Research Projects

The carbon-free nature of ammonia, coupled with the existing infrastructure for its generation and transport, has led to its prominence as a fuel in gas turbines, especially in marine applications. As the development of this fuel technology matures, attention must be given to safety aspects. The absence of carbon molecules and fuel-bound nitrogen leads to very different reaction kinetics. Hence, studying the chemical kinetic response of ammonia flames to clean fire suppressants such as CO₂, N₂, and hydrohalocarbons (FM-200, Novec 1230, etc.) is of interest. Additionally, it is often blended with other low-carbon-intensity fuels, such as hydrogen and methane, to augment reactivity. The behaviour of such binary and ternary blends under the influence of clean flame inhibitors should be studied. Under the present proposal, an optically accessible spherical combustion chamber will be designed to achieve the discussed objectives. The experimental facility will be pressure tested up to 100 bars so that any relevant pressure conditions for the IC engine and gas turbine can be created inside the vessel. A heating coil embedded in the chamber wall will enable the study of reaction kinetics at elevated temperature conditions as well. Fundamental properties of the fuel, related to flame ignition (minimum ignition energy), propagation (flame speed), and flammability limits will be quantified in the proposed experimental facility. The reaction chamber will be equipped with a high-frequency pressure transducer to monitor pressure oscillation. The peak overpressure and the rate of pressure rise will indicate the influence of chemical inhibitors on the flame. Additionally, flame propagation will be monitored using a Schlieren imaging facility enabled by the quartz windows of the combustion chamber. Flame propagation images acquired with a high-speed camera will be used to determine the flame speed under stretched conditions. The data can be extrapolated to obtain the freely propagating flame speed as well. Finally, the minimum ignition energy needed for flame kernel development will be quantified by measuring the voltage in a capacitive discharge ignition system. The spherical combustion chamber is amenable to 2D modelling as the flame propagation characteristics sufficiently away from the wall can be solely expressed in terms of the radial coordinate and time. An in-house numerical code will be developed and validated against the rich dataset generated on flame speed, peak overpressure, and ignition energy. Any flame surface instability, if observed, will also be analyzed numerically with the help of existing codes such as OpenFOAM or ANSYS Fluent. Insights on radical recombination cycles and reaction pathways will be gained through numerical analysis. In summary, the influence of flame inhibitors on pure ammonia and ammonia-methane-hydrogen blended fuels will be explored comprehensively through flame imaging, dynamic pressure sensing, and numerical modelling.