A large-scale continuous detonation combustor (CDC) has been designed, fabricated and tested to study the effect of different design elements on the operation process and CDC propulsion performance. ...It has been shown experimentally that widening of the air-inlet slit in the annular combustion chamber from 2 to 15 mm leads to a decrease in the number of detonation waves (DWs) simultaneously circulating in the combustor from four to one and, finally, to transition to the operation mode with intermittent (pulse) longitudinal reaction waves resembling pulse detonations. The number of DWs and the thrust produced by the CDC can be increased by installing a shaped obstacle at the CDC exit nozzle providing the blockage of the combustor cross section. The maximum net thrust produced by the CDC attained 6 kN at the total mass flow rate of fuel components of 7.5 kg/s, whereas the maximum fuel-based specific impulse attained ∼3000 s.
•We conduct experiments in a large-scale continuous-detonation combustor operating on hydrogen–air mixture.•We vary a size of air-inlet slit to observe changes in operation process and propulsion performance.•Widening of slit from 2 to 15 mm leads to decrease in a number of rotating detonation waves and to detonation failure.•Maximum fuel-based specific impulse obtained in experiments is 3000 s.
Deflagration-to-detonation transition (DDT) in gas (oxygen)-liquid n-heptane film and gas (oxygen)-liquid n-decane film systems is registered experimentally using a fused or exploding wire as a weak ...ignition source that generates a primary shock wave with a Mach number ranging from 1.02 to 1.6. In a straight smooth-walled channel of rectangular cross section 54 × 24 mm, 3 and 6 m long with one open end, the DDT is obtained at distances 900 to 4000 mm from the ignition source 3 to 1700 ms after ignition. The DDT is obtained for n-heptane and n-decane films 0.2 to 0.7 mm thick, which corresponds to the overall fuel-to-oxygen equivalence ratios of 15 to 40. The registered detonation velocities range from 1400 to 2000 m/s. In several experiments, a high-velocity quasi-stationary deflagration front propagating at an average velocity of 700-1100 m/s is recorded. The structure of this front includes the leading shock wave followed by the reaction zone separated from each other by a time delay of 90 to 190 μs. The results obtained are important for explosion safety and for better understanding of the operation process in the continuous-detonation and pulse-detonation combustors of advanced rocket and air-breathing engines with the supply of liquid fuel in the form of a wall film.
Experiments are performed on continuous detonation combustion of ternary hydrogen–liquid propane–air mixture in a large-scale annular combustor 406 mm in outer diameter with an annular gap of 25 mm. ...Liquid propane is fed into the combustor at the time when sustained continuous-detonation combustion of hydrogen–air mixture is attained therein. Mass flow rates of hydrogen, propane and air in the experiments ranged from 0.1 to 0.5 kg/s (hydrogen), 0.1 to 0.5 kg/s (propane), and 5 to 12 kg/s (air). Continuous-detonation combustion of liquid propane in air is obtained for the first time due to addition of hydrogen rather than due to enrichment of air with oxygen. Combustor operation with a single continuously rotating detonation wave (DW) for about 0.1 s has been obtained when the flow rates of propane and air remained constant while the flow rate of hydrogen was rapidly decreasing.
•We conduct experiments on continuous detonation of H2–liquid propane–air mixture.•We use hydrogen as an initiating fuel.•Continuous detonation of liquid propane is obtained for the first time with hydrogen as an additive.
•We study pulsed detonations of ternary C3H8/CH4–O2–steam mixtures at 0.1 MPa.•Maximum steam dilution in initial mixtures is 60% for C3H8 and 40% for CH4.•Maximum steam content in the detonation ...products expanded to 0.1 MPa attains 80%.•Steam temperature in expanded detonation products exceeds 2250 K.•Steam produced by pulse detonations can be used for clean waste gasification to syngas.
It is proposed to produce highly superheated steam (HSS) for environmentally friendly steam assisted gasification of organic municipal and industrial wastes using cyclic detonations of ternary propane/methane–oxygen–steam mixtures. Systematic experiments to determine the detonation limits of such mixtures in terms of steam dilution have been conducted. The experiments are performed in an innovative pulse-detonation steam superheater (PDSSH) with cyclic detonations of ternary mixtures at variation of fuel-to-oxygen equivalence ratio (from 0.14 to 1.77 in propane mixtures and from 0.3 to 1.84 in methane mixtures) and steam volume fraction (from 0 to 0.7) at normal atmospheric pressure. The experiments are supplemented by thermodynamic calculations. Cyclic detonations of ternary propane/methane–oxygen–steam mixtures are proved to generate HSS with temperature exceeding 2250 K, when expanded to the atmospheric pressure. The detonation products of stoichiometric ternary mixtures under consideration can contain up to 80% HSS and up to 17% CO2 with trace amounts of CO, O2 and H2. As a result of deep processing (gasification) of organic wastes by such products a gaseous mixture of CO and H2 is obtained, which can be further used as a fuel gas for PDSSH operation, heat/electricity production, and as a raw material for production of methanol and synthetic motor fuels. Due to periodic filling of the PDSSH with the cool ternary gas mixture, the temperature of PDSSH walls and inner elements increases insignificantly, so that conventional (not heat-resistant) construction materials can be used for its production.
The previously proposed experimental method for evaluating the detonability of fuel–air mixtures, based on measuring the run-up distance and/or run-up time of deflagration-to-detonation transition ...(DDT) in a standard pulsed detonation tube, was applied to study the DDT in the stoichiometric air mixtures of the binary methane–hydrogen fuel with a volume fraction of hydrogen ranging from 0 to 1 under the fixed thermodynamic and gasdynamic conditions. Based on the known data on combustion and self-ignition of such a fuel, it was expected that the DDT run-up distance and time should gradually decrease with hydrogen concentration. Contrary to expectations, the dependences of DDT run-up distance and time on the volume fraction of hydrogen turned out to be nonmonotonic: instead of a monotonic decrease, they reach local maxima.
•DDT in CH4–H2-air mixtures with H2 content ranging from 0 to 1 is studied.•Measured DDT run-up distance and time are shown to reach local maxima.•This finding is proved to reflect physicochemical properties of such mixtures.
The results of systematic experiments on deflagration-to-detonation transition (DDT) in homogeneous ethylene–hydrogen–air mixtures at normal pressure and temperature conditions are reported. ...Experiments are performed in a pulse-detonation tube of three different configurations with one open end. Hydrogen content and fuel-to-air equivalence ratio in the mixture are varied from 0 to 100% and from 0.5 to 3.5, respectively. The measured DDT run-up distance and time are shown to sharply decrease only at hydrogen content exceeding 70%vol. in the tube of all three configurations. The observed effect is explained by multidirectional influence of hydrogen addition on the mixture physicochemical properties relevant to the DDT phenomenon.
•The objects of research are ethylene–hydrogen–air mixtures with hydrogen content from 0 to 1.•Detonability of such mixtures in terms of DDT run-up distance and time is studied experimentally.•DDT run-up distance and time are found to sharply decrease at hydrogen content above 70%.•Similarity of results for alkane and alkene fuels indicates the determining role of hydrogen properties.
The possibility of organizing a continuous-detonation combustion of a liquid fuel film in an annular combustor of a detonation liquid-propellant rocket engine has been demonstrated. The near-limit ...mode of the longitudinally pulsating "film" detonation and the continuous spinning "film" detonation modes with one and two detonation waves circulating in the annular gap of the combustor are recorded in the fire tests.
It is found that the determining factor for the catalytic ignition of mixtures of hydrogen with ethane and ethylene is not only the material of the catalyst but also the chemical nature of the C
2
...hydrocarbon in the mixture with H
2
. It is shown that the limits of the catalytic ignition of the synthesis gas over metallic rhodium (Rh) are qualitatively different from the dependences for a hydrogen–hydrocarbon mixed fuel. The dependence of the lower limit of catalytic ignition on temperature has a distinct maximum, which indicates a more complex mechanism of the catalytic process than in the case of hydrogen–methane mixtures; the Arrhenius dependence of ln H
2
lim
on 1/
T
does not hold. Therefore, the interpretation of the upper and lower limits of catalytic ignition (ULCI, LLCI) used in the literature, taking into account catalyst poisoning by CO molecules, needs to be clarified. The relatively long delay periods of the catalytic ignition of hydrogen–
n
-pentane mixtures (tens of seconds) and the absence of dependence of the delays on the initial temperature allow us to conclude that the catalytic ignition of hydrogen–propane/
n
-pentane mixtures is determined by the rate of transfer of hydrocarbon molecules to the surface of the catalytic wire. Thus, in the oxidation of hydrogen–hydrocarbon mixtures for “short” hydrocarbons, the main factor determining the catalytic ignition is the oxidation reaction of hydrogen on the catalytic surface. With an increase in the number of carbon atoms in the hydrocarbon, the factors associated with the chemical structure, i.e., the reactivity of the hydrocarbon in catalytic oxidation, begin to play a significant role; and then the rate of oxidation is determined by the rate of transfer of the hydrocarbon molecules to (or within) the catalyst surface.
The values of the ignition temperature are experimentally determined and the effective activation energies of the limits of catalytic ignition of mixtures ((40–70%) H
2
+ (60–30%) CH
4
)
stoich
+ air ...over metallic rhodium at a pressure of 1.7 atm in the temperature range of 20 to 300°C are estimated. Above the rhodium surface treated with ignitions, the catalytic ignition temperature of a mixture of 70% H
2
+ 30% CH
4
+ air is 62°C, which indicates the possibility of using rhodium to significantly reduce the ignition temperature of fuels based on hydrogen-methane mixtures. The critical nature of the implementation of the bulk reaction is experimentally discovered: the bulk process occurs at H
2
= 45%, but is absent at hydrogen concentrations of ≤40%. If H
2
≤ 40%, only a slow surface catalytic reaction occurs. This phenomenon is illustrated by a qualitative calculation. It is established that the effective activation energies of both the upper and lower limits of the catalytic ignition of stoichiometric mixtures of H
2
+ CH
4
in the linearity range are approximately (2.5 ± 0.6) kcal/mol. This means that the key reactions responsible for the occurrence of the upper and lower limits of catalytic ignition are the same. It is shown that, in the case of catalysis with a rhodium catalyst, the chain propagation process is most likely of a heterogeneous nature, since the effective activation energy is less than 3 kcal/mol.
The air-breathing pulsed detonation thrust module (TM) for an aircraft designed for a subsonic flight at a speed of up to 120 m/s when operating on a standard aviation kerosene was developed using ...the analytical estimates and parametric multivariant three-dimensional (3D) calculations. The TM consists of an air intake with a check valve, a fuel supply system, a prechamber-jet ignition system and a combustion chamber with an attached detonation tube. An experimental sample of TM was fabricated, and its firing tests were carried out on a test rig with a thrust-measuring table. In firing tests, TM characteristics are obtained in the form of dependencies of effective thrust, aerodynamic drag and fuel-based specific impulse on fuel consumption at different speeds of the approaching air flow. It has been experimentally shown that the fuel-based specific impulse of the TM reaches 1000-1200 s, and the effective thrust developed by it reaches 180–200 N.
