Simulating Thermal State of High-Temperature Ceramic Samples

Developing high-velocity atmospheric aircraft equipped with ramjet engines, which use atmospheric air as the oxidizer, is an important component of aerospace technology prospects. These craft may be employed to quickly deliver payloads over intercontinental distances and as boosters for spacecraft injection into orbit. A characteristic feature of high-velocity atmospheric aircraft is a presence of sharp aerofoil edges subjected to highly oxidative airflow. This means that actual implementation of numerous hypersonic atmospheric aircraft projects largely depends on whether it is possible to develop materials that could remain stable in an oxidative atmosphere at temperatures of 2000--2500 °C. We estimated the thermal state of a structural component in the shape of a blunted wedge made out of promising refractory ceramics under flight conditions at an altitude of 22 km and a velocity of Mach 7

Применение вспомогательных топлив для управления сверхзвуковыми потоками реагирующих топливно-воздушных смесей в канале камеры сгорания

Besides gas-dynamic methods, chemical ones are also suitable for the implementation of stable supersonic combustion of hydrocarbon fuels. Organoelemental compounds are known for their high reactivity, so attention was paid to organosilicon liquid during the research on the experimental model. The obtained estimates of the laminar flame speed in a mixture of vapors of this liquid with air were 0.72-0.8 m/s, which is higher than that of ethylene successfully used in supersonic combustion tests. The tested compound can be considered as a candidate for supplementary fuel to control the supersonic reactive flows in the combustion chambers of ramjet engines.

ОСОБЕННОСТИ РАСЧЕТА И РЕГУЛИРОВАНИЯ ДВУХКОНТУРНОГО ТУРБОРЕАКТИВНОГО ДВИГАТЕЛЯ С ФОРСАЖНОЙ КАМЕРОЙ СГОРАНИЯ В НАРУЖНОМ КОНТУРЕ НА ПРЯМОТОЧНЫХ РЕЖИМАХ РАБОТЫ

A promising direction in aviation is the creation of anaircraft for supersonic cruise speeds (Mach 3...4). It is known that ramjet engines are more preferable for Mach numbers larger 3. However, they do not have starting thrust and uneconomical at subsonic flight speeds. At the same time, at subsonic flight speeds, turbofan engines are the most expedient. The combination of the positive properties of turbofan engines at subsonic speeds and a ramjet engines at supersonic speeds is possible by using duct-burning turbofan engine, which can operate at the ramjet mode with the blocked gas turbine duct at supersonic flight conditions. At this mode, duct-burning turbofan engine turns into ramjet engine, which, however, has special features due to the presence of fan in front of the combustion chamber, which operates in turbine mode or in zero power mode and also because of the outlet jet, which has annular shape, flows out from the duct causes the appearance of bottom drag. The presence of bottom drag requires both the development of a mathematical model for its calculation and taking into account its influence on the choice of the control law for the nozzle outlet area. The article presents a mathematical model of the working process of duct-burning turbofan engine at ramjet mode, taking into account the presence of fan in the flow path and bottom drug. Using the developed mathematical model, the regularities of changes in the internal and effective thrust, as well as the specific fuel consumption, depending on the relative fuel consumption and the critical section of the nozzle at a given altitude and flight speed are established. The critical section of the nozzle is the main regulating factor, and the relative fuel consumption is related to the main regulating factor - the fuel consumption. These patterns are useful for choosing a control program.There is such a combination of regulating factors whichprovides two extremes in the regularities of trust and specific fuel consumption changes: the mode of minimum specific fuel consumption and the mode of maximum thrust. In addition, the influence of gas underexpansion in the nozzle on the thrust-economic parameters of the engine and the required area of the nozzle outlet section were estimated. The obtained regularities are advisable to use when engine control program is chosen.

Oxygen–Methane Torch Ignition System for Aerospace Applications

A new ignition system, based on a CH4/O2 torch has been developed by the Chemical Propulsion Laboratory of the University of Brasilia. Designed to ignite a hybrid rocket, this device has been improved to be used in testing of solid and liquid ramjet engines under development in our lab. The capability to provide multiple ignitions and to cool-down its combustion chamber walls by using a swirled injection of the oxidizer, along with a very low weight to power ratio, makes this device versatile. The igniter is controlled by a feedback system, developed by our group, which guarantees the possibility of operating in different design conditions enabling, therefore, complete integration with systems of different nature. The main characteristics of the igniter and the design solutions are presented including some considerations about the tests performed to evaluate the quality and performance of the ignition system.