If you want to use this technology in a small aircraft, unless you use a small fan engine as a power, such as the one used in the Global Hawk drone being developed in the United States, it would be nice," Alice added, "and a small turbofan engine design like this can also avoid problems with the engine blades." Theoretically, this design is relatively safe. ”

"Let's talk about that kind of model with a turbofan engine later," Zhang Lan smiled bitterly.

The two little girls were in a hurry. It seems that in "Terminator 3" ~ a "Predator" drone prototype, capable of carrying eight missiles, and the drone that has been modified by T-X with internal programs, is to use three small turbofan engines, but in fact, three engines are a bit wasteful, in fact, only the ~ turbofan engine equipped on the wing is enough, and the engine in the tail is actually completely unnecessary.

Suddenly thinking of a possibility, Zhang Lan asked, "What if you don't use a turboprop engine, but a propeller fan engine?" What about feasibility? The blades of a fan engine are much shorter than those of a turboprop engine, and they seem to be more efficient. ”

Compared with the three propellers of the V-"Osprey" tiltrotor that can be used as both turboprop and helicopter rotors, the propellers used on the top of the propeller engine are indeed much shorter, and of course, the number of propellers used on the propeller fan engine is much larger than that of the V-"Osprey" tiltrotor aircraft.

"Paddle fan engine?" Xiao Xi and Alice glanced at each other, "What are you talking about, the D-propeller fan engine and the matching SV-double-row counter-rotating propeller fan used on the An-70 wide-body short-take-off and landing medium-sized military transport aircraft that Russia and Ukraine have just begun to study?" ”

The so-called propeller fan engine can also be called an unducted turbofan engine. It can be seen as a turboprop engine with advanced high-speed propellers with blades, and an ultra-high bypass ratio turbofan engine with the outer duct removed, but unlike the turbofan engine, the propeller engine replaces the multi-layered multi-stage blades of the turbofan engine in the duct with a single or double row of swept blades with a wide chord, thin-blade type exposed in the field.

The propeller fan engine has just come out and has received wide attention from the international aviation community, this combination of turboprop engine low fuel consumption rate and turbofan engine high flight speed dual advantages of the aero engine, its effective bypass ratio reached an astonishing 25 ~ 60, far more than the existing turbofan engine - if it is not limited by the congenital lack of propellers, the aircraft carrying this thing, under the same conditions, can fly faster than the aircraft equipped with the turbofan engine!

Among them, the advanced wide-chord, := vane-shaped swept high-speed propeller is a unique key component of this propeller engine, which has multiple wide-chord, thin-blade swept propellers, which can maintain high efficiency at higher flight speeds than traditional turboprop engines. This type of ground propeller consisting of multiple wide-stringed, thin-bladed swept propellers - so let's call it - can be single-rowed, but equally double-rowed.

Different from the single, the double-row propeller often adopts the reverse rotation design, that is, assuming that if the blades of the front propeller rotate in a clockwise direction, then the blades of the rear propeller rotate in a counterclockwise direction, so that the rear propeller can straighten the swirl flow at the outlet of the front propeller, thereby improving the work efficiency of the propeller.

The An-70 wide-body short-range take-off and landing medium-sized military transport plane, which is currently under development, uses a double-row counter-rotating propeller engine for the D-propeller engine used on it.

It is equipped with a propeller engine that combines the dual characteristics of a turboprop engine and a turbofan engine. It can reduce the fuel consumption of aircraft with turbofan engines by 20 to 30 percent. It can also fly at a speed close to that of an aircraft equipped with an afterburner-free turbofan engine. i.e. flight at high subsonic speeds.

Military transport planes use ground-free turbofan engines to cruise at speeds of about 800 to 900 kilometers per hour. The cruising speed of the aircraft equipped with a paddle fan engine can reach 750 kilometers per hour. This speed is quite close to the ground speed of a turbofan engine. If the aircraft is equipped with a paddle fan engine, the aircraft type and wing design are good enough. Its speed is comparable to that of an aircraft equipped with an afterburnerless turbofan engine.

This speed is also close to or reaches the ground limit that a turboprop engine can reach. However, its fuel consumption is only 70 to 100 percent of that of a turbofan engine. Comparable to turboprop engines. Even the most advanced ground turbines cannot be compared.

Both in terms of cost-effectiveness ratio and usage. Propeller engines are the best alternative to turboprop engines. At the same time, it is also a choice of high subsonic aero engine with extremely high efficiency ratio.

It's just a pity ~, so far, the technology of the new branch of the turbofan engine is still not mature enough, even the United States, which claims to be the most developed country in aviation science and technology, has already begun to develop the propeller fan engine, but so far, it still has not mastered the key manufacturing technology of the propeller fan engine and the propeller fan engine ~ row to the rotary propeller fan, and the research on this technology is still in the laboratory test stage.

At present, only Ukraine and Russia can master this technology. Well, of course, at present, the mastery of this technology by the Ukrainian and Russian teams is not very good, the key reason is that when this technology is about to succeed, the damn Soviet government has collapsed, and more than a dozen union republics have taken a share of the Soviet Union's family funds, plus the robbery of people from outside, the loss of a large number of researchers and the loss of research materials, resulting in this completely new type of engine, which was originally close to success, so far, cough cough, it is still in a state close to success.

"That's it," Zhang Lan nodded, "Do you think it's feasible?" ”

"The engine?" Chenxi thought for a moment and nodded, "Well, that engine is indeed much more efficient than a turboprop engine, and as you said, the length of the propeller's blades is also greatly shortened, and the choice of using this engine and propellers as an engine similar to the V-that kind of tiltrotor is indeed very good, much higher than the efficiency and speed of the turboprop engine used on the V-." This is quite feasible. ”,

"However, then we need to develop a new paddle fan engine," Alice added, with a look of emotion on her beautiful little face, like a modern construction machinery designer seeing a hoe that has been excavated by archaeology for thousands of years, "The paddle fan engine, what an ancient thing, the performance is not bad, but the noise of this thing is really loud." ”

This is true, the speed of the blades of the propeller engine for the propeller engine far exceeds the speed of the propeller of the turboprop engine, so its noise is also louder than that of the turboprop engine, which is a real headache.

"Instead of being so troublesome, it is better to directly develop an ultra-high bypass ratio propeller fan engine with a duct and directly install the propeller fan into the duct. What do you guys think? Zhang Lan is a little unwilling, in his memory, it seems that Russia has come up with a paddle fan engine with an outer duct HK-93, well, I just don't know if it has succeeded, it seems to be just a technical verification engine.

"Oh, although the noise of the engine's blades is less when it rotates," Xiao Chenxi shook his head with a smile, "but with an outer duct, the whole engine is not only much larger, but also much heavier. ”

When listening to Xiao Chenxi, Zhang Lan thought about it, and Khan: Isn't it! Think about the An-wide-body short-take-off and landing medium-sized military transport plane being developed by Lao Maozi and Ukraine, and the volume of Lao Maozi's HK-93 engine with an outer duct has added an outer duct to the paddle fan, although it has effectively reduced the problem of high noise of the paddle fan under high-speed operation, and although the weight is not as large as that of a turbofan engine of the same power, the volume is much larger than that of a turbofan engine of the same power. This is not very obvious in large aircraft, but if it is applied to a tiltrotor similar to the V-, the impact is much greater, in order to reduce such a little noise, add so much extra weight and volume, no matter how it is worth it, let alone how to install it is a problem.

"It's really not worth it." Thinking so, Zhang Lan nodded approvingly and asked Alice, "There should be no problem in developing such an aero engine, right?" Do you want to ask Brother Tian for help? ”

Although I think that there will be basically no big ~ problem, Zhang Lan is not very sure, after all, Alice also said that this is already a very old thing for them.

"Of course there's no problem with something as simple as that," before Alice could speak, the room suddenly heard the sound of Brother Pillar's trademark urn, "We'll be able to handle it, we don't have to go to Megatron." ”