scholarly journals Some Key Issues in Hypersonic Propulsion

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3690
Author(s):  
Claudio Bruno ◽  
Antonella Ingenito
Keyword(s):  
Kinetic Energy ◽  
Constant Volume ◽  
Supersonic Combustion ◽  
Relative Importance ◽  
Friction Drag ◽  
Wave Versus ◽  
Hypersonic Propulsion ◽  
Key Issues ◽  
Drag Ratio ◽  
Critical Aspects

This paper summarizes and discusses some critical aspects of flying hypersonically. The first is the L/D (lift over drag) ratio determining thrust and that in turn depends on the slenderness Küchemann’s τ parameter. This second parameter is found to depend on the relative importance of wave versus friction drag. Ultimately, all engineering drag is argued to depend on vorticity formed at the expense of the vehicle kinetic energy, thus requiring work by thrust. Different mixing strategies are discussed and shown to depend also on mechanisms forming vorticity when the regime is compressible. Supersonic combustion is briefly analyzed and found, at sufficiently high combustor Mach, to take place locally at constant volume, unlike conventional Brayton cycles.

Numerical Simulation of Supersonic Combustion in Quasi One-Dimensional Flow

1991 ◽  
Author(s):  
T. Gary Yip
Keyword(s):  
Flow Model ◽  
Cone Angle ◽  
Initial Pressure ◽  
Supersonic Combustion ◽  
Propulsion Systems ◽  
One Dimensional ◽  
Hypersonic Propulsion ◽  
Dimensional Flow ◽  
Conical Shock ◽  
Shock System

Abstract Supersonic combustion induced by a two-shock system has been studied using a chemical nonequilibrium, quasi one-dimensional flow model. The combustion of stoichiometric, premixed H2-air is described by a chemistry model which consists of 11 species and 28 reactions. The freestream Mach numbers used in this calculations are 8, 10 and 12. The initial pressure is 0.01 atm and temperature 300 K. The first of the two shocks is a conical shock and the second is its reflection. Supersonic combustion has been predicted to occur at combustor pressures between 0.8 and 2.9 atmospheres, and temperatures between 1500 and 3000 K. The Mach number of the flow in the combustor is between 1.7 and 4. These combustor conditions are typical of the future hypersonic propulsion systems. The results also show the changes in the composition of the flow during the induction and heat release phases. The two-shock system is assumed to be generated by a cone. For Mach 8, 10 and 12, the minimum cone angle for generating a strong enough two-shock system to induce supersonic combustion has also been identified.

Fragmentation of alkoxide ions following collisional activation. An energy-resolved study

1988 ◽  
Vol 66 (11) ◽  
pp. 2947-2953 ◽  
Author(s):  
Roger S. Mercer ◽  
Alex G. Harrison
Keyword(s):  
Kinetic Energy ◽  
Collisional Activation ◽  
Collision Energy ◽  
Relative Importance ◽  
Elimination Reaction ◽  
Proton Abstraction ◽  
Relative Stabilities ◽  
Collisionally Activated Dissociation ◽  
Reaction Channels ◽  
Alkane Elimination

The collisionally activated dissociation reactions of the C2 to C5 alkoxide ions have been studied for collisons occurring at 8 keV kinetic energy and also over the range 5 to 100 eV kinetic energy. The alkoxide ions fragment by 1,2-elimination of H2 and/or an alkane. Thus, primary alkoxide ions fragment by elimination of H2 only, secondary alkoxide ions show elimination of H2 and alkane molecules, while tertiary alkoxide ions show elimination of alkanes only. In alkane elimination, loss of CH4 is much more facilie than loss of larger alkanes. For secondary alkoxide ions, where more than one elimination reaction occurs, the energy dependence of fragmentation has been explored over the collision energy range 5 to 100 eV. The results are interpreted in terms of a step-wise mechanism involving formation of an anion-carbonyl compound ion-dipole complex, followed by proton abstraction by the H− or alkyl anion leading to the final products. The relative importance of the reaction channels is determined by the relative stabilities of these ion-dipole complexes.

scholarly journals Long Distance Managerial Intervention in Overseas Conflicts: Helping Missionaries Reframe Conflict along Multiple Dimensions

2010 ◽  
Vol 38 (3) ◽  
pp. 281-293 ◽  
Author(s):  
David R. Dunaetz
Keyword(s):  
Conflict Management ◽  
Relative Importance ◽  
Long Distance ◽  
Home Office ◽  
Office Management ◽  
Multiple Dimensions ◽  
Rich Media ◽  
Present Information ◽  
Key Issues ◽  
The Relationship

Effective ways of conflict management must be found for missionaries when no trusted mediator in the region is available. Home office management or leaders in other regions can intervene through context rich media such as the telephone and video conferencing to provide help. Intervention through context poor media, such as email, is much less likely to succeed. Effective managerial intervention involving interaction with each party can lead to reframing the conflict into an opportunity to cooperate and find mutually beneficial solutions. The manager can present information, ask questions, and help the parties see that resolution is possible by addressing key issues such as the relative importance of the consequences, the potential win-win nature of the solution, each party's sense of victimization, and the certainty of continued interaction in the relationship.

The Effects of Different Computational Domain and Several Key Issues on CFD Simulated Results for Centrifugal Pumps

2011 ◽  
Author(s):  
Liang Dong ◽  
Hou-lin Liu ◽  
Ming-gao Tan ◽  
Yong Wang ◽  
Kai Wang
Keyword(s):  
Kinetic Energy ◽  
Velocity Distribution ◽  
Turbulent Kinetic Energy ◽  
Prediction Accuracy ◽  
Cfd Simulation ◽  
Chamber Wall ◽  
Computational Domain ◽  
Centrifugal Pumps ◽  
Study Results ◽  
Key Issues

The computational domain is one of the major factors inducing CFD uncertainty. The effects of different computational domains and several key issues on CFD simulation results for centrifugal pumps are studied, such as the effects of modeling methods and boundary conditions on the whole computational domain numerical simulation. The study results indicate that the prediction accuracy of the whole computational domain is higher than that of the non-whole computational domain. The velocity distribution obtained by the whole computational domain in the gap between the impeller and volute is significantly layered, while the distribution obtained by the non-whole computational domain is triangular. The relative velocity distribution in the impeller and the turbulent kinetic energy in the volute for the two computational domains are obviously different, too. The number of the interfaces has little impact on the prediction accuracy. The rotational attribute of the chamber wall has a little effect on velocity and turbulent kinetic energy distribution, but the rotational attribute of the chamber wall can significantly improve the prediction accuracy of efficiency.

Energetics of Magnetosphere-Ionosphere system during Main Phase of Intense Geomagnetic Storms over three Solar Cycles

2018 ◽  
Vol 13 (S340) ◽  
pp. 69-70
Author(s):  
K. J. Suji ◽  
P. R. Prince
Keyword(s):  
Solar Wind ◽  
Kinetic Energy ◽  
Wind Energy ◽  
Joule Heating ◽  
Geomagnetic Storms ◽  
Main Phase ◽  
Relative Importance ◽  
Solar Cycles ◽  
Dynamo Action ◽  
Solar Wind Energy

AbstractSolar wind kinetic energy gets transferred into the Earth’s magnetosphere as a result of dynamo action between magnetosphere and solar wind. Energy is then dissipated among various dissipation channels in the MI system. In the present study, energetics of 59 intense geomagnetic storms are analyzed for the period between 1986 and 2015, which covers the three consecutive solar cycles SC 22, 23 and 24. The average solar wind energy impinging the MI system is estimated using Epsilon parameter, the coupling function. Moreover, the relative importance of different energy sinks in the MI system are quantified and is found that more than 60% of solar wind energy is dissipated in the form of ionospheric Joule heating.

Some observations on the ion–molecule reactions in ethylene

1968 ◽  
Vol 46 (2) ◽  
pp. 101-109 ◽  
Author(s):  
J. J. Myher ◽  
A. G. Harrison
Keyword(s):  
Kinetic Energy ◽  
Ground State ◽  
Relative Importance ◽  
Collision Complex ◽  
Ion Molecule Reactions ◽  
Secondary Ions ◽  
Secondary Ion

The ion–molecule reactions in ethylene have been studied under conditions where C2H4+ was the only primary ion. In addition to the expected secondary ions C3H5+ and C4H7+, the C3H4+, C2H2+, and C2H3+ ions have been detected, presumably formed by the reactions[Formula: see text]Reactions [b] and [c] are endothermic for ground state reactants and it has been shown that the kinetic energy of the reactant ion plays a major role in determining the relative importance of these endothermic reactions.The C5H9+ ion has been shown to originate by further reaction of the C3H5+ secondary ion rather than by reaction of the (C4H8+)* collision complex. The reversion of the (C4H8+)* complex to reactants has been confirmed by the observation of isotopically mixed ethylene ions in C2H4–C2D4 mixtures.

Energy and Exergy Analyses of the Pulse Detonation Engine

2003 ◽  
Vol 125 (4) ◽  
pp. 1075-1080 ◽  
Author(s):  
T. E. Hutchins ◽  
M. Metghalchi
Keyword(s):  
Gas Turbine ◽  
Constant Volume ◽  
Supersonic Combustion ◽  
Working Fluid ◽  
Pulse Detonation Engine ◽  
Pulse Detonation ◽  
Energy And Exergy ◽  
Efficiency And Effectiveness ◽  
Detonation Engine ◽  
Exergy Analyses

Energy and exergy analyses have been performed on a pulse detonation engine. A pulse detonation engine is a promising new engine, which uses a detonation wave instead of a deflagration wave for the combustion process. The high-speed supersonic combustion wave reduces overall combustion duration resulting in an nearly constant volume energy release process compared to the constant pressure process of gas turbine engines. Gas mixture in a pulse detonation engine has been modeled to execute the Humphrey cycle. The cycle includes four processes: isentropic compression, constant volume combustion, isentropic expansion, and isobaric compression. Working fluid is a fuel-air mixture for unburned gases and products of combustion for burned gases. Different fuels such as methane and JP10 have been used. It is assumed that burned gases are in chemical equilibrium states. Both thermal efficiency and effectiveness (exergetic efficiency) have been calculated for the pulse detonation engine and simple gas turbine engine. Comparison shows that for the same pressure ratio pulse detonation engine has better efficiency and effectiveness than the gas turbine system.

Flow Field Characteristics of Butterfly-Type Cavity and its Influence on Supersonic Flow

2011 ◽  
Vol 347-353 ◽  
pp. 2468-2474
Author(s):  
Jin Xiang Wu ◽  
Jing Ma ◽  
Xiang Gou ◽  
Lian Sheng Liu ◽  
En Yu Wang
Keyword(s):  
Energy Dissipation ◽  
Kinetic Energy ◽  
Combustion Chamber ◽  
Turbulent Kinetic Energy ◽  
Energy Dissipation Rate ◽  
Hydrogen Gas ◽  
Supersonic Combustion ◽  
Flow Field Characteristics ◽  
Cavity Configuration ◽  
New Type

A new type of cavity configuration — butterfly-type cavity applied in the scramjet is proposed in this paper. The supersonic combustion chamber with Butterfly-type cavity was investigated numerically and experimentally. Results show that the horizontal vortex moving along the Y direction is helpful in gathering hydrogen gas, but the vertical vortex moving along the Z direction is not. Both turbulent kinetic energy and turbulent kinetic energy dissipation rate are very high at the junction between the cavity and the main combustion chamber. And the production of turbulent kinetic energy is agreeable with that of turbulent kinetic energy dissipation.

scholarly journals The impact of scandal and inquiries on social work and the personal social services

Social Work ◽  
2020 ◽  
pp. 191-212
Author(s):  
Ray Jones
Keyword(s):  
Social Work ◽  
Social Services ◽  
Social Work Education ◽  
Public Image ◽  
Relative Importance ◽  
Key Issues ◽  
Programme Content ◽  
Work Education ◽  
The Impact ◽  
Discriminatory Practice

Following a summary of changes in the context of social work education in the last 50 years, the chapter discusses key issues which have shaped educational approaches: the nature of the profession; preparation for one role or for many; student selection and recruitment targets; where decision-making should lie; where responsibility for financing social work education should lie; and the relative importance in social work education of curriculum and programme content, underpinning of professional ethics and a focus on service users, education for anti-discriminatory practice and preparation for practice. Challenges now facing social work education are then discussed. Do higher education institutions and employers agree on what makes a good social worker? Can we and will we learn from evaluation? Are we sufficiently international? Among conclusions drawn are that social work still has a problem with its public image, that insufficient attention has been given to retaining social workers in practice by enabling quality relationship-based work to be practised under good supervision, and that it will be important to maintain programmes of initial education in strong research-based institutions.

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