|Title of Invention||
A CENTRIFUGAL FAN IMPELLER FOR EFFICIENT SUCTION OF GASES AND VAPOURS
|Abstract||This invention relates to a centrifugal fan impeller. It consists of two juxtoposedly positioned plates centred with a drivable hub. Backwardly curved fan blades are mounted on the facing sides of the impeller plates. The arlgles of the inlet point and the outlet poirlt of each fan blade with respect to the centre of the hub is maintained at 900.|
Thi s Invent ion rel ates to a centrifugal fan impel ler for efficient suction of gases and vapours.
Fans are used to generate continuous flow of gaseous streams aerodynamioally. Fans and blowers are used all over the world in a wide variety of industries. Some of the important appli oati ons are in steam power stations, venti1ati on systems, coo 1ing of e1ectri c motors/generators, suction of air, gas/vapour and many ot her industrial processes. The basic purpose of a fan is to move a mass of air, gas or vapour at the desired velooi ty (by the action of its rotor). For achieving this objective, a slight increase in the air/gas pressure is created across the fan rotor or impeller, but the main aim remains to move air or gas without any appreciable increase in its pressure.
Fans and blowers can be either axial, centrifuga1 or of the mi xed~flow type. A majority of low pressure fans are of the axial type whereas a large number of high pressure fan/blowers are of the centrifugal type. While centrifugal fans generate higher pressure per stage at comparatively lower flow rates, axial fans and blowers handle higher flow rates at lower pressure per stage. The centrifugal fans are further subdivided into three types denoted by the curvature or slope of the impeller blades, the angle of which largely determines the operating characteristics. The three basic types are commonly designated
as: i) forward curved blade ii ) radial blade and iii) backward curved blade. Among these three types, the backward curved blade type centrifugal fans are most widely used because they have the lowest power consumption for equal air flow and less noise in running. In the backward curved type, the blades are inolined away from the direct ion of motion. Backward curved blade impeI 1errs are employed for lower pressure and lower flow rates. The width to diameter ratio of such impellers is small .
The centri fugal fans produce pressure from two independent sources.
i) from the centrifugal force created by rotating the
enclosed air column and ii) from the kinetic energy imparted to the air by virtue of its velocity leaving the impeller.
This velocity in turn is a combination of rotative velocity of the i mpe Her and air speed relative to the , impel 1er. A fan hav ing backward-curved hiades builds up more of its pressure by centri fugal force (a more efficient form of energy transfer) and 1 ess by velocity conversi on and therefore, must run at a higher speed. With the velocities opposite in the fan hav ing backward curved blades, the energy requirement per Kg. of air is decreased. Thus, the blade angle definitely influences
the horse power requirement of a fan. Also, the sound developed by a fan Is a chracterist1e which is becoming increasingly important. The pressure rise and flow rate in centri fugal fans depend on the peripheral speed of the impeller and blade angles. The stage losses and performance also vary with the blade geometry.
The following drawbacks are associated wi t.h the existing type of centrifugal fans:
i ) the suction performance is not uniform due to turbulence i i ) the energy requirement is too high iii) the sound and vibration levels are more iv) these fans have large moment of inertia.
This often leads to problems when electric motors are used with direct on-1ine start and hence motor burn-out rate is very high v > handling during ma in tenance work is diffi cult due to heavy weight.
The ma in objects of the i nvent ion are to overcome the above drawbacks. The centrifugal fan impeller is developed to provide eff i c i ent sucti on performance to develop an energy efficient centrifnga1 fan impeller; to reduce the sound and vibration 1 evel; and to reduce the instantaneous current value for reduot ion in motor-burnout ra te .
Further, the centrifugal fan impeller developed by UR has the following advantages:
Aooiimu 1 at ion of dust is reduced; handling is very easy because of lesser weight; technical perfection is ensured due to the applioation of CAD/CAM teohn ique and are very cost effective.
The volumetric opaoi ty, pressure generation, power requirement, efficiency and peripheral speed of the impeller are primarily affected by the type of blading and blade angle; ser-ond ly by the proportions of associated fan housing, inlet, outlet and structural memebers. The impeller diameter and width are also influencing the flow rate. Moreover, the diameter ratio of the impeller determines the 1ength of the blade passage; the smaller this ratio the longer is the blade passage. For efficient suction of air, gas or vapour, the existing impeller d iameter, blade angle, blade profile and manufacturing methodologies have been changed. With the help of this invention, it is possible to improve the suction performance and reduce the energy consumption of the centrifugal fans.
The centri fugal fan impeller according to this invention consists of two impeller plates connected to a hub through a join ing ring. A olearance is provided between the hub and the plate assembly. The two impeller plates are di sposed juxtaposed to each other and are rotatably mounted on the hub. A
drivable shaft is housed within the hub and is driven by an electric motor connected thereto. A plurality of fan blades are located within the two plates. The backwardly curved fan blades nr^ fixed on to the sides of the two impeller plates juxtaposed to each other. The width of the impeller is the same throughout and is equal to the width of the blade. Blades are mounted such that the blade prof ile is unaltered and the angle between the inlet find the outlet point of each blade with the centre is maintained at right angles.
The centrifugal fan Impeller for efficient suction of gases and vapours comprises two juxtaposedly disposed impeller plates provided centrally with a driavable hub, a plurality of backwardly curved fan blades connected to the facing sides of said impeller plates, such that the angle between the inlet and the outlet point of each blade with respect to the hub centre is maintained at right angles, the width of said fan blades being
Ntibst.antla 1 ly the same as the width of said impeller.
The invention will now be described with reference fa figure 1 of the accompanying drawings.
The two side plates of the impeller are designated reference numeral 1 and 2 respectively. The hub is shown by numeral 4 and the .joining ring is indicated by numera 1 P>. The
arrows designated by I and 0 show the inlet and the outlet points for the gases/vapour. The backwardly curved fan blades are shown by numeral 3. Angles AOB and COD are maintained at 90° so as to effect maximum efficiency while the blades are rotated. Shaft and the motor being conventional and known are not shown in the figures. It is observed that the blade number can range from 2-62.
Though a npeci f io embodiment has been described hereinabove, alterations and modifications known to persons skilled in the art are not excluded from the appended claims.
1 A centrifugal fan impeller for efficient suction of
gases and vapours comprising two jiuxtaposedly disposed impeller plates (1,2) provided centrally with a drivable hub (4), a plurality of backwardly curved fan blades (3) connected to the facing n idea of said i mpeller piates, such that the angle (AOB, COD) between the inlet point and outlet point of each blade with respect to the hub centre is maintained at right angles, the width of said fan blades being substantially the same as the width of sa id impeller.
2, The centrifugal fan impeller as claimed in claim 1,
wherein the hub is connected to said impeller plate through a
3, The centrifugal fan impeller as claimed in claims 1 and
2, wherein a drivable shaft is housed inside the hub.
4, The centrifugal fan impeller as claimed in claim 1
wherein a minimum of two and a maximum of 62 backwardly curved
blades are provided.
5. A centrifugal fan impeller for efficient Ruction of gases and vapours substantially as herein described with particular reference to figure 1 of the accompanying drawings.
|Indian Patent Application Number||187/MAS/1999|
|PG Journal Number||44/2007|
|Date of Filing||15-Feb-1999|
|Name of Patentee||THE SOUTH INDIA TEXTILE RESEARCH ASSOCIATION|
|Applicant Address||COIMBATORE AERODROME POST, COIMBATORE 641 014|
|PCT International Classification Number||F04D29/28|
|PCT International Application Number||N/A|
|PCT International Filing date|