Conventional combustion processes are known to be highly irreversible processes. The
potential to obtain useful work from the fuel is degraded during the combustion process. For
example, for a reciprocating internal combustion engine, about 20% or more of the potential
work from the fuel is destroyed during the combustion process. This potential work is known as
availability (a thermodynamic property). The motivation for the current work was to develop a
conceptual model of a set of processes related to reciprocating engines that would eliminate this
destruction of availability. One conceptual model, proposed by Keenan, suggested that a
preselected set of “reactants” could be compressed (at constant composition) to a high
temperature and pressure. At this high temperature and pressure, the “reactants” would be in
chemical equilibrium. At this point, the “reactants” would be expanded back to the original
volume. The expansion process would consist of a “shifting” chemical equilibrium such that the
composition during expansion would continue to change. At the end of the compression and
expansion, net work would be available without destroying any of the work potential of the fuel.
The purpose of the current work was to develop a quantitative model of this concept, and to use
the model in a series of computations to examine the effects of temperature, pressure, and other
parameters on the work production capability of the concept.
The concept was studied for eight different fuels for various conditions. In general, the
net work output increased as the temperature, pressure and compression ratio increased. For
low compression temperatures and pressures, the concept resulted in a small amount of net
work produced without destroying any fuel availability. For sufficiently high compression
pressure and temperature (e.g., 10 MPa and 6000 K, respectively), however, the thermal
efficiency was ~28% for isooctane and was ~40% for hydrogen and methane, for air as the
oxidant, an equivalence ratio of 1.0, and a compression ratio of 18. Although the temperatures
and pressures considered are well beyond practical values for the materials and designs of
today, the general result of the study is that conditions can be identified to eliminate the
combustion irreversibility.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-1351 |
| Date | 15 May 2009 |
| Creators | Patrawala, Kaushik Tanvir |
| Contributors | Caton, Jerald A. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | electronic, application/pdf, born digital |
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