In 1919, Germany transformed the "Pigeon" reconnaissance plane into a passenger plane, which opened the curtain on the vigorous development of civil aviation. Subsequently, civil airliners entered the fast lane of development, and various layout types emerged one after another.
(Pigeon Reconnaissance Aircraft)
In 1958, the Boeing 707 developed by Boeing was officially delivered. The basic configuration of civil airliners has not changed significantly so far. Swept wings, lower wings, sling engines, and conventional layouts with well-defined boundaries between wings and fuselage have become the common civilian airliners we see today.
(Boeing 707 imported from China)
This layout is suitable for large jets cruising at high subsonic speeds at altitudes of up to 10,000 meters. In the aviation industry, this layout is known as a "tube-wing" layout.
Later, although the civil airliner has made great progress in aviation materials, aero engines, and avionics systems, it basically continues to use the Boeing 707 type in the aerodynamic layout.
Of course, the application of winglets and supercritical airfoils squeezes the last remaining "value" of the "tube-wing" layout. Today, the aerodynamic efficiency potential of the conventional layout can be regarded as "twisting Yangge on the edge of the cliff - the good days are over".
Boeing Airbus mainstream passenger aircraft, it can be seen that the aerodynamic layout type is very different from that of Boeing 707
Especially in today's increasingly serious energy crisis, airlines are eager to have unlimited fuel in the tank and sell tickets in the cabin. This means that "more fuel-efficient" and "more loadable" are the inevitable trends in the development of civil airliners in the future.
In this case, the Blended-Wing-Body (BWB) layout is likely to be the choice of future civil airliners.
The forerunner has become flattened and enlarged
The so-called wing-body fusion layout refers to the lift body layout with a high degree of integration between the wing and the fuselage, that is to say, there is no obvious dividing line between the fuselage and the wing.
This form of layout was proposed by many scholars as early as World War II. However, the complete wing-body fusion layout was first proposed by McDonnell Douglas, the king of passenger aircraft development, in 1988.
From the perspective of time, in general, there are three stages of wing-body fusion layout thinking. The first phase is from 1991 to 2000, the second from 2001 to 2010 and the third from 2010 to today.
In the first stage, McDonnell Douglas was the most concerned and successively proposed two wing-body fusion layout schemes. At this stage, the wing-body fusion layout of the airliner is mainly a large. The plan given by McDonnell is to carry 800 people up. After Boeing acquired McDonnell Douglas, it also took over the pot of wing-body fusion layout. The naturally released satellite is not small, with a planned crew of 450 people.
A typical scheme for the first phase of wing-body fusion layout in the United States
The research of this period was about how to turn the fuselage into a lifting body. The idea at this point was to turn the cylindrical body into a disc-shaped body. This design can reduce resistance by reducing the wetting area.
(Changes in the airframe in the BWB scheme)
While reducing drag, the fuselage in the wing-body fusion layout also bears a part of the lift. This makes the aerodynamic load distribution of the whole machine more uniform, thereby reducing the weight of the whole machine.
(In the literature, the wing-body fusion layout and the conventional layout are compared in terms of lift and aerodynamic loads)
Although in the first stage, the wing-body fusion layout scheme has already demonstrated the advantages over conventional layouts. However, aviation technology at this time could not reduce the aerodynamic noise problem in this layout, so mainstream airliners did not choose this option.
Followers, lower resistance and quieter
In the second stage, both Europe and the United States actively participated in the research of wing-body fusion layout. Among them, NASA's promotion is very important. After 2000, NASA launched the N+2/N+3 program. Benefiting from this program, Boeing has launched a series of design solutions.
At this stage, various research institutions have further increased the wing-body fusion degree of the wing-body fusion layout. The improved wing-body fusion also further reduces the weight of the aircraft structure and improves the lift-to-drag ratio.
Taking the Boeing Sugar Ray scheme as an example, the natural laminar drag reduction technology is used at the leading edge and the small rib drag reduction technology is used in the turbulent region. These technologies ensure that the lift-to-drag ratio of the whole machine is very high.
In the N+3 program promoted by NASA, the engine was embedded in the rear of the fuselage to effectively reduce noise.
Runners, the ranks are getting bigger
In the past 15 years, the research on wing-body fusion layout has entered the third stage. At this stage, the research institutions for this layout are more abundant. Researchers' research on wing-body fusion layouts is also more geared towards engineering applications.
For example, for the hypersonic cruise feature of the future passenger aircraft, Dzyne Technologies has optimized the design. It placed the cargo compartment and fuel tanks at the wing roots instead of under the passenger cabin.
(Ascent1000 Aircraft Proposal from Dzyne Technologies)
The Airbus design not only changed the layout type, but even changed the energy structure of the passenger aircraft. They gave the wing-body fusion layout "ZEROe" using hydrogen energy.
(Airbus ZEROe solution)
Russia, which has been performing unsatisfactorily on passenger planes, also gave its own PPT plan. It is not too late for Russia to study the wing-body fusion layout scheme. Since 1991, the Tupolev Design Bureau, a well-known Russian airliner design bureau, has been studying a number of options. The most famous is the Tu-404 scheme.
(Maozi's BWB plan)
Canada, Germany, the United Kingdom, France and other countries have also carried out the application of wing-body fusion layout in different types of passenger aircraft such as business jets and regional airliners during this period.
Since the beginning of the new century, the mainland has had its own thinking and exploration in the layout of wing-body integration. The most typical solutions are the Sparrow B scheme given by COMAC and the NPU-BWB-300-II scheme given by Northwestern Polytechnical University.
On April 21, 2017, the scaled-down verification aircraft designed according to the Lingque B scheme successfully made its first flight at Zhanghe Airport in Jingmen, Hubei Province.
(Sparrow B Verification Machine)
The scaled verification machine designed by Northwestern Polytechnical University according to the NPU-BWB-300-II scheme has carried out several test flights in 2023, and has successfully verified the overall design, aerodynamic design, flight control and other technologies.
(Northwestern Polytechnical University NPU-BWB-300-II program)
The next generation?
Although more and more civil airliner research institutions are looking at the wing-body fusion layout scheme. However, there are still three major problems that are difficult to solve.
(1) It is relatively difficult to maneuver the aircraft
Compared with the conventional layout, the wing-body fusion layout is more difficult to maneuver in the longitudinal, heading, and lateral directions. Especially when the aircraft is rolling and turning, passengers close to the outside will be subject to greater overload, which will affect the riding experience.
(2) Difficulties in cabin layout
According to the existing wing-body fusion layout scheme, the number of seats in each row is far more than the 7~9 seats in the current wide-body passenger aircraft. This makes it difficult to balance the passenger experience in the cabin, regardless of the layout.
(3) Difficulties in handling emergencies
The wing-body fusion layout has a large number of seats in a single row, and in the event of an emergency, the evacuation of passengers will become a big problem. Although the aforementioned Airbus VELA scheme has been studied for emergency evacuation, compared with the conventional layout, the wing-body fusion layout is difficult to evacuate quickly.
In addition to the above three difficulties, there are many problems to be solved in the wing-body fusion layout, such as noise, structure, operation, and airworthiness.
With the advancement of aviation technology, these problems may be better solved. After all, aviation is a business for human beings to challenge themselves.
So, if one day the wing-body fusion layout is really put into operation, will you choose to ride?