Page 50 - The Jet Engine

Combustion chambers

Fig. 4-7 Multiple combustion chambers.

Tubo-annular combustion chamber 20. The main advantage of the annular chamber is
18. The tubo-annular combustion chamber bridges that, for the same power output, the length of the
the evolutionary gap between the multiple and chamber is only 75 per cent of that of a tubo-annular
annular types. A number of flame tubes are fitted system of the same diameter, resulting in consider-
inside a common air casing (fig. 4-8). The airflow is able saving of weight and production cost. Another
advantage is the elimination of combustion
similar to that already described. This arrangement propagation problems from chamber to chamber.
combines the ease of overhaul and testing of the
multiple system with the compactness of the annular 21. In comparison with a tubo-annular combustion
system. system, the wall area of a comparable annular
chamber is much less; consequently the amount of
Annular combustion chamber cooling air required to prevent the burning of the
19. This type of combustion chamber consists of a flame tube wall is less, by approximately 15 per cent,
single flame tube, completely annular in form, which This reduction in cooling air raises the combustion
is contained in an inner and outer casing (fig. 4-9). efficiency (para. 27) to virtually eliminate unburnt
The airflow through the flame tube is similar to that fuel, and oxidizes the carbon monoxide to non-toxic
carbon dioxide, thus reducing air pollution.
already described, the chamber being open at the
front to the compressor and at the rear to the turbine 22. The introduction of the air spray type fuel spray
nozzles. nozzle (Part 10) to this type of combustion chamber

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