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

3 Experiments on Droplet Array Combustion
ticles eventually stagnate and accumulate in soot shells [76, 78, 235, 394]. Xu
et al. [465, 467] report in detail on the effects and interaction of soot formation,
aggregation, and oxidation under microgravity conditions.
As far as this study is concerned, the representativeness of the collected exhaust
gas samples was a major issue for the interpretation of the experimental
results. Thus, a great effort was put into a sophisticated design as well as into
the operational procedures. Concerning the technical implementation of the
measurement techniques and operational procedures, full access by remote
control needed to be ensured apart from the standard “hard line” access. For
the drop tower environment, remote access to the drop capsule was secured
by the Capsule Control System (CCS), the switchable power supply PDU, and
the radio telemetry/telecommand system with a WLAN transmitter unit [104].
During the sounding rocket flight, a more elaborate telemetry/telecommand
system was used to communicate with the experiment module. It was operated
by DLR MORABA and is outlined in detail in Table C.2. EADS Astrium was
in charge of the telemetry/telecommand interface, and a single timer (manufacturer:
Kayser-Threde; type: KM1038) was utilized allowing 24 commands.
Timer events and sequencing commands finally controlled the experiment at
the physical level. Nevertheless, the two respective control rooms with the experiment
operators have to be considered as an extension of the experimental
setup.
From the mechanical point of view, the experimental setup is exposed to microgravity
conditions, on the one hand, but to vibration and high loads during
launch, landing, and touchdown, on the other hand (Figs. C.2 through C.4). In
the case of drop tower experiments, the residual acceleration (microgravity
quality) during the “capsule flight” is in the range of 1×10 −6 to 1×10 −5 of g 0 ,
which are the best achievable values amongst all microgravity facilities. In the
case of sounding rocket experiments, a microgravity quality of 1×10 −4 of g 0
can be achieved for a duration of approximately 6min. Comprehensive information
on the different loads acting on the setup is given in Chapter C.1.
Parabolic flight experiments are an exception to this comparison, as they are
directly operated by the experimentalist. The microgravity quality as well as
external loads remain at a moderate level (see also Chap. B.1) [66, 104].
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