TY - JOUR
T1 - Flame image velocimetry analysis of reacting jet flow fields with a variation of injection pressure in a small-bore diesel engine
AU - Yang, Jinxin
AU - Rao, Lingzhe
AU - Zhang, Yilong
AU - de Silva, Charitha
AU - Kook, Sanghoon
N1 - Funding Information:
The experiments were performed at the UNSW Engine Research Laboratory, Sydney, Australia. The equipment and software used for FIV analysis was supported by the Australian Research Council via LIEF scheme. The author(s) received no financial support for the research, authorship, and/or publication of this article.
Funding Information:
The experiments were performed at the UNSW Engine Research Laboratory, Sydney, Australia. The equipment and software used for FIV analysis was supported by the Australian Research Council via LIEF scheme.
Publisher Copyright:
© IMechE 2020.
PY - 2021/9/1
Y1 - 2021/9/1
N2 - This study measures in-flame flow fields in a single-cylinder small-bore optical diesel engine using Flame Image Velocimetry (FIV) applied to high-speed soot luminosity movies. Three injection pressures were tested for a two-hole nozzle injector to cause jet-wall interaction and a significant jet-jet interaction within 45° inter-jet spacing. The high-pressure fuel jets were also under the strong influence of a swirl flow. For each test condition, soot luminosity signals were recorded at a high framing rate of 45 kHz with which the time-resolved, two-dimensional FIV post-processing was performed based on the image contrast variations associated with flame structure evolution and internal pattern change. A total of 100 combustion events for each injection pressure were recorded and processed to address the inherent cyclic variations. The ensemble-averaged flow fields were used for detailed flow structure discussion, and Reynolds decomposition using a spatial filtering method was applied to obtain high-frequency fluctuations that were found to be primarily turbulence. The detailed analysis of flow fields suggested that increased injection pressure leads to enhanced jet flow travelling along the bowl wall and higher flow vectors penetrating back towards the nozzle upon the impingement on the wall. Within the jet-jet interaction region, the flow vectors tend to follow the swirl direction, which increases with increasing injection pressure. The FIV also captured a turbulent ring vortex formed in the wall-jet head, which becomes larger and clearer at higher injection pressure. A vortex generated in the centre of combustion chamber was due to the swirl flow with its position being shifted at higher injection pressure. The bulk flow magnitude indicated significant cyclic variations, which increases with injection pressure. The turbulence intensity is also enhanced due to higher injection pressure, which primarily occurs in the wall-jet head region and the jet-jet interaction region.
AB - This study measures in-flame flow fields in a single-cylinder small-bore optical diesel engine using Flame Image Velocimetry (FIV) applied to high-speed soot luminosity movies. Three injection pressures were tested for a two-hole nozzle injector to cause jet-wall interaction and a significant jet-jet interaction within 45° inter-jet spacing. The high-pressure fuel jets were also under the strong influence of a swirl flow. For each test condition, soot luminosity signals were recorded at a high framing rate of 45 kHz with which the time-resolved, two-dimensional FIV post-processing was performed based on the image contrast variations associated with flame structure evolution and internal pattern change. A total of 100 combustion events for each injection pressure were recorded and processed to address the inherent cyclic variations. The ensemble-averaged flow fields were used for detailed flow structure discussion, and Reynolds decomposition using a spatial filtering method was applied to obtain high-frequency fluctuations that were found to be primarily turbulence. The detailed analysis of flow fields suggested that increased injection pressure leads to enhanced jet flow travelling along the bowl wall and higher flow vectors penetrating back towards the nozzle upon the impingement on the wall. Within the jet-jet interaction region, the flow vectors tend to follow the swirl direction, which increases with increasing injection pressure. The FIV also captured a turbulent ring vortex formed in the wall-jet head, which becomes larger and clearer at higher injection pressure. A vortex generated in the centre of combustion chamber was due to the swirl flow with its position being shifted at higher injection pressure. The bulk flow magnitude indicated significant cyclic variations, which increases with injection pressure. The turbulence intensity is also enhanced due to higher injection pressure, which primarily occurs in the wall-jet head region and the jet-jet interaction region.
KW - Diesel engine
KW - FIV
KW - in-flame flow field
KW - injection pressure variation
KW - natural soot luminosity
UR - http://www.scopus.com/inward/record.url?scp=85092133111&partnerID=8YFLogxK
U2 - 10.1177/1468087420960616
DO - 10.1177/1468087420960616
M3 - Article
AN - SCOPUS:85092133111
SN - 1468-0874
VL - 22
SP - 2968
EP - 2981
JO - International Journal of Engine Research
JF - International Journal of Engine Research
IS - 9
ER -