Optimising thermal performance and emission of micro-combustor in micro-thermophotovoltaic system
| dc.contributor.author | Tong, Jinshen | |
| dc.date.accessioned | 2023-06-15T02:00:18Z | |
| dc.date.available | 2023-06-15T02:00:18Z | |
| dc.date.issued | 2023 | en |
| dc.description.abstract | Microfabrication technology has revolutionized the development of Micro- electromechanical systems (MEMS) and enabled the creation of MEMS-based power devices with a wide range of applications. Micro-thermophotovoltaic system (MTPV) as a MEMS-based system has gained significant attention in recent years, offering several advantages such as noiseless operation, fuel versatility, portability, and low maintenance. Hence, it is critical to develop a micro-combustor with high thermal performance to achieve higher efficiency in MTPV systems. However, it is difficult to improve the micro-combustor's thermal performance because its reduced size leads to massive heat loss and flame quenching. Therefore, obtaining higher and more uniform wall temperature is the goal in the development of the micro-combustor in this study. The aim of the study is as follows: (1) to study the fundamental knowledge of the flame characteristics and reaction mechanisms, (2) to design the structure and analysis of the thermal performance of the premixed methane/air micro-combustor by altering the operating parameters, (3) to improve the thermal performance and mitigate the NOx emission in ammonia/oxygen fueled micro-combustor. Elevating the inlet temperature stabilizes the flame and extends the blowout limit; however, it has a negative effect on the mean temperature and standard deviation of the outer wall when the inlet velocity is small. Besides, at the high inlet velocities (≥ 0.8 m/s), the outer wall mean temperature (OWMT) and standard deviation were optimized when the inlet temperature is 400 K, and CO2 production is highest. The choice of reaction mechanism significantly affects combustion performance and accuracy in numerical analysis. The one-step reaction mechanism shows a significant difference in OWMT along the flow stream direction, whereas the 25-step reaction mechanism accurately predicts OWMT and can be used in further micro-combustion studies. The presence of a cavity in a combustor increases the OWMT by 64.8 K, resulting in a more uniform temperature distribution due to its ability to anchor the high- temperature zone upstream and preheat the fresh mixture. Cavity height is a critical factor in thermal performance, and OWMT and temperature uniformity are optimized when the dimensionless height of 1/5 above. Increasing the inlet velocity increases OWMT, and the optimal equivalence ratio corresponds to the maximum OWMT and uniform temperature distribution. Implementing the cavity leads to a 9.8% increase in exergy efficiency compared to a conventional micro-combustor. However, adding hydrogen negatively affects OWMT and exergy efficiency while enhancing temperature uniformity. The thermal performance and NOx emissions of a micro-combustor are affected by various parameters, including inlet pressure, equivalence ratio, and hydrogen blending. Increasing the inlet pressure enhances the mixing process, increases the temperature distribution along the outer wall, and reduces NOx emissions due to the lack of O and OH radicals. Varying the equivalence ratio between 0.95 to 1.1 has a minor effect on thermal performance but a significant impact on NOx emissions. A decrease in the equivalence ratio results in a large increase in NO emission. Blending hydrogen less than 15% at a low inlet velocity in ammonia-oxygen combustion greatly reduces NOx emissions with only a slight loss in the standard deviation of outer wall temperature. However, increasing the inlet pressure negatively impacts the exergy efficiency of the micro-combustor system. | en |
| dc.identifier.uri | https://hdl.handle.net/10092/105573 | |
| dc.identifier.uri | http://dx.doi.org/10.26021/14667 | |
| dc.language | English | |
| dc.language.iso | en | en |
| dc.rights | All Right Reserved | en |
| dc.rights.uri | https://canterbury.libguides.com/rights/theses | en |
| dc.title | Optimising thermal performance and emission of micro-combustor in micro-thermophotovoltaic system | en |
| dc.type | Theses / Dissertations | en |
| thesis.degree.discipline | Mechanical Engineering | en |
| thesis.degree.grantor | University of Canterbury | en |
| thesis.degree.level | Masters | en |
| thesis.degree.name | Master of Engineering | en |
| uc.bibnumber | 3292375 | |
| uc.college | Faculty of Engineering | en |