Design Procedure of a Novel Microturbine Low NOx Conical Wire-Mesh Duct Burner

Abstract

Nowadays, air pollution and climate change have become a global environmental problem. As a result, government regulations worldwide are becoming increasingly stringent. This has led to an urgent need to develop new designs and methods for improving combustion systems to minimize the production of toxic emissions, such as nitrogen oxides. Microturbine based cogeneration units are one of the interesting alternatives for combined electrical power and heat generation (CHP). Microturbine CHP technology still needs to be developed to increase efficiency and heat-to-power ratio and to improve operating flexibility. This can all be obtained by adding a duct burner to the CHP unit. This paper documents the design process for a novel low NOx conical wire-mesh duct burner for the development of a more efficient microcogeneration unit. This burner provides the thermal energy necessary to raise the microturbine exhaust gas temperature to increase the heat recovery capability. The duct burner implements both lean premixed and surface combustion techniques to achieve low NOx and CO emission levels. The design process includes a set of preliminary design procedures relating the use of empirical and semiempirical models. The preliminary design procedures were verified and validated for key components, such as the duct burner premixer, using the laser sheet illumination (LSI) technique. The LSI was used to study the mixing process inside the premixer fitted with different swirlers. The designed duct burner successfully operated in a blue flame mode over a wide range of conditions with NOx emissions of less than 5 ppmv and CO emissions of less than 10 ppmv (corrected to 15% O2).