Chapter 49 J-7F [Recommended for the critical period, please read it! 】

One morning a week later, inside the wind tunnel testing center of the 611 Institute.

Lu Yuying sat in the control room, waiting for the newly put into use wind tunnel to complete all the debugging work required for the inlet duct test.

And next to him was the hastily produced scale model.

After the meeting with Chang Haonan, Lu Yuying flew back to Chengdu almost non-stop with all the information provided by the former, and then quickly arranged for his engineers to work in two shifts 24 hours a day to start the final improvement of the design plan. .

Since Chang Haonan has almost completed all the theoretical foundations and simulation tools required for the integrated design method of the air inlet/front fuselage, the entire initial design and proportional model manufacturing process has changed from the repeated obstacles in the previous period and has been carried out successfully. Very smooth.

In addition, considering that almost all of these technical materials are in electronic form, it is logical that Lu Yuying also tried computer-aided design in the completion process of this new J-7F plan.

In the first two or three days, due to various reasons such as lack of proficiency in software operation and even some veteran engineers not knowing how to use computers, the progress was not even as good as the traditional method.

But after Lu Yuying withstood the pressure and replaced a group of young people, the efficiency advantages of computers gradually began to be reflected.

Even many comrades who complained at first expressed their unwillingness to use pencils and drawing tablets again after adapting.

Under the buff of such multiple factors, within a week, they even came up with two versions of the design that were slightly different.

What is being tested today is a version called the J-7F2.

Soon after, an engineer wearing light blue overalls walked in holding a report:

"Reporting to Mr. Lu, the wind tunnel inlet test system has been calibrated. The repeatability accuracy of the flow coefficient, total pressure recovery coefficient and distortion index are all within the range required by the design specifications. It is fully capable of undertaking formal model tests."

"Okay, get ready to start."

As Lu Yuying signed his name on the report, the wind engineers began intensive preparations.

Each working time of the supersonic wind tunnel is very short. Depending on the speed of the test, the long time can only reach tens of seconds, and the short time may only be a few milliseconds.

It often takes months or even years to fully test an aerodynamic design.

However, since the changes to the J-7F were not major, Lu Yuying’s focus on testing this time was only the nose and air intake.

Coupled with the simulation tools provided by Chang Haonan, the selection of test conditions is also targeted, and the number of tests required is only a fraction of the usual number.

Therefore, early in the morning on the third day after the test started, Lu Yuying, who was sleeping in the office, was called to the wind tunnel center by a phone call.

"Mr. Lu, the difference between the wind tunnel test results and our previous calculation results is very small. There is no problem with this design!"

After seeing Lu Yuying's figure, the engineer who had been on duty at the wind tunnel came over excitedly with the test report:

"The design method you brought back from Beijing this time is simply amazing. It can almost match the intake air flow rate below 70%, and this performance is simply inferior to our previous designs. Heaven and earth!"

Lu Yuying took the report and turned directly to the final conclusion.

"Okay, okay!"

Although he only uttered three words, it is not difficult to see from his trembling hands and facial muscles that this senior aircraft designer is also in great excitement, but with a higher concentration.

"It's a pity that there are currently no conditions for TPS model simulation in China. The accuracy of the simulation results of our ejection model under higher intake air flow conditions is average, so we can only do this."

The young engineer who had just brought the report said with regret.

As for the wind tunnel, it doesn't mean that you can immediately use the full capabilities of a piece of hardware.

In addition to the wind tunnel itself, the model used for the experiment, the way the test data is obtained and post-processed, and even the way the model is supported will affect the accuracy of the test.

Take the model just mentioned as an example. The TPS model, which has been widely used in developed countries since the late 80s, except that the internal exhaust cannot simulate high-temperature gas, other conditions are very similar to those of real engines, which can save a lot of test flight hours. .

Even for an ejection model with a relatively simple structure, the Siberia Chaplekin Institute of Aviation Science and Technology can achieve 100% simulation of the intake air flow through its rich design experience.

For the same model, the 611 Institute can only simulate 70%-80%.

It’s very helpless, but this is the foundation of China’s aviation industry.

"Step by step, our country's foundation is indeed weaker in comparison, but as long as we don't give up the pace of catching up, we will one day be able to make up for all these gaps."

When he said this, Lu Yuying almost subconsciously thought of Chang Haonan whom he met at Beijing Hang University.

If he was still 1% doubtful before, now looking at the report in his hand, he is completely convinced that the other party is the kind of peerless genius who can single-handedly promote technological progress.

"The next step is to build a prototype and then prepare it for flight."

Lu Yuying said proudly.

"But Mr. Lu, our funds for this project... are almost running out."

The engineer next to him warned carefully.

Because this new J-7 variant has not found a launch user, the R&D funds so far have been squeezed out by the 611 Research Institute itself. It is barely enough for paper design and wind tunnel testing, but if you want to actually build one A plane is just a drop in the bucket.

"It doesn't matter. There is a seminar this afternoon between the project leaders of our institute and the nearby brother factories. I will solve the money problem."

Lu Yuying said as he put the report in his briefcase into his briefcase and hurriedly left the wind tunnel test center.

……

In the afternoon of that day, Lu Yuying directly brought two versions of the J-7F design drawings, wind tunnel model and wind tunnel test results to the venue.

"The preliminary design of the improved J-7F is currently going well, and the wind tunnel test results show that its flight performance is significantly improved compared to the current J-7E..."

"Last year, that is, in 1995, Israel upgraded a batch of deeply improved models called MiG-21 Lancers for Romania. This proves that many countries still need a low-cost second-generation improved fighter jet..."

"Taking into account the market prospects, we have specially designed two sub-models, namely the J-520F21 with a radar diameter of 7mm, which can be directly upgraded from a MiG-7F or J-1M fighter jet, and the J-600F7 with a radar diameter of 2mm, but must be newly manufactured. …”

"During the development process of the J-7F, we cooperated with Beijing Hang University and tried to adopt a fully digital design method for the first time, which greatly accelerated the design process. At the same time, we can also accumulate experience for the digital design of other models in the future..."

"To sum up, we believe that although the J-7F model does not have a customer launch, it has good market prospects and technical value, and can be considered for research and development in the form of self-raised funds."

After Lu Yuying's introduction, the audience fell into silence for a few seconds.

Thanks to the book friend [Danqing Mozi] for the 500 starting coin reward

Thanks to book friend [Xiao Xiao Zhen Zhen] for the 100 starting coin reward