Diesel exhaust gas control of selective catalytic reduction system using sliding mode controller

Abstract

Selective Catalytic Reduction (SCR) is a well-known method of reducing Nitrogen Oxide (NOx) emissions from stationary and mobile diesel engines. Due to the growing need for retrofit SCR systems in diesel engines, significant progress must be made in improving catalyst activity, injection controller, and by-product minimization. This thesis presents the design and development of retrofit SCR and fast-SCR systems for a stationary constant-speed diesel engine. The performance of retrofit system is improved with SCR catalyst and then combined with pre-oxidation catalyst, with and without a mixer. Control of SCR systems for a constant-speed stationary diesel engine as well as automotive diesel engine, represented by linearized third order and fourth order state-space models using Discrete-time Super-Twisting Sliding Mode Controller (DSTSMC) are carried out. newlineThe first work is about the design and fabrication of an expansion chamber, catalytic substrate, mixer, and urea injection elements of SCR and fast-SCR systems for a stationary diesel engine. A pair of ceramic monolith substrates are selected and, coated with cerium oxide and copper-zeolite for pre-oxidation and SCR catalyst, respectively. The catalyst for SCR and fast-SCR systems that have been synthesized are analyzed by various physio-chemical characterization methods. newlineIn the second work, the experimental investigation of NOx conversion efficiency of SCR system for the stationary diesel engine under Non-Road Steady Cycle (NRSC) is performed. The emission reduction by the retrofit system and the engine performance indicators are evaluated with the SCR catalyst and then combined with pre-oxidation catalyst, with and without a mixer. newline