Chapter 116 A new starting point for the independent aviation industry (2 in 1) (page 12)
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.
“……如果局部需用喘振裕度ΔSM1满足√[max（ΔSMP^2，ΔSMA^2）+ΔSMW^2]+ΔSMT+ΔSMW>ΔSM1，则补偿温度畸变的局部需用喘振裕度的计算方式为……”
“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 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."
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.
