In the process of learning from later test pilots, the design flaws of the J-7II engine were included in the test flight lesson plan as a typical case, and Yang Weining was naturally clear about the ins and outs of this problem. Pen × fun × Pavilion www. ｂｉｑｕｇｅ。 ｉｎｆｏ

The J-7II fighter uses a turbojet-7B engine, which is an axial twin-rotor turbojet engine with afterburner, which is composed of four major components: twin-rotor axial flow compressor, ring tube combustion chamber, twin-rotor gas turbine, afterburner and adjustable tail nozzle, in addition to the fuel system, starting system, cooling system, anti-icing system and other main systems, as well as the transmission device that drives the engine and aircraft accessories.

The twin-rotor structure can ensure that the engine works reliably at a high altitude and in the maximum flight speed range, and avoids the engine surge.

The afterburner can make the engine burn again under the conditions of maximum speed and the maximum temperature before the turbine, further increase the gas temperature and increase the gas expansion acceleration energy, thereby improving the jet speed, and can greatly increase the thrust of the engine in a short time.

However, due to the design and the mounting edge material of the afterburner, the cooling system of the turbojet-7 has a major flaw.

Under general flight training conditions, this defect will not cause engine failure, but once it enters the combat state, the aircraft frequently turns on the afterburner and flies at supersonic speed, which may lead to the high temperature of the afterburner chamber wall, igniting the aluminum alloy fuselage of the aircraft, causing major flight accidents.

At the beginning, Yang Weining did not think of this technical flaw of the J-7II, and it was not until Xiao Liu mentioned that the temperature of the fuselage increased after the test flight, and Yang Weining remembered this problem.

Yang Weining pondered for a moment and asked, "Butcher, is the combustion chamber flame cylinder of the Turbojet-7B GH30 or GH15 used?"

“GH-15。 ”

Yang Weining said: "I remember that the prototype of the turbojet-7 has a pre-turbine temperature of 915 °C, and the J-7II uses a turbojet-7B, and the pre-turbo temperature is 1015 °C, which is 100 higher, right?"

Tu Kai was slightly stunned, his understanding of Yang Weining was only limited to a computer genius, when Yang Weining stopped Xiao Liu to look at the data just now, he just asked casually, he didn't expect him to have such a professional insight into the engine.

GH series alloy is the abbreviation of China's high-performance iron-nickel-based high-temperature resistant alloy, which greatly improves the thermal strength while maintaining high plasticity and excellent oxidation resistance, and also has good process performance such as stamping, welding and hot working.

He nodded and said: "That's right, we used GH30 alloy below 800°C as the material of the flame cylinder, but after 50 hours of test run, we found that cracks occurred at the upper arc adapter on both sides of the flame cylinder installation edge. Since the heating and cooling fatigue and vibration loads on the installation side of the flame cylinder of the retrofit machine are much worse than those of the prototype, it is no longer suitable to continue to use GH30 alloy, so we chose GH15 with higher heat resistance. ”

Yang Weining continued to ask, "What about the combustion chamber shell?"

Tu Kai pondered for a moment and frowned: "If I remember correctly, both engines should be 1Cr18Ni9Ti." ”

1Cr18Ni9Ti is ordinary stainless steel.

Yang Weining said with a smile: "This is the problem, butcher, think about it, the temperature before the vortex of the combustion chamber rises by 100 degrees, and the installation edge as an important heat sink is still made of ordinary stainless steel. It just so happened that Comrade Yu Hongfei was carrying out a supersonic test flight project today, and it is entirely possible for the body temperature to rise by more than ten degrees after turning on afterburner. ”

Tu Kai couldn't help but be stunned, he didn't expect the problem to appear here.

What shocked him even more was that Yang Weining's understanding of the turbojet-7 engine, I am afraid that the chief designer of this engine came, and there was no way to find out the source of the problem in just ten minutes.

For a while, there was a buzz at the scene.

Listening to his analysis, it is really possible that this is the reason. ”

"This comrade looks young, but he has a deep theoretical and practical foundation. ”

"I don't know where this kid comes from, but his tone is really big enough. ”

Xiao Liu on the side suddenly breathed a sigh of relief and said with a smile: "So that's the case, I thought it was a problem, the temperature of the body increased by more than ten degrees, and the impact on the body was not great, this is not a big problem." ”

Everyone present nodded in agreement, and even Tu Kai bowed slightly.

Indeed, when the plane flies at high speed in the air, the temperature of the body caused by friction is already high, but it rises by more than ten degrees, and the aircraft can fully withstand it.

Yang Weining couldn't help but be a little disappointed, the aviation people of this era are still too immature, whether it is experience or ability, there are too many things to learn. This is also understandable, in fact, no matter which country, many times, the aviation industry is gradually progressing under the lessons of blood and fire.

Yang Weining shook his head and said, "Is there no problem? ”

Tu Kai was slightly stunned, and said suspiciously: "Xiao Yang, is there anything wrong with this?"

Yang Weining said: "Tu Gong, do you think we are designing a fighter plane, or are we designing an ordinary civilian aircraft?"

"Fighter jets, of course!"

Xiao Liu on the side shouted.

Yang Weining said solemnly: "That's it, this is a fighter plane, once a war breaks out, in the state of fighting with the enemy, can it be that our afterburner is only turned on once? Today, only one afterburner flight is turned on, and the temperature of the airframe has risen by more than ten degrees, if the afterburner flight is turned on frequently, how much will the temperature of the airplane rise? If serious consequences are caused by this problem, who will bear the responsibility? Who should guarantee the life of the pilot?"

In the end, Yang Weining's expression became more and more serious, and his tone became more and more stern, and for a while, everyone present was stunned.

Although I don't know what the origin of this young man is, Tu Kai, as the chief engineer of the Rongcheng Aircraft Factory, has no affection at all, which is too bullish.

The scene fell into a strange silence, and after a long time, Tu Kai clapped his hands lightly, sighed and said: "Today, Xiao Yang gave me and all of us a vivid lesson, our production workshop is more responsible than Mount Tai, but how many people really remember this in their minds." This problem is actually not difficult to think of, but including me, most of us have ignored this problem, if it is not for Xiao Yang to mention it, it is very likely that there will be an accident in the future, which can give us a profound lesson. Let's give Xiao Yang a round of applause. ”

The scene immediately burst into warm applause.