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When uranium alloyed with 6-wt% niobium (U–6Nb) is rapidly compressed in uniaxial strain experiments, shear stress is observed to relax with a characteristic time of 30 ± 7 ns. In shock wave experiments, this relaxation inhibits the development of an elastic precursor commonly seen in other materials. When U–6Nb is cold-rolled to pre-twin and significantly increase the density of dislocations in the material, stress relaxation effects are diminished suggesting that twinning causes relaxation in the un-worked material. Separate ramp wave compression experiments produce effects that agree with those observed in shock-loading experiments. A phenomenological model is introduced that allows accurate simulation of all experiments. Estimates of residual shear stress after relaxation are obtained.

The chapter discusses the concept of a radial flow turbine that is used for producing hydraulic power. It discusses mainly two types of radial flow turbines—the inward flow radial flow (IFR) and outward flow gas turbines. The IFR turbine covers tremendous ranges of power, rates of mass flow, and rotational speeds, from very large outwards turbines used in hydroelectric power for the generation of hundreds of megawatts down to tiny closed cycle gas turbines for the space power generation of a few kilowatts. The IFR gas turbine continues to be used extensively for powering automotive turbo charges, aircraft auxiliary power units, and expansion units in gas liquefaction. Over a limited range of specific speed, IFR turbines provide efficiency about equal to that of the best axial-flow turbines. The significant advantages offered by the IFR turbine compared with the axial-flow turbine are the greater amount of work that can be obtained per stage, the ease of manufacture, and its superior ruggedness. Different types of inward turbines are also discussed in this chapter, along with the optimum design selection of IFR turbines including factors such as nozzle blade row boundary layers, rotor passage boundary layers, disc wind age, and kinetic energy loss at exit.

Publisher Summary The design and performance prediction of axial flow compressors and turbines has been based upon the measurements of the flow-through two-dimensional cascades of blades. For cascade analysis, the flow across individual blade rows is treated as two-dimensional and steady. This approach is appropriate for many compressor and turbine designs and the derived flow characteristics obtained from cascade tests have usually been found to be satisfactory, although laborious to collect. It is most important that the flow across the central region of the cascade blades is a good approximation to two-dimensional flow and that the flow repeats across several blade pitches. This effect could be achieved by employing a large number of long blades, but then an excessive amount of power would be required to operate the tunnel. A cascade blade profile can be conceived as a curved camber line upon which a profile thickness distribution is symmetrically superimposed. Cascade flow characteristics such as streamtube thickness variation, cascade performance parameters, and blade surface velocity distributions are discussed in the chapter. This also includes discussion on the compressor cascade performance, turbine cascade performance, and the analysis of cascade.

Publisher Summary This chapter focuses on the three-dimensional flow in axial turbomachinery. An analysis called the “radial equilibrium method,” widely used for three-dimensional design calculations in axial compressors and turbines, is based upon the assumption that any radial flow occurring is completed within a blade row. The radial equilibrium equation applies to compressible flow as well as incompressible flow. With constant stagnation enthalpy and constant entropy, a free-vortex flow, therefore, implies uniform axial velocity downstream of a blade row, regardless of any density changes incurred in passing through the blade row. The design problem (the tangential velocity distribution) with the axial velocity variation and the direct problem (the swirl angle distribution), with the axial and tangential velocities being determined, are specified in the chapter. It also includes an introduction to the subject of computational fluid dynamics that plays a large part in turbomachinery design and analysis. All the principles detailed in this chapter are equally applicable to the numerical and experimental studies of turbomachines. Radial turbomachinery remains hugely important for a vast number of applications such as turbo charging for internal combustion engines, oil and gas transportation, and air liquefaction. As jet engine cores become more compact, there is also the possibility of radial machines finding new uses within aerospace applications.

Publisher Summary This chapter discusses the elementary flow analysis and preliminary design of radial-flow work-absorbing turbomachines comprising pumps, low speed fans, and compressors. It focuses on the compressor because the basic action of all these machines is the same. Turbomachines employing centrifugal effects for increasing fluid pressure have been in use and the earliest machines using this method were hydraulic pumps followed later by ventilating fans and blowers. The axial flow compressors are found to be better in meeting the needs of larger engines. Not only are the frontal area (and drag) smaller with engines using axial compressors but also the efficiency for the same duty is better by as much as 3 or 4%.Many applications are found in small gas turbines for road vehicles and commercial helicopters as well as bigger applications, e.g., diesel engine turbochargers, chemical plant processes, factory workshop air supplies, large-scale air-conditioning plant, etc. The chapter discusses the details for calculating the performance of centrifugal compressors with backward swept impeller vanes and presents the thermodynamic analysis of the centrifugal compressor with the help of the impeller and diffuser. The diffuser is an important element of a compressor or pump. Its purpose is to reduce the velocity of the flow leaving the impeller resulting in an increase in pressure. The optimum design of the pump and compressor is presented in this chapter. It also evaluates the performance of the pump, fan, and compressor with the help of suitable examples.

Two experiments have been performed to measure the effects of pulsed radiation loads on the front of small tubular structures, using as an energy source the X-ray fluence produced by a Z-pinch at the Sandia National Laboratories Z Facility. The project had two major goals: to establish the feasibility of using the Z machine to study the phenomenology associated with debris generation and propagation down tubular structures with partitions; and to use the resultant experimental data to validate numerical hydrocodes (shock physics codes) so that we have confidence in their use in analyzing these types of situations. Two tubular aluminum structures (5 and 10 cm long and 1 cm inside diameter) were prepared, with aluminum partitions located at the front, halfway down the pipe, and at the rear. Interferometry (VISARs) provided multiple velocity histories for all of the partitions. In both experiments, the first barrier, which was exposed directly to the x-ray fluence, was launched into the pipe at a velocity of ∼2 km/s, accelerating to give a mean velocity of ∼2.6 km/s. Loss of plate integrity is inferred from the dispersed launch of the second partition at ∼1 km/s. Wall shocks propagating at 4.5 km/s were inferred. Post-test metallography showed evidence of melting and partial vaporization of the plates, and turbulent mixing with material from the walls. Calculations qualitatively agree with the observed results, but slightly overpredict debris velocity, possibly due to overestimates of total energy fluence. An application for this work is the study of techniques for line-of-sight shock and debris mitigation on high-power pulsed power facilities such as Z and its follow-on machines.

In this paper, we describe a new technique for using a pulsed power source (Z pinch) to produce planar shock waves for high-pressure equation of state (EOS) studies. Initial EOS experiments indicate that these sources are effective for shock wave studies in samples with diameters of a few millimeters and thicknesses of a fraction of one millimeter, and thus provide the possibility for achieving accuracy in shock and particle velocity measurements of a few percent. We have used the Z pinch source to produce the first in-situ time-resolve particle velocity profiles obtained with pulsed radiation sources in the Mbar regime. Particle velocity profiles obtained with a VISAR interferometer are compared with 1-D numerical simulations performed with a radiation-hydrodynamics code, ALEGRA. Good agreement with experimental results was achieved in the simulations and suggests that the Z pinch source should be a valuable tool for high-pressure EOS studies in thermodynamic regimes important to hypervelocity impact.

A series of controlled impact experiments has been performed to determine the shock loading and release behavior of two types of concrete, differentiated by aggregate size, but with average densities varying by less than 2 percent. Hugoniot stress and subsequent release data was collected over a range of approximately 3 to 25 GPa using a plate reverberation technique in combination with velocity interferometry. The results of the current data are compared to those obtained in previous studies on concrete with a different aggregate size but similar density. Results indicate that the average loading and release behavior are comparable for the three types of concrete discussed in this paper. Residual strain is also indicated from these measurements.

A systematic study is described which has led to the successful launch of thin flier plates to velocities of 16 km/s. The energy required to launch a flier plate to 16 km/s is approximately 10 to 15 times the energy required to melt and vaporize the plate. The energy must, therefore, be deposited in a well-controlled manner to prevent melt or vaporization. This is achieved by using a graded-density assembly to impact a stationary flier-plate. Upon impact, time-dependent, structured, high pressure pulses are generated and used to propel the plates to hypervelocities without melt or fracture. In previous studies, a graded-density impact of 7.3 km/s was used to launch a 0.5 mm thick plate to a velocity of over 12 km/s. If impact techniques alone were to be used to achieve flier-plate velocities approaching 16 km/s, this would require that the graded-density impact occur at - 10 km/s. In this paper, we describe a new technique that has been implemented to enhance the performance of the Sandia hypervelocity launcher. This technique of creating an impact-generated acceleration reservoir, has allowed the launch of 0.5 mm to 1.0 mm thick plates to record velocities up to 15.8 km/s. In these experiments, both titanium (Ti-6A1-4V) and aluminum (6061-T6) alloy were used for the flier-plate material. These are the highest metallic projectile plate velocities ever achieved for masses in the range of 0.1 g to 1 g.

Mathematical models for stamping of metal blanks are based upon the physical principles of equilibrium of forces, material constitutive laws and constraints resulting from contact between the blank and the press itself. We investigate singularities in the differential algebraic equation (DAE) resulting from one such model. In particular, the inability of numerical integrators to preserve anticipated symmetries in its solution as time advances is shown to be due to singularities on or close to the solution curve.

Recently, a numerical method was proposed for the solution of the equations of an incompressible fluid on a two dimensional grid consisting of Delaunay triangles. The method utilized the complementary grid of Voronoi polygons, as well as the dual variable reduction scheme developed by the authors. In this paper we generalize these ideas to thermally expandable, homogeneous, two-phase flow. This includes a derivation of the semi-discrete system, and the dual variable methodology that is used to solve it.

Experiments have been performed on NASA state-of-the-art hypervelocity impact shields using the Sandia Hypervelocity Launcher (HVL) to obtain test velocities greater than those achievable using conventional two stage light-gas sun technology. The objective of the tests was to provide the first experimental data on the advanced shielding concepts for evaluation of the analytical equations (shield performance predictors) at velocities previously unattainable in the laboratory, and for comparison to single Whipple Bumper Shileds (WBS) under similar loading conditions. The results indicate that significantly more mass is required on the back sheet of the WBS to stop an approximately flat-plate particle impacting at 7 km/sec and at 10 km/sec that the analytical equations (derived from spherical particle impact data) predicted. The Multi-Shock Shield (MSS) consists of four ceramic fabric bumpers, and is lighter in terms of areal density by up to 33%, but is as effective as the heavier WBS under similar impact conditions at about 10 km/s. The Mesh Double Bumper shield (MDB) consists of an aluminum wire mesh bumper, followed by a sheet of solid aluminum and a layer of Kevlar ® fabric. It provides a weight savings in terms of areal density of up to 35% compared to the WBS for impacts of around 10 km/s.

Publisher Summary The chapter discusses the concept of a radial flow turbine that is used for producing hydraulic power. It discusses mainly two types of radial flow turbines—the inward flow radial flow (IFR) and outward flow gas turbines. The IFR turbine covers tremendous ranges of power, rates of mass flow, and rotational speeds, from very large outwards turbines used in hydroelectric power for the generation of hundreds of megawatts down to tiny closed cycle gas turbines for the space power generation of a few kilowatts. The IFR gas turbine continues to be used extensively for powering automotive turbo charges, aircraft auxiliary power units, and expansion units in gas liquefaction. Over a limited range of specific speed, IFR turbines provide efficiency about equal to that of the best axial-flow turbines. The significant advantages offered by the IFR turbine compared with the axial-flow turbine are the greater amount of work that can be obtained per stage, the ease of manufacture, and its superior ruggedness. Different types of inward turbines are also discussed in this chapter, along with the optimum design selection of IFR turbines including factors such as nozzle blade row boundary layers, rotor passage boundary layers, disc wind age, and kinetic energy loss at exit.

Publisher Summary This chapter presents the basic characteristics of axial-flow compressors and ducted fans. It also covers the analysis of axial-flow compressors stage (mean-line analysis, velocity diagrams, thermodynamics, and stage loss relationships and efficiency) and axial-flow compressors rotors. Many axial compressors are multi-stage devices and repeating stages are initially assumed in which the velocity triangles for all stages are similar, the mean radius is constant, and the axial velocity through the machine is constant. The chapter covers the main preliminary design considerations such as stage loading, flow coefficient, reaction, inter-stage swirl, and blade aspect ratio. This includes a new presentation of the ways through which the measurements of cascade loss and turning can be translated into the performance of a compressor stage. Both incompressible and compressible cases are covered in the chapter and the huge importance of off-design performance is presented in detail including the ways a designer can influence compressor operating range during the very early design stages. For preliminary design and analysis purposes, a multi-stage compressor is thought of as a series of single-stage compressors, each performing as it would in isolation. However, to understand the performance of a real machine, the behavior of the overall system must be considered in more detail. This is particularly important to understand the sources of loss in a compressor and the off-design operation.

Publisher Summary The chapter emphasizes on the dimensional analysis and performance law associate with turbomachines. The widest comprehension of the general behavior of all turbomachines is obtained from dimensional analysis. Dimensional analysis applied to turbo machines has two uses—namely, prediction of a prototype's performance from the tests conducted on a scale model (similitude) and the determination of the most suitable type of machine on the basis of maximum efficiency, for a specified range of head, speed, and flow rate. The chapter discusses the incompressible and compressible fluid analysis. In case of incompressible fluid analysis, the performance of a turbo machine can be expressed in terms of the control variables, geometric variables, and fluid properties. The application of dimensional analysis to compressible flow increases the complexity of the functional relationships such as flow coefficient and stage loading. Performance characteristics for high speed machines such as compressor and turbines are also discussed in the chapter. A useful guide to the selection of the most appropriate type and size of compressor, pump or fan for a given duty and optimum efficiency is obtained by means of the cordier diagram.

Publisher Summary This chapter presents the basic thermodynamic and aerodynamic characteristics of axial-flow turbines. It covers the preliminary design and analysis of single- and multi-stage axial turbines. The main goal in the preliminary stage design of a turbine is to fix the shapes of the velocity triangles, either by setting the flow angles or by choosing values for the three dimensionless design parameters—φ, ψ, and R. A consideration of the ways the preliminary design choices affect the turbine basic layout and the efficiency can provide useful guidance to the designer .The development of the axial-flow turbine clearly depends upon the design advances made in the field of steam turbines. Three key non-dimensional parameters such as design flow coefficient, stage loading coefficient, and stage reaction are related to the shape of the turbine velocity triangles and are used in fixing the preliminary design of a turbine stage. The calculations needed to fix the size, the number of stages, the number of aerofoils in each blade row, and the velocity triangles are covered in the chapter. It covers the merits of different styles of turbine design including the implications for mechanical design such as centrifugal stress levels and cooling in high speed and high temperature turbines. Through the use of some relatively simple correlations, the trends in turbine efficiency with the main turbine parameters are also presented in the chapter.

The computer code ALGAE (ALgorithms for the GAs Equations) treats incompressible, thermally expandable or locally compressible flows in complicated two dimensional flow regions. The solution method, finite differencing schemes and basic modeling of the field equations in ALGAE is applicable to engineering design settings of the type found in Stirling cycle engines. This paper reports on the use of ALGAE to model multiple components of the Space Power Research Engine (SPRE). Video tape computer imulations of the transient behavior of the working gas 6elium) in the heater-regenerator-cooler complex of the SPRE demonstrate the usefulness of such a program in providing information on thermal and hydraulic phenomena in multiple component sections of the SPRE.

During the Engineering Design Activity (EDA) of the ITER program a major effort is being devoted to conductor R&D for the ITER magnets systems. This program includes all aspects of cable-in-conduit-conductor (CICC) manufacturing development such as superconducting strand, large multistage cables, and fabrication of thick-wall and thin-wall conduits. It also includes an extensive program of small scale laboratory measurements and experiments designed to predict the full-size conductor and magnet performance, and to quantify elements of the conductor design guidelines. A description of the manufacturing development and experimental program is given, including experiments for determining AC losses in the superconductor, CICC stability under BC and fast ramped conditions of field and current, and development of novel quench detection techniques.

An interactive computer program PLANIT is described which is useful in detecting anomalies in a finite element idealization of a three dimensional structure. Intersections of a sequence of planes with a catenation of brick elements are constructed and scanned with the aid of a graphics terminal.

Fabrication details, results of tests conducted, and areas for potential improvement in connection with the development of a hypervelocity electromagnetic launcher for equation of state (HELEOS) experiments are discussed. Common materials and fabrication technology are used in the manufacture of all components, and modular design allows for extending the length of the railgun as progress dictates. The launcher uses a 'vee block' geometry, which is designed to provide compressive preload, operate with a 300-MPa internal bore pressure, and easily accommodate interchangeable materials in the bore support structure and rail. Full-scale material testing of the railgun was performed, and a precision round-bore fabrication process was developed. Air-gage inspection is used to determine bore diameter and straightness. >

An interactive computer program STRSIT is described which generated contour plots of stresses in and normal to a specified plane intersecting a catenation of 20-node elements.

Equations and constitutive relations describing two-dimensional, thermally expandable, homogeneous, two-phase flow are presented and discussed. Four numerical solution methods of these equations are reviewed in detail. A fully and linearly implicit numerical method is developed that utilizes a dual variable transformation technique to substantially reduce the size of the matrix required for inversion at each time step. A computer code (DUVAL) incorporating this dual variable method is discussed, and preliminary numerical results are presented.