In fact, the reason why Chang Haonan was so anxious to come to the 410 factory to check the production of the engine, in addition to having an understanding of the domestic aviation power production level in order to carry out some layouts in advance, another very important reason is that he also remembered that when he checked the test flight data of the No. 01 prototype before, he found that the working state of the two turbojet 14 on the plane was very unstable.

If this phenomenon occurs only on the unit that malfunctions, it can be considered a pre-surge symptom.

However, the actual situation is that there is a similar phenomenon between the two engines, and even the two on the No. 03 prototype that Chang Haonan later went to check.

And the magnitude of instability is not the same.

In this case, it means that the problem is most likely in the manufacturing process.

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

But it's not enough.

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

The more stable the working state of the engine, the shorter the distance between these two curves needs to be left, which is equivalent to "squeezing" more actual performance under the same theoretical limit.

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

So if we can find and solve that instability, we can further improve the actual performance of this engine.

But it's obviously not that easy.

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

As a person who was not deeply immersed in the field of mechanical engineering, he really failed to find out which step went wrong.

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

Fortunately, even if there are subsequent improvements in manufacturing, they are still in the category of production stereotype, so they will not affect the current work.

……

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

The prototype of the Turbojet 14, numbered 010001, had been rolled off the production line from Plant 410 the night before and had been shipped here overnight.

It almost pins the hopes of the entire 606 Institute and the entire 83 Project.

In fact, when this engine was assembled and tested off the assembly line, everyone had already discovered that it was different from the original design -

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

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

What's more, it was reduced by 10% in one go.

Even if nothing else changes, weight reduction alone is enough to take the performance of the Turbojet 14 to the next level.

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

The 110 kilograms can only be regarded as a giveaway.

If the giveaways are already so surprising, how can you not expect the performance of the engine itself?

Yang Fenghat, Yan Zhongzhong and Chang Haonan stood together, watching the engine, which had poured thousands of people's efforts, to be fixed on the cargo pallet, and then slowly entered the cabin of the Y-8.

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

Yang Fengfa was wearing a leather jacket, put his two hands into his sleeves, and asked Yan Zhongzhong next to him:

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

"Yes......" Yan Zhongzhong nodded, tightened the cotton clothes wrapped around his body again, and raised his head slightly, as if he was recalling something:

"At that time, the high-altitude platform of the 624 Institute was still under construction, and the air intake distortion test, as well as the plateau and high and low temperature start-up tests could not be done, and the functional test could only simulate the situation below 20,000 meters altitude, so many things could only be tested by risking to be installed on the No. 01 prototype."

"This time, I can make up for the content that I didn't have time to do before, especially the plateau low-temperature starting ability, which should be regarded as the top priority of our model in the future." Although Yang Fenghata is not an expert in aviation power, as the person in charge of the entire 83 project, he is still very online in his control of the direction of the project.

Air defense on the Tibetan Plateau remained an unusually problematic until the first decade of the 21st century.

Although the innate altitude of the Xikhaz airfield allows our aviation units to theoretically gain an altitude advantage of three to four thousand meters just by taking off, maintaining the normal operation of aircraft at an altitude of 5,000 meters is itself a topic that has never been studied.

This situation did not improve until the infrastructure of the interior to Qinghai-Tibet was improved, and the airstrip in Xikhaz was expanded into a full-fledged air base.

As for the current 90s......

The trisonic squadron was also armed at this time with the MiG-25R reconnaissance aircraft, which symbolized their name.

Although these aircraft are no longer at their full strength due to age and lack of maintenance, they are still free to move around at altitude and speed.

Hearing this, Chang Haonan turned over slightly and interjected:

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

"You even changed the starter?" There was surprise in Yang Bonghata's tone.

He didn't remember an item in the list of improvements he had seen before.

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

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

This explanation made a hint of surprise flash in Yang Fenghat's eyes.

Obviously, there's one more giveaway, and it's still so satisfying -

Turbine engines must rely on outside power when they are started from a standstill.

Because there is no relative air flow through the engine, if the main combustion chamber is fed with oil and ignited, the engine will only be burned out and the engine rotor will not be rotated.

When the engine is in a plateau environment, the air quality flow rate of the engine or starter sucked into the engine or starter becomes smaller when it is started normally than in the plain, and then the starter power is significantly reduced, the rotor acceleration slows down, and the time of the cold running stage of the engine is prolonged, which can easily lead to the failure of starting, and even enter the slow state in advance and damage the engine in the case of insufficient air flow.

However, the reduced mass of the compressor blades can be inefficient and the power of the starter can be detrimental, allowing the rotor to reach the required operating speed faster.

It is equivalent to improving the efficiency of plateau starting.

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

"Xiao Chang, Lao Yan, after you get to Fucheng, you must complete the data of the plateau launch test, which is very important."

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

"Even if you delay some progress, it's fine."

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

(End of chapter)