The efficiency of a pulsed detonation combustor–axial turbine integration

Abstract

The paper presents a detailed numerical investigation of a pulsed detonation combustor (PDC) coupled with a transonic axial turbine stage. The time-resolved numerical analysis includes detailed chemistry to replicate detonation combustion in a stoichiometric hydrogenair mixture, and it is fully coupled with the turbine stage flow simulation. The PDC-turbine performance and flow behaviour are analyzed for different power input conditions, by varying the system purge fraction. Such analysis allows for the establishment of cycle averaged performance data and also to identify key unsteady gas dynamic interactions occurring in the system. The results obtained allow for a better insight on the source and effect of different loss mechanisms occurring in the coupled PDC-turbine system. One key aspect arises from the interaction between the non-stationary PDC outflow and the constant rotor blade speed. Such interaction results in pronounced variations of rotor incidence angle, penalizing the turbine efficiency and capability of generating a quasi-steady shaft torque. . Please refer to any applicable publisher terms of use.concepts. The European Ultra Low emission Technology Innovations for Mid-century Air-4 craft Turbine Engines (ULTIMATE) [1] addresses the prime gas turbine engine loss sources, 5 revealed by exergetic analysis [2], and investigates possible synergies arising from the combi-6 nation of radical technologies. One of the investigated gas turbine engine concepts comprises 7 an intercooled geared turbofan including a pulse detonation combustion (PDC) system [3]. 8 Pulsed detonation combustors burn fuel using an intermittent, periodically initiated, 9 detonation wave combining heat addition with a pressure increase. This should theoretically 10 result in a lower entropy increase than the conventional Joule-Brayton cycle. Pressure rise 11 combustion systems are believed to provide a theoretical improvement of 8 to 15% [3, 4, 5] 12 in the thermal efficiency of the power plant. 13Among many other very important engineering challenges, the theoretical potential of 14 integrating pulsed detonation combustion in a gas turbine is dependent on efficient integra-15 tion with a upstream compressor [6] and a downstream expansion system [7, 8, 9, 10, 11, 12]. 16The unsteady nature of pulsed detonation results in strong variations in mass flow, thermo-17 dynamic quantities, turbine rotor inlet angles [13], and can even lead to periods of reversed 18 flow [14]. The turbine is therefore subjected to rapid periodic changes in operating con-19 ditions and cannot be represented by a single point in a performance map [15]. This flow 20 behavior has a direct negative impact on the high pressure turbine efficiency, and can negate 21 the theoretical thermal efficiency improvements of detonation combustion. Moreover, irre-22 spective of the turbomachinery concept being investigated it is important to understand 23 how the non-stationary PDC shock-waves [16, 17], influence turbomachinery flows, in par-24 ticular during the early...

Review on the Rotating Detonation Engine and It’s Typical Problems

“…The throttling effect of turbine could affect the propagation of detonation waves, besides, the unsteady flow at the PDC outlet section can lead to pulsing inlet condition of the turbine. The relevant studies show that, the unsteady exhaust of the PDC could lead to local separation bubbles on the turbine blades, and further increase the boundary layer loss of the turbine [54]; the effects of unsteady flow from the PDC on the axial turbine efficiency is not significant if the PDC exhaust is mixed with the steady bypass flow [55]. The performance analysis of the axial flow turbine under high-amplitude, high-frequency pulsating flow conditions shows that the turbine efficiency is closely related to the corrected mass flow and mass flow averaged rotor blade intake angle [56][57].…”

An alternative architecture of the Humphrey cycle and the effect of fuel type on its efficiency

“…The strong variations of pressure, temperature, and velocity cause excessive aerodynamic losses and could negate all thermodynamic gains harvested from pressure-gain combustion. 35,36 A plenum can be used to condition the incoming flow in a turbine and minimize the aerodynamic losses in it. The current work systematically studies the trade-off between combustor pressure gain and the maximum allowable thermodynamic losses in this plenum.…”

“…On the other hand, conventional turbines experience a considerable drop of their isentropic efficiency, when they operate at the outlet of pressure‐gain combustors. The strong variations of pressure, temperature, and velocity cause excessive aerodynamic losses and could negate all thermodynamic gains harvested from pressure‐gain combustion 35,36 . A plenum can be used to condition the incoming flow in a turbine and minimize the aerodynamic losses in it.…”

Investigation of the Exhaust Flow of a Pulse Detonation Combustor at different Operating Conditions based on High-Speed Schlieren and PIV

“…Excessively high temperatures, the presence of shocks, and high pressure and temperature fluctuations produced by the inherent unsteady combustion process are undesirable for both the compressor upstream and the turbine downstream of the PDC. In Xisto et al [6] a PDC-turbine system is investigated revealing that the mismatch between the transient inlet flow conditions of the rotor and the constant blade speed results in a significant amount of losses. In their study the PDC was directly attached to the turbine without any additional devices in between.…”