Pulse Detonation Research Articles

Explosion behaviors of vapor–liquid propylene oxide/air mixture under high-temperature source ignition

Propylene oxide (PO) is widely used in fuel–air explosive (FAE) and pulse detonation engines (PDE). The explosion process of PO/air mixture in a 20 L spherical container under high-temperature source ignition was studied through experiment and numerical simulation. A good agreement was observed between the experimental and simulation results. The ignition temperature (1100–2500 K) and initial droplet size (10–200 μm) had no obvious effect on the maximum explosion pressure (Pmax) at a nominal concentration of 130 g/m3. Explosion time (te) and reaction time (tr) of PO aerosol explosion increased with the increase in initial droplet size. The flame propagation process in the direction of 90° was not the same as that of 45°. Explosion flame propagated from the center to the surrounding area, then sagged along wall facing the center and presented a U-shape. Explosion time at ignition temperature of 1600 K was 29.63 ms, which was the shortest compared with the temperature of 2000 K, 2500 K, and 1100 K. The influence of ignition temperature on te was more obvious than that of initial droplet size. The flame propagation mechanism of droplet sizes of 10 μm and 50 μm was different from that of 100 μm and 200 μm. The time to reach the maximum flame temperature(tf) increased with the increase in droplet size; the flame propagation speed decreased with the increasing droplet size, and the maximum flame velocity can reach 6.07 m/s.

Effects of wedge-angle change on the evolution of oblique detonation wave structure

Compared to pulse detonation engine and rotating detonation engine, oblique detonation engine has the advantage of higher flight Mach number. However, it is still challenging to achieve stabilized oblique detonation wave for a broad range of flight conditions. To control oblique detonation wave, this study focuses on the oblique detonation wave structure evolution induced by changing the wedge angle. Transient two-dimensional simulations are conducted for wedge-stabilized oblique detonation wave in a stoichiometric hydrogen/air mixture. The detailed chemistry of hydrogen combustion is considered, and the thermal states of the reactants are determined by the specified flight altitude and the Mach number. The angle change between inflow and wedge can be achieved in two ways: inflow-angle change with fixed wedge angle and wedge-angle change with fixed inflow direction. Results indicate that no new autoignition zone exists in the transient wave evolution caused by wedge-angle change, which is different from that of inflow-angle change observed in previous studies. For the wedge-angle change process, the effects of wedge-angle change rate on transient oblique detonation wave structure evolution are further assessed. It is found that the transient oblique detonation wave structure is more sensitive to the wedge-rotation angular velocity for increasing wedge angle (controlled by the thermodynamic properties of the mixture) than that for decreasing wedge angle (controlled by the shock wave dynamic). For the quasi-steady triple-wave structure during wedge-angle decreasing process, a normal detonation wave occurs and becomes dominant in the wave structure evolution, whose formation mechanism is analyzed by the polar curve theory.

Flight Demonstration of Pulse Detonation Engine Using Sounding Rocket S-520-31 in Space

A detonation engine system is successfully demonstrated for the first time in space using sounding rocket S-520-31 of the Japan Aerospace Exploration Agency/Institute of Space Astronautical Science. Detailed flight results of an S-shaped pulse detonation engine (PDE) installed in the rocket are presented herein. The flight is conducted to confirm that the PDE and its system operate at scheduled sequences in space, confirm the reproducibility of the PDE cycle, and despin the rocket around its axis. It is confirmed that the PDE operated successfully for 14 cycles in space. The experimental plateau pressure of is of the calculated plateau pressure, which suggests that detonation occurred in 14 cycles. The pressure profiles of the cycles are similar, and the pressure integrals are , confirming the excellent reproducibility of the PDE cycle. A probability statistical approach assuming a Gaussian distribution is applied to determine the average angular acceleration difference between processes of the PDE operation, mixture supply, and oxygen supply. The results suggested that the PDE despun the rocket via the thrust produced via detonation combustion, which is consistent with a quasi-steady-state model with an accuracy of .

Pulsed Detonation Hydroramjet: Design Optimization

A new type of marine transportation engine, the pulsed detonation hydroramjet (PDH), which was first designed, manufactured, and tested by the present authors, has been further investigated in terms of the potential improvement of its propulsive performance. PDH is composed of a pulsed detonation tube (DT) inserted in the flow-through water guide. Thrust is developed by shock-induced pulsed water jets which are periodically emitted from the water guide nozzle. The measured values of the time-averaged thrust and specific impulse in the first operation cycle were shown to always be considerably higher than those in subsequent cycles, indicating the possibility of improving the overall thrust performance. The present manuscript is aimed at clarifying the reasons for, and eliminating, cycle-to-cycle variability during PDH operation, as well as optimization of the PDH design. An experimental model of the PDH with an optically transparent water guide was designed and manufactured. The cycle-to-cycle variability was found to be caused by the overexpansion of gaseous detonation products in the DT due to the inertia of water column in the water guide. Gas overexpansion caused the reverse flow of the gas–water mixture which filled the water guide and penetrated the DT, thus exerting a strong effect on PDH operation. To eliminate the cycle-to-cycle variability, a new PDH model was developed, manufactured, and tested. The model was equipped with a passive flap valve and active rotary valve and operated on the stochiometric propane–oxygen mixture. Its test firing showed that use of the valves made it possible to eliminate the cycle-to-cycle variability and nearly double the time-averaged thrust and specific impulse reaching 40 N and 550 s, respectively.

Prediction of detonation initiation in an air-breathing pulse detonation combustor utilizing a simplified ethylene-air reaction mechanism

In order to predict the detonation initiations accurately with less computational effort, a reduced method was proposed to establish a three-step ethylene/air global reaction mechanism for detonation combustors. The activation energy of the three-step mechanism was set as a key parameter that varies with the initial state of the reactants. A database of detonation simulation activation energy was established in a range of the equivalence ratio of 0.7–2.3 and the pressure ahead of the precursor shock front of 0.2–2.0 atm. Compared with existing simplified chemical reaction mechanisms, the proposed mechanism was confirmed to better reproduce the results of GRI-Mech3.0 within the given applicability range. The developed mechanism was used to predict the lean and rich limits of detonation initiation for simulation successfully in an air-breathing pulse detonation combustor. The simulation results were consistent with the theoretical limits estimated by the detonation cell sizes. Stable operation of an air-breathing detonation combustor was achieved in the experiments. Moreover, a series of equivalence ratio ranges of detonation initiation and the initiation distances were obtained. The simulated limits fell within the two experimentally obtained ranges of the lean limit and the rich limit. This proved that the established three-step mechanism is appropriate for the simulations of detonation initiation.

Suppression of pressure feedback of the rotating detonation combustor by a Tesla inlet configuration

With the increase in the inlet throat area, the rotating detonation combustor (RDC) can obtain higher pressure gain. However, the pressure feedback caused by the rotating detonation wave (RDW) can affect the upstream components of combustion chamber and interfere with the stable operation of RDC. Therefore, to obtain outstanding performance, it is imperative to investigate the suppression of pressure feedback. In this study, kerosene and 28.5% oxygen-enriched air (at room temperature) were taken as the propellant, and the tesla valve inlet configuration was applied to RDC, and the effect was compared with that of the traditional inlet configuration to suppress pressure feedback. A series of experiments were conducted to examine the operation characteristics of Tesla RDC and the effect and mechanism of suppressing pressure feedback. Under similar conditions, Tesla RDC can effectively transform the longitudinal pulsed detonation (LPD) mode into the rotating detonation (RD) mode, thus expanding the operating range of RDC. RDC under the exit nozzle with a small area ratio (0.25) was successfully realized. The operating range of Tesla RDC can be expanded by 300% and 94.7% at an exit area ratio of 0.5 and 0.65, respectively. The bypass channel in Tesla valve inlet configuration is the key to expanding the operating range. Directing pressure feedback to the bypass channel can effectively weaken the influence on the main inlet channel and shorten the inlet recovery time. Two quantitative evaluation indexes of pressure feedback were established; one is the percentage of the pressure fluctuating amplitude in the air plenum to the pressure amplitude of the detonation wave (PFdw), and the other is the static pressure of the air plenum, PFap. By analyzing the dynamic pressure signal upstream of the combustor, it was found that pressure disturbance is in the form of a pressure wave during the upstream return of the combustor, and the return speed is close to the local sound speed. Pressure feedback is mainly suppressed at the inlet throat, and PFdw is reduced by approximately 14% due to drainage of the bypass channel. Tesla RDC exhibits a good suppression effect on LPD mode, PFdw is significantly lower in the large exit nozzle area ratio, and the minimum value is 23%. PFap has an approximately linear relationship with the equivalence ratio, and the minimum value is 7.7%. Overall, this study demonstrates that Tesla RDC has excellent potential in widening the operation range and suppressing the pressure feedback, providing an innovative method for improving the performance of RDC.

Experimental study of the influence of annular nozzle on acoustic characteristics of detonation sound wave generated by pulse detonation engine

Acoustic characteristics of the detonation sound wave generated by a pulse detonation engine with an annular nozzle, including peak sound pressure, directivity, and A duration, are experimentally investigated while utilizing gasoline as fuel and oxygen-enriched air as oxidizer. Three annular nozzle geometries are evaluated by varying the ratio of inner cone diameter to detonation tube exit diameter from 0.36 to 0.68. The experimental results show that the annular nozzles have a significant effect on the acoustic characteristics of the detonation sound wave. The annular nozzles can amplify the peak sound pressure of the detonation sound wave at 90° while reducing it at 0° and 30°. The directivity angle of the detonation sound wave is changed by annular nozzles from 30° to 90°. The A duration of the detonation sound wave at 90° is also increased by the annular nozzles. These changes indicate that the annular nozzles have an important influence on the acoustic energy distribution of the detonation sound wave, which amplify the acoustic energy in a direction perpendicular to the tube axis and weaken it along the direction of the tube axis.

Air-argon dual loop gas turbine engine with pulse detonation combustion and water injection

Air-argon dual loop gas turbine engine with pulse detonation combustion and water injection

Natural Gas Conversion and Organic Waste Gasification by Detonation-Born Ultra-Superheated Steam: Effect of Reactor Volume

The pulsed detonation (PD) gun technology was applied for the autothermal high-temperature conversion of natural gas and atmospheric-pressure oxygen-free allothermal gasification of liquid/solid organic wastes by detonation-born ultra-superheated steam (USS) using two flow reactors of essentially different volume: 100 and 40 dm3. Liquid and solid wastes were waste machine oil and wood sawdust, with moisture ranging from 10 to 30%wt. It was expected that decrease in the reactor volume from 100 to 40 dm3, other conditions being equal, on the one hand, should not affect natural gas conversion but, on the other hand, could lead to an increase in the gasification temperature in the flow reactor and, correspondingly, to an increase in the product syngas (H2 + CO) quality. The PD gun was fed by natural gas–oxygen mixture and operated at a frequency of 1 Hz. As was expected, complete conversion of natural gas to product syngas in the PD gun was obtained with H2/CO and CO2/CO ratios equal to 1.25 and 0.25, irrespective of the reactor volume. Liquid and solid wastes were gasified to H2, CO, and CH4 in the flow reactors. The steady-state H2/CO and CO2/CO ratios in the syngas produced from waste machine oil were 0.8 and 0.5 for the 100-dm3 reactor and 0.9 and 0.2 for the 40-dm3 reactor, respectively, thus indicating the expected improvement in syngas quality. Moreover, the maximum mass flow rate of feedstock in the 40-dm3 reactor was increased by a factor of over 4 as compared to the 100-dm3 reactor. The steady-state H2/CO and CO2/CO ratios in the syngas produced from the fixed weight (2 kg) batch of wood sawdust were 0.5 and 0.8 for both reactors, and the gasification time in both reactors was about 5–7 min. The measured H2 vs. CO2 and CO vs. CO2 dependences for the syngas produced by the autothermal high-temperature conversion of natural gas and atmospheric-pressure allothermal gasification of liquid/solid organic wastes by USS at f = 1 Hz were shown to be almost independent of the feedstock and reactor volume due to high values of local instantaneous gasification temperature.

Numerical study on detonation initiation process in the chamber with characteristic structures of the dual-mode scramjet combustor

In order to improve the performance of traditional ramjet, a ramjet based on pulse detonation (PD-Ramjet) instead of isobaric combustion was proposed. Several special-shaped detonation chambers which retained the characteristic structures of the dual-mode scramjet combustor were designed. Characteristic structures included the expansion channel and the cavity. The filling process and detonation initiation process of the stoichiometric hydrogen/air mixture under the incoming flow condition of the sub-combustion mode were studied in the detonation chambers with characteristic structures by two-dimensional numerical simulation method, and the influences of the characteristic structures on the filling process and detonation initiation process were analyzed. The simulation and analysis results indicated that the hydrogen concentration at both sides of the chamber near the outlet was low due to the structure of the expansion channel, and the pressure and velocity of the detonation wave decreased gradually after the expansion channel. The cavity had a significant influence on the filling process, which resulted in the uneven hydrogen concentration downstream the cavity, especially near the outlet of the chamber. The intensity of the detonation wave attenuated to a certain extent by reason of the cavity, where the peak pressure first decayed due to the sudden expansion of the flow path and then rose owing to the reflection at the cavity aft wall.

Suppression of the back-propagated pressure waves originated from a liquid-fueled valveless pulse detonation combustor with combined aero-valves

In order to seek out a way to isolate the back-propagated pressure waves originated from a valveless pulse detonation combustor (PDC), a liquid-fueled single tube PDC was designed and tested at frequencies ranging from 10 Hz to 30 Hz with different types of aero-valve installed at the air inlet such as wedge-shaped aero-valves, reflux-typed aero-valves and combined valves. The damping ability of the aero-valves were quantified and compared. Then, an isolator was designed and combined with the optimized aero-valves to isolate the back-propagated pressure waves. The experimental results show that both the wedge-shaped aero-valve and the reflux-typed aero-valve could reduce the peak value of the back-propagated pressure waves and the pressure oscillation at the air inlet. The largest pressure oscillation was reduced from (74.7 ± 3.35)% to (25 ± 1.84)% when three wedge-shaped aero-valves was installed at the inlet section, while the pressure oscillation was only (22.3 ± 2.9)% with three reflux-typed aero-valves. What's more, the pressure oscillation at the air inlet could be further reduced with the combination of the wedge-shaped aero-valve and the reflux-typed aero-valve. The combined structure 6 (one wedge-shaped aero-valve + two reflux-typed aero-valves) was the most effective way to reduce the pressure oscillations at the air inlet even though the peak value of the back-propagated pressure waves at the air inlet for the combined structure 6 were the highest. When an isolator was installed on the base of the combined structure 6 and the structure F (three reflux-typed aero-valves), the back-propagated pressure waves could be isolated under the case of high inlet total pressure such as a firing frequency of 30 Hz. But there are still pressure oscillations for the firing frequencies lower than 25 Hz because of that there is no supersonic region in the air inlet or the Mach number of supersonic regions is very small at low firing frequencies.

Spinning pulsed detonation in rotating detonation engine

Experiments are conducted on a rotating detonation engine fed by Hydrogen and Air. Spinning pulsed detonation mode is identified for the first time. Characterized by evident spiral and pulsed features, this mode exhibits two distinctive types: single-wave pattern where one circumferentially propagating transverse wave is attached to a longitudinal pulsed detonation and two-wave pattern where two circumnavigating transverse waves are attached to a longitudinal pulsed detonation. The inception, sustenance, and transition of this novel mode are described and analyzed. Moreover, a propagation mechanism for spinning pulsed detonation mode is proposed by analogy with that of different detonation phenomena, i.e., spinning detonation wave in a round tube and rotating detonation wave in an RDE. A trade-off relationship between the longitudinal pulsed detonation and the attached transverse wave is reflected in spinning pulsed detonation mode, explaining the prevalent mode switch between longitudinal pulsed detonation mode and rotating detonation mode in RDEs. The validity of this proposed propagation mechanism is verified by the data of pressure signals and high-speed photography.

Performance analysis of a hybrid pulse detonation engine using liquid hydrogen as fuel

Aimed at enhancing the comprehensive performance of the air turbo rocket engine (ATR), two schemes of hybrid pulse detonation engine (PDE) configurations based on the ATR were proposed. The engines are fueled by liquid hydrogen, and the oxidant is the incoming air or self-carried liquid oxygen. The ideal thermodynamic cycle processes of the engines were analyzed, and the relevant mathematical models were established. The fuel pump pressure ratio of the ATREX and the oxidant-fuel ratio of the ATR-GG are respectively used as iterative variables. The performances of the two engine schemes at the design point were obtained and compared with that of the traditional ATR. The results show that, under ideal conditions, the specific thrust and specific impulse of the hybrid PDE based on the ATREX are about 20% higher than those of the traditional ATREX. Moreover, the mass of the oxidant required by the hybrid PDE based on the ATR-GG is about 49.5% lower than that of the traditional ATR-GG, while the specific thrust and specific impulse are not reduced as compared with those of the traditional ATR-GG.

Numerical studies on interactions between a centrifugal compressor and the back-propagated pressure waves originated from a pulse detonation combustor

In order to investigate the influence of the back-propagated pressure waves originated from a pulse detonation combustor on the operating characteristics of the compressor in the pulse detonation turbine engine, a model consist of a centrifugal compressor and an isolation section which was usually utilized to decrease the peak value of the back-propagated pressure waves was set up. Numerical simulations were carried out to study the interactions between the centrifugal compressor and the back-propagated pressure waves under different operating conditions. The matching characteristics of the compressor under the influence of the back-propagated pressure waves were analyzed in a detonation cycle. The results showed that the back-propagated pressure waves would push the shock wave in the isolator towards the throat position, but the shock wave did not pass through the throat for the compressor corrected speed of n = 100% and n = 105%. For these two cases, the back-propagated pressure waves were completely isolated and the operating characteristics of the compressor were the same as those under the steady outlet conditions. For the corrected speed of n = 50% and n = 90%, the shock wave in the isolator section was pushed out of the throat and the supersonic flow in the isolator section was destroyed under the influence of the back-propagated pressure waves. The back-propagated pressure waves would propagate upstream into the compressor. Consequently, the instantaneous mass flow rate and the torque acting on the centrifugal impeller was decreased. The work required by the compressor was also reduced. The equivalent isentropic efficiency of the compressor was decreased. The separation or backflow in the compressor caused by the back-propagated pressure waves would results in an equivalent isentropic efficiency loss of 3.2% points for the case of n = 90% and 15.6% points for the case of n = 50%.

Experimental study of pulse detonation engine with liquid ethanol and oxygen mixtures

Experimental study of pulse detonation engine with liquid ethanol and oxygen mixtures

Natural Gas Conversion and Liquid/Solid Organic Waste Gasification by Ultra-Superheated Steam

The technology of a pulsed detonation gun for gasification of organic waste with ultra-superheated steam has been experimentally demonstrated for the first time. Experiments were performed on natural gas conversion as well as on the gasification of liquid (waste machine oil) and solid (wood sawdust) waste by hot detonation products of natural gas–oxygen mixture at a frequency of detonation pulses f = 1 Hz. Periodic release of detonation products to a 100 L flow reactor provided a time-averaged mean temperature and pressure in the reactor at about 1200 K and 0.1 MPa. It is shown that the technology of a pulsed detonation gun can provide complete (100%) natural gas conversion to syngas containing H2 and CO with a H2/CO ratio of 1.25. During the gasification of liquid and solid wastes, the total volume fraction of combustible gases (H2, CO, and CH4) in the product syngas was 80 and 65% with H2/CO ratios of 0.8 and 0.5, respectively. Comparison of the experiments on natural gas conversion and liquid/solid organic waste gasification under the same conditions at f = 1 Hz showed that the composition of the product syngas in terms of H2 and CO content almost did not depend on the type of used feedstock. The estimated ideal energy gain defined as the ratio of the total energy of product syngas to the energy spent in its production from dry wood sawdust is about 4.6, i.e., the pulsed detonation technology of biomass gasification is economically very attractive.

Experimental study of H2/air rotating detonation wave propagation characteristics at low injection pressure

H2/air rotating detonation wave (RDW) propagation characteristics were studied under low injection pressure. A small air mass flow rate and wide air injection ring were used to obtain low injection pressure. The formation of RDWs and the influence of different injection pressures on the RDW propagation process were studied and analyzed. The experimental results show that the lower limit of injection pressure for H2/air to form an RDW with stable propagation is 2.21 bar for hydrogen and 2.32 bar for air. At these injection pressures, the longitudinal pulsed detonation (LPD) mode and the single rotating detonation wave (SRDW) mode occur successively in the rotating detonation combustor (RDC), and the RDW velocity is 1491.4 m/s. The reasons for the generation, persistence and transformation of the LPD are analyzed. When the air mass flow rate is 370 g/s, the minimum air injection pressure to produce RDC ignition in a wide equivalence ratio range is 3.0 bar. With an equivalence ratio of 0.57–1.54, the RDW velocity and pressure first increase and then decrease, the maximum RDW velocity and pressure occur with an equivalence ratio of 1.2–1.3. RDW velocity and pressure increase with the air injection pressure rises. Flame characteristics during steady RDW propagation were analyzed using high-speed photography.

Experimental research on operation performance and acoustic behavior of two-phase dual-tube pulse detonation engine

In order to research the operation synchronous of dual-tube pulse detonation engine, the operation performance and acoustic behavior of dual-tube pulse detonation engine under different fill fractions are studied experimentally. The results show that the instability of deflagration to detonation transition is the main reason for the non-synchronous work of the two tubes. With the increase of fill fraction, the detonation sound pressure increases gradually. In the region near the tube exit, the pressure and velocity of the shock wave attenuate rapidly, and the attenuation speed gradually slows down while the propagation distance increases. The time interval of detonation waves arriving at the tube exit of the two tubes can significantly affect the peak sound pressure and the duration of the sound wave outside the tube. With the increase of time interval, the peak sound pressure decreases and the total duration as well as the duration of the positive pressure increase. The synchronization of the working process of the dual-tube pulse detonation engine can be diagnosed by analyzing the pressure and duration of the sound wave outside the tube. The research results in this paper have certain reference significance for improving the synchronous of multi-tube pulse detonation engine and will be useful for the application of multi-tube pulse detonation engine in aircraft power system.

Numerical study of back-propagation suppression and intake loss in an air-breathing pulse detonation engine

In order to reduce the back-propagation pressure and the back-propagation distance of burnt gas in the air-breathing pulse detonation engine effectively, two back-propagation suppression structures were proposed in this paper. The influences of channel width (D) and unit length (L) in the corresponding back-propagation suppression structure on the intake loss and the back-propagation characteristics were studied by the 2-D numerical simulation which was based on stoichiometric propane/air mixture to obtain the optimal structure. The grid independence and the reliability of numerical simulation were verified. The simulation results indicated that the back-propagation suppression structure with a flow channel formed by the annular cavities and the convergent sections was the structure with the optimal back-propagation suppression performance. And the following two methods were proved to be effective in this paper. By the means of propagating the pressure wave along the arc-shaped channel, the propagation distance of the pressure wave increased, which resulted in an attenuation of the back-propagation pressure. And the back-propagation pressure was reduced by the way of making the pressure wave propagate toward the downstream of the engine after colliding with the wall of the annular cavity and offsetting with the expansion wave.

Analytical Assessment of Blended Fuels for Pulse Detonation Engine Performance

A pulse detonation engine (PDE) is possible to be a next-generation high-performance propulsion system in aerospace-related applications. To generate power or thrust, PDE uses repeated detonations. The current study evaluates the PDE performance with alternative and blended fuels in the Zeldovich–von Neumann–Doring (ZND) model. Parameters such as temperature ratio, pressure ratio, detonation velocity, and specific impulse were determined analytically for the fuels. The computed detonation parameters and specific impulse were compared with those available in NASA’s open-source program, Chemical Equilibrium with Applications (CEA), to ensure the results' sufficient validity. It was found that the highest specific impulse was achieved with hydrogen at an equivalence ratio of 1. Analytical values of all the parameters were in an acceptable range as defined by NASA CEA. As compared to pure butane and propane, their blends yielded higher values (1 to 10 percent) of specific impulse. Propane and butane are safe, non-toxic, clean-burning fuels, great energy sources, and can be used as alternative fuels in PDE.