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Abstract

Dynamical systems analysis was employed as an alternative investigative tool to conventional reaction path analysis and sensitivity analysis in methanol-air auto-ignition, in which the non-linear chemical rate equations describing a homogeneous, methanol-air auto-ignition system were linearised. The resultant system of linear, inhomogeneous differential equations were solved analytically using an eigen-mode analysis. The numerically determined solution to the non-linear auto-ignition trajectory was employed to determine the local analytic behaviour for a number of regular points along the solution trajectory to equilibrium. The solution trajectory was found to qualitatively change three times, thereby defining four different regions in the time and temperature domain. The dominant eigen-mode solutions were expressed in terms of dominant reactions at regular intervals along the solution path, revealing the dominant local chemistry. The solution trajectory was dominated by four explosive modes in the first, low temperature region (T < 1,090 K). Two dominant explosive modes coupled to form an explosive, oscillating mode in the second region (1,090 K < T < 1,160 K). In the third region (1,160 K < T < 2,000 K), the explosive, oscillating mode changed to a decaying, oscillating mode. The changes in the low temperature region of the solution trajectory were found to be associated with the critical points in the evolution of the branching agent (hydrogen peroxide) concentration. The third qualitative change occurred at T ~ 2,000 K, when the dominant decaying, oscillating mode describing methanol and formaldehyde oxidation to carbon monoxide collapsed, to be replaced with real, decaying modes (proper stable nodes) describing the wet oxidation of carbon monoxide to carbon dioxide, and its reverse reaction, together with the high temperature formation of water and other equilibrium products.

Publication Type:	Article
Subjects:	T Technology > TJ Mechanical engineering and machinery
Departments:	School of Science & Technology > Engineering

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