The role of structural heat exchange and heat loss in the design of efficient silicon micro-combustors

The performance of millimeter-scale combustors intended for miniaturized power and propulsion systems is strongly influenced by heat exchange to and within the combustor structure. Accordingly, a one-dimensional model with full chemistry that includes heat exchange to and within the combustor wall has been developed. It is used to study the effects of axial heat transfer from the post-flame to the pre-flame via wall conduction in a silicon micro-channel combustor with planar symmetry. The simulations show that axial heat transfer widens stability limits, increases the burning rate, and can enable the construction of smaller, higher power density combustors. Axial heat transfer also enhances the benefits of operating at elevated pressures. The simulations also show that heat loss to the environment places a lower bound on the combustor volume. Maximum power density combustor configurations are identified under adiabatic and non-adiabatic conditions. The maximum power density tends to increase with increasing pressure while the micro-channel length and height associated with the maximum tend to decrease.