The military-industrial scientific research system of the academic master

In fact, the reason why Chang Haonan was so anxious to come to the 410 Factory to check the engine production situation was that in addition to having an understanding of the domestic aviation power production level so that he could make some arrangements in advance, another very important reason was that he also remembered When I checked the test flight data of the No. 01 prototype before, I found that the working status of the two turbojet 14s on board was very unstable.

If this phenomenon occurs only on the faulty unit, it can be considered as a sign before surge.

However, the actual situation is that similar phenomena exist in both engines, including the two engines on the No. 03 prototype that Chang Haonan later visited specifically to check.

And the magnitude of instability is different.

This situation means that the problem most likely lies in the manufacturing process.

Although after increasing the surge margin of the turbojet 14 by a full 25%, he can ensure that state fluctuations of this magnitude will not induce surge again.

But it's not enough.

The surge margin is somewhat similar to the margin left in terms of performance. The surge boundary line is the theoretical limit, and the common operating line is the artificial performance boundary set to ensure safety.

The more stable the engine's working condition, the shorter the distance between the two curves, which means that more actual performance can be "squeezed out" while the theoretical limit remains unchanged.

After some previous improvements, the performance potential of the turbojet 14 is actually greater than before.

Therefore, if the unstable factor can be found and solved, the actual performance of this engine can be further improved.

But this matter is obviously not that easy.

When Chang Haonan left the production workshop, it was already late at night.

As a person who is not deeply immersed in the field of mechanical manufacturing, he really failed to find out which step caused the problem.

We can only wait until the testing phase or even the later small batch trial production phase to slowly explore the problem.

Fortunately, even if there are subsequent improvements in manufacturing, they are within the scope of production finalization, so they will not affect the current work.

…

One morning a few days later, a Y-8 transport plane painted in gray and white landed on the runway of Beiling Airport in Factory 112.

The turbojet 14 prototype numbered 010001 had already rolled off the production line from Factory 410 the night before and was shipped here overnight.

It almost pinned the hopes of the entire 606 Institute and the entire August 3rd Project.

In fact, when the engine was assembled and tested off the line, everyone had already discovered its differences from the original design——

The weight of the entire machine under the national military standard has been reduced from the original 1150kg to 1040kg.

The weight loss of 110 kilograms may not seem like much, but for an aero engine, every kilogram of weight is worthy of careful calculation.

Not to mention it was reduced by 10% in one go.

Even if other performance remains unchanged, the weight reduction alone is enough to bring the performance of the turbojet 14 to a new level.

What’s even more exaggerated is that the main optimization direction of this improvement is not weight loss.

This 110 kilograms can only be regarded as a gift.

Since the gifts are already so surprising, how can everyone not look forward to the performance of the engine itself?

Yang Fenghao, Yan Zhongcheng and Chang Haonan stood together and watched as the engine, which had invested thousands of people's efforts, was fixed on the pallet and then slowly entered the cabin of the Y-8.

In the northeastern morning in mid-September, there was already a hint of chill in the air.

Yang Fenghao was wearing a leather jacket, put his hands inside his sleeves, and asked Yan Zhongcheng next to him:

"The last time I sent this old guy to Fucheng, it was nearly eight years ago, right?"

"Yeah..." Yan Zhongcheng nodded, tightened the cotton clothes tightly around his body, and raised his head slightly, as if he was remembering something:

"At that time, the high-altitude platform of Institute 624 was still under construction. The air intake distortion test, plateau and high and low temperature start-up tests could not be done. Functional tests could only simulate conditions below 20,000 meters, so many things could only be installed in adventure equipment. Testing can only be carried out on prototype No. 01.”

"This time, we can make up for the content that we didn't have time to do before, especially the plateau low-temperature starting capability, which should be the top priority for our model." Although Yang Fenghata is not an aviation power expert, as the entire Eighth Three The person in charge of the project is still very online in controlling the direction of the project.

The air defense of the Qinghai-Tibet Plateau remained an extremely troubling problem until the first decade of the 21st century.

Although the innate altitude of Xigazi Airport allows our military aviation forces to theoretically gain an altitude advantage of three to four thousand meters as long as they take off, maintaining the normal operation of the aircraft at an altitude of 5,000 meters is itself a problem that has never been studied by anyone. subject.

This situation did not improve until the infrastructure construction from the mainland to Qinghai-Tibet was improved and the airstrip in Xikaz was expanded into a full-fledged air force base.

As for the current 90s...

The Triplesonic Squadron was also equipped with the MiG-25R reconnaissance aircraft that symbolized their name.

Although these aircraft are no longer able to exert their full strength due to their age and insufficient maintenance, they can still come and go freely with height and speed.

Hearing this, Chang Haonan turned slightly sideways and said:

"In fact, after this improvement, the starting efficiency of the turbojet 14 in plateau environment will also be improved."

"You even modified the starter?" Yang Fenghao's tone was filled with surprise.

He didn't recall such an item being on the list of improvements he'd seen before.

"No, but the compressor rotor is lighter than before, and the total pressure recovery coefficient has increased." Chang Haonan shook his head:

"This can compensate to some extent for the reduced air density and insufficient oxygen content."

This explanation made Yang Fenghata's eyes flash with surprise.

Obviously, there is one more gift, and it is still so satisfying——

When a turbine engine is started from a standstill, it must rely on external power.

Because there is no relative airflow flowing through the engine at this time, if oil is supplied to the main combustion chamber for ignition at this time, the engine will only be burned without causing the engine rotor to rotate.

When the engine is in a plateau environment, the mass flow of air sucked into the engine or starter is smaller than during normal startup on a plain, and the power of the starter is significantly reduced, the rotor accelerates slower, and the cold running phase of the engine is extended, which can easily lead to startup Failure, even in the case of insufficient air flow, entering the idle state in advance and damaging the engine.

However, the reduction in the quality of the compressor blades can reduce the adverse effects of the reduced power of the inefficient starter, allowing the rotor to reach the specified operating speed faster.

This is equivalent to improving the plateau startup efficiency.

After thinking for a moment, Yang Fenghao turned to Chang Haonan and Yan Zhongcheng with a happy face:

"Xiao Chang, Lao Yan, after you get to Fucheng, you must complete all the data for the plateau startup test. This is very important."

After saying this, he seemed to feel that it was not enough, so he continued to add two more sentences:

"It's okay even if it delays some progress."

"I estimate that our J-8 export plan may be implemented at this air show."