Модель гибридного ракетного двигателя. Вычисления, проект и испытания

На даний час і у майбутньому ракетні двигуни будуть найголовнішими засобами виводу на орбіту космічних транспортних апаратів. В даний час найважливішою вимогою при проектуванні двигуна ракети є зменшення її вартості і максимальне збільшення енерговіддачі. Проектування ракетних двигунів - довготривалий і трудомісткий процес, метою якого є виробництво дешевого і високоякісного двигуна, що має мінімальний вплив на навколишнє середовище. Слідуючи зазначеним вимогам, Варшавський Технологічний Університет спільно з Варшавським авіаційним Інститутом розпочали програму екологічно безпечного розвитку ракетних двигунів. Експериментальний гібридний двигун ракети був розроблений і виготовлений для перевірки нової формули твердого палива. Дана стаття містить дослідження безпечної роботи двигуна з окислювачем Al/AN/HTPB, використовуючи при цьому лабораторний дослідний стенд перевірки ракетного гібридного двигуна. Основна мета цієї роботи – це проектування простого ракетного двигуна з наступною можливістю його подальшого розвитку і поліпшення.Now and in the foreseeable future rocket engine will be the most basic propulsion of space vehicle. Nowadays the most important condition in design of rocket engine is the cost reduction and increasing thrust to weight ratio as much as possible. The design of rocket engines is exhaustive and difficult process. It must produce low cost and high performance engine with minimal influence on the environment. Following these requirements, Warsaw University of Technology jointly with Institute of Aviation in Warsaw, started their own program on ecologically safe propulsion development. The experimental hybrid rocket motor has been designed and manufactured to test a new formula of solid fuel. The paper explores the performance and safety implications associated with the oxidizer enhanced Al/AN/HTPB grain by using of a laboratory scale hybrid rocket motor test stand. The main objective of this work was to design simple rocket engine that could smoothly be developed and possibly improved in the future.На данный момент и в обозримом будущем ракетные двигатели будут самыми основными двигательными установками космических транспортных средств. В настоящее время самым важным условием при проектировании двигателя ракеты является уменьшение ее стоимости и максимальное увеличение соотношения тяги к весу. Проектирование ракетных двигателей – продолжительный и трудоемкий процесс, целью которого является производство дешевого и высококачественного двигателя с минимальным влиянием на окружающую среду. Следуя указанным требованиям, Варшавский Технологический Университет совместно с Варшавским авиационным институтом начали программу экологически безопасного развития ракетных двигательных установок. Экспериментальный гибридный двигатель ракеты был разработан и изготовлен для проверки новой формулы твердого топлива. Данная статья содержит исследования безопасной работы двигателя с окислителем Al/AN/HTPB, используя при этом лабораторный испытательный стенд проверок ракетного гибридного двигателя. Основная цель этой работы состоит в проектировании простого ракетного двигателя с последующей возможностью его дальнейшего развития и улучшения

An ecohydrology model of the Guadiana Estuary (South Portugal)

A 1-D ecohydrology model is proposed that integrates physical, chemical and biological processes in the Guadiana Estuary during low flow conditions and that predicts the ecosystem health as determined by the following variables: river discharge, nutrients, suspended particulate matter, phytoplankton, zooplankton, bivalves, zooplanktivorous fish and carnivorous/omnivorous fish. Low flow conditions prevail now that the Alqueva dam has been constructed. The ecological sub-model is based on the non-linear Lotka-Volterra equation. The model is successful in capturing the observations of along-river changes in these variables. It suggests that both bottom-up and top-down ecological processes control the Guadiana Estuary ecosystem health. A number of sensitivity tests show that the model is robust and can be used to predict e within likely error bounds provided by the sensitivity tests e the consequences on the estuary ecosystem health of human activities throughout the river catchment, such as the irrigation farming downstream of the Alqueva dam, reclamation of the salt marshes by urban developments, and flow regulation by the Alqueva dam. The model suggests that the estuarine ecosystem health requires transient river floods and is compromised by flow regulation by the Alqueva dam. Remedial measures are thus necessary

Swimming abilities of temperate pelagic fish larvae prove that they may control their dispersion in coastal areas

The Sense Acuity and Behavioral (SAAB) Hypothesis proposes that the swimming capabilities and sensorial acuity of temperate fish larvae allows them to find and swim towards coastal nursery areas, which are crucial for their recruitment. To gather further evidence to support this theory, it is necessary to understand how horizontal swimming capability varies along fish larvae ontogeny. Therefore, we studied the swimming capability of white seabream Diplodus sargus (Linnaeus, 1758) larvae along ontogeny, and their relationship with physiological condition. Thus, critical swimming speed (U-crit) and the distance swam (km) during endurance tests were determined for fish larvae from 15 to 55 days post-hatching (DPH), and their physiological condition (RNA, DNA and protein contents) was assessed. The critical swimming speed of white seabream larvae increased along ontogeny from 1.1 cm s(-1) (15 DPH) to 23 cm s(-1) (50 and 55 DPH), and the distance swam by larvae in the endurance experiments increased from 0.01 km (15 DPH) to 86.5 km (45 DPH). This finding supports one of the premises of the SAAB hypothesis, which proposes that fish larvae can influence their transport and distribution in coastal areas due to their swimming capabilities. The relationship between larvae's physiological condition and swimming capabilities were not evident in this study. Overall, this study provides critical information for understanding the link between population dynamics and connectivity with the management and conservation of fish stocks.Funding Agency Portuguese Foundation for Science and Technology SFRH/BD/104209/2014 Portuguese Foundation for Science and Technology UID/Multi/04326/2019 FCT, under the Transitional Norm DL57/2016/CP[1361]/CT[CT0008 CLIMFISH project-A framework for assess vulnerability of coastal fisheries to climate change in Portuguese coast n2/SAICT/2017-SAICTinfo:eu-repo/semantics/publishedVersio

Dependence of pp->pp pi0 near Threshold on the Spin of the Colliding Nucleons

A polarized internal atomic hydrogen target and a stored, polarized beam are used to measure the spin-dependent total cross section Delta_sigma_T/sigma_tot, as well as the polar integrals of the spin correlation coefficient combination A_xx-A_yy, and the analyzing power A_y for pp-> pp pi0 at four bombarding energies between 325 and 400 MeV. This experiment is made possible by the use of a cooled beam in a storage ring. The polarization observables are used to study the contribution from individual partial waves.Comment: 6 pages, 1 table, 4 figures, corrected equations 2 and

Undular tidal bores: Effect of channel constriction and bridge piers

A tidal bore may occur in a macro-tidal estuary when the tidal range exceeds 4.5-6 m and the estuary bathymetry amplifies the tidal wave. Its upstream propagation induces a strong mixing of the estuarine waters. The propagation of undular tidal bores was investigated herein to study the effect of bridge piers on the bore propagation and characteristics. Both the tidal bore profile and the turbulence generated by the bore were recorded. The free-surface undulation profiles exhibited a quasi-periodic shape, and the potential energy of the undulations represented up to 30% of the potential energy of the tidal bore. The presence of the channel constriction had a major impact on the free-surface properties. The undular tidal bore lost nearly one third of its potential energy per surface area as it propagated through the channel constriction. The detailed instantaneous velocity measurements showed a marked effect of the tidal bore passage suggesting the upstream advection of energetic events and vorticity "clouds" behind the bore front in both channel configurations: prismatic and with constriction. The turbulence patches were linked to some secondary motions and the proposed mechanisms were consistent with some field observations in the Daly River tidal bore. The findings emphasise the strong mixing induced by the tidal bore processes, and the impact of bridge structures on the phenomenon. © 2010 Springer Science+Business Media B.V

Research on dust explosions at the University of Michigan

Dust explosion research carried out at the University of Michigan during the last two decades has been summarized. Significant results are presented on the smoldering combustion of dust heaps, turbulent combustion of premixed dust clouds, entrainment and combustion of layered dust, and on shock wave ignition of particles and shock wave initiated detonative combustion. Also, information on the detonation of hybrid mixtures and gaseous mixtures containing nonreactive particles is given.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29913/1/0000270.pd

Kelvin-Helmholtz instability in the presence of variable viscosity for mudflow resuspension in estuaries

The temporal stability of a parallel shear flow of miscible fluid layers of dif- ferent density and viscosity is investigated through a linear stability analysis and direct numerical simulations. The geometry and rheology of this Newto- nian fluid mixing can be viewed as a simplified model of the behavior of mud- flow at the bottom of estuaries for suspension studies. In this study, focus is on the stability and transition to turbulence of an initially laminar configuration. A parametric analysis is performed by varying the values of three control pa- rameters, namely the viscosity ratio, the Richardson and Reynolds numbers, in the case of initially identical thickness of the velocity, density and viscosity profiles. The range of parameters has been chosen so as to mimic a wide variety of real configurations. This study shows that the Kelvin-Helmholtz instability is controlled by the local Reynolds and Richardson numbers of the inflection point. In addition, at moderate Reynolds number, viscosity strat- ification has a strong influence on the onset of instability, the latter being enhanced at high viscosity ratio, while at high Reynolds number, the influ- ence is less pronounced. In all cases, we show that the thickness of the mixing layer (and thus resuspension) is increased by high viscosity stratification, in particular during the non-linear development of the instability and especially pairing processes. This study suggests that mud viscosity has to be taken into account for resuspension parameterizations because of its impact on the inflec- tion point Reynolds number and the viscosity ratio, which are key parameters for shear instabilities

The shock wave ignition of dusts

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76923/1/AIAA-1984-205.pd

Investigation of organic dust detonation in the presence of chemically inert particles,

The results of experimental studies of organic dust detonation in the presence of chemically inert particles are presented. Tests were carried out using a vertical detonation tube, and direct streak pictures showing the flame acceleration and pressure and temperature records were obtained. Flax dust, dispersed in an oxygen atmosphere, was used as the fuel, and two kinds of quartz sand were introduced as nonreacting particles. It was found that addition of inert particles caused a linear decrease of the detonation wave velocity but had no special influence on the transition distance. Calculations using the Gordon McBride Code Showed that propagation of the detonation wave in a dust-oxygen mixture requires that the dust particles burnout at a level of about 70% but addition of inert particles increased the necessary burnout level to over 80% (with a significant decrease of the detonation wave velocity).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31938/1/0000891.pd

A review on substances and processes relevant for optical remote sensing of extremely turbid marine areas, with a focus on the Wadden Sea

The interpretation of optical remote sensing data of estuaries and tidal flat areas is hampered by optical complexity and often extreme turbidity. Extremely high concentrations of suspended matter, chlorophyll and dissolved organic matter, local differences, seasonal and tidal variations and resuspension are important factors influencing the optical properties in such areas. This review gives an overview of the processes in estuaries and tidal flat areas and the implications of these for remote sensing in such areas, using the Wadden Sea as a case study area. Results show that remote sensing research in extremely turbid estuaries and tidal areas is possible. However, this requires sensors with a large ground resolution, algorithms tuned for high concentrations of various substances and the local specific optical properties of these substances, a simultaneous detection of water colour and land-water boundaries, a very short time lag between acquisition of remote sensing and in situ data used for validation and sufficient geophysical and ecological knowledge of the area. © 2010 The Author(s)