Radial Inflow Turbine Study.

The blades of turbocharger impellers are exposed to unsteady aerodynamic forces, which cause blade vibrations and may lead to failures. An indispensable requirement for a safe design of radial inflow turbines is a detailed knowledge of the exciting forces. Up to now, only few investigations relating to unsteady aerodynamic forces in radial turbines were presented. To give a detailed insight into the complex phenomena, a comprehensive research project was initiated at the Institut für Thermische Strömungsmaschinen, at the University of Karlsruhe. A turbocharger test rig was installed in the high pressure, high temperature laboratory of the institute. The present paper gives a description of the test rig design and the measuring techniques. The flow field in a vaneless radial inflow turbine was analyzed using laser Doppler anemometry. First results of unsteady flow field investigations in the turbine scroll and unsteady phase resolved measurements of the flow field in the turbine rotor will be discussed. Moreover, results from finite element calculations analyzing frequencies and mode shapes are presented. As vibrations in turbines of turbochargers are assumed to be predominantly excited by unsteady aerodynamic forces, a method to predict the actual transient flow in a radial turbine utilizing the commercial Navier Stokes solver TASCflow3d was developed. Results of the unsteady calculations are presented and comparisons with the measured unsteady flow field are made. As a major result, the excitation effect of the tongue region in a vaneless radial inflow turbine can be demonstrated.

Microturbines are small gas turbines that have the capacity range of 25-300 kW. The main components of microturbine are compressor, turbine, combustor and recuperator. This research paper focuses on the design of radial inflow turbine that operates in 30 kW microturbine. In order to operate the 30 kW microturbine with the back work ratio of 0.5, the radial inflow turbine should be designed to produce power at 60 kW. With the help of theory of turbo-machinery and the analytical methods, the design parameters are derived. The design results are constructed in 3D geometry. The 3D fluid-geometry is validated by computational fluid dynamics (CFD) simulation. The simulation results show the airflow path, the temperature distribution, the pressure distribution and Mach number. According to the simulation results, there is no flow blockage between vanes and no shock flow occurs in the designed turbine.

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Microturbines have been developed as an important power unit for distributed generation (DG) or distributed energy resource (DER) options [1]. They have been established and are widely used in aircraft and power applications, due to their easy installation, reliability, high performance, multi-fuel capabilities and low emission [2]. However, the aerothermodynamic design of a radial turbine still poses a challenge due to its high rotational speed and high inlet temperature, which influence the centrifugal stress and the rotor structural integrity. This paper presents the numerical investigations on the aerothermodynamic design of the nozzle and the radial inflow rotor for a 600 kW simple cycle gas turbine engine using a One-dimensional Computer FORTRAN Code (OFC) [3], on the grounds of non-dimensional parameters aimed at computational and work time reduction. This program utilizes a one-dimensional solution of flow conditions through the turbine along the meanline. The referred computer program is an effective performance prediction tool mostly in the initial stage of the preliminary design and can be used to quickly investigate and calculate the number of design options prior to any details of the vane and blade geometry. In order to find the most promising design option, a computational fluid dynamics (CFD) simulation has been used to study the performance, the aerothermodynamic design and the flow characteristics of the turbine components. The OFC results were compared with the CFD simulation, a computer program for the design analysis of radial inflow turbines, and analytical results taken from specialized literature showed the results were in agreement.

Cycles using supercritical carbon dioxide have been recognized as potential future power technology. However, the turbines in these systems tend to experience very high rotational speeds and entail small physical sizes, which can affect on the overall feasibility. One turbine type having potential to overcome some of the described challenges is the radial outflow turbine. However, its use in supercritical carbon dioxide power systems has not yet been extensively studied since typically axial or radial inflow turbines are considered instead. In this paper, the design of radial-outflow turbines with supercritical carbon dioxide is carried out and the results are compared to the respective radial inflow turbine designs. The analysis was carried out with turbine inlet temperature of 600 °C, inlet pressure of 200 bar and outlet pressure of 78 bar. Designs with four mass flow rates were investigated to study the effect of the power scale on the turbine design and losses. The geometry, efficiency, rotor stress and axial force were defined and analyzed for each design case. The results show that both the investigated turbine types can reach high isentropic efficiencies ranging from about 85% to over 90%. The radial outflow turbines can reach high efficiencies at wider specific speed range whereas the efficiency of radial inflow turbine is reduced more steeply, as the design speed is changed from its optimal value. Radial outflow turbines also reach high efficiencies with lower design speeds and that can be considered advantageous, since it helps to reduce the challenges related to turbomachinery rotordynamic and mechanical design. As a conclusion of the study, it is suggested that the use of radial outflow turbines can increase the feasibility of supercritical carbon dioxide power systems at the examined power scales.

According to the flow condition of the nuclear turbine, we can divide the turbine into the radial inflow turbine and axial inflow turbine. The radial flow turbine refers to the turbine steam where the steam or the vapor flows along the radial center. The radial machine has much greater work performance. Because the steam has to overcome the centrifugal force which increases its work ability. Currently, the radial inflow turbine is widely used in small unit and super low temperature engineering. In the state of global warming and the lack of energy, the radial inflow turbine performs well since it has a lot of advantages. This paper mainly introduces the process of the thermal design of a radial inflow turbine. One of the most important task is to determine the basic thermodynamic process and the selection of various parameters of the radial inflow turbine. We will apply the computer programming language C# to compile it. The thermodynamic process design uses IAPWS-IF97 formula to compute physical parameters of the vapor. Then we will finish the development of the software.

A comprehensive one-dimensional meanline design approach for radial inflow turbines is described in the present work. An original code was developed in Python that takes a novel approach to the automatic selection of feasible machines based on pre-defined performance or geometry characteristics for a given application. It comprises a brute-force search algorithm that traverses the entire search space based on key non-dimensional parameters and rotational speed. In this study, an in-depth analysis and subsequent implementation of relevant loss models as well as selection criteria for radial inflow turbines is addressed. Comparison with previously published designs, as well as other available codes, showed good agreement. Sample (real and theoretical) test cases were trialed and results showed good agreement when compared to other available codes. The presented approach was found to be valid and the model was found to be a useful tool with regards to the preliminary design and performance estimation of radial inflow turbines, enabling its integration with other thermodynamic cycle analysis and three-dimensional blade design codes.

Turbine optimization potential to improve automotive Rankine cycle performance

The use of supercritical fluids has been identified as potential solution in realizing highly efficient and compact sized power systems. In this study, the effect of design power scale and specific speed on supercritical CO2 operated radial inflow turbines within the power range of 0.1 MW–3.5 MW is investigated and analyzed. A radial turbine design tool including loss distribution analysis based on loss correlations was developed. In general, the SCO2 radial turbines can be designed to have high efficiency with efficiency ranging from over 80%–87% depending on the turbine design power scale. On the other hand, the turbine dimensions are small and the required rotational speeds are significantly high even at MW scale designs. It was observed that the specific speed and mass flow rate highly affect both the geometry and the turbine loss distribution. Turbine designs with highest isentropic efficiencies were observed with specific speeds ranging from 0.50 to 0.60. With the lowest investigated turbine power outputs from 100 kW to few hundreds of kW the tip clearance loss is the most significant loss whereas the passage, stator and exit kinetic loss are the most significant loss sources at higher power levels.

Preliminary design and CFD analysis of a radial inflow turbine and the turbine seal for an organic Rankine cycle using zeotropic mixture

Expounding on the results of the author's work with the US Army Research Office, DARPA, the Office of Naval Research, and various defense industry contractors, Governing Lethal Behavior in Autonomous Robots explores how to produce an "artificial conscience" in a new class of robots, humane-oids, which are robots that can potentially perform more et

Jagdish Chandra (ed) 1984 Philadelphia: Siam viii + 191 pp price £23.80 ISBN 0 89871 052 9 Chaotic motion is the pseudo-random behaviour of systems governed by deterministic classical equations of motion. Nonlinear dynamics and associated chaotic motion have attracted much research interest in recent years, particularly because the results are applicable to a wide range of problems in science and engineering.

Addition of fillers to polymers has long been used as a strategy to enhance the properties of polymers. In the last two decades, however, a class of materials termed as "polymer nanocomposites" (PNC) has evolved to refer to blends of polymers and inorganic fillers in which the inorganic component has one or more dimensions below 100 nm.1-3 Examples of such materials include mixtures of a variety of homopolymers and multicomponent polymers blended with fillers such as clays, nanotubes, Fullerenes, polyhedral oligomeric silsesquioxanes (POSS), nanoscopic silica particles, and so forth.2-7 Initial interest and research in such materials arose from the significant property enhancements reported for extremely low loadings of nanofillers. These reports fueled intense research into the mechanical, electrical, barrier, and fire retardancy properties of PNCs and have led to some notable commercial technologies utilizing PNCs.1, 8-10 More recent efforts have expanded the above class of studies and materials by examining the properties of nanocomposites involving polymer blends and block copolymers, where the potential to create multifunctional materials possessing novel electrical, magnetic, and optical properties have been reported.11, 12 However, despite the scale of intense research on PNCs, much of the initial promise of PNCs has not yet borne out. In this viewpoint article, I present an (admittedly) personal perspective of some of the issues confronting the field of PNCs, focusing especially on the opportunities by which theory, modeling, and computer simulations from polymer physics may aid in realizing the full potential of PNCs. Many of the common nanofillers used in PNCs are unfortunately characterized by strong van der waals interparticle attractions, which promote their agglomeration.13 Moreover, the effective interactions between nanofillers are also influenced by the polymer-filler interactions, and if the latter are unfavorable, it leads to conditions conducive to the aggregation of the fillers. Aggregation and clustering of the fillers typically leads to a significant reduction in the interfacial contact between the fillers and the polymer and hence a deterioration of the property enhancements that can be attained in PNCs. Consequently, achieving stable, dispersed configurations of nanofillers in the polymer matrix is a prime requirement to realize the full property potential of PNCs. Many experimental strategies have been explo-red to overcome the above challenge.14 These have ranged from using polymer-filler combinations, which are known to exhibit favorable affinities to functionalizing the fillers by self-assembling surfactant and grafting polymers to promote favorable polymer-filler interactions (and provide a steric barrier against agglomeration). Also, successful strategies using external fields to promote nonequilibrium dispersion of the nanofiller have been demonstrated.15 From a theoretical perspective, the outstanding question confronting the design of such strategies is "For specified combination of matrix polymer(s), filler(s), the functionalizing moieties and/or external fields, can we predict the equilibrium and nonequilibrium structural characteristics of the PNC dispersion?" Anisotropy of fillers: Most of the PNCs explored for applications involve filler particles such as clays, carbon nanotubes, nanofibers, and so forth, which exhibit considerable shape anisotropy. Indeed, such fillers prove most suitable for exploiting significant polymer-filler interfacial contact at even extremely low loadings of the filler. In contrast, very few of the aforementioned theories and simulations deal with the phase behavior and structure of mixtures of anisotropic fillers dispersed in single and multicomponent polymers.27-29 The rich literature of colloidal physics suggests that the equilibrium characteristics of anisotropic colloids can be expected to be significantly different and richer compared with their isotropic counterparts.30 Moreover, situations combining anisotropic fillers with multicomponent polymers such as block copolymers can be expected to reveal a rich interplay between polymer self-assembly and colloidal phase behavior. It will be of significant interest to PNC research to translate some of the theoretical advances achieved in the context of spherical fillers to the corresponding situations involving anisotropic fillers. Role of Functionalization: As mentioned earlier, functionalization of the fillers is a common strategy to overcome the issue of agglomeration of fillers. However, in much of the existing theories, the role of functionalization is treated either empirically as a modified polymer-filler interaction18, 23 or in more detailed formalism as a modification of the effective polymer-mediated potentials between the fillers. The first approach can be deemed reasonable for small oligomeric or surfactant-like functionalizers, but suffers from the drawback that it leaves open the question of the relationship between the polymer-filler interaction and the physicochemical properties of the functionalizing group. The second approach has typically been effected for the situation of grafted polymer functionalizers.31 It is, however, a pairwise interaction approach that works only for the homogeneous phase of the polymer matrix and in addition neglects multibody effects, which may become important when either long grafting polymers or higher concentrations of fillers are used. Overall, it would be desirable to develop a suite of simulations and/or modeling tools that, similar to the nongrafted case, can obviate such assumptions while still being able to predict the structure of the PNC dispersion. Structure under nonequilibrium and external field conditions: Despite the best experimental strategies, nonequilibrium effects resulting from filler aggregation and/or external fields are bound to remain important for many applications of PNCs, especially for situations involving anisotropic fillers. Some unresolved questions include: "How does the structure of a PNC dispersion evolve upon dispersing the fillers in the polymer matrix?," "Can quantities such as the fractal dimension and cluster size distributions be predicted for specified polymer-filler combinations?," "How does externally applied shear, electric, and magnetic fields (and combinations thereof) impact upon the nonequilibrium state of the dispersion?" Although computer simulations may shed light on some of the relevant issues, the time and length scales, which can be probed by such means may not necessarily overlap with experimental regimes, and there is a need for development of appropriate theoretical models to address pertinent issues. There have been some notable theoretical advances in this regard in the context of colloidal science,32, 33 and a preliminary assessment of their applicability to the field of PNCs would be extremely beneficial. However, issues unique to PNCs, such as the significant anisotropy of the fillers, potentially long-ranged interparticle interactions (mediated by the polymers), the dynamical and rheological response of the polymer matrix, are expected to prove important and provide fertile and challenging areas for theoretical research. Detailed structural characteristics: Many experimental studies of the mechanical, electrical, and rheological behavior of PNCs have suggested an intimate connection between enhanced macroscopic properties and the percolation behavior of the fillers.10, 34-36 Although such features can be directly extracted in computer simulations, existing theoretical frameworks mostly concern with the phase behavior and/or structural features at a pair correlation level. It may be of interest to the PNC experimental community to develop a theoretical framework, which can predict the the influence of different interactions, functionalization, and external fields upon more detailed structural characteristics such as the percolation characteristics37, 38 fractal and cluster dimensions of the fillers in the polymer matrix. Connection to atomistic details: Much of the above discussion focused on some open questions in the context of structure of PNCs as examined from a "coarse-grained" polymer physics perspective. Although such efforts are valuable for providing design guidelines, deducing mechanistic underpinnings and suggesting new experimental strategies, questions involving the detailed chemistry of the filler, polymer and functional groups cannot typically be answered in such frameworks. This situation is compounded by the fact that much of the coarse-grained modeling of PNCs use potentials and interaction parameters, which cannot also be directly determined from experimental measurements. The latter contrasts with the analogous situation in multicomponent polymer melts and solutions where experimental solubility measurements provide direct information on the parameters used in the corresponding coarse-grained theories.39 Addressing this shortcoming in the context of PNCs requires the development of efficient computer simulation tools and methodologies, which can render the connection between the chemistry of the components and the coarse-grained parameters more quantitative. The research field of "coarse-graining methodologies" is undergoing intense development in the context of simple and polymeric fluids.40-42 Although some notable "multiscale" efforts have also occurred in the context of PNCs,43, 44 much work remains to be done in surmounting the time, length scale challenges accompanying the interactions, structure, and properties of PNCs. Detailed structural information: Much of the aforementioned macroscopic theories were developed for model structural representations such as random or completely aligned dispersions while ignoring PNC specific features such as aggregation and/or complex structural arrangement of the fillers. Consequently, it is not surprising that such ideal models cannot quantitatively predict the properties of PNCs. One potential area for future research is the development of macroscopic models capable of accommodating detailed structural information, such as experimentally obtainable pair correlation functions of the fillers or cluster sizes and fractal dimension of aggregates, while rendering quantitative predictions regarding the macroscopic properties of PNCs. This area has recently seen some notable advances, especially arising from numerical continuum mechanical approaches.47-49 It may be envisioned that the results of such efforts can be used to guide the refinement of classical models to accommodate the PNC specific features. Interfacial effects: An important feature that distinguishes PNCs from traditional composites is the presence of significant amounts of polymer-filler interfaces and its influence upon the macroscopic properties. To highlight the resulting issues, I point out the status with respect to the "simpler" situation of polymer films supported on a solid substrate. In such contexts, experiments have clearly demonstrated that the polymer-surface interactions can lead to properties for the polymer layer, which are in general markedly different from that of the bulk polymeric material.50 Moreover, for properties such as glass transition temperatures,51 aging dynamics,52, 53 and elastic moduli,54 the interfacial effects have been shown to persist to extremely long length scales relative to the physical dimensions of the polymer. In the context of properties that exhibit only a short ranged interfacial effects (such as solubility of penetrants and mechanical properties), the aforementioned approaches may suffice to accommodate the influence of polymer-filler interfaces upon macroscopic properties. However, to endow a predictive value to theories, quantitative connections between the physicochemical polymer-filler interactions and the properties of the interfacial layer (or the parameters in the boundary conditions) in such models needs to be established. Although computer simulations may aid in this effort, in many cases, new formalisms may be necessary to discern quantities such as "local" mechanical properties,55 "local" conductivities, "local" penetrant diffusivities, and so forth, in such efforts. Once the connections between polymer-filler interactions and the interfacial properties are firmly established, "homogenization theories" similar to that used for the macroscopic properties of composites and dispersed media may be pursued. However, such approaches still need to be augmented to account for the possibility of complex structural arrangement of the fillers (an issue discussed earlier) and the overlap of interfacial layers which may consequently arise. As discussed earlier, some interfacial properties (such as the glass transition temperatures) are known to display long ranged variations influenced by the surface of the fillers, and in such cases, boundary condition and/or three-phase model approaches are likely to prove inadequate for capturing the influence of polymer-filler interfaces upon the macroscopic properties of the system. Refining the existing models to account for such properties represents an extremely challenging task, because in many cases there is a lack of understanding of the physics underlying such long ranged variations in polymer thin films. Moving to PNCs brings even more complications, such as the possibility for overlap of interfacial layers arising from different particles (such overlaps become very likely for long-ranged effects), leading to significant multibody interaction effects. Overall, this is an area for which the directions of theoretical modeling are far less clear (to me), suggesting that radically new ideas may be necessary to make progress in understanding and predicting the properties of polymer thin films and PNCs. The above represents an opinionated selection of some of the open questions confronting theoretical modeling of polymer nanocomposite systems. While active research is in progress in a number of the above-mentioned areas, successful fruition in many of the issues requires a confluence of ideas from different fields, viz., colloid and polymer physics, statistical and continuum mechanics, modeling and simulation approaches, and most importantly, experiments and theories. While technology and experiments are likely to provide more focus to the issues and theoretical efforts, progress in the above delineated issues is expected to have significant fundamental implications for many related areas of polymer and colloidal science, and may also potentially lead to uses and applications of PNCs above and beyond what has been realized or even dreamed about. This research program on polymer nanocomposites has been graciously supported by research grants from the National Science Foundation, American Chemical Society, Air Force Research Laboratories, Robert A. Welch Foundation, and the US Army Research Office under grant W911NF-07-1-0268. The author thanks Dr. Victor Pryamitsyn for useful comments which helped to shape the ideas expressed in this viewpoint. The author also acknowledges Profs. Glenn Fredrickson, Kenneth Schweizer, John Torkelson, Peter Green, Donald Paul, Jack Douglas, Sanat Kumar, Richard Vaia, and Ramanan Krishnamoorti for many discussions over the years while patiently educating him on the issues in polymer nanocomposites.

: US Army Research Office has funded this 2-year basic research effort by ICx-Agentase to study new techniques of modifying native enzymes with polymers via atom transfer radical polymerization to increase their solubility and utility in organic solvents and to increase their stability in body. Protein-initiated ATRP would enable us to overcome many problems in conventional technology that modifies proteins with polyethylene glycol or pegylation. These problems include lack of control on number of polymer chains attached per protein, low yield, tedious purifications, and less-than-optimal stabilization. The first goal of this study is to develop new technique/s to modify enzymes with hydrophobic polymers and dissolve high concentrations of modified enzymes in organic solvent and apply them in self decontaminating paints and coatings. The second goal of the study was to study the potential of using of ATRP modified proteins for therapeutic applications in vivo. Chymotrypsin and BChE conjugates synthesized by ATRP were demonstrated and were highly active and much more stable in mouse serum as compared to conventionally pegylated enzymes.

The catalyst layer used in a fuel cell is an archetype of multi-component composite materials used as electrodes in many electrochemical devices. In this talk, we will describe and link together a number of studies of the fuel cell catalyst layer that we have been carried out over the past 10 to 15 years. The first of these was a modeling effort that was initially carried out to describe the geometrically constrained limits on utilization of dispersed catalyst in the layer. To answer our original question, the catalyst components were broken down to constituents (Pt nanoparticles, carbon particles, ionomer) and interactions between components were used to build a hierarchical model of the catalyst layer. The interactions were defined in the context of colloidal interaction theory using descriptions of electronic properties of the constituents derived from experimental measurements of refractive index/dielectric properties across a wide range of frequencies. The model satisfactorily captured some aspects of the structure of the catalyst layer, e.g. the tendency toward segregation of components, and provides a good bound to the utilization of catalysts but failed to provide a quantitatively accurate description of certain transport-related physical properties. In the next phase of the work, the connectivity of ionomer in the catalyst layer was probed using NMR relaxation and diffusion measurements on water in the catalyst layer as a function of water content. Finally, a detailed study of the distribution of components within the catalyst layer, the catalyst layer porosity and the adsorption of ionomer in catalyst layers, all as functions of composition, was undertaken. These three chapters of work correspond to three different probes usng models and experiments of many types to yield a more nuanced picture of the catalyst layer. Future prospects and needs will be presented in the context of still-missing information and where we might look for it. Acknowledgement We gratefully acknowledge the support of this work by the US Army Research Office and the Naval Research Research Office. The significant contributions of Professor J. Adin Mann of Case Western Reserve university and Dr. Karren More of Oak Ridge National Lab are also appreciated.