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.
“Dear experts, let me 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 began his introduction.
The first part is naturally the definition.
Although those who can sit here are experts in the field of aviation power, this link is still essential.
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 this, 10,000 people could 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 the strength of the engine structure...”
“Due to The highest pressure ratio point and highest efficiency point of high-performance compression components are very close to the stability boundary; in order to ensure its stable operation, the surge margin is set so that the boosting capacity provided by the compression components is not fully utilized, and in a certain situation To a certain extent, it is equivalent to wasting the design potential of the engine..."
"For the compression component, it is divided into a stable operating area and an unstable operating area on the characteristic diagram shown in Figure 1.3, and the dividing line can be defined as the surge boundary..."
"Influence on the aerodynamic stability of the engine There are many types of destabilizing factors, and their effects on the engine are also different. Some destabilizing factors increase the common working line of the compression components, and some destabilizing 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 what they were interested in. content.
“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, namely pressure distortion, temperature distortion, shock wave, gust, Renault Number changes, turning on/off afterburner, unsteady heat transfer..."
"Considering the wide variety of destabilization factors, I divided them into four major categories based on the mechanism that affects the engine surge margin. Classes are established to establish mathematical models of their effects on engine aerodynamic stability: steady-state destabilization factors, dynamic process destabilization factors, intake distortion destabilization factors, and statistical destabilization factors. ”
"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 destabilization factors..."
If Chang Haonan, who had just been reborn, wanted to explain such a rather complicated set of standards, even just a part of the standards It is still quite difficult to understand.
But in the past few months, especially since joining the 83 Project, his past shortcomings in engineering experience have been strengthened, so for some slightly obscure content, he can also use calculation examples or Explain by means of 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.
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 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 about aerodynamic stability. The test operation manual is also a part of the aerodynamic stability analysis system of aerospace engines. ”
“When our standards in the field of aerodynamics are complete and accurate enough, we can establish a set of standards applicable to many types of aerodynamics. The engine and the simulation system used to evaluate the impact of various destabilization factors on the aerodynamic stability of the engine allow users to select packaged standard models to assemble into a target engine for simulation, thereby guiding the design process of the inlet matching the engine..."
When Chang Haonan was talking about this, several experts on the other 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. A lot of time and money are wasted, and 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 what kind of impact this simulation system will have.
The explanation is gradually coming to an end.
“...If the local required surge margin ΔSM1 satisfies √[max(ΔSMP^2, ΔSMA^2)+ΔSMW^2]+ΔSMT+ΔSMW>ΔSM1, then the local need to compensate for temperature distortion The calculation method of surge margin is..."
"After obtaining the local required stability margin of each destabilization factor, the local required stability margin of the non-random factors is considered according to the algebraic sum method , the local required stability margin of the random factor is considered using the sum square, so as to obtain the total required stability margin. ”
"Among the several typical working 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 which , he directly released a picture 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.
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 short silence at the scene.
About a few seconds later, the first round of applause from someone unknown sounded. 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 the establishment of new standards at yesterday’s symposium of the Science and Technology Commission, no one thought that Chang Haonan’s work The level of completion is already so high.
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 judging 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, explain 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 even lasts for 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?"
< br>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 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 explained at the same time:
“In the test of Turbojet 14, we tried four different plug-in plate distortion simulation devices, including a single-piece crescent shape, two-piece crescent shape, and a circular ring shape. and fan-shaped. "
"According to the obtained results, the ability of the four design schemes to generate distorted flow fields is relatively close, but Scheme 1, that is, the single crescent plate involves the least independent variables. There is only one baffle height H, which is more beneficial for numerical simulation and optimization work on stability in the early engineering design stage.”
“For example, in our process of transforming the turbojet 14 compressor. , specifically considering the optimization of surge margin..."
Then another person asked:
“In the test operation method in the guide, you mentioned that you need 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 coefficient of stability margin and
distortion sensitivity, does this mean that an engine must be destroyed every time a stability evaluation is performed? ”
“It depends on the engine itself? In theory, for a well-designed aeroengine, the distortion index can be adjusted to bring it into a rotational stall state that will not cause permanent damage to the structure. However, this requires a large amount of test and simulation data to support it. ”
Facing this slightly sharp question, Chang Haonan did not change his expression, still smiling confidently:
"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 ultimate capability test, just like the static test of the aircraft and the full life test of the engine. Therefore, causing damage to the test subject was 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 static test of the whole machine The last part is to destroy the aircraft as a 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 "agreed to pass" on the opinion letter and signed his own name.
Subsequently, the other nine 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 officially 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 toward independence.
......
After the review work is over, the expert team will not leave Fucheng immediately, because one of their first phase tasks is to follow the test of the Turbojet 14 Condition.
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 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 expression or heartbeat like Chang Haonan.
This battle is just right for an undergraduate student.
But it is 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'll be in charge this time?"
While several members of the expert team were asking 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 You. Now that I have to change someone on the spot, I need to start the running-in 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 seems to have become more nervous...
Last night I forgot to set it and posted it... The update was added at night as usual
(End of this chapter)