On the Formation of Nitrogen Oxides During the Combustion of ...

3.1 Droplet Combustion Facility
The combustion chamber is installed on the fourth platform of the DCU
(Fig. 3.2, E) and has inner dimensions of (140×50×54) mm 3 (W×D×H). Its
temperature is precisely controlled by a K-type thermocouple that is attached
to the inner combustion chamber wall and by heating cartridges that are integrated
into the combustion chamber housing. Two further thermocouples
(S-type) measure the gas temperature inside the combustion chamber. Apart
from these thermal aspects, the combustion chamber also houses four symmetrically
aligned sample probes for exhaust gas sampling [208, 293, 294, 296].
The combustion chamber is designed in line with the following operational
specification:
• Facilitate fast heat-up periods starting from an ambient temperature
level (within 45 to 60 min)
• Maintain preheating temperature at set-point of e.g. 500±1K
• Exchange air/exhaust from inside the combustion chamber within 15s
• Restore set-point temperature within 40s after an air exchange
• Facilitate execution of nominal experiment sequence including the insertion
of the droplet array holder and the exhaust gas collection through
the exhaust gas sampling system (see also Chap. 3.2.6)
• Operate combustion chamber shutter (open/close position) in accordance
with the experiment sequence
• Minimize heat loss of combustion chamber induced by the insertion of
the cold droplet array holder (steel frame)
In particular the shutter design (Fig. 3.8) must not counteract the thermal insulation
and airtightness of the combustion chamber. The latter requirement
is essential for the flushing sequence at the end of a combustion run, which
is subdivided into a complete evacuation and a succeeding refilling with fresh
air. A leak at the shutter sealing might cause a major interference with the
global pressure regulation of the DCU.
By lifting the droplet array into the combustion chamber, a little air gap of
1mm on average remains between the combustion chamber opening (Fig. 3.8,
D) and the steel frame of the droplet array holder inserted. This gap must
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