AGT100 COMBUSTOR BASIC INFORMATION AND TUTORIALS

What is Allison AGT100 Combustor?

The main features of this combustor, shown schematically in have been described by Rizk and Mongia. It comprises a prechamber in which the fuel is vaporized and mixed with air, a pilot and ignition chamber, and the main cylindrical chamber.

Variable geometry is employed to control the stoichiometry in the primary zone. The prechamber contains a centerbody that houses both the main fuel injector and a pilot nozzle, which is employed only for lightup and acceleration to engine idle speed.

The main fuel is introduced from a manifold surrounding the prechamber, just downstream of the prechamber axial swirler. Uniform filming of the fuel is achieved by spraying it through eight tangential holes onto the etched surface of the prechamber.

The swirling air assists in the prefilming process. The high temperatures of the inlet air and the prechamber walls combine to promote rapid vaporization of the fuel within the prechamber.

At power modes higher than idle, additional air is admitted into the prechamber through a radial swirler to merge and mix with the air flowing through the axial swirler.

Engine lightup is initiated in a small pilot chamber located on the side of the main combustion chamber. This piloting device also serves as a sustainer source when the combustor is operating at low inlet air temperatures or at conditions that lie outside the normal lean blowout limits.

The swirling vaporized fuel–air mixture flows into the main chamber through a round opening in the center of the dome. At high-power settings, additional air is injected into the main chamber through eight holes that are drilled in a manner designed to impart a swirling motion to the flowing air.

Four simple rectangular dilution holes were chosen to ease fabrication of the ceramic liner. Variable geometry, in the form of sliding bands, is used to vary and control the flow areas of the dilution holes and the radial swirler in the prechamber.

At low-power modes, most of the air flows through the dilution holes. As the fuel flow rate is increased above idle, the variable geometry is moved to increase the airflow through the radial swirler and to reduce, by a corresponding amount, the airflow through the dilution holes.

The use of variable geometry enabled the AGT100 combustor to meet the program goals of 5.0 and 37 g/kg fuel for NOx and CO, respectively. Moreover, the experimental data acquired in the course of this investigation was used by Rizk and Mongia to develop a model for calculating NOx formation in
LPP combustors.

This model takes into account the effects of pressure, residence time, and air distribution between different combustion zones. It also provides useful insight into the contribution of the pilot chamber to the total NOx emissions.