XI Международная студенческая научная конференция Студенческий научный форум - 2019

One of the most important aspects of the modern military aviation of the Russian Federation is the engine. The contemporary aircraft are predominately powered with air-breathing engines. In its turn, one of essential components of the aviation gas-turbine engine is a combustion chamber. It is sometimes called a "flaming hearth" of the engine.

A combustion chamber is designed to provide heat for the working fluid (air), to increase its kinetic energy by burning the fuel, stored on board, with oxidizer (oxygen) from the air. A combustion chamber is a part of all types of air-breathing engines, both of direct and indirect action. In this connection the actuality of research into increasing the combustor quality and performance is of utmost importance.

Combustion chambers can be divided into two groups:

- main combustion chambers, incorporated into the core of the engine, which includes a compressor (in case of two- or three-stage engines – high-pressure compressor), a combustion chamber and a gas turbine;

-afterburners, designed for additional thrust acceleration by burning large quantities of fuel, located before the exhaust nozzle of the engine.

Main combustion chambers can be classified as annular combustion chamber, tubular combustion chamber and cannular combustion chamber.

The main combustor parameters are:

completeness of fuel combustion;

excess air ratio;

full pressure recovery ratio.

The current combustor development trends include increasing gas temperature behind the combustion chamber, increasing the completeness of fuel combustion and normalizing temperature range distribution.

It is necessary to consider more closely every aspect.

Gas temperature increase is limited due to several reasons. The most important factors are limitation according to the strength properties of the combustion chamber and the chemical composition of the fuel. Unfortunately for modern science it is rather difficult to create the materials, which would be able to withstand higher temperatures than those, which exist today, despite the fact that the stress is very high. For example, the gas temperature behind the combustion chamber in some modern engines can reach 2200 degrees K and even more. The problem with fuel can be solved, but there is a problem with financing, as aircraft engines consume a huge amount of fuel. For example, an American reconnaissance aircraft SR 71, weighing empty 24 tons, consumes 46 tons of fuel every 5 flight hours, even with a specially developed for this aircraft type of fuel J8.

The completeness of fuel combustion depends both on the combustion chamber shaping and on fuel composition. The main problem is that trying to reach maximum possible completeness of fuel combustion by means of reshaping the problems can arise, leading to the deterioration of other combustion chamber parameters.

Normalizing temperature range distribution completely depends on the combustion chamber shape and on the condition of the inlet airflow. In order to gain high performances, engineers have to make difficult calculations while designing even the tiniest components.

What is more, another important task is to increase the ecological compatibility of combustion chambers. It is very important, because unlike civil aviation, military aviation has rather low requirements to the ecological aspect. Taking into consideration great fuel consumption and flight occurrence, this can have grave consequences for the environment.

To sum up, the combustion chamber is one of the most important components of the aircraft engine, and its optimization and increasing its performances are very important tasks for the modern aviation designers.