Section b -2A
Most of the surface of B-2A is covered with a special elastic material, which keeps the surface uniform in conductivity and reduces the radar wave reflection at joints or joints. In design, the invisible parts (such as the air inlet) will be coated with radar absorbing material (RAM), and its composition is still highly confidential. RAM is a multi-layer spray coating, which contains components that can convert radar wave energy into heat energy. After the whole machine is coated with a coating with a proper thickness, radar waves reflected from both sides of the coating will interfere with each other and cancel each other after the radar waves with a specific wavelength are irradiated on the coating. A similar concept is the coating of optical lenses, which can eliminate unnecessary light.
2A are sprayed with absorbent material.
Except for the area behind the nozzle, the trailing edge of the B-2 flying wing has nine large control surfaces. The rearmost "beaver tail" is a whole movable control surface, which is used to offset the bumps caused by vertical gusts when flying at low altitude. On the outermost side are a pair of separated airfoils called "speed brake-Rudder". The remaining six aileron surfaces are used for pitch and roll control, and the outermost pair is also used as aileron at low speed. B-2 originally designed a pair of separate flaps under the rear fuselage, but the wind tunnel test showed that the aircraft did not need flaps at all, so the flaps on the first flight test prototype were riveted to death. But the production B-2 still left traces of flaps. The wing area of the plane is large enough that no flaps are needed for take-off and landing.
The "beaver tail" at the tail of B-2 can be used for pitch control. Pay attention to the auxiliary intake valve that opens above the air intake.
"Beaver tail" detail photo
Beating marks left by the back edge of B-2A abdomen
B-2 has no vertical tail, which is different from traditional aircraft. The aircraft is yaw neutral, that is, when B-2 turns left or right, it will not produce centering aerodynamic force. B-2 is controlled by Northrop's patented speed brake rudder at the trailing edge of the outer wing. Speed brake-The rudder can crack up and down, and it can crack at the same time as speed brake. When it cracks asymmetrically, it can be used as a rudder. Because of the boundary layer on the surface of the flying wing, the speed brake-rudder must crack at least 5 degrees to work. Therefore, in normal flight, the speed brake-rudders on both sides are in the open position of 5 degrees, so they can work immediately when they need to be controlled, which is why the speed brake-rudders in the B-2 flight photos we saw are all open. The open speed brake rudder will affect the stealth effect of the aircraft (especially in the backward direction), so when the B-2 arrives in the war zone, the speed brake rudder will be completely closed. It is said that the B-2 relies on the engine thrust difference for yaw control in complete stealth mode.
In normal flight, the speed brake rudders on both sides of B-2 are in the open position of 5 degrees.
B-2 is inherently static and unstable, and it relies on a four-degree wired transmission system to achieve stable flight. General Electric Company has developed the flight control computer unit of this aircraft. Eight actuator remote terminals are installed at the trailing edge of the wing of B-2, and the instructions of ge flight control computer are received through the four-redundancy digital data bus. The remote terminal converts the digital command into an analog signal, so that the actuator can control the wing to deflect to a corresponding angle. The remote terminal is also responsible for controlling all necessary feedback loops. Six groups of air data sensors are installed at the leading edge of the wing in front of the B-2 windshield to provide air data to the wired transmission system, which determines the angle of attack and sideslip of the aircraft according to the air pressure value.
There are three groups of air data sensors (4 in each group) above the nose of B-2A, and there are also three groups below.
There are three groups of air data sensors (four in each group in the white circle) above the nose of B-2A, and a /APQ- 18 1 radome is next to the sensors.
Four ge f118-ge-110 afterburner turbofan engines are installed in the engine compartment on both sides of the central fuselage of the B-2A, each with a rated static thrust of 86 18kg. F 1 18 is developed on the basis of F 10 1-X, and it is a fighter model of B- 1 bomber F10/engine. Compared with F 10 1, f1-x has a smaller low-pressure external bypass cylinder, which reduces the bypass ratio from 2: 1 to 0.87: 1. The engine with low bypass ratio only needs a smaller intake and exhaust system, so it was selected by B-2.
F118-ge-110 afterburner turbofan engine
The air inlet of the engine is far away from the leading edge of the wing to avoid being irradiated by radar waves below. Because the B-2 adopts a thick flying wing structure, the engine can be buried deep in the flying wing, and the flat air inlet and curved air inlet on the upper surface of the flying wing can ensure that the airborne radar cannot directly illuminate the front of the engine from above, let alone from below. In this way, the B-2 can adopt a simpler air inlet, and there is no problem just by modifying the lip with sharp teeth. However, there is another problem with the air intake on the wing. The airflow has to flow through the upper surface of the flying wing for a certain distance before it can enter the air inlet, which aggravates the boundary layer problem. Therefore, the inlet of subsonic B-2 also uses the conventional partition plate to remove the gap, and like the lip of the inlet, it has also been secretly modified.
In the detailed photo of the B-2A air inlet, you can see the serrated lips and the boundary layer suction gap.
The initial wind tunnel test shows that there is some airflow separation in the large arc inlet, which leads to thrust loss at low speed. In order to solve this problem, four diamond engine auxiliary intake valves are installed on both sides above the air intake.
From this point of view, the exhaust pipe of B-2 is also S-shaped.
The boundary layer airflow separated by the boundary layer separation plate of B-2 inlet is mixed into the tail nozzle to reduce the exhaust temperature and infrared radiation. The airflow passing through the partition also expands and is guided to various internal airflow pipes, which are collectively called secondary airflow systems. This includes ventilation of accessory transmission and engine compartment installed on engine block, ram cooling airflow of heat exchanger of environmental control system and airflow of bypass circuit. When working at low speed on the ground, the air flow of the engine is increased through four diamond-shaped engine auxiliary intake valves, which are located at the top of the intake hood and in front of each engine intake. The operation when the auxiliary intake valve is opened reduces the mass flow ratio of the main intake and the corresponding sharp lip rotation loss. The total pressure recovery of the engine is improved, and the pressure distortion level of the inlet is reduced at the same time, thus improving the low-altitude flight state, especially the performance at takeoff.
B-2 engine and intake/exhaust pipe system, it can be seen that in order to reduce the exhaust temperature, a large amount of cold air is introduced by the boundary layer absorption notch of the intake port.
The design of engine tail nozzle system is also a big challenge. The tail nozzle of B-2A needs to minimize the infrared signal characteristics, which makes it difficult for the enemy infrared detection system to find the aircraft. The long-range infrared search and tracking system of some fighters and the guidance head of infrared guided missiles can detect the thermal radiation of hot gas and water vapor emitted by the engine, and B-2 needs quite a few measures to reduce the infrared characteristics. One of them is to reduce the exhaust temperature as quickly and effectively as possible. The engine nozzle of B-2 aircraft is located at the gap between the three serrated protrusions on the trailing edge of the wing, and is covered by the lower surface of the wing within a certain distance, thus reducing the heat of the engine nozzle and reducing the chance of being discovered by the enemy infrared detection device. The engine nozzle goes deep into the wing and is honeycomb-shaped, so radar waves can't enter. In addition, the engine assembly is also equipped with an airflow mixer, which can guide the cold air flowing through the airfoil into the engine and continuously reduce the outer temperature of the engine. The nozzle is wide and flat, so people can't see the nozzle at the tail of the plane. Especially the nozzle temperature adjustment technology greatly reduces the infrared exposure signal of the nozzle. In addition, due to the interaction between the jet and the airflow passing through the upper surface of the wing, vortices can be formed on both sides of the tail nozzle, further reducing the exhaust temperature.
When B-2 flies at high subsonic speed, the airflow on the upper surface of the wing has reached supersonic speed.
The four-wheeled main landing gear is installed on both sides of the engine compartment and retracted forward into the wing. The huge serrated edge landing gear door can act as a vertical stabilizer during take-off and landing. The two-wheel nose landing gear is retracted backward under the nose.
B-2' s thick nose gear
The fuel tank occupies most of the space inside the outer wing part. Two large bomb compartments are arranged side by side under the fuselage between the engine compartments. Each bomb bay can be equipped with an advanced rotary pylon developed by Boeing, eight 908kg ammunition, and two bomb rack components can be installed to mount conventional ammunition.
The rear central fuselage made by Boeing Company contains two large bomb bays.
Advanced rotary pylon developed by Boeing Company.
B-2 mountable weapon
In the process of repairing B-2 stealth coating, the coating is toxic. The daily coating maintenance of B-2 is quite complicated.