Chapter 116 A New Starting Point for the Independent Aviation Industry (Two-in-One)

Because there was very little preparation time and there was still a lot of data to obtain, Chang Haonan had not conducted any rehearsals before.

Fortunately, the entire assessment method was basically completed by himself. Although the aviation industry standards involved have not yet been written out, they have been deeply rooted in Chang Haonan's mind.

So I came prepared.

"Dear experts, I will give a detailed description and explanation of the contents of the "Aviation Turbojet and Turbofan Engine Inlet Total Pressure Distortion Assessment Guide".

Chang Haonan stood next to the projector screen, looked at the ten expert panel members in front of him, took a deep breath, and officially began his introduction.

The first part is of course the definition.

Although the people who can sit here are all experts in the field of aviation power, this link is still indispensable.

Because what he is introducing is a "standard".

And it is a groundbreaking standard.

It’s like books sharing the same text and cars running on the same track.

Before that, 10,000 people can have 10,000 interpretations of a certain concept in their minds, but after that, it must be unified.

Standardization is the cornerstone of science and the romance of science.

"The aerodynamic stability of an aeroengine refers to the ability to maintain the engine's working state relative to disturbances based on aerodynamics, regardless of factors such as engine structural strength..."

“Because the highest pressure ratio point and highest efficiency point of the high-performance compression component are very close to the stability boundary; and in order to ensure its stable operation, the surge margin is set so that the boosting capacity that the compression component can provide is not fully utilized. To some extent, it is equivalent to wasting the design potential of the engine..."

"For compression components, the characteristic diagram shown in Figure 1.3 is divided into a stable operating area and an unstable operating area, and the dividing line can be defined as the surge boundary..."

"There are many types of destabilization factors that affect the aerodynamic stability of the engine, and their effects on the engine are also different. Some destabilization factors increase the common working line of the compression components, and some destabilization factors move the stability boundary of the compression components downward... …”

Chang Haonan projected a characteristic diagram of compression components onto the screen and introduced it carefully with a long pointer in his hand, while the ten experts below were also busy writing and carefully recording the content they were interested in.

“To this end, I analyzed and counted a large number of engine instability failures that have occurred in the past, and summarized 16 types of stability degradation factors in the evaluation specifications, including pressure distortion, temperature distortion, shock wave, wind gust, Reynolds number change, switch-on/ Disconnect the afterburning force and unsteady heat transfer..."

“Considering that there are many types of destabilization factors, I divided them into four major categories according to the mechanism that affects the engine surge margin, and established mathematical models of their impact on engine aerodynamic stability: steady-state destabilization factors, dynamic process Class destabilization factor, intake distortion class destabilization factor, statistical class destabilization factor.”

"For the first three types of destabilization factors, numerical calculation methods are used for quantitative analysis and evaluation; for the fourth type of destabilization factors, statistical normative values ​​will mainly be used to evaluate them. Below I will focus on the third type, which is the air intake Detailed engineering methods are given for the evaluation of distortion-type destabilization factors..."

If Chang Haonan had just been reborn, it would be quite difficult to explain even just one part of such a rather complicated set of standards.

However, in the past few months, especially since joining the 83 Project, his past shortcomings in engineering experience have been strengthened, so he can easily explain some slightly obscure content with calculation examples or illustrations.

Moreover, Chang Haonan now has a unique advantage.

It was he who really participated in the turbojet 14 project.

China's first engine model that has completely gone through the entire testing process.

Even though I didn’t participate from scratch, it was enough.

After communicating with Du Yishan on the phone yesterday, Chang Haonan began to consider restructuring the standard system of the entire aviation industry.

As a reborn person who has experienced the second decade of the 21st century, only he knows how great it is for engineers to have a completely independent set of technical standards.

Many development processes can be completed using encapsulated standard models as easily as building blocks.

By analogy, it's like writing programs in assembly language or even machine language in the past, but now you can suddenly use high-level languages ​​directly.

Therefore, when introducing the idea of ​​​​numerical simulation, he specially drew a pie for the members of the expert group present:

"It should be noted that this evaluation guide is not only an operating manual for aerodynamic stability testing, but also a part of the aerodynamic stability analysis system of aeroengines."

"When our standards in the field of aerodynamics are complete and accurate enough, we can establish a simulation system suitable for multiple types of engines to evaluate the impact of various destabilization factors on engine aerodynamic stability, allowing users to choose packaged The standard model is assembled into the target engine for simulation, thereby guiding the design process of the inlet matching the engine..."

When Chang Haonan talked about this, several experts on the opposite side had already shown mesmerized expressions.

Of course they know that this is something that has not yet been revealed.

But this cake is so delicious.

China's aero-engine project has long been used as a supporting aircraft project and lacks technical continuity. Therefore, the pre-research and design process of each new model is like going through a disaster, requiring a lot of repetitive work, wasting a lot of time and In terms of funding, the results are often not good.

The experts sitting here have all experienced this helplessness, so they hope that the idea proposed by Chang Haonan can come true.

You know, modular numerical simulation and simulation of engines is something that developed countries, including the United Kingdom and the United States, have never thought of.

In this era when most people want to follow the footsteps of the United States or Europe, it is not easy to have such an "out of the ordinary" idea.

Some people have even begun to imagine what impact this simulation system will have.

The explanation gradually came to an end.

"...If the local surge margin ΔSM1 is required to satisfy √[max (ΔSMP^2, ΔSMA^2) + ΔSMW^2] + ΔSMT + ΔSMW> ΔSM1, then the local surge margin needs to be used to compensate for temperature distortion. The calculation method is..."

“After obtaining the local required stability margin of each destabilizing factor, the local required stability margin of the non-random factors is considered by the algebraic sum method, and the local required stability margin of the random factor is considered by the sum square root, so that Obtain the total required stability margin."

"Among the several typical operating conditions considered, the one with the smallest remaining stability margin is the weak link in the engine's aerodynamic stability design, and is also the object that needs to be optimized during the engineering design stage."

Having said this, he directly released a diagram of the total required stability margin of the Turbojet 14.

It clearly states that when flying at high altitudes and afterburner on and off conditions change, this is the weakest link in the stability of this engine.

It is consistent with the data obtained during the test flight.

Chang Haonan turned around and bowed slightly to the members of the expert team.

"My introduction on the aerodynamic stability testing and evaluation methods of aeroengines is over. I have done a little bit of work. Thank you all."

There was a brief silence.

After about a few seconds, the first round of applause from someone unknown rang out.

Then, the entire conference room was instantly filled with applause.

Although the members who entered the expert group were all those who expressed their support for setting new standards at yesterday's Science and Industry Committee symposium, no one expected that Chang Haonan's work had been completed to such a high degree.

At this point, everyone knows that the first standard that belongs entirely to China Aviation Industry is about to appear.

Of course, the routine question-and-answer session is still indispensable.

But the atmosphere is completely different from ordinary review meetings.

Under normal circumstances, the nature of the review team's questions is more similar to "questioning", which requires the people on the stage to explain, explain or correct things that were not explained clearly before, or there were omissions or even mistakes.

It's a bit like a graduation defense, but much more serious in nature.

After all, national standards cover a wide range of areas and have great influence, and there is no room for sloppiness.

Therefore, sometimes, this questioning process even lasts for more than a day - because problems may be discovered and need to be corrected off-site.

Therefore, it is not uncommon for the review meeting to last for ten days and a half.

However, in Chang Haonan's case, because the introduction he just gave was extremely complete, and he also had the experience of a real project such as the Turbojet 14, the style of the question-and-answer session this time was more like...asking for advice.

After all, too many new concepts, theories, and engineering methods were introduced at once.

"Comrade Chang Haonan, in the assessment guide document you provided, it was mentioned that a plug-in plate distortion simulation device is installed at the compressor inlet. Why should this plug-in plate be set as a single crescent plate?"

The first person to ask a question was a middle-aged engineer who didn't look too old. Judging from the name tag on the table, his name was Lin Yuang.

At yesterday's meeting, it was he who was the first to propose that a new standard should be established based on the assessment guide, rather than making minor improvements based on the old 1994 standard.

It is precisely for this reason that Lin Yuang pays great attention to every detail that Chang Haonan talks about.

As the initiator, he must ensure that nothing goes wrong.

Many people who are engineers are more interested in such issues involving principles.

However, Chang Haonan's theoretical foundation was relatively solid, and he had collected a lot of data in the past few days, so he walked steadily to the blackboard next to him without any panic, picked up the chalk and drew four simple diagrams, and at the same time explained:

"In the test of Turbojet 14, we tried four different plug-in distortion simulation devices, including a single-piece crescent shape, two-piece crescent shape, a circular ring shape and a sector shape."

"According to the results obtained, the four design schemes are relatively close in their ability to generate distorted flow fields, but Scheme 1, which is a single crescent plate, involves the fewest independent variables and only has one baffle height H. For the early stage, Numerical simulation and optimization work for stability during the engineering design phase is more beneficial.”

“For example, when we were modifying the compressor of the turbojet 14, we specifically considered optimizing the surge margin...”

Then another person asked:

"In the test operation method in the guide, you mentioned that it is necessary to use a plug-in distortion simulation device to gradually increase the distortion intensity until the engine enters an unstable operating state, in order to obtain the stability margin and

Coefficient of distortion sensitivity, does this mean that an engine must be destroyed every time a stability assessment is performed? "

"This depends on the condition of the engine itself. Theoretically, for a well-designed aeroengine, the distortion index can be adjusted to bring it into a rotating stall state that will not cause permanent damage to the structure, but this requires a lot of experiments. and simulated data as support.”

Faced with this somewhat sharp question, Chang Haonan did not change his expression and still had a confident smile on his face:

"This is what we hope to do in the future, which is to use the flow data at the compressor inlet to determine the condition of the engine during the flight of the aircraft. When there are signs of surge, we can remind the pilot or even actively adjust flight attitude to avoid more serious instability failures."

"Moreover, stability evaluation is part of the extreme capability test, just like the static test of the aircraft and the full life test of the engine, so damage to the test object is originally planned."

The questioner nodded, obviously agreeing with this explanation.

During the flight tests of most models, prototype No. 02 will not be seen, because generally No. 02 will be a static test machine, and the last part of the static test of the whole machine is to Aircraft destruction as termination condition.

Although it sounds a bit sad, it is essential.

Chang Haonan answered several questions in a row that followed.

Finally, after more than four hours of marathon review, Liu Zhenxiang, the leader of the expert group, wrote "Agree" on the submission and signed his name.

Subsequently, the other nine people also signed respectively, which was regarded as the official approval of the evaluation method at the level of the Commission of Science, Technology and Industry for National Defense.

After going through some subsequent approval processes, it will be officially "regularized" and become a standard.

According to the numbering convention, it will be named GJB/Z64A-96.

It's a name worth remembering.

Although inconspicuous, it is the starting point for China's aviation industry to get rid of external dependence and truly move towards independence.

…

After the review work is completed, the expert team will not leave Fucheng immediately, because one of their first-phase tasks is to track the testing of the Turbojet 14.

It can be regarded as an intuitive understanding of this set of assessment methods.

When Chang Haonan led ten members of the expert team into the control room of the high-altitude test bench, Yao Mengna's expression became a little stiff.

Even if he is a student of Academician Du Yishan, not everyone can face the expert group sent by the Commission of Science, Technology and Industry for National Defense without changing his face or heart like Chang Haonan.

This battle was just right for an undergraduate student.

But it’s a bit too big for a PhD student.

What's more, she always felt that she was just helping Chang Haonan, and she was not very confident in on-site command.

"Otherwise...you will still be in charge this time?"

While several members of the expert team were pulling Liu Zhenxiang to ask questions, Yao Mengna approached Chang Haonan who was gulping down water.

"It's okay, don't be nervous, just follow the steps."

Chang Haonan's voice was already hoarse. The review meeting that lasted from afternoon to evening almost exhausted all his energy:

"The conductor of the test in the past few days has always been Yin. Now that he is replaced on the spot, he needs to start running in again. It is not appropriate."

Seeing the rare nervous expression on the senior sister's face, Chang Haonan patted her shoulder to encourage her.

As a result, the other party seemed to become more nervous...

I forgot to set it up and posted it last night... I will update it at night as usual.