Method for designing a multiblade radial fan and a multiblade radial fan

A multiblade radial fan comprising an impeller and a scroll type casing, wherein the impeller and the scroll type casing to satisfy the formula:

• .theta..sub.z =tan.sup.-1 {0.295.epsilon.(1-nt/(2.pi.r))(H/H.sub.t).xi..sup.1.641 }
• where 0.75.ltoreq..epsilon..ltoreq.1.25, n=a number of the radially directed blades, t=a thickness of the radially directed blades, r=an outside radius of the impeller, H=a height of the radially directed blades, H.sub.t =a height of the scroll type casing, .xi.=a diameter ratio of the impeller, .theta..sub.z =a divergence angle of the scroll type casing.

A method for making a multiblade centrifugal fan comprising an impeller having a plurality of blades circumferentially spaced from each other and a scroll type casing accommodating the impeller, comprising forming the scroll type casing such that a tongue located at or outside a radial position where a ratio of a half band width of a jet flow discharged from an interblade channel to a virtual interblade pitch is a certain value near 1.

A method for making a multiblade centrifugal fan comprising an impeller having a plurality of blades circumferentially spaced from each other and a scroll type casing accommodating the impeller, comprising forming the scroll type casing such that a tongue located at or outside a radial position where a ratio of a half band width of a jet flow discharged from an interblade channel to a virtual interblade pitch at a radial position where half band widths of two adjacent jet flows discharged from two adjacent interblade channels are equal to a virtual interlade pitch is a certain value near 1.

A method for making a multiblade centrifugal fan comprising an impeller having a plurality of blades circumferentially spaced from each other and a scroll type casing accommodating the impeller, wherein the impeller and the scroll type casing are formed to satisfy the formula:

• -A.tau.+B<10.0
• where .tau.=b/.delta..sub.3, b=(.delta..sub.3 -c)(C.sub.d /X)+c, c=C.delta..sub.1, .delta..sub.1 ={(2.pi.r)/n}-t, .delta..sub.3 =2.pi.(r+X)/n, C.sub.d =a tongue clearance, n=a number of the blades, t=a thickness of the blades, r=an outside radius of the impeller, and A, B, C, X=constants determined through tests.

A method for making a multiblade centrifugal fan comprising an impeller having a plurality of blades circumferentially spaced from each other and a scroll type casing accommodating the impeller, wherein the impeller and the scroll type casing are formed to satisfy the formula:

• -47.09.tau.+50.77<10.0
• where .tau.=b/.delta..sub.3, b=(.delta..sub.3 -c)(.sub.d /X)+c, X=0.8.delta..sub.2, c=0.3.delta..sub.1, .delta..sub.1 ={(2.pi.r)/n}-t, .delta..sub.2 =2=(2.pi.r)/n, .delta..sub.3 =2.pi.(r+X)/n, C.sub.d =a tongue clearance, n=a number of the blades, t=a thickness of the blades, r=an outside radius of the impeller.

A multiblade centrifugal fan comprising an impeller having a plurality of blades circumferentially spaced from each other and a scroll type casing accommodating the impeller, wherein the scroll type casing further comprises a tongue located at or outside the a radial position where a ratio of a half band width of a jet flow discharged from an interblade channel to a virtual interblade pitch is a certain value near 1.

A multiblade centrifugal fan comprising an impeller having a plurality of blades circumferentially spaced from each other and a scroll type casing accommodating the impeller, wherein the scroll type casing further comprises a tongue located at or outside a radial position where a ratio of a half band width of a jet flow discharged from an interblade channel to a virtual interblade pitch at a radial position where half band widths of two adjacent jet flows discharged from two adjacent interblade channels are equal to a virtual interblade pitch is a certain value near 1.

A multiblade centrifugal fan comprising an impeller having a plurality of blades circumferentially spaced from each other and a scroll type casing accommodating the impeller, wherein the impeller and the scroll type casing satisfy the formula:

• -A.tau.+B<10.0
• where .tau.=b/.delta..sub.3, b=(.delta..sub.3 -c)(C.sub.d /X)+c, c=C.delta..sub.1, .delta..sub.1 ={(2.pi.r)/n}-t, .delta..sub.3 =2.pi.(r+X)/n, C.sub.d =a tongue clearance, n=a number of the blades, t=a thickness of the blades, r=an outside radius of the impeller, and A, B, C, X=constants determined through tests.

A multiblade centrifugal fan comprising an impeller having a plurality of blades circumferentially spaced from each other and a scroll type casing accommodating the impeller, wherein the impeller and the scroll type casing satisfy the formula:

• -47.09.tau.+50.77<10.0
• where .tau.=b/.delta..sub.3, b=(.delta..sub.3 -c)(.sub.d /X)+c, X=0.8.delta..sub.2, c=0.3.delta..sub.1, .delta..sub.1 ={(2.pi.r)/n}-t, .delta..sub.2 =(2.pi.r)/n, .delta..sub.3 =2.pi.(r+X)/n, C.sub.d =a tongue clearance, n=a number of the blades, t=a thickness of the blades, r=an outside radius of the impeller.

A method for driving an impeller of a multiblade radial fan, comprising the step of driving the impeller so as to make a flow coefficient .phi. equal to

• 0.295.epsilon.(1-nt/(2.pi.r)).xi..sup.1.641
• where 0.75.ltoreq..epsilon..ltoreq.1.25, n=a number of the radially directed blades, t=a thickness of the radially directed blades, r=an outside radius of the impeller, .xi.=a diameter ratio of the impeller.

A method for making a multiblade centrifugal fan comprising an impeller having a plurality of blades circumferentially spaced from each other and a scroll type casing accommodating the impeller, wherein the impeller and the scroll type casing are formed to satisfy the formula:

• {(.delta..sub.3 -c)(C.sub.d /X)+c}/.delta..sub.3 .gtoreq.1
• where c=C.delta..sub.1, .delta..sub.1 ={(2.pi.r)/n}-t, .delta..sub.3 =2.pi.(r+X)/n, C.sub.d =a tongue clearance, n=a number of the blades, t=a thickness of the blades, r=an outside radius of the impeller, and C, X=constants determined through tests.

A method for making a multiblade centrifugal fan comprising an impeller having a plurality of blades circumferentially spaced from each other and a scroll type casing accommodating the impeller, wherein the impeller and the scroll type casing are formed to satisfy the formula:

• {(.delta..sub.3 -c)(C.sub.d /X)+c}/.delta..sub.3 .gtoreq.0.87
• where X=0.8.delta..sub.2, c=0.3.delta..sub.1, .delta..sub.1 ={(2.pi.r)/n}-t, .delta..sub.2 =(2.pi.r)/n, .delta..sub.3 =2.pi.(r+X)/n, C.sub.d =a tongue clearance, n=a number of the blades, t=a thickness of the blades, r=an outside radius of the impeller.

A multiblade centrifugal fan comprising an impeller having a plurality of blades circumferentially spaced from each other and a scroll type casing accommodating the impeller, wherein the impeller and the scroll type casing satisfy the formula:

• {(.delta..sub.3 -c)(C.sub.d /X)+c}/.delta..sub.3 .gtoreq.1
• where c=C.delta..sub.1, .delta..sub.1 ={(2.pi.r)/n}-t, .delta..sub.3 =2.pi.(r+X)/n, C.sub.d =a tongue clearance, n=a number of the blades, t=a thickness of the blades, r=an outside radius of the impeller, and C, X=.

A multiblade centrifugal fan comprising an impeller having a plurality of blades circumferentially spaced from each other and a scroll type casing accommodating the impeller, wherein the impeller and the scroll type casing satisfy the formula:

• {(.delta..sub.3 -c)(C.sub.d /X)+c}/.delta..sub.3 .gtoreq.0.87
• where X=0.8.delta..sub.2, c=0.3.delta..sub.1, .delta..sub.1 ={(2.pi.r)/n}-t, .delta..sub.2 =(2.pi.r)/n, .delta..sub.3 =2.pi.(r+X)/n, C.sub.d =a tongue clearance, n=a number of the blades, t=a thickness of the blades, r=an outside radius of the impeller.