Pulse Detonation Research Articles

Experimental study on thermal load characteristics of a U-bend pulse detonation combustor

The performance of pulse detonation turbine engines (PDTE) surpasses that of conventional turbine engines, primarily due to the pressure gain combustion process inherent in PDTE. A U-bend pulse detonation combustor (PDC) with a compact axial length was designed to meet the requirements of PDTE. However, the PDC introduces complex thermal management challenges. In this study, the wall temperature along the U-bend PDC was experimentally measured under various operating conditions, the thermal load characteristics were investigated. The results indicate that the external wall temperature increases monotonically with prolonged operation, whereas the internal wall temperature exhibits periodic fluctuations corresponding to the periodic filling and combustion process in the PDC. The temperature difference between the internal and external walls increases, then decreases over time, eventually fluctuates within a narrow temperature range. The wall temperature was observed to increase along the flow direction, peaking at 811 °C at 30 Hz at the location where the detonation wave is generated. Similarly, the heat flux of the PDC first increases, then decreases, and eventually reaches a constant value, indicating thermal equilibrium. The heat flux represents a significant energy loss, with the detonation section being the area of highest heat loss, reaching approximately 90.5 kW/m2 at 30 Hz.

Numerical and experimental investigation on the operating characteristics of fan-shaped pulse detonation combustor

The internal flow channel of a turbine engine is typically annular. When circular pulse detonation combustors (PDCs) are installed in this channel, there is a problem with low section utilization rates. To solve this problem, a single-tube fan-shaped PDC test system was developed. The effects of ignition distance on the operating characteristics of the fan-shaped PDC using air and gasoline under different frequencies were studied through both experiment and 3-D numerical simulation. Numerical simulation was also used to investigate the formation and propagation characteristics of detonation waves. The results show that the fan-shaped PDC can operate stably at frequencies ranging from 5 to 25 Hz when the ignition distance is either 2.30 or 2.70 times the equivalent circle diameter from the thrust wall, and it is found to be better to ignite at a distance of 2.30 times the equivalent circle diameter. The blockage ratio of the lower arc surface is larger than that of the other surfaces. This results in more intense collision and reflection. A larger local high pressure area forms near the lower arc surface, which is conducive to the formation of detonation waves. However, the larger blockage ratio makes the flow loss larger, which weakens the intensity of the pressure waves near the lower arc surface. The detonation waves in the fan-shaped PDC travel closer to the upper arc surfaces.

Research on Aircraft Engines and Advanced Power in Land, Sea and Air

This paper provides a comprehensive overview of advanced propulsion technologies in military applications across land, sea, and air domains. It examines the theoretical foundations of propulsion systems, tracing the evolution of aircraft engines from early piston designs to modern jet propulsion. The study explores current state-of-the-art technologies, including advanced turbofan engines, hybrid electric systems, and nuclear propulsion for naval vessels. Special attention is given to emerging fields such as unmanned aerial vehicle propulsion, hypersonic technologies, and stealth engine designs. The research also delves into futuristic concepts like magnetohydrodynamic propulsion and pulse detonation engines. Throughout the analysis, common themes of improved efficiency, enhanced power-to-weight ratios, and increased operational capabilities are highlighted. This paper aims to provide a holistic view of the current landscape and future trajectory of military propulsion technologies, underlining their critical role in shaping modern warfare capabilities.

The effect of spatial non-uniformity on multiple transient modes of detonation onset in a three-dimensional channel

The study of the transient combustion modes is one of the key topics when considering the safety of space flights. Control of detonation onset has a dual application. First, the search for ways to prevent detonation modes in case of accidental fuel releases for fire safety issues of launch systems and the avoidance of accidents with rocket engines at a launch site and in near-Earth space. Second, the study of detonation and the possibility of using it to create propulsion systems based on detonation combustion of fuel. The paper shows the effect of the presence of spatial non-uniformities on the promotion of detonation in the chamber. Various geometries with and without obstacles and cavities are considered. It is demonstrated that the presence of obstacles accelerates the transition to the detonation process on the one hand, but on the other hand the presence of obstacles in combustion chamber could be the cause of incidental uncontrolled ignition, which ruins stable operation of an engine. The results of theoretical studies of the working cycle of the combustion chamber of a pulsed detonation engine are presented. Theoretical estimates for thrust characteristics are obtained.

Effect of Multi-Cycle Combustion on Nox Emission Formation of Hydrogen Fuel in Pulse Detonation Engine

Effect of Multi-Cycle Combustion on Nox Emission Formation of Hydrogen Fuel in Pulse Detonation Engine

Experimental Study and Application Prospects of Coal Dust/Methane/Oxygen Pulse Detonation Performance: Coal Dust Equivalence Ratio and Types.

In order to achieve reliable application of coal in pulse detonation combustion chambers, this study explored the influence mechanism of equivalence ratio and coal type (lignite, anthracite) on the detonation characteristics of coal/methane/oxygen methane-solid two-phase fuel. A high-energy ignition device was used to ignite the preblast methane fuel, and the high-temperature and high-pressure energy generated directly initiated the detonation of coal/methane/oxygen methane-solid two-phase fuel. The experimental results are as follows: (1) The maximum detonation pressure of coal/methane/air fuel is positively correlated with the initial pressure. With the increase of the φglobal, the maximum detonation pressure of the two types of coal gradually increases. To be specific, when the φglobal rises from 0.5 to 1.6, the sensitivity of lignite and anthracite to the maximum detonation pressure with respect to the initial pressure increases from 4.56 to 6.11 and 5.48, respectively; (2) In terms of detonation flame and maximum pressure wave velocity, anthracite shows better dynamic performance than lignite. The maximum velocity of detonation flame and pressure wave is achieved when the φglobal is 1.4. (3) In terms of detonation thrust performance, as the φglobal increases from 0.5 to 1.6, the rate of increase in average thrust of the two types of coal first increases and then decreases. Compared with lignite, anthracite has a wider time domain and higher peak value in the average thrust curve and the generated detonation wave displays a greater impulse. The experimental data and conclusions obtained in this study are of practical significance for realizing the engineering application of pulverized coal detonator power generation.

Numerical study of hydrogen ratio effect on detonation initiation characteristics of aviation kerosene with hydrogen addition

Detonation initiation is one of the most important problems in the research of pulse detonation engine (PDE). It is difficult for aviation kerosene to meet the performance requirement of short-distance detonation initiation in PDE. Hydrogen can improve the detonability of fuels. Aviation kerosene with hydrogen addition provides a new method to shorten the detonation initiation distance in PDE. Therefore, hydrogen ratio effect on detonation initiation characteristics of hydrogen-doped aviation kerosene was studied by two-dimensional numerical simulation with the adoption of standard k-ε model, finite rate reaction model and simplified aviation kerosene/hydrogen/air reaction kinetics mechanism. The results indicated that hydrogen-doped aviation kerosene/air mixtures could not be successfully detonated with the minimum hydrogen ratio of 9.73 %, while the detonation was eventually initiated with higher hydrogen ratios, suggesting that the detonability of hydrogen-doped aviation kerosene was improved by increasing hydrogen ratio. The critical hydrogen ratio of 11 % was determined by further research. As the hydrogen ratio increased, the initiation time and distance of the plane detonation wave first increased slowly and then decreased rapidly, while the detonation velocity raised monotonically. The degree of spherical wave decoupling had an influence on the detonation initiation. Specifically, less spherical wave decoupling induced two Mach stems to propagate at the same time, which was conducive to accelerating the initiation of plane detonation.

Synergistic effect of physicochemical and geometric techniques for initiating detonation in a small-size pulse detonation engine

This article is devoted to the influence of temperature, obstacle and enrichment of the liquid fuel–air mixture with oxygen, as well as the synergistic effect of the combined action of these techniques on the initiation of detonation in a small-sized pulsed detonation engine with a channel of subcritical dimensions (d = 20 mm and L = 500 mm). Explosive limits for detonation of heptane in the frequency mode (f = 1–50 Hz) have been established in terms of the equivalence ratio (ϕ = 0.7–2.6) and in terms of the oxygen-to-air ratio ([O2/air] > 2 for heptane and [O2/air] > 3 for Jet-A1). It was found that the wave velocity in heptane-oxygen-air and Jet-A1-oxygen-air mixtures varies from 500 m/s to 2500 m/s depending on the technique used to accelerate the DDT. Without the use of special techniques, detonation does not occur, and the wave velocity does not exceed 700 m/s. The use of heat, or obstacle or oxygen enrichment leads to the initiation of detonation at distances of 540–660 mm from the ignition initiator, which is 20–26 calibers of engine diameter. A synergistic effect of the combined use of an obstacle, thermal activation and enrichment of the mixture with oxygen was discovered, which made it possible to reduce the pre-detonation distance by almost 60 % and increase the frequency of the detonation mode by also 60 % (up to 80 Hz) compared to each technique separately.

Experimental Pressure Gain Analysis of Pulsed Detonation Engine

A pulsed detonation chamber (PDC) equipped with Hartmann–Sprenger resonators has been designed and tested for both Hydrogen/air and Hydrogen/Oxygen mixtures. A full-factorial experimental campaign employing four factors with four levels each has been carried out for both mixtures. Instantaneous static pressure has been measured at two locations on the exhaust pipe of the PDC, and the signal has been processed to extract the average and maximum cycle pressures and the operating frequency of the spark plug. The PDC has been shown to be able to reach sustained detonation cycles over a length below 200 mm, measured from the spark plug to the first pressure sensor. The optimal regimes for both air and Oxygen operation have been determined, and the influence of the four factors on the responses is discussed.

A comparative study based on control system for a pulse detonation engine

Pulse Detonation Engine has been a point of interest in the propulsion industry for some time and the interest has been rising due to its better output and results. But any system can perform its task efficiently based on the efficiency of its control system. In this paper we have presented a comparative study between multiple control systems- one based on Bluetooth technology, the other based on infrared sensor technology and one based on wired electrical system. For the wireless system, the signal received from either of the media is passed to the various sensors and systems connected through an Arduino board that further controls the solenoid valves and ignition system. Primarily, a control system circuit is developed using Arduino board and different sensors to connect the fuel supply and ignition system. In the next stage, Bluetooth sensors are connected using an android app and then an infrared sensor based system is integrated with the Arduino to control the engine and the performance of the two systems are compared. Whereas for wired system, every sub system is controlled through optical wires including the solenoid valves, the injection system and the sensors.

Correction: Numerical Evaluation of Varying Combustion Chamber Length on the Performance of Pulse Detonation Engine Using DES Model

Correction: Numerical Evaluation of Varying Combustion Chamber Length on the Performance of Pulse Detonation Engine Using DES Model

Investigation of the relationship between combustion efficiency and total pressure gain for RDE

Total pressure gain is an important parameter in RDC engineering applications. Many factors affect the total pressure gain, such as the area ratio of the outlet to the inlet (A8/A3.1) and type of fuel. In this study, convergent–divergent slot and Tesla valve inlet configurations were adopted. Three convergent nozzles were used, and the ratios of the outlet area to the combustor cross-sectional area (A8/A3.2) were 0.65, 0.5, and 0.25, respectively. The experiments were conducted at mass flow rate of 1.5 kg/s, 1.3 kg/s, and 1.0 kg/s. The combustion efficiency and total pressure gain were calculated using the temperature increase and Mach-corrected static pressure (MCSP). When A8/A3.2 is 0.25, most of the propagation modes are longitudinal pulsed detonations (LPD). The combustion efficiency increased with the equivalence ratio within the range of the detonation boundary. A model was developed to describe the relationship between combustion efficiency and total pressure gain. Once the configuration of the RDC is fixed, a proportional relationship exists between the combustion efficiency and total pressure gain. Improving combustion efficiency enhances the total pressure gain.

Study on the influence of outlet diameter on the out-field pressure action characteristics of pulse detonation cleaning device

Pulse detonation cleaning technology is an efficient cleaning technology that is used inert shock waves generated by decoupling the detonation to remove ash and deposits. And it has great advantages in the field of furnace cleaning. In order to investigate the pressure distribution characteristics outside the detonation cleaning device and to explore the effect of the device outlet diameter on the pressure distribution characteristics, numerical simulations and experimental studies of pulse detonation cleaning device with using propane-air as the fuel has been carried out. The numerical simulation and experimental study on pulse detonation cleaning device by using propane-air as the fuel has been carried out. The results show that: as the propagation distance increases, there is a trend for the out-field arc shaped shock wave to transform into plane wave, and the applied pressure tends to be similar from the axis outward, and the time it acts on the ash accumulation surface also tends to be similar. When the external shock wave acts on the ash accumulation surface of the non-convective tube bundle, except for the positive reflection at the axial opposite position, which generates one pressure peak, the other positions mainly generate two pressure peaks due to oblique reflection. The ratio (diameter ratio) between the diameter of the tail outlet and the diameter of the detonation chamber is 1, the pressure peak of inert shock wave in the out-field is the largest. Increasing or decreasing the out diameter of the tail will weaken the action of the inert shock to different degrees. For diameter ratio smaller than 1, the pressure peak of the inert shock increases with increasing diameter ratio, while for diameter ratios larger than 1, decreases with increasing diameter ratio.

Performance analysis of pulse detonation ramjet

Abstract A Pulse Detonation Ramjet (PDR) performance evaluation model is established based on the component-based method. The influence law of working parameters of pulse detonation combustor (PDC), PDR geometry parameters, flight speed and altitude on the performance is analyzed. Results are as follows. (1) With the increase of the equivalent ratio, the PDR specific thrust first increases and then decreases, reaching a maximum value around 1.2, but the fuel specific impulse always decreases; (2) The change of inlet throat cross-sectional area has little effect on specific thrust and fuel specific impulse, but the increase of nozzle throat cross-sectional area will have a negative effect; (3) PDR specific thrust and fuel specific impulse increase first and then decrease with the increase of flight Mach number and altitude; (4) Compared with a ramjet engine, the advantage range of PDR can reach 18.04 %, but gradually decreases with the increase of Mach number.

Investigation of Spray Characteristics for Detonability: A Study on Liquid Fuel Injector and Nozzle Design

Detonation engines are gaining prominence as next-generation propulsion systems that can significantly enhance the efficiency of existing engines. This study focuses on developing an injector utilizing liquid fuel and a gas oxidizer for application in detonation engines. In order to better understand the spray characteristics suitable for the pulse detonation engine (PDE) system, an injector was fabricated by varying the Venturi nozzle exit diameter ratio and the geometric features of the fuel injection hole. Analysis of high-speed camera images revealed that the Venturi nozzle exit diameter ratio plays a crucial role in determining the characteristics of air-assist or air-blast atomization. Under the conditions of an exit diameter ratio of Re/Ri = 1.0, the formation of a liquid film at the exit was observed, and it was identified that the film’s length is influenced by the geometric characteristics of the fuel injection hole. The effect of the fuel injection hole and Venturi nozzle exit diameter ratio on SMD was analyzed by using droplet diameter measurement. The derived empirical correlation indicates that the atomization mechanism varies depending on the Venturi nozzle exit diameter ratio, and it also affects the distribution of SMD. The characteristics of the proposed injector, its influence on SMD, and its velocity, provide essential groundwork and data for the design of detonation engines employing liquid fuel.

Numerical Evaluation of Varying Combustion Chamber Length on the Performance of Pulse Detonation Engine Using DES Model

Numerical Evaluation of Varying Combustion Chamber Length on the Performance of Pulse Detonation Engine Using DES Model

Influence of aerodynamic valve structural parameters on detonation initiation and back pressure characteristics of air-breathing pulse detonation engine

In order to enhance the stability of detonation initiation in air-breathing pulse detonation engines (APDE), while simultaneously mitigating the non-stationary back pressure disturbance due to the huge pressure gain in the APDE, a central blunt body aerodynamic valve (aero-valve) was developed and tested with a single-tube pulse detonation combustor (PDC). The detonation initiation and back pressure characteristics of PDC were then discussed. In order to reveal the influence of the aero-valve's structural parameters on the cold-state filling, detonation initiation, and back pressure characteristics of PDC, numerical simulations were carried out based on the experimental setup. The numerical results indicated that the cold-state flow characteristics within the aero-valve was predominantly influenced by the inner diameter of the aero-valve shell (Das), while the cold-state flow inside the combustor was primarily dominated by the axial distance from the thrust wall to the aero-valve shell (Lx) and the inner diameter of the aero-valve outlet (dout). And dout has a larger impact on the cold-state flow inside the combustor. During the hot state, reducing Lx or dout is beneficial for both the generation of detonation and the suppression of back pressure, with the most significant gain effect coming from decreasing dout. The optimal combination scheme for the aero-valve is identified as Das/R = 4.5, Lx/R = 0.25 and dout/R = 0.7, where R is the detonation combustor radius. The PDC equipped with this optimized aero-valve not only has better detonation initiation characteristics, but also a smaller pressure oscillation ratio.

Effects of Copper Foam Wall/Obstacles on the Deflagration-to-Detonation Transition

To investigate the process of deflagration-to-detonation transition (DDT) of the copper foam wall in the pulse detonation engine, detonation combustion experiments were carried out using ethylene and oxygen-enriched air (oxygen concentration: 40%) as fuel and oxidant. The effects of copper foam pore size, thickness, installation length, and structure on the flame acceleration were studied experimentally, as were the effects of blockage ratio and mixture equivalence ratio. The results show that among the four pore sizes selected, the 10 PPI case produces the fastest flame development on the porous flat wall. For conditions with successful detonation, the 10 PPI case reduces the DDT distance and time by 34.97 and 42.57%, respectively, compared with the 40 PPI case. Regarding the installation length of copper foam, it is found that copper foam with a large pore size (10 PPI) and a short installation length achieves stable detonation. The general structure of copper foam was also analyzed, including the porous flat wall, porous obstacle, and solid obstacle with the same installation length. These three structures effectively accelerate the initiation of detonation. Particularly, porous obstacles show more pronounced effects on flame acceleration than the commonly used solid obstacles. These results are instructive for optimizing the short-distance ignition ability of pulsed detonation engines.

Primary investigation on Ram-Rotor Detonation Engine

The study presents a new type of detonation engine called the Ram-Rotor Detonation Engine (RRDE), which overcomes some of the drawbacks of conventional detonation engines such as pulsed detonation engines, oblique detonation engines, and rotating detonation engines. The RRDE organizes the processes of reactant compression, detonation combustion, and burned gas expansion in a single rotor, allowing it to achieve an ideal detonation cycle under a wide range of inlet Mach numbers, thus significantly improving the total pressure gain of the propulsion system. The feasibility and performance of RRDE are discussed through theoretical analysis and numerical simulations. The theoretical analysis indicates that the performance of the RRDE is mainly related to the inlet velocity, the rotor rim velocity, and the equivalence ratio of reactant. Increasing the inlet velocity leads to a decrease in the total pressure gain of the RRDE. Once the inlet velocity exceeds the critical value, the engine cannot achieve positive total pressure gain. Increasing the rim velocity can improve the total pressure gain and the thermodynamic cycle efficiency of RRDE. Increasing the equivalence ratio can also improve the thermodynamic cycle efficiency and enhance the total pressure gain at lower inlet velocities. While at higher inlet velocities, increasing the equivalence ratio may reduce the total pressure gain. Numerical simulations are also performed to analyze the detailed flow field structure in RRDE and its variations with the inlet parameters. The simulation results demonstrate that the detonation wave can stably stand in the RRDE and can adapt to the change of the inlet equivalence ratio within a certain range. This study provides the preliminary theoretical basis and design reference for the RRDE.

Gasification of Liquid Hydrocarbon Waste by the Ultra-Superheated Mixture of Steam and Carbon Dioxide: A Thermodynamic Study

The thermodynamic modeling of waste oil (WO) gasification by a high-temperature gasification agent (GA) composed of an ultra-superheated H2O/CO2 mixture is carried out. The GA is assumed to be obtained by the gaseous detonation of fuel–oxidizer–diluent mixture in a pulsed detonation gun (PDG). N-hexadecane is used as a WO surrogate. Methane or the produced syngas (generally a mixture of H2, CO, CH4, CO2, etc.) is used as fuel for the PDG. Oxygen, air, or oxygen-enriched air are used as oxidizers for the PDG. Low-temperature steam is used as a diluent gas. The gasification process is assumed to proceed in a flow-through gasifier at atmospheric pressure. It is shown that the use of the detonation products of the stoichiometric methane–oxygen and methane–air mixtures theoretically leads to the complete conversion of WO into a syngas consisting exclusively of H2 and CO, or into energy gas with high contents of CH4 and C2-C3 hydrocarbons and an LHV of 36.7 (fuel–oxygen mixture) and 13.6 MJ/kg (fuel–air mixture). The use of the detonation products of the stoichiometric mixture of the produced syngas with oxygen or with oxygen-enriched air also allows theoretically achieving the complete conversion of WO into syngas consisting exclusively of H2 and CO. About 33% of the produced syngas mixed with oxygen can be theoretically used for PDG self-feeding, thus making the gasification technology very attractive and cost-effective. To self-feed the PDG with the mixture of the produced syngas with air, it is necessary to increase the backpressure in the gasifier and/or enrich the air with oxygen. The addition of low-temperature steam to the fuel–oxygen mixture in the PDG allows controlling the H2/CO ratio in the produced syngas from 1.3 to 3.4.