PERFORMANCES OF A MESOCOMBUSTOR AT 0.3 MPa WITH PREHEATED AIR

Improvements in understanding how to design future mesocombustors are mandatory for the development of propulsion and power-generation systems having a size of few centimeters or even smaller and able to deliver high performances (lasting, power and energy density). To advance and extend the analysis carried out by the same authors in previous works, the experimental investigation of a 254 mm3 non-premixed swirling cylindrical mesocombustor, fed by methane/air at 0.3 MPa and with air preheated up to 200 °C was performed. The combustion pressure was chosen based on the values quoted in literature for gas turbines of centimeter scale. The analysis is carried out for several equivalence ratios and at two pressure values (0.1 and 0.3 MPa). To this aim the combustor is enclosed in a pressurized vessel. The desired pressure value inside the vessel is obtained by discharging a controlled mass flow rate of nitrogen through a sonic orifice. Data about the behavior and the performances of the meso-combustor (stability, exhaust gas composition, exhaust gas temperature, etc.) are obtained at the operating conditions specified above. The results evidenced that either the pre-heating of the combustion air or the increase of pressure are effective in improving the general performances (stability limits, chemical efficiency). Based on the measured chemical efficiency, the maximum power density of the meso-combustor resulted to be above 1.4 GW/m3 at 0.3 MPa, while the maximum exhaust gas temperature resulted to be higher than 1570 K. Nevertheless the maximum values of chemical efficiency, power density and exhaust gas temperature cannot all be achieved simultaneously. Finally the measured data (CO, CO2 and TUHC molar fractions, gas temperature, chemical efficiency) appear to be well correlated with the mean gas residence times.