Spin Detonation Research Articles

Continuous Detonation of the Liquid Kerosene—Air Mixture with Addition of Hydrogen or Syngas

Regimes of continuous detonation of heterogeneous mixtures of aviation kerosene and air with addition of hydrogen or syngas are studied in a flow-type annular cylindrical combustor 503 mm in diameter. With variations of the flow rates of air, liquid kerosene, hydrogen, and their relationships, regimes of continuous spin detonation are obtained in the following ranges: number of detonation waves 1–5, detonation wave velocity 1.15–1.67 km/s, and wave rotation frequency 0.73–4.86 kHz. In the case with addition of syngas with the composition CO + 3H2, regimes with two opposing transverse waves are obtained; the mean velocity of wave rotation is 0.66–1.47 km/s, and the frequency is 0.85–1.87 kHz. Bubbling of the gaseous fuel (hydrogen or syngas) through liquid kerosene in the fuel injection system makes it possible to reduce the mass fraction of the gas in the two-phase fuel down to 8.4% for hydrogen and 47% for syngas with the composition CO + 3H2. It is demonstrated that the minimum fraction of syngas in kerosene that still ensures the detonation regime is determined by the amount of hydrogen. Based on the stagnation pressure measured at the combustor exit, the specific impulse in the case of continuous detonation is determined as a function of the two-phase fuel composition. The maximum value of the specific impulse (about 4000 s) is obtained for the mass fraction of hydrogen in the two-phase fuel equal to 42%. The minimum diameter of the annular detonation combustor is estimated as a function of the specific flow rate of the heterogeneous mixture.

MHD effects in continuous spin detonation

Conversion possibility of the chemical energy of combustion products of a hydrogen–oxygen mixture into electrical energy with the use of continuous spin detonation has been demonstrated for the first time in an MHD system. The specific conductivity of detonation products in the region of rotation of the detonation front was measured to be ~3 · 10–2 Ω–1 m–1. The structure of transverse detonation waves was examined, their velocity was measured (2220 ± 50 m/s), and the flow in their vicinity was studied.

The propagation mechanism of detonation wave in a round tube filled with larger blockage ratio orifice plates

In this study, the detonation propagation mechanisms for the stoichiometric hydrogen-oxygen mixture are explored systematically in a circular tube with 6-m in length and an inner diameter of 90-mm. The continuous orifice plates with BR = 0.93 are adopted to investigate the characteristics of detonation diffraction, failure and initiation. High-speed piezoelectric pressure transducers are used to obtain the average velocity, and the smoked foil technique is adopted to record the detonation cellular patterns. The results indicate that three various propagation regimes can be observed, i.e., steady detonation, quasi-detonation and fast flame. In the smooth tube, only the steady detonation and fast flame modes are seen. When the initial pressure is greater than the critical value, the detonation can propagate at about the theoretical CJ velocity. Near the critical pressure, a sudden velocity drop is observed. Of note is that the single-headed spin and double-headed detonation cannot occur because of the limitation of the aspect ratio. In the tube filled with obstacles, the averaged wave velocity is decayed severely. Only the mechanisms of the quasi-detonation and fast flame can be seen. In the quasi-detonation mode, the critical value of d/λ is greater than 7.36, which is far larger than 1. Two different detonation ignition regimes produced by the shock reflection from the wall are observed, i.e., the initiation positions occur in the vicinity of the tube wall and the surface of the orifice plate.

MHD Effects in Continuous Spin Detonation

MHD Effects in Continuous Spin Detonation

Detonation of a hydrogen-oxygen gas mixture in a plane-radial combustor with exhaustion toward the periphery in the regime of oxygen ejection

The results of experimental study concerning a continuous spin detonation of hydrogen-oxygen mixture in a flow-through plane-radial combustor with a diameter of 10 cm and with exhaustion toward the periphery in the regime of oxygen ejection are presented. In the experiment, the regimes of continuous spin detonation with one and two transverse detonation waves rotating with velocity D = 1.3÷1.43 and 1.45÷1.54 km/s, measured relative to the inner cylindrical surface of the combustor, respectively, and two near-sonic waves rotating with velocities of about 0.7 km/s have been observed. The waves of pulse combustion with frequencies of 4.4 – 3.6 kHz have been found for the first time. The structure of waves and flow in their vicinity has been studied.

Continuous spin detonation of methane/hydrogen-air mixtures with additional injection of air to combustion products

Results of experimental investigations in a flow-type annular cylindrical combustor with an outer diameter dc = 503 mm are reported. The influence of air addition to products of continuous spin detonation of a CH4 + 8H2 - air mixture on detonation wave parameters, pressures in the combustor, and specific impulse is studied. The range of existence of continuous spin detonation in terms of the specific flow rate of the mixture through the combustor cross section is extended to 1360 kg/(s·m2), whereas the equivalence ratio is reduced to φ∑ = 0.4. It is shown that addition of air to detonation products up to the level of the air flow rate in the main injection system increases the velocity of continuous spin detonation, pressure in the combustor, and thrust, whereas the specific flow rate of the fuel decreases.

Continuous Detonation of Methane/Hydrogen–Air Mixtures in an Annular Cylindrical Combustor

Regimes of continuous detonation of methane/hydrogen–air mixtures in spin and opposing transverse detonation waves are obtained for the first time in a flow-type annular cylindrical combustor 503 mm in diameter. A two-component (methane/hydrogen) fuel with the H2 mass fractions of 1/9 to 1/2 in the range of specific flow rates of the mixture from 64 to 1310 kg/(s ·m2) and the fuel-to-air equivalence ratio ϕ = 0.78–1.56 is considered. In methane/hydrogen–air mixtures with two compositions of the fuel (CH4 + 8H2 and CH4 + 4H2), one-wave and two-wave regimes of continuous spin detonation are obtained; the frequency of rotation of transverse detonation waves is 0.56–1.66 kHz at ϕ = 0.78–1.02. For the fuel compositions CH4 + 2H2 and CH4 + 1.5H2, continuous multifront detonation with two opposing transverse detonation waves rotating with the frequency of 0.86–1.34 kHz at ϕ = 1.0–1.23 is obtained. For the CH4 + H2 + air mixture, both combustion in the chamber and continuous spin detonation outside the combustor with transverse detonation waves rotating with the frequency of 1.01–1.1 kHz are observed. The lean limits of continuous detonation are obtained in terms of the specific flow rate of the mixture: 64, 100, 200, and 790 kg/(s · m2) for the fuel compositions CH4 + 8H2, CH4 + 4H2, CH4 + 2H2, and CH4 + 1.5H2, respectively, for the mass fraction of hydrogen in the methane/hydrogen fuel of ≈0.16. Violation of regularity of the continuous detonation wave structure and the wave velocity with a decrease in the fraction of hydrogen in the two-component fuel is detected.

Rotating Detonations and Spinning Detonations: Similarities and Differences

Rotating Detonation Combustors are studied with increasing interest worldwide, and are seen as the most promising of the available pressure gain (stagnation) combustion concepts. The dynamics and structure of rotating detonations are an area of active interest owing to their sensitivity to a wide range of factors, which have been hard to predict. In the current manuscript, we argue that rotating detonations share a considerable number of quantitative and qualitative properties with spinning detonations, which is a well-known near-limit phenomenon in fundamental detonation studies. We show that the fill height in rotating detonations play the same role as the pitch length inscribed by spinning detonations. While the pitch-to-hydraulic diameter ratio of spinning detonations is known to range from 2 to 6 across a wide range of conditions, it is shown here, from literature, that the fill height-to-hydraulic diameter of rotating detonations also extends across a similar range—between 1 and 5 across diverse facilities and conditions.

Hydrogen-fueled detonation ramjet model: Wind tunnel tests at approach air stream Mach number 5.7 and stagnation temperature 1500 K

The mode of continuous spinning detonation (CSD) combustion of hydrogen in the annular combustor of a model of a hydrogen-fueled detonation ramjet under conditions of approach air stream Mach number 5.7 and stagnation temperature 1500 K is registered experimentally in a short-duration (pulsed) wind tunnel at the overall air-to-hydrogen equivalence ratio (ER) ranging from 0.7 to 1.4. The maximum values of thrust and specific impulse of the ramjet model are attained at ER = 1.25 and are estimated as 1550 N and 3300 s, respectively. At 1.4 < ER < 1.6, the mode of longitudinally pulsating detonation (LPD) combustion is registered with somewhat lower values of thrust and specific impulse.

Fabrication of a helical detonation channel: Effect of initial pressure on the detonation propagation modes of ethylene/oxygen mixtures

The effect of the initial gas mixture pressure on curved detonation propagation modes has been extensively investigated in the present study using a stoichiometric ethylene–oxygen mixture in a new experimental facility consisting of a straight channel section joined to a helical channel section. Flame propagation through the helical channel was observed by high-speed CCD camera, and the trajectories of triple points on the detonation waves were obtained using a soot-deposition plate. The results clearly identify three detonation propagation modes, namely, a stabilized propagation mode, critical mode, and non-stabilized propagation mode, that vary according to the ratio of the radius of curvature of the inside wall ri to the normal detonation cell width λ. For the stabilized propagation mode (ri/λ > 27), the detonation velocity at the inner wall in the curved section asymptotically approaches the detonation velocity in the straight section with increasing initial pressure due to competition between the weakening and strengthening effects characteristic of the curved channel geometry. A definite flame shape, which is perpendicular to the inner wall of the channel, is observed. For the critical mode (16 ≤ ri/λ ≤ 27), the shape of the flame front is observed to be more irregular and unstable than that of the stabilized propagation mode. This mode can be considered as a transition zone, where the stabilized propagation mode transits to the non-stabilized propagation mode with decreasing initial pressure. For the non-stabilized propagation mode (ri/λ < 16), two types of periodic detonation propagation behavior are observed. The first is analogous to single-headed spinning detonation in a circular tube, which is observed in an initial pressure range of 5.5–11 kPa. Soot-coated foil records show that the cellular structure has specific features of the periodic variation, such as re-generation, decrease, and partial disappearance of detonation near the inner wall. The angular interval of consecutive cycles for sinning-like detonation decreases with increasing initial pressure. The second is galloping detonation near the detonation propagation limit. In one cycle of galloping detonation, a change from multi-headed to single-headed cellular structure is observed. However, as the galloping detonation further decays to the low velocity phase of the galloping cycle, the cellular structure vanishes. The angular interval of consecutive cycles for galloping detonation is observed to be random. Although both spinning-like and galloping detonations periodically undergo the process of re-generation, decrease, and failure, they exhibit two different propagation behaviors. The former partially fails near the inner wall, and is re-initiated by transverse detonation from the outer wall, while the latter fails completely, and re-generates by local explosion at the outer wall.

Numerical simulation of classical and rotating detonation waves in methane mixtures

A numerical simulations of a two-dimensional multi-front irregular structure of the detonation wave (DW) in methane-based mixtures at normal initial condition have been conducted. The computations have been performed in a wide range of channel height. From the analysis of the flow structure and the number of primary transverse waves in channel, the dominant size of the detonation cell for studied mixtures has been determined. We have simulated the cellular front structure in stoichiometric methane–air and methane–oxygen mixtures, and in a rich (equivalence ratio φ = 1.5) methane-air mixture. Based on the fundamental studies of front structure of the classical propagating DW in methane mixtures, numerical simulation of continuous spin detonation of rich (ϕ = 1.2) methane-oxygen mixture has been carried out in the cylindrical detonation chamber (DC) of the rocket-type engine. We studied the global flow structure in DC, and the detailed structure of the front of the continuous rotating DW. 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 geometric limit of stable existence of rotating DW has been determined.

Continuous spin detonation of poorly detonable fuel-air mixtures in annular combustors

This paper reports on the results of experimental investigations of continuous spin detonation of three fuel-air mixtures (syngas-air, CH4/H2-air, and kerosene/H2–air in a flow-type annular cylindrical combustor 503 mm in diameter. The limits of existence of continuous detonation in terms of the specific flow rates of the mixtures (minimum values) are determined. It is found that all gas mixtures, including the least detonable methane-air mixture, with addition of hydrogen can be burned in the continuous spin detonation regime.

Continuous spin detonation of a syngas-air mixture in a plane-radial vortex combustor

Continuous spin detonation in syngas-air mixtures with three different syngas compositions [CO]/[H2] = 1/3, 1/2, and 1/1 is experimentally studied in a flow-type radial vortex combustor 500 mm in diameter. It is found that all these mixtures with three syngas compositions can be effectively burned in air in the detonation regime. Transverse detonation waves of identical structure are detected. The limits of existence of continuous detonation in terms of the specific flow rates of the mixtures (minimum values) are determined.

Detonation combustion of lignite with titanium dioxide and water additives in air

The influence of mineral additives (6.2–70%) and water (15–54%) to lignite on the possibility of its burning in an air flow in a continuous detonation regime in a radial vortex combustor 500 mm in diameter is studied. A syngas with a composition CO + 3H2 is used for transporting the coal mixture and for promoting the chemical reaction. It is shown that regimes of continuous spin detonation, conventional combustion, and pulsed combustion may occur depending on the amounts of the mineral (TiO2) added to coal, water, and syngas. The boundaries between the domains of existence of detonation and combustion are determined in the coordinates of the ratio of the syngas flow rate to the rate of consumption of the combustible portion of coal and the mineral component of coal and water. It is seen that the continuous spin detonation regime persists if the mineral additive fraction in the lignite mixture is up to 65% and the water fraction is smaller than 30%. It is also demonstrated that the syngas flow rate should be increased with increasing mineral additive fraction and increasing coal humidity in order to ensure burning of the combustible component of syngas.

An experimental study on the detonability of gaseous hydrocarbon fuel–oxygen mixtures in narrow channels

This study was performed to address the detonability related to gaseous hydrocarbon fuel–oxygen mixtures (i.e., CH4–2O2, C2H6–3.5O2 and C3H8–5O2) in different ducts (36-mm circular tube and annular channel heights with 2-mm, 4.5-mm and 7-mm gaps). The results show that detonation can achieve self-sustained propagation with a steady velocity because the conditions are within the detonability in C1–C3 alkanes/oxygen mixtures; the velocity decreases as the detonation transmits into the annular channel due to increased heat and momentum losses from the wall. A modified theoretical model is proposed to predict the detonation velocity deficit for different size channels. Through a comparison with the experimental results, this model was determined to be suitable for predicting the velocity deficit in C1–C3 alkane fuel with oxygen mixtures within reasonable accuracy. Both experimental and theoretical predicted data indicate that velocity deficit is more significant in the smaller channel gap, which verifies that losses are more prominent in the narrower channel. Furthermore, the detonation cellular structure from the smoked foil was measured to analyze the propagation mechanism. The results show detonation has a single-headed spinning structure when detonability is approached. The onset of single-headed spinning detonation of CH4–2O2, C2H6–3.5O2 and C3H8–5O2 in a 36-mm circular tube occurs from p0=3–7 kPa, 4.2–5 kPa and 3.5–3.6 kPa, respectively. This suggests the pressure range of the single-headed spinning phenomenon is narrower for hydrocarbon fuels with more carbon atoms.

Deflagration to detonation transition in JP-10 mist/air mixtures in a large-scale tube

Deflagration to detonation transitions (DDTs) in JP-10 mist/air mixtures have been studied in a horizontal multiphase combustion and explosion tube with inner diameter of 199mm and length of 32.8m. The mist/air mixtures were generated by injecting liquid samples into the experimental tube. Experiments were performed at 298k and 101kPa with equivalence ratio ranged from 0.51 to 2.09. The coupling process of deflagration wave with leading shock wave and low-velocity self-sustained detonation were observed in JP-10 mist/air mixture with a concentration of 142.86g/m3, and the average velocity of the self-sustained detonation wave is 510m/s, which is as low as 26% of C-J value. The low-velocity detonation in JP-10 mist/air mixture can be explained by the low-volatile property of JP-10 liquid and boundary condition. The leanest and richest critical detonable concentrations were studied. The detonation structure was studied by using pressure sensors array mounted in the wave structure test section. A single-head spin detonation wave front was observed and the cellular structure resulting from the spinning movement of the triple point was analyzed.

Experimental investigation of methane-oxygen detonation propagation in tubes

In this study, the detonation behaviors of methane-oxygen with five equivalence ratios (φ=0.5, 0.667, 1, 1.333, 2) were investigated experimentally. Two 32-mm inner diameter round tubes were used, i.e., a smooth tube and a porous tube, to study the effect of different walls on the detonation limits. Fiber optical sensors was employed to capture the signals of the detonation wave, from which the velocity can be determined. Smoked foils were inserted into the smooth to register the cellular structure. The results indicate that in the smooth tube, the detonation propagates at a steady velocity within the limit. The stable spinning detonation is observed in a range of the initial pressure. Below the limits, no steady velocity and cell structure can be observed. In the porous tube, the detonation limits are elevated significantly. Within the limits, the detonation propagates at a velocity more than 0.70VCJ. Below the limits, the decoupled deflagration can hold a steady velocity at about 0.4VCJ∼0.5VCJ. The failure condition for the mixture at φ=0.5 is d/λ≈6. For other mixtures, the detonation fails at d/λ≈4.

Scaling factor in continuous spin detonation of syngas–air mixtures

Multiwave regimes of continuous spin detonation in syngas–air mixtures in a flow-type annular cylindrical combustor 503 mm in diameter are obtained. Experiments are performed for mixtures of carbon oxide and hydrogen with the ratio of the components equal to 1/3, 1/2, or 1/1. The varied parameters are the flow rates of air and syngas, the ratio of these flow rates, and the combustor length. Scalability of the continuous spin detonation process is demonstrated: at identical values of the specific flow rate of air and the combustor expansion ratio, the number of transverse detonation waves increases with increasing combustor diameter. In the examined ranges of combustor lengths and specific flow rates of air, the frequency of these waves is independent of the combustor length, except for narrow regions where the number of waves (and, correspondingly, the flow regime) changes. The structures of transverse detonation waves in regular regimes are almost identical for all examined syngas compositions. It is shown that detonation can be initiated by a jet of combustion products. The minimum diameters of the detonation chamber for different flow rates of the mixture are estimated.

Pressure measurement by fast-response piezo-electric sensors during continuous spin detonation in the combustor

Pressure profiles in a transverse detonation wave propagating in a plane-radial vortex chamber during continuous spin detonation of a mixture consisting of lignite, syngas, and air are measured by specially designed and fabricated high-frequency pressure sensors based on TsTS-19 piezo-ceramics. Pressure levels in the detonation wave front relative to the mean static pressure are determined. It is demonstrated that these levels decrease toward the combustor center (by a factor of 20 and lower) as the wave intensity (velocity) decreases. Pressure oscillations behind the wave front testify to a complex gas-dynamic pattern of the processes in the wave region. A chemical reaction region is detected behind the wave front; its length is approximately 8% of the period between the waves.

Pressure measurement by Fast-Response Piezo-Sensors during Continuous Spin Detonation in the Combustor

Pressure measurement by Fast-Response Piezo-Sensors during Continuous Spin Detonation in the Combustor