Philip said with a smile: "With the pressure P, volume V, and temperature T, the state of the gas is basically determined, and the overall performance scheme design of the aero engine, that is, to use the relationship between these three quantities in every possible way to induce the air molecules to work more and eat less." But before we can get into the specifics of the overall performance package, there are two most basic questions that need to be addressed: how to inhale and how to eject. For inhalation, if you air molecules don't want to come in, then pull you. ”

One engineer asked, "Shall we take in air through a compressor?" ”

Philip nodded, "That's right! The multi-stage fan of the compressor is an accomplice in abducting air molecules, and they simply trick people into it, knowing that they like the characteristics of big houses. Junior, do you want to own your own house? Do you want to change the pigeon cage into a palace? Then come in and check it out! Through the high-speed rotation of the fan, a large amount of air is thrown backwards, causing fewer and fewer air molecules near the fan, that is, the empty room is unoccupied! So the elements from afar came to improve the housing conditions, but they didn't expect to be thrown into the black factory behind them as cattle and horses. In this way, the inhalation problem is simply solved. ”

Another engineer asked curiously, "But what about jets?" ”

Philip continued: "The jet issue is a bit troublesome to solve. A jet engine must eject high-velocity gas to produce thrust, but this must rely on higher pressure ratio conditions, and the greater the ratio of internal pressure to external pressure, the higher the speed of the jet. However, the internal pressure does not rise out of thin air, and there must be a laborious compression process. In order to increase the pressure inside the engine, a compressor must be used. Under the powerful fan-like fan of compressor blades, the air molecules are forced to go backwards. The compressor flow channel is designed to be high in the front and low in the back, and the blades are shorter than the first, so the further back you go, the more crowded it becomes, and finally the purpose of pressurization is achieved. In fact, from this point of view, the front fan is also a compressor. However, in terms of use, the main business of the fan is to lure air molecules in, and the main compression process is realized by the pressurization stage and high-pressure compressor at the back. ”

Billy thought for a moment and asked, "So where exactly does our overall design start?" ”

Philip earnestly: "The working process of a jet engine is a non-stop cycle of inhalation, compression, combustion, expansion, and jet. Air molecules come from the atmosphere and eventually mix into the atmosphere, which is really dust to dust, earth to earth, and cause and effect cycle. Therefore, the selection of cyclic parameters such as pressure, temperature, and flow rate of each section of the engine and the flow channel is the beginning of the overall scheme design of the jet engine. For example, according to the existing state of art, the efficiency of the compressor designed in the final design is likely to be relatively low, so there is no way to raise the efficiency index of the high-pressure turbine upward, or increase the temperature by ten degrees or twenty degrees. After various trade-offs and balances, the key parameters of the whole working cycle are obtained, such as bypass ratio, total pressure ratio, thrust, fuel consumption rate, high and low shaft speed, as well as the performance parameters of each component, such as flow, temperature, efficiency, pressure ratio, etc. Based on these parameters, it is also possible to continue to calculate the approximate dimensions of the entire flow path of the engine, that is, the preliminary flow channel. With the preliminary runner and the performance indicators that each component needs to achieve, it can finally be sent to various specialties for specific design. ”

Messerschmidt said with emotion: "I didn't expect this jet engine to look simpler than the piston engine structure, but the design is much more complicated, and it is impossible to complete the design of a jet engine without comprehensive theoretical knowledge!" ”

Philip replied, "Yes! In order to ensure that the overall indicators are met, the turbine efficiency is low, and the compressor must be high. The air intake is overbearing, and the parts behind it will be unlucky - at this time, quarrels are inevitable, and the landlord's family has no surplus grain, why is the index for it so low? It's hard for us to be professional! In the process of pressing the seesaw, the designers of the overall scheme must learn to dance with shackles and learn to find balance on the tightrope. ”

After a pause, Philip continued: "In fact, the situation of trembling on the tightrope may not all occur in the index allocation process, and the subsequent design process is unavoidable. For example, the design of the acceleration and deceleration control law of the whole machine after the component design is completed, which is a typical left and right face-slapping work. If the oil is intensified and the force is excessive, the acceleration line will go directly to the surge zone or the over-temperature over-rotation zone, which is likely to cause the turbine to overheat or directly make the compressor gasp. The oil is slowly added, the engine is quite safe, the acceleration time is too long, the plane is about to crash to the ground when the go-around flight and your thrust has not risen yet, even worse! Similarly, when decelerating, the oil is collected too quickly, and the working line plunges into the oil-poor area, and the combustion chamber goes out directly and strikes. Slow it down, the pilot is out again, the runway is so long, I use all the brakes, what do you mean that the thrust has been so big?! ”

Billy smiled wryly: "Then our road in the future is really long and tortuous!" ”

Philip nodded, "That's right! Don't look at me, I'm talking about the Tao. But I'm just theoretically a little bit more than you know. In the end, it's up to you engineers to really rely on. Of course, success always has its twists and turns. It is likely that the individual indicators after the design of the components are indeed not reached, then it should be used to evaluate the performance of the whole aircraft, if the requirements of the aircraft are found to be able to meet after the evaluation, the local substandard can only pinch the nose to recognize, so there will be some margin when doing the overall plan! Do not meet the aircraft requirements after the assessment? Hehe, don't send it if you go! The engine had to be sent to a waste warehouse or an aviation museum. ”

Messerschmidt patted Philip on the shoulder and said, "Philip, you really taught us a vivid lesson!" I think all of you here today, including me, have gained a lot. Hearing you say that, I decided that no matter how difficult this jet engine is, we will make it too! Recently I got the news that our German government is going to set up an aviation department, and I heard that there will be regular aviation competitions, and I think that if our aircraft can win the championship in this competition, the fame will become bigger and bigger, and the future development will be faster and better. ”

Philip was surprised and said, "To set up an aviation department? So fast! I think with turbochargers and torque converters, our M20 transport aircraft can also shine in the competition, right? ”

Messerschmit nodded and said, "Yes, I think the restrictions we are subject to may be slowly relaxed, so it is not impossible to develop fighters in the future!" ”

Philip said to himself: Didn't the German Ministry of Aviation be established only in 1933? It's only the autumn of 1931, so can we say that the history of this time and space has changed? It can't be because I crossed over and caused the butterfly effect, right? So, will World War II happen? And will Hitler be the original Hitler?