Aerodynamic Mitigation of Mechanical Constraints in Small Compressor Blade Profiles

2021 ◽  
Author(s):  
Tony Dickens ◽  
James Taylor ◽  
Chris Hall ◽  
Rob Miller
Keyword(s):  
Mitigation Strategies ◽  
Core Size ◽  
Trailing Edge ◽  
Flow Angle ◽  
The Past ◽  
Mechanical Constraints ◽  
Trailing Edges ◽  
Local Modification ◽  
Profile Loss ◽  
Local Nature

Abstract The drive for ever higher aircraft efficiency inevitably leads to a reduction in core compressor size; over the past 30 years the height of the rear stages of a typical aeroengine has reduced by 40%. This trend will continue; a further reduction of almost 50% is expected by 2050. It is shown in this paper that the two greatest sources of increased profile loss as core size is reduced comes from the mechanical and manufacturing constraints placed on the maximum and trailing edge thickness. Furthermore, mitigation strategies are presented which successfully minimized or eliminated these loss sources. An experimental study showed that local modification to the trailing edge shape from a semi-circle to a more elliptical shape almost entirely eliminated the increase in trailing edge loss associated with a reduction in compressor size. Elliptical trailing edges improved loss by both narrowing the wake and increasing the base pressure. Despite the local nature of the modification, the elliptical trailing edges had a powerful effect on flow turning. This was accounted for by redesigning each design to achieve the specified exit flow angle. A set of “as manufactured” small core blades was created by combining measured data from existing manufacture methods with airfoils scaled to ensure minimum thicknesses necessary for mechanical integrity along the blade were not breached. Core sizes down to 40% of current designs were run in CFD. It is often assumed that the loss in efficiency as core size is reduced is unavoidable. However, it was shown that approximately half of this is directly due to the increase in thickness to satisfy tolerancing. Part to part deviation has negligible effect at all but the smallest compressor size tested (at 40% of current values).

The Base Pressure and Loss of a Family of Four Turbine Blades

1988 ◽  
Vol 110 (1) ◽  
pp. 9-17 ◽  
Author(s):  
L. Xu ◽  
J. D. Denton
Keyword(s):  
Dominant Role ◽  
Turbine Blades ◽  
Base Pressure ◽  
Trailing Edge ◽  
Edge Geometry ◽  
Trailing Edges ◽  
Loss Prediction ◽  
Turbine Cascades ◽  
Profile Loss ◽  
Made In

Measurements of the effect of trailing edge geometry on the base pressure and loss of a family of four turbine cascades are presented. The measurements were made in the transonic range of Mach number from 0.8 to 1.2. It is found that, for blades with typical trailing edge thickness, the trailing edge loss is the major source of profile loss at these speeds and that the base pressure plays a dominant role in determining the loss. For blades with thick trailing edges an accurate prediction of base pressure is crucial to loss prediction. However, it is found that current methods of base pressure prediction are unable to give reliable predictions.

scholarly journals Analgesia for Sheep in Commercial Production: Where to Next?

Animals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 1127
Author(s):  
Alison Small ◽  
Andrew David Fisher ◽  
Caroline Lee ◽  
Ian Colditz
Keyword(s):  
Research Effort ◽  
Mitigation Strategies ◽  
Worth Living ◽  
Life Worth Living ◽  
The Past ◽  
Considerable Research ◽  
Husbandry Practices ◽  
Industry Practice ◽  
Successful Launch ◽  
Inflammatory Drugs

Increasing societal and customer pressure to provide animals with ‘a life worth living’ continues to apply pressure on livestock production industries to alleviate pain associated with husbandry practices, injury and illness. Over the past 15–20 years, there has been considerable research effort to understand and develop mitigation strategies for painful husbandry procedures in sheep, leading to the successful launch of analgesic approaches specific to sheep in a number of countries. However, even with multi-modal approaches to analgesia, using both local anaesthetic and non-steroidal anti-inflammatory drugs (NSAID), pain is not obliterated, and the challenge of pain mitigation and phasing out of painful husbandry practices remains. It is timely to review and reflect on progress to date in order to strategically focus on the most important challenges, and the avenues which offer the greatest potential to be incorporated into industry practice in a process of continuous improvement. A structured, systematic literature search was carried out, incorporating peer-reviewed scientific literature in the period 2000–2019. An enormous volume of research is underway, testament to the fact that we have not solved the pain and analgesia challenge for any species, including our own. This review has highlighted a number of potential areas for further research.

scholarly journals Effects of Periodic Wake Passing Upon Aerodynamic Loss of a Turbine Cascade: Part I — Measurements of Wake-Affected Cascade Loss by Use of a Pneumatic Probe

1999 ◽  
Author(s):  
Ken-ichi Funazaki ◽  
Nobuaki Tetsuka ◽  
Tadashi Tanuma
Keyword(s):  
Turbine Cascade ◽  
Flow Angle ◽  
Linear Cascade ◽  
Local Loss ◽  
Aerodynamic Loss ◽  
Free Stream Turbulence ◽  
Pressure Distributions ◽  
Wake Turbulence ◽  
Wake Passing ◽  
Profile Loss

This paper reports on an experimental investigation of aerodynamic loss of a low-speed linear turbine cascade which is subjected to periodic wakes shed from moving bars of the wake generator. In this case, parameters related to the wake, such as wake passing frequency (wake Strouhal number) or wake turbulence characteristics, are varied to see how these wake-related parameters affect the local loss distribution or mass-averaged loss coefficient of the turbine cascade. Free-stream turbulence intensity is changed by use of a turbulence grid. In Part I of this paper a focus is placed on the measurements by use of a pneumatic five-hole yawmeter, which provides time-averaged stagnation pressure distributions downstream of the moving bars as well as of the turbine cascade. Spanwise distributions of wake-affected exit flow angle are also measured. From this study it is found that the wake passing greatly affects not only the profile loss but secondary loss of the linear cascade. Noticeable change in exit flow angle is also identified.

scholarly journals Urban Risks and Resilience

2021 ◽  
pp. 197-211
Author(s):  
Susan L. Cutter
Keyword(s):  
Adverse Events ◽  
Case Studies ◽  
Mitigation Strategies ◽  
Urban Resilience ◽  
Building Capacity ◽  
Urban Informatics ◽  
The Past ◽  
End Point ◽  
Point Versus

AbstractThe resilience concept has become more significant in the past decade as a means for understanding how cities prepare and plan for, absorb, recover from, and more successfully adapt to adverse events. Definitional differences—resilience as an outcome or end-point versus resilience as a process of building capacity—dominate the literature. Lagging behind are efforts to systematically measure resilience to produce a baseline and subsequent monitoring, in order to gauge what, where, and how intervention or mitigation strategies would strengthen or weaken urban resilience. The chapter reviews research and practitioner attempts to develop urban informatics for resilience and provides selected case studies of cities as exemplars.

scholarly journals TACO and TRALI: biology, risk factors, and prevention strategies

Hematology ◽  
2018 ◽  
Vol 2018 (1) ◽  
pp. 585-594 ◽  
Author(s):  
Nareg Roubinian
Keyword(s):  
Risk Factors ◽  
Mitigation Strategies ◽  
Blood Component ◽  
Patient Blood Management ◽  
Blood Management ◽  
Prevention Strategies ◽  
In Vivo Models ◽  
The Past ◽  
Circulatory Overload

AbstractTransfusion-related acute lung injury (TRALI) and transfusion-associated circulatory overload (TACO) are the leading causes of transfusion-related morbidity and mortality. These adverse events are characterized by acute pulmonary edema within 6 hours of a blood transfusion and have historically been difficult to study due to underrecognition and nonspecific diagnostic criteria. However, in the past decade, in vivo models and clinical studies utilizing active surveillance have advanced our understanding of their epidemiology and pathogenesis. With the adoption of mitigation strategies and patient blood management, the incidence of TRALI and TACO has decreased. Continued research to prevent and treat these severe cardiopulmonary events is focused on both the blood component and the transfusion recipient.

scholarly journals Role of Polymeric Coating on Metallic Foams to Control the Aeroacoustic Noise Reduction of Airfoils with Permeable Trailing Edges

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1087 ◽  
Author(s):  
Reza Hedayati ◽  
Alejandro Rubio Carpio ◽  
Salil Luesutthiviboon ◽  
Daniele Ragni ◽  
Francesco Avallone ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Metal Foams ◽  
Polymeric Coating ◽  
Metallic Foams ◽  
Noise Mitigation ◽  
Trailing Edge ◽  
Reference Case ◽  
Pore Sizes ◽  
Coated Metal ◽  
Trailing Edges

Studies on porous trailing edges, manufactured with open-cell Ni-Cr-Al foams with sub-millimeter pore sizes, have shown encouraging results for the mitigation of turbulent boundary-layer trailing-edge noise. However, the achieved noise mitigation is typically dependent upon the pore geometry, which is fixed after manufacturing. In this study, a step to control the aeroacoustics effect of such porous trailing edges is taken, by applying a polymeric coating onto the internal foam structure. Using this method, the internal topology of the foam is maintained, but its permeability is significantly affected. This study opens a new possibility of aeroacoustic control, since the polymeric coatings are temperature responsive, and their thickness can be controlled inside the foam. Porous metallic foams with pore sizes of 580, 800, and 1200 μm are (internally) spray-coated with an elastomeric coating. The uncoated and coated foams are characterized in terms of reduced porosity, average coating thickness and air-flow resistance. Subsequently, the coated and uncoated foams are employed to construct tapered inserts installed at the trailing edge of an NACA 0018 airfoil. The noise mitigation performances of the coated metal foams are compared to those of uncoated metal foams with either similar pore size or permeability value, and both are compared to the solid trailing edge reference case. Results show that that the permeability of the foam can be easily altered by the application of an internal coating on the metallic foams. The noise reduction characteristics of the coated foams are similar to equivalent ones with metallic materials, provided that the coating material is rigid enough not to plastically deform under flow conditions.

scholarly journals A spatial multicriteria prioritizing approach for geo-hydrological risk mitigation planning in small and densely urbanized Mediterranean basins

2019 ◽  
Vol 19 (1) ◽  
pp. 53-69 ◽  
Author(s):  
Guido Paliaga ◽  
Francesco Faccini ◽  
Fabio Luino ◽  
Laura Turconi
Keyword(s):  
Risk Mitigation ◽  
Process Analysis ◽  
Mitigation Strategies ◽  
Economic Resources ◽  
Rain Event ◽  
Catchment Scale ◽  
Effective Prevention ◽  
The Past ◽  
High Hazard ◽  
A Priority

Abstract. Landslides and floods, particularly flash floods, occurred recently in many Mediterranean catchments as a consequence of heavy rainfall events, causing damage and sometimes casualties. The high hazard is often associated with high vulnerability deriving from intense urbanization, in particular along the coastline where streams are habitually culverted. The necessary risk mitigation strategies should be applied at the catchment scale with a holistic approach, avoiding spot interventions. In the present work, a high-risk area, hit in the past by several floods and concurrent superficial landslides due to extremely localized and intense rain events, has been studied. A total of 21 small catchments have been identified: only some of them have been hit by extremely damaging past events, but all lie in the intense-rain high-hazard area and are strongly urbanized in the lower coastal zone. The question is what would happen if an intense rain event should strike one of the not previously hit catchments; some situations could be worse or not, so attention has been focused on the comparison among catchments. The aim of the research has been identifying a priority scale among catchments, pointing out the more critical ones and giving a quantitative comparison tool for decision makers to support strong scheduling of long-time planning interventions at the catchment scale. The past events' effects and the geomorphic process analysis together with the field survey allowed us to select three sets of parameters: one describing the morphometric–morphological features related to flood and landslide hazard, another describing the degree of urbanization and of anthropogenic modifications at the catchment scale and the last related to the elements that are exposed to risk. The realized geodatabase allowed us to apply the spatial multicriteria analysis technique (S-MCA) to the descriptive parameters and to obtain a priority scale among the analyzed catchments. The scale can be used to plan risk mitigation interventions starting from the more critical catchments, then focusing economic resources primarily on them and obtaining an effective prevention strategy. The methodology could be useful even to check how the priority scale is modified during the progress of the mitigation work realization. In addition, this approach could be applied in a similar context, even among sub-catchments, after identifying a suitable set of descriptive parameters depending on the active geomorphological processes and the kind of anthropogenic modification. The prioritization would allow to invest economic resources in risk mitigation interventions priory in the more critical catchments.

Effect of Unguided Turning Angle and Trailing Edge Shape on Cooled Blade Loss

2014 ◽  
Author(s):  
Andrey Granovskiy ◽  
Mikhail Kostege ◽  
Vladimir Vassiliev
Keyword(s):  
Gas Turbines ◽  
Numerical Procedure ◽  
Suction Side ◽  
Aerodynamic Characteristics ◽  
Base Pressure ◽  
Trailing Edge ◽  
Flow Angle ◽  
Generation Mechanisms ◽  
Cooled Blade ◽  
Blade Loss

A significant part of the overall loss in modern gas turbines is the trailing edge loss. This loss is, more strongly than other constituents, affected by operation, because the trailing edge can significantly change its shape due to degradation. Also by manufacturing of new parts and reconditioning the same tolerances as in other parts of blade lead to higher deviations of aerodynamic characteristics. Therefore the understanding of trailing edge loss generation mechanisms is of utmost importance for a sound blade design. In this work the results of combined experimental and numerical investigation of the trailing edge impact on the transonic cooled blade loss are presented. This study comprises the investigation of the unguided flow angle and the trailing edge shape on the profile losses and a base pressure. The unguided flow angle characterizes the curvature distribution on the aerofoil suction side. The numerical and experimental investigation of transonic cooled turbine cascades have shown that the increase of the unguided flow angle results in loss reduction due to increase of the base pressure downstream of the trailing edge. At the same time the deviation of the trailing edge from a round shape has detrimental effect on performance and conducted investigations allow quantification of this effect. The measurements were performed in a transonic wind tunnel and numerical simulations were done using in-house 2D Navier-Stokes code. The comparison of calculations with measurements showed that they are in reasonable agreement. The validated numerical procedure has been used for demonstration of possibility to reduce loss in aerofoil with thick trailing edge by tuning of the unguided flow angle. The use of the thick trailing edges at HP cooled turbines reduces restriction on tolerances, improves of manufacturability and reduces cost.

Heat Transfer in a Vane Trailing Edge Passage With Conical Pins and Pin-Turbulator Integrated Configurations

2014 ◽  
Author(s):  
J. Kruekels ◽  
S. Naik ◽  
A. Lerch ◽  
A. Sedlov
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Gas Turbine ◽  
Internal Heat ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Heat Transfer Coefficients ◽  
Trailing Edges ◽  
Converging Channel ◽  
Internal Heat Transfer

The trailing edge sections of gas turbine vanes and blades are generally subjected to extremely high heat loads due to the combined effects of high external accelerating Mach numbers and gas temperatures. In order to maintain the metal temperatures of these trailing edges to a level, which fulfills the mechanical integrity of the parts, highly efficient cooling of the trailing edges is required without increasing the coolant consumption, as the latter has a detrimental effect on the overall gas turbine performance. In this paper the characteristics of the heat transfer and pressure drop of two novel integrated pin bank configurations were investigated. These include a pin bank with conical pins and a pin bank consisting of cylindrical pins and intersecting broken turbulators. As baseline case, a pin bank with cylindrical pins was studied as well. All investigations were done in a converging channel in order to be consistent with the real part. The heat transfer and pressure drop of all the pin banks were investigated initially with the use of numerical predictions and subsequently in a scaled experimental wind tunnel. The experimental study was conducted for a range of operational Reynolds numbers. The TLC (thermochromic liquid crystal) method was used to measure the detailed heat transfer coefficients in scaled Perspex models representing the various pin bank configurations. Pressure taps were located at several positions within the test sections. Both local and average heat transfer coefficients and pressure loss coefficients were determined. The measured and predicted results showed that the local internal heat transfer coefficient increases in the flow direction. This was due to the flow acceleration in the converging channel. Furthermore, both the broken ribs and the conical pin banks resulted in higher heat transfer coefficients compared with the baseline cylindrical pins. The conical pins produced the highest average internal heat transfer coefficients in contrast to the pins with the broken ribs, though this was also associated with a higher pressure drop.

Investigation of the Surge Behavior of a Multi-Stage Axial Compressor With a Multi-Sensor Probe

2011 ◽  
Author(s):  
P. Waniczek ◽  
P. Jeschke ◽  
H. Schoenenborn ◽  
T. Metzler
Keyword(s):  
Flow Field ◽  
Velocity Vector ◽  
Reverse Flow ◽  
Axial Compressor ◽  
Leading Edge ◽  
Field Structure ◽  
Pressure Probe ◽  
High Time Resolution ◽  
Trailing Edge ◽  
Flow Angle

The surge behavior of the first rotor of an eight-stage aero engine high pressure compressor has been investigated experimentally. For that purpose, a new multi-hole pressure probe was developed and adapted to the axial compressor test rig. Due to the high time resolution measurements (more than 45000 measuring points per surge cycle) it is possible to investigate the dynamic flow field of a surge cycle in a time-accurate manner. The results especially show the complex flow field structure at the surge inception. At the rotor leading edge the flow shows perturbations with high amplitudes and initiates the surge event, whereas the flow at the rotor trailing edge is less influenced. The inflow vector turns around the leading edge of the blade relatively slowly. During that turn around three different characteristic flow conditions have been identified. These are ‘zero rotor turning’, ‘turbine-like flow’ and ‘no flow’. ‘No flow’ means, that the absolute velocity vector reaches a flow angle where it consists of a pure tangential velocity component. That is the point where the reverse flow phase is initiated. A 180° shift of the flow direction at the rotor trailing edge is the consequence. After a quasi-steady reverse flow the acceleration of the flow starts. In total, this paper gives new and fundamental insights into the unsteady flow field phenomena during various surge cycles. Especially the transient velocity vector imparts a good idea of the flow field structure of a surging compressor.

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