03/11/2025
By Danielle Fretwell
Candidate Name: Behlol Nawaz
Degree: Doctoral
Defense Date: Tuesday, March 25th, 2025
Time: Noon - 2 p.m.
Location: ETIC 445
Committee:
Advisor: J. Hunter Mack, Associate Professor, Dept. of Mechanical and Industrial Engineering, University of Massachusetts Lowell
Committee Members:
1. Ruizhe Ma, Assistant Professor, Miner School of Computer & Information Sciences, University of Massachusetts Lowell
2. Noah Van Dam, Assistant Professor, Dept. of Mechanical & Industrial Engineering, University of Massachusetts Lowell
3. Juan Pablo Trelles, Professor, Dept. of Mechanical & Industrial Engineering, University of Massachusetts Lowell
Brief Abstract:
Energy systems are a core component of most aspects of civilization and have a bearing on several key global issues. Fossil fuels are currently the dominant energy sources, but they create environmental pollution, contribute to climate change, and consume finite natural resources. In response to this, renewable energy systems are being added to the global portfolio of energy sources at an increasing pace. This has led to an increase in the diversification of energy sources worldwide. Not only are the newer sources more sustainable, but the diversification of the energy mix also makes the overall energy production infrastructure more robust and resilient to certain shock events. However, as many of the more promising renewable sources are intermittent and non-dispatchable, the storage and transmission of the energy they produce is critical and continues to be a challenge. Sustainable fuels can address these challenges and would be especially suitable for areas that require higher energy densities or scale, such as aviation, marine propulsion, heavy transportation, heating, or utility-scale storage. Conventional fuels such as gasoline, diesel, kerosene, and fuel oils have high energy densities and are easy to handle,
transport, and refuel. Therefore, renewable fuels would not only have to provide reduced, net-zero, or zero carbon emissions, but also meet or exceed the requirements for storage and transportation.
It is important to understand the fundamental combustion properties of fuels as they dictate the performance, emissions, safety, and design of combustion systems that use them. One such property is the intrinsic instability of flames for a given combustible mixture. They cause wrinkles (or cracks) on flame fronts, forming cellular structures that can impact performance and safety in some cases due to their effect on burning velocity, explosion risk, and emissions. Intrinsic instabilities are often studied in constant volume combustion chambers (CVCC) with optical access, which are experimental devices that allow the study of certain combustion properties and flame structure in a controlled environment. This dissertation focuses on methods for the detection and characterization of intrinsic instabilities in several fuels including ammonia (NH3), hydrogen (H2), and methane (CH4) with multiple combinations of diluents, under varied initial conditions. Several methods are explored for detecting wrinkling observed in high-speed images of spherical CVCC flames due to intrinsic instabilities. The use of pressure traces for detecting the instabilities using machine learning methods is also explored. This could be a potential alternative for CVCC systems that may not have optical access.
This work improves our understanding of intrinsic instabilities for novel fuel and diluent combinations. It also helps expand the methods used to study them, using image processing as well time series classification with pressure traces. Both of these contributions could make calculations and simulations of combustion systems more accurate by helping them account for the effects of intrinsic instabilities. That in turn would help with the design processes, making sure future combustion systems can be developed in a cost-effective manner, while improving their performance, reliability, and emissions.