Exhaust thermochemical recovery in low carbon vehicles via catalytic reforming of renewable fuels

Mardani, Moloud (2023). Exhaust thermochemical recovery in low carbon vehicles via catalytic reforming of renewable fuels. University of Birmingham. Ph.D.

Mardani2023PhD.pdf
Text - Accepted Version
Restricted to Repository staff only until 31 December 2027.
Available under License All rights reserved.
Download (12MB) | Request a copy

Abstract

The necessity of gradual reduction of fossil fuels dependence and development of renewable fuels is strongly shaped by environmental challenges and fossil fuel resources. Automotive industry is one of the main sources of toxic emissions in the environment. In recent years, substantial developments and research have been accomplished to partially substitute fossil fuels with clean and renewable alternatives in combustion engines.

Fuel reforming is known as a technique for thermochemical exhaust waste energy recuperation for onboard hydrogen production. Hydrogen as a cost-effective and environmentally friendly fuel can be considered for automotive usage. However, hydrogen production from reforming of petroleum-based fuels, like gasoline, is unsustainable. One of the potential solutions for gradual reduction of fossil fuel dependence is partially substitution of these fuels with clean and renewable alternatives such as biofuels. This study aims to investigate the exhaust gas fuel reforming of biofuels such as butanol and ethanol. For this purpose, the possibility of hydrogen production through catalytic reforming of biofuels, in a pure and blended mixture, using the real exhaust composition of a modern gasoline direct injection (GDI) engine was investigated. Some key parameters are investigated both experimentally and theoretically to extend the potential and reliability of this method toward improving the GDI engine efficiency, fuel economy and emissions.

The experimental analyses were conducted on Rh/CZN and Rh-Pt catalysts to investigate the feasibility of biofuels reforming and compare with thermodynamic equilibrium predictions. Thermodynamic equilibrium calculations of biofuel reforming process were performed based on the Gibbs energy minimisation method using ANSYS-Chemkin software to model complex gas-phase reactions inside the catalyst bed. Furthermore, computational fluid dynamic (CFD) analysis of fuel reformer unit was conducted using CFD software ANSYSII Fluent to predict heat transfer, temperature distribution and fluid flow behaviour within the full-scale fuel reformer. Governing equations for solid and fluid domains were discretised based on FVM (Finite Volume Method) and a standard K-epsilon model was employed to model turbulent fluid flow inside the domains. Generally, a reasonable agreement was observed between experimental, numerical and thermodynamic equilibrium data.

Richer H2 syngas mixture with higher calorific value and reforming process efficiency was achieved from biofuel reforming process owing to lower endothermicity of biofuel reforming compared to gasoline in addition to weaker molecular bonds and higher molecular diffusivity rate of biofuels which leads to efficient use of the catalyst. The results of simulated REGR (reformed exhaust gas recirculation) were evidence that the integration of REGR in a GDI engine benefits both CO2 reduction and fuel replacement fractions, which are proportional to the engine performance and the reformate calorific value. Overall, the implementation of a full-scale fuel reformer system using pure or biofuel-gasoline blend for exhaust heat recovery and on-board H2 production has been accredited for the effective application of the REGR system in practical conditions.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):