The 20 to learn F22 vector nozzle, high performance titanium alloy and ceramic.
tengxunjunshi· 2016-05-29 14:03:19
Author: Hou Jian
in supersonic speed state, the aircraft has a 38-50% or even higher proportion of resistance from the tail of the aircraft. To the rear fuselage aerodynamic shape on drag reduction, greatly reduce the resistance of the supersonic cruise flight, F22 using with the integration of the entire design of binary vector thrust system, and acquired resistance and excellent effect of stealth.
binary vector thrust of F22 reduced the effect of drag from two aspects, the first is idiomatic Russian aircraft of axisymmetric vectoring exhaust nozzle can also do it. Aircraft into the supersonic state in the future, with the increase of aerodynamic center after the shift and drag, horizontal tail gas dynamic surface will control resistance increase, the ability to control decreased and a series of problems. Thrust vector through the sharing of horizontal tail, greatly reducing the deflection amplitude of the tail, F22 in maintaining the balance of supersonic flight can greatly reduce the control of resistance.
F22 body drag fighter design insurmountable peak < so far and the second effect is unique to F22: F22 fuselage with a pointed at both ends of the supersonic airfoil section, the side of the fuselage shape is a huge supersonic wing, forming very low resistance of supersonic lift body configuration; and the how to tail pointed, the entire design performance index has a crucial influence. Using two thrust vectoring nozzle, the F22 tail will smooth the cross-sectional area is reduced to the minimum. < therefore used F22 binary vector thrust, seemingly bulky lot and thrust loss of a large number, than the axisymmetric nozzle and super maneuver control ability is deficient in; but it improved fighter overall resistance and signal features, actually get performance gains is axis symmetry nozzle can not be compared.
picture: F15S/MTD. After the first facelift binary vector nozzle and axisymmetric vectoring exhaust nozzle performance comparison test, Russia the thrust vector stuff, all Americans WanNI < since resistance and stealth advantage so obvious, why Sino Russian aircraft do not use? The answer is one: do not make that level. Four generations of machines due to emphasize the Super Tour, the characteristics of jet engines are double high, high temperature, high speed; the circular cross-section of axis symmetry nozzle stress not only the uniform, and subjected to thermal load and mechanical load is small. The square section will inevitably suffer from the heat, the force of a high degree of uneven, there is no light and high strength and high temperature resistant materials, can not deal with such a harsh working environment. Class= img_box "
to F22 as an example, the structure of the nozzle force of titanium alloy material is specially developed. Before the F22, titanium alloy limit working temperature from 350 degrees has been elevated to 600 degrees, but are unable to overcome high temperature combustion (titanium chemical properties at high temperatures is very active, so-called high temperature is relative aluminum alloy) problem. And the F22 alloy C high temperature resistant titanium alloy (grade Tidyne 3515, the basic composition of 50% titanium, 35% vanadium, 15% chromium) in laser ignition test, ignition point than the third generation fighter with the conventional titanium alloy higher than 500 degrees.
picture: not material and engineering ability also catch not on Americans. Results out of the binary vector nozzle cannot hold the volume and weight, the tiger painting dogs < China and Russia, in the alloy C series alloy public information based on the developed similar performance of resistance burning titanium alloy, such as the Chinese version of the alloy C is called Ti40. However, due to the basic work is not solid - such as the principle of the study of titanium alloy is not deep enough system, the domestic application in the TI40 has not reached the level of practical. According to open in 2014 Journal of aeronautical materials, our country will Ti40 first application in the lower working temperature of the engine compressor casing, until after the model of success and then gradually extended application to other parts, obviously this only is turbofan 15 the.
j-20 now with or no thrust vectoring nozzle AL31 engine < on the other hand alloy C series alloy itself, also cannot resist directly impact ablation of motive gas, so it needs to a thermal barrier to isolate the gas. The United States is based on silicon carbide fiber as the basis of the development of composite ceramic materials, in order to obtain high temperature, high strength, high toughness and impact resistance. And in this regard, China and the United States compared to the larger gap -- burn resistant titanium alloy at least made out, OK with two; and silicon carbide toughened ceramics, at least high performance silicon carbide fiber in our country currently rely heavily on imports and by the international community the embargo.