The Military-industrial Scientific Research System of the Academic Master Chapter 116

Chapter 116: A new starting point for the independent aviation industry (two-in-one)

 Because the preparation time is very short and there is still a lot of data to be obtained, Chang Haonan has 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.

“Experts, I will give a detailed description and explanation of the contents of the “Guidelines for the Assessment of Inlet Total Pressure Distortion of Aviation Turbojet and Turbofan Engines”.”

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 started his introduction.

 The first part is naturally the definition.

ˆAlthough the people sitting here are all experts in the field of aviation power, this link is still essential.

 Because what he is introducing is a "standard".

  And it is the standard that created the world.

 Just like books running on the same text or cars running on the same track.

 Before this, 10,000 people can have 10,000 interpretations of a certain concept in their minds, but after that, they 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 working state of the engine 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 it were Chang Haonan who had just been reborn, it would still be quite difficult to explain even a part of such a rather complicated set of standards.

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

 Furthermore, Chang Haonan currently has a unique advantage.

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

 The first engine model in China that has gone through all testing processes.

 Although I didn't participate from the beginning, 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 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 operation 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 other side had already expressed enchanted expressions.

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

 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 must know that 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 the impact this simulation system will have.

 The explanation is gradually coming 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 calculation is required to compensate for temperature distortion The 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 Get 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.”

 Speaking of 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 or when the afterburner on/off conditions change, this 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 team.

“This is the end of my introduction on the aerodynamic stability testing and evaluation methods of aeroengines. I have done a little bit of work. Thank you all.”

 There was a brief silence.

 About a few seconds later, the first round of applause from someone unknown rang out. Subsequently, 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 Technology 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.

 It's just that the atmosphere is completely different from ordinary review meetings.

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

 Somewhat similar to 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 may even last more than a day—because problems may be discovered and need to be corrected off-site.

 So 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 have been introduced at once.

“Comrade Chang Haonan, in the evaluation 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 with an engineering background are more troubled by issues involving principles.

However, Chang Haonan's theoretical foundation is relatively solid, and he has 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 single-piece crescent shape, two-piece crescent shape, circular ring shape and 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, during our renovation of the turbojet 14 compressor, we specifically considered optimizing the surge margin…”

 Following this, 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.”

Facing this slightly 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.”

“Furthermore, 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 may sound a pity, it is essential.

 Chang Haonan answered several questions in a row that followed fluently.

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

 Subsequently, nine other people also signed, 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/Z6496.

 This is a name worth remembering.

Although it is 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-stage tasks is to track the testing of the turbojet 14.

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

When Chang Haonan led ten members of the expert team into the control room of the high-altitude test platform, Yao Mengna's expression, which was originally calm, 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 expression or heartbeat like Chang Haonan.

This battle is 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 taking a big gulp of 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 You. Now if I change the person on the spot, I need to start the running-in all over again, which is inappropriate.”

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 posted it last night when I forgot to set it...I will update it in the evening as usual

 (End of this chapter)

Chapter end