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Chapter 7: Conclusion
Experiment and numerical simulation have been conducted to study the characteristics
of Swiss-roll combustors, and the feasibility of applying to gas mask system was
investigated. A three-dimensional (3D) numerical model was built and results were
validated with experimental data. Via 3D model, the accuracy of the quasi-1D
assumption out-of-plane heat loss model for 2D model in different cases was verified.
The flame curvature was observed in the 3D numerical model and it affects the extinction
limits when the combustors are too tall. A fluid phenomenon called Dean vortices can be
found in 3D model when the turbulence model is not activated, and their effect on heat
transfer enhancement is similar to what turbulence does. 2D model with turbulence
model activated can be used to reproduce 3D model results when out-of-plane heat loss
model is valid and the flame curvature effect is not significant. A 4-step reaction model
developed in the turbulent flow reactor, in which the reaction temperature and pressure
range is similar to Swiss-roll combustor, was employed to justify the use of 1-step model
with adjusting pre-exponential term. The results showed both reaction models are
comparable with each other.
Effects of different scales were studied via 3 different scale but geometrically identical
3D numerical models. At the same Re (the same NTU), smaller scale combustor showed
better performance (in terms of lean limits) at low Re region due to lower overall heat
loss to heat release ratio, which basically means lower heat loss coefficient α. On the
other hand, at high Re region, larger scale combustors have better performance due to
more residence time. Effects of geometrical parameter (number of turns) were studied in