang Haonan replied without changing his expression.

Zheng Liangqun sat up straight and showed awe.gif.

"You wait first..."

Then he picked up the phone and quickly called a lieutenant:

"Ask Deputy Chief of Staff Lu to attend the meeting tonight on my behalf. Say there's an emergency here and I can't get away for the time being."

Such a decisive decision made Chang Haonan a little nervous:

"This...is not good."

After the young officer left, he turned his head to look at the door and said:

"The report is with you anyway. It's not like you'll be able to run away..."

Zheng Liangqun waved his hand:

"It's just a seminar to contact local units. The political department plays the leading role, and the other departments are just showing up. It would be the same if the deputy leaders were to go..."

Then he turned his attention back to the report in his hand.

Because it was written for his superiors, Chang Haonan not only retained the data analysis, but also wrote a section after each part using the most concise sentences possible.

Zheng Liangqun naturally had no difficulty reading it.

"That is to say..."

About half an hour later, he finally raised his head again:

"Do you think that the current problem of the Americans is not just the immaturity of individual technologies or some flaws in details, but that there is a problem at the route level?"

Chang Haonan had already found some tea leaves from Zheng Liangqun's office and made himself a cup:

"It's got to be more fundamental."

He put down the teacup in his hand and replied:

"Based on the current situation, I think not only the X51A, but even if they try to develop a gliding hypersonic weapon, they will encounter big problems..."

Zheng Liangqun's face showed surprise for a moment, but he quickly restrained his expression:

"Is it possible to solve this problem by using flying instead of testing?"

"It's hard."

Chang Haonan shook his head:

"The premise of using flight testing instead of testing is that the cause of the fault is single and the location of the problem can be determined. But if it was simply a mistake in model selection, they should have realized it during the ground testing phase and would not have allowed the aircraft to take off with such a big problem. So there must be a big loophole in the engineering management phase... Taken together, I guess they can't even do a root cause analysis."

"In fact, I can't even figure out how they succeeded with the X43A back then..."