**2. Aim and Scope of the Study**

Co-combustion of gaseous fuels in a two-stage combustion system is a relatively unrecognized solution. For this reason, the authors decided to conduct a comparative experimental study using a single-cylinder research engine. The TJI system used a singlefuel operation where the fuel was methane, then the strategy was changed to a dual-fuel operation, and propane was supplied to the ignition chamber instead of methane. So, the comparison subject is the effect of changing the fuel supplied to the ignition chamber. In the research program on the effect of fuel type, large changes in the dose of fuel supplied to the prechamber with varying values of the excess air ratio were realized.

The questions sought to be answered regarding the thermodynamics of the process were (1) how the excess air ratio affects the combustion process, and (2) how the dose of fuel fed into the prechamber affects combustion efficiency.
