Abstract
In this paper, an alternative micro-gas turbine is
proposed, where the traditional compressor-turbine arrangement is
replaced by an axial, throughflow wave rotor. The investigated
wave rotor features symmetrically cambered wall profiles and
angled port arrangement for shaft power extraction and uses shock
and rarefaction waves for pressure exchange and to achieve gas
compression and expansion within a single device.
A validated quasi-one-dimensional model that solves the laminar
Navier-Stokes equations using a two-step Richtmyer scheme with
minmod flux limiter is employed to characterise and examine microgas
turbine behaviour. The model accounts for wall heat transfer,
flow leakage, wall friction and inviscid blade forces. In addition,
modified boundary conditions consider finite passage opening effects
and a simple steady-flow combustor model is defined that links
the high pressure in- and outlet ports.
The model is used to conduct a parametric study to investigate
the effects of leakage gap, heat release rate, exhaust backpressure,
as well as profile camber on gas turbine performance with a focus
on generated combustor compression and expansion efficiency,
shaft power and system efficiency. The implications of combustor
pressure loss as well as effects of a potential recuperator are
discussed as well. The results identify axial leakage and combustor
pressure loss as primary drivers for enhanced performance. Finally,
the results reinforce the capacity of wave rotors to compress and
expand gas efficiently, while thermal efficiency remains below 10
percent.
