闲时用软件motocalc测算了一下i90的飞行参数,所配置是用国内的双天(Dualsky)电机和6s 4500mAh电池+apc 16*10桨,以下是软件设置的贴图,烦请各位帮我看看设置上有什么问题,还想知道motocalc的测算和实际的情况会有多大出入. thanks!
1)主要参数
主要是桨的参数设置, P.Const(桨常数)和拉力常数(T.Const)的选择有没有问题,更深入点,这两个东西的含义是什么?
机翼参数,主要是AoA设定,按理说应当设小点,F3A飞机的主翼安装角0.1几,平尾安装角负的零点几,如果这里的AoA设为1或2,平飞时产生的升力就太小,以至托不起飞机,所以飞行时要带点杆,使飞行时的迎角增大些,获得足够升力.
2)计算报告
从上面的报告看,电池的电流不高,最大功率输出243w/kg, 远低于彭教授的550w/kg的F3A机要求,但motor的效率较高,mot Ef在整个范围内效率是87.4%~ 91.4%, 66%动力以最佳迎角可以飞行42分钟.
3)系统建议
MotOpinion - I90-dualsky5060ca9-6s-apc1610
0.9m above Sea Level, 101.3kPa, 25度
Motor: Dualsky XM5060CA-9; 345rpm/V; 1.05A no-load; 0.035 Ohms.
Battery: My 4500 (20C); 6 cells; 4500mAh @ 3.7V; 0.0038 Ohms/cell.
Speed Control: Castle Creations Phoenix 80; 0.001 Ohms; High rate.
Drive System: APC 16-Inch Propellers; 16x10 (Pconst=1.24; Tconst=1) direct drive.
Airframe: Fliton Inspire 90; 51dm? 3446g; 67.6g/dm? Cd=0.042; Cl=0.14; Clopt=0.44; Clmax=0.89.
Stats: 278 W/kg in; 243 W/kg out; 11.6m/s stall; 16.5m/s opt @ 66% (42:43, 37度); 29.7m/s level; 11.95m/s @ 46.5? -2.2m/s @ -7.7?
Warning:
MotoCalc was unable to determine a throttle setting for hands-off cruise airspeed, so the best lift-to-drag ratio airspeed and throttle setting will be used instead.
Inability to determine a throttle setting for an airspeed usually means the model is not capable of reaching the required speed with the given power system, or the airfoil information has not been specified correctly.
Power System Notes:
The full-throttle motor current at the best lift-to-drag ratio airspeed (40.7A) falls approximately between the motor's maximum efficiency current (25.2A) and its current at theoretical maximum output (303.8A), thus making effective use of the motor.
The voltage (21.1V) exceeds 12V. Be sure the speed control is rated for at least the number of cells specified above.
Possible Aerodynamic Problems:
The static pitch speed (27.6m/s) is less than 2.5 times the stall speed (11.6m/s), which may result in reduced performance at typical flying speeds and a low maximum speed. This situation is usually acceptable for an electric sailplane or other slow-flying model.
Pitch speed can be increased by using a higher pitched and/or smaller diameter propeller, a higher cell count, or some combination of these methods.
Aerodynamic Notes:
With a wing loading of 67.6g/dm? a model of this size will have trainer-like flying characteristics. It would make an ideal trainer, for use in calm to light wind conditions.
The static thrust (4457g) to weight (3446g) ratio is 1.29:1, which will result in extremely short take-off runs, no difficulty taking off from grass surfaces (assuming sufficiently large wheels), and vertical climb-outs. This model will probably be able to perform a hover or torque roll.
At the best lift-to-drag ratio airspeed, the excess-thrust (2491g) to weight (3446g) ratio is 0.72:1, which will give very steep climbs and incredible acceleration. This model can easily do consecutive loops, and has sufficient in-flight thrust for any aerobatic maneuver.
General Notes:
This analysis is based on calculations that take motor heating effects into account.
These calculations are based on mathematical models that may not account for all limitations of the components used. Always consult the power system component manufacturers to ensure that no limits (current, rpm, etc.) are being exceeded.
要换个大点螺距的桨,桨后的气流相对速度(最大)不在飞机失速速度的2.5到3的范围内,对飞行时的性能有影响,为什么呢?要查查资料.
拉重比1.29:1,垂直爬升看来是没有问题,但此时只有243w/kg的功率输出,为什么还要500多瓦/kg的功率输出呢?看来还要请彭大大来解惑.
motocalc的计算模型和实际效果到底有多大差别,应该怎样来分析使用这个软件,这是我最关心的问题,真要请各位有经验的飞友们出来指导了.
[ 本帖最後由 pandy 於 2009年5月7日 11:25 AM 編輯 ] |
樓主: pandy
發表於 2009年4月22日 04:46 PM
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