Pulse Detonation Research Articles

Effect of oxygen rich environment on detonation characteristics of pulse detonation engine

The detonation tests of propane/air pulse detonation engine at normal temperature were carried out in this paper. The effects of chemical ratios on the detonation performance of propane/air pulse detonation engine in oxygen-rich environment were studied. The propagation modes and characteristics of detonation waves and the detonation characteristics of the engine under different conditions were analyzed. Detonation tests were conducted on propane/air mixtures with oxygen mass fraction of 20%, 25%, 30% and 35% respectively. The results showed that: In the detonation experiment of the propane/air mixture with oxygen content of 20%, 25% and 30%, the flame wave propagation velocity in the detonation tube is low, which fails to form a stable detonation wave. The detonation effect of the fuel mixture with oxygen content of 20% is the worst, and the propagation velocity of flame wave is 384.00 m/s. In the experiment of propane/air mixture with oxygen content of 35%, the detonation velocity and pressure obtained by pressure signal analysis are both greater than the theoretical CJ detonation velocity, and the detonation state is successfully reached.

Performance analysis of a pulse detonation turbine engine based on unsteady finite-time model

Quasi-steady state and transient state performance analyses of a pulse detonation turbine engine (PDTE) are conducted based on an unsteady finite-time model. In quasi-steady state performance analysis, the transient compressor operation status over a detonation cycle time is studied. The thrust, specific fuel consumption, and the cycle thermal efficiency are compared under four different operation frequencies. The power extraction method is introduced to design a control strategy for the transient state performance analysis. Last, effect of flight conditions on the PDTE acceleration performance is investigated. The results show that the compressor will enter the surge condition during the pulse detonation combustor (PDC) exhaust period and strive back to the non-surge condition during the filling process due to the pressure changes in PDC. The increasing of the operation frequency will bring performance promotion, as the thrust and thermal efficiency will increase while the specific fuel consumption will go down. An optimal fuel supply law is obtained by utilizing the power extraction method, and it takes the PDTE 6.08s to accelerate from the corrected rotor speed of 0.6–1.0. The rising of flight altitude will dramatically prolong the acceleration process, while increasing of Ma will speed up the acceleration process.

Анализ действия детонационного генератора низкоамплитудных импульсов давления регулируемой длительности

The paper presents results of the analysis conducted on the action of the low-amplitude pressure pulse detonation generator with adjustable duration, where the detonation wave affects the controlled compressible medium and propagates in the direction from the medium subjected to the shock wave compression. Analytical expressions are provided for a simple model of the process under study to calculate the pressure pulse amplitude-time characteristics on the compressible medium with the charge detonation product plane-symmetric flow and the compressible inert medium. The paper considers a scheme of experimental (laboratory) assembly. In its cylindrical channel, the detonation product quasi-one-dimensional effect on the controlled environment is realized. Results of registering dynamics of pressure alterations in the controlled environment were obtained. When comparing calculation and experiment results, the reasons causing their discrepancy were identified. If the assembly body is made of steel not subjected to heat treatment, then it becomes possible to use it five times (at least) with charges of the bulk explosives based on the hexogen with generating controlled pressure pulses of several kilobars in the condensed organic materials with duration of at least tens of microseconds. In this case, the pressure rise time at the pulse leading edge reaches approximately ten microseconds.

A Short Review on Efficiency of Rotating Detonation Engine

The rotating detonation engine (RDE) is a revolutionary propulsion technology with the potential to significantly enhance the efficiency of propulsion systems. This paper provides an in-depth review of the RDE's efficiency, its advantages over pulse detonation engines (PDEs) and deflagration concepts, as well as its applications in rocketry. The historical development of detonation engines, specifically RDE, is discussed, along with various research methodologies applied in both atmospheric and vacuum conditions. The challenges and potential solutions for utilizing RDE in space missions are also explained in this paper.

Modeling a Combustion Chamber of a Pulse Detonation Engine

This paper presents the results of numerical simulation of a model combustion chamber of a pulse detonation engine using the authors’ developed software package. The main goal of the present study is to numerically investigate the effects of cyclic operation of pulse detonating chambers, as the former studies have been limited to simulating one cycle. To achieve this goal, a new mathematical model for heavy gas was applied simulating condensed fuel phase, which made it possible to accelerate computations and simulate multi-cycle operation of the device. Distributions of such characteristics as temperature, pressure, velocity, concentrations of reagents, intensity of reactions, and thrust force are obtained. A two-stage kinetic model of propellant combustion is proposed. Attention is paid to the main stages of PDE operation: filling of the chamber with reagents, ignition and transition to detonation, products exhaust, purification, and cooling the chamber with a neutral gas. The simulation of the working cycle with the shortest period for the specified system parameters was carried out, the execution time of each stage was obtained, and an assessment was carried out to minimize the main stages of the work cycle. Numerical results demonstrated that the characteristics of the engine cycle are stabilized already in the second cycle: the thrust in the first cycle differs from the thrust in the second by 5%, in the third from the second by 1%. Moreover, details of thrust dynamics in the second and third cycles were studied.

Reheat effect on the improvement in efficiency of the turbine driven by pulse detonation

Due to the strong unsteadiness of pulse detonation, large flow losses are generated when the detonation wave interacts with the turbine blades, resulting in low turbine efficiency. Considering that the flow losses are dissipated into the gas as heat energy, some of them can be recycled during the expansion process in subsequent stages by the reheat effect, which should be helpful to improve the detonation-driven turbine efficiency. Taking this into account, this paper developed a numerical model of the detonation chamber coupled with a two-stage axial turbine, and a stoichiometric hydrogen-air mixture was used. The improvement in turbine efficiency attributable to the reheat effect was calculated by comparing the average efficiency of the stages with the efficiency of the two-stage turbine. The research indicated that the first stage was critical in suppressing the flow unsteadiness caused by pulse detonation, which stabilized the intake condition of the second stage and consequently allowed much of the flow losses from the first stage to be recycled, so that the efficiency of the two-stage turbine was improved. At a 95% confidence level, the efficiency improvement was stable at 4.5%–5.3%, demonstrating that the reheat effect is significant in improving the efficiency of the detonation-driven turbine.

Experimental Study on the Ignition Characteristics of Scramjet Combustor with Tandem Cavities Using Micro-Pulse Detonation Engine

This experimental investigation focused on the ignition and combustion characteristics of a tandem cavity-based scramjet combustor with side-by-side identical cavities. This study utilized the Pusan National University-direct connect scramjet combustor (PNU-DCSC), which was capable of simulating flight conditions at Mach number 4.0–5.0 and altitudes of 20–25 km using the vitiated air heater (VAH). The combustion tests were conducted under off-design point conditions corresponding to low inlet enthalpy. It is a condition in which self-ignition does not occur, and a micro pulse detonation engine (μPDE) ignitor is used. The results revealed that as the injection pressure of the gaseous hydrogen fuel (GH2) and the corresponding equivalence ratio increased, the combustion mode transitioned from the cavity-shear layer flame to the jet-wake flame. Furthermore, the measured wall static pressure profiles along the isolator and scramjet combustor indicated that the region of elevated pressure distribution caused by the shock train expanded upstream with higher equivalence ratios. When ignited from the secondary cavity, the combustion area did not extend to the primary cavity at lower equivalence ratios, while it expanded upstream faster with higher equivalence ratios. Therefore, the combustion characteristics of the tandem cavity were found to vary based on the overall equivalence ratio of the main fuel (GH2) and ignition position.

Experimental and Numerical Study of Pulse Detonation Engine with Ethylene as a Fuel

This paper presents an insight on the study of transient, compressible, intermittent pulsed detonation engine with one-step overall reaction model to reduce the computational complexity in detonation simulations. Investigations are done on flow field conditions developing inside the tube with the usage of irreversible one-step chemical reactions for detonations. In the present simulations one and two-dimensional axisymmetric tubes are considered for the investigation. Studies are also performed with different grid sizes which influence the prediction of Von-Neumann spike, CJ Pressure and detonation velocity. Numerical studies are conducted using 66mm diameter tube and compared with the literature values. The simulation result from the single-step reaction model agrees well with the previous published literature of multi-step reaction models. The present studies shows that one-step overall reaction model is sufficient to predict the flow properties with reasonable accuracy. Experiments are conducted in a 25mm dia. tube with Ethylene/Air mixtures. The reactants are premixed and injected into the detonation tube using solenoid valves. The equivalence ratio of the fuel/oxidizer mixture and the length of the detonation tube are varied to understand their effects on detonation parameters. Finally the results from the present numerical study are compared and validated using NASA CEA and experiments.

Experimental study of DDT run-up distance and detonation wave velocity deficit for stoichiometric hydrogen-oxygen mixture in micro spiral channels

The determination of the deflagration-to-detonation transition (DDT) run-up distance LDDT is crucial in both the design of pulse detonation engines (PDEs) and safety protection. In this paper, the LDDT of stoichiometric hydrogen–oxygen premixed mixtures in millimeter-scale spiral channels were studied experimentally and high-speed photography was employed to capture the flame propagation process. The mixtures in three different rectangular cross-sectional channel widths and various initial pressures were tested. The present results show that the LDDT decreases with increasing the initial pressure, and with increasing the channel width, the larger LDDT is observed. When fitted with the LDDT ∝ P0−m relationship, the values of m obtained in this study ranged from 0.997 to 4.222. The critical value of 0.1 for the equivalent area divergence induced by the boundary layer ξ is proposed to distinguish the behaviors between micro and macro channels, regardless of the type of mixture and channel configuration. Additionally, an empirical formula considering the influence of the boundary layer is obtained, which allows for the quantitative prediction of LDDT. Because of the influence of curvature effect, the smaller the channel width, the greater the prediction deviation. Due to the boundary layer effect, the momentum and heat dissipation are more pronounced in smaller tubes, resulting in a loss of velocity for the detonation wave. It is suggested that the detonation wave velocity increases as the channel width and initial pressure increase. Fay's model was employed to estimate the theoretical velocity deficit, and the experimental results were in good agreement with the theoretical predictions. The current findings are valuable for the field of micro PDE and may help the assessment of the potential risk of hydrogen detonation in micro systems.

ON THE DETERMINATION OF THE SPECIFIC HEAT FLUX VALUE IN A PULSE DETONATION ENGINE’S CHAMBER

Abstract. The development of detonation engines (DE) is one of the most promising areas of rocket and space engine manufacturing. They are more efficient as compared to the liquid rocket engines and are structurally simpler. At the same time, the detonation engine chamber’s structure is subjected to much higher thermal loads. Therefore, at the development stage of the DEs, to create an efficient cooling system for the engine’s chamber, it is necessary to be able to determine the value of thermal energy, which is absorbed by the walls of the DE’s chamber. The goal of this research is to determine the specific heat flux from the detonation products towards the walls of the pulse detonation engine’s (PDE) chamber. The task of the work is to establish the methodology for calculating the values of the specific heat flux transmitted to the walls of the PDE’s chamber. The main tools for solving this problem are the method of mathematical simulation using computational fluid dynamics (CFD), and the method of regression analysis. The main results of this study: the possibility to utilize the well-known Ievlev methodology to determine the convective specific heat flux for the PDE’s chamber was analyzed; it was shown that for the conditions of the PDE’s chamber, the Ievlev methodology calculation results differ significantly from the experimental data, which can be explained by the presence of a clearly pronounced non-stationary nature of the detonation process; it was proven the utilization of the Viegas formula to obtain the values of the convective specific heat flux for the PDE’s chamber gives better results as compared to the known experimental data and the results of the mathematical simulations; it was also demonstrated that the average integral value of the specific heat flux, determined by the described methodology, can be used to calculate the thermal state of the PDE's chamber. Conclusion: a methodology for calculation of the specific heat flux value for the pulse detonation engine's chamber was proposed. The obtained calculation results are in good agreement with the results of mathematical simulations and known experimental data. The described methodology can be used in the design of cooling systems for the pulse detonation engine’s chambers.

Effect of back-propagation pressure on axial flow compressor in a pulse detonation turbine engine

In order to reveal the affect mechanism of the back-propagation pressure on the axial flow compressor, the pressure back-propagation process and the effect of back-propagation pressure on compressor were carried out by numerical simulation. The pressure back-propagation characteristics in the pulse detonation chamber and intake section were studied by the 2-D numerical simulation with stoichiometric propane/air mixture. And the pressure histories at the inlet of the intake section were applied as the boundary conditions of the compressor outlet in the 3-D numerical simulation of the axial flow compressor. The simulation results indicated that there existed a critical value of back-propagation pressure oscillation ratio, above which the compressor would enter the unstable operating state eventually. The flow deceleration behind the back-propagation pressure waves was the fundamental reason for the compressor to enter the unstable operating state.

Experimental study on tesla valve and bypass manifold to suppress feedback of rotating detonation engine fuel by kerosene

In this paper, the effects of the Tesla valve intake structure with or without bypass manifold on suppressing pressure feedback and combustion product backflow in rotating detonation engine fueled by kerosene and enriched air with 29% oxygen content are investigated, with the configuration of convergent–divergent intake without bypass manifold being used for comparison. The working range, detonation wave propagation characteristics, and propulsion performance for the three configurations are evaluated. It is found that the Tesla valve intake structure can effectively improve the suppression of pressure feedback and combustion product backflow through the diversion function of the Tesla valve bypass channel and that the addition of the bypass manifold further improves the suppression of pressure feedback. The Tesla valve intake with bypass manifold configuration has the best ability to suppress pressure feedback, with a minimum value of pressure feedback percentage of about 6.5% and a minimum value of air plenum pressure fluctuation percentage of about 6.7%. By comparison, the minimum value of pressure feedback percentage of the convergent–divergent intake without bypass manifold configuration is about 29.8%, and its minimum value of pressure feedback percentage is about 7.8%. The Tesla valve intake without bypass manifold configuration is most effective in suppressing combustion product backflow, with the effective inlet area ratio of about 95.7%. Under the same conditions, the minimum effective inlet area ratio of the convergent–divergent intake without bypass manifold configuration is about 90.2%. Ultimately, optimizing the engine structure leads to a broader working range and higher propulsion performance. The Tesla valve intake structure broadens the working range by suppressing the generation of the longitudinal pulsed detonation mode. When the bypass manifold is incorporated, some combustible reactants directly enter the rear of the combustion chamber from the head of the chamber, and the working range is reduced. Compared with the convergent–divergent intake without bypass manifold configuration, the working range of the Tesla valve intake with bypass manifold configuration is widened by 383.3%, and that of the without bypass manifold configuration by 700%. Both the Tesla valve intake and bypass manifold increase the strength of detonation waves and improve propulsion performance. The Tesla valve intake with bypass manifold configuration has the highest specific thrust, at about 90.1 N s3/(kg·m). This is increased by an average of 10% compared with the Tesla valve intake without bypass manifold configuration, and by an average of 30.1% compared with the convergent–divergent intake configuration.

Experimental study on suppressing pressure feedback and combustion product backflow of the rotating detonation engine

To further improve the feedback suppression effect of rotating detonation engines (RDEs), an optimized Tesla valve inlet structure (TVI-II) was designed on the basis of the previous research of our research group. Taking kerosene and 29% oxygen-enriched air as the reactants, the operation characteristics, the feedback suppression effect, and the feedback suppression mechanism were obtained through a series of experiments. It is found that due to the existence of bypass channel, TVI-RDE can effectively suppress the occurrence of longitudinal pulsed detonation and broaden the working boundary of the engine. The working range of the TVI-I-RDE was broadened by 183.3%, and that of the TVI-II-RDE was broadened by 700%. The TVI-II-RDE is more effective in suppressing pressure feedback and combustion product backflow. When the pressure feedback phenomenon occurs, the rotating detonation wave mainly decoupled and attenuated in the converging section of bypass channel. The minimum pressure feedback percentage (PFdw) of TVI-II-RDE was 11.4%, as compared to about 40% for the TVI-I-RDE. The change law of the air plenum pressure fluctuation percentage (PFap) was similar to that of PFdw, and the minimum PFap of the TVI-II-RDE was about 7.7%. Narrower bypass channel width would lead to longer residence time of combustion products. The effective inlet area ratio (EA) of the TVI-II-RDE was at least 95.7%, which is at least 6.1% higher than that of the CDI structure. The results show that the TVI-II-RDE has great potential in suppressing feedback, which promotes the engineering application of RDE.

Numerical Analysis on Detonation Wave and Combustion Efficiency of Pulse Detonation Combustor With U-Shape Combustor

Abstract The research work is carried out for deflagration and detonation combustion processes at different equivalence ratios of hydrogen–air mixtures in a pulse detonation combustor (PDC). Furthermore, the U-shape channel curvature radius and thickness effect on detonation wave propagation are also investigated. This numerical simulation has been done using a SIMPLE algorithm with the finite volume discretization method and laminar finite rate chemistry for volumetric reaction in the Ansys Fluent platform. The numerical result shows that the U-bend radius of R = 3.5 cm can enhance the faster deflagration-to-detonation transition. So far, the fully developed detonation wave was found near the curvature area of the detonation tube having a width of W = 8 cm. This enhanced detonation wave velocity reaches 2775 m/s, which is higher than the C-J detonation velocity. Furthermore, the entropy generation has been analyzed in two modes of the combustion process. The entropy generation number of 0.76 and 0.7 is obtained from the deflagration and detonation combustion processes. However, the entropy production rate is less in the detonation combustion process, but thermal entropy generation is more in the deflagration combustion process with a magnitude of 3.5 kJ/kg K for an equivalence ratio of φ = 1.5. A combustion efficiency of 78% is found in the detonation combustion process, which is comparatively higher than the deflagration process.

Fast Deflagration-to-Detonation Transition in Helical Tubes

When designing a new type of power plants operating on pulsed detonations of gaseous or liquid fuels, the concept of fast deflagration-to-detonation transition (FDDT) is used. According to the concept, a flame arising from a weak ignition source must accelerate so fast as to form an intense shock wave at a minimum distance from the ignition source so that the intensity of the shock wave is sufficient for fast shock-to-detonation transition by some additional arrangements. Hence, the FDDT concept implies the use of special means for flame acceleration and shock wave amplification. In this work, we study the FDDT using a pulsed detonation tube comprising a Shchelkin spiral and a helical tube section with ten coils as the means for flame acceleration and shock amplification (focusing), respectively. To attain the FDDT at the shortest distances for fuels of significantly different detonability, the diameter of the pulsed detonation tube is taken close to the limiting diameter of detonation propagation for air mixtures of regular hydrocarbon fuels (50 mm). Experiments are conducted with air mixtures of individual gaseous fuels (hydrogen, methane, propane, and ethylene) and binary fuel compositions (methane–hydrogen, propane–hydrogen, and ethylene–hydrogen) at normal pressure and temperature conditions. The use of a helical tube with ten coils is shown to considerably extend the fuel-lean concentration limits of detonation as compared to the straight tube and the tube with a helical section with two coils.

Gasification of Waste Machine Oil by the Ultra-Superheated Mixture of Steam and Carbon Dioxide

Reported in the article is further progress in the development of the novel pulsed detonation gun (PDG) technology for the conversion of organic wastes into syngas in a two-component gasifying agent (GA) containing ultra-superheated steam and carbon dioxide obtained by pulsed detonations of a natural gas–oxygen mixture at a frequency of 1 Hz. Experimental studies were carried out on a waste converter with a 40 dm3 flow reactor and two PDGs with a total volume of 2.4 or 3.2 dm3, which is approximately a factor of 6 and 4.5 less than in previous studies, respectively. The objective of the research was to find the design and operation parameters of the waste converter that provide a minimum amount of CO2 in the gasification products. Waste machine oil was used as a feedstock. It is shown that, compared with the earlier experiments with a higher average temperature of the reactor wall and with a PDG of a much larger volume, the contents of H2, CO, CH4, and CO2 in the syngas remained virtually unchanged, whereas the efficiency of the gasification process increased significantly: the use of 1 g of natural gas made it possible to gasify up to 4 g of the feedstock. It is also shown that the determining role in the gasification process of liquid feedstock is played by the feedstock residence time in the PDG rather than in the reactor. The minimum ratio between the flow rates of the GA and liquid feedstock, the minimum ratio between the flow rates of combustible gas and liquid feedstock, as well as the actual GA consumption in the gasification process are determined experimentally.

Deflagration to Detonation Transition in Heterogeneous Mixtures Containing Ethanol/Acetone and Oxygen

Liquid fuel is the choice for volume-limited propulsion systems, including detonation-based propulsion. A liquid fuel with high vapor pressure has the advantage of more fuel vapor in the mixture, which supports the transition from deflagration to detonation. This paper reports on an experimental study of deflagration-to-detonation transition (DDT) in a pulse detonation engine with heterogenous mixtures of oxygen and ethanol or acetone. Single-cycle tests were taken for different fuels, equivalence ratios, and DDT enhancement methods. The size distribution of fuel droplets was characterized at the atomizer and engine exit. The effect of the fuel evaporation was dominant for the acetone spray only. Comparing the measured detonation velocities of the two mixtures, a lower velocity deficit relative to the theoretical Chapman–Jouguet detonation velocity was measured for the acetone–oxygen mixtures, and this behavior is related to the higher amount of fuel vapor that existed in the mixtures. Moreover, a shorter transition to detonation was observed in the acetone–oxygen mixture. The addition of a Shchelkin spiral reduced the DDT distance; however, the Chapman–Jouguet condition could be reached only downstream of the obstacle. The measured detonation cell size of the heterogeneous acetone–oxygen mixture was smaller than that of the ethanol–oxygen mixture, indicating that it is more detonable.

Operational performance parameter range in ICF propulsion theory

This paper explores the operational performance parameter range for inertial confinement fusion propulsion systems under the assumption of best case and worst case mission scenarios. This includes the spacecraft thrust, jet power and specific power. We show the derivation of the key driving equations and then simplify these with approximations for ease of domain space analysis. This includes a consideration of minimum and maximum values for jet efficiency, momentum weighting factor, nozzle divergence angle, fuel burn-up fraction, capsule mass and detonation pulse frequency. It is estimated that the range of parameter values may be of order 0.001 N–100 MN thrust, 1000 W–1,000 TW jet power, 0.01 W/kg–10 GW/kg specific power. Although this range includes values that are likely outside the realistic design space of applicability and to show this data from published designs is also examined. The analysis is considered for reaction isotopes of low mass hydrogen and helium nuclei only and does not take into account the possibility of propellant expellant augmentation, vehicle staging, design optimality or enhanced fuel reactions.

Effects of detonation initial conditions on performance of pulse detonation chamber-axial turbine combined system

The pulse detonation turbine engine (PDTE) has a potential performance advantage over conventional gas turbine engines due to the self-pressurization feature of detonation. However, pulse detonation exhibits strong unsteadiness, and large flow losses can be generated when the detonation wave interacts with the turbine blades, which severely limits engine performance. Therefore, how to maximize this potential performance advantage is crucial to the application of the PDTE. If the detonation initial conditions could be adjusted to modify the characteristics of detonation so that the pulse detonation chamber (PDC) and turbine are well matched, the performance of the PDTE could be greatly improved. Taking this into account, this paper numerically investigated the performance of the PDC-turbine combined system with different hydrogen-air mixture equivalence ratios and initial temperatures. The turbine efficiency and PDC combustion efficiency were analyzed first, which provided guidance for the thermal efficiency analysis. The results indicated that the combined system was more suitable for operation under lean fuel conditions due to the high thermal efficiency and obvious performance advantage over isobaric combustion. In addition, increasing the initial temperature could improve thermal efficiency under lean fuel conditions, but some of the performance advantage would be sacrificed.

Performance analyses of detonation engine cogeneration cycles

AbstractAircraft engines such as gas turbines and detonation engines have very important attention by the researchers in the last decades. However, using detonation engines for producing electrical and heat power was not researched efficiently. In this study, gas turbine and pulse detonation engines cogeneration systems were analyzed and compared by using first and second laws of thermodynamics and exergy analysis method. Three different cycles, namely, basic gas turbine, Zeldovich–von Neumann–Döring (ZND) detonation engine and steam injected regenerative ZND detonation engine cogeneration systems were investigated. The performance analyses and the advantage of these three cycles were obtained and discussed. The performance analyses were done for different compression ratios (r), and the combustion outlet temperatures and pressures, exergy efficiencies, specific fuel consumption, electrical efficiency, exergy fuel consumption, electrical heat rates and other performance parameters of the three cycles were obtained and discussed. It is found that gas turbine cogeneration systems have some advantages and disadvantages in some conditions than ZND cycle. The steam injected regenerative ZND detonation engine cogeneration systems can compete with the Brayton cycle cogeneration systems.