Detonation Chamber Research Articles

REALIZATION OF CONTINIOUSLY ROTATING DETONATION FOR SYNGAS-AIR MIXTURES

Numerical simulation of continuously rotating detonations (CRD) of stoichiometric two-fuel mixture with air has been carried out for the cylindrical annular detonation chamber (DC) of the rocket-type engine. Thesyngas (1 - α)óO + αH2, a binary mixture of hydrogen H2 and carbon monoxide CO, is taken as a fuel. The global flow structure in the DC and the detailed structure of the transverse detonation wave (TDW) front in thecontinuously rotating regime have been studied. Integral characteristics of the detonation process - the distribution of average values of static and total pressure along the length of the DC - and the value of specific impulse on the DC exit have been obtained. The regions of existence of stable CRD regime in coordinates “stagnation pressure pm - stagnation temperature Tm” in the injection manifold (receiver) have been determined. The minimal values of the DC length and radius for CRD for some regions at the pm-Tm plane have been found.

Experimental study on wave propagations in a rotating detonation chamber with different outlet configurations

To improve the propulsive performance, exhaust nozzles are desired for rotating detonation engines in practical applications. Therefore, their effects on the upstream behaviors inside the combustion chamber are required to be clarified. This study focuses on the characteristics of rotating detonation waves influenced by different outlet configurations. Three types of aerospike nozzle configurations are developed with different throat areas. Ethylene and oxygen-enriched air with an oxygen volume fraction of 50% are utilized in this study. When nozzles are employed, five wave propagation modes (i.e., the single-wave mode, the counter-rotating wave mode, the self-adjustive mode, the periodic oscillation mode, and the deflagration mode) are observed with the equivalence ratio ranging from 0.33 to 1.39, while only single-wave mode appears in the nozzle-less case under the same operating conditions. When increasing the equivalence ratio or reducing the nozzle throat area, those unstable propagation modes are more likely to happen and three boundaries of the equivalence ratio for the wave propagation transformation are clarified. On the contrary, the standard deviations of propagation velocities in the stable propagation process are smaller when employing nozzle configurations compared to the nozzle-less cases, which indicates a more stable state of the wave propagation although the stable propagation range is narrowed. Besides, the pressure rise and specific thrust are analyzed under different outlet configurations.

Numerical simulation of the influence of confined multi-point ignited H2–O2 mixture on the propagation of shock waves towards a deformable plate

The study of shock wave propagation in a detonation chamber is of great importance as a part of the plate forming process. Investigations related to the effects of premixed gas detonation on the deflection of a plate require in-depth examination. An Eulerian-Lagrangian numerical simulation is conducted using the space-time conservation element and solution element method of LS-DYNA software to study the effect of confined multi-point ignited gaseous mixture on the dynamic response of thin plates clamped at the end of a combustion chamber. The FSI couples a Lagrangian finite element solver with a Eulerian fluid solver in a 2D space with detailed chemistry of H2–O2 mixture. The solution contains the detonation wave propagation through the combustion chamber and its interaction with the plate. The influence of variation in the multi-point ignition locations and combustion chamber dimensions on the pressure history and plate deflection is studied. To verify the model, a comparison with the experimental study is carried out using an adjustable model representative of the real experiment. The verified model is used to link the evolution of plate shape with the arrival time and intensity of shock waves within the chamber. It is found that a longer distance between the ignition point and the plate intensifies the ultimate deflection of the plate. In addition, a fairly large combustion area employed in a direction rather than transverse to the plate surface is unable to influence the ultimate deformation of the plate.

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.

Numerical Investigation on the Height of Detonation Wave in Rotating Detonation Engine

Three-dimensional numerical simulations were conducted on a non-premixed rotating detonation engine (RDE) with different exhaust nozzles (i.e. without a nozzle, with a divergent nozzle, with a convergent nozzle, and with a Laval nozzle). Aside from describing the flow-field structure inside the chamber, the detonation wave height of the detonation wave, and the outlet Mach number were also investigated. It is found that the convergent and Laval nozzles make the flow-fields more complex in chamber by the reflected shock waves. The height rises with the increase of air mass flow rate when detonation chamber exit is in choke state, but it decrease when detonation chamber exit is not in choke state.

Effects of Reversed Shock Waves on Operation Mode in H2/O2 Rotating Detonation Chambers

Operation modes are an important topic in the research of Rotating Detonation Chamber (RDC) as it can affect the stability of RDC. However, they have not been discussed in detail due to the limitation of measurement means in experiments. The aim of this research is to investigate the mechanism of different operation modes by numerical simulation. In this paper, a numerical simulation for RDCs with separate injectors is carried out. Different operation modes and mode switching are analyzed. There is a series of reversed shock waves in the flow field. It was found that they have great effects on operation mode and mode switching in RDCs. A reversed shock wave can transit into a detonation wave after passing through isolated fresh gas region where fresh gas and burnt gas distribute alternatively. This shock-to-detonation transition (SDT) phenomenon will influence the ignition process, contra-rotating waves mode and mode switching in RDCs. SDT makes the number of detonation wave increases, resulting in multi-wave mode with one ignition. Moreover, quenching of detonation waves after collision and SDT after passing through isolated fresh gas region are the mechanism of contra-rotating waves mode in RDCs with separate injectors. In addition, when the inlet total temperature increases, a shock wave is easier to transit into a detonation wave. The distance that a shock wave travels before SDT decreases when temperature increases. This will result in mode switching. Therefore, SDT determines that there is a lower bound of detonation wave number.

Numerical study of continuously rotating detonation in two-fuel gaseous mixture

Numerical simulation of continuously rotating detonations of stoichiometric two-fuel mixture with air has been carried out for the cylindrical annular detonation chamber (DC) of the rocket-type engine. The syngas (1-α)СO+αH2, a binary mixture of hydrogen H2 and carbon monoxide CO, is taken. We studied the global flow structure in DC, and the detailed structure of the transverse wave (TW) front in the continuous rotating regime. Integral characteristics of the detonation process − the distribution of average values of static and total pressure along the length of the DC, and the value of specific impulse have been obtained. The region of existence of stable continuous detonation regime in coordinates of the stagnation pressure - temperature in injection manifold (receiver) and the geometric limit of stable TW have been determined.

Ежекторний детонаційний двигун на екологічно чистих компонентах палива

The subject of research in the article is engines operating on the detonation principle of converting the energy of the working fluid. In recent years, there has been an exponential growth in the number of scientific papers devoted to detonation engines, and the most promising direction is the study of detonation engines with an ejector nozzle (EN). The work aims to obtain the results of studies of the defining characteristics of a detonation engine with an ejector nozzle. The main tasks are the scientific analysis of the working process of the pulse detonation engine with EN; modeling of working processes occurring in the flow path of the engine; numerical implementation of a mathematical model and a computational experiment. Methods, for the numerical implementation of the model of a detonation engine with an ejector, a finite-difference TVD scheme of the second order of accuracy was used. According to the results of the work performed, we observe two regions on the pressure curves, within which the pressure remains unchanged for a certain time interval (pressure plateau). An increase in the length of the ejector leads to an increase in the duration of the stage of the outflow of detonation products from the flow path of the engine, an increase in the added mass of atmospheric air, and contributes to a significant increase in the specific impulse of thrust. The value of the thrust impulse was obtained by integrating the excess pressure on the traction wall over time. Conclusions. The scientific novelty is as follows. The change in pressure overtime on the traction wall of the detonation chamber when using cylindrical EHs of different lengths was investigated by the method of numerical simulation. The value of the thrust coefficient of the ejector nozzle for the starting conditions is obtained. The studies carried out in this work are aimed at analyzing the operating mode of a promising propulsion system and are aimed at modeling the gas-dynamic processes of a pulsed detonation engine with an ejector to obtain the data necessary for preliminary design, consideration of alternative design options, and an operational assessment of the possible characteristics of an engine with an ejector. The main advantages of the engine are the ultra-high-speed of energy release in the detonation process, which leads to an increase in the efficiency of the thermodynamic cycle, simplification and cost reduction of the design, and a significant gain in in-flight performance.

Effect of fill flow rate on flame acceleration in a detonation channel

In a pulse detonation engine, filling fresh reactive mixtures into the detonation chamber is an indispensable process. The fill flow rate would significantly influence the subsequent flame acceleration and detonation initiation processes. Nevertheless, the existing works regarding the flame acceleration and detonation initiation are mostly performed on the quiescent mixtures. This work, therefore, investigates the effect of fill flow rate on the flame acceleration process in a square cross-section, obstructed detonation channel. Ethylene was utilized as the fuel, and oxygen-enriched air with an oxygen volume fraction of 40% as the oxidizer. The flame acceleration processes of quiescent and moving mixtures were observed by high-speed Schlieren and chemiluminescence techniques. It was found in this work that the fill flow rate dominates the flame propagation in the early stage of the flame acceleration (i.e., to the sound velocity of reactants). The initial flame structures vary from smooth (quiescent) to wrinkled (50 g/min) and cellular (100 g/min and 150 g/min), and to turbulent (200 g/min) with the increase of the fill flow rate. The Schlieren measurements of the filling processes show that the flow instabilities and the shear layer shedding from the obstacle surfaces into the mainstream are responsible for the promoted flame acceleration in high fill flow rate cases.

A new 365-litre dust explosion chamber: Design and testing

The explosions of combustible dusts pose a hazard in many industries. Several serious accidents have resulted in material damage, impaired environment, and the losses of human lives. Specific equipment has been developed to determine the explosive properties of dispersed dusts; their requirements are specified in EN 14034 and ASTM 1226 standards. These standards specify the use of the equipment in the volume of 1 m3 and 20 L.This paper deals with redesigning and testing a detonation chamber for the study of dispersed dust. It presents technical solutions to redesigning the detonation chamber of KV 150M2 type to a new 365 L dust explosion chamber. The article describes the technical solution to the dispersing, control and timing system. Finally, comparative measurements in the redesigned detonation chamber with the commercially available 20 L sphere are described. The samples of lycopodium, hard coal, beech wood, magnesium and urotropin powders were used to compare the results.

Numerical study of detonation flows in a supersonic annular chamber

The presented paper is devoted to the study of detonation structures in a flow-type supersonic chamber of a new design, previously proposed by us. The detonation chamber is an annular cylindrical channel located between the inner and outer cylindrical walls. The oblique detonation wave is formed by a compression body inside the annular channel, shaped as a continuous monofilar helix with a constant pitch angle. Numerical simulations are performed for a supersonic flow of a stoichiometric hydrogen-air mixture with inflow Mach number M0=3 and the pitch angle a<aCJ. A mathematical model of the reacting flow in the combustor is developed in a two-dimensional unsteady formulation. A two-stage model of the detonation kinetics is used to describe the chemical process in reacting gas. The flow evolution for the different conditions for starting the detonation chamber operation is numerically studied. The final structures of the steady flow in the combustor are obtained. The bifurcation effect of a stationary solution according to the initial conditions of the problem is discovered for some combinations of the geometric parameters of the detonation combustor.

Numerical investigation of the operating process in an annular detonation chamber of low diameter

Burning in unsteady rotating detonation waves is one of the ways of operating process organization in future aircrafts engines. However, a minimum combustion chamber diameter in which the unsteady rotating detonation process can be actualized is a significant limitation of such engines. A possibility of hydrogen-air mixture burning in an annular chamber with a diameter of 78 mm is shown in this paper using methods of three-dimensional computational fluid dynamics. The geometry of the chamber and the modes of its operation were selected, and the influence of the total pressure of air at the inlet was studied. At the pressure of 32 bar, the mass flux in the critical section of the aerodynamic nozzle was 7349.2 kg/(s·m2). It is shown that in a rotating reference frame in which the detonation wave is at rest, streamlines come to the wavefront almost at right angles. This fact allows making simple estimates of the fresh mixture parameters in front of the wave. Comparison with the detonation parameters in a premixed hydrogen-air mixture in the tube showed that the velocity of the detonation wave in the chamber is 0.65-0.74 of the Chapman-Jouguet detonation velocity, and its height is approximately equal to the characteristic size of the cellular structure of the detonation.

Numerical Modeling of the RDE

Abstract The idea of using the phenomenon of rotating detonation to propulsion has its roots in fifties of the last century in works of Adamson et al. and Nicholls et al. at the University of Michigan. The idea was recently reinvented and experimental research and numerical simulations on the Rotating Detonation Engine (RDE) are carried in numerous institutions worldwide, in Poland at Warsaw University of Technology (WUT) since 2004. Over the period 2010-2014 WUT and Institute of Aviation (IOA) jointly implemented the project under the Innovative Economy Operational Programme entitled ‘Turbine engine with detonation combustion chamber’. The goal of the project was to replace the combustion chamber of turboshaft engine GTD-350 with the annular detonation chamber. This paper is focused on investigation of the influence of a geometry and flow conditions on the structure and propagation stability of the rotating detonation wave. Presented results are in majority an outcome of the aforementioned programme, in particular authors’ works on the development of the in-house code REFLOPS USG and its application to simulation of the rotating detonation propagation in the RDE.

Study on the performance of a rotating detonation chamber with different aerospike nozzles

To generate thrust efficiently is the ultimate objective of developing a practical propulsion device utilizing detonation. The rotating detonation engine shows its great potentials because of pressure gain combustion is produced while detonations rotate inside the chamber. In order to improve the propulsive performance of a rotating detonation engine, investigations have been carried out theoretically and experimentally focusing on aerospike nozzles. A method of designing aerospike nozzles for the rotating detonation chamber was proposed. Three aerospike nozzles, with different geometry structures including conical and flat configurations and design pressure ratios, were developed in different design points. Compared to the nozzle-less condition, three operation modes have been obtained in the combustion chamber with nozzles. The results indicate that the reflected wave caused by the convergent section will induce the generation of multiple waves. The pressure gains in the combustion chamber were varied with different nozzle geometries. The propulsive performance of the conical configuration nozzle was better than the flat one. In addition, with the increase of the mass flow rate, the thrust was increased for all the cases while the maximum specific impulse was achieved at a flow rate of 0.190 kg/s.

Time-resolved, single-ended laser absorption thermometry and H2O, CO2, and CO speciation in a H2/C2H4-fueled rotating detonation engine

Rotating detonation engines (RDEs) require novel diagnostic tools to better understand complex detonation behavior and improve performance. To this end, a single-ended laser absorption sensor for in situ, time-resolved measurements of temperature, H2O, CO2, and CO concentrations has been developed and deployed within the annulus of a hydrogen/ethylene/air-fed RDE. With a measurement rate of 44 kS/s, the sensor delivers four co-aligned, mid-infrared laser beams into the annular detonation chamber and captures the back-reflected radiation through a single optical port. A ray-tracing optimization algorithm, designed to maximize signal-to-noise ratio and beam-perturbation tolerance, was used to determine the optimal sensor optical configuration. Wavelength-modulation spectroscopy (WMS) further compensated for interference sources in the harsh detonation environment. Time-resolved and time-averaged sensor measurements of gas temperature and species at equivalence ratios of 0.74, 0.87, and 1.03 are presented.

Influence of Gaseous Hydrogen Addition on Initiation of Rotating Detonation in Liquid Fuel–Air Mixtures

Hydrogen is the most common molecule in the universe. It is an excellent fuel for thermal engines: piston, turbojet, rocket, and, going forward, in thermonuclear power plants. Hydrogen is currently used across a range of industrial applications including propulsion systems, e.g., cars and rockets. One obstacle to expanding hydrogen use, especially in the transportation sector, is its low density. This paper explores hydrogen as an addition to liquid fuel in the detonation chamber to generate thermal energy for potential use in transportation and generation of electrical energy. Experiments with liquid kerosene, hexane, and ethanol with the addition of gaseous hydrogen were conducted in a modern rotating detonation chamber. Detonation combustion delivers greater thermal efficiency and reduced NOx emission. Since detonation propagates about three orders of magnitude faster than deflagration, the injection, evaporation, and mixing with air must be almost instantaneous. Hydrogen addition helps initiate the detonation process and sustain continuous work of the chamber. The presented work proves that the addition of gaseous hydrogen to a liquid fuel–air mixture is well suited to the rotating detonation process, making combustion more effective and environmentally friendly.

Study on operation and propulsion features of a pulse detonation rocket engine with secondary oxidizer injection

To explore an effective method which can help to reduce the pressure and velocity fluctuations and promote the utilization of kinetic energy in the exhaust products of a pulse detonation chamber, a secondary oxidizer injection method has been proposed and investigated experimentally. A gasoline based valveless pulse detonation system was employed and it operated stably from 10 to 50 Hz. With the extra injection, pressure and velocity fluctuations of the detonation products were reduced dramatically, and a thrust increment up to 29.5% was achieved on the same account of fuel. It provides a new way to promote the propulsion performance of pulse detonation engines beyond the traditional methods, e. g. nozzle and ejector optimization. Moreover, it can be used as a supplement to nozzles, by the combination of a fluidic nozzle, a maximum thrust increase of 75.9% was obtained in this study. The reduction of pressure and velocity fluctuations is believed to provide most of the benefits on thrust improve, and stratified fuel distribution, after-burning, and partial-fill effects are also main reasons especially in higher frequencies.

Detonation Structure in Ethylene/Air-Based Non-Premixed Rotating Detonation Engine

Rotating detonation engines (RDEs) are gaining significant interest as a practical approach to increasing the operating efficiency of propulsion systems through pressure gain combustion. To use RDEs in practical gas turbines, their stability and performance with regard to hydrocarbon fuels need to be tested. Prior experimental work has shown that ethylene/air systems exhibit suppressed wave propagation, with speeds that are nearly half the ideal wave speeds. The purpose of this study is to simulate realistic RDE configurations that have been experimentally studied to gain insight into this wave suppression. Detailed numerical simulations using a reduced 8-species 2-step and a 21-species 38-step chemistry model are conducted. When ethylene is diluted with hydrogen, the system reaches a stable mode comparable to detonation propagation after unsteady transition period between a weak deflagrative and a stronger detonation mode. It is further shown that pure ethylene cases stay in the weak regime with weak pressure propagation aided by deflagration along the wave path. Species, temperature, and pressure profiles normal to the wave front show a weak pressure rise followed by a broad reaction zone. As a result, heat release is not confined to the near-shock region but is distributed across the detonation chamber.

ОСОБЛИВОСТІ КОНСТРУКТИВНИХ СХЕМ ДВИГУНІВ З ІМПУЛЬСНИМИ ДЕТОНАЦІЙНИМИ КАМЕРАМИ

The pressure of the products of chemical reactions in the chamber of a rocket engine increases significantly if the rocket fuel components burn in the detonation mode. In this case, it can get to a simpler and more reliable expulsion propellant feed system instead of a turbopump feed system. The value of heat release power (MW / liter) of detonation engines is several orders of magnitude larger than that of aircraft and rocket engines operating in the Brighton cycle. The high rate of energy released in the detonation mode can significantly reduce the mass, the inertia, and overall dimensions of the propulsion system. Due to these features, detonation chambers are advisable to be used as part of ejector pulsed detonation engines, together with a turbine – in electric power generators of spacecraft, in a hybrid design – together with turbofan or turboprop engines, etc. In the article are considered various design schemes of pulse detonation engines (PDE): single-chamber and multi-chamber pulsed detonation engines; an ejector PDE system; a hybrid PDE and an integrated detonation-turbine unit with a detonation chamber in the form of a spiral and with a multi-chamber detonation device. The possibility of pulsation frequency increase is realized in the multi-chamber pulsed detonation engine, and the possibility of thrust size increase is realized in PDE with ejector. Replacing traditional chambers with detonation chambers in the construction of gas turbine jet engine will allow providing a decrease in propellant flow rate value from 8 % to 10 % on some estimations. In the hybrid detonation propulsion plant advantages inherent to the detonation cycle combine with positive features of a turbo-compressor jet engine. A combination of PDE and turbine allows creating the cogeneration propulsion system in that a turbine is used for the production of electric power, and detonation chamber – for the creation of thrust impulse. Practical realization of hybrid pulse detonation turbo-engine and the integrated detonation-turbine device is possible if two key complex problems will be solved. These problems are the detonation waves weakening on input in a turbine and the bearing and shaft necessary work resource increasing into a detonation pulsating stream

Structural response and wall thickness design of pulse detonation combustor

This paper deals with the structural response and wall thickness design of pulse detonation combustor. The pulse detonation combustor is a chamber with cylindrical shell structure, which is loaded with internal moving detonation pressure and thermal load. Much higher strain and stress can be excited under moving pressure load than static load. How to choose the attenuation coefficient during detonation pressure were discussed. The results of structural response simulation based on finite element method were compared with analytical result in the literature. The multi-cycle detonation pressure load and thermal load were measured on a pulse detonation engine principle prototype initialed through deflagration-to-detonation transition for the first time. The structural response characteristics of the detonation chamber were studied based on the measured load under different working frequencies. A series of comparison between numerical simulation and experimental measurement were carried out. The wall thickness of the chamber was designed based on the fatigue load spectrum under real detonation load and the chamber’s target fatigue life. Special attention was paid to the mutual influence between the dynamic amplification factor and the wall thickness.