The Experts below are selected from a list of 528 Experts worldwide ranked by ideXlab platform
Ronald K Hanson - One of the best experts on this subject based on the ideXlab platform.
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single cycle unsteady nozzle phenomena in Pulse Detonation Engines
Journal of Propulsion and Power, 2007Co-Authors: Z C Owens, Ronald K HansonAbstract:10.2514/1.22415 A quasi-one-dimensional, Euler model with detailed finite-rate chemistry is used to conduct a parametric assessment of nozzle area ratio effects on the single-cycle performance of a Pulse Detonation engine. Using results from the parametric study, design criteria are suggested for evaluating optimal contraction and expansion nozzle area ratios. In particular, the optimal expansion area ratio is shown to be well-predicted by using isentropic theory and the time-averaged, head wall pressure as the stagnation condition. To validate the parametric analysis, three nozzle sections are fabricated and tested in a single-cycle Pulse Detonation engine facility. Time-resolved thrust and specific imPulse (I SP ) measurements are made for each nozzle and compared to simulated results. Additionally, schlieren imaging is used to investigate the blowdown gasdynamics in each of the three nozzles. Comparisons between simulated and measured imPulse data are addressed using insights gathered from the flow visualization. Resulting analysis indicates that multidimensional wave phenomena are important in nozzles with converging sections. Overprediction of I SP by the model is attributed to deficiencies in accurately capturing the plateau pressure (P 3 ), as well as the inability to model the experimentally observed deflagration-to-Detonation transition process. The relative contribution of each of these effects is quantified. Experimental measurements validate trends observed in the parametric study and reveal that an appropriately optimized diverging nozzle produces the largest single-cycle Isp.
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Diode Laser Sensors for Ground Testing
2006Co-Authors: Ronald K Hanson, Jay B JeffriesAbstract:Tunable diode laser (TDL) absorption has proven highly effective for time-resolved in situ sensing of gaseous flows, and as a result such sensors are utilized increasingly in the development and control of advanced propulsion and combustion systems. Sensors using TDL absorption along a line-of-sight have the capability of fast or even continuous measurements of multiple flowfield quantities. Recent advances in TDL absorption-based sensors suggest excellent potential for development into routine diagnostic tools for a wide variety of ground-test applications. From research in our laboratory we select three aspects: (1) the development of wavelength-multiplexed absorption concepts, allowing multiple measurements along each line-of-sight; (2) ground-test applications of TDL absorption to Pulse Detonation Engines, gas turbine sector rigs, and scramjet combustor research; and (3) extension of wavelength-multiplexed TDL sensing to hydrocarbon fuels using new wavelength-tunable mid-IR lasers. Nomenclature Tν = fractional transmission at frequency ν ν = frequency in cm-1 I = Intensity S = absorption linestrength φ = absorption lineshape Pi = partial pressure of molecular species i αν = spectral absorbance defined as the product SφPiL kν = spectral absorption coefficient L = optical path length T = gas temperature I
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monitoring and control of a Pulse Detonation engine using a diode laser fuel concentration and temperature sensor
Proceedings of the Combustion Institute, 2002Co-Authors: Scott T Sanders, Jay B Jeffries, Ronald K HansonAbstract:Fuel measurements are needed to accurately tailor fued charges in Pulse Detonation Engines (PDEs) to improve engine performance and to validate PDE models and computations. Here, we report simultaneous concentration and temperature measurements of C 2 H 4 fuel in a PDE using a newly developed diode-laser absorption sensor. These measurements enable characterization of the fuel loading and ignition timing of the engine. Based on these characterizations, a real-time control system that optimizes fuel consumption and maximizes specific imPulse in the engine has been realized. Similar measurements of C 2 H 4 concentration and temperature were used to characterize Pulse-to-Pulse interference resulting from loading fresh fuel/oxygen reactants into hot combustion products. The sensor was used in a simple control scheme to minimize such interference, illustrating its potential role in control systems to maximize the engine's operation rate. During these studies, the sensor demonstrated two valuable improvements over traditional absorption spectroscopic techniques: (1) increased robustness and accuracy and (2) simultaneous measurements of concentration and temperature. These improvements are enbled by broad wavelength scanning of the Q-branch spectra of C 2 H 4 near 1.62 μm. The success achieved in these small-scale tests provides strong support for expanded use of diode-laser sensors in propulsion applications.
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diode laser sensor for monitoring multiple combustion parameters in Pulse Detonation Engines
Proceedings of the Combustion Institute, 2000Co-Authors: Scott T Sanders, Jeffrey A Baldwin, Thomas P Jenkins, Douglas S Baer, Ronald K HansonAbstract:Diode-laser absorption spectroscopy techniques have been adapted and, applied for in situ measurements of pertinent combustion parameters in Pulse Detonation Engines (PDEs). A sensor employing five multiplexed diode lasers operating in the 1300–1800 nm spectral region has been developed for monitoring gas temperature, H2O concentration, liquid fuel concentration, and soot volume fraction. Gas temperature is determined from the ratio of H2O absorbances at different wavelengths: water mole fraction and fuel and soot volume fractions are determined from the measured gas temperature and absorbances at selected wavelengths. The sensor's time response (0.5 μs) and non-intrusive, nature make it suitable for measurements in the hostile environment generated by PDEs. The sensor was used to monitor a 4 cm diameter PDE operating on a JP-10/oxygen aerosol. Measurements revealed charges of non-uniform equivalence ratio at ignition. Detonations processing such charges reached 95% of the Chapman-Jouget velocity and gas pressures predicted for a stoichiometric, uniform load. Gas temperature and H2O concentration, however, reached only ≈50% of the Chapman-Jouget predictions, as a result of the decreasing fuel concentration along the length of the engine. The sensor also revealed the presence of hot H2O for a long duration (>100 ms) relative to the duration of the pressure Pulse (≈500 μs) in the blowdown following the Detonation. The engine performance information recorded by the sensor is expected to enhance PDE modeling and optimization efforts, potentially enabling PDE combustion control.
Shepherd J. E. - One of the best experts on this subject based on the ideXlab platform.
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Toroidal Imploding Detonation Wave Initiator for Pulse Detonation Engines
'American Institute of Aeronautics and Astronautics (AIAA)', 2007Co-Authors: Jackson S., Shepherd J. E.Abstract:Imploding toroidal Detonation waves were used to initiate Detonations in propane–air and ethylene–air mixtures inside of a tube. The imploding wave was generated by an initiator consisting of an array of channels filled with acetylene–oxygen gas and ignited with a single spark. The initiator was designed as a low-drag initiator tube for use with Pulse Detonation Engines. To detonate hydrocarbon–air mixtures, the initiator was overfilled so that some acetylene oxygen spilled into the tube. The overfill amount required to detonate propane air was less than 2% of the volume of the 1-m-long, 76-mm-diam tube. The energy necessary to create an implosion strong enough to detonate propane–air mixtures was estimated to be 13% more than that used by a typical initiator tube, although the initiator was also estimated to use less oxygen. Images and pressure traces show a regular, repeatable imploding wave that generates focal pressures in excess of 6 times the Chapman–Jouguet pressure.Atheoretical analysis of the imploding toroidal wave performed using Whitham’s method was found to agree well with experimental data and showed that, unlike imploding cylindrical and spherical geometries, imploding toroids initially experience a period of diffraction before wave focusing occurs. A nonreacting numerical simulation was used to assist in the interpretation of the experimental data
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Model for the Performance of Airbreathing Pulse-Detonation Engines
'American Institute of Aeronautics and Astronautics (AIAA)', 2006Co-Authors: Wintenberger E., Shepherd J. E.Abstract:A simplified flowpath analysis of a single-tube airbreathing Pulse Detonation engine is described. The configuration consists of a steady supersonic inlet, a large plenum, a valve, and a straight Detonation tube (no exit nozzle). The interaction of the filling process with the Detonation is studied, and it is shown how the flow in the plenum is coupled with the flow in the Detonation tube. This coupling results in total pressure losses and pressure oscillations in the plenum caused by the unsteadiness of the flow. Moreover, the filling process generates a moving flow into which the Detonation has to initiate and propagate. An analytical model is developed for predicting the flow and estimating performance based on an open-system control volume analysis and gasdynamics. The existing single-cycle imPulse model is extended to include the effect of filling velocity on Detonation tube imPulse. Based on this, the engine thrust is found to be the sum of the contributions of Detonation tube imPulse, momentum, and pressure terms. Performance calculations for Pulse Detonation Engines operating with stoichiometric hydrogen–air and JP10–air are presented and compared to the performance of the ideal ramjet over a range of Mach numbers
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Thermodynamic Cycle Analysis for Propagating Detonations
'American Institute of Aeronautics and Astronautics (AIAA)', 2006Co-Authors: Wintenberger E., Shepherd J. E.Abstract:Propagating Detonations have recently been the focus of extensive work based on their use in Pulse Detonation Engines [1]. The entropy minimum associated with Chapman–Jouguet (CJ) Detonations [2] and its potential implications on the thermal efficiency of these systems [3] has been one of the main motivations for these efforts. The notion of applying thermodynamic cycles to Detonation was considered first by Zel’dovich [4], who concluded that the efficiency of the Detonation cycle is slightly larger than that of a cycle using constant-volume combustion. More recently, Heiser and Pratt [3] conducted a thermodynamic analysis of the Detonation cycle for a perfect gas using a one-γ model of Detonations. Other studies have used constant-volume combustion as a surrogate for the Detonation process [5]. This work presents two main contributions. First, we present an alternative physical model for the Detonation cycle handling propagating Detonations in a purely thermodynamic fashion. The Fickett–Jacobs (FJ) cycle is a conceptual thermodynamic cycle that can be used to compute an upper bound to the amount of mechanical work that can be obtained from detonating a given mass of explosive. Second, we present computations of the cycle thermal efficiency for a number of fuel-oxygen and fuel-air mixtures using equilibrium chemistry, and we discuss the strong influence of dissociation reactions on the results
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Introduction to "To the Question of Energy Use of Detonation Combustion" by Ya. B. Zel'dovich
'American Institute of Aeronautics and Astronautics (AIAA)', 2006Co-Authors: Wintenberger E., Shepherd J. E.Abstract:Ya. B. Zel’dovich (1914–1987) made numerous contributions [1] to the theory of Detonation, beginning with his very well known and widely translated article [2] on Detonation structure that first introduced the standard Zel’dovich-von Neumann-Döring (ZND) model of shock-induced combustion. Even at that early stage of Detonation research, Zel’dovich was also considering the application of Detonations to propulsion and power engineering. He published these ideas in another paper [3] that has been virtually unknown in the West and has apparently remained untranslated until now. We are indebted to Sergey Frolov of the N.N. Semenov Institute of Chemical Physics for first bringing this article to our attention. We believe that the focus of this paper, which is the application of Detonation waves to power generation and propulsion, is very relevant to the current activity on Pulse Detonation Engines. In particular, Zel’dovich was apparently the first researcher to consider the questions of the relative efficiency of various combustion modes, the role of entropy production in jet propulsion, and the distinction between unsteady and steady modes of Detonation in power engineering and propulsion applications. Even 60 years later, we believe that his results are relevant and can be of value in modern discussions on thermodynamic cycle analysis of Detonation waves for propulsion [4]. For these reasons, we have arranged for the paper to be translated and suggested that it be published by the Journal of Propulsion and Power
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Thermal and Catalytic Cracking of JP-10 for Pulse Detonation Engine Applications
'California Institute of Technology Library', 2002Co-Authors: Cooper M., Shepherd J. E.Abstract:Practical air-breathing Pulse Detonation Engines (PDE) will be based on storable liquid hydrocarbon fuels such as JP-10 or Jet A. However, such fuels are not optimal for PDE operation due to the high energy input required for direct initiation of a Detonation and the long deflagration-to-Detonation transition times associated with low-energy initiators. These effects increase cycle time and reduce time-averaged thrust, resulting in a significant loss of performance. In an effort to utilize such conventional liquid fuels and still maintain the performance of the lighter and more sensitive hydrocarbon fuels, various fuel modification schemes such as thermal and catalytic cracking have been investigated. We have examined the decomposition of JP-10 through thermal and catalytic cracking mechanisms at elevated temperatures using a bench-top reactor system. The system has the capability to vaporize liquid fuel at precise flowrates while maintaining the flow path at elevated temperatures and pressures for extended periods of time. The catalytic cracking tests were completed utilizing common industrial zeolite catalysts installed in the reactor. A gas chromatograph with a capillary column and flame ionization detector, connected to the reactor output, is used to speciate the reaction products. The conversion rate and product compositions were determined as functions of the fuel metering rate, reactor temperature, system backpressure, and zeolite type. An additional study was carried out to evaluate the feasibility of using pre-mixed rich combustion to partially oxidize JP-10. A mixture of partially oxidized products was initially obtained by rich combustion in JP-10 and air mixtures for equivalence ratios between 1 and 5. Following the first burn, air was added to the products, creating an equivalent stoichiometric mixture. A second burn was then carried out. Pressure histories and schlieren video images were recorded for both burns. The results were analyzed by comparing the peak and final pressures to idealized thermodynamic predictions
Kailas Kailasanath - One of the best experts on this subject based on the ideXlab platform.
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effect of inlet on fill region and performance of rotating Detonation Engines
47th AIAA ASME SAE ASEE Joint Propulsion Conference & Exhibit, 2011Co-Authors: Douglas Schwer, Kailas KailasanathAbstract:Rotating Detonation Engines (RDE’s) represent an alternative to the extensively studied Pulse Detonation Engines (PDE’s) for obtaining propulsion from the high efficiency Detonation cycle. Unlike the PDE, RDE’s require fuel and oxidizer under high pressure to be injected through micro-nozzles from mixture plenums. This injection process is critically important to the stability and performance of the RDE. In previous papers, this injection process has been idealized as a mass addition source term at the injection wall. This has allowed us to do a variety of parametric studies on the effect of plenum pressure, back pressure, and engine geometric parameters. Due to the importance of the injection process, it is important to more closely focus on different approximations to this process; from idealized representations of the micro-nozzles to actually modeling individual micro-injectors. The results show that the RDE simulation is very sensitive to how these injectors are modeled; however, the more stable ideal injection approximation still provides valuable information on the influence of different parameters on overall performance. Values for specific imPulse vary from 5331 s to 4918 s.
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numerical study of the effects of engine size on rotating Detonation Engines
49th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2011Co-Authors: Douglas Schwer, Kailas KailasanathAbstract:Rotating Detonation Engines (RDE’s) represent an alternative to the extensively studied Pulse Detonation Engines (PDE’s) for obtaining propulsion from the high efficiency Detonation cycle. Since it has received considerably less attention, the general flow-field and effect of parameters such as stagnation conditions, combustion chamber sizing, and fuel mixture on specific imPulse are less well understood than for PDE’s. In this paper we use a model developed previously for doing time-accurate calculations of RDE’s in two and three dimensions to examine the effect of different engine sizing parameters on mass flow rate, performance, and thrust. Specific sizing parameters that are discussed are area ratio of micro-injectors to head-end wall, combustion chamber diameter and length. Additionally, several three-dimensional simulations for small combustion chambers with different thicknesses are shown. Results indicate that for many of these parameters, the characteristics of the engine scale in predictable ways for high plenum pressures. At lower plenum pressures, the results are more difficult to interpret. Specific imPulses varied from 3300 s (low-pressure, large chamber length) to 5500 s.
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numerical investigation of the physics of rotating Detonation Engines
Proceedings of the Combustion Institute, 2011Co-Authors: Douglas Schwer, Kailas KailasanathAbstract:Abstract Rotating-Detonation-Engines (RDE’s) represent an alternative to the extensively studied Pulse-Detonation-Engines (PDE’s) for obtaining propulsion from the high efficiency Detonation cycle. Since it has received considerably less attention, the general flow-field and effect of parameters such as stagnation conditions and back pressure on performance are less well understood than for PDE’s. In this article we describe results from time-accurate calculations of RDE’s using algorithms that have successfully been used for PDE simulations previously. Results are obtained for stoichiometric hydrogen–air RDE’s operating at a range of stagnation pressures and back pressures. Conditions within the chamber are described as well as inlet and outlet conditions and integrated quantities such as total mass flow, force, and specific imPulse. Further computations examine the role of inlet stagnation pressure and back pressure on Detonation characteristics and engine performance. The pressure ratio is varied between 2.5 and 20 by varying both stagnation and back pressure to isolate controlling factors for the Detonation and performance characteristics. It is found that the Detonation wave height and mass flow rate are determined primarily by the stagnation pressure, whereas overall performance is closely tied to pressure ratio. Specific imPulses are calculated for all cases and range from 2872 to 5511 s, and are lowest for pressure ratios below 4. The reason for performance loss is shown to be associated with the secondary shock wave structure that sets up in the expansion portion of the RDE, which strongly effects the flow at low pressure ratios. Expansion to supersonic flow behind the Detonation front in RDE’s with higher pressure ratios isolate the Detonation section of the RDE and thus limit the effect of back pressure on the Detonation characteristics.
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numerical investigation of rotating Detonation Engines
46th AIAA ASME SAE ASEE Joint Propulsion Conference & Exhibit, 2010Co-Authors: Douglas Schwer, Kailas KailasanathAbstract:Rotating Detonation Engines (RDE’s) represent an alternative to the extensively studied Pulse Detonation Engines (PDE’s) for obtaining propulsion from the high efficiency Detonation cycle. Since it has received considerably less attention, the general flow-field and effect of parameters such as stagnation conditions, combustion chamber length, and fuel mixture on specific imPulse are less well understood than for PDE’s. In this paper we develop a model for doing time-accurate calculations of RDE’s in two and three dimensions, using algorithms that have successfully been used for PDE simulations previously. Results are shown for a stoichiometric hydrogen-air RDE operating at 10 atm, 300 K stagnation premixture conditions and 1 atm back pressure. Conditions within the chamber are described as well as inlet and outlet conditions and integrated quantities such as total mass flow, force, and specific imPulse. Further computations examined the role of back pressure and inlet stagnation pressure on performance. It was found that the specific imPulse was dependent on pressure ratio, whereas the mass flow and propulsive force were primarily dependent on the stagnation properties of the inlet micro-nozzles. The specific imPulse varied from 3845 sec to 5560 sec over a pressure ratio of 5 to 30. The specific imPulse for the 10 atm stagnation pressure, 1 atm back pressure was 5130 sec.
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recent developments in the research on Pulse Detonation Engines
40th AIAA Aerospace Sciences Meeting & Exhibit, 2002Co-Authors: Kailas KailasanathAbstract:Introduction I Nprinciple,Detonationsare an extremelyef cientmeans of combustinga fuel-oxidizermixture and releasing its chemical energy content. During the past 60 years or so, there have been numerous researcheffortsat harnessingthepotentialof Detonationsfor propulsion applications.1 There is a renewed interest lately on intermittent or Pulsed Detonations Engines. Eidelman et al. and Eidelman and Grossmann3 have reviewed some of the initial research as well as work done in the late 1980s on Pulse Detonation Engines (PDEs). The basic theory, design concepts, and the work in the early 1990s related to Pulse DetonationEngines have been discussedby Bussing and Pappas.4 The focus of a more recent review5 is on performance estimates fromvarious experimental, theoreticaland computational studies. More recently, work related to nozzles for PDEs has been discussed. Other reviews7i9 discussing the objectives and accomplishments of various programs are also available.The objective of this paper is to update the previousreviews, focusingon themore recent developmentsin the researchon PDEs. The review is restricted toworkopenlyavailablein the literaturebut includesongoingefforts around the world. Currently, there are several programs sponsored by Of ce of Naval Research (ONR), U.S. Air Force, NASA, Defense Advanced Research Projects Agency, and other agencies in the United States as well as several parallel efforts in Belarus, Canada, France, Japan, Russia, Sweden, and other countries.The results from some of these programs are just beginning to be published.A summary of recent progress and the various organizationsand people involved in PDE research in Japan has been presented.9 Reports of the basic PDE research sponsoredby ONR are available in the proceedingsof a recurringannualmeeting(forexample, seeRef. 10).Recentwork conducted outside the United States has been reported at international meetings on Detonations such as those held in Seattle11 (for more information, see http://www.engr.washington.edu/epp/icders/) and Moscow.12 Although an attempt is made to cover a broad range of the reported research, the shear volume of papers presented with PDEs in the title make it impractical to be exhaustive. Rather than providing a chronologicalreport, an attempt is made here to discuss the recent progress in terms of broad topic areas. The key issues that need to be resolved have been addressed in a number of papers (e.g., Refs. 13 and 14). The speci c order in which to discuss the various topics was determined by considering the schematic of an idealized, laboratory Pulse Detonation engine shown in Fig. 1. This idealizedengine is representativeof the device
S M Frolov - One of the best experts on this subject based on the ideXlab platform.
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Reduction of the Deflagration-to-Detonation Transition Distance and Time in a Tube with Regular Shaped Obstacles PHYSICAL CHEMISTRY
2020Co-Authors: S M Frolov, I V Semenov, P V Komissarov, P S Utkin, V V MarkovAbstract:Here, we suggest, for the first time, use of regular obstacles of special shape for acceleration of deflagration-to-Detonation transition (DDT). As shown by calculations and experiments, such obstacles make it possible to considerably decrease the DDT length and time as compared to regular rectangular obstacles. The new method of acceleration of the DDT can be used for designing compact combustion chambers of air-breathing Pulse Detonation Engines (PDEs). Detonation has been considered, until recently, only as an extremely undesirable scenario of an accidental explosion, as an inadmissible combustion regime in a piston engine, or as a powerful source of destruction in military operations. However, recently, a new field of study has been initiated and developed that deals with the creation of jet propulsion systems with controlled detonative fuel combustion, PDEs In In calculations, the final stage of DDT in a flat channel of height H with regular obstacles was considered after a relatively weak SW, with the Mach number å 0 and the compression phase duration τ , has formed capable of initiating ignition of the mixture when reflecting from the obstacles. The work dealt with the search for the shape of regular obstacles ensuring fast shock-toDetonation transition (SDT) by the mechanism described i
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shock wave and Detonation propagation through u bend tubes
Proceedings of the Combustion Institute, 2007Co-Authors: S M Frolov, V S Aksenov, I O ShamshinAbstract:Abstract The objective of the research outlined in this paper is to provide experimental and computational data on initiation, propagation, and stability of gaseous fuel–air Detonations in tubes with U-bends implying their use for design optimization of Pulse Detonation Engines (PDEs). The experimental results with the U-bends of two curvatures indicate that, on the one hand, the U-bend of the tube promotes the shock-induced Detonation initiation. On the other hand, the Detonation wave propagating through the U-bend is subjected to complete decay or temporary attenuation followed by the complete recovery in the straight tube section downstream from the U-bend. Numerical simulation of the process reveals some salient features of transient phenomena in U-tubes.
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shock wave and Detonation propagation through u bend tubes
Proceedings of the Combustion Institute, 2007Co-Authors: S M Frolov, V S Aksenov, I O ShamshinAbstract:Abstract The objective of the research outlined in this paper is to provide experimental and computational data on initiation, propagation, and stability of gaseous fuel–air Detonations in tubes with U-bends implying their use for design optimization of Pulse Detonation Engines (PDEs). The experimental results with the U-bends of two curvatures indicate that, on the one hand, the U-bend of the tube promotes the shock-induced Detonation initiation. On the other hand, the Detonation wave propagating through the U-bend is subjected to complete decay or temporary attenuation followed by the complete recovery in the straight tube section downstream from the U-bend. Numerical simulation of the process reveals some salient features of transient phenomena in U-tubes.
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optimization study of spray Detonation initiation by electric discharges
Shock Waves, 2005Co-Authors: S M Frolov, Ya V Basevich, V S Aksenov, S A PolikhovAbstract:Development of air-breathing Pulse Detonation Engines is faced with a challenging problem of Detonation initiation in fuel sprays at distances feasible for propulsion applications. Extensive experimental study on initiation of a confined n-hexane spray Detonation in air by electric dis- charges is reported. It is found that for direct initiation of spray Detonation with minimal energy requirements (1) it is worth to use one discharger located near the closed end of a Detonation tube and at least one additional discharger down- stream from it to be triggered in-phase with primary shock wave arrival; (2) the discharge area should be properly insu- lated to avoid electric loss to metal tube walls; (3) discharge duration should be minimized to at least 50 µs; (4) discharge channel should preferably occupy a large portion of a tube cross-section; (5) test tube should be preferably of a diame- ter close to the limiting tube diameter; (6) gradual transition between the volume with electric discharger and the tube should be used; and (7) a powerful electric discharger uti- lized for generating a primary shock wave can be replaced by a primary shock wave generator comprising a relatively low-energy electric discharger, Shchelkin spiral, and tube coil. With all these principles implemented, the rated elec- tric energy of about 100 J was required to initiate n-hexane spray-air Detonation in a 28-mm tube at a distance of about 1 m from the atomizer.
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O R I G I NA L A RT I C L E Optimization study of spray Detonation initiation by electric discharges
2005Co-Authors: S M Frolov, V S Aksenov, S A PolikhovAbstract:Abstract Development of air-breathing Pulse Detonation Engines is faced with a challenging problem of Detonation initiation in fuel sprays at distances feasible for propulsion applications. Extensive experimental study on initiation of a confined n-hexane spray Detonation in air by electric discharges is reported. It is found that for direct initiation of spray Detonation with minimal energy requirements (1) it is worth to use one discharger located near the closed end of a Detonation tube and at least one additional discharger downstream from it to be triggered in-phase with primary shock wave arrival; (2) the discharge area should be properly insulated to avoid electric loss to metal tube walls; (3) discharge duration should be minimized to at least 50 µs; (4) discharge channel should preferably occupy a large portion of a tube cross-section; (5) test tube should be preferably of a diameter close to the limiting tube diameter; (6) gradual transition between the volume with electric discharger and the tube should be used; and (7) a powerful electric discharger utilized for generating a primary shock wave can be replaced by a primary shock wave generator comprising a relatively low-energy electric discharger, Shchelkin spiral, and tube coil. With all these principles implemented, the rated electric energy of about 100 J was required to initiate n-hexane spray-air Detonation in a 28-mm tube at a distance of about 1 m from the atomizer. Keywords Detonation initiation · Liquid-fuel spray · Electric discharge · Pulse Detonation engin
Scott T Sanders - One of the best experts on this subject based on the ideXlab platform.
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monitoring and control of a Pulse Detonation engine using a diode laser fuel concentration and temperature sensor
Proceedings of the Combustion Institute, 2002Co-Authors: Scott T Sanders, Jay B Jeffries, Ronald K HansonAbstract:Fuel measurements are needed to accurately tailor fued charges in Pulse Detonation Engines (PDEs) to improve engine performance and to validate PDE models and computations. Here, we report simultaneous concentration and temperature measurements of C 2 H 4 fuel in a PDE using a newly developed diode-laser absorption sensor. These measurements enable characterization of the fuel loading and ignition timing of the engine. Based on these characterizations, a real-time control system that optimizes fuel consumption and maximizes specific imPulse in the engine has been realized. Similar measurements of C 2 H 4 concentration and temperature were used to characterize Pulse-to-Pulse interference resulting from loading fresh fuel/oxygen reactants into hot combustion products. The sensor was used in a simple control scheme to minimize such interference, illustrating its potential role in control systems to maximize the engine's operation rate. During these studies, the sensor demonstrated two valuable improvements over traditional absorption spectroscopic techniques: (1) increased robustness and accuracy and (2) simultaneous measurements of concentration and temperature. These improvements are enbled by broad wavelength scanning of the Q-branch spectra of C 2 H 4 near 1.62 μm. The success achieved in these small-scale tests provides strong support for expanded use of diode-laser sensors in propulsion applications.
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diode laser sensor for monitoring multiple combustion parameters in Pulse Detonation Engines
Proceedings of the Combustion Institute, 2000Co-Authors: Scott T Sanders, Jeffrey A Baldwin, Thomas P Jenkins, Douglas S Baer, Ronald K HansonAbstract:Diode-laser absorption spectroscopy techniques have been adapted and, applied for in situ measurements of pertinent combustion parameters in Pulse Detonation Engines (PDEs). A sensor employing five multiplexed diode lasers operating in the 1300–1800 nm spectral region has been developed for monitoring gas temperature, H2O concentration, liquid fuel concentration, and soot volume fraction. Gas temperature is determined from the ratio of H2O absorbances at different wavelengths: water mole fraction and fuel and soot volume fractions are determined from the measured gas temperature and absorbances at selected wavelengths. The sensor's time response (0.5 μs) and non-intrusive, nature make it suitable for measurements in the hostile environment generated by PDEs. The sensor was used to monitor a 4 cm diameter PDE operating on a JP-10/oxygen aerosol. Measurements revealed charges of non-uniform equivalence ratio at ignition. Detonations processing such charges reached 95% of the Chapman-Jouget velocity and gas pressures predicted for a stoichiometric, uniform load. Gas temperature and H2O concentration, however, reached only ≈50% of the Chapman-Jouget predictions, as a result of the decreasing fuel concentration along the length of the engine. The sensor also revealed the presence of hot H2O for a long duration (>100 ms) relative to the duration of the pressure Pulse (≈500 μs) in the blowdown following the Detonation. The engine performance information recorded by the sensor is expected to enhance PDE modeling and optimization efforts, potentially enabling PDE combustion control.
