Chapter 157 Saving the Y-8 Yun-8
In the following period, with the help and guidance of Chang Haonan, the prediction results of the ice accumulation morphology on the main wing and tail surface of the Y-8 were quickly produced.
In the cold wind of late November and early winter, in the final assembly workshop of Factory 182, a group of people were surrounding the transport 8F that was being dragged out as a research object.
Not far from the aircraft, there are two drawing boards on which three views of the Y-8 main wing and horizontal tail are drawn.
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 with a counterweight model of equal weight, verifying that the flight performance of the aircraft will not be too seriously reduced due to the installation of radar, but it must When installing real electronic equipment on an aircraft, 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 test flight 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 The 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 meeting 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 changes in the wing section after the aircraft passes through the ice area for 120 seconds under different severe weather conditions. The growth of ice. "
The conditions of Factory 182 are really limited. There is no digital projector in Beijing or Shengjing. If you use slides, on the one hand, the resolution is relatively low; on the other hand, the There was no way to project such a large drawing, so I had to put it on the drawing board and let everyone gather around to 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-1990s, 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.
Not to mention 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 hit the wing surface. Afterwards, there will be a greater probability of impact rollback, rather than the normal spreading and viscosity phenomenon, so the upper surface of the wing with faster airflow is relatively clean."
"And even if the upper surface of the wing is relatively clean. When icing occurs, because the faster incoming flow speed also corresponds to a smaller incoming flow angle, the ice shape is mainly frost ice without overflow process. The adhesion ability is very poor and the shape of the ice surface is very close to the shape of the wing. The hazard is much weaker than the life-threatening ice on the leading edge and lower surface.”
“If this is an aircraft flying at a slower speed, such as the Y-5, then the ice accumulation area to focus on will change. It forms the leading edge and upper surface of the wing.”
Chang Haonan’s explanation was clear and clear to the surrounding engineers:
"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 large part of the 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 increase with the chord length of the wing. It weakens with the increase, that is, the closer to the outside of the wing, the less likely it is for ice accumulation, which can also explain why the ice accumulation on the horizontal tail is often more serious than the main wing.”
“According to our research. , in quite a few cases, icing on the wing not only does not lead to 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, this will The strong bowing moment caused the accident of the previous Y-8J.”
"..."
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 base on different ice accumulation theories According to the situation, different de-icing designs in different areas of the wing can greatly improve the anti-icing capability and improve the energy consumption level. ”
“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 160W, 465W, 992W and 1430W respectively, while the converted thermal powers of the gas thermal de-icing system are 128W, 402W, 817W and 1265W respectively. ”
“Even considering a 50% safety margin. It also saves 65% of electrical energy and 85% of thermal energy than the previous Soviet design. "
"Especially the latter, when the hot gas de-icing device is turned on, it can directly increase the engine speed by about 8%. Output power!"
When Chang Haonan said this, he dropped the pencil in his hand on the table in front of him:
"So, comrades, our next job is to, based on the calculation results , designed two corresponding sets of de-icing devices and matched them with the internal structure of the wing, giving the veteran Yun-8 a new lease of life.”
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
(End of this chapter)