Transonic Combustion or TSCi™ is a novel combustion process based on the patented concept of injection-ignition of fuel. The process takes advantage of the improved mixing properties of supercritical fuel to achieve high yet controlled rates of heat release and high cycle efficiency. However, there is little science that documents the mixing process, ignition characteristics and combustion behavior of gasoline-like fuels in supercritical conditions, let alone the fluid transport properties. Thus, experimental studies and modeling efforts are necessary to enhance understanding of this combustion process and for effective development of this technology.This paper focuses on the model development and validation efforts for TSCi™ in an optical pressure chamber. An optically accessible pressure chamber was used to study the combustion of an injection-ignited supercritical fuel. Chemistry and Computational Fluid Dynamics (CFD) models were developed to simulate TSCi™ and were validated against data from the pressure chamber. This paper focuses on the validation efforts for supercritical n-heptane injected at different pressures. The comparison metrics encompassed fluid jet penetration, ignition delay and lift-off length.A reduced chemistry model for n-heptane was developed for the supercritical regime. The reduction process included sensitivity studies, to match ignition delay timing to results from shock-tube experiments available in literature. The chemistry model was implemented in a transient three-dimensional CFD simulation. The simulation results were then validated against data from the pressure chamber and the penetration rate, ignition delay and lift-off-length compared well with the experimental data.