Incorporation of forward blade sweep in preliminary controlled vortex design of axial flow rotors

Vad, János

doi:10.1177/0957650912443445

Cited by 19 publications

(26 citation statements)

References 23 publications

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“…rot , D and S from equation (6) in which aer is the experimentally measured value. If the natural recovery of static pressure and swirl component at rotor outlet is conservatively assumed to be null (i.e.…”

Section: The Value Of E S Is Then Used To Obtain Estimates Ofmentioning

confidence: 99%

Forward sweep to improve the efficiency of rotor-only tube-axial fans with controlled vortex design blades

Masi

Castegnaro

Lazzaretto

2016

Proceedings of the Institution of Mechanical Engineers, Part A:

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Rotor-only axial fans feature rotors designed according to different vortex criteria. Nowadays the literature does not exhaustively clarify when a specific swirl distribution has to be used and which are the advantages/drawbacks in terms of fan performance and efficiency. A review of the experimental performance of rotor-only axial fans designed with different vortex criteria is summarized here in Φ − Ψ and σ − δ (specific speed-specific diameter) graphs to identify the best operating conditions of each design. Four rotor-only axial fans (two free-vortex, a constant-swirl and a rigid-body swirl one) are tested on an ISO-5801-A rig. For two of them, flow velocities at rotor exit are measured with a 5-hole probe. The result is an experimentally based map around the Cordier curve for rotor-only axial fans. Indications on the best Φ − Ψ range for fans designed using different vortex criteria are provided and explained. The effects of increasing the tip clearance on the rotor performance at design duty are investigated as well. KEYWORDS Rotor-only axial fans, Vortex criteria, Axial-fan design, Arbitrary vortex, Non-Free Vortex, Cordier curve NOMENCLATURE const generic constant c chord length [mm] c tip tip chord length [mm] r radius [m] R tip radius [m] tc tip clearance [mm] D fan diameter [m] b c airfoil camber [%] T aerodynamic rotor torque [Nm] q v flow-rate [m 3 /s] c u local swirl velocity [m/s] c a2 local axial velocity [m/s] c a = qv π D 2 4 ·(1−ν 2) mean axial velocity [m/s] v m = qv π D 2 4 velocity at fan exit [m/s] n rotational speed [rpm] Re tip = ρ·(πnD 60)·c tip µ Reynolds number DF Lieblein Diffusion Factor FVP = 1 2 ρv 2 m fan velocity pressure [Pa] ∆p t−s fan total-to-static pressure rise [Pa] OPEN ACCESS Downloaded from www.euroturbo.eu 1 Copyright c ⃝ by the Authors FTP=∆p t−s +FVP fan total pressure [Pa] ν hub-to-tip ratio ω angular velocity [rad/s] Φ = qv (π D 2 4)(πnD 60) flow-rate coefficient Ψ = (F T P or ∆p t−s) 1 2 ρ(πnD 60) 2 pressure coefficient η = (F T P or ∆p t−s)·qv T ·ω efficiency σ = n·q 0.5 v F T P 0.75 specific-speed δ = D·F T P 0.25 q 0.5 v specific-diameter ρ air mass density [kg/m 3 ] ξ stagger angle (with respect to fan axis) [ • ] µ air dynamic viscosity [Pa s] Γ circulation [m 2 /s] Σ a = c a2 ca dimensionless axial velocity ϵ s = cu ca dimensionless tangential velocity INTRODUCTION In this paper the performance of 30 rotor-only axial fan designed according to different vor-tex criteria is analyzed with the aim of providing fan designers with indications on the suitable choice of swirl distribution for a given duty. The rotor-only configuration is largely the most common for low-to-medium pressure-rise axial-fan applications. In this layout fixed vanes and diffuser are absent and the only aerodynamic components are the impeller and the external casing. The resulting simplicity corresponds to cheapness of purchase and maintenance but it is paid with the loss of the dynamic pressures associated with the axial and tangential velocities at rotor exit (except the small amounts con...

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Section: The Value Of E S Is Then Used To Obtain Estimates Ofmentioning

confidence: 99%

Forward sweep to improve the efficiency of rotor-only tube-axial fans with controlled vortex design blades

Masi

Castegnaro

Lazzaretto

2016

Proceedings of the Institution of Mechanical Engineers, Part A:

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“…In reference [8], Vad proposed a preliminary CVD method, harmonizing the angle of forward sweep with the spanwise circulation distribution for total efficiency improvement. This can be achieved, farther away from the endwalls, by means of shortening the flow path length on the blade suction side in order to minimize the total pressure loss at prescribed isentropic total pressure rise.…”

Section: Introduction and Objectivesmentioning

confidence: 99%

Efficiency gain of low-speed axial flow rotors due to forward sweep

Vad

Halász

Benedek

2014

Proceedings of the Institution of Mechanical Engineers, Part A:

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The paper aims at discovering the relationship between the spanwise gradient of blade circulation and the total efficiency gain due to forward sweep, in the case of low-speed axial flow fans, at the design point. For this purpose, an extensive set of literature data have been processed and evaluated by statistical means. A trend function has been established for quantifying the aforementioned relationship. By such means, it has been pointed out that the efficiency gain due to forward sweep tends to increase with the spanwise gradient of blade circulation. This means that the purposeful incorporation of forward sweep in the design process offers an increased potential for efficiency improvement in the case of rotors of controlled vortex design. The maximum efficiency gain has been observed to be 2 to 3 percent, due to an in-house developed design method. It has been noted that the efficiency improvement due to forward sweep tends to be minor for free-vortex rotors. Furthermore, the efficiency tends to deteriorate if spanwise decreasing blade circulation occurs in forward-swept rotors. Remarks have been made on the means of simultaneous reduction of loss and noise related to low-speed axial fans, for a prescribed aerodynamic performance.

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“…More recently, tunnel ventilation fan designers have started to utilise computational fluid dynamics analyses at the beginning of the design process. Vad [4] and Corsini et al [5] have proposed the application of computational methods in the fan design process. They have developed a family of high-performance swept fans for mine ventilation by feedingback the three-dimensional design criterion with computed aerodynamic data which provides insight into the size and nature of rotor secondary flows.…”

Section: Introductionmentioning

confidence: 99%

The Conceptual Design of High Pressure Reversible Axial Tunnel Ventilation Fans

Sheard¹,

Daneshkhah²

2012

Advances in Acoustics and Vibration

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Tunnel ventilation fans, classically, must have the ability to both supply and extract air from a tunnel system, with the operator's choice dependent on the tunnel ventilation system's operating mode most appropriate at any given point in time. Consequently, tunnel ventilation fans must incorporate a reversible aerodynamic design which limits the maximum fan pressure rise. This paper presents three high pressure reversible fan concepts. These comprise a two-stage counter rotating fan, a single-stage high speed fan, and a two-stage fan with a single motor and impeller on each end of the motor shaft. The authors consider the relative merits of each concept. The third concept offers the most compact fan, transform, silencer, and damper package size. The authors discuss the mechanical design challenges that occur with a two-stage fan with a single motor and impeller on each end of the motor shaft. They present and consider a selected motor bearing arrangement and casing design for maintainability. Finally, the authors present both prototype fan and full-scale package aerodynamic and acoustic performance, before discussing the challenges presented by high temperature certification in accordance with the requirements of EN 12101-3: 2012.

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Incorporation of forward blade sweep in preliminary controlled vortex design of axial flow rotors

Cited by 19 publications

References 23 publications

Forward sweep to improve the efficiency of rotor-only tube-axial fans with controlled vortex design blades

Forward sweep to improve the efficiency of rotor-only tube-axial fans with controlled vortex design blades

Efficiency gain of low-speed axial flow rotors due to forward sweep

The Conceptual Design of High Pressure Reversible Axial Tunnel Ventilation Fans

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