Combustion Processes in Hybrid Rocket Engines

In recent years, there has been a resurgence of interest in the development of hybrid rocket engines for advanced launch vehicle applications. Hybrid propulsion systems use a solid fuel such as hydroxyl-terminated polybutadiene (HTPB) along with a gaseous/liquid oxidizer. The performance of hybrid combustors depends on the convective and radiative heat fluxes to the fuel surface, the rate of pyrolysis in the solid phase, and the turbulent combustion processes in the gaseous phases. These processes in combination specify the regression rates of the fuel surface and thereby the utilization efficiency of the fuel. In this paper, we employ computational fluid dynamics (CFD) techniques in order to gain a quantitative understanding of the physical trends in hybrid rocket combustors. The computational modeling is tailored to ongoing experiments at Penn State that employ a two dimensional slab burner configuration. The coordinated computational/experimental effort enables model validation while providing an understanding of the experimental observations. Computations to date have included the full length geometry with and with the aft nozzle section as well as shorter length domains for extensive parametric characterization. HTPB is sed as the fuel with 1,3 butadiene being taken as the gaseous product of the pyrolysis. Pure gaseous oxygen is taken as the oxidizer. The fuel regression rate is specified using an Arrhenius rate reaction, which the fuel surface temperature is given by an energy balance involving gas-phase convection and radiation as well as thermal conduction in the solid-phase. For the gas-phase combustion, a two step global reaction is used. The standard kappa - epsilon model is used for turbulence closure. Radiation is presently treated using a simple diffusion approximation which is valid for large optical path lengths, representative of radiation from soot particles. Computational results are obtained to determine the trends in the fuel burning or regression rates as a function of the head-end oxidizer mass flux, G=rho(e)U(e), and the chamber pressure. Furthermore, computation of the full slab burner configuration has also been obtained for various stages of the burn. Comparisons with available experimental data from small scale tests conducted by General Dynamics-Thiokol-Rocketdyne suggest reasonable agreement in the predicted regression rates. Future work will include: (1) a model for soot generation in the flame for more quantitative radiative transfer modelling, (2) a parametric study of combustion efficiency, and (3) transient calculations to help determine the possible mechanisms responsible for combustion instability in hybrid rocket motors

Teaching the College Introductory Survey in the High School: Reaching out to AP U.S. History Teachers

The College Board\u27s Advanced Placement (AP) program now serves as a strong vehicle for promoting high academic standards, with college-level work for high school students. The product of a unique collaboration between high school teachers and college faculty dating back to the 1950s, AP is the de facto standard for academic programs that help students make the transition from high school to college. The recognition of AP as a program of academic excellence has, in turn, fueled a rapid expansion in the number of students taking the examinations. Last year, approximately 250,000 students took the Advanced Placement United States History examination. With this growth comes the continued twin challenges of maintaining high standards that correspond with advances in each discipline, and expanding access to these rigorous courses in much more equitable ways. In this article we provide a brief overview of college faculty\u27s involvement in the school-college collaboration that is AP, including the College Board\u27s expanded efforts to strengthen its support to AP teachers

Adverse drug effects monitoring of amlodipine in a tertiary care hospital

Background: Amlodipine have been widely used drug for the treatment of Hypertension. It has many beneficial effects and less side effects. But, only very few adverse effects of Amlodipine have been documented and many were not reported. So, this study will bring out the possible adverse effect of Amlodipine.Methods: This study included 100 patients with hypertension who are taking amlodipine only. Patients who were willing to participate in the study were given a questionnaire containing demographic data and adverse drug profile of amlodipine. The symptoms of adverse drug reaction were documented. They were also asked about the other symptoms they are having, other than the questionnaire. The causality assessment was done by WHO assessment scale and severity by using modified Hartwig seigel severity assessment scale.Results: This study showed that most of the patients belong to 51-60 years age group. Mostly they were females, and many were having disease for less than a year. Most of the patients developed adverse drug reaction. Many patients had more than one adverse drug reaction. The commonest adverse effect were fatigue, palpitation, dizziness, insomnia, headache, joint pain, light-headedness, somnolence, nausea, flushing abdominal pain, tremor, leg pain, neck pain, back pain and edema. The adverse drug reaction(ADRs) mostly belongs to possible category and were mild.Conclusions: Most of the patients who were taking amlodipine had atleast one adverse drug reaction during their treatment period. It is mild, needs dose adjustment and healthy life style modification

Critical Analysis on the Structural and Magnetic Properties of Bulk and Nanocrystalline Cu-Fe-O

Nanocrystalline and bulk samples of “Fe”-doped CuO were prepared by coprecipitation and ceramic methods. Structural and compositional analyses were performed using X-ray diffraction, SEM, and EDAX. Traces of secondary phases such as CuFe2O4, Fe3O4, and α-Fe2O3 having peaks very close to that of the host CuO were identified from the Rietveld profile analysis and the SAED pattern of bulk and nanocrystalline Cu0.98Fe0.02O samples. Vibrating Sample Magnetometer (VSM) measurements show hysteresis at 300 K for all the samples. The ferrimagnetic Neel transition temperature () was found to be around 465°C irrespective of the content of “Fe”, which is close to the value of cubic CuFe2O4. High-pressure X-Ray diffraction studies were performed on 2% “Fe”-doped bulk CuO using synchrotron radiation. From the absence of any strong new peaks at high pressure, it is evident that the secondary phases if present could be less than the level of detection. Cu2O, which is diamagnetic by nature, was also doped with 1% of “Fe” and was found to show paramagnetic behavior in contrast to the “Fe” doped CuO. Hence the possibility of intrinsic magnetization of “Fe”-doped CuO apart from the secondary phases is discussed based on the magnetization and charge state of “Fe” and the host into which it is substituted

Hybrid Analog-Digital Precoding Revisited Under Realistic RF Modeling

In this letter, we revisit hybrid analog-digital precoding systems with emphasis on the modeling of their radio-frequency (RF) losses, to realistically evaluate their benefits in 5G system implementations. We focus on fully-connected analog beamforming networks (FC-ABFNs) and on discrete Fourier transform implementations, and decompose these as a bank of commonly used RF components. We then model their losses based on their S-parameters. Our results reveal that the performance and energy efficiency of hybrid precoding systems are severely affected once these, commonly ignored, losses are considered in the overall design. In this context, we also show that hybrid precoder designs similar to Butler matrices are capable of providing better performances than FC-ABFN for systems with a large number of RF chains