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

Fortunately, the entire evaluation method was basically completed by himself, and although the aviation industry standards involved behind it have not yet been written, they have been deeply rooted in Chang Haonan's mind.

So I came prepared.

"Experts, I will give a detailed explanation and explanation of the content of the "Guidelines for the Evaluation of Imported Total Pressure Distortion of Aviation Turbojet and Turbofan Engines".

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

The first part, of course, is the definition.

Despite the fact that all the people here are experts in the field of aerodynamics, this link is still essential.

Because what he's introducing is a "standard".

And it's groundbreaking.

It's like a book with the same text and a car with the same track.

Before that, there could be 10,000 explanations of a concept in the minds of 10,000 people, but after that, they had to be unified.

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

"The aerodynamic stability of an aero engine refers to the ability of the engine to maintain its working state relative to interference from the perspective of gas dynamics, regardless of factors such as the structural strength of the engine......"

"Due to the fact that the highest pressure ratio point and the highest efficiency point of the high-performance compression component are very close to the stability boundary; In order to ensure its stable operation, the surge margin is set so that the booster capacity that can be provided by the compression parts is not fully utilized, which is equivalent to wasting the design potential of the engine to some extent......"

"For compressed parts, which are divided into stable and unstable working areas on the characteristic diagram shown in Figure 1.3, the dividing line can be defined as the surge boundary ......"

"There are many different types of destabilization factors that affect the aerodynamic stability of an engine, and the impact on the engine is also different. Some of the stability reduction factors increase the common working line of the compression parts, and some of the stability reduction factors move the stability boundary of the compression parts downward......"

Chang Haonan projected a characteristic map of compressed parts onto the screen, holding a long whip in his hand and carefully introducing it, while the ten experts below were also working hard to write and carefully record the content they were interested in.

"To this end, I analyzed and counted a large number of engine instability failures that occurred in the past, and summarized 16 types of destabilization factors in the evaluation specification, namely pressure distortion, temperature distortion, shock wave, gust of wind, Reynolds number change, on/off afterburner, unsteady heat transfer ......"

"Considering that there are many types of stability reduction factors, I divide them into four categories according to the mechanism that affects the surge margin of the engine, and establish a mathematical model of their impact on the aerodynamic stability of the engine: steady-state stabilization factors, dynamic process stability degradation factors, intake distortion stability reduction factors, and statistical stability reduction factors."

"For the first three types of stability reduction factors, numerical calculation methods are used for quantitative analysis and evaluation; For the fourth type of stability reduction factor, the statistical standard value will be mainly used to evaluate, and I will focus on the evaluation of the third type, that is, the intake distortion type of stability reduction factor, and give a detailed engineering method below......"

If it is Chang Haonan, who has just been reborn, it is still quite difficult to explain such a set of rather complex standards, even if it is only a part of the standards.

However, in the past few months, especially since joining the 83 Project, his shortcomings in engineering experience in the past have been strengthened, so he can easily explain some slightly obscure content in the form of calculations or legends.

Moreover, Chang Haonan has a unique advantage at the moment.

It was he who was really involved in the Turbojet 14 project.

Huaxia is the first engine model to have gone through the entire test process in its entirety.

Although I didn't start from scratch, it was enough.

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

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

Many of the development processes can be done using encapsulated standard models, which can be done as easily as building blocks.

By analogy, it is as if you used to have to write programs in assembly language or even machine language, but now you can suddenly write programs directly in high-level language.

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

"It is important to note that this rating guide is not only an operating manual for conducting aerodynamic stability tests, but also a part of the aerodynamic stability analysis system for aero engines."

"When our standards in the field of aerodynamics are complete and accurate enough, we can establish a simulation system suitable for various types of engines to evaluate the influence of various destabilization factors on the aerodynamic stability of the engine, allowing users to select a packaged standard model to assemble the target engine for simulation, so as to guide the design process of the inlet path supporting the engine......"

When Chang Haonan said this, there were already several experts on the other side with fascinated expressions.

Of course, they knew that this was a matter of eight words.

But this cake is so fragrant.

Due to the long-term supporting of the aircraft project, Huaxia's aero engine project lacks technical continuity, so the pre-research and design process of each new model seems to be in a catastrophe, requiring a lot of repetitive work, wasting a lot of time and money, and often the effect is 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 must know that the modular numerical simulation and simulation of the engine is something that developed countries, including the United Kingdom and the United States, have not thought of.

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

Some people are even beginning to imagine what the impact of the simulation system will be.

The lecture is gradually coming to an end.

“…… If the local surge margin ΔSM1 satisfies the √[max(ΔSMP^2,ΔSMA^2)+ΔSMW^2]+ΔSMT+ΔSMW>ΔSM1, the local surge margin to compensate for temperature distortion is calculated as ......"

"After obtaining the local demand stability margin of each stability reduction factor, the local need of non-random factors is considered by algebraic sum, and the local need of random factors is considered by the stability margin and square root, so as to obtain the total demand stability margin."

"Among the typical working conditions considered, the one with the smallest residual stability margin is the weak link in the aerodynamic stability design of the engine, and it is also the object that needs to be optimized in the engineering design stage."

Speaking of which, he directly released a diagram of the total required stability margin composition of the vortex jet 14.

It is clearly stated that when the situation of high-altitude flight and afterburner on/off changes, it is the weakest link in the stability of this engine.

Consistent with the data obtained during the test flight.

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

"I have done a little bit of work at the end of my introduction on aerodynamic stability testing and evaluation methods for aero engines, thank you"

There was a brief silence at the scene.

After about a few seconds, the first applause rang out for no one who it belonged to.

Then, the entire conference room was filled with applause in an instant.

Although the members of the expert group were all people who expressed their approval of the establishment of new standards at yesterday's symposium of the Science and Technology Commission, no one thought that Chang Haonan's work had been completed so high.

At this point, everyone knows very well that the first standard, which belongs entirely to Huaxia Aviation Industry, is about to appear.

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

It's just that the atmosphere is completely different from the average judging session.

Under normal circumstances, the nature of the questions asked by the judging team is more similar to "questioning", which is to ask the people on the stage to explain, explain or correct the things that have not been explained clearly, or there are omissions or even mistakes.

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

After all, the national standard covers a wide range and has great influence, and there is no room for sloppiness.

As a result, in some cases, the questioning process can even take more than a day – because there may be a problem that needs to be corrected on the spot.

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

However, here in Chang Haonan, because his introduction just now is extremely complete, and there is a real project of Turbojet 14 as experience, the style of the question session this time is more like ...... Ask.

After all, there are too many new concepts, theories, and engineering methods that have been introduced at once.

"Comrade Chang Haonan, as mentioned in the assessment guide document you provided, by setting up a plug-in distortion simulation device at the inlet of the compressor, why should this plug-in plate be set up as a single crescent-shaped plate?"

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

At yesterday's meeting, he was the first to propose that a new standard should be established based on the assessment guidelines, rather than a minor repair on the basis of the old 1994 standard.

It is precisely because of this that Lin Yuang is very attentive to every detail that Chang Haonan said.

As the initiator, he had to make sure that nothing went wrong.

Many engineers will compare principles such as pestles.

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

"In the vortex 14 test, we tried four different plug-in distortion simulators, including a single crescent, a double crescent, a ring and a fan."

"According to the obtained results, the ability of the four design schemes to generate distorted flow fields is relatively similar, but scheme 1, that is, a single crescent slab, involves the least independent variables, and only one baffle height H, which is more beneficial for numerical simulation and optimization of stability in the early engineering design stage."

"For example, in the process of retrofitting the turbojet 14 compressor, we specifically considered the optimization of the surge margin......"

This was followed by another question:

"In the test operation method in the guide, you mentioned that you need to gradually increase the distortion strength by using a plug-in distortion simulation device until the engine enters an unstable working state, and then the stability margin can be obtained

Does this mean that an engine must be destroyed for every stability assessment? ”

"It depends on the engine itself, and theoretically, for a well-designed aero engine, the distortion index can be adjusted to a rotational stall state that does not cause permanent damage to the structure, but this requires a lot of experimental and simulation data."

In the face of this slightly sharp question, Chang Haonan did not change his color, and still had a confident smile:

"This is also what we hope to do in the future, that is, during the flight of the aircraft, through the flow data of the compressor inlet to judge the situation of the engine, when there are signs of surge, to remind the pilot, and even to actively adjust the flight attitude to avoid more serious instability failures."

"Moreover, the stability assessment is part of the ultimate capability test, just like the static test of an aircraft and the lifetime test of the engine, so the damage to the test object is planned."

The questioner nodded, clearly agreeing with the explanation.

In the flight test process of most models, the prototype of No. 02 will not be seen, because under normal circumstances, No. 02 will be a static testing machine, and the last part of the static test of the whole aircraft is to destroy the aircraft as a termination condition.

As sad as it may sound, it's essential.

In the following series of several questions, Chang Haonan can be regarded as fluent in answers.

Finally, after more than four hours of marathon review, Liu Zhenxiang, as the leader of the expert group, wrote down the four big words "agree to pass" on the opinion letter and signed his name.

Subsequently, the other 9 people also signed separately, which can be regarded as officially recognizing 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 officially become a standard.

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

It's a name to remember.

Although it is inconspicuous, it is the starting point for Huaxia Aviation Industry to get rid of its dependence on foreign countries and truly move towards independence.

……

After the review is over, the expert group will not leave Fucheng immediately, because one of their first phase tasks is to track the test of Vortex 14.

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

When Chang Haonan entered the control room of the high-altitude test bench with ten members of the expert group, Yao Mengna's expression, which was originally calm, stiffened a little.

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 like Chang Haonan.

This battle turned out to be just right for an undergraduate.

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

What's more, she has always felt that she is just giving Chang Haonan a hand, and she is not very confident in the on-site command.

"Or else...... You're in command this time? ”

Taking advantage of the fact that several members of the expert group pulled Liu Zhenxiang to ask questions, Yao Mengna found Chang Haonan, who was pouring water.

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

Chang Haonan's voice was already a little hoarse, and the judging meeting that lasted from afternoon to evening almost exhausted all his physical strength:

"The conductor of the test in the past few days has always been Ling, and now he is replaced on the spot, but he needs to start running in again, which is not suitable."

Seeing that the senior sister showed a rare nervous expression, Chang Haonan patted her on the shoulder to show encouragement.

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

I forgot to release it when I set it last night...... Plus more as usual in the evening

(End of chapter)