The military-industrial scientific research system of the academic master.

In the following period, with the help and guidance of Chang Haonan, the prediction results of the ice accumulation morphology on the surface of the Y-8 main wing and tail wing were quickly produced.

In the cold wind of late November and early winter, in the final assembly workshop of Factory 11, a group of people were surrounding the Transport 182F that was being dragged out as a research object.

Not far from the aircraft, there are two drawing boards with three views of the main wing and horizontal tail of the Y-8 respectively.

If you look closely, you will also find that there are several irregular lines outlined in different colors around the edge of the wing.

Since the problem of wing icing involves flight safety, the work of the entire 182 factory has slowed down during this period, especially the test flight of Y8J, which was directly stalled due to the last second-class accident.

According to the schedule, the first two sets of SouShui-2000MS radars purchased from the UK will be shipped back to China soon.

Although in the preliminary preparations in the past few years, the radar part has been simulated using equal-weight counterweight models, which verified that the flight performance of the aircraft will not be too seriously reduced due to the installation of radar, it is necessary to install real electronic equipment When getting on an airplane, a series of issues such as energy consumption, vibration, working environment, and electromagnetic compatibility must be considered.

These can only be tested by going to heaven.

Therefore, if the flight test subjects cannot be restarted when the radar is shipped back to China, it will have a very negative impact on the time for the equipment to form combat effectiveness.

Some people even thought that they should build a simple multi-stage electric heating device according to the initial plan, and then slowly consider a more complete de-icing system for the next model.

In the end, Liang Shaoxiu resisted the pressure and fully supported the basic research subjects of Chang Haonan and others. Only then did he see the actual results today.

"Comrades, after nearly half a month of work, two professors, Lin Guofan and Zhu Lan, and I have completed the simulation and prediction of the growth of ice accumulation on the wings of the Y-8 aircraft, and have also determined the corresponding heating and de-icing system load. .”

Chang Haonan's first words caused a burst of applause in the huge assembly workshop.

No matter what attitude the people standing here had towards this research before, but now that the results have been obtained only half a month later, there is nothing to argue about.

If you are not worried about the project progress not being able to meet the deadline, who wouldn’t want a system that is more effective and can improve flight performance?

"The red, orange, blue and green lines in these two pictures respectively correspond to the ice accumulation on the wing section after the aircraft passes through the ice accumulation area for 120 seconds under different severe climatic conditions."

The conditions of Factory 182 are really limited. There are no digital projectors in Beijing or Shengjing. If you use slides, the resolution will be low on the one hand, and there is no way to project such a large drawing, so we have to use slides. On the drawing board, let everyone gather around and look at it.

"So under the worst weather conditions, ice accumulation is mainly distributed on the lower surface of the wing?"

Someone immediately saw the clues.

In the mid-90s, due to objective reasons such as insufficient performance of icing detectors, not to mention China, the world's research on ice damage during flight was still in a barbaric era.

Apart from anything else, even the natural icing test, which has become very popular in later generations and has even become one of the standard procedures for civil aircraft airworthiness certification, does not yet have a particularly unified and scientific standard.

Americans basically rely on the fact that the temperature in the Great Lakes region is low enough and the water vapor is abundant enough to find similar clouds to fly in.

As for other countries, they are even more impressive.

Fortunately, the flight conditions of most jet aircraft are already on the edge of the icing area, so the number of air accidents related to ice accumulation in civil aviation is still within an acceptable range, and most of them are regional passenger aircraft such as the ATR72. Smaller general aviation aircraft such as the Cessna 172 will have a relatively limited impact.

Therefore, the results of this simulation are indeed somewhat counterintuitive to most people.

"The flight speed of the Y-8 aircraft is already relatively fast among propeller aircraft. According to our research, when the inflow speed exceeds 75m/s, supercooled water droplets will have a greater impact on the wing surface. There is a probability of impact rollback, rather than normal spreading and viscosity, so the upper surface of the wing with faster airflow is relatively clean."

"Furthermore, even if ice forms on the upper surface of the wing, since the faster incoming flow speed corresponds to a smaller incoming flow angle, the ice shape will mainly be frost ice without overflow process. The adhesion ability is very poor and the ice surface The shape is very close to the shape of an aircraft wing, and the damage is much weaker than the life ice on the leading edge and lower surface."

"If this is an aircraft flying at a relatively slow speed, such as the Y-5, then the ice accumulation area to focus on will become the leading edge and upper surface of the wing."

Chang Haonan's explanation was clear and clear, and the engineers surrounding him quickly understood:

"So we, or almost all the de-icing devices for large propeller aircraft in the past that were built based on experience, actually missed the point?"

"Yes, a lot of energy is wasted."

Chang Haonan nodded, then picked up the pen again and pointed at the horizontal tail part:

"Another point is that the degree of ice accumulation on the aircraft will weaken as the chord length of the wing increases. That is, the closer to the outside of the wing, the less likely it is for ice accumulation to occur. This can also explain why ice accumulation occurs on the horizontal tail. Often more severe than the main wing.”

"According to our research, in quite a few cases, ice on the wing not only does not cause a decrease in lift, but also provides an additional positive pressure area due to the strong vortex formed in the back area of ​​​​the ice. For an aircraft with a normal layout, For example, there will be a strong bowing moment, which is why the previous Y-8J had an accident."

"..."

After Chang Haonan, there were Lin Guofan who introduced the impact of meteorological factors on ice accumulation problems, and Zhu Lan who introduced the microstructure design of the wing surface.

This small-scale seminar held in the assembly workshop lasted until that night, and even dinner was delivered by someone from the canteen.

As the three people's explanations continued, a new set of ice accumulation theories was gradually laid out in front of all participants...

"Then, as long as we provide different de-icing designs in different areas of the wing according to different ice accumulation conditions, we can greatly improve the anti-icing capability and improve energy consumption levels."

“According to our calculations, after applying the cylindrical surface microstructure designed by Professor Zhu Lan to the leading edge of the wing where the ice accumulation is the most serious, under the working conditions corresponding to these four lines, the amount of electric heating required for each meter of the wing to de-ice The system power requirements are 160 and 1430W respectively, while the converted thermal power of the gas thermal de-icing system is 128 and 1265W respectively.”

"Even if a 50% safety margin is considered, it will save 65% of electrical energy and 85% of thermal energy compared to the previous Soviet design."

"Especially the latter, when the hot gas de-icing device is turned on, it can directly increase the engine output by about 8%!"

Chang Haonan said this and dropped the pencil in his hand on the table in front of him:

"So, comrades, our next job is to design the two corresponding sets of de-icing devices based on the calculation results, and match them with the internal structure of the wing, so that the veteran Yun-8 can be reborn!"

Note: The issue of flow velocity on the upper and lower surfaces of the wing in this chapter is explained using Bernoulli's principle (high flow velocity brings low pressure) that appears in middle school textbooks. But strictly speaking, people still don't fully understand the question "why airplanes can fly." There are several different schools of thought regarding the specific source of wing lift.