Chapter 173 Electrical Discharge Machining
After both parties confirmed the project details and confirmed that they had no objections to the preliminary plan formulated by Chang Haonan, they were worried that Ye Changmengduo would be robbed again. Chang Haonan’s 611 used the fastest speed to The project was submitted.
Although it is the busiest time at the end of the year, this project still received the green light from the Science and Technology Commission, and the entire process was completed in only a few days.
When Chang Haonan took the plane back to Shengjing, an engineer from the 611 Institute who had participated in the J-7F design work was already following him.
On the Eighth-Three Project, there were only some scattered test flight subjects that needed to be completed at the trial training base to be supplemented. There was no work that Chang Haonan needed to complete, so after landing, he rushed directly to the task force responsible for the turbojet 606 Institute of 14 engine performance tuning.
Compared with the J-8C equipped with two engines, the J-7F, which is lighter, smaller and has a single engine, requires its own power to have higher reliability and lifespan, but its thrust requirements are not high.
For this purpose, the 606 Institute has specially developed a new model, the turbojet 14B.
There are not many specific changes. The main ones are to reduce the temperature in front of the turbine at the expense of about 5% of the thrust, in exchange for a lower failure rate, and to increase the first turnover cycle from 150 hours to 250 hours. .
At the same time, the power of the generator supporting the engine was increased from the original 18kw to 20kw.
After all, there is only one engine, but it has to drive a KJL7 radar with high power, and some margin must be left to deal with other subsystems.
Accordingly, the model originally installed on the J-8C was named Turbojet 14A
This work is not difficult. Therefore, although the chief designer Yan Zhongcheng has focused mainly on the aviation of the Turbojet 14, In terms of changing the design of the gas engine, other people in the Kunlun engine project team relied on Chang Haonan’s previous design experience to complete improvements.
This kind of efficiency greatly exceeded Chang Haonan's expectations, and after some inspections, he also determined that there was nothing wrong with the design of the turbojet 14B.
For China Aviation Industry in the mid-1990s, it was very gratifying to be able to achieve this level of fine-tuning of engine performance at once.
“Factory 410 has started to produce a prototype of this model. If there are no problems in the factory test, it will be sent to Chengdu for installation and matching in about two years.”
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This change is very small, especially for sub-models that reduce performance. Generally, there is no need to conduct complete ground and air platform tests as before.
However, Chang Haonan was not happy for long.
One morning two days later, he had just finished breakfast when he was stopped by Liu Dan, the deputy chief designer in charge of model improvement.
"Chang Gong, the news from the 410 factory is that the turbojet 14B prototype broke down during the factory test."
After hearing this sentence, I was still a little confused. Chang Haonan suddenly woke up.
He took several deep breaths to calm himself down.
Engine problems at this stage are not necessarily a bad thing.
Moreover, the failure was not an accident, which means the situation was not particularly serious.
“Let’s go to Factory 410.”
……
The group soon arrived at the 410 Factory not far away.
The person in charge of the reception was Chang Haonan’s old acquaintance, Zhong Shihong, the director of the technical department.
He led everyone to the testing workshop behind the production workshop.
An engine is being installed on the test bench.
The overall structure here looks a bit similar to the SB101 high-altitude platform of the 624 Institute, but it does not have the ability to simulate high-altitude environments. It is just a place to fix the engine and test whether it can work normally. From the outside, this turbojet 14B has no damage.
It also verified Chang Haonan’s previous guess that the problem should not be serious.
"This prototype machine was assembled the afternoon before yesterday. Routine factory testing began in the evening, and the problem was quickly discovered."
Zhong Shihong walked to the control room next to him and called up Relevant test data were obtained:
“When the engine is at maximum thrust but the afterburner is not activated, the working condition of the compressor will fluctuate violently without warning. By this morning, There was an alarm in the combustion chamber. After we shut down the engine for cooling, we checked and found that the first-stage turbine blades had been damaged, but the test time had only passed less than thirty hours.”
"We have conducted many rounds of investigations, but in the end we still couldn't find out the cause, so we can only contact you to see if we can determine what the problem is."
After hearing this introduction, 606 Institute The biggest worry here is not the prototype itself, but the turbojet 14A that has entered small batch production.
After all, it is related to the design and finalization of the J-8C.
However, it seems that this point has been estimated for a long time. Before anyone could ask, Zhong Shihong said that several turbojet 14A produced at the same time did not have similar problems and the test was completed very smoothly. .
While Chang Haonan breathed a sigh of relief, he was also quite confused.
Most of the parts of the turbojet 14B are exactly the same as the turbojet 14A, so a large number of parts from the same batch will be directly used for assembly.
The result is that there is a problem with the model whose parameter orientation is low performance and high reliability?
This suddenly reminded Chang Haonan that when doing ground simulation tests for aircraft engines in Fucheng, Yao Mengna's test process of the temperature field distribution in front of the turbine seemed to have similar results.
When the throttle valve is near the minimum afterburner and maximum thrust, the temperature field distribution is the most unstable. If you continue to increase the thrust, the situation will gradually get better.
At that time, everyone could only locate the problem in the process of air film hole processing, and did not find a more specific reason.
Chang Haonan slowly walked to the test bench and picked up the damaged turbine blade from the table.
Because it uses air film holes for active cooling, it is covered with dense circular holes, which is extremely unfriendly to patients with cryptophobia.
“Minister Zhong, how do you process these film cooling holes when you produce turbine blades?”
After hearing this question, Zhong Shihong’s face couldn’t help but reveal A trace of pride:
“These small holes have a diameter of only 0.25 to 0.30mm and are difficult to process mechanically, so we can only use EDM deep hole processing technology. Our 410 factory specially used 100A EDM for this purpose. The flow electrode of the machine tool was changed to a hollow rotating copper electrode, allowing the coolant to flow inside the copper tube. This solved the technical problem of short electrode life and manufactured the turbine blade of the Turbojet 14. ”
"Well...is this the mainstream processing method in the world now?"
"That's not the case. Western countries generally use electro-hydraulic beam processing, but our country's foundation in the field of electrochemistry is really poor. Weak, and related equipment is restricted and cannot be purchased, so we have no choice but to go the EDM route."
Zhong Shihong shook his head:
"But the entire turbine. We strictly follow the world's advanced standards for other blade manufacturing processes, so you can rest assured in terms of quality. "
"The testing standards are also based on them?"
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After hearing this, Chang Haonan finally realized.
"Then I probably know where the problem lies."
(End of this chapter)