Catalytic Combustion: An Important Consideration for Future Applications

Abstract

Many problems in practical combustion devices are caused by the need to establish a near-stoichiometric zone which aids in the achievement of stable, highly-efficient combustion. For example, if operation at low equivalence ratios (φ ∼ 0.6) were practical, NO_x, emission and combustion chamber cooling requirements could be reduced. The present work describes the results of a large-scale experiment where combustion stability was achieved through the use of a catalytic bed within the reaction zone (i.e., catalytic combustion). Since this scheme requires design of a system which results in uniform fuel-air mixing and a uniform velocity profile, the exhaust gases closely approximate isothermal plug flow, thus avoiding many additional current system disadvantages due to severe temperature gradients. Testing was conducted at pressures up to 10.5 atmospheres and exhaust temperatures up to 1589 °K. Performance trends with fuel-air ratio, inlet temperature, reference velocity and pressure were obtained. A literature search was conducted to collect available catalytic oxidation information. Characteristics of noble metal and transition metal oxides are discussed. Results of the present work are interpreted vis-a-vis possible future applications. A summary of development work required before practical application is offered.