Excessively Fuel-Rich Conditions for Cold Starting of Liquid-Fuel Pulse Detonation Engines

Numerical investigation of the liquid-fueled pulse detonation engine for different operating conditions

“…After stage 1, the results of two parameters (fuel/air equivalence ratio (fuel vapor mass fraction) and the mixture temperature) are very important for the successful DDT process [6][7][8][9][10][11][12]. There exists a certain range of pre-vaporization fuel/air equivalence ratio for successful DDT (detonation onset), while too lean or too rich of a fuel vapor mixture can cause failure in the DDT process.…”

“…For the OC3, Table 4 shows that the fuel vapor mass fraction is greater as the injected fuel mass flow rate is greater. The obtained fuel vapor mass For the liquid-fueled PDE with cold-starting, Li and coworkers [12], based on their experiments, have reported on the relation between the mixture temperature and global equivalence ratio to attain the vapor fuel/air equivalence ratio of about 1.0 to ensure the onset of detonation. In this work, we found that there is a range of the fuel/air equivalence ratio and average mixture temperature where the DDT still successfully transits to detonation (see Tables 2, 3, 4 for details).…”

“…The greater energy density of the liquid fuel can provide more power to the propulsion system. Due to the high potential benefit of implementation, numerous investigations of liquid-fueled detonation engines have been carried out for both the experimental and numerical studies [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. In particular, for experimental investigation, Webber [2] and Crammer [3] conducted research on spray detonations for a liquid-fueled rocket engine.…”

“…To attain the necessary pre-vaporization fuel level, Frolov [8] and Fan et al [9] conducted experiments on the DDT process by starting from room temperature and found the tube temperature that was deemed favorable for the liquid-fueled PDE, while Schauer et al [10] and Tucker et al [11] demonstrated an operational PDE of up to 15 Hz with the inlet air heated to the temperature of 123 and 149 °C (396.15 and 422.15 K), respectively. Recently, Li et al [12] have performed a series of experiments on excessively fuel-rich conditions for cold-starting the liquidfueled pulse detonation engine to establish the criteria for detonation transition of two-phase mixtures based on the PDE filling time and droplet life time, leading to a range of appropriate PDE operating parameters, such as droplet size, inlet air temperature, and PDE running frequency. They also concluded that successful detonation experiments using liquid fuels can be generally achieved when the vapor phase equivalence ratio is near-stoichiometric or slightly fuel rich.…”

“…In fact, a complete operating cycle of the detonation engine often involves three main processes: the injection and vaporization process, the deflagration-to-detonation transition process, and the detonation propagation process. Each of the sub-processes can be found in the published literature, such as atomization and droplet size effects [5], heat transfer [4], turbulence-chemistry mixing [18], evaporation process [19], incomplete reaction and reaction beyond the C-J plane [20], excessive fuel-rich conditions for cold-starting [12], and others, which are required in the three main processes in order to elucidate better and clearer physical and chemical insights of the complete operating cycle of a liquid-fueled detonation engine.…”