| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系 === 81 === The fuel droplets spout from injector nozzle contains several
different sizes of diamete, and the life time of these droplets
is an important factor in combustion chamber and sprayer design
. Therefore , it is an important study to understand the
vaporization / combustion situation of a single fuel droplet in
a high temperature and oxidizing environment with external
flow. Especially , the study of droplet ignition plays an
important role to understand the droplet combustion phenomena.
In a real fuel spray combustor , the combustion of fuel
droplets occure in a convective , high temperature , oxidizing
environment and the relative motion of neighboring air turns
the problems into two dimensional or more . Due to the complex
chemical reaction and fluid interaction with combustion , the
droplet combustion becomes an extremely difficult phenomenon to
solve . This research of simple ignition model is to understand
the effects of the fuel droplets and of the external
environment on the ignition delay . Threeply - period concept
is introduced to interpret the dominant factors that govern the
ignition process . Numerical technique is applied to get an
insight of transient behavior of a fuel droplet to ignition . A
special hybird numerical scheme ICED-ALE is used to circumvent
the difficulties arising from the rapid transition of ignition
and regression offuel droplet . The results indicated the
droplet in smaller dimension is easier to be be ignited in most
cases . But in higher temperature enviroment , the dimension of
fuel droplet affects the delay times less .At enviroment
temperature of 1050 k , the ignition delay time difference
between large and small fuel droplet is 7.7% . Basically , it
saves 34.6% time for fuel droplet ignition in convective
enviroment than one in stagnant which coincides the real
physical situation .
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