Xiao Weiguo looked at the more than 30 technicians at the conference table, and he already had a plan in his heart, he stayed up late last night and worked overtime, and finally had the best solution, of course, he only knew theoretically that to finally solve the problem of fatigue cracks in turbine blades, it was still necessary to rely on these people here.

"Designers and engineers, you've done a great job!" Xiao Weiguo said gratefully, "You have worked hard for the development of the Wind Thunder Jet Engine, which we have seen in our eyes and remembered in our hearts." The turbine is the component with the largest thermal load and power load in the jet engine, so it is inevitable that such problems will arise in the development process! After all, we're walking a path that no one else has ever taken. There may be more problems and difficulties waiting for us, but as long as we think of ways to solve them, we can definitely solve them. ”

Speaking of this, Xiao Weiguo picked up the accident report in front of Messerschmidt and said loudly: "From your investigation report, I have found the root of the problem. The crack in the turbine blades of the wind and thunder jet engine was not caused by the dynamic load, so the solution to this problem is not to replace the superalloy material or improve the process. So, what is the cause of the turbine blade crack produced by the wind and thunder engine during the long-lasting test run? One detail you may not have noticed is that all the cracks pass through the leading or trailing edge of the blade and are perpendicular to the edge of the blade! And this time the cracks are mainly concentrated in the tip of the blade! What does this mean? This shows that the cause of cracks is thermal stress! ”

Messerschmidt didn't know that Xiao Weiguo already had an answer, and when he heard him say this, he suddenly felt that this question seemed to be solved soon, so he asked with great interest: "Philip, it turns out that you already have the answer!" Let's talk about why it is caused by thermal stress. What can we do to solve it? ”

The rest of the technicians also stared at Xiao Weiguo, they wanted to know why Xiao Weiguo knew the cause of the problem as soon as he came, they studied it for several days, but they were at a loss, and finally they could only hurriedly make a conclusion that now seems to be a serious mistake. As a matter of fact. This time, Xiao Weiguo was equivalent to giving these technicians a vivid lesson, and there were not many opportunities like this, so everyone listened carefully and recorded carefully.

Xiao Weiguo said with a solemn expression: "You must know that the factors that affect the low-cycle fatigue life of high-temperature turbine rotor blades mainly include the thermal stress caused by thermal shock, the tensile force generated by high-speed rotating centrifugal load, aerodynamic force and metal material properties. The majority of the total life of turbine blades is lost during start-up and shutdown due to transient thermal stresses. Therefore, from this point of view, we have not done enough basic experimental research, which is why such a problem arises. So what's the most effective way to solve this problem? Instead of using new superalloy materials or lowering the temperature before the turbine, we will improve the performance of the engine in the future. This is mainly achieved by increasing the pre-turbine temperature. So now the problem comes, the solution to the fatigue crack of the turbine blade is to focus on the cause of the problem. Since it is caused by thermal stress and cannot reduce the temperature before the turbine, then we can also reduce the operating temperature of the turbine blades by other methods! ”

One designer broke through and said excitedly: "I thought of it! Is it possible to introduce cold air to cool the turbine blades of the engine? Moreover, this cold air can only pass through the inside of the engine turbine blades, like the radiator of a piston engine! ”

Xiao Weiguo nodded and said, "You're right!" We are designers and engineers. It is to think more about problems with divergent thinking. The use of effective cooling measures is a strong guarantee for the safe and reliable operation of the engine, and it is also an effective measure to reduce the cost of high-temperature materials. In the future, we will increase the thrust of the engine. It is mainly achieved by increasing the temperature of the inlet gas of the engine turbine, but the heat-resistant temperature of the superalloy material is always limited, which depends on the advanced design to effectively reduce the temperature of the engine turbine, especially the turbine blades. Our engine turbine blades are designed to be hollow, i.e. to cool the blades, but currently our blade cooling design is problematic and does not bring in cold air to cool the blades. This creates fatigue cracks in the turbine blades. ”

Messerschmidt asked curiously: "Philip, how should we design to better cool the turbine blades of the engine?" ”

Xiao Weiguo said: "We have to design a cooling system. Of course, for the reference of cooling air, the issues of pressure, flow and temperature must be taken into account. Cooling air can be drawn out of the compressor. The air pressure of different stages is different, and it is necessary to ensure that the cooling air can flow along the cooling surface in a certain direction and speed, and the pressure at the discharge of the cooling air must also be considered. The flow rate of cooling air depends on the cooling requirements, which needs to be fully considered and designed and debugged, and the flow limiting hole can be used to adjust and divert the local cooling air volume. The cooling air comes from the compressor, and the temperature of each stage of the compressor is different, and some of them reach more than 200 degrees, so the air is not suitable for cooling. ”

Messerschmitt nodded and said, "Philip, I understand what you said. However, is this cooling system alone sufficient to ensure that the turbine life of the engine meets the design target? ”

Xiao Weiguo said with a smile: "In fact, this cooling system can already solve the current problem. Of course, there are other ways to make the turbine last longer and more guaranteed, but it will not be possible to use it for a while, and we can apply those new technologies in subsequent improved models in the future. Let me briefly talk about the two technologies for improving the fatigue strength of turbine blades, one is surface strengthening, and the other is surface protection. ”

Messerschmidt said curiously: "Philip, tell me how these two technologies are implemented!"

"Surface strengthening is one of the effective ways to improve the fatigue strength of turbine blades, such as surface hardening and surface rolling. These process measures to strengthen the surface layer can improve the surface hardness of the turbine blades, thereby reducing the surface damage of the turbine blades, and the most important thing is to form a surface layer with compressive residual stresses on the surface of the turbine blades. The fatigue damage of turbine blades is caused by the tensile stress on its surface layer, and the residual compressive stress of the surface layer can offset part of the tensile stress, so that the fatigue strength of the turbine blade can be improved. Fatigue failure of turbine blades generally starts from the surface, and the surface is in contact with the high-temperature gas environment, which has a great impact on the fatigue strength. Therefore, the use of appropriate surface protection methods to isolate the blade surface from the high-temperature gas environment can improve the high-temperature fatigue strength of the blade. Measures to improve the surface protection of turbine blades to develop a high-temperature coating. Xiao Weiguo said eloquently. (To be continued.) )