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FIELD OF INVENTION
The present invention relates to a narrow width Backward Aerofoil bladed Radial fan adaptable to utilities and process industries in general and Primary Air handling Application in particular for better part load performance.
BACKGROUND OF THE INVENTION
Fan is a Turbo machine designed to deliver a given volume and pressure to meet the system requirement.
Fans are very essential auxiliaries to boiler for steam generation in the field of Power & Process Industries. Fans are used as Forced Draft Fan for providing air for combustion, Primary Air fan for carrying pulverized coal to combustion chamber & Induced Drat Fans for exhausting the flue gases to Chimney as per the system requirement. The application requirements can be catered by radial and axial flow fan. Suitable control mechanism is used to regulate the fan performance to meet system demand and to meet part load operating conditions.

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The prior art radial fan comprises an Impeller which is plate bladed design. Generally the coefficient of Lift for a blunt body like Plate bladed design will be very low and hence there will be flow separation losses, swirl & recirculation losses, which will be enormous and hence the performance of the configuration will be poor. The Impeller consists of a Back/Centre Plate, a formed Blade, a taper shroud, a ring and a hub. The impeller is placed inside a spiral casing which will act as the diffuser to recover the kinetic energy of the fluid leaving the impeller. A suction chamber uniformly guides the flow inside the fan through a seal to the impeller. The impeller is driven by a motor. The electrical energy input is converted into aerodynamic output by the rotating impeller.
OBJECTS OF THE INVENTION
It Is therefore, an object of the invention to propose a High pressure Backward Aerofoil Bladed Radial fan adaptable in utilities and process industries in general and Primary air handling Application in particular for improved performance.
Another object of the present invention is to propose a High pressure Backward Aerofoil Bladed Radial fan which is capable of handling worst coal and simultaneously reduce the power consumption at the part load design performance.

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BRIEF DESCRIPTION OF THE INVENTION
The invention proposes an improved fan in which the blade of the impeller is Backward Aerofoil Bladed having a profile with smooth entry, exit angles for high pressure application. Dimensions of the casing & suction chamber has been optimized to extract maximum kinetic energy. The damper has been configured to have wide spread of operation with easy manufacturing process.
The High pressure Backward Aerofoil bladed Fan of the invention comprises an Impeller having blades of Backward Aerofoil design.
Flow separation losses, swirl & recirculation losses are reduced in profiled shape bladed, as compared to blunt plate bladed design hence the performance of the new configuration is better. The above approach has been validated using Computational Fluid Dynamics. The new Impeller consists of Back/Centre Plate, fitted with Aerofoil Blade. The device parameters like Camber, Angle of incidence, Leading and trailing edge shapes are correspondingly determined and selected.

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The new impeller is placed inside a Spiral casing which will act as the diffuser to recover the kinetic energy of the fluid leaving from the impeller whose diffusivity angle and geometry shape are selected after detailed analysis. The number of blades and blade actuations are decided based on controllability factors.
The mechanical design of the developed fan is evolved using Finite Element Analysis.
Performance test of the new fan has been carried out to establish its aerodynamic performance. A considerable improvement in efficiency comparing with plate bladed design and considerable reduction in weight compared with conventional design has been achieved.
The new configuration caters to following design criteria.
Flow coefficient j = 0.030
Pressure Coefficient y = 1.1655
Efficiency h = 86%

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The backward aerofoil bladed design have predetermined camber, angle of incidence, leading and trailing edge. The Spiral casing acts as a diffuser to recover the kinetic energy of the fluid leaving from Impeller. The suction chamber is specific by geometry and configuration for guiding the flow through a Seal to said impeller.
The impeller is provided with rear or center plate.
The selected parameters of the camber, angle of incidence, leading & trailing edges are capable of handling high pressure.
The damper configuration caters for better controllability.
The invented fan exhibits better pressure, volume performance, reduced vibration and noise, less power consumption and improved erosion, fatique life compared to prior art machines.

The invention relates to a high pressure Backward Aerofoil Bladed Fan comprising an Impeller (01) having a plurality of backward aerofoil type blades (02), the configuration of the plurality of blades (02) is profiled in such a way that flow separation losses, swirl and recirculation losses are 'substantially reduced; the camber, angle of incidence, leading and trailing edge of the blades are correspondingly selected to match the profile of said impeller which is housed inside a Spiral casing (03) which acts as a diffuser to recover the kinetic energy of the fluid leaving from the Impeller (01) ;and a suction chamber (04) with a matching geometry and configuration for guiding the flow through a Seal
(05) to said impeller (01), wherein the fan exhibits flow-coefficient, pressure coefficient, and efficiency to the magnitude of 0.030, 1.1655, and 86% respectively.