The biomass derivatives, including gas obtained from agricultural residues, are potential alternatives to power production in rural areas. Thus, gas can be utilized as the primary fuel in a diesel engine operating in dual fuel mode to generate electricity. This research investigates the combustion of such gas in an engine through a locally available substitute gas of controlled composition, consisting of a combination of liquefied petroleum gas and nitrogen (LPGN2). The selected composition has the same energy content as syngas. A LISTER PETTER diesel engine used for experimental purposes was modified to run on dual fuel. The engine was instrumented to assess parameters such as pressure, temperature, fuel flow and pollutant emissions. The engine operated at partial loads and a constant speed of 1500 rpm. LPGN2 mixture combustion analysis revealed a cylinder pressure trend comparable to the conventional diesel with lower pressure peaks. At low load, the maximum pressure for the diesel-LPGN2 (D-LPGN2) blend decreased by 16%. The heat release curves show the same combustion phases as for syngas in the dual-fuel engine. In addition, the specific consumption was higher with an overall low efficiency. The daily ignition is longer, and the diffusive combustion phase is more pronounced with the formulated gas, leading to a lower indicated mean pressure. The instability of combustion in dual fuel mode is reflected in an increase in the coefficient of variation (COVIMEP). At 20% engine load, the COVIMEP reaches 11.5% with D-LPGN2 while allowing the engine operation. Moreover, the specific consumption was 4,18 kg/kWh for D-LPGN2, with an overall efficiency of 16.2%. As expected for a gas with a low calorific value, specific consumption (Cs) is higher with D-LPGN2 than with pure diesel (D-P). The pollutant emissions were comparable to those of syngas, with a sharp reduction in nitrogen oxide concentrations of up to 73% at low loads. The engine combustion simulated using the thermodynamic 0D combustion model was satisfactory, with a root mean square error of less than 7%. These results provide interesting indications for optimizing syngas combustion in a low-load diesel engine in dual fuel mode.

Key words: Dual fuel engine; LPG-Nitrogen mixture; Syngas; Combustion; Modelling