Pulse Detonation Engine Research Articles

Numerical simulation of the nozzle and ejector effect on the performance of a pulse detonation engine

Single-shot pulse detonation engine (PDE) with three different types of nozzles-straight ejector combinational structures at three different ejector positions were simulated by the unsteady 2-D axisymmetric method. Three types of nozzles included the straight nozzle, convergent nozzle and convergent-divergent nozzle. Propane was used as the fuel and air as the oxidizer. The simulation results indicated that the PDE with a straight nozzle and PDE with a convergent-divergent nozzle obtained improved performance when an ejector was added at all of the three ejector positions (x /d = –1, 0 and +1), and PDE with a convergent-divergent nozzle gained the larger improved performance at all the three ejector positions. The PDE with a convergent nozzle-ejector combinational structure obtained the slightly worse performance at the ejector position of x /d = –1, gained the slightly increased performance at the ejector position of x/d = 0, and achieved the largest impulse augmentation and the second largest ejection ratio at the ejector position of x /d = +1 among all of the nine cases of the nozzle-ejector combinational structures. Ejector position of x /d = +1 was the best ejection position at which the PDE with a convergent nozzle-ejector combinational structure achieved the best propulsion performance, ejector position of x /d = –1 was the best ejector position for the PDE with a convergent-divergent nozzle-ejector combinational structure, and ejector position of x /d = 0 was the best ejector position for the PDE with a straight nozzle-ejector combinational structure.

Numerical simulation and performances evaluation of the pulse detonation engine

A pulse detonation engine (PDE) is a type of propulsion system that uses detonation waves to combust the fuel and oxidizer mixture. The engine is pulsed because the mixture must be renewed in the combustor between each detonation wave. Theoretically, a PDE can operate from subsonic up to hypersonic flight speed. Pulsed detonation engines offer many advantages over conventional propulsion systems and are regarded as potential replacements for air breathing and rocket propulsion systems, for platforms ranging from subsonic unmanned vehicles, long range transports, high-speed vehicles, space launchers to space vehicles. The article highlights elements of the current state of the art, but also theoretical and numerical aspects of these types of unconventional engines. This paper presents a numerical simulation of a PDE at h=10000 m with methane as working fluid for stoichiometric combustion, in order to find out the detonation conditions.

Evaluation of critical blockage ratio and pulse length in a pulse detonation engine using CFD and MATLAB

A Pulse Detonation Engine (PDE) is a new invented propulsion device that takes advantage of the pressure rise inherent to the efficient burning of fuel-air mixtures via detonations. Detonation initiation is a critical process that occurs in the cycle of a PDE. A practical method of detonation initiation is Deflagration-to-Detonation Transition (DDT), which describes the acceleration of a subsonic deflagration created using low initiation energies to a supersonic detonation. The DDT process is not well understood due to a wide range of time and length scales involving complex chemistry, turbulence and unsteady pressure waves. This paper discuss about the effects of blocking ratio in the augmentation of detonation pressure and velocity inside a cylindrical tube of diameter 0.0254m and a length of 1 m. The blockages are rectangular in shape placed at 2/3rd distances of the length of the tube and the heights of the blockages are varied in terms of the diameter of the tube as 1/4th, 1/3rd, ½, 2/3rd and 3/4th the diameter of the tube. The setup is then analyzed in MATLAB using the physics of Friedlander’s equation, which formulate the decay time duration of pressure across the tube length, with and without the blockage. Further, a 2D CFD analysis through ANSYS Workbench is conducted which gave the effective blocking ratio in a rectangular type of blockage placed at the 2/3rd position of the length of the tube and the results are compared. For variable pressures ranging from 1 MPa to 100 MPa input, the effective pulse length is around 0.25 seconds after which the decay of pressure and temperature attain the critical limit. Also it is found that the maximum feasible velocity occurs for an inlet pressure of 10 MPa and 2/3rd height of the blockage where the corresponding outlet velocity is 4692m/s and outlet total pressure being 10.542 MPa.

A preliminary heat transfer analysis of pulse detonation engines

Abstract Detonation engines offer higher theoretical thermal efficiencies as compared to their deflagration-based counterparts. Simultaneous pressure gain during heat addition through the detonation wave provides the superiority to the Zeldovich-von Neumann-Dring (ZND) cycle which is used to define the thermodynamic process of detonation engines. Combustion temperatures can rise as high as 3000 K across the detonation wave. The continuous exposure to such elevated temperature may risk the integrity of the structural components of the engines. Consequently, heat management of the detonation engines highlights an important parameter on the construction of a demonstrator. In order to be able to design an appropriate cooling system, both for pulse detonation and rotating detonation engines (PDE & RDE), an accurate estimation of the heat load stands as an essential prerequisite. Hence, a preliminary numerical study of the heat transfer on a pulse detonation engine model was conducted to quantify the heat load. Conservation equations for deflagration-to-detonation transition (DDT) in detonation engines were solved through open source fluid dynamics solver OpenFOAM equipped with ddtFoam module. Reactive flow field of premixed mixtures (Hydrogen-air) was modeled with a URANS second-order approximate Riemann solver equipped with Weller combustion model, and Arrhenius equations of O’Connaire reaction scheme for Hydrogen-air detonation. Multiple boundary conditions were tested to achieve the most appropriate model. Natural convection over the lateral combustor peripheries found to be the most realistic boundary condition for the problem. In order to observe cooling process better, PDE tubes in different length were also simulated. Finally, the transient heat transfer phenomenon across the pulse detonation tube is documented for various conditions investigated.

Laser intensity and absorbance measurements by tunable diode laser absorption spectroscopy based on non-line fitting algorithm

A novel approach to using tunable diode laser absorption spectroscopy (TDLAS) is developed for measuring the laser intensity and absorbance of gas with highly broadened and congested spectra by wavelength division multiplex (WDM) technology. Direct absorption spectroscopy with non-linear algorithm is utilized, because this fitting method offers benefits in dealing with blended spectral features according to the relationship between transmitted laser intensity and absorbance by Beer law. Compared with traditional TDLAS sensing with WDM, this approach has some advantages of transmissions demultiplexing without additional optic gratings and detectors. Following the published theory, the absorbance and transmitted laser intensity are incorporated into an improved non-linear fitting model. A solution to a simulation of CO2 blended spectrum at a pressure of 5 atm is exploited to demonstrate the ability to recover the absorption in a high pressure environment, inferring the optimal combination of parameters in the model. The influences of these nonideal laser effects, such as nonlinear and linear coefficients, are investigated by the multiplexed transmission simulations at rovibrational transitions of H2O near 7444 cm-1 and 7185 cm-1. Errors in absorbance fitting is larger when nonlinear or linear coefficients of two lasersbecome closer. The satisfied results can be obtained when linear coefficients ratio is limited whitin a range from 0.05 to 0.67. In addition, the essential transition spacing in multiplexed transmissions, larger than the full width of transitions, is considered to be able to improve the fitting accuracy. This approach is validated in a static absorption cell over a pressure range from 1 to 10 atm at room temperature to demonstrate the ability to measure the blended CO2 spectrum from 63307 cm-1 to 6337 cm-1 by a single DFB laser. The sensor method resolves laser intensity with a nonlinear coefficient of 1.4×10-4 and recovers absorbance with a root mean square (RMS) precision of 3.2%, which demonstrates the applicability of this sensor to high-pressure gas sensing systems. Another approach to validating the gas temperature and measuring H2O by WDM is presented in a gas-liquid two phase pulsed detonation engine running with a filling fraction of 100%. Two fiber coupled lasers, respectively, near 7185.6 cm-1 and 7444.35 cm-1 are scanned at 20 kHz to achieve a temporal resolution of 50 μs for monitoring detonation exhaust. A fixed spectrum interval (about 0.7 cm-1) of transitions in multiplexed transmission is created through temperature adjustment in DFB laser to provide more independent absorption information. Recovered linear coefficients of 0.18 and 0.46 in two DFB lasers are in good agreement with the results from the simulations. An instantaneous temperature measurement of 1183 K in the exhaust 7.45 ms after detonation wave provides the confirmation of the ability of this method to infer the temperature and H2O time histories in the whole detonation process. In conclusion, the novel approach based on TDLAS has tremendous potential applications in high pressure combustion diagnosis and WDM spectrum analysis.

Parametric cycle analysis of an ideal pulse detonation engine – Supersonic branch

The purpose of this note is to present a mathematical description of an ideal pulse detonation engine (PDE) based on parametric cycle analysis for supersonic heat addition. The parametric cycle analysis is presented in terms of parameters similar to those for the well-known parametric cycle analyses for the ideal ramjet engine. The performance characteristics of specific thrust, thrust-specific fuel consumption, fuel-to-air ratio, thermal efficiency, propulsive efficiency, overall efficiency, and thrust flux are illustrated as functions of the two parameters: inlet/diffuser exit Mach number, M2 > 1, and freestream Mach number, Mo. This work provides algebraic equations which can be used quickly to investigate the ideal supersonic combustion PDE performance as a function of a variety of input parameters. It is hoped that this work will aid in exploring the performance of the ideal supersonic combustion PDE from a big picture perspective.

Advanced energy technologies in aviation

In this study, analytical and computational analysis is performed to determine the effect of thermodynamic detonation parameters on the performance of the pulse detonation engine. For analytical study along with pure fuels blend of hydrogen (50 %) + kerosene (50 %), hydrogen (50 %) + methane (50 %) and methane (50 %) + kerosene (50 %) are considered. The ANSYS FLUENT program is utilized two-dimensional computational fluid dynamics (CFD) simulation using a stoichiometric mixture of three pure fuels: hydrogen-air, methane-air, and kerosene-air. Time-dependent numerical simulations are used to explore the flow condition inside the detonation tube. Excellent performance is observed for hydrogen-air fuel. Hydrogen shows the highest velocity of 2524.36 m/s and a specific impulse of 6842.16 s. The lowest velocity and specific impulse are produced by kerosene of 1520 m/s and 1473.6 s, respectively. It is shown that measured parameters could vary significantly depending on the choice of fuels used. The results infer that hydrogen blends of methane and kerosene fuels are also suitable for pulse detonation engine (PDE) application. Finally, these analytical and simulated results are validated with the previously published literature and NASA CEA (national aeronautics and space administration -chemical equilibrium with applications).

Ignition of lean and stoichiometric air–propane mixture with a subcritical microwave streamer discharge

Pulse detonation engines are considered to be one of effective propulsion systems for future space missions. Significant efforts are being spent on acceleration of fuel combustion and rising is efficiency. Existing studies have mainly focused on optimizing fuel injection and mixing, repetitive initiation of detonation and integration of detonation tubes with fuel inlets. Understanding of streamer propagation mechanism is of essential importance for the studies of electrical breakdown phenomena and their related applications. In this study, a subcritical microwave streamer discharge is used to initiate ignition of air–fuel mixtures. Ignition of lean fuel mixtures by a streamer has been demonstrated at atmospheric pressure. The speed of streamer-initiated combustion has been shown to be higher compared to that initiated by a spark. The combustion efficiency has also been shown to be higher when using the microwave streamer ignition.

Application of Anova to Pulse Detonation Engine Dynamic Performance Measurements

Application of Anova to Pulse detonation engine dynamic performance measurement resulted in quantifying engine functionality during various operations. After evaluating the performance, techniques of improving it, were applied in multiple areas of relevant interest. This produced encouraging results and helped in upscaling efforts in a significant manner. The current paper deals in the details of anova implementation and systematic identification of key areas of improvements. The improvements were carried out after careful selection of plans in the engine, ground rig and instrumentation setup etc. It also yielded better reproducibility of performance and optimization of main subsystems of PDE. Further, this will also contribute to reduce the development cycle and trial complexity also, if researchers continue to extract concern areas to be addressed.

Utilization of Nonthermal Plasma in Pulse Detonation Engine Ignition

Nonthermal plasma ignition using alternating-current-driven dielectric barrier discharge is applied to a pulse detonation engine. Five different geometrical in-house design plasma generators are tested to obtain more effective discharge performance. The selected plasma igniter, with 4.0 mm discharge gap between two electrodes with a dielectric barrier, can be powered by an alternating-current supply with output voltage and sinusoidal wave frequency. The required discharging waveforms, and hence ignition energy, can be obtained by the automatic frequency-control system, via which the operating frequency can be adjusted up to 500.0 Hz holding with almost unchanged breakdown voltages and currents in practical application. The respective mixture of hydrogen, acetylene, and ethylene was allocated with an excess air coefficient ranged from 0.6 to 1.4. The initial pressure of the mixture changed from 0.04 to 0.1 MPa and was tested in the single-trial experiments. The shortened deflagration-to-detonation transition and detonation waves show the effectiveness of nonthermal plasma-assisted ignition for wider excess air coefficients. The multicycle mode is also conducted to show the performance of 15.0 Hz collaborative operation using the plasma igniter in an airbreathing pulse detonation engine. The feasibility of the present alternating-current-driven dielectric barrier discharge technology to generate nonthermal plasma is thus verified for single-trial detonation tube and multicycle pulse detonation engine ignition in laboratory.

Study on the effects of ionization seeds on pulse detonation characteristics

Ionization phenomenon is happened on the wave front due to the presence of high temperature and pressure in the detonation process. Plasma produced in the detonation process can be used as magnetohydrodynamic (MHD) generator or flow controlled by the external magnetic field. However, it is necessary to increase the ionization efficiency by adding metal ions with lower ionization potential owing to the limited amount of plasma produced by detonation. In this paper, a model of pulse detonation engine with ionization seeds was established. The Conservation Element and Solution Element (CE/SE) method was deduced to simulate the interaction between plasma and detonation process. The influence of ionization seed contents on the electrical conductivity and detonation characteristic parameters was analyzed, and the MHD control of detonation process was realized by adding the external electromagnetic field device. The results showed that it had a little influence on the detonation process but a great influence on the generation of detonation plasma by the addition of a certain amount of ionized seed. The ion mass fraction and electrical conductivity in the detonation tube were first increased and then decreased with the increase of ionization seed content, which reached the maximum at the ionization seed mass fraction of 0.05. The acceleration and deceleration process could be achieved by the MHD control.

A novel blast-mitigation concept for light tactical vehicles

PurposeA new concept solution for improving blast survivability of the light tactical military vehicles is proposed and critically assessed using computational engineering methods and tools.Design/methodology/approachThe solution is inspired by the principle of operation of the rocket-engine nozzles, in general and the so called “pulse detonation” rocket engines, in particular, and is an extension of the recently introduced so-called “blast chimney” concept (essentially a vertical channel connecting the bottom and the roof and passing through the cabin of a light tactical vehicle). Relative to the blast-chimney concept, the new solution offers benefits since it does not compromise the cabin space or the ability of the vehicle occupants to scout the environment and, is not expected to, degrade the vehicle’s structural durability/reliability. The proposed concept utilizes side vent channels attached to the V-shaped vehicle underbody whose geometry is optimized with respect to the attainment of the maximum downward thrust on the vehicle. In the course of the channel design optimization, analytical and computational analyses of supersonic flow (analogous to the one often used in the case of the pulse detonation engine) are employed.FindingsThe preliminary results obtained reveal the beneficial effects of the side channels in reducing the blast momentum, although the extent of these effects is quite small (2-4 per cent).Originality/valueTo the authors’ knowledge, the present work is the first exploration of the side-vent-channels concept for mitigating the effect of buried-mine explosion on a light tactical vehicle.

Performance Metric for Turbine Stage Under Unsteady Pulsating Flow Environment

In a turbine stage for a vehicular turbocharger or a pulse detonation engine (PDE) system, the power extraction process is inherently unsteady due to a highly pulsating flow delivered from the upstream combustor. Characterizing the operating performance of such a turbine stage would call for defining unsteady efficiency on a physically rigorous basis. Since the instantaneous efficiency can be calculated as the fraction of the actual power to the unsteady ideal power, an expression for the unsteady ideal power from the turbine stage is first derived by applying mass conservation and the first/second law of thermodynamics for the turbine stage. The newly derived expression elucidates the distinction from the quasi-steady situation in that the storage effect of mass/energy/entropy over the turbine stage is no longer negligible compared to the flux of mass/energy/entropy at the inlet and outlet. The storage effect resolves the previously reported physical inconsistency that the instantaneous efficiency can be a value of above unity or below zero; an erroneous result associated with defining the efficiency based on a quasi-steady basis. As the reduced frequency of the inlet pulsation of the turbine stage becomes larger than unity, the mass/energy/entropy accumulation rate over the turbine stage becomes significant compared to the mass/energy/entropy influx rate. Then, the definition of the efficiency based on a quasi-steady assumption loses its applicability. In this paper, the role of mass/energy/entropy storage rate in the unsteady ideal power is assessed in order to underpin the inconsistency in the previous quasi-steady approach. The utility of the unsteady efficiency definition is elucidated for the case of a turbocharger turbine stage subjected to high inlet flow pulsation.

Calculation of shock wave propagation in water containing reactive gas bubbles

The entry of a shock wave from air into water containing reactive gas (stoichiometric acetylene–oxygen mixture) bubbles uniformly distributed over the volume of the liquid has been numerically investigated using equations describing two-phase compressible viscous reactive flow. It has been demonstrated that a steady-state supersonic self-sustaining reaction front with rapid and complete fuel burnout in the leading shock wave can propagate in this bubbly medium. This reaction front can be treated as a detonation-like front or “bubble detonation.” The calculated and measured velocities of the bubble detonation wave have been compared at initial gas volume fraction of 2 to 6%. The observed and calculated data are in satisfactory qualitative and quantitative agreement. The structure of the bubble detonation wave has been numerically studied. In this wave, the gas volume fraction behind the leading front is approximately 3–4 times higher than in the pressure wave that propagates in water with air bubbles when the other initial conditions are the same. The bubble detonation wave can form after the penetration of the shock wave to a small depth (~300 mm) into the column of the bubbly medium. The model suggested here can be used to find optimum conditions for maximizing the efficiency of momentum transfer from the pressure wave to the bubbly medium in promising hydrojet pulse detonation engines.

ロータリーバルブを使用したパルスデトネーションエンジンの作動実験

ロータリーバルブを使用したパルスデトネーションエンジンの作動実験

Ignition Study on a Rotary-valved Air-breathing Pulse Detonation Engine

AbstractIn the present study, the ignition effect on detonation initiation was investigated in the air-breathing pulse detonation engine. Two kinds of fuel injection and ignition methods were applied. For one method, fuel and air was pre-mixed outside the PDE and then injected into the detonation tube. The droplet sizes of mixtures were measured. An annular cavity was used as the ignition section. For the other method, fuel-air mixtures were mixed inside the PDE, and a pre-combustor was utilized as the ignition source. At firing frequency of 20 Hz, transition to detonation was obtained. Experimental results indicated that the ignition position and initial flame acceleration had important effects on the deflagration-to-detonation transition.

Closed-loop active flow control of a non-steady flow field in a highly-loaded compressor cascade

The provision of secure compressor operation under circumstances of a pulsed detonation engine is crucial for the success of pressure gaining combustion processes for turbo machinery applications. This paper discusses active flow control as a possible solution to approach this challenge. The presented experiments were conducted on a highly loaded low speed linear compressor stator cascade operated at \(Re=600{,}000\) and \(Ma =0.07\). A choking-device which was located in the wake of the cascade simulated the non-steady outflow condition that is expected under the conditions of pressure gaining combustion. In the discussed experiments, the choking-device generated a periodic disturbance to every passage at a typical Strouhal number of \(Sr =0.03\). The flow structures of the non-steady flow field were strongly correlated to the working-phase of the choking-device. In this paper, an iterative learning controller was used to find an optimized actuation trajectory that was used for closed-loop sidewall-actuation to control the corner separation in the non-steady flow field. The iterative learning controller took advantage of the periodicity of the disturbance to calculate a non-steady actuation trajectory that optimally suppressed the impact of the choking-device on the flow. The active flow control effect was evaluated by means of static pressure rise using five hole probe measurements in the wake of one passage.

Effects of a jet turbulator upon flame acceleration in a detonation tube

Allowing a fuel/air mixture to flow through bluff-body structures enhances the deflagration-to-detonation transition (DDT) process in pulse-detonation engines by increasing the turbulence intensity within the detonation chamber. However, these structures give rise to resistance and thrust loss. The use of jets as turbulators to reduce the obstacle-blockage ratio may reduce this loss. A jet turbulator composed of multiple evenly spaced jets on the tube wall was designed, and its effects upon flame acceleration were analysed. The results show that fuel/air-mixture jets combined with a low obstacle-blockage ratio can accelerate flame propagation whereas pure-air jets cannot. The jet turbulator offers an improvement over bluff-body structures in terms of acceleration of the DDT process.

Flow Rate Measurement Method for Gaseous Fuel Injection for Pulse Detonation Engines

A mass-flow model was developed to calculate the flow rates of a gaseous fuel and oxidizer injected intermittently into a pulse detonation engine. The procedure used the mass-flow parameter of the gas to estimate the ideal mass-flow rate. The ideal mass-flow rate calculation incorporated determination of the time-varying injection surface area, supply pressure, and temperature and specific heat ratio of the gas considering choked flow at the injecting surface. This value of ideal mass flow was multiplied by an experimentally determined discharge coefficient to account for losses. The calculated mass-flow rates and valve opening time duration were used to calculate the total mass of reactants injected per pulse for a typical pulse detonation engine. In addition, a scheme for the change in injection surface area for different types of valve openings was presented. Results indicated the practicality of the developed mass-flow model to calculate the intermittent gas mass injection into a pulse detonation engine. The results also showed that the experimentally determined discharge coefficient via steady-state calibration held true for valve operation at 1, 10, and 20 Hz.

Overview of Performance, Application, and Analysis of Rotating Detonation Engine Technologies

Recent accomplishments related to the performance, application, and analysis of rotating detonation engine technologies are discussed. The pioneering development of optically accessible rotating detonation engines coupled with the application of established diagnostic techniques is enabling a new research direction. In particular, chemiluminescence images of detonations propagating through the annular channel of a rotating detonation engine are reported and appear remarkably similar to computational fluid dynamic results of rotating detonation engines published in the literature. Specific impulse measurements of rotating detonation engines and pulsed detonation engines are shown to be quantitatively similar for engines operating on hydrogen/air and ethylene/air mixtures. The encouraging results indicate that rotating detonation engines are capable of producing thrust with fuel efficiencies that are similar to those associated with pulsed detonation engines while operating on gaseous hydrocarbon fuels. A rotating detonation engine is coupled with a turboshaft engine for the first time. The performance of the rotating detonation engine gas turbine engine is similar to or better than that of the conventional gas turbine engine across a broad range of operating conditions. Realizing the advantages of pressure gain combustion in rotating detonation engines is enabling new combustion system design opportunities and supporting the development of efficient and sustainable power and propulsion technologies.