This paper reports on a study that experimentally investigates MILD (Moderate or Intense Low-oxygen Dilution) oxy-combustion of Natural Gas (NG),Liquefied Petroleum Gas (LPG) and Ethylene (ETH).Tests were conducted at a laboratory-scale furnace with a parallel burner system at a firing rate of 13 kW.The MILD oxy-combustion was found to work well for all the fuels,even using pure oxygen as oxidant.Very low emissions of NOx and CO were measured for a range of equivalence ratio.The thermal field measurements of MILD combustion with air and the CO2/O2 mixture are compared,finding uniform temperature distributions for both cases.The furnace temperatures and the global emission measurements are also presented.It is revealed that,externally diluted at a fixed mass fraction of CO2,the MILD oxy-combustion can be achieved only when equivalence ratio is greater than a critical value,despite any of the fuels.As the equivalence ratio is increased from 0.5 to 1,the temperature and NOx emissions decrease.When the equivalence ratio reaches 1,extremely high CO emission occurs.Furthermore,the establishment of the MILD oxy-combustion requires the fuel injection momentum to be sufficiently high.This can be achieved by reducing the fuel nozzle diameter,using CO2 to dilute fuel or even changing fuel,e.g.,from LPG and ETH to NG.