TY - JOUR
T1 - Droplet combustion behavior of oxidatively degraded methyl laurate and methyl oleate in microgravity
AU - Ando, Shion
AU - Wu, Yuxiang
AU - Nakaya, Shinji
AU - Tsue, Mitsuhiro
N1 - Funding Information:
The authors are pleased to acknowledge the support of the Ministry of Education, Science, Sports and Culture, Grant in aid for Scientific Research (B), 16H04586, 2016 and 19H02341, 2019.
Publisher Copyright:
© 2020
PY - 2020/4
Y1 - 2020/4
N2 - Droplet combustion behavior of degraded and non-degraded fatty acid methyl ester (FAME) were studied under microgravity condition. Accelerated oxidation tests were conducted for methyl laurate (LME) and methyl oleate (OME) as representatives of FAME, and the changes in viscosities and compositions were evaluated. The Rancimat method was employed for oxidizing fuels at 100 °C for 6 or 24 h. The viscosities and compositions were measured with an Ubbelohde viscometer and a gas chromatography-mass spectrometer (GC–MS), respectively. Results showed that various oxidation products were formed only for OME during the oxidation test, and the amounts increased with an increase in the oxidation time. In addition, viscosities of degraded OME were higher than those of non-degraded OME, which would be attributable to the formation of oxidation products. Subsequently, the droplet combustion experiment was performed at 0.1 MPa, 750 °C in CO2-rich atmosphere under microgravity. Droplet combustion behavior was analyzed in terms of evolutions of droplet diameter squared and the instantaneous burning rate. As a result, the instantaneous burning rate of LME maintained almost constant during its combustion period as well as n-decane, which indicates that the behavior of instantaneous burning rate was not influenced by the difference in fuel properties between hydrocarbon and unsaturated FAME. In contrast, the droplet of degraded OME exhibited puffing during the evaporation and combustion periods. This indicates that oxidation products with various volatilities were formed in the degraded fuels, which resulted in puffing. As oxidation proceeded, the release rate of liquid and vapor by puffing decreased owing to the increased viscosity, which causes puffing more frequently. Furthermore, the time of bubble formation increased with an increase in the initial droplet diameter owing to an increase of the heat capacity of the droplet. On the contrary, the time of bubble formation did not vary drastically with the oxidation time, which was probably owing to a limited change in the heat capacity during the oxidation test. This study addresses the droplet burning behavior of LMEs and OMEs with an emphasis on the effects of oxidation.
AB - Droplet combustion behavior of degraded and non-degraded fatty acid methyl ester (FAME) were studied under microgravity condition. Accelerated oxidation tests were conducted for methyl laurate (LME) and methyl oleate (OME) as representatives of FAME, and the changes in viscosities and compositions were evaluated. The Rancimat method was employed for oxidizing fuels at 100 °C for 6 or 24 h. The viscosities and compositions were measured with an Ubbelohde viscometer and a gas chromatography-mass spectrometer (GC–MS), respectively. Results showed that various oxidation products were formed only for OME during the oxidation test, and the amounts increased with an increase in the oxidation time. In addition, viscosities of degraded OME were higher than those of non-degraded OME, which would be attributable to the formation of oxidation products. Subsequently, the droplet combustion experiment was performed at 0.1 MPa, 750 °C in CO2-rich atmosphere under microgravity. Droplet combustion behavior was analyzed in terms of evolutions of droplet diameter squared and the instantaneous burning rate. As a result, the instantaneous burning rate of LME maintained almost constant during its combustion period as well as n-decane, which indicates that the behavior of instantaneous burning rate was not influenced by the difference in fuel properties between hydrocarbon and unsaturated FAME. In contrast, the droplet of degraded OME exhibited puffing during the evaporation and combustion periods. This indicates that oxidation products with various volatilities were formed in the degraded fuels, which resulted in puffing. As oxidation proceeded, the release rate of liquid and vapor by puffing decreased owing to the increased viscosity, which causes puffing more frequently. Furthermore, the time of bubble formation increased with an increase in the initial droplet diameter owing to an increase of the heat capacity of the droplet. On the contrary, the time of bubble formation did not vary drastically with the oxidation time, which was probably owing to a limited change in the heat capacity during the oxidation test. This study addresses the droplet burning behavior of LMEs and OMEs with an emphasis on the effects of oxidation.
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U2 - 10.1016/j.combustflame.2019.12.042
DO - 10.1016/j.combustflame.2019.12.042
M3 - Article
AN - SCOPUS:85077654896
VL - 214
SP - 199
EP - 210
JO - Combustion and Flame
JF - Combustion and Flame
SN - 0010-2180
ER -