Rotating Detonation Wave Research Articles

Experimental investigation on detonation combustion patterns of hydrogen/vitiated air within annular combustor

Experiments on continuous rotating detonation (CRD) were performed using hydrogen and vitiated air with total temperature of 860K. Two types of detonation phenomenon were found, namely, continuous rotating detonation wave (CRDW) traveling azimuthally in the annular detonation combustor, and detonation wave (DW) propagating along the detonation combustor axial direction. For the CRDW, four different combustion patterns existed, namely, one wave in homo-rotating mode, two waves in homo-rotating mode, one couple in hetero-rotating mode and two couples in hetero-rotating mode. For DW propagating axially, it was like pulse detonation engine (PDE), but do not need repeated ignition. Besides, the DW propagated upstream, and worked with a higher frequency than PDE. The experiments showed that the DW could be sustained continuously and steadily in all the five patterns within annular combustor, requiring no repeated ignition.

MEASUREMENTS OF PRESSURE IN FRONT OF SHOCK WAVE – ASSESSMENT OF METHODOLOGY INFLUENCE ON THE MEASUREMENT RESULTS ON THE BASIS OF EXPERIMENTS WITH THE SHOCK TUBE

The experiments, described in the article, are related to research of a rotating detonation that has been conducted in the Institute of Aviation in Warsaw since 2009, under the OPIE project: “Turbine engine with detonation combustion chamber”. Measurements of the shock wave parameters, are among the most difficult in the art. This is due to high speed of the wave transition, and above all, a very small thickness of the shock wave. For the purposes of the mentioned project, a methodology for measuring pressure on the rotating detonation wave was developed. It included the type of sensors, their location and their protection from heat and flames. In order to determine the capabilities, limitations and accuracy of the method that was used, a series of experiments were planned and carried out. They enabled the assessment of the impact, on the measurement of pressure in the shock wave, of the following factors: the location of the sensor (frontal and lateral) relative to the shock wave front, protrusion or retraction of the sensor in its housing, the covering of the sensor with a protective layer (such as a high temperature silicon). This paper presents the results of the experiments that were carried out with use of a small shock tube of a simple design. The high-pressure part of the tube (so-called “driver”) was charged with the compressed nitrogen gas. The membrane was designed to be torn by pressure and pressure magnitude of the shock wave were measured by a “twin pair” of the Kistler 603B type piezoelectric sensors, one of which was always the reference sensor.

НЕКОТОРЫЕ АСПЕКТЫ РЕГИСТРАЦИИ И ДЕШИФРОВКИ ВРАЩАЮЩИХСЯ ДЕТОНАЦИОННЫХ ВОЛН

НЕКОТОРЫЕ АСПЕКТЫ РЕГИСТРАЦИИ И ДЕШИФРОВКИ ВРАЩАЮЩИХСЯ ДЕТОНАЦИОННЫХ ВОЛН

An experimental study on CH4/O2 continuously rotating detonation wave in a hollow combustion chamber

CH4/O2 continuously rotating detonation waves (CRDWs) have been experimentally achieved in a special model with a hollow combustion chamber rather than a typical cylindrical annular chamber. Experiments were conducted at atmospheric backpressure and under various injection conditions (different mass flow rates of CH4/O2 gaseous mixture). The injection conditions, together with the time domain and frequency domain characteristics of the high frequency pressure, have been analyzed. A high speed camera was employed to roughly record the reaction zone structure. Results show that for the given test mode working with lower mass flow rates – 38gs−1 CH4 and 131.7gs−1 O2 (leading to an equivalence ratio of 1.154), CRDWs occurred but were not stably propagating. In contrast, stably propagated CRDWs were observed in a four-wave mode when mass flow rates were increased to 36.1gs−1 CH4 and 217.2gs−1 O2 (leading to an equivalence ratio of 0.665). The corresponding average frequency and average velocity of the CRDWs were 19.251kHz and 1512ms−1, respectively. FFT and STFT discussions on the high-frequency pressure history of CRDWs validated the stability of rotating detonation waves in the hollow chamber. This study further verified the feasibility of triggering the CRDW in a unique hollow combustion chamber through annular injection distribution. Injecting enough combustible mixture is the essential condition for sustaining a stable CRDW.

Experimental study on propagation mode of H2/Air continuously rotating detonation wave

The propagation mode of H2/Air continuously rotating detonation waves (CRDWs) has been experimentally studied in a rotating detonation engine (RDE) model which injected gaseous H2 and Air in slit-orifice collision mode. Experiments were conducted by varying injection conditions (different mass flow rates and equivalence ratio) at atmospheric backpressure, and thereby four typical detonation propagation modes were concluded. Moreover, the injection conditions, as well as the time domain and frequency domain characteristics for each mode were detailedly analyzed. Results show that: for the test model with an oxidizer injection throat of 0.4 mm wide, H2/Air CRDW usually propagated in an one-way mode as the mass flow rate increased, which in sequence included three sorts of mode: single wave mode, single/dual-wave hybrid mode, and dual-wave mode. However, after the blow-off N2 was injected and the H2 flow began to decrease, the detonation was possible to be maintained in a special dual-wave collision mode. This collision mode was more likely to be observed in the test model with a narrower oxidizer injection throat of 0.2 mm wide. At lower mass flow rate, CRDWs tended to show unstable dual-wave collision mode, and the collision points slowly moved back and forth within a small azimuthal angle; with the mass flow rate increasing, the collision points remained stable and CRDWs propagated in stable dual-wave collision mode.

Rotating Detonation Instabilities in Hydrogen-Oxygen Mixture

Rotating detonation engines are studied more and more widely because of high thermodynamic efficiency and high specific impulse. Rotating detonation of hydrogen and oxygen was achieved in this study. Rotating detonation waves were observed by high speed cameras and detonation pressure traces were recorded by PCB pressure sensors. The velocity of rotating detonation waves is fluctuating during the run. Low frequency detonation instabilities, intermediate frequency detonation instabilities and high frequency detonation instabilities were discovered. They are relevant to unsteady heat release, acoustic oscillations and rotating detonation waves.

Induction for multiple rotating detonation waves in the hydrogen–oxygen mixture with tangential flow

Abstract Rotating detonation engines are studied more and more widely because of high thermodynamic efficiency and high specific impulse. Generally one detonation wave exists in the engines but sometimes multiple detonation waves appear, as is complicated and difficult to explain. Increasing the number of rotating detonation waves uniforms the flow field and weakens the combustion instabilities. A controllable way to induce multiple detonation waves is introduced here. Rotating detonation engine runs with a single detonation wave or multiple detonation waves were both conducted. Pressure sensors were used to record the pressure traces of rotating detonation waves and gas flow controllers controlled the flow rates of reactants. Tangential flow of reactants from the predetonator produces shock waves moving upstream, inducing multiple rotating detonation waves when there is axial flow of reactants from the head of the combustor. The maximum number of detonation waves is subject to the flow rates.

Experimental Research on the Propagation Process of Continuous Rotating Detonation Wave

Abstract In order to study the propagation mechanism of continuous rotating detonation wave, the H 2 /air continuous rotating detonation engine ignited by tangentially installed H 2 /O 2 pre-detonation tube is studied experimentally using a tilt slot injector structure. The experimental results show that the stable rotating detonation wave can be gained successfully with the equivalent ratio of 0.93. The propagation frequency and velocity of rotating detonation wave range from 5200 to 5500 Hz and from 1518.5 to 1606.1 m/s, respectively. Three propagation modes, such as rotation, reversal and bifurcation, of detonation wave are verified through the analysis of propagation mechanism of rotating detonation wave.

Experimental Study of a High-Frequency Fluidic Valve Fuel Injector

Fuel injectors composed of an ori ce connected to a small plenum cavity were mounted on a detonation tube. These fuel injectors, termed uidic valves, utilize their geometry and a supply pressure to deliver fuel and contain no moving parts. Behavior of these uidic valves is characterized in order to determine their feasibility for integration with high-frequency pulsed or rotating detonation wave engines. Fuel ow is initiated just prior to ignition of the detonation tube to understand the interaction between the uidic valves and the wave. Parametric studies have been conducted with the type of fuel injected, the ori ce diameter, and the plenum cavity pressure. Results indicate that the detonation wave pressure temporarily shuts o the uidic valve supply, but the wave products can be quickly expelled by the fresh fuel supply to allow for refueling. The interruption time of the valve scales with the injection and detonation wave pressure ratios as well as a characteristic time.

Cellular structure of detonation utilized in propulsion system

How to confine a detonation in a combustor is a key issue of detonation applications in propulsion systems. Based on achieving schemes, detonations applied in the combustor, including pulse detonation wave (PDW), oblique detonation wave (ODW) and rotating detonation wave (RDW), are different from that described by the classic CJ theory in fine structures and its self-sustaining mechanisms. In this work, the cellular structures and flow fields of ODW and RDW were obtained numerically, and the fundamental characteristics and self-sustaining mechanisms of the detonations were analyzed and discussed. ODW front consists of three parts: the ZND-like front, the single-headed triple point front and the dual-headed triple point front. Cellular structures of RDW are heterogeneous, and the cell size near the outer wall is smaller than that near the inner wall.

Airbreathing rotating detonation wave engine cycle analysis

A cycle analysis model for an airbreathing, rotating detonation wave engine (RDE) is presented. The engine consists of a steady inlet system with an isolator which delivers air into an annular combustor. A detonation wave continuously rotates around the combustor with side relief as the flow expands towards the nozzle. A model for the side relief is used to find the pressure distribution around the combustor. Air and fuel enter the combustor when the rarefaction wave pressure behind the detonation front drops to the inlet supply pressure. To create a stable RDE, the inlet pressure is matched in a convergence process with the average combustor pressure by increasing the annulus channel radial width with respect to the isolator channel. Performance of this engine is considered using several parametric studies and compared with rocket-mode computational results. A hydrogen–air RDE reaches a specific impulse of 3800 s and can reach a flight speed of Mach 5.

Numerical investigation of flow particle paths and thermodynamic performance of continuously rotating detonation engines

Based on the two-dimensional numerical simulation of continuously rotating detonations in an annular chamber, the paths of flow particles burned by three different processes are tracked and analyzed in detail. The detonation wave, the deflagration wave, the oblique shock wave, and the contact surface have a small influence on the paths of flow particles. The fluctuation of paths in the azimuthal direction is less than 12% of the circumference of the combustion chamber. The path will deflect when the flow particle encounters the detonation wave or the oblique shock wave, and it will not deflect when encounters the deflagration wave or the contact surface. About 23.6% fuel is burned by deflagration, and the left is burned by rotating detonation wave. The thermodynamic performance of continuously rotating detonations is then discussed. The p–v and T–s diagrams obtained by numerical simulation are qualitatively consistent with the ideal ZND model. The average thermal efficiency of the detonation combustion in 2D RDE is 31%, and its average net mechanical work is 1.3MJ/kg. The thermal efficiency of the entire RDE is 26.4%, and its net mechanical work is 30% of the ideal ZND model. The superior performance of continuously rotating detonations is determined.

Experimental and three-dimensional numerical investigations on H2/air continuous rotating detonation wave

Results of both experimental and three-dimensional numerical studies on H2/air continuous rotating detonation are presented. Tangentially injected H2/O2 hotshot jet was used to ignite the engine successfully. Under the condition of air and hydrogen mass flow rates of 265 and 7.7 g/s and the ambient pressure of 11 kPa, H2/air continuous rotating detonation has been realized for about 300 ms. Time–frequency characteristics of the measured results were analyzed by different methods, and the results agreed well with each other. The detonation wave propagated stably during the test, with the propagation frequency variation of 5.35–5.85 kHz. The mean propagation velocity was 1674.3 m/s, which was about 85.0% of the theoretical value. Corresponding three-dimensional numerical simulation was carried out. Flow field structure of the rotating detonation wave was analyzed, and the curvature effect was also considered. Propagation processes of both the experiment and simulation results were compared. The variation of detonation wave propagation frequency of the simulation case was 6.262–6.27 kHz, with the mean propagation velocity of 1870.1 m/s, which was larger than the experiment result. Distribution of the mean combustor pressure along the axis direction was analyzed. Within the heat release zone, the mean pressure decreased greatly, and it changed gently beyond this zone. The changing tendency of both the experimental and numerical results agreed with each other, but there were differences between the pressure values.

Change in Continuous Detonation Wave Propagation Mode from Rotating Detonation to Standing Detonation

We perform a three-dimensional numerical simulation based on a one-step chemical reaction model to investigate changes in the mode of H2-Air detonation wave propagation from rotating detonation wave (RDW) mode to standing detonation wave mode. The physical characteristics of an RDW with injection velocity of 500m/s are analyzed to investigate the physical mechanisms involved. We find that with increasing injection velocity, the detonation wave gradually changes from perpendicular to the head wall to parallel to the head wall. When the injection velocity exceeds the Chapman–Jouguet velocity VCJ (about 1984m/s), the detonation wave changes orientation to become perpendicular to the fuel injection direction, and the rotating mode changes accordingly to a standing mode. Finally, the plane detonation characteristic triple-wave structures can be found from the standing mode.

Mathematical modeling of a rotating detonation wave in a hydrogen-oxygen mixture

A two-dimensional unsteady mathematical model of spin detonation in an annular cylindrical ramjet-type combustor is formulated. The wave dynamics in the combustor filled by a hydrogen-oxygen mixture is studied numerically.

Continuous detonation combustion of fuel-air mixtures

Continuous detonation combustion of fuel-air mixtures was performed. In a disk-shaped chamber with a plane radial eddying flow directed from the periphery to the central outlet opening, a rotating detonation wave in which hydrogen, methane, and sprayed liquid fuels (kerosene and diesel fuel) mixed with air were burnt was excited. Previously, a similar process was realized only for fuel-oxygen mixtures.

Maintained detonation waves in an annular channel: A hypothesis which provides the link between classical acoustic combustion instability and detonation waves

This paper is an account of a part of a research programme carried out at Rolls-Royce Limited. The programme was directed at evaluating the benefits which may acerue by using detonation waves as the heat addition process in an airbreathing gas turbine power plant. The concept of a maintained detonation wave moving around an annulus which is continuously replenished with fresh combustibles is well known. The work is largely experimental and is directed at the attainment of a demonstration of such a maintained moving detonation wave in ethylene/oxygen/air mixtures. The detonation wave moves into fresh combustibles which are introduced through continuous inlet slits in the annular chamber wall at right angles to the direction of the propagation of the wave. The design has no moving mechanical parts, and the valving of the gas flow is achieved gas-dynamically by matching the pressure profiles behind the detonation wave to the pressure of the inflowing combustibles. The two or three supersonic combustion waves which propagate in a stable fashion have pressure ratios between 2 and 10 and velocities between 1100 and 1500 m/s. These results are functions of the energy content of the incoming combustibles and the gas dynamics of the scavenging and refilling processes. Consideration of all these results has led to the conclusion that all such waves propagating with constant velocity around a continuously replenished annular channel obey the Chapman-Jouguet hypothesis for stable detonations; the unusually low pressure ratios and velocities are accounted for by consideration of the conditions of the gas upstream of the wave which results from incomplete scavenging with fresh combustibles of the hot combustion products of the pressure wave. This explanation provides the link between maintained rotating detonation waves and classical acoustic instability.

Feasibility studies of a rotating detonation wave rocket motor.

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

The symmetry of time in physics

Rotating detonation engines are widely studied because of their compact configurations and high thermal cycle efficiency. For briefty, most of the numerical simulations of rotating detonation engines used premixed reactant mixtures. The rotating detonation waves under non-premixed condition are not studied enough. Here, a series of three-dimensional numerical simulations of a rotating detonation engine under both premixed and non-premixed conditions using H2/air mixture are performed. The explicit formulation of density-based solver in ANSYS Fluent is used to perform the simulations. Two total mass flow rates of 272.3 g/s and 500 g/s are selected. When the total mass flow rate is 272.3 g/s, the engine operates at single-wave mode under both premixed and non-premixed conditions. When the total mass flow rate is 500 g/s, the engine operates at single-wave mode under premixed condition. While under non-premixed condition, a spontaneous formation of dual-wave mode is observed. This case agrees well with the phenomenon observed in experiments that as the total mass flow rate increases, the number of rotating detonation waves tends to increase. Pressure waves caused by the high pressure behind the detonation waves can propagate upstream to the H2 and air plenums. The pressure feedback in the H2 plenum is much more obvious than that in the air plenum. Due to the imperfect mixing of H2/air and the more deflagration combustion caused by the hot detonation products, the thrust of the RDE under non-premixed condition is smaller than that under premixed condition.