The Optimization of an Integrated Strut OGV Configuration

2014 ◽  
Author(s):  
Yadong Xie ◽  
Xiaohe Yang ◽  
Jianguo Ding ◽  
Xiaofeng Liu ◽  
Jinzhang Feng
Keyword(s):  
Guide Vane ◽  
Thickness Distribution ◽  
Large Diameter ◽  
Axial Direction ◽  
Maximum Diameter ◽  
Axial Distance ◽  
Recovery Coefficient ◽  
Maximum Thickness ◽  
Circumferential Distribution

In a core-mounted high-bypass ratio aero engine the bypass strut is designed to support the intermediate casing and to go the RDF (radial drive shaft) of a large diameter. Therefore the maximum thickness of the strut and maximum thickness distribution along the chord are restricted by the maximum diameter of the RDF. In order to enhance the total pressure recovery coefficient as well as reducing the backpressure circumferential variation, in this paper we describe the optimization of a datum configuration of the circumferential integrated strut OGV (Outlet Guide Vane). The datum configuration was designed based on an original configuration in which OGV and struts are separated axially. In the datum configuration, OGV is moved down-stream to be combined with the struts. The combined strut not only supports the casing as discussed above but also plays the role of turning the flow from the upstream fan to the axial direction. At the same time, the maximum thickness of the strut is about 8 times thicker than that of the OGV. The datum configuration will reduce noise because of larger axial distance between fan and OGVs as well as reducing weight because of fewer struts used in datum configuration. A re-staggering of OGV with sweep and dihedral both at the tip and hub will be used to optimize this datum configuration. Both datum configuration and optimized configuration will be compared with respected to the pressure loss included in the OGV and struts and the backpressure circumferential distribution variation.

scholarly journals Numerical Investigation of a Radially Cooled Turbine Guide Vane Using Air and Steam as a Cooling Medium

Computation ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 63
Author(s):  
Sondre Norheim ◽  
Shokri Amzin
Keyword(s):  
Numerical Model ◽  
Gas Turbines ◽  
Guide Vane ◽  
Axial Direction ◽  
Average Error ◽  
Inlet Temperature ◽  
Average Temperature ◽  
Cooling Medium ◽  
Turbine Guide Vane ◽  
Steam Cooling

Gas turbine performance is closely linked to the turbine inlet temperature, which is limited by the turbine guide vanes ability to withstand the massive thermal loads. Thus, steam cooling has been introduced as an advanced cooling technology to improve the efficiency of modern high-temperature gas turbines. This study compares the cooling performance of compressed air and steam in the renowned radially cooled NASA C3X turbine guide vane, using a numerical model. The conjugate heat transfer (CHT) model is based on the RANS-method, where the shear stress transport (SST) k−ω model is selected to predict the effects of turbulence. The numerical model is validated against experimental pressure and temperature distributions at the external surface of the vane. The results are in good agreement with the experimental data, with an average error of 1.39% and 3.78%, respectively. By comparing the two coolants, steam is confirmed as the superior cooling medium. The disparity between the coolants increases along the axial direction of the vane, and the total volume average temperature difference is 30 K. Further investigations are recommended to deal with the local hot-spots located near the leading- and trailing edge of the vane.

Thermally developing forced convection flow through porous concentric pipes annular duct

2021 ◽  
pp. 095440622110022
Author(s):  
Farhan Ahmed
Keyword(s):  
Flow Region ◽  
Axial Direction ◽  
Darcy Number ◽  
Convection Flow ◽  
Axial Distance ◽  
Cross Sectional ◽  
Developing Flow ◽  
Annular Sector ◽  
Flow Through ◽  
The Cross

This article shows the thermally developing flow through concentric pipes annular sector duct by describing the Darcy Brinkman flow field. The cross sectional convection-diffusion terms are transformed in power law discretized form by integrating over the differential volume, whereas backward difference scheme is used in the axial direction of heat flow. With the help of semi implicit method for pressure linked equations-revised ( SIMPLE-R), we get the solution of the governing problem. The graphs of velocity profiles against R and average Nusselt number against axial distance are plotted for different values of Darcy number and geometrical configuration parameters. It has been pointed out that velocity and thermal entrance length decrease, when we decrease the value of Darcy number. By decreasing the cross section of the concentric pipes annular sector duct in the transverse direction, thermally fully developed flow region develops earlier.

scholarly journals Anatomy and physiology of phrenic afferent neurons

2017 ◽  
Vol 118 (6) ◽  
pp. 2975-2990 ◽  
Author(s):  
Jayakrishnan Nair ◽  
Kristi A. Streeter ◽  
Sara M. F. Turner ◽  
Michael D. Sunshine ◽  
Donald C. Bolser ◽  
...  
Keyword(s):  
Potential Role ◽  
Large Diameter ◽  
Respiratory Cycle ◽  
Conscious Perception ◽  
Relative Impact ◽  
Afferent Neurons ◽  
Sensory Afferents ◽  
Synaptic Contacts ◽  
Anatomy And Physiology

Large-diameter myelinated phrenic afferents discharge in phase with diaphragm contraction, and smaller diameter fibers discharge across the respiratory cycle. In this article, we review the phrenic afferent literature and highlight areas in need of further study. We conclude that 1) activation of both myelinated and nonmyelinated phrenic sensory afferents can influence respiratory motor output on a breath-by-breath basis; 2) the relative impact of phrenic afferents substantially increases with diaphragm work and fatigue; 3) activation of phrenic afferents has a powerful impact on sympathetic motor outflow, and 4) phrenic afferents contribute to diaphragm somatosensation and the conscious perception of breathing. Much remains to be learned regarding the spinal and supraspinal distribution and synaptic contacts of myelinated and nonmyelinated phrenic afferents. Similarly, very little is known regarding the potential role of phrenic afferent neurons in triggering or modulating expression of respiratory neuroplasticity.

Flow Measurements in a Nozzle Guide Vane Passage With a Low Aspect Ratio and Endwall Contouring

2000 ◽  
Author(s):  
Steven W. Burd ◽  
Terrence W. Simon
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Guide Vane ◽  
Flow Measurements ◽  
Vast Number ◽  
Aspect Ratios ◽  
Nozzle Guide Vane ◽  
Endwall Contouring ◽  
Nozzle Guide

The vast number of turbine cascade studies in the literature has been performed in straight-endwall, high-aspect-ratio, linear cascades. As a result, there has been little appreciation for the role of, and added complexity imposed by, reduced aspect ratios. There also has been little documentation of endwall profiling at these reduced spans. To examine the role of these factors on cascade hydrodynamics, a large-scale nozzle guide vane simulator was constructed at the Heat Transfer Laboratory of the University of Minnesota. This cascade is comprised of three airfoils between one contoured and one flat endwall. The geometries of the airfoils and endwalls, as well as the experimental conditions in the simulator, are representative of those in commercial operation. Measurements with hot-wire anemometry were taken to characterize the flow approaching the cascade. These measurements show that the flow field in this cascade is highly elliptic and influenced by pressure gradients that are established within the cascade. Exit flow field measurements with triple-sensor anemometry and pressure measurements within the cascade indicate that the acceleration imposed by endwall contouring and airfoil turning is able to suppress the size and strength of key secondary flow features. In addition, the flow field near the contoured endwall differs significantly from that adjacent to the straight endwall.

Expanding the Role of Endovenous Laser Therapy: Results in Large Diameter Saphenous, Small Saphenous, and Anterior Accessory Veins

2011 ◽  
Vol 25 (5) ◽  
pp. 656-661 ◽  
Author(s):  
Cassius Iyad Ochoa Chaar ◽  
Stanley A. Hirsch ◽  
Michael T. Cwenar ◽  
Robert Y. Rhee ◽  
Rabih A. Chaer ◽  
...  
Keyword(s):  
Laser Therapy ◽  
Large Diameter ◽  
Endovenous Laser Therapy

A New Loss and Deviation Model for Axial Compressor Inlet Guide Vanes

2013 ◽  
Author(s):  
Milan Banjac ◽  
Milan V. Petrovic ◽  
Alexander Wiedermann
Keyword(s):  
Guide Vane ◽  
Thickness Distribution ◽  
Axial Compressor ◽  
Algebraic Model ◽  
Operating Conditions ◽  
Inlet Guide Vane ◽  
Viscous Effects ◽  
Through Flow ◽  
Trailing Vortices ◽  
Compressor Inlet

This paper describes a new universal algebraic model for the estimation of flow deflection and losses in axial compressor inlet guide vane devices. The model deals with nominal flow and far-off-design operating conditions in connection with large stagger angle adjustments. The first part of the model considers deflection and losses in 2D cascades, taking into account the main cascade geometry parameters and operating conditions, such as Mach number and stagger adjustment. The second part of the model deals with additional deviation and losses due to secondary flow caused by the endwall viscous effects and by the trailing vortices. The model is developed for NACA65 airfoils, NACA63-A4K6 airfoils and airfoils having an NACA65 thickness distribution on a circular-arc camber line. It is suitable for application in 1D or 2D through-flow calculations for design and analysis cases. The development of the method is based on systematic CFD flow calculations for various cascade geometries and operating parameters. The comparison of correlation results with experimental data for several test cases shows good agreement.

Flow-Induced Vibration of a Large-Diameter Elbow Piping Based on Random Force Measurement Caused by Conveying Fluid: Visualization Test Results

2005 ◽  
Author(s):  
Tomomichi Nakamura ◽  
Tadashi Shiraishi ◽  
Yoshihide Ishitani ◽  
Hisato Watakabe ◽  
Hiromi Sago ◽  
...  
Keyword(s):  
Force Measurement ◽  
Large Diameter ◽  
Pressure Fluctuations ◽  
Pressure Sensors ◽  
Maximum Flow ◽  
Axial Direction ◽  
Random Force ◽  
Test Facility ◽  
Flow Induced Vibration ◽  
Correlation Lengths

A 1/3 scale flow-induced vibration test facility that simulates the hot-leg piping of the JNC sodium-cooled fast reactor (JSFR) is used to investigate the pressure fluctuations of the pipe, where the high velocity fluid flows inside the piping. By the measurement of the pressure drop in the elbow piping while changing the Reynolds number, the similarity law of this model is confirmed. To evaluate the flow-induced vibrations for the hot-leg and cold-leg pipes, the random force distributions along the pipe and their correlations are measured with pressure sensors in a water loop. It is found that a flow velocity-dependent periodic phenomenon in the rear region of the elbow, and the maximum flow-induced random vibration force in the pipe are observed in the region of flow separation downstream the elbow. Finally, a design method is proposed with power spectral densities of the pressure fluctuations classified into four sections, correlation lengths in the axial direction divided into three sections, and with correlation lengths in the tangential direction into four sections.

Static Pressure-Volume Curves for the Lung of the Frog (Rana Pipiens)

1978 ◽  
Vol 76 (1) ◽  
pp. 149-165 ◽  
Author(s):  
G. M. HUGHES ◽  
G. A. VERGARA
Keyword(s):  
Volume Change ◽  
Rana Pipiens ◽  
Static Pressure ◽  
Large Diameter ◽  
The Difference ◽  
Isolated Lungs ◽  
Precise Role ◽  
Different Parts

1. Static pressure/volume curves have been determined for isolated frog lungs inflated with either air or saline. In both cases a hysteresis was present: the pressure required to produce unit change of volume being greater during inflation than deflation. 2. The pressure necessary for a given volume change was less for the saline-filled than the air-filled lungs. The difference between these curves is due to the surface tension at the air/lung interface. 3. Pressure/volume curves for air-filled lungs in situ were similar to curves for isolated lungs. However, a greater pressure was required for the same volume change during both inflation and deflation. 4. Compliance was calculated from different parts of air pressure/volume curves and gave values greater than those obtained using similar calculations for higher vertebrates. 5. These observations support other evidence for the presence of a surfactant in the lung lining of frogs in spite of the relatively large diameter of their ‘alveoli.’ The precise role of such a lining is uncertain and it is concluded that similar forces may be involved during the inflation and deflation of lungs of frogs and higher vertebrates in spite of differences in gross morphology.

The Early Development of Muscle Spindles in the Rat

1973 ◽  
Vol 12 (1) ◽  
pp. 175-195
Author(s):  
ALICE MILBURN
Keyword(s):  
Close Association ◽  
Large Diameter ◽  
Muscle Spindles ◽  
Muscle Fibres ◽  
Intrafusal Muscle ◽  
Intrafusal Fibres ◽  
Fusimotor Innervation ◽  
Nuclear Chain ◽  
Intramuscular Nerve

The morphogenesis of muscle spindles in rat lower hind-limb muscles has been investigated using the electron microscope. The earliest detectable spindles are seen in the 19.5-day foetus and consist of a single myotube bearing simple nerve terminals of the large primary afferent axon from nearby unmyelinated intramuscular nerve trunks. The capsule forms by an extension of the perineural epithelium of the supplying nerve fasciculus, and is confined initially to the innervated zone. Myonuclei accumulate in this region, so that the first intrafusal muscle fibre to develop is a nuclear-bag fibre. Myoblasts, present within the capsule of the spindle throughout its development, fuse to form a smaller less-differentiated myotube by the 20-day foetal stage. This new myotube matures by close association with the initial fibre, and by birth (21-22 days gestation) has formed the smaller, intermediate bag fibre, that has been identified histochemically and ultrastructurally in the adult. The nuclear-chain fibres develop in the same way; myoblasts fuse to form satellite myotubes that mature in pseudopodial apposition to one of the other fibres within its basement membrane. This apposition consists of extensions of sarcoplasm from the developing myotube into the supporting fibre. By the 4-day postnatal stage the full adult complement of 4 intrafusal muscle fibres is present, although ultrastructural variations, seen in the adult, are not differentiated. The fusimotor innervation begins to arrive at birth, but is not mature until the 12th postnatal day, when the myofibrillar ultrastructural differentiation, including the loss of the M-line in the large-diameter bag fibre, is complete. The periaxial space appears at the same time. It is suggested that the sequential development of the intrafusal fibres is a reflexion of the decreasing morphogenetic effect of the afferent innervation, whereas the role of the fusimotor innervation is in ultrastructural, myofibrillar differentiation.

Selection of fewer dominant follicles in Trio carriers given GnRH antagonist and luteinizing hormone action replaced by nonpulsatile human chorionic gonadotropin†

2020 ◽  
Vol 103 (6) ◽  
pp. 1217-1228
Author(s):  
Victor E Gomez-León ◽  
João Paulo Andrade ◽  
Brian W Kirkpatrick ◽  
Sadrollah Molaei Moghbeli ◽  
Alvaro García-Guerra ◽  
...  
Keyword(s):  
Luteinizing Hormone ◽  
Chorionic Gonadotropin ◽  
Human Chorionic Gonadotropin ◽  
Gnrh Antagonist ◽  
Maximum Diameter ◽  
High Fecundity ◽  
Follicle Diameter ◽  
Follicle Selection ◽  
Selection Of

Abstract Studying selection of multiple dominant follicles (DFs) in monovulatory species can advance our understanding of mechanisms regulating selection of single or multiple DFs. Carriers of the bovine high fecundity Trio allele select multiple DFs, whereas half-sib noncarriers select a single DF. This study compared follicle selection during endogenous gonadotropin pulses versus during ablation of pulses with Acyline (GnRH antagonist) and luteinizing hormone (LH) action replaced with nonpulsatile human chorionic gonadotropin (hCG) treatment in Trio carriers (n = 28) versus noncarriers (n = 32). On Day 1.5 (Day 0 = ovulation), heifers were randomized: (1) Control, untreated; (2) Acyline, two i.m. doses (Days 1.5 and D3) of 3 μg/kg; (3) hCG, single i.m. dose of 50 IU hCG on Day 1.5 followed by daily doses of 100 IU; and (4) Acyline + hCG. Treatments with nonpulsatile hCG were designed to replace LH action in heifers treated with Acyline. Acyline treatment resulted in cessation of follicle growth on Day 3 with smaller (P < 0.0001) maximum follicle diameter in Trio carriers (6.6 ± 0.2 mm) than noncarriers (8.7 ± 0.4 mm). Replacement of LH action (hCG) reestablished follicle diameter deviation and maximum diameter of DFs in both genotypes (8.9 ± 0.3 mm and 13.1 ± 0.5 mm; P < 0.0001). Circulating follicle stimulating hormone (FSH) was greater in Acyline-treated than in controls. Finally, Acyline + hCG decreased (P < 0.0001) the number of DFs from 2.7 ± 0.2 to 1.3 ± 0.2 in Trio carriers, with most heifers having only one DF. This demonstrates the necessity for LH in acquisition of dominance in Trio carriers (~6.5 mm) and noncarriers (~8.5 mm) and provides evidence for a role of GnRH-induced FSH/LH pulses in selection of multiple DFs in Trio carriers and possibly other physiologic situations with increased ovulation rate.

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