The Military-industrial Scientific Research System of the Academic Master Chapter 511

Chapter 511 Turbofan 9A preparing to tap its ultimate potential

Chang Haonan certainly didn't mean to look down on Teacher Yang Huimei.

But to be honest, the subject of management itself is more practical than theoretical.

There is really no need to take the paper too seriously.

As a professor of management, being able to arrange jobs for all the graduate students under his command is a reflection of his ability...

In short, after sending Xu Yang and Yang Huimei away, Chang Haonan finally took care of the first thing of the day.

　　It also settled a minor worry.

The paper itself is of course of little use to Chang Haonan, but he is somewhat looking forward to the impact it may have on the Torch Group and even the entire Chinese academic community.

There are two other emails left in the mailbox.

The content of the second email is much more ordinary in comparison.

It was Liu Hongbo, who had already started working in Bingcheng, asking whether the technical ideas for helicopter sound field simulation were feasible—

Helicopters are slow and have poor maneuverability. The core of their survivability is the concealment brought by the height of the treetops. If they are discovered a few kilometers in advance, it will greatly increase the risk of being attacked by concentrated fire.

The price is increased weight and complexity of the rotor.

However, in the current 1990s, research on "quiet rotors" in various countries is generally still in its infancy.

“Currently, the calculation of helicopter rotor noise basically uses the Lighthill acoustic analogy method based on the FW-H equation.”

Chang Haonan gathered his thoughts and began to think about the content of the email.

Generally speaking, the best way to suppress HSI is to increase the rotor diameter/number of blades and reduce the linear speed outside the blades.

For military helicopters, excessively loud and easily identifiable sounds can also make it easy to be detected in advance.

After thinking about it, Chang Haonan pulled out a few sheets of A4 paper from the printer tray next to him.

As long as it's not too outrageous.

The so-called quadrupole source nonlinear noise is medium and high-speed impulse noise (HSI).

Although Mi-28, AH64 and other models have tried to use some qualitatively effective technologies, in general, noise still ranks relatively low in everyone's performance requirements for helicopters.

Since lift is mainly obtained by the rotor, this type of HSI noise may not only cause hearing damage to the members inside the aircraft, but also cause instability factors such as rotor tip flutter, affecting flight safety.

"After several days of trying, I found that this method performs well in calculating rotor thickness and load noise, but it cannot be used to solve the nonlinear noise of the quadrupole source, resulting in abnormally high noise during the helicopter's hovering/forward flight process. …”

For helicopters, the impact of noise is not just a matter of comfort.

It should be said that the depth of research conducted by Bingfei Group was higher than he had previously expected.

“And if we completely use experimental methods, on the one hand, the 122nd Factory and the 602nd Institute do not have enough acoustic laboratories for helicopters, and on the other hand, the cost and development cycle cannot be guaranteed..."

Helicopters like the Zhi-9, which already have limited power, and the 122 Factory, whose technological level is far behind that of European original manufacturers, obviously do not have the conditions for this...

“I am trying to calculate the flow field first, and then determine the rotor vibration through the flow field, thereby indirectly calculating the sound field to get the results, but there are some issues that need Mr. Chang's guidance..."

When the rotor speed is high, shock waves may exist on the surface of the rotor blades and extend to the spatial area. The flow field exhibits transonic and strongly nonlinear characteristics, and will emit very penetrating and discernible pulses. sound.

Sound = vibration.

Anyone who has ever done it knows how frustrating it can be to write formulas on a computer.

Immediately afterwards, while sorting out the calculation ideas that emerged in his mind, he began to write furiously:

"The FW-H equation has shortcomings in the universality of the research problem. The essence and premise of accurately calculating the rotor sound field is to calculate the rotor flow field. As long as the shock waves and tip vortices that may exist in the flow field can be captured through calculation, acoustics It is not difficult to ensure the accuracy of calculations..."

“Specifically, you can try to obtain the far-field sound pressure characteristics by integrating the sound pressure value on the surface surrounding all sound sources. The sound pressure value on the surface can be determined by Kirchhoff's formula..."

“In actual numerical calculations, the integration surface must be discretized into small surface elements, and the integration is performed on each surface element. The final result is the superposition of the contributions of each surface element, and dS is the area of the micro-surface element…”

"The information obtained from the flow field calculation can be calculated on the Kirchhoff surface through interpolation and other methods. For the unstructured overlapping grid of the new version of TORCH Multiphysics, a method similar to the generation of hole boundaries in nested grids can be considered To determine the integral surface…”

"Manually given a space surrounding the blade, which is similar to a "hole" in a nested grid, first loop through all the grid points and determine whether the point falls within the hole according to the spatial coordinates. If the point falls within the hole , then mark the point as 0, otherwise it is 1..."

“As for the flow field calculation, the essence is back to the numerical solution of the N-S equation. This is the core function when the TORCMultiphysics software was created, and I will not go into details here..."

“This is my understanding of the above-mentioned issues. It is just one person's opinion and is for reference only.”

“And I wish you a successful completion of your project.”

The five pages of A4 paper were written very eloquently and quickly.

After briefly checking that the content just now was correct, Chang Haonan put several pages into the scanner.

Sheet-fed scanners were invented in the early 1990s and have now entered the Chinese market.

Although the price is ridiculously high, Chang Haonan is not too poor with money after all, so he still gritted his teeth and equipped each office with one. After scanning it in, he directly sent the content as an attachment to Liu Hongbo in Bingcheng.

After dealing with the two things without incident, Chang Haonan looked at the clock on the wall.

It's almost time to have lunch.

He clicked on the last unread email.

This is a routine work report of the Turbofan 10 project.

The kind that will be sent out every few days.

He planned to have lunch after a brief look.

However.

“Experimental results of flow heat transfer characteristics of special-shaped air film holes”—

When he saw this title, Chang Haonan knew that he would not be able to eat his lunch.

This research is crucial for the design of combustion chamber and turbine structures of aeroengines.

He has previously used the basic control equation of flow heat transfer to calculate the film cooling effect of different shaped holes.

But after all, this is a research direction that has never been done before, and experimental results are still needed to correct the numerical calculation method.

That's why it has been postponed until today.

Thinking of this, he couldn't sit still anymore. He quickly turned off the computer and put on his coat, ready to see the results.

There is so much experimental data over the past month that it is impossible to send it all via email.

In the Compressor Research Center of Beijing Hang University, Liu Yongquan, wearing a blue lab coat, stood in front of two computers recording experimental data.

Next to him is Chang Haonan, who is looking at the experimental data attentively and comparing it with his own calculation results.

"Judging from the results, for our experimental subjects, the cooling effect of dustpan-shaped holes is better than fan-shaped holes and simple forward-inclined holes. However, the influence of expansion ratio, hole inclination angle and expansion angle on cooling efficiency is still relatively complicated. …”

Chang Haonan stared at the two screens at the same time and slowly gave his judgment.

“Actually, the key is that we do not have the means to directly measure the velocity and pressure distribution in the air film holes. On the one hand, we cannot buy the relevant sensors, and on the other hand, even if they are obtained through special channels, the accuracy cannot meet the requirements..."

Liu Yongquan said from the side, obviously still a little regretful.

“When we engage in scientific research in China, we have never reached a stage where we get everything we ask for.”

Chang Haonan doesn't really care:

“The velocity and pressure distribution in the hole are the cause, and the displayed temperature field distribution is the effect. If the theoretical tools are advanced enough, even if the former cannot be obtained directly, it can be inferred from the result.”

Liu Yongquan opened his mouth, but was so shocked by Chang Haonan's confident words that he had nothing to say for a moment.

After a while, he spoke again:

“Under different environments, the heat dissipation effects of various hole types will also be somewhat different.”

“For this part, it is not very useful to just test it in a laboratory environment. Actual testing is still needed to prove the feasibility of our design.”

Of course Chang Haonan has been prepared for this kind of thing:

“This is no problem. I will contact Liming Factory this afternoon and ask them to prepare to apply the new cooling technology on the second-stage prototype of the turbofan 9A.”

“Whipfan 9A?”

Liu Yongquan was stunned:

“But the temperature in front of the turbine of turbofan 9 is a bit too low for our technology, and no effect can be measured..."

“Just modify the atomization level of the fuel injection structure and increase the temperature of the combustion chamber.”

Chang Haonan raised his head and said:

“Although the foundation of Turbofan 9 is average, the value of continuing to tap the potential will not be too great, but we are just changing the design without changing the process and materials, and the cost will not increase too much.”

“The temperature in front of the turbine of the improved model is increased, which can at least improve some supersonic performance and reduce some additional fuel consumption.”

Seeing what he said, Liu Yongquan naturally had no objection.

“Mr. Chang, you are trying to squeeze out all the potential of Sibei...”

The words were somewhat complimentary.

“It's best to make the best use of everything. There are so many units in the Air Force waiting to be replaced. It will also be a big help to get the JH-7A out early..."

(End of this chapter)

Chapter end

Report