Maximum-efficiency architectures for regenerative steady-flow combustion engines
Abstract/Contents
- Abstract
- Steady-flow combustion engines currently account for about 20% of world-wide electricity generation (gas turbine engines) and almost all of commercial aviation (jet engines). With growing interest in natural gas as a low-carbon alternative to coal, and the economic opportunity associated with the discovery of potentially large natural gas reserves, steady-flow combustion engines are likely to play a larger role in energy conversion. Evidently, increasing engine efficiency is of primary importance and has been an active topic of research for over a century. On the one hand, many advanced engine cycles (e.g., humidified cycles, oxy-fuel cycles, fuel-cell/gas turbine combined cycles) that promise higher efficiency are being proposed and analyzed. But on the other hand, there is a sense of resignation that raising turbine inlet temperature is our only hope for higher efficiency. Simply stated, we do not know what engine architectures provide maximum efficiency. The objective of this dissertation is to establish maximum-efficiency architectures allowed by physics and implementable by engineering for regenerative, steady-flow combustion engines. The goal is also to advance thermodynamic understanding of the tradeoffs in reducing sources of entropy generation (irreversibility) that are the reason for inefficiency in engines. To do so, an irreversibility-minimization approach is developed that has three stages. First, reactive engine architectures are modeled as sequences of energy transfer and transformation processes, and represented as trajectories traced by the working fluid in thermodynamic state space. Second, total irreversibility in any architecture is calculated as a function of the trajectory that represents it. Third, the extremal trajectory is identified that minimizes total irreversibility while satisfying constraints such as the turbine inlet temperature limit. Two methods are employed for identifying the extremal trajectory: optimal-control theory and attractor-trajectory based methodology. The former is an extension of the calculus of variations. The latter is a physics-based methodology, developed in this work specifically for engine-architecture optimization to overcome some of the challenges associated with obtaining solutions using the former. The extremal trajectory represents the optimal architecture that has efficiency greater than any other conceivable architecture subject to the same constraints, and the attractor-trajectory based methodology provides insights into the thermodynamics of regenerative steady-flow combustion engines.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2012 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Ramakrishnan, Sankaran |
|---|---|
| Associated with | Stanford University, Department of Mechanical Engineering |
| Primary advisor | Edwards, Christopher |
| Thesis advisor | Edwards, Christopher |
| Thesis advisor | Bowman, Craig T. (Craig Thomas), 1939- |
| Thesis advisor | Gerdes, J. Christian |
| Advisor | Bowman, Craig T. (Craig Thomas), 1939- |
| Advisor | Gerdes, J. Christian |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Sankaran Ramakrishnan. |
|---|---|
| Note | Submitted to the Department of Mechanical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2012. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2012 by Sankaran Ramakrishnan
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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