Radiation Measurements and Temperature Estimates of Unsteady Exhaust Plumes Exiting from a Turbine Driven by Pulsed Detonation Combustion

Unsteady exhaust plumes exiting from a turbine driven by pulsed detonation combustion are studied using radiation intensity measurements acquired with a high speed infrared camera. The gas temperature near the turbine exit is estimated using inverse analysis of the radiation measurements. Phase-averaged and time-averaged radiation intensity and temperature values are reported for a range of operating frequencies (10 – 20 Hz), equivalence ratios (1.0 – 1.4), fuel/air fill fractions (0.6 – 0.9), and air purge fractions (0.50 – 0.75). An increase in the operating frequency results in an increase in the time-average temperature. An increase in the equivalence ratio from stoichiometric to fuel rich conditions results in an increase in the peak temperature and smaller effects on the time-averaged temperature. An increase in the fill fraction or decrease in the purge fraction causes the peak and time-averaged temperature to increase for all operating conditions considered in this work. Cycle-to-cycle variation in the peak radiation intensity and temperature values is found to be minimal. The temperature values are useful for improving unsteady efficiency calculations of turbines driven by pressure gain combustion. This work demonstrates that imaging in the mid-infrared spectrum coupled with inverse radiation analysis is an effective non-intrusive technique for estimating gas temperatures in low luminosity, unsteady, high speed flows of practical interest.