E Richardson - Physics-based predictive modeling for ultra-low-emission combustion technology

Prospective technologies for low-emission power and propulsion systems rely on highly dilute, low-temperature combustion. Low-temperature combustion prevents formation of oxides of nitrogen, but it has not been achieved in automotive and aerospace applications due to lack of understanding and predictive models. This study will probe the fundamental fluid dynamic processes which are critical to ensure stable, efficient, and clean conversion of fuel energy under such highly dilute conditions. Two complementary technological applications motivate this study. The first is application of 'split-injection' strategies, which are being investigated by partners in the automotive industry. These strategies employ large numbers of separate fuel-injection events in order precisely to control the timing and rate of heat release and pollutant formation. The second application is the injection of highly dilute reactants into a flow structure that recirculates combustion products. This process underpins low-emission aero-engine development by project partner Rolls-Royce - indeed it is fundamental to the development of combustion systems in general. High-end scientific computing methods will be employed to perform full-resolution numerical experiments, designed to explain the relationship between the fluid-, mixing-, and chemical-dynamics of split-injection. For the first time, the age concept will be used in the analysis of these experiments; the age, or residence time, of a mixture is a natural reference quantity for understanding how kinetically limited combustion processes (e.g. autoignition, highly-dilute combustion, NOx and soot-particle formation) evolve. A novel modelling framework, built on this concept of fluid age will be developed and subsequently its potential for the design of ultra-low-emission combustion systems will be demonstrated in automotive and aerospace applications.