An interactive grid generation procedure for axial and radial flow turbomachinery

A combination algebraic/elliptic technique is presented for the generation of three dimensional grids about turbo-machinery blade rows for both axial and radial flow machinery. The technique is built around use of an advanced engineering workstation to construct several two dimensional grids interactively on predetermined blade-to-blade surfaces. A three dimensional grid is generated by interpolating these surface grids onto an axisymmetric grid. On each blade-to-blade surface, a grid is created using algebraic techniques near the blade to control orthogonality within the boundary layer region and elliptic techniques in the mid-passage to achieve smoothness. The interactive definition of bezier curves as internal boundaries is the key to simple construction. This procedure lends itself well to zonal grid construction, an important example being the tip clearance region. Calculations done to date include a space shuttle main engine turbopump blade, a radial inflow turbine blade, and the first stator of the United Technologies Research Center large scale rotating rig. A finite Navier-Stokes solver was used in each case

An analysis of the viscous flow through a compact radial turbine by the average passage approach

A steady, three-dimensional viscous average passage computer code is used to analyze the flow through a compact radial turbine rotor. The code models the flow as spatially periodic from blade passage to blade passage. Results from the code using varying computational models are compared with each other and with experimental data. These results include blade surface velocities and pressures, exit vorticity and entropy contour plots, shroud pressures, and spanwise exit total temperature, total pressure, and swirl distributions. The three computational models used are inviscid, viscous with no blade clearance, and viscous with blade clearance. It is found that modeling viscous effects improves correlation with experimental data, while modeling hub and tip clearances further improves some comparisons. Experimental results such as a local maximum of exit swirl, reduced exit total pressures at the walls, and exit total temperature magnitudes are explained by interpretation of the flow physics and computed secondary flows. Trends in the computed blade loading diagrams are similarly explained

Progress of High Efficiency Centrifugal Compressor Simulations Using TURBO

Three-dimensional, time-accurate, and phase-lagged computational fluid dynamics (CFD) simulations of the High Efficiency Centrifugal Compressor (HECC) stage were generated using the TURBO solver. Changes to the TURBO Parallel Version 4 source code were made in order to properly model the no-slip boundary condition along the spinning hub region for centrifugal impellers. A startup procedure was developed to generate a converged flow field in TURBO. This procedure initialized computations on a coarsened mesh generated by the Turbomachinery Gridding System (TGS) and relied on a method of systematically increasing wheel speed and backpressure. Baseline design-speed TURBO results generally overpredicted total pressure ratio, adiabatic efficiency, and the choking flow rate of the HECC stage as compared with the design-intent CFD results of Code Leo. Including diffuser fillet geometry in the TURBO computation resulted in a 0.6 percent reduction in the choking flow rate and led to a better match with design-intent CFD. Diffuser fillets reduced annulus cross-sectional area but also reduced corner separation, and thus blockage, in the diffuser passage. It was found that the TURBO computations are somewhat insensitive to inlet total pressure changing from the TURBO default inlet pressure of 14.7 pounds per square inch (101.35 kilopascals) down to 11.0 pounds per square inch (75.83 kilopascals), the inlet pressure of the component test. Off-design tip clearance was modeled in TURBO in two computations: one in which the blade tip geometry was trimmed by 12 mils (0.3048 millimeters), and another in which the hub flow path was moved to reflect a 12-mil axial shift in the impeller hub, creating a step at the hub. The one-dimensional results of these two computations indicate non-negligible differences between the two modeling approaches

Computational Study of the CC3 Impeller and Vaneless Diffuser Experiment

Centrifugal compressors are compatible with the low exit corrected flows found in the high pressure compressor of turboshaft engines and may play an increasing role in turbofan engines as engine overall pressure ratios increase. Centrifugal compressor stages are difficult to model accurately with RANS CFD solvers. A computational study of the CC3 centrifugal impeller in its vaneless diffuser configuration was undertaken as part of an effort to understand potential causes of RANS CFD mis-prediction in these types of geometries. Three steady, periodic cases of the impeller and diffuser were modeled using the TURBO Parallel Version 4 code: (1) a k- turbulence model computation on a 6.8 million point grid using wall functions, (2) a k- turbulence model computation on a 14 million point grid integrating to the wall, and (3) a k- turbulence model computation on the 14 million point grid integrating to the wall. It was found that all three cases compared favorably to data from inlet to impeller trailing edge, but the k- and k- computations had disparate results beyond the trailing edge and into the vaneless diffuser. A large region of reversed flow was observed in the k- computations which extended from 70 to 100 percent span at the exit rating plane, whereas the k- computation had reversed flow from 95 to 100 percent span. Compared to experimental data at near-peak-efficiency, the reversed flow region in the k- case resulted in an underprediction in adiabatic efficiency of 8.3 points, whereas the k- case was 1.2 points lower in efficiency

Computational Assessment of a 3-Stage Axial Compressor Which Provides Airflow to the NASA 11- by 11-Foot Transonic Wind Tunnel, Including Design Changes for Increased Performance

A 24 foot diameter 3-stage axial compressor powered by variable-speed induction motors provides the airflow in the closed-return 11- by 11-Foot Transonic Wind Tunnel (11-Foot TWT) Facility at NASA Ames Research Center at Moffett Field, California. The facility is part of the Unitary Plan Wind Tunnel, which was completed in 1955. Since then, upgrades made to the 11-Foot TWT such as flow conditioning devices and instrumentation have increased blockage and pressure loss in the tunnel, somewhat reducing the peak Mach number capability of the test section. Due to erosion effects on the existing aluminum alloy rotor blades, fabrication of new steel rotor blades is planned. This presents an opportunity to increase the Mach number capability of the tunnel by redesigning the compressor for increased pressure ratio. Challenging design constraints exist for any proposed design, demanding the use of the existing driveline, rotor disks, stator vanes, and hub and casing flow paths, so as to minimize cost and installation time. The current effort was undertaken to characterize the performance of the existing compressor design using available design tools and computational fluid dynamics (CFD) codes and subsequently recommend a new compressor design to achieve higher pressure ratio, which directly correlates with increased test section Mach number. The constant cross-sectional area of the compressor leads to highly diffusion factors, which presents a challenge in simulating the existing design. The CFD code APNASA was used to simulate the aerodynamic performance of the existing compressor. The simulations were compared to performance predictions from the HT0300 turbomachinery design and analysis code, and to compressor performance data taken during a 1997 facility test. It was found that the CFD simulations were sensitive to endwall leakages associated with stator buttons, and to a lesser degree, under-stator-platform flow recirculation at the hub. When stator button leakages were modeled, pumping capability increased by over 20 of pressure rise at design point due to a large reduction in aerodynamic blockage at the hub. Incorporating the stator button leakages was crucial to matching test data. Under-stator-platform flow recirculation was thought to be large due to a lack of seals. The effect of this recirculation was assessed with APNASA simulations recirculating 0.5, 1, and 2 of inlet flow about stators 1 and 2, modeled as axisymmetric mass flux boundary conditions on the hub before and after the vanes. The injection of flow ahead of the stators tended to re-energize the boundary layer and reduce hub separations, resulting in about 3 increased stall margin per 1 of inlet flow recirculated. In order to assess the value of the flow recirculation, a mixing plane simulation of the compressor which gridded the under-stator cavities was generated using the ADPAC CFD code. This simulation indicated that about 0.65 of the inlet flow is recirculated around each shrouded stator. This collective information was applied during the redesign of the compressor. A potential design was identified using HT0300 which improved overall pressure ratio by removing pre-swirl into rotor 1, replacing existing NASA 65 series rotors with double circular arc sections, and re-staggering rotors and the existing stators. The performance of the new design predicted by APNASA and HT0300 is compared to the existing design

Mechanism of succinate efflux upon reperfusion of the ischaemic heart.

AIMS: Succinate accumulates several-fold in the ischaemic heart and is then rapidly oxidized upon reperfusion, contributing to reactive oxygen species production by mitochondria. In addition, a significant amount of the accumulated succinate is released from the heart into the circulation at reperfusion, potentially activating the G-protein-coupled succinate receptor (SUCNR1). However, the factors that determine the proportion of succinate oxidation or release, and the mechanism of this release, are not known. METHODS AND RESULTS: To address these questions, we assessed the fate of accumulated succinate upon reperfusion of anoxic cardiomyocytes, and of the ischaemic heart both ex vivo and in vivo. The release of accumulated succinate was selective and was enhanced by acidification of the intracellular milieu. Furthermore, pharmacological inhibition, or haploinsufficiency of the monocarboxylate transporter 1 (MCT1) significantly decreased succinate efflux from the reperfused heart. CONCLUSION: Succinate release upon reperfusion of the ischaemic heart is mediated by MCT1 and is facilitated by the acidification of the myocardium during ischaemia. These findings will allow the signalling interaction between succinate released from reperfused ischaemic myocardium and SUCNR1 to be explored

RAGE Mediates a Novel Proinflammatory Axis A Central Cell Surface Receptor for S100/Calgranulin Polypeptides

AbstractS100/calgranulin polypeptides are present at sites of inflammation, likely released by inflammatory cells targeted to such loci by a range of environmental cues. We report here that receptor for AGE (RAGE) is a central cell surface receptor for EN-RAGE (e xtracellular n ewly identified RAGE-binding protein) and related members of the S100/calgranulin superfamily. Interaction of EN-RAGEs with cellular RAGE on endothelium, mononuclear phagocytes, and lymphocytes triggers cellular activation, with generation of key proinflammatory mediators. Blockade of EN-RAGE/RAGE quenches delayed-type hypersensitivity and inflammatory colitis in murine models by arresting activation of central signaling pathways and expression of inflammatory gene mediators. These data highlight a novel paradigm in inflammation and identify roles for EN-RAGEs and RAGE in chronic cellular activation and tissue injury

Evaluation of Right-of-Way Fence Tags to Reduce Animal-Vehicle Collisions

Animal-vehicle collisions (AVC) pose a serious and growing threat to motorists traveling on ADOT roads. Solutions exist to effectively mitigate AVC, such as wildlife crossing structures (overpasses and underpasses), however these solutions can be costly and untimely. Fence tags, a small reflective tag that is attached to the right-of-way fence and deter animals from crossing the fence, provide a potential cost-effective solution to reduce AVC. The research team evaluated the effectiveness of fence tags designed by Swift Creek, LLC, in reducing AVC. Fence tags were installed along both sides of five 2-mile segments of roadway and maintained for three years by replacing missing or damaged fence tags on a quarterly basis. The research team queried ADOT Crash Data to determine changes in AVC prior to the study (July 1, 2015 \u2013 June 30, 2018) and following fence tag installation (July 1, 2018 \u2013 June 30, 2021). Collisions in the areas where fence tags were installed were reduced by an average of 25.4 percent across all sites. This reduction was significant; however, the control sites were also reduced by a similar average of 25.8 percent across all study sites. These findings indicate that (1) the effectiveness of fence tags at reducing AVC were not noticeably different than the control, or (2) external factors that were not considered in the study, such as the effect of nearby road construction, may have influenced the effectiveness of the fence tags. To better understand the results of this study and improve available data for future projects and management decisions, the research team recommends: (1) further examining fence tags as a viable mitigation technique by looking at other aspects that could be taken into account in the study, such as other external factors affecting their use; measuring the effective tag size; implementing a longer observation period before, during, and after the intervention, etc. and (2) implementing data collection forms that capture animal type/species

Succinate accumulation drives ischaemia-reperfusion injury during organ transplantation.

During heart transplantation, storage in cold preservation solution is thought to protect the organ by slowing metabolism; by providing osmotic support; and by minimising ischaemia-reperfusion (IR) injury upon transplantation into the recipient1,2. Despite its widespread use our understanding of the metabolic changes prevented by cold storage and how warm ischaemia leads to damage is surprisingly poor. Here, we compare the metabolic changes during warm ischaemia (WI) and cold ischaemia (CI) in hearts from mouse, pig, and human. We identify common metabolic alterations during WI and those affected by CI, thereby elucidating mechanisms underlying the benefits of CI, and how WI causes damage. Succinate accumulation is a major feature within ischaemic hearts across species, and CI slows succinate generation, thereby reducing tissue damage upon reperfusion caused by the production of mitochondrial reactive oxygen species (ROS)3,4. Importantly, the inevitable periods of WI during organ procurement lead to the accumulation of damaging levels of succinate during transplantation, despite cooling organs as rapidly as possible. This damage is ameliorated by metabolic inhibitors that prevent succinate accumulation and oxidation. Our findings suggest how WI and CI contribute to transplant outcome and indicate new therapies for improving the quality of transplanted organs.Work in the M.P.M. laboratory was supported by the Medical Research Council UK (MC_U105663142) and by a Wellcome Trust Investigator award (110159/Z/15/Z) to M.P.M. Work in the C.F. laboratory was supported by the Medical Research Council (MRC_MC_UU_12022/6). Work in the K.S.P. laboratory was supported by the Medical Research Council UK. Work in the RCH lab laboratory was supported by a Wellcome Trust Investigator award (110158/Z/15/Z) and a PhD studentship for .L.P from the University of Glasgow. A.V.G. was supported by a PhD studentship funded by the National Institute for Health Research Blood and Transplant Research Unit (NIHR BTRU) in Organ Donation and Transplantation at the University of Cambridge in collaboration with Newcastle University and in partnership with NHS Blood and Transplant (NHSBT)