Preliminary Design of Axial Fans at Off-Design Working Points

2014 ◽  
Author(s):  
Matthias Semel ◽  
Julien Grilliat ◽  
Antonio Delgado
Keyword(s):  
Best Practice ◽  
Preliminary Design ◽  
Hydraulic Efficiency ◽  
Axial Fan ◽  
Free Vortex ◽  
Best Practice Guidelines ◽  
Work Distribution ◽  
Theoretical Predictions ◽  
Axial Fans ◽  
Straight Lines

An analytical formulation for axial fan performances at and off design point is proposed for an arbitrary work distribution. It is shown that the total pressure, total-to-static pressure and hydraulic efficiency characteristics can be described by means of hyperbola, straight lines and parabola. This formulation is applied to axial fans with free vortex work distributions, allowing a theoretical study onto the influence of the hub-to-tip ratio. Theoretical predictions are compared with numerical simulations. Good qualitative agreements are found. Conclusions onto the best practice guidelines for the design of axial fan according to a free vortex work distributions are presented.

Derivative Design of Axial Fan Range: From Academia to Industry

2016 ◽  
Author(s):  
Tommaso Bonanni ◽  
Lucio Cardillo ◽  
Alessandro Corsini ◽  
Giovanni Delibra ◽  
Anthony G. Sheard ◽  
...  
Keyword(s):  
Performance Prediction ◽  
Good Accuracy ◽  
Design Method ◽  
Three Dimensional ◽  
Correct Prediction ◽  
Preliminary Design ◽  
Axial Fan ◽  
Data Set ◽  
Axial Fans ◽  
Relative Errors

The work presented in this paper concerns a useful method for axial fans preliminary design based on the “Derivative Design” concept. The emphasis is, on one side, on education and, on the other, on the practical help that such method can provide in the early preliminary design process. A complete data set of an axial fan measured with ISO 5801 standards is the start point for the investigation and the prediction of the multiple possible performance that different fan configurations can provide, in terms of dimensionless duty coefficients. In particular, configurations with different number of blades, and hence of solidity, are studied. The typical options of derivative design are explored and relations for performance prediction are presented. A detailed description of the derivative design methodology is followed by tests and validation. The tools employed are a fully three dimensional code, the Advanceded Actuator Disk Mode (AADM), and two other in-house codes, the Meanline Axisymmetric Calculation (MAC) and Axisymmetric Laboratory (AXLAB). Results of the derivative design method are reported, showing a good accuracy against the AADM data. The MAC and AXLAB ensure still acceptable results when increasing the solidity of the machine. On the contrary, a decrease of solidity leads to higher relative errors in the prediction of the load coefficient. In conclusion, an exploration of the possible fields of operation of a blade profile can be carried out by a correct prediction of the stage diffusion factor.

The Role of Forward Sweep in Subsonic Axial Fan Rotor Aerodynamics at Design and Off-Design Operating Conditions

2003 ◽  
Author(s):  
A. Corsini ◽  
F. Rispoli
Keyword(s):  
Three Dimensional ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Design Parameters ◽  
Axial Fan ◽  
Suction Surface ◽  
Free Vortex ◽  
Application Range ◽  
Rotor Aerodynamics ◽  
Work Distribution

The role that forward sweep plays in the aerodynamics of subsonic axial fan rotor is herein discussed, with emphasis on the combined effects of non-uniform three-dimensional work distribution and modified stacking lines. To study blade forward sweep effects numerical investigations have been undertaken on highly loaded fans of non-free vortex design, with ideal total head rise coefficient typical of industrial application range. The results of two rotors with identical overall design parameters and, respectively, with 35-deg forward swept blades and unswept blades have been compared. The investigation has been carried-out using an accurate in-house developed multi-level parallel finite element RANS solver, with the adoption of a non-isotropic two-equation turbulence closure. The pay-off derived from the sweep technology has been assessed with respect to the operating range improvement. To this end the flow structure developing through the blade passages and downstream of the rotors as well as loss distributions have been analysed at three different operating conditions. The studies showed that the forward swept blade operates more efficiently in particular at low volume flows, with a delayed onset of stall. The analyses of three-dimensional flow structures showed that, sweeping forward the blade, the flow centrifugation on blade suction surface is reduced and non-free vortex spanwise secondary flows is attenuated. Moreover, reduced fluid mechanical losses have been also pointed out in rotor with swept blades.

scholarly journals Experiment-Based Preliminary Design Guidelines for Consideration of Profile Vortex Shedding From Low-Speed Axial Fan Blades

2021 ◽  
Vol 143 (6) ◽  
Author(s):  
Gábor Daku ◽  
János Vad
Keyword(s):  
Vortex Shedding ◽  
Design Guidelines ◽  
Preliminary Design ◽  
Axial Fan ◽  
Noise Emission ◽  
Blade Vibration ◽  
Low Speed ◽  
Blunt Trailing Edge ◽  
Axial Fans ◽  
Semi Empirical

Abstract This paper presents hot-wire measurements in a wind tunnel, close downstream of basic models of blade sections being representative for low-speed, low-Reynolds number axial fans, in order to explore the signatures of vortex shedding (VS) from the blade profiles. Using the Rankine-type vortex approach, an analytical model was developed on the velocity fluctuation represented by the vortex streets, as an aid in evaluating the experimental data. The signatures of profile VS were distinguished from blunt trailing-edge VS based on Strouhal numbers obtained from the measurements in a case-specific manner. Utilizing the experimental results, the semi-empirical model available in the literature for predicting the frequency of profile VS was extended to low-speed axial fan applications. On this basis, quantitative guidelines were developed for the consideration of profile VS in preliminary design of axial fans in the moderation of VS-induced blade vibration and noise emission.

scholarly journals Experiment-Based Preliminary Design Guidelines for Consideration of Profile Vortex Shedding From Low-Speed Axial Fan Blades

2020 ◽  
Author(s):  
Gábor Daku ◽  
János Vad
Keyword(s):  
Vortex Shedding ◽  
Design Guidelines ◽  
Preliminary Design ◽  
Axial Fan ◽  
Noise Emission ◽  
Blade Vibration ◽  
Low Speed ◽  
Blunt Trailing Edge ◽  
Axial Fans ◽  
Semi Empirical

Abstract The paper presents hot wire measurements in a wind tunnel, close downstream of basic models of blade sections being representative for low-speed, low-Reynolds-number axial fans, in order to explore the signatures of vortex shedding (VS) from the blade profiles. Using the Rankine-type vortex approach, an analytical model was developed on the velocity fluctuation represented by the vortex streets, as an aid in evaluating the experimental data. The signatures of profile VS were distinguished from blunt-trailing-edge VS based on Strouhal numbers obtained from the measurements in a case-specific manner. Utilizing the experimental results, the semi-empirical model available in the literature for predicting the frequency of profile VS was extended to low-speed axial fan applications. On this basis, quantitative guidelines were developed for consideration of profile VS in preliminary design of axial fans in moderation of VS-induced blade vibration and noise emission.

A Criterion for the Preliminary Design of High-Efficiency Tube-Axial Fans

2016 ◽  
Author(s):  
Massimo Masi ◽  
Stefano Castegnaro ◽  
Andrea Lazzaretto
Keyword(s):  
High Efficiency ◽  
Low Cost ◽  
Pressure Rise ◽  
Maximum Size ◽  
Industrial Applications ◽  
Design Criterion ◽  
Preliminary Design ◽  
Axial Fan ◽  
Axial Fans ◽  
Analytical Formulas

Tube-axial fans are widely used in industrial applications because of their compactness, simplicity, and low cost. However, the achievable fan pressure rise is generally penalised by the absence of a straightener and diffuser, and the consequent waste of tangential and axial dynamic pressures at the fan outlet. The corresponding fan efficiency drop might not comply with stringent regulations like the European Directive for energy-related products. Thus, operation ranges of high efficiency need to be clearly defined in the preliminary design phase, especially when constraints on maximum size and/or rotational speed are imposed. This paper proposes analytical formulas and charts to evaluate the efficiency of the tube-axial fan configuration (with or without tail-cone diffuser) when constraints on fan size and/or speed are additional design requirements. The analytical formulas and charts have been validated against experimental data. On this basis, a preliminary design criterion is suggested for high-efficiency tube-axial fans featuring arbitrary vortex design blades of constant swirl type. The criterion is used to design a 315 mm low-to-medium pressure tube-axial fan that is able to operate at a constant aeraulic efficiency peak of approximately 0.6 for blade positioning angles in the range 20° to 30°.

Opioid crisis in primary care? An audit of high-dose opioid prescribing at Bangholm GP Practice

2020 ◽  
Vol 70 (suppl 1) ◽  
pp. bjgp20X711581
Author(s):  
Charlotte Greene ◽  
Alice Pearson
Keyword(s):  
Chronic Pain ◽  
Back Pain ◽  
Practice Guidelines ◽  
Best Practice ◽  
Evidence Base ◽  
High Dose ◽  
Opioid Prescription ◽  
Opioid Prescribing ◽  
Best Practice Guidelines

BackgroundOpioids are effective analgesics for acute and palliative pain, but there is no evidence base for long-term pain relief. They also carry considerable risks such as overdose and dependence. Despite this, they are increasingly prescribed for chronic pain. In the UK, opioid prescribing more than doubled between 1998 and 2018.AimAn audit at Bangholm GP Practice to understand the scale of high-strength opioid prescribing. The aim of the audit was to find out if indications, length of prescription, discussion, and documentation at initial consultation and review process were consistent with best-practice guidelines.MethodA search on Scottish Therapeutics Utility for patients prescribed an average daily dose of opioid equivalent ≥50 mg morphine between 1 July 2019 and 1 October 2019, excluding methadone, cancer pain, or palliative prescriptions. The Faculty of Pain Medicine’s best-practice guidelines were used.ResultsDemographics: 60 patients (37 females), average age 62, 28% registered with repeat opioid prescription, 38% comorbid depression. Length of prescription: average 6 years, 57% >5 years, 22% >10 years. Opioid: 52% tramadol, 23% on two opioids. Indications: back pain (42%), osteoarthritis (12%), fibromyalgia (10%). Initial consultation: 7% agreed outcomes, 35% follow-up documented. Review: 56% 4-week, 70% past year.ConclusionOpioid prescribing guidelines are not followed. The significant issues are: long-term prescriptions for chronic pain, especially back pain; new patients registering with repeat prescriptions; and no outcomes of treatment agreed, a crucial message is the goal is pain management rather than relief. Changes have been introduced at the practice: a patient information sheet, compulsory 1-month review for new patients on opioids, and in-surgery pain referrals.

scholarly journals Introducing New Guidelines on Geoheritage Conservation in Protected and Conserved Areas

Geoheritage ◽  
2021 ◽  
Vol 13 (2) ◽  
Author(s):  
Roger Crofts ◽  
Dan Tormey ◽  
John E. Gordon
Keyword(s):  
Practice Guidelines ◽  
Best Practice ◽  
Communication To The Public ◽  
The Public ◽  
Best Practice Guidelines ◽  
The World ◽  
New Guidelines ◽  
The Many ◽  
Ethical Basis ◽  
Improve Practice

AbstractThis paper introduces newly published guidelines on geoheritage conservation in protected and conserved areas within the “IUCN WCPA Best Practice Guidelines” series. It explains the need for the guidelines and outlines the ethical basis of geoheritage values and geoconservation principles as the fundamental framework within which to advance geoheritage conservation. Best practice in establishing and managing protected and conserved areas for geoconservation is described with examples from around the world. Particular emphasis is given to the methodology and practice for dealing with the many threats to geoheritage, highlighting in particular how to improve practice for areas with caves and karst, glacial and periglacial, and volcanic features and processes, and for palaeontology and mineral sites. Guidance to improve education and communication to the public through modern and conventional means is also highlighted as a key stage in delivering effective geoconservation. A request is made to geoconservation experts to continue to share best practice examples of developing methodologies and best practice in management to guide non-experts in their work. Finally, a number of suggestions are made on how geoconservation can be further promoted.

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