Flame pipes

The combustion chamber – is the main element of a gas turbine unit. Creation of a low-emission combustion process inside the combustion chamber is the main issue addressed by gas turbine engine developers. It is the reliability and durability of combustion chamber elements that determine the resource and main characteristics of the entire plant

One of the most important components of tubular-ring combustion chambers is the flame tube.

This element operates under extremely severe conditions of elevated temperatures (up to 1000°C).

It is in the flame tube that the large temperature differences during start-up or change of operation of the turbine are concentrated. This contributes to the presence of thermal stresses in the flame tube components. Therefore, in many cases, the life cycle of the flame tubes determines the life cycle of the combustion chamber as a whole.

In order to ensure the required flame tube life, a number of design solutions are used:

1. application of heat-resistant materials for manufacturing;
2. connection of elements with low stiffness to compensate for various thermal expansions (pos. 8 Figure 1);
3. modification of elements in places of maximum concentration of temperature stresses.

Fig. 1. Main elements of a single-section combustion chamber compartment of a Gas Turbine Unit

Fig. 1 shows a single section combustion chamber compartment of a Gas Turbine Plant.

The main elements are flame tube (3),  burner elements (1,2), casing (5)..

Basic principles of fuel combustion in the combustion chamber.

ТFuel and oxidizer (air) are fed to the burner. The ignition of the fuel-air mixture and its combustion in the primary zone (10) takes place by means of the igniter. To ignite the tubular-ring combustion chamber, flame by-passes (9) are installed on the flame tube.

The flame temperature inside the flame tube reaches 1000°C. In order to avoid burning of the wall, convective cooling process is realized. The channel formed by the casing (5) and the wall of the flame tube (3) is supplied with air taken between the compressor stages.  In addition to the channel, the air enters the dilution holes (6), which helps to reduce the temperature of the exhaust gases and allows to regulate the temperature field at the outlet. For connection to the gas collector, an adapter element with a sealing ring (7) is used.

Emission limits have forced developers to move toward reducing fuel consumption during combustion. This approach complicates the process of flame tube cooling.

The main direction of improvement of flame tube designs is the use of more efficient cooling systems.