Acoustically modulated pressure gain combustor for application to isochoric heat addition gas turbines



  • After nearly 80 years of development, only incremental gains in conventional gas turbine engine eciency are possible at signi cant cost. As these heat engines account for a signi cant portion of global energy consumption, there remains great interest in producing further
    performance improvements.
  • If a large gain in gas turbine eciency is to be realize, a deviation from convention is necessary
  • The largest loss of thermodynamic availability in a gas turbine engine occurs within the combustion chamber. This results from the net loss
    of total pressure during the isobaric heat addition process. This loss signi cantly reduces the eciency of the cycle.
  • The net loss in total pressure may be replaced with a net gain if the heat addition process was replaced with an isochoric one. These
    devices are known as constant volume or pressure gain combustors.


  • For the purpose of studying a pressure gain combustor in gas turbine relevant conditions, an acoustically modulated pulsed combustor has
    been developed.
  • This combustor operates on the unsteady Humphrey thermodynamic cycle and has actively modulated fuel and air injection.
  • The 40 cm pulsed combustor operates at 500 Hz and is coupled with an unsteady ejector to dampen ow oscillations that would decrease
    turbine performance.


  • No experimental data has been obtained for a Pulsed Combustor Ejector Shroud system (PCES) operating in gas turbine relevant conditions (i.e. elevated pressure).
  • Also, little experimental data exists detailing PCES pollutant emissions (NOx, CO, UHC), none at relevant pressures. For this reason, the objectives are:
    • Replicated and compare with previous low pressure experimental
    • Characterize PCES system performance
    • Demonstrate net total pressure gain across PCES at 10 bar with liquid transportation fuels.

Experimental Apparatus

  •  Pressure-gain combust or experimental apparatus is composed pulsed-combustor coupled with an unsteady ejector and enclosed within a shroud
  • High-pressure shroud is capable of sustained operation at 10 bar, with 0.5 kg/second of inlet air
  • Apparatus allows for characterization of the pressure-gain combustion system in simulated gas turbine conditions through measurement of
    the total pressure ratio across the heat addition process as a function of the total temperature ratio
  • Initial experiments will be conducted with gaseous fuels with the final objective of moving to liquid transportation fuels.
    Figure 1: High pressure shroud for pressure gain combustor characterization




Figure 2 : High pressure shroud for pressure gain combustor characterization



Figure 3 : Volume rendering of temperature with fuel mass fraction isocontours