Download or read book Control of Flow Structure and Ignition of Hydrocarbon Fuel in Cavity and Behind Wallstep of Supersonic Duct by Filamentary DC Discharge written by and published by . This book was released on 2011 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report results from a contract tasking Institute of High Temperatures RAS as follows: The contractor will investigate the phenomena of plasma-induced ignition of high speed, low temperature air-fuel mixtures using a recirculation zone created by a rearward facing wall step and wall cavity. The plasma will be generated using a multi-electrode, quasi direct-current electrical discharge. Fuel injectors will be located in the recirculation zone. The effects of plasma induced ignition, mixing intensification, flame-stabilization, and combustion completeness will be evaluated. Investigations will be carried out using both gaseous and liquid hydrocarbon fuels. Diagnostics include high speed video, Schlieren photography, pressure distribution measurements, electrical measurements, optical spectroscopy and infrared absorption spectroscopy. The research is mainly experimental, but will include several analytical and computational efforts for better understanding and verification of the results.

Download or read book Effect of Flow Distortion on Fuel Mixing and Combustion in an Upstream fueled Cavity Flameholder for a Supersonic Combustor written by Steven J. Etheridge and published by . This book was released on 2012 with total page 55 pages. Available in PDF, EPUB and Kindle. Book excerpt: Typical studies of scramjet combustion employ as uniform a flowpath as possible. These studies are important to isolate the effects of a given combustor configuration. However, such studies tend to ignore the effects of a shock train created by the vehicle installation and that this shock train changes over the flight envelope. Consequently, the performance of a given configuration is measured without considering the considerable effects of this shock train or how it changes with different flight conditions. This thesis includes experimental and computational studies of the effects of an incident shockwave on the flowfield, fuel distribution and combustion within a cavity flameholder with upstream fuel injection. The effect of the shockwave location (on the upstream fuel jet or over the cavity) and shock angle are controlled by adjusting a shock generator mounted in the tunnel test section. The effect of fuel injection momentum ratio is also examined. Shadowgraphy is used to characterize the flowfield while planar laser induced fluorescence of the NO and OH molecules are used to measure the fuel mixing and combustion, respectively. These experimental data are compared with CFD solutions of the Reynolds Averaged Navier-Stokes equations provided in previous CFD work. The effect of the shock on the cavity shear layer is found to control the fuel distribution within the cavity. The shock on jet impingement forces the shear layer deep within the cavity and results in higher concentrations near the cavity centerline, but low mixing uniformity. The shock on cavity case causes the shear layer to separate upstream of the cavity, mixing uniformity is enhanced by the increased breakup of the fuel plume. Combustion is stronger and more uniform in the shock on cavity case, while it is limited to the edges of the cavity with shock impingement on the jet. The greater mixing afforded in the shock on cavity case reduces the fuel concentration near the centerline and permits stronger burning in the center of the cavity. Small changes in the fuel injection momentum ratio (doubling) do not strongly affect the pattern of fuel distribution in any case. Combustion in the shock on cavity case is reduced by increasing fuel injection momentum because the fuel concentration at the centerline is too high. Small increases in the shock angle did not strongly affect the results.

Download or read book Ignition and Combustion of Liquid Hydrocarbon Fuels in Supersonic Flow written by Simon Slutsky and published by . This book was released on 1969 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental study was carried out to investigate the combustion of a liquid hydrocarbon (hexane) injected into a supersonic stream. Injection modes included wall and central injection configurations. Extremely rapid and intense heat release phenomena were obtained. It was concluded that this mode of combustion could be made to compete with that of pure gas phase combustion for many technological applications. A preliminary theoretical model of the combustion mechanism was constructed which accounts for many of the observed phenomena, and which explains the very rapid combustion characteristics.

Download or read book On Recessed Cavity Flame holders in Supersonic Cross flows written by Ghislain Jean Retaureau and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Flame-holding in a recessed cavity is investigated experimentally in a Mach 2.5 preheated cross-flow for both stable and unstable combustion, with a relatively low preheating. Self-sustained combustion is investigated for stagnation pressures and temperatures reaching 1.4 MPa and 750 K. In particular, cavity blowout is characterized with respect to cavity aspect ratio (L/D =2.84 - 3.84), injection strategy (floor - ramp), aft ramp angle (90 deg - 22.5 deg) and multi-fuel mixture (CH4-H2 or CH4-C2H4 blends). The results show that small hydrogen addition to methane leads to significant increase in flame stability, whereas ethylene addition has a more gradual effect. Since the multi-fuels used here are composed of a slow and a fast chemistry fuel, the resulting blowout region has a slow (methane dominant) and a fast (hydrogen or ethylene dominant) branch. Regardless of the fuel composition, the pressure at blowout is close to the non-reacting pressure imposed by the cross-flow, suggesting that combustion becomes potentially unsustainable in the cavity at the sub-atmospheric pressures encountered in these supersonic studies. The effect of preheating is also investigated and results show that the stability domain broadens with increasing stagnation temperature. However, smaller cavities appear less sensitive to the cross-flow preheating, and stable combustion is achieved over a smaller range of fuel flow rate, which may be the result of limited residence and mixing time. The blowout data point obtained at lower fuel flow rate fairly matches the empirical model developed by Rasmussen et al. for floor injection phi = 0.0028 Da^-.8, where phi is the equivalence ratio and Da the Damkohler number. An alternate model is proposed here that takes into account the ignition to scale the blowout data. Since the mass of air entrained into the cavity cannot be accurately estimated and the cavity temperature is only approximated from the wall temperature, the proposed scaling has some uncertainty. Nevertheless the new phi-Da scaling is shown to preserve the subtleties of the blowout trends as seen in the current experimental data.

Download or read book Experimental Studies of Plasma assisted Ignition and MHD Supersonic Flow Control written by Rodney Meyer and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Toward Plasma Assisted Ignition in Scramjets written by and published by . This book was released on 2003 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Air Force plasma ignition program is assessing the prospect of main-fuel ignition with plasma generating devices in a supersonic flow. As the study progresses baseline conditions of operation are being established such as the required operational time of the device to initiate a combustion shock train. The two plasma torches currently under investigation consist of a DC constricted-arc design from the Virginia Polytechnic Institute and State University and an AC unconstricted-arc design based on a modified spark-plug from Polytechnic University. The plasma torches are realistic in size and operate within current power constraints while differing substantially in orifice geometry. In order to compare the potential of each concept the flow physics of each part of the igniter/fuel-injector/combustor system are being studied. In each step of the program, we utilize CFD and experiments to help define and advance the ignition process. To understand the constraints involved with ignition process of a hydrocarbon fuel jet an experimental effort to study gaseous and liquid hydrocarbons is underway, involving the testing of ethylene and JP-7 fuels with nitrogen and air plasmas. Results from the individual igniter studies have shown the plasma igniters to produce hot pockets of highly excited gas with peak temperatures up to (and in some cases above) 5000 K at only 2-kW total input power. In addition ethylene and JP-7 flames with a significant level of OH as determined by OH PLIF were also produced in a Mach-2 supersonic flow with a total temperature and pressure of 590 K and 5.4 atm respectively.

Download or read book Numerical Study of Cavity Based Flameholder with Slot Injection for Supersonic Combustion written by Independently Published and published by . This book was released on 2016-06-30 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: The current work has focused on finding the optimum cavity properties to enhance themixing phenomenon and combustion processes in supersonic flow using ComputationalFluid Dynamics (CFD) ANSYS Fluent. Various models has been modeled with differentvalues of offset ratios (OR) and aft ramp angles (ϴ) while keeping the length-to-depth ratioconstant. All cavity flows have taken open type i.e. length-to-depth ratio

Download or read book Investigation of Supersonic Combustion of Hydrocarbon Fuel rich Hot Gas in Scramjet Combustor written by M. Situ and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Kinematics of Mixing written by J. M. Ottino and published by Cambridge University Press. This book was released on 1989 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt: In spite of its universality, mixing is poorly understood and generally speaking, mixing problems are attacked on a case-by-case basis. This is the first book to present a unified treatment of the mixing of fluids from a kinematical viewpoint. The author's aim is to provide a conceptually clear basis from which to launch analysis and to facilitate an understanding of the numerous mixing problems encountered in nature and technology. After presenting the necessary background in kinematics and fluid dynamics, Professor Ottino considers various examples of dealing with necessary background in dynamical systems and chaos. The book assumes little previous knowledge of fluid dynamics and dynamical systems and can be used as a textbook by final-year undergraduates, graduate students and researchers in applied mathematics, engineering science, geophysics and physics who have an interest in fluid dynamics, continuum mechanics and dynamical systems. It is profusely illustrated in colour, with many line diagrams and half-tones. Systems which illustrate the most important concepts, many exercises and examples are included.

Download or read book Three Dimensional Imaging Techniques written by Takanori Okoshi and published by . This book was released on 2011-03 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: A seminal early text on lenticular and holographic imaging, Takanori Okoshi's "Three-Dimensional Imaging Techniques" provides analysis and insights into the fundamentals of 3-D perception and the creation of 3-D imagery as well as a history of its technological development.

Download or read book Mixing of Hydrogen Injected from Multiple Injectors Normal to a Supersonic Airstream written by R. Clayton Rogers and published by . This book was released on 1971 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Study of the Mixing of Hydrogen Injected Normal to a Supersonic Airstream written by R. Clayton Rogers and published by . This book was released on 1971 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: Jet to free-stream dynamic pressure ratio effects on penetration and mixing of hydrogen injected normal to supersonic airstreams.

Download or read book Tailored Excitation for Frequency Response Measurement Applied to the X 43a Flight Vehicle written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-08-26 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: An important aspect of any flight research project is assessing aircraft stability and flight control performance. In some programs this assessment is accomplished through the estimation of the in-flight vehicle frequency response. This estimation has traditionally been a lengthy task requiring separate swept sine inputs for each control axis at a constant flight condition. Hypersonic vehicles spend little time at any specific flight condition while they are decelerating. Accordingly, it is difficult to use traditional methods to calculate the vehicle frequency response and stability margins for this class of vehicle. A technique has been previously developed to significantly reduce the duration of the excitation input by tailoring the input to excite only the frequency range of interest. Reductions in test time were achieved by simultaneously applying tailored excitation signals to multiple control loops, allowing a quick estimate of the frequency response of a particular aircraft. This report discusses the flight results obtained from applying a tailored excitation input to the X-43A longitudinal and lateral-directional control loops during the second and third flights. The frequency responses and stability margins obtained from flight data are compared with preflight predictions.