  The ``Shockless Explosion Combustion" (SEC) concept for gas turbine
combustors, introduced in 2014, approximates constant volume combustion (CVC)
by harnessing acoustic confinement of autoigniting gas packets. The resulting
pressure waves simultaneously transmit combustion energy to a turbine plenum
and facilitate the combustor's recharging against an average pressure gain.
Challenges in actualizing an SEC-driven gas turbine include i) the creation of
charge stratifications for nearly homogeneous autoignition, ii) protecting the
turbo components from combustion-induced pressure fluctuations, iii) providing
evidence that efficiency gains comparable to those of CVC over deflagrative
combustion can be realized, and iv) designing an effective one-way intake
valve. This work addresses challenges i)-iii) utilizing computational engine
models incorporating a quasi-one-dimensional combustor, zero- and
two-dimensional compressor and turbine plena, and quasi-stationary turbo
components. Two SEC operational modes are identified which fire at roughly one
and two times the combustors' acoustic frequencies. Results for SEC-driven gas
turbines with compressor pressure ratios of 6:1 and 20:1 reveal 1.5-fold mean
pressure gains across the combustors. Assuming ideally efficient compressors
and turbines, efficiency gains over engines with deflagration-based combustors
of 30% and 18% are realized, respectively. With absolute values of 52% and 66%,
the obtained efficiencies are close to the theoretical Humphrey cycle
efficiencies of 54% and 65% for the mentioned pre-compression ratios. Detailed
thermodynamic cycle analyses for individual gas parcels suggest that there is
room for further efficiency gains through optimized plenum and combustor
designs.
