脉冲激光推进的能量相似律理论研究

激光推进的能量相似律,指确定的激光能量有与之相对应的最佳喷管尺寸,使得冲量耦合系数最大且不变的规律。用大气高度参数、入射的激光能量、喷管几何参数构造了无量纲因子,建立了圆锥形喷管在单脉冲条件和一维球对称点聚焦情况下的能量相似律。结果表明:当锥角固定时,冲量和冲量耦合系数存在极大值,极大值对应的无量纲因子仅与气体比热比相关;当无量纲因子固定时,冲量随入射激光能量增加而单调增大,冲量耦合系数则与能量无关。本文的研究结论和规律性认识,对目前可实现和以后工程化放大的激光能量范围,均能给出可信可靠的喷管优化尺寸。     

抛物形喷管的激光推进能量相似律数值研究

针对吸气式抛物形喷管,通过辐射输运方程和流体力学方程联立求解,计算激光能量沉积过程中的爆轰波流场,并采用高温平衡气体模型计算后续的激波流场,得到了不同构形的喷管在不同条件下的冲量和冲量耦合系数。提炼了耦合多种影响因素的无量纲因子,讨论了入射激光能量和喷管构形对推进性能参数的影响,建立了抛物形喷管激光推进的能量相似律。结果表明:当顶点到出口最外侧点连线和对称轴的夹角固定时,冲量和冲量耦合系数随无量纲因子先增大后减小,在0.37附近取得极大值;当无量纲因子固定时,冲量和冲量耦合系数均随夹角增大而减小,冲量随入射激光能量增加而增大,冲量耦合系数受能量的影响程度很小。     

Investigation on Mechanism of Altitude Characteristic for Air-breathing Pulsed Laser Thruster

Altitude characteristic is of great importance for studying when an air-breathing pulsed laser thruster works in the dense atmosphere condition of 0-30 km altitude. The experimental findings all over the world show that the similar relationship between impulse coupling coefficient and altitude. According to strong explosion theory and an ideal gas model, a dimensionless factor indicating energy law of similitude is introduced, and formula of impulse coupling coefficient is deducted. Then theoretical study of altitude characteristic is carried out and mechanism of altitude characteristic is further explained. The results indicate that there is a maximum value of impulse coupling coefficient if the dimensionless factor equals to 0. 41 in theory, and whether the phenomena of maximum appear or not depends on the range of the dimensionless factor related to altitude. As to a conical nozzle with the fixed length of 120 mm, the relationship between the sonic velocity and the dimensionless factor causes the maximum phenomenon at the altitude of about 12. 5 km, and maximum theoretical impulse coupling coefficient is also found in the experimental investigations. The mechanism of altitude characteristic for air-breathing pulsed laser thruster is discovered in this article, which will provide reference for further research on altitude characteristic.     

吸气式激光推力器概念设计

以发射10kg级微小卫星为航天任务背景,基于地面推力1000N的设计指标,分析了吸气式激光推进的主要性能参数,依据所建立的激光推进能量相似律理论和数值计算研究结果,对激光参数、聚焦系统和喷管子系统进行设计,完成了封闭的吸气式激光推力器概念设计循环。所提出的二次反射聚焦系统与抛物形喷管组合的吸气式激光推力器概念模型经数值计算程序验证,可以获得地面500N/MW的冲量耦合系数。所提出的设计理论和方法对激光推力器概念设计有一定的参考价值,是研制激光推力器模型的重要基础。     

聚焦方向对吸气式激光推进冲量耦合系数的影响

为了获得吸气式激光推进冲量耦合系数随聚焦方向的变化规律,针对抛物形喷管,采用光线追踪法求解辐射输运方程,通过与二维轴对称辐射流体动力学方程组联立,计算得到了3组单脉冲激光能量条件下不同聚焦方向对应的冲量耦合系数。计算结果表明:当聚焦方向在0°～135°范围内变化时,冲量耦合系数总体上呈下降趋势,而且激光能量较大时,这种趋势愈明显。     

飞机易损性计算中的射击线几何描述方法(英文)

本文提出了一种飞机易损性计算中的射击线几何描述方法。首先,将给定打击方向上的飞机暴露面积划分为三个子区域:非易损区域、非重叠易损区域和重叠易损区域。然后,把飞机的独立存在状态划分为三类:杀伤状态、中间状态和非杀伤状态,利用射击线扫描法,对以上三个子区域中的飞机存在状态参数进行分析。最后,该方法提供两类射击线几何描述数据:(1)每个子区域内部件的易损面积和暴露面积,这些数据主要用于计算部件的单击中易损性;(2)飞机的独立存在状态及各个状态对应的面积,这些数据主要用于计算飞机的单/多击中易损性。算例分析表明,所提出的方法通过跟踪射击线运动路径,可以提供飞机及部件被威胁命中部分的面积参数,从而使易损性计算更具有真实性。同时,该方法解决了目前方法在考虑部件重叠时的通用性问题,所提供的几何描述数据形式简单,易于分析人员使用。     

喷管构形对多脉冲激光推进冲量耦合系数的影响

多脉冲激光推进中,后续脉冲的推进性能受到之前激波流场的影响。为了获得喷管构型参数对多脉冲推进性能的影响规律,针对圆台形喷管构形,数值模拟了频率为20,50,100Hz时多脉冲流场演化过程,得到了喷管顶部直径和长度对多脉冲冲量耦合系数的影响规律。结果表明：多脉冲冲量耦合系数随着顶部直径的增加而增加;一定范围内增加喷管长度利于冲量耦合系数的提高,但喷管过长将不利于喷管内气体的恢复,多脉冲冲量耦合系数提高不明显;不同频率下顶部直径和长度对冲量耦合系数的影响规律基本一致。研究结果为多脉冲条件下喷管参数优化和实验参数选择提供参考。     

7一种双S形进气道流场特性殛控制的试验研究

In order to provide the line of-sight blockage of the engine face for an advanced Uninhabited Combat Air Vehicle(UCAV), a highly curved serpentine inlet is proposed and experimentally studied. Based on the static pressure distribut ion measurement along the wall, the flow separation is found at the top wall of the second S duct for the baseline inlet design, which yields a high flow distortion at the exit plane. To improve the flow uniformity, a single array of vortex generators (VGs) is employed within the inlet. In this experimental study, the effects of mass flow ratio, free stream Mach number, angle of attack and yaw on the performance of a serpentine inlet instrumented with VGs are obtained. Results indicate: (1) Compared with the baseline serpentine design without flow control the application of the VGs promotes the mixing of core flow and the low momentum flow in the boundary layer and thus prevents the flow separation. Under the design condition, the exit flow distortion (

) decreases from 11. 7% to 2.3% by using the VGs. (2) With the descent of the free stream Mach number the total pressure loss decreases. How ever, the circular total pressure distortion increases. When the angle of attack rises from - 4° to 8°, the total pressure recovery and the circular total pressure distortion both go down. In addition, with the increase of yaw the total pressure recovery is fairly constant, while the circular total pressure distortion ascends gradually. (3) When Ma₀=0.6-0.8, α= −4°-8° and β= 0°-6°, the total pressure recovery varies between 0.936 and 0.961, the circular total pressure distortion coefficient varies between 1.4% and 5.4% and the synthesis distortion coefficient has a ranges from 3.8% to 7.0%. The experimental results confirm the excellent performance of the newly designed serpentine inlet incorporating VGs.     

能量密度对水工质激光推进性能的影响

当辐照激光能量密度不是很高时,在分析水工质激光推进基本物理过程的基础上,只考虑汽化过程对冲量形成过程的贡献,用一维理论模型研究了辐照激光能量密度对冲量耦合系数、比冲、能量转化效率等推进性能参数的影响规律。结果表明,随着辐照激光能量密度的增加,存在一个获得最大冲量耦合系数的最优能量密度;比冲随着能量密度的增加而变大;对于透射率一定的工质而言,随着能量密度增大,能量转化效率趋于一个恒定值。这一理论研究结果对下一步的实验研究工作具有较好的指导意义。     

平行四边形截面的旁路式双喉道气动矢量喷管数值研究

将异型出口设计与气动推力矢量喷管结合,提出了平行四边形截面的旁路式双喉道气动矢量喷管(bypass dual throat nozzle,BDTN),并与基准矩形截面的BDTN进行流场结构及气动性能的对比研究。三维数值计算表明:平行四边形构型与矩形构型具有相同的气动性能变化规律;相较于基准矩形BDTN构型,由于壁面倾斜导致流场结构变化,平行四边形构型在矢量状态下的俯仰矢量角及推力系数有所降低,但对非矢量状态下的推力系数和流量系数影响不大;壁面倾角是性能变化的重要因素,相同落压比时壁面倾角越小,矢量角越小,壁面倾角不小于60°时喷管的稳定矢量角均可达10°以上,最大矢量角均可达15°以上;平行四边形出口增强了尾喷流与环境气流的掺混,出口射流中心线速度衰减大大加快,有利于提高红外隐身特性。