Detonation Chamber Research Articles

Numerical modelling of continuous spin detonation in rich methane-oxygen mixture

A numerical simulation of a two-dimensional structure of the detonation wave (DW) in a rich (equivalence ratio φ=1.5) methane-air mixture at normal initial condition has been conducted. The computations have been performed in a wide range of channel heights. From the analysis of the flow structure and the number of primary transverse waves in the channel, the dominant size of the detonation cell for studied mixture has been determined to be 45÷50 cm. Based on the fundamental studies of multi-front (cellular) structure of the classical propagating DW in methane mixtures, numerical simulation of continuous spin detonation (CSD) 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 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 CSD has been determined.

Experimental investigation of an air-breathing pulse detonation turbine prototype engine

This article presents a prototype system of pulse detonation turbine engine which consists of two pulse detonation chambers (PDCs) and a turbocharger. Synchronous and asynchronous ignition methods are investigated with ignition frequency up to 20Hz. Equivalence ratios are controlled around unity. Pressures in the PDCs show different detonation characteristics between these two ignition modes. Pressures upstream of the PDCs are also given. Detailed analyses of these pressure histories show that the two PDCs are coupled and these coupling effects become stronger for asynchronous ignition. Pressure downstream of the compressor is measured and three different compressor pressure ratios are defined according to this pressure. Pressure ratios and rotational speed are given as functions of ignition frequency and air flow rate which also reflect differences between these two ignition modes. Finally, the propulsive performances of the air-breathing pulse detonation prototype engine with synchronous and asynchronous ignition modes are provided. The maximum specific thrust of the system reaches 753Ns/kg which is 27% higher than that of the traditional engine based on ideal Brayton cycle.

Thermobaric effects formed by aluminum foils enveloping cylindrical charges

Conceptually new cylindrical charges enveloped by Al foils have been designed and their thermobaric effects, due to simultaneous fragmentation and combustion of the foils, have been experimentally determined. The fragmentation processes of Al foil was supported by numerical simulations. It has been shown that the quasistatic pressures (QSP) for phlegmatized RDX (RDXph) enveloped with Al-coated plastic foils are higher than that of the pure RDXph, due to combustion of these foil fragments in a thermobaric explosion. The QSP generated by Al–Ni foils enveloping RDXph was found to be much lower than performance of other foils, possibly due to relatively inert nature of Ni. In a small detonation chamber, the charges of RDXph/Al foil (RDXph/Alf) produced even higher experimental maximum peak pressure (Δpmax) than the charges that contained Al powder (Alp). In a closed bunker, the impulse amplitudes of RDXph enveloped by aluminized polyethylene (Al-PE) foils and RDXph enveloped by 100µm Alf (Alf100) charges are much lower than those of the other charges. It was found that the charges enveloped by Al foils have even larger Δpmax than that of RDXph/Alp charges, indicating that the Alf could generate better blast performances than the Alp. The simulations indicate that the observed blast enhancement is dependent not on the thickness, but on the size of surrounding space. The thermobaric fire-ball generated by 40g RDX/Alf charge could sustain combustion up to 40ms, reaching a maximum radius of about 2.4m.

Analysis of influence design parameters ejector pipe at the detonation specifications engine

The engines that use a detonation cycle have greater thermal efficiency than engines with constant-pressure combustion cycle. The mechanisms of ejector augmentation are evident in secondary air entrainment. The impulse characteristics of a pulse detonation engine (PDE) with ejector were investigated under different parameters. The propagation of a detonation wave in an ejector-augmented pulse detonation rocket engine fueled with a hydrogen-oxygen methane-oxygen and hydrocarbon-oxygen mixture is studied. The straight cylindrical ejector was coaxially installed at different axial locations relative to the exit of the detonation chamber. The use of a non-steady ejector is modeled for pulse detonation engine performance improvement. In this paper, a two-dimensional numerical model is developed to help design the basic geometry and operating parameters of the device. The unsteady flow processes are simulated and compared with a baseline PDE without ejector enhancement. Various features including detonation-shock interaction, detonation diffraction and vortex formation are observed. It is observed that the design of detonation wave flow path in detonation tube, ejector and operating parameters such as Mach numbers are mainly responsible for improving the propulsion performance of PDE.Object оf numerical simulation is the cylindrical detonation chamber with a diameter of Dc = 25 mm and a length of Lc = 100 mm. The cylindrical ejectors with a length of Le = 100 mm and diameters De = 35, 40, 45, 50 that 55 mm were attached to the chamber. Also ejectors with a diameter of De = 35 mm and lengths of Le = 50, 100, 150, 200 that a 250 mm respectively were attached to the chamber. The calculation was performed with a computer program that implements a numerical TVD-scheme. The results of calculations were presented as the dependence of specific thrust impulse Isp/Ispo ratio (Isp ­- specific thrust impulse with ejector nozzle; Ispo - specific thrust impulse of a chamber only) to the ejector-to-PDE diameter ratio (De/Dc), to the ejector-to-PDE length ratio (Le/Lc) and to the displacement of an ejector-to-PDE length ratio ((Ld +Lc)/Lc), where Ld – distance from the input section of the nozzle to the thrust wall of a detonation chamber. The method of a numerical simulation proved the possibility of a significant increase of pulse detonation engine performance through the use of ejector nozzle.

Particle temperature measurements in closed chamber detonations using thermoluminescence from Li2B4O7:Ag,Cu, MgB4O7:Dy,Li and CaSO4:Ce,Tb

The present work describes the procedures and results from the first temperature measurements in closed chamber detonations obtained using the thermoluminescence (TL) of particles specifically developed for temperature sensing. Li2B4O7:Ag,Cu (LBO), MgB4O7:Dy,Li (MBO) and CaSO4:Ce,Tb (CSO) were tested separately in a total of 12 independent detonations using a closed detonation chamber at the Naval Surface Warfare Center, Indian Head Explosive Ordnance Disposal Technology Division (NSWC IHEODTD). Detonations were carried out using two different explosives: a high temperature plastic bonded explosive (HPBX) and a low temperature plastic bonded explosive (LPBX). The LPBX and HPBX charges produced temperatures experienced by the TL particles to be between ~550–670K and ~700–780K, respectively, depending on the shot. The measured temperatures were reproducible and typically higher than the thermocouple temperatures. These tests demonstrate the survivability of the TL materials and the ability to obtain temperature estimates in realistic conditions, indicating that TL may represent a reliable way of estimating the temperature experienced by free-flowing particles inside an opaque post-detonation fireball.

Experimental research on rotating detonation in liquid fuel–gaseous air mixtures

This paper describes experimental research into the initiation and propagation of rotating detonation for liquid kerosene and gaseous air mixtures. The research facility with main subsystems is described: fuel and air feeding system, initiation and measurement system. The methods of measurement and calculation of the mass flow rate for each mixture component and methods of calculation of propagation velocity are presented. Pressure inside the detonation chamber was measured by up to three, fast Kistler transducers, which were placed in one line along the chamber or in one plane around the circumference. Propagation of rotating detonation was obtained for a mixture of liquid kerosene and air and a small addition of gaseous hydrogen (below the lean limit). In some experiments, liquid isopropyl nitrate was added to kerosene and its influence to enhance the detonation sensitivity of the kerosene–air mixture was checked. Also a velocity deficit of 20–25% was determined for rotating detonation for the examined heterogeneous mixture.

TURBINE ENGINE WITH DETONATION COMBUSTION CHAMBER IN INSTITUTE OF AVIATION

In Institute of Aviation from 2010 is realized a project POIG 2007-2014 “Turbine engine with detonation chamber.” The main target is to develop a turbine engine using a rotating detonation effect in the process of combustion the fuel. This article presents the most important stages leading to achieve the goals. As a facility test, we have chosen a turbo shaft engine GTD-350 characterized by the location of combustion chamber, which is outside the engine. This feature has helped in modernization the combustion chamber to adjust it to the detonation combustion. Works over the project has been started from the attempts to obtain a rotating detonation in the combustion chamber with a diameter of 500 mm powered by hydrogen. These researches have allowed the team to master the method of detonation initiation and methods for identifying the process of spinning detonation. In the same time works over the kerosene injection on the visualization bench has been begun. On this bench, we have mainly evaluated the extent and location of the fuel stream and the quality of the spray. Simultaneously the program to simulate the injection and the process of spinning detonation in actual geometries of different combustion chambers has been created. The process of initiation the detonation is discussed in the article on the example of detonator using ammo tutorial. Researches about combustion detonation with simultaneously reinforcement the combustion chamber with hydrogen and liquid fuel JET-A1 has also been discussed in this article. Presented research results includes pressure fuel waveforms in supply manifold along with the measurements of combustion pressure correlated with Air-Fuel Equivalence Ratio – lambda. Currently we are working over the integration of the combustion chamber of the engine GTD-350.

Multicriterial choice of the best variant of the pulse detonation engine design for aircraft angular stabilization and orientation systems

The verbal and mathematical formulations of the problem of multicriterion ranging of the pulse detonation engine design variants were carried out. Using the method of morphological box the morphological tablewas composed, on the basis of which many possible design variants of the pulse detonation engines were generated.When compiling the morphological table a conception of pulse detonation engines in the form of the followingsubsystems was considered: detonation chamber, components supply system, initiation system, controlsystem. Eventually as valid options, which were subjected to a study on the firing test bench, we selected twentyvariants. The system of criteria for the assessment of the pulse detonation engines design variants (specificthrust, frontal thrust, specific consumption, unit weight, length) was proposed. Criteria values were determinedduring firing tests. The peculiarities of solving problems by using the methods of "hard" ranging, hierarchiesanalysis, Borda`s method were discovered. The criterion formation of the true Pareto tuples was formulated. Usingthe methods of "hard" ranging, hierarchies analysis, Borda`s method, the criterion of the true Pareto tuplesformation the applied problems of choosing the best pulse detonation engine variant for three important caseswere resolved: - the atmosphere is taken into account, pulse detonation engine suffers the influence of the frontalresistance; - the atmosphere is taken into account, pulse detonation engine is located inside the aircraft and doesnot suffer the immediate impact of the frontal resistance; - the influence of the atmosphere is not taken into account,only pulse detonation engines without ejector are subject to the analysis. The best pulse detonation enginedesign variants for different values of the criteria priorities were revealed.

Detonation engine fed by acetylene–oxygen mixture

The advantages of a constant volume combustion cycle as compared to constant pressure combustion in terms of thermodynamic efficiency has focused the search for advanced propulsion on detonation engines. Detonation of acetylene mixed with oxygen in various proportions is studied using mathematical modeling. Simplified kinetics of acetylene burning includes 11 reactions with 9 components. Deflagration to detonation transition (DDT) is obtained in a cylindrical tube with a section of obstacles modeling a Shchelkin spiral; the DDT takes place in this section for a wide range of initial mixture compositions. A modified ka-omega turbulence model is used to simulate flame acceleration in the Shchelkin spiral section of the system. The results of numerical simulations were compared with experiments, which had been performed in the same size detonation chamber and turbulent spiral ring section, and with theoretical data on the Chapman–Jouguet detonation parameters.

Long-Term, High-Throughput Operation of a Controlled Detonation Chamber Based on Shakedown Under Initial Overload in the Plastic Range

Hydrostatic or pneumatic overpressure testing prior to actual service provides a number of purposes related to structural integrity of pressure vessels, including some degree of confirmation of both the design and fabrication processes. For detonation chambers designed to control impulsive pressure loadings, preservice hydrostatic testing at impulses greater than those expected during normal operation can provide an added benefit—the ability to reduce cyclic fatigue damage caused by long-term, high-throughput operation, where the chamber may be use to control hundreds or even thousands of detonations without compromising structural integrity through excessive fatigue crack initiation and growth. This paper illustrates the favorable characteristics of controlled detonation chamber operation following an initial preservice impulsive over-testing program that demonstrates shakedown and satisfaction of strain ratcheting criteria, leading to favorable cyclic fatigue behavior during subsequent long-term, high-throughput operation.

Influencing Factors on the Performance of Pulse Detonation Engine at Test Bench

Unsteady operation of valveless pulse detonation engine results in unsteady gas dynamics of air inflow. In this paper, a simplified model has been developed to evaluate actual performance of pulse detonation engine with consideration of intake condition. The volume of plenum chamber, inflow area of pulsed detonation chamber and the operation frequency are considered as influencing factors on pulsed detonation chamber thrust performance. The simulation results show bigger plenum chamber volume leads to less inflow perturbation of pulsed detonation chamber. If the gas state of inflow is not determined by unsteady character, the negative thrust of pulsed detonation chamber will decrease with the increase in frequency. But when unsteady character has an effect on inflow, the negative thrust of pulsed detonation chamber increases with the increase in frequency. The experimental results of pulse detonation engine on test bench confirmed the simulation results.

Damage Caused by Dynamic/Cyclic Loading of a Detonation Chamber

The plastic damage caused by multiple dynamic loading and its influence on the ductility and toughness of 3.5% Ni steel (SA203E) and C steel (SA516M) were examined for the discussion of integrity design of detonation chambers. V-notched specimens and hourglass specimens were welded on the 1/7-scale model of a 1-ton explosive class detonation chamber and subjected to 30 detonation shots. It has been indicated that 30 detonation shots caused prestrain in the specimens. The ductility was reduced by the prestrain. The Charpy impact toughness was affected as well in a lower temperature. It has been noted that the damage is developed with fatigue crack growth at the notch root of the V-notched specimen.

Detonation Transition Around Cylindrical Reflector of Pulse Detonation Engine Initiator

To achieve reliable transmission of detonation waves to a pulse detonation engine combustor (detonation chamber), the authors propose a pulse detonation engine initiator that uses a cylindrical reflector downstream of a predetonator exit. The detonation wave propagates around the reflector to change the wave shape in three transition stages: from a planar detonation wave in the predetonator to an expanding cylindrical detonation wave, from the cylindrical wave to a planar toroidal detonation wave, and from the toroidal wave to a planar detonation wave in the detonation chamber. The cylindrical wave propagates along a cylindrical path between the reflector and front wall of the detonation chamber, and the toroidal wave propagates along an annular path between the reflector and sidewall of the detonation chamber. The purpose of this study was to examine the influence of the gap width of the annular path on the transition stages from cylindrical to toroidal and from toroidal to planar. A series of experiments that filled the entire test section with the driver gas mixture (stoichiometric hydrogen–oxygen mixture) showed that the expanding cylindrical detonation wave was sufficiently strong to survive the rarefaction waves from the corners of the reflector at all of the investigated annular gap widths (5, 10, 15, and 20 mm) and was transmitted to the planar toroidal wave successfully in all cases. When the strength of the cylindrical detonation wave was under a supercritical condition for diffraction at the reflector corner, the necessary filling distance for the driver gas was predicted well by the Whitham theory. A second series of experiments showed the influence of the annular gap width on the detonation transition from the planar toroidal detonation wave to the planar detonation wave. Two different types of detonation transitions termed “continuous transition” and “temporal quenching” were observed. The threshold value of for continuous transition is approximately four.

Reactive thrust generated by continuous detonation in the air ejection mode

Processes of continuous spin detonation and pulsed detonation, as well as combustion of a hydrogen-air mixture in an annular combustor 306 mm in diameter in the regime of air ejection are studied experimentally. The specific flow rates of hydrogen are 0.6–9.8 kg/(s ·m2). It is found that the greatest specific impulses of thrust generated by the combustor are reached in the case of continuous spin detonation. On the average, they are greater than the corresponding values by a factor of 1.5 in the case of burning the mixture in streamwise detonation waves, by a factor of 2 in the case of conventional combustion (by a factor of 3 at the maximum thrust impulse of 2200 m/s), and by a factor of 10 in the case of exhaustion of cold hydrogen. A change in the specific flow rate of hydrogen beginning from ≈1.2 kg/(s·m2) corresponding to the maximum thrust impulse decreases its value, and this decrease is more profound as the detonation limits in terms of the specific flow rate of hydrogen are approached. The maximum reactive thrust (83 N) is developed in the examined detonation chamber near the upper limit at the specific flow rate of hydrogen equal to 3 kg/(s·m2).

THREE-DIMENSIONAL NUMERICAL SIMULATIONS OF THE COMBUSTION CHAMBER OF THE ROTATING DETONATION ENGINE

From 2010 Warsaw University of Technology (WUT) and Institute of Aviation (IoA) jointly implement the project under the Innovative Economy Operational Programme entitled ‘Turbine engine with detonation combustion chamber’. The goal of the project is to replace the combustion chamber of turboshaft engine GTD-350 with an annular detonation chamber. During the project, the numerical group that aims to develop computer code allowing researchers to simulate investigated processes has been established. Simulations provide wide range of parameters that are hardly available from experimental results and enable better understanding of investigated processes. Simulations may be also considered as a cheap alternative for experiments, especially when testing geometrical optimizations. In this paper the analysis of simulation results of the combustion chamber of the Rotating Detonation Engine (RDE) investigated at the IoA in Warsaw is presented. Primarily, REFLOPS USG which has become a fundamental numerical tool in the research of the RDE at the IoA is briefly described and governing equations and numerical methods used are shortly presented. Some aspects of numerical simulations of the RDE, related to selection of combustion mechanism, and an initiation of rotating detonation are provided. Secondly, results of simulations of inviscid gas with numerical injectors of hydrogen are compared with available experimental results. Three different wave patterns are identified in numerical solution and briefly described. Results of simulations are compared to experimental results in combustion chamber. Results presented in this paper are part of the project UDA-POIG.01.03.01-14-071 ‘Turbine engine with detonation combustion chamber’ supported by EU and Ministry of Regional Development, Poland.

Propulsive Performance of Ideal Detonation Turbine Based Combined Cycle Engine

A novel two-mode propulsion system based on detonation combustion, known as a detonation turbine based combined cycle engine (DTBCC), was proposed and thermodynamically analyzed for potential application to aircrafts whose flight Mach number is from 0 to 5. The obvious advantage of the two-mode system is that both modes share the same multidetonation chambers. The quasi-stable total temperature and total pressure for inlet conditions of the turbine could be realized in this hybrid pulse detonation engine. A key parameter (drive area ratio) was defined as the ratio of the outflow area at the head to the cross-sectional area of the detonation chamber. The calculated results showed that the increase of the drive area ratio led to the increase in the mass flow entering the turbine; however, this led to the decrease of the total inlet temperature, the total inlet pressure, and the expansion-pressure ratio of the turbine. Compared with an ideal turbojet engine, the inlet temperature of the turbine in a preturbine hybrid pulse detonation engine with a drive area ratio of 1 was 80 K lower than the former under the same pressure ratio and the same fuel-air ratio. In other words, the increase of the drive area ratio may improve the performance of this hybrid pulse detonation engine. Variation of the pressure ratio was adapted to varied flight Mach numbers by a change of the drive area ratio, which induced the enlargement of the operating range. Finally, a performance model was established to research the components’ characteristics and the propulsive performance of the engine. Preliminary performance estimates suggested that thrust and specific fuel consumption of the two-mode propulsion system were superior to the existing turbine based combined cycle designs.

The effect of fuel pretreatment on performance of pulse detonation rocket engines

For hypersonic potential-use pulse detonation rocket engines (PDREs), the detonation chamber must stand against the high intensity of waste heat by fuel active cooling which in turn preheats and promotes liquid hydrocarbon fuel to crack into lower-molecular-weight carbon alkenes. The purpose of this research was to study the beneficial effects of the fuel pretreatments on PDRE performance, which comprised preheating and adding additives. Firstly, five concentric-counter-flow heat exchangers based on active cooling were tested to investigate the effect of geometric dimension on the heating efficiency. The results showed that the optimum length and thickness of annular heat exchange section were 300mm and 5mm, respectively. The heating capacity of the heat exchanger based on active cooling was significant. Furthermore, the effects of heat exchanger on operation time duration of PDRE and atomization improving of liquid kerosene were then investigated. The results indicated that the operation time of PDRE were extended nearly three times and PDRE could be operated normally without fuel injector. The initiation time was a very important factor for the multi-cycle PDRE, which was the sum of ignition delay time and whole deflagration-to-detonation transition (DDT) run-up time; therefore, experiments were conducted to investigate the effects of the fuel preheating and adding additives on the detonation initiation time. The results demonstrated that with the aid of fuel preheating, the detonation initiation time for liquid kerosene was noticeably reduced and the operation time of PDRE was remarkably prolonged, a fully-developed detonation wave was achieved in the position away from igniter 8.33 times of the diameter of the detonation tube. By adding the additives to liquid kerosene, the detonation initiation time from 0.75ms decreased to 0.34ms and the detonability of fuel was dramatically improved.

Experimental Research on Induction Systems of an Air-breathing Valveless Pulse Detonation Engine

An air-breathing valveless PDE model was designed and manufactured, which was made up of subsonic inlet, mixing chamber, ignition chamber, detonation chamber. The total pressure recovery coefficient, flux coefficient and intake resistance with six different induction systems were measured by a semi free subsonic flow field. The proof-of-principle experiments of PDE model with different induction systems were all successfully carried out, by using liquid gasoline-air mixture with low-energy system (total stored energy less than 50 mJ). The measured detonation wave pressure ratio was very close to that of C-J detonation. The air-breathing PDE model was easy to initiate and worked in good condition. The deflagration to detonation transition (DDT) and operation frequency effect on pressure traces were also investigated by experiments. The results indicated the oscillation of pressure peak at P6 enhanced with the operation frequency increased. DDT accomplished before P6 and the DDT distance was about 0.9 m (from the ignitor).

Analysis of the Dynamic Response of a Controlled Detonation Chamber

Detonation chambers (either mobile or fixed) are used worldwide for a wide range of applications. At present, a 1/7 scale model of a 1 ton detonation chamber is available for extended testing in Belgium. The chamber is a single wall cylindrical vessel with semielliptical ends. Each time an explosive charge is fired in the vessel, that vessel is submitted to a number of deformation cycles. A series of strain gauges measures the deformation of the vessel walls. Experimental peak strains and vibration frequency can be compared with predicted values based on simple formulas. Measured values are reasonably close to the estimated values. The influence of the shape of the charge is studied. The shape has an important influence on the chamber response. For a fixed charge mass, a spherical charge causes less deformation than a cylindrical charge and is therefore advantageous from a fatigue point of view.

Driver Gas Reduction Effect of Pulse-Detonation-Engine Initiator Using Reflecting Board

To reduce driver gas usage of a pulse detonation engine operating in airbreathing mode, the authors experimentally examined a combination method of a reflecting board and overfilling of the driver gas. This method has the potential to reduce the predetonator diameter by half and shorten the overfilling distance h to the reflecting board position w. Experiments with stoichiometric hydrogen–oxygen and hydrogen–air mixtures as driver and target gases, respectively, showed that the overfilling distance necessary to have a planar detonation wave propagate in a detonation chamber is reduced to 30 mm when a reflecting board is used with a reflecting board clearance of w 10 mm. With an overfilling distance of 30 mm, the transformation of the detonation wave from cylindrical to toroidal did not occur because of the mixing effect of the driver gas and the target gas around the reflecting board. A 100-mm-thick reflecting board prevents the mixing effect, and a successful transformation from cylindrical to toroidal becomes possible with an overfilling distance as small as 17.2 mm.