Fluid reaction surfaces (i.e. – impellers) – Specific blade structure – Radial flow devices
Reexamination Certificate
2000-02-23
2001-11-13
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Specific blade structure
Radial flow devices
C416S238000, C416S242000, C416SDIG005
Reexamination Certificate
active
06315522
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a helicopter blade aerofoil and a helicopter blade.
2. Description of the Related Art
In Japanese Patent Application No. 9-30730 (Japanese Unexamined Patent Publication JP-A 10-226397 (1998)) corresponding to U.S. Pat. No. 5,961,290, the Applicant of the present invention proposed an aerofoil AK100D as the prior application having large maximum lift coefficient Clmax and lift-drag ratio and reduced noise level.
Another prior art of the helicopter blade aerofoils are known Japanese Unexamined Patent Publications JP-A 50-102099 (1975), JP-A 59-134096 (1984), JP-A 63-64894 (1988), Japanese Examined Patent Publication JP-B2 62-34600 (1987), Japanese Patent Application No. 8-52121 (Japanese Unexamined Patent Publication JP-A 9-240593 (1997)) corresponding to U.S. Pat. No. 5,957,662, etc.
The aerofoil AK100D (the prior application), having excellent lift characteristics, drag characteristics, and lift-drag characteristics, especially superior lift characteristics at low velocities, in which a reduced noise level can be achieved. However it has a tendency that the maximum lift coefficient in a middle velocity range of Mach numbers M of 0.5 to 0.6 is small.
When a helicopter with a rotor having a radius R which is rotating at a rotational angular velocity &OHgr; flies at a ground velocity V, the airspeeds of an advancing blade where the rotational speed of the rotor is added to the ground velocity V, and a retreating blade where the ground velocity V is subtracted from the rotational speed of the rotor are significantly different from each other. The operating envelope of helicopter blades thus exist in a wide range from lower velocity to higher velocity. In order to improve the performance of the rotor as a whole, therefore, it is necessary to improve the lift characteristics in wider velocity range.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a helicopter blade aerofoil and helicopter blade having a large maximum lift coefficient Clmax in wide velocity range from lower velocity to higher velocity, and a reduced noise level.
It is another object of the invention to provide a helicopter blade aerofoil and helicopter blade having a large maximum lift coefficient Clmax in a wide range form lower velocity to higher velocity, and a reduced noise level, in which pitching moment about an aerodynamic center of the aerofoil can be reduced.
The invention provides a helicopter blade aerofoil having coordinate values within ±3% errors of upper and lower surfaces on the basis of a reference aerofoil having a thickness to chord ratio of 10% (hereinafter, referred to as aerofoil AK100G), of which upper and lower surfaces are substantially defined by the following coordinates, and of which leading edge profile is substantially defined by the following leading edge radius and center of a circle:
X/C
Yup/C
Ylow/C
0.00000
0.00000
−0.00000
0.00100
0.00511
−0.00584
0.00250
0.00843
−0.00813
0.00500
0.01218
−0.01014
0.00750
0.01505
−0.01136
0.01000
0.01747
−0.01218
0.01250
0.01959
−0.01277
0.01500
0.02150
−0.01328
0.01750
0.02325
−0.01375
0.02000
0.02487
−0.01415
0.02500
0.02780
−0.01483
0.05000
0.03891
−0.01714
0.07500
0.04682
−0.01862
0.10000
0.05291
−0.01979
0.15000
0.06152
−0.02206
0.20000
0.06666
−0.02470
0.25000
0.06892
−0.02729
0.30000
0.06895
−0.02949
0.35000
0.06841
−0.03109
0.40000
0.06744
−0.03211
0.45000
0.06568
−0.03270
0.50000
0.06301
−0.03272
0.55000
0.05943
−0.03211
0.60000
0.05498
−0.03084
0.65000
0.04968
−0.02883
0.70000
0.04349
−0.02600
0.75000
0.03649
−0.02237
0.80000
0.02886
−0.01794
0.85000
0.02087
−0.01315
0.90000
0.01279
−0.00777
0.95000
0.00538
−0.00304
1.00000
0.00236
−0.00095
Leading edge radius r/C=0.0096,
Center of circle X/C=0.0097, Y/C=−0.0018,
where X is a distance from the leading edge to a trailing edge along a chord line of the aerofoil, C is a length of the aerofoil in the chord direction, Yup is a distance from the chord line to the upper surface, Ylow is a distance from the chord line to the lower surface, and r is the leading edge radius.
According to the invention, since the leading edge upper surface contour, the leading edge radius, and the camber line are optimized in comparison with a conventional symmetric blade having a thickness to chord ratio of 10% (e.g., NACA0010), the pressure distribution in the upper surface of the aerofoil is flattened, and the level of the main rotor rotational noise can be reduced by several dB from that of the prior art. Moreover, the maximum lift coefficient Clmax is greatly improved.
Moreover, the aerofoil AK100G according to the present invention can realize an improvement of the maximum lift coefficient Clmax in a wide range of velocities in comparison with an aerofoil AK100D (the prior application). Thus, the operating envelope of the helicopter blade can be extended, and the flight performance of the helicopter is improved. In particular, the maximum lift coefficient Clmax in a middle velocity range is improved, so that the hovering performance of the helicopter is greatly improved.
Furthermore, the invention provides a helicopter blade aerofoil having coordinates values with ±3% errors of upper and lower surfaces, defined by a thickness to chord ratio within a range from 8% to 15% on the basis of the aerofoil AK100G. According to the present invention, an aerofoil AK080G having a thickness to chord ratio of 8% is obtained by multiplying the values of Yup/C and Ylow/C by 8/10 for all chord lines X/C on the basis of the aerofoil AK100G having a thickness to chord ratio of 10%, and on the other hand, an aerofoil AK150G having a thickness to chord ratio of 15% is obtained by multiplying the values by 15/10. Therefore, similar effect can be achieved with any aerofoil having a thickness ratio within a range from 8% to 15%, obtained by multiplying a constant factor for the reference aerofoil (AK100G).
Furthermore, the present invention provides a helicopter blade aerofoil having coordinates values with ±3% errors of upper and lower surfaces, the helicopter blade aerofoil including, on the basis of the aerofoil AK100G, a trailing edge tab having a length of 5% to 10% of a chord length of the aerofoil and a tab angle in a range of 0 to 5 degrees in a trailing edge elevating direction with respect to a chord line in a trailing edge of the aerofoil (hereinafter, the aerofoil with such a trailing edge tab is referred to as AK100G-TAB).
According to the present invention, an aerofoil having a trailing edge tab of a predetermined length can be obtained by multiplying the aerofoil AK100G by an arbitrary reduction ratio, and adding a trailing edge tab having an arbitrary thickness.
Therefore, while maintaining the superior characteristics of the aerofoil AK100G, a pitching moment Cm can be reduced by adding a tab having a predetermined tab angle and a predetermined length to the trailing edge of the aerofoil AK100G. When the trailing tab is bent in the range of 0 to 5 degrees (in the trailing edge elevating direction), a pitching down moment reduction effect can be attained in accordance with the tab angle. The aerofoil including the trailing edge tab having a length in the range of 5 to 10% of the chord length can attain a pitching moment reduction effect in accordance with the tab length.
Furthermore, the present invention provides a helicopter blade aerofoil having coordinates values with ±3% errors of upper and lower surfaces, defined by a thickness to chord ratio within a range from 8% to 15% on the basis of the aerofoil AK100G-TAB.
According to the present invention, an aerofoil AK080G-TAB having a thickness to chord ratio of 8% is obtained by multiplying the values of Yup/C and Ylow/C by 8/10 for all chord lines X/C on the basis of the aerofoil AK100G-TAB having a thickness to chord
Inagaki Kenjiro
Tsuchihashi Akihiko
Yamakawa Eiichi
Advanced Technology Institute of Commuter-Helicopter, Ltd.
Look Edward K.
Nguyen Ninh
Wenderoth , Lind & Ponack, L.L.P.
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