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后缘襟翼气动载荷计算是大型运输类飞机增升装置设计工作中的关键步骤之一。在新型民用运输机的研制与适航取证工作中,发现现有的襟翼载荷计算方法在某些特殊工况下并非足够保守。某型支线客机襟翼测压试飞中测得其巡航构型下襟翼气动载荷相对计算值有较为明显的增加。在分析对比了试飞与风洞试验的压力分布数据,并借助CFD工具进行定性分析后,最终证明气动载荷的增加主要由襟翼舱的密封失效所造成。以往载荷计算时,襟翼舱内部的襟翼表面压力通常赋值为0,这在襟翼舱保持密封时是可靠的;但在实际飞行中,襟翼舱处襟翼与机翼主翼面后缘之间的密封装置通常会由于制造或受载变形等原因失效,此外该位置附近的扰流板也会在飞行时浮动或偏转,这些都会导致襟翼舱内部气压降低到当地外界的静压值,使得巡航构型襟翼压力分布在头部有一个较为明显的平台式增加。另一型单通道干线客机通过低速风洞测压试验发现在小襟翼偏度构型时襟翼的法向气动力系数有明显增加,采用该试验结果作为输入,计算得到的考虑扰流板偏转影响的小襟翼偏度构型襟翼气动载荷,甚至超过了扰流板未偏转时所有增升构型下的襟翼最严重载荷。通过对压力分布数据及CFD计算得到的二维流场的分析,证明扰流板偏转造成襟翼载荷增加的主要原因是前者对后者的上洗效应。扰流板的偏转将增加其下游襟翼处的当地迎角,使得后者在小偏度时就接近其在大偏度时的法向力系数,之后由于小襟翼偏度构型时更大的襟翼设计速度与对应速压最终造成了载荷增加。针对上述两个问题提出了符合客观流动规律的方法进行补充和修正:在计算巡航构型襟翼载荷时,可在原有测压试验得到襟翼压力分布的基础上补充平顶型前缘分布作为载荷计算输入;而在计算小襟翼偏度增升构型襟翼载荷时,则可以采用工程方法预估扰流板偏转带来的载荷增量。上述方法已在实际工作中得到验证和应用。
Trailing edge flap aerodynamic load calculation is one of the key steps in the design of a large transport aircraft lifting device. In the development of new civil transport aircraft and airworthiness certification, found that the existing method of calculating the flap load in some special conditions is not enough conservative. A certain type of regional passenger aircraft flap pressure measurement test measured the cruise configuration of the flap under the aerodynamic load relative to the calculated value of a more significant increase. After analyzing and comparing the pressure distribution data of test and wind tunnel tests and carrying out qualitative analysis with CFD tools, it is finally proved that the increase of aerodynamic load is mainly caused by the failure of the sealing of the flap cabin. In past load calculations, the flap surface pressure inside the flap cabin is usually assigned a value of 0, which is reliable when the flap cabin remains sealed; however, in actual flight, the flaps of the flap bay wing and the trailing edge of the main wing of the wing The seal between them usually fails due to manufacturing or load deformation, etc. In addition, the spoiler near this position will also float or deflect during flight, which will lead to the pressure drop inside the flap cabin to the static pressure outside the local environment , So that cruise configuration flap pressure distribution in the head there is a more obvious platform-type increase. Another type of single-channel mainline passenger aircraft through low-speed wind tunnel manometry test found that in the small flaps deflection flaps normal aerodynamic coefficient has increased significantly, using the test results as input, the calculated spoiler Deflection-affected small-flap skewed flap aerodynamic loads exceed the most severe flaps in all ascent configurations with spoiler deflected. Through the analysis of the pressure distribution data and the two-dimensional flow field calculated by CFD, it is proved that the main cause of the increase of the flap load caused by the deflection of the spoiler is the washing effect of the former on the latter. The deflection of the spoiler increases the local angle of attack at its downstream flaps such that the latter approaches the normal force coefficient at large deviations at low deviations and then increases due to the small flap deflection The large flaps design speed and the corresponding speed pressure eventually caused the load to increase. In order to solve the above two problems, a new method that meets the objective law of flow is proposed to supplement and revise. In calculating the load of cruise configuration flaps, the flat-top front distribution can be supplemented based on the flap pressure distribution obtained from the original pressure measurement Load calculation input; and in the calculation of small flaps skew increase configuration flap load, you can use engineering methods to predict spoiler deflection caused by the load increment. The above method has been verified and applied in practical work.