Colorless Distributed Combustion (CDC) is a novel method to enhance flame stability and thermal field uniformity, increase combustion efficiency and reduce pollutants emission, including noise. The focus of this thesis is to investigate swirl-assisted distributed combustion at high thermal intensity for gas turbine application. This thesis investigates the impact of fuel enrichment on CDC conditions by using naphthalene as a fuel additive in ethanol to increase the heating value without compromising ultra-low emissions, in addition to investigating how CDC fuel flexibility can mitigate instability associate with hydrogen enriched alternate fuels. To better predict and implement CDC design in future gas turbine combustors a distributed combustion index (DCI) will be developed to determine the impact of heat release intensity, equivalence ratio, preheat temperature and entrainment gas on distributed conditions. Lastly, the impact of flowfield interaction on achieving CDC condition will be examined for enhanced understanding of mixing required for CDC.