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.
.
. . . = = . . = . . . . . . . . . .
. = ()
. = ()
=
Cascade Nomenclature
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Effect of velocity distribution on profile drag coeff.
Common camber line shapes
Suction & Pressure Surface
Zero Lift Direction
Weinigs Lattice coefficient
= =
, ;= , =
> . > ; <
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Aerofoil representation
British Practice:
Aerofoil built around basic circular or parabolic camber line
12C4/35 P30 Denotes an aerofoil for which the maximum thickness to chord ratio(t/c) is 12%, C4 denotes
the base profile, 35 is the camber angle in degrees, P denotes a parabolic arc camber line and 30 is the
percentage of the chord from the leading edge where maximum camber occurs.
American Practice:
Series of aerofoils developed by NACA
A series of camber lines used, each associated with design lift coefficient (CLO) of a single aerofoil.
NACA 65-(12)10
Camber line corresponding to CLO=12/10=1.2 and a profile shape 65 with approximate 10% thickness.
Ordinates for other camber are obtained by direct scaling in proportion to the camber CLO
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Section of profiles in use in axial machines
Characteristics of the Clark Y profile (t/c=10%, Rec=8*105)Prepared by Dr. S. Ramamurthy, [email protected]
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Lift and Drag Characteristics of flat and cambered
Plates (t/c=0.02, Rec=3*105) adopted from Wallis
Eckerts results for axial fan(Rec=3*105, same Camber
and rotational speed) showing comparison between
the performance of cambered plate and profiled blade
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NACA 6510
C4
3-Different airfoils used in
Turbo machines
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NACA 65 series of cascade aerofoils
(L.J. Herring ,J.C. Emery and J.R. Erwin.
Courtesy NACA)
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Blades in cascade and the effectof proximity on blade performance
Data for an NACA 65(27) 10 aerofoil in cascade
(b1=450,s/c=1.0)
Note: 65(27) 10 means 65 series foil,
CLO=2.7,t/c=10%;CLO is design lift
Coefficient, related to camber angle
q as sketched
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Blade setting variables
Flow & pressure distributionover symmetrical aerofoil
Flow & pressure distributionover an inclined aerofoil
Root and tip sections of a typical
Compressor rotor blade illustratingThe degree of twist
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= + = =
, =
=
= ; =
=
+
= = =
+ = + = . =
: = Prepared by Dr. S. Ramamurthy, [email protected]
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.: = = =
. =
=
= =
=
=
= , =
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=
=
=
=
+
= =
=
+
= = =
+
=
= =
=
=
=
,
=
= = =
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Layout of a conventional low speed cascade tunnel (Lieblen) (Courtesy of NASA)
A sample plot of inlet and outlet stagnation pressures
and fluid outlet angle (adopted from Todd) Compressor cascade characteristicsDiagrammatic representationOf fluid deviation
=
=
=
= . + . :.
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:, , , incidence(i)
., =
. , = + .. .. =
. , . = = + = . ;
Fig. 1 Space chord ratio correction
For nominal deflection
Fig. 2 Reynolds number correction
For nominal deflection
Fig. 3 Nominal deflection as a
Function of nominal outlet angle
Fig. 4 Off-design performance of
cascade
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=
, =
=
=
=
=
=
=
=
=
=
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:.
. .:
.. .. , = +
< .
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, = .
, . = & = , =
= . , ,
.
Effect of staggerPrepared by Dr. S. Ramamurthy, [email protected]
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:, :,
:.
. ,
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: < , :
:
=
,
=
: > ,:
. . ,, .