DGLR-MTR-2000.PDF

It demonstrated particularly good tolerance to FOD
during the development and qualification tests (sand,
ice, water, …).
Both stages can be easily inspected with boroscopes
in order to monitor the mechanical
condition.
6.2 Combustor
A reverse-flow annular combustor was chosen for its
advantages regarding the whole engine architecture.
Best adapted to the centrifugal compressor design, it
minimises engine length, provides good accessibility
to fuel nozzles and allows a short and rigid generator
rotor.
The combustor [1] can be shortened only provided
rapid fuel conversion is achieved in its primary combustion
zone. Primary zone conversion is controlled
by the fuel mixing and vaporisation subprocesses.
These processes can be precipitated by achieving a
preferably small size of fuel droplet, a high relative
velocity between the drops and the gas, a preferably
homogeneous fuel distribution in the primary zone,
and a high turbulence level conducive to efficient mixing.
Therefore, the fuel conditioning system proved to
be a key criterion.
In order to improve the fuel conditioning system MTU
developed a new type air blast atomiser which is illustrated
in Fig. 3.
Fig. 3 Air blast atomiser
According to this design the fuel is sprayed onto a
venturi insert by means of a pressure atomiser. The
two counter-rotating primary zone vortices concentrates
the burning process in the centre of the primary
zone. The secondary airstream forms a layer on the
flame tube wall. This system prevents contact of the
burning gases with the flame tube walls. Fig. 4 shows
the flame generated by this type of atomiser.