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Advanced Fossil Fuel Power Systems
Published in D. Yogi Goswami, Frank Kreith, Energy Conversion, 2017
Alas, it is not possible to design a combustor with steady supersonic flow (Mach number of about 3–4) and a standing detonation wave in a land-based power generation turbine. The only possibility is to create detonation waves at a high frequency (say, tens of times per second) inside a semi-closed channel (tube) utilizing a suitable ignition system. The inherent unsteadiness of the practical detonation combustion led to the concept of intermittent or pulse(d) detonation combustion (PDC), which has been seriously investigated for aircraft propulsion systems for more than half a century [111]. In its most basic configuration, the resulting aircraft gas turbine engine, widely known as a pulse detonation engine (PDE), comprises a semi-closed multitubular combustion chamber in which detonations are created at a high frequency, for example, 80–100 times in a second, for practical flight units. For the application of PDC to land-based gas turbines for electric power generation, see references [76,79]. Realistic gas-dynamic calculations for the C-J detonation [76] suggest that the PR accompanying the TR in a PDC is much smaller than that suggested by the ideal CVHA (i.e., PR = TR). As shown in Figure 13.36, for the temperature ratio 2.58 in Table 13.9, a more realistic CVHA PR is 1.74. Substituting that value in the calculations, the equivalent Carnot efficiency becomes 76.4% (instead of nearly 80% in Table 13.9) and the implied GTCC efficiency with a CF of 0.782 is 59.7%–2.5% points lower than the “true” CVHA Brayton cycle efficiency in Table 13.9. Even so, the performance is still impressive: nearly 60% GTCC efficiency with E class TIT (cheaper materials, lower emissions).
Pulsejet and Ramjet Engines
Published in Ahmed F. El-Sayed, Aircraft Propulsion and Gas Turbine Engines, 2017
All regular jet engines operate on the deflagration of fuel—that is, the rapid but subsonic combustion of fuel. The PDE is a concept currently in active development to create a jet engine that operates on the supersonic detonation of fuel.
Experimental and numerical study of flame acceleration and DDT in a channel with continuous obstacles
Published in Combustion Theory and Modelling, 2023
An important manifestation of gaseous combustion is the spontaneous acceleration of a flame front, which is of great significance in combustion science and application [1,2]. The study of flame acceleration and deflagration-to-detonation transition (DDT) has a crucial role in both preventing explosions in confined spaces and ensuring the safe operation of engines with detonation-based propulsion [2–5]. For instance, if a methane-air mixture accidentally ignites in closed tunnels or chambers of a mine, damaging overpressure can build up as the flame accelerates down the shaft [1,6]. Under certain conditions, the flame can undergo a transition to detonation. In the combustor of a pulse detonation engine (PDE), a nearly constant-volume heat addition process occurs when the detonation traverses the chamber, creating high pressure in the combustion chamber and providing thrust. For the rotating detonation engine (RDE), DDT in the pre-detonation tube is important for the ignition and stabilisation of continuous detonation. Superior to the traditional deflagration mode, the detonation mode of combustion will minimise entropy generation and produce a net increase in stagnation pressure. Thus the promotion of flame acceleration and effective utilisation of the subsequent DDT are essential for the design and operation of PDE and RDE [4,5].
Spectra signals of gas pressure pulsations in annular and linear dual-slotted nozzles
Published in Combustion Science and Technology, 2019
Vladimir A. Levin, Natalia E. Afonina, Valeriy G. Gromov, Ivan S. Manuylovich, Aleksander N. Khmelevsky, Vladimir V. Markov
2-Stage PDE assumes injection of prepared (at the first stage) power-intensive medium into deflector cavity – gas dynamic resonator in which process of spontaneous ignition is periodically initiated and effective gas mixture detonation combustion takes place (at the second stage). Annular (or linear dual-slotted) nozzles with the internal deflector cavity in the form of a spherical (cylindrical) segment are considered as perspective for realization of pulsing, including the detonation, regime of fuels combustion (Levin et al., 2001; Taki and Fujiwara, 2004, 2006). The presence of a high-frequency pulsing flow mode in annular (or linear dual-slotted) nozzle is a necessary condition of 2-Stage fuels combustion technology realization. As shown in experiments (Levin et al. 1995, 2010, 2012, 2013, 2015, 2016; Leyva et al., 2003; Marchukov et al., 2006; McManus and Dean 2005; Nechaev et al., 2002; Zeng et al., 2015), there are different regimes of gas flow in such nozzle devices. In the steady-state regime, they belong to the class of nozzles with a central body. In unsteady periodic pulsed regimes, such nozzles are high-frequency pulsed output devices. The study of pressure pulsation signals is topical for determining the dependence of spectral composition pulsations from geometric nozzles parameters and their flow conditions in order to manage the process frequency. Pulsation frequency management is of interest at similar nozzle devices application to regulate frequency process of pulsing mode combustion in 2-Stage PDE.
Comparison between Ideal and Slot Injection in a Rotating Detonation Engine
Published in Combustion Science and Technology, 2018
S. Palaniswamy, V. Akdag, O. Peroomian, S. Chakravarthy
Detonation engines offer significant improvement in thermodynamic efficiency (Wolanski, 2011) over isobaric-combustor-based power plants due to near constant-volume combustion. Combustion occurs over very short distances and very high velocities (on the order of km/s) in detonation engines. Pulse detonation engines (PDEs) have been examined in great detail as thrust producing devices and as replacement for combustors in jet engines. However, the highly unsteady nature of combustion in PDEs makes them less than ideal for constant thrust production. A typical PDE cycle operates at tens of Hz. Most of the cycle duration is consumed by fill and purge operations. Inlet valves and exhaust nozzle are often used to improve the performance (Ma et al., 2006) of PDEs as thrust producing devices. A rotating detonation engine (RDE), on the other hand, offers the improved thermodynamic efficiency of a PDE while operating at thousands of Hz. Thrust from an RDE is nearly constant compared to that of a PDE.