- Title
- Characterisation of biomass feedstocks relaxation properties using visco-elastic models
- Creator
- Owonikoko, Aminu
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2025
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Biomass is a renewable organic material that has the potential to be a significant feedstock for producing renewable energy and other products. Biomass potential as a renewable energy feedstock has not been fully utilised and the current potential supply of biomass feedstocks is dedicated biomass and agricultural residues. These materials form part of what is termed second-generation biomass because they do not compete with food crops. To understand the handling and storage characteristics of the biomass materials, this project assessed the compactive-relaxation of fuzzy cotton seeds, leafy biomass, wheat straw, woodchips, and wood pellets behaviour experimentally and theoretically under various loads with respect to time. This knowledge led to a significant step forward in understanding the characterisation of biomass materials. A fundamental and in-depth understanding of the compactive-relaxation response of fuzzy cotton seeds, leafy biomass, wheat straw, woodchips, and wood pellets ensembles have been investigated. These investigations have helped to examine data and optimise visco-elastic models (i.e. stress relaxation models) deeply particularly the Zener model and two Maxwell elements model due to their originality which facilitates a better understanding of the biomass material relaxation mechanics such as fast relaxation and slow relaxation with respect to their respective relaxation time constants 1 and 2. The biomass relaxation characteristics assessed at different times (i.e., at 60, 120, and 180 seconds) using relaxation ratio and principle (initial) stress have set a pace in understanding the stress relief required for biomass to flow reliably during handling. The results from this work have led to the determination of the stress relief experienced by the material during compaction which justifies the stress relaxation of biomass materials investigated in this project. In terms of novelty, the project methodology is well-differentiated and adopted the visco-elastic models with their parameters (principle/initial stress, elastic stress, decay stresses 1 and 2, relaxation time constants 1 and 2) and interpretations, analyse, and optimised them in a novel way different from what is available in the literature. Numerical and graphical optimisation were used to develop a novel time constant 1 and optimised time constant 2 for two Maxwell elements model and reduce errors in the relaxation model and maximise curve fitting closeness between measured data and model data in leafy biomass, wheat straw, woodchips, and wood pellets without depending heavily on curve fitting tools (e.g., MATLAB and OriginPro software).
- Subject
- biomass materials; compactive-relaxation; Visco elastic models such as zener model; fractional zener model; two maxwell elements model; peleg model; single Maxwell element; time constants; numerical and graphical optimisation
- Identifier
- http://hdl.handle.net/1959.13/1517619
- Identifier
- uon:57137
- Rights
- Copyright 2025 Aminu Owonikoko
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 7 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 343 KB | Adobe Acrobat PDF | View Details Download |