Chapter 1300: Reduce Drag and Increase Thrust

This sudden voice startled Liu Yongquan and Han Chenfeng, who had already relaxed.

The two of them turned around almost at the same time.

Now that there is an emergency, it is naturally impossible to continue the previous chatting topics, including arranging dinner just mentioned, which can only be put aside for now.

"What's the specific situation?"

Liu Yongquan strode quickly back to the console and looked at the data display terminal of the engine test bench.

Han Chenfeng almost didn't understand aviation at all, but faced with this situation, after hesitating for two years, he also chose to follow the other party and return to the test workshop.

"Mr. Liu, you see, we started the afterburner in the first two rounds of tests. The engine thrust was maintained at a high level, and the thrust fluctuations were relatively violent, so we did not observe it immediately."

Ma Xiaoyu had already adjusted the engine working thrust curve during the test just now, and introduced to Liu Yongquan:

"But when the afterburner is turned off in the middle and only the maximum speed of the compressor is maintained, it can be clearly found that the thrust after stable working condition is about 3% higher than the turbofan 10A we usually test, and it is quite stable. I just said I tried lowering the speed to 80%, but compared with the previous data, it was still almost 3% higher..."

Although the engine will enter mass production after production is finalized, as a high-value product with a small output, each aircraft engine needs to undergo ground bench testing before leaving the factory.

Therefore, Ma Xiaoyu is more familiar with the working parameters of the turbofan 10A than at his own home.

Although the factory testing environment does not meet the requirements for "sea level" thrust in the national military standards, when the testing environment and testing methods have not changed, the thrust suddenly increased by 3%, which is obviously only possible with the newly added It is related to the plasma generating equipment installed.

Liu Yongquan took out his reading glasses from his pocket, put them on and leaned in front of the computer screen to take a closer look:

"The changes are indeed obvious..."

He frowned and thought for a moment:

"Is it because the probe interferes with the flow field behind the tail nozzle?"

In fact, no matter what is placed behind the tail nozzle, it will not affect the real thrust of the engine.

However, the thrust data is tested based on sensors installed on the bench. If the flow field is severely disturbed, it may cause deviation in the results.

For example, if you go to the extreme and put a thrust reverser behind the engine, the platform will be hit by the secondary impact of the reverse thrust airflow and give higher results.

However, as soon as he finished speaking, he was denied by himself:

"No...it's just a probe, it can't have such a big impact."

For a moment, the entire control room fell into silence, leaving only the scream of the engine coming from the other side of the armored wall.

After a few minutes, Liu Yongquan still couldn't find a clue, so he decided to start the experiment first:

"Remove the probe, restart the afterburner, keep working for a period of time, and see how the average thrust compares to normal."

"yes!"

Ma Xiaoyu nodded, then turned around and started operating.

Soon, the roar of the engine that reached everyone's ears became more obvious, and the thrust curve displayed on the screen quickly increased by a level, reaching around 13 tons.

The principle of the afterburner is to make full use of the remaining oxygen in the gas and perform a second injection combustion behind the engine structure. The generated gas is directly output without passing through the turbine structure, so the thrust curve fluctuates very drastically. Indeed It is difficult to determine with the naked eye where the center of the fluctuation is.

But the computer can still give relatively representative results through the thrust data recorded over a long period of time——

If the engine thrust is not less than a certain value 75% of the time after the afterburner is turned on, then it is considered to be a ground bench test thrust.

Amid the gazes of more than a dozen pairs of eyes, a number finally appeared on the far right side of the violently changing curve on the screen.

"13711.6 kilograms of force..."

Ma Xiaoyu read it out slowly.

There was another moment of silence.

"First turn off the afterburner and adjust the speed to idle."

Liu Yongquan ordered while pacing back and forth with his head lowered:

"The factory test thrust of the turbofan 10A fluctuates slightly depending on the individual, but it has never exceeded 13,300kgF. In other words, even after the afterburner is turned on, today's result still increased by about 3.5%..."

If a new sub-model is improved, then the 4% thrust increase is indeed not very impressive.

But the key is that they don't seem to have to pay any extra price for this...

Just when everyone was racking their brains but couldn't think of any possibility, an unexpected voice sounded from not far behind:

"Old Liu."

It's Han Chenfeng who has gone and returned.

He is a complete layman in the field of aviation development, and he was just sitting next to it just to listen to the excitement.

As a result, after listening to it, I really thought of a possibility:

"This situation... I think it is most likely caused by the plasma generating device!"

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Liu Yongquan stopped and looked at Han Chenfeng with a somewhat suspicious look, but there was no other way at the moment. No matter who he was, he could only treat a dead horse as a living horse doctor.

"But what is the relationship between plasma and engine thrust... Even if it has an impact, it should have a negative impact, right?"

he asked with some confusion.

"No, it's not as simple as you think..."

As Han Chenfeng spoke, he searched around for a while, and finally pulled a whiteboard from the wall, and then removed several pieces of paper fixed with magnets on it:

"Actually, many basic concepts of plasma are not very clear yet. In situations like the one you encountered, it may be due to the hydrodynamic effect of mutual interference between plasma and shock waves, resulting in shock wave systems inside the aircraft engine. Weakening, the flow resistance decreases, so according to the most basic mechanical principles, we can know that the same work can be exchanged for a greater gas flow rate, and the reflected thrust will naturally increase. "

"Or another possibility... the plasma generates an electrostatic force on the aerodynamic boundary layer on the inner wall of the engine flow channel, thereby reducing the turbulence of the boundary layer and weakening the efficiency of turbulent vortex generation. The effect is the same Reduce flow resistance..."

"..."

After some explanation, everyone including Liu Yongquan looked at each other in confusion.

Plasma is used to absorb radar waves to achieve stealth. Both the front and rear sides belong to the category of electromagnetism. This principle is easy to understand.

But using plasma to reduce drag...

Perhaps seeing everyone's confusion, Han Chenfeng added:

"From a theoretical perspective, most of our common forces such as friction, elasticity, and thrust are essentially a type of electromagnetic force, so..."

"The more specific principle..."

Before Liu Yongquan could ask, the latter raised his hand to interrupt him and replied with a wry smile:

"The mechanism in this aspect is still very controversial. There are explanations ranging from perturbation theory to energy theory. I can only assure you that this drag reduction phenomenon 100% exists."

At this point, he paused for a moment, then continued:

"Also, although I don't know how you plan to control the plasma to form a dense shell, for your research, this should be a good phenomenon, indicating that the plasma is fully and uniformly generated, which is beneficial to subsequent operations to a certain extent. ”

Liu Yongquan, who was an engineer by training, did not have strong theoretical abilities and was not prepared to challenge his shortcomings, so he gave up asking for details and turned to Ma Xiaoyu, who was sitting in front of the computer:

"Xiao Ma, you continue to test the plasma distribution in the tail flame jet according to the original plan. I will report this situation to the 611 Institute and Academician Chang. First, let them judge whether There is no hope of applying this phenomenon to the field of aircraft design. Secondly... maybe Academician Chang will have a more accurate understanding of this phenomenon..."