Detonation Chamber Research Articles

Numerical study on detonation initiation process in a reverse ignition boosted detonation chamber

Numerical study on detonation initiation process in a reverse ignition boosted detonation chamber

Analysis of coupling supersonic turbine stage with rotating detonation combustor under different turbine parameters

The rotating detonation gas turbine boasts several advantageous characteristics, including self-pressurization, minimal entropy increase, high thermal efficiency, and a high thrust-to-weight ratio. These features make it a promising candidate for the next generation of aerospace power devices. This study investigates the flow characteristics and performance attributes of the supersonic turbine stage coupled with a rotating detonation chamber based on different rotational speeds, blade ratio of rotor and stator, and hub radius, and uses DMD (Dynamic Mode Decomposition) to analyze the main modes of the supersonic turbine. The research identifies distinct wave modes in both the stator and rotor blades of the supersonic turbine. In the stator blades, the modes include waveless contact modes, opposite side λ-wave oblique shock wave modes, and derived modes from opposite side λ-wave oblique shock waves. In the rotor blades, the modes encompass non-separation modes (waveless modes, asymmetric dual λ-wave modes, oblique cut wave modes, and single-side λ-wave modes on the pressure surface), leading-edge stator excitation single separation bubble modes, saddle-type separation modes, and dual separation bubble modes. The efficiency and power of the supersonic turbine stage increase with the rotational speed. The turbine efficiency is highest when the blade ratio is 10:7. Under multi-wave mode conditions, detonation waves demonstrate adaptive self-regulation abilities, ultimately achieving equilibrium in speed, detonation wave height, and spacing. The dominant modes in the stator blades and combustion chamber are governed by detonation waves and slip lines, while in rotor blades, the primary mode is the flow-directional vortex mode governed by detonation waves and slip lines at a frequency lower than their propagation frequency. This research holds certain reference significance for understanding the internal flow characteristics of rotating detonation gas turbines, as well as discussing the patterns of efficiency, power, and load characteristics, thereby offering valuable insights for the practical application of rotating detonation gas turbines.

Influence of inhomogeneous distribution of inflow equivalence ratio on oblique detonation morphology and characteristic

In this paper, numerical simulations using Euler equations coupled detailed chemical reaction model are performed to reveal the influence of inhomogeneous distribution of inflow equivalence ratio (ER) on the morphology and characteristic of oblique detonation in hydrogen/oxygen/argon mixtures. The purpose of this study is to better understand the key parameters’ variation law of oblique detonation flow field under practical flight conditions so as to guide the design of oblique detonation chamber. Within the scope of our simulations, the results show that the oblique detonation wave (ODW) can still be standing under a large ER gradient. The thermodynamic state and characteristic sizes of the flow field reach the maximum value around ER = 0.8. First, the ODW angle and the post-wave temperature/pressure increase with the homogeneous inflow ER. Then, the inhomogeneity of inflow ER is introduced by assuming a lateral linear distribution covering the whole inflow boundary. When the ER increases along the inflow boundary with ER = 0 at the wedge tip, the overall morphology of the ODW presents a concave structure. Inversely, the ODW is convex with ER = 0 at the top outlet. The morphology and characteristic sizes of ODW are determined by the mixture composition in front of the corresponding wave surface. The transition mode of ODW is mainly determined by the ER of the incoming flow in front of the induction region.

Effect of ethylene-rich gas temperature on rotating detonation auto-initiation process

In this study, the propagation characteristics of a rotating detonation wave (RDW) between ethylene-rich gas and ambient air were investigated experimentally. The traditional pre-detonator initiation method was abandoned in the experiment, but the spontaneous combustion of high-temperature ethylene-rich gas and air was adopted. The RDW auto-initiated through the deflagration-to-detonation transformation (DDT) process. With an increase in the ethylene-rich gas temperature, the modes of RDW propagation appeared as delayed initiation, dual-wave collision, and fluctuating dual-wave collision modes. When the gas temperature was too high, a secondary detonation wave was produced near the head of the rotating detonation chamber (RDC), which affected the propagation efficiency and stability of the RDW. The increase in gas temperature expanded the equivalence ratio range of auto-initiation, which was due to the higher gas temperature, and more highly active components were precipitated.

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.

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.

One-step synthesis and characterization of Y2O3 nanoparticles via emulsion detonation method

Yttrium oxide (Y2O3) nanoparticles have critical applications in many industries, including ceramics, optics, and biomedicine. However, conventional synthesis methods are typically cumbersome and time-consuming. Herein, a novel emulsion detonation method successfully achieved the one-step synthesis of Y2O3 nanoparticles. In this method, yttrium nitrate hexahydrate was uniformly dispersed in the emulsion explosive as a precursor and an auxiliary oxidizer. After the emulsion explosive was detonated in a detonation chamber, the detonation products were collected, purified and characterized by X-ray diffraction, Fourier transform infrared spectrometer, Raman spectrometer, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, field emission transmission electron microscopy, and ultraviolet spectrophotometer. The results show that the as-synthesized powders are high-purity cubic phase yttrium oxide nanoparticles with a spherical-like morphology and an average particle size of approximately 30 nm. These Y2O3 nanoparticles have a wide (5.53 eV) energy band gap, close to the conventional methods. Based on detonation theory, thermochemical theory, and characterization results, this text discussed the mechanism of the Y2O3 nanoparticles synthesized by the emulsion detonation method. During detonation, the formation of the Y2O3 nanoparticles underwent three stages: the formation of the Y2O3 molecules by the collision of Y and O ions, the formation of the crystal nucleus at supersaturation concentration, and crystal growth. This study provides a novel, cost-effective method for efficiently synthesizing Y2O3 nanoparticles.

Influence of high-pressure intermittent fuel supply mode on operation characteristics of pulse detonation combustor

In order to reduce the atomization particle size in a liquid fueled pulse detonation combustor (PDC), a high-pressure intermittent fuel supply system was designed and tested with a U-shaped PDC (U-PDC). Influence of high-pressure intermittent fuel supply mode on the initiation characteristics of the U-PDC was experimentally investigated. Gasoline\\air was used as fuel and oxidant in the test, the atomization particle size of high-pressure direct injector was obtained and the detonation characteristics of U-PDC were analyzed. The results show that the particle size of a single direct spray is 10 μm to 30 μm, and the atomization particle size of the three direct injector combination is about 20 μm to 55 μm under simulated operating conditions. Smaller atomization particle size is conducive to fuel evaporation and participation in combustion The high-pressure intermittent fuel supply mode can realize stable operating with the U-PDC from 10 Hz–30 Hz, and reduce the influence of the periodic pressure pulsation in the detonation chamber on the fuel supply stability. The detonation wave velocity increases with the increased frequency, and the DDT distance is shortened from 733 mm to 616 mm. This laid the foundation for subsequent high-pressure intermittent fuel supply technology in PDC.

Numerical study on the flow characteristics and stability in the isolator of rotating detonation ramjet engine by different combustion modes and structure parameters

In this paper, numerical simulations are conducted to investigate the effects of the combustion modes and structure parameters of the combustion chamber of a rotating detonation ramjet engine(RDRE) generated within the isolator. The stability of the isolator in the combustion mode as a single or dual wave mode is evaluated. The influence of parameters such as the combustion chamber expansion angle and the outside diameter of combustion chamber is also taken into account. The results show that the propagation of the detonation wave in the combustion chamber in a dual-wave (DW) mode reduces the instability generated by the combustion chamber on the isolator. In the stability model, the fluctuation range of the single-wave (SW) mode accounts for 14.43 % of the total length of the isolator, while it is 4.67 % in the DW mode, which is reduced by 10.97 %. The DW mode is more capable of withstanding changes in the combustion state of the detonation chamber. In the SW mode, the back propagation pressure wave (BPPW) propagates to the inlet of the isolator, while the fluctuation range of the isolator in the DW mode only increases by 29.68 % and still maintains a stable working condition. Changing the length of the isolator and outer diameter of the combustion chamber, the DW mode can also accommodate changes in the combustion chamber structure without affecting the inlet flow status of the isolator.

NOx formation processes in rotating detonation engines

High-fidelity simulations of RDEs with H2-Air-NOx chemistry are employed to study NOx emissions in such devices. Discrete injection of gaseous hydrogen fuel and continuous injection of air oxidizer is used at various mass flow rate conditions in several 3D RDE simulations to understand resulting NOx production behaviors. Simulations are also performed for two different injector configurations, one in which air is injected axially into the detonation chamber [Axial Air Inlet (AAI)] and one in which air is injected radially [Radial Air Inlet (RAI)]. It is seen that the AAI RDE produces much less NOx than the RAI RDE, mainly due to the weaker waves seen in this system as a result of parasitic combustion losses from product gas recirculation. Parasitic combustion does lead to NOx formation in its own right, but the emissions levels from this process are negligible compared to emissions stemming directly from detonation processes. In regards to detonation strength in particular, it is generally seen that detonation strength increases with increasing mass flow rate, in turn increasing peak pressure, peak heat release and NOx emissions levels. Nevertheless, even the highest recorded NOx levels at the combustor exit in this study remain on the same order of magnitude as compared to gas turbine exhaust emissions levels, supporting the claim that significant differences between detonative and deflagrative combustion do not necessarily lead to significant differences in NOx levels. Overall, this study provides greater understanding into the behaviors of NOx formation in RDEs and how these behaviors are affected by changes in operating parameters.

Effect of equivalence ratio on rotating detonation combustion with n-heptane sprays

Three-dimensional simulations are conducted for rotating detonative combustion fueled by n-heptane sprays without any fuel pre-vaporization. Parametric studies are performed to study the influences of equivalence ratio on the rotating detonation wave. The decoupled process of the detonation wave with lean equivalence ratio is also been analyzed. It is found that when the global equivalence ratio is lower than 0.6, a stable propagating detonation wave cannot be observed in the combustion chamber. With the gradual increase of the global equivalence ratio, the detonation wave can stably propagate in the combustion chamber after ignition. When the global equivalence ratio is 0.8–1.5, the propagation mode of the detonation wave in the combustion chamber is one-way propagation mode. When the global equivalence ratio gradually increase from 0.8 to 1.5, the formation time of the detonation wave first decreases and then increases with the increase of the equivalence ratio. Besides, the stability of the detonation wave first increases and then decreases with the increase of the equivalence ratio. Moreover, the thrust of the rotating detonation chamber fueled by n-heptane increases gradually with the increase of the equivalence ratio. The specific impulse of the combustion chamber first increases and then decreases with the increase of the equivalence ratio.

Evolution of the cellular structure of detonation waves under the condition of non-uniform initiation

At present, detonation principles are widely used for propulsion purposes. Stable initiation of detonation and its sustainable propagation are the key factors for safe operation of detonation chambers. In this paper, the evolution of the cellular structure of detonation waves under the condition of non-uniform initiation is investigated within the frames of two-dimensional simulations in a stoichiometric mixture of hydrogen with air. The dependence on cellular structure on the heterogeneity of initiation sources, chemical kinetic mechanism is studied. The simulation results are compared with experimental data. It is demonstrated, that in case of detonation decay after switching off initiators the flow structure essentially depends on heterogeneity of initiator, while in achieving the self-sustaining propagation mode the wave structure becomes independent on initiation conditions and “forgets” initial heterogeneity.

Study on initiation characteristics of rotating detonation by auto-initiation and pre-detonation method with high-temperature hydrogen gas

Experimental studies were conducted on the initiation characteristics of rotating detonation waves (RDW) using auto-initiation and pre-detonation methods with high-temperature hydrogen gas. The effects of the two initiation methods on the formation and propagation characteristics of rotating detonation waves were compared. The experimental results showed that the formation process of the RDW was different when using auto-initiation and pre-detonation initiation. However, the parameters of the stable propagation stage of the RDW were similar. The time required for the formation of the RDW by pre-detonation was relatively short. As the equivalence ratio increased, the rotating detonation chamber (RDC) exhibited five propagation modes: two-co rotating detonation waves (TRDW), two-counter rotating detonation waves (TCRDW), a mixed mode, intermittent single rotating detonation wave (ISRDW), and single rotating detonation wave (SRDW). It is worth noting that both initiation methods were capable of achieving rotating detonation within the equivalence ratio range of 0.68–1.96. The pre-detonation initiation can expand the range of stable SRDW modes and has some advantages in terms of RDW propagation stability.

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

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

Effects of blockage ratio on the propagation characteristics of hydrogen-rich gas rotating detonation

The propagation characteristics of a hydrogen-rich gas/air rotating detonation wave (RDW) were investigated for different blockage ratios (BRs). Two rotating detonation chamber (RDC) widths were used in combination with different RDC exit widths to obtain different RDC BRs. The variations in the RDW propagation modes and wave velocities at different BRs and equivalence ratios (ERs) were studied and analyzed. The experimental results show that four types of RDW propagation modes can be obtained (single wave, single wave/counter-double waves hybrid mode, triple waves, and unstable triple waves) by changing the BRs and ERs. For BR > 0.64, the RDW exhibits a triple waves mode. The RDC width also affects the RDW propagation mode. The results show that at low BRs, the change in the RDW propagation mode owing to the injection pressure difference is the main influence mechanism. As the BR increases, the influence of the reflected shock wave from the exit of the RDC increases, which plays an important role in the generation of the triple waves mode. The stability of RDW propagation can be improved by appropriately increasing the blockage ratio in the RDC. The 26 mm RDC width at BR = 0 results in a maximum wave velocity of 1933.8 m/s. Moreover, the stability of the RDW propagation is poor at low and high BRs.

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

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

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

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

Numerical and boundary condition effects on the prediction of detonation engine behavior using detailed numerical simulations

High-fidelity numerical simulations of an experimental rotating detonation engine with discrete fuel/air injection were conducted. A series of configurations with different feed-plenum pressures but with constant equivalence ratio were studied. Detailed chemical kinetics for the hydrogen/air system is used. A resolution study for the full rotating detonation engine (RDE) system simulation is also conducted. Two kinds of boundary conditions, a total pressure boundary and a constant mass flow rate boundary, are used to assess the effects of the inlet boundary. As mass flow rate is increased, the total pressure boundary causes more error in the axial pressure distribution while the constant mass flow rate gives a better solution for all cases ran. The simulations confirm experimental findings, and reproduce qualitative as well as some of the quantitative trends. These results demonstrate that a) fuel-air mixing is highly non-uniform within the detonation chamber, leading to variations in local equivalence ratio, b) the fuel and oxidizer injectors experience significant backflow as the detonation wave passes over, but recover at different rates which further augments the inefficiencies in mixing, and c) parasitic combustion in the mixing region makes the detonation wave weak by extending the reaction zone across the wave.

Experimental study on the auto-initiation of rotating detonation with high-temperature hydrogen-rich gas

An experimental study on the auto-initiation process of rotating detonation waves (RDWs) was conducted with high-temperature hydrogen-rich gas as the fuel and air as the oxidant. Spontaneous combustion of high-temperature hydrogen-rich gas and air occurred after they were injected into a rotating detonation chamber (RDC), which resulted in hot spots in the RDC and induced the formation of a rotating deflagration flame. Then, an RDW formed through the deflagration-to-detonation transition process in the RDC. The auto-initiation process of high-temperature hydrogen-rich gas and the formation mechanism of RDWs were studied in detail through experiments. The influences of the equivalence ratio on the RDW propagation characteristics of high-temperature hydrogen-rich gas were analyzed. The results showed that with the increase in the equivalence ratio from 0.61 to 1.93, five RDW propagation modes appeared in the RDC: Failure, two counter rotating detonation wave (TCRDW), Mixed, intermittent single rotating demodulation wave, and single rotating detonation wave (SRDW) modes. The Mixed mode was the transition mode from the TCRDW mode to the SRDW mode. The highest RDW velocity was 1485.9 m/s when the equivalence ratio was 1.32, in which the propagation mode was the stable SRDW mode.

Investigation on propagation characteristics and performances of RDE fueled by kerosene under low oxygen mass fraction

The application of rotating detonation chambers instead of traditional afterburners is expected to improve the overall performance of turbine engines. Based on the background, the effects of oxygen mass fractions, inlet temperatures, equivalent ratios and nozzle outlet areas on the propagation characteristics and performances of RDE under low oxygen mass fractions and lean fuel conditions are investigated. It is observed that increasing the inlet temperature can widen the lower boundary of the oxygen mass fraction maintaining the propagation of RDWs, but decrease the propagation stability of the detonation waves. Although increasing the equivalent ratio has little effect on the lower boundary of the oxygen mass fraction, the propagation stability of the detonation wave is enhanced. It is found that reducing the nozzle outlet area ratio can effectively broaden the lower boundary of the oxygen mass fraction. With the decrease of oxygen mass fraction, the total pressure gain and combustion efficiency show a decreasing trend. Reducing the inlet air temperature, increasing equivalent ratios and reducing the nozzle outlet area ratio are conducive to reducing the inlet pressure ratio, which in turn reduces the inlet air loss and improves the total pressure gain. Combustion efficiency is higher under conditions of high oxygen mass fractions, low inlet temperatures, low equivalent ratios and small outlet area ratios.