固液火箭发动机试验燃速的计算

基于固液火箭发动机固体药柱燃速与药柱通道氧化剂质量流率的关系,推导分析得出:在2s短工作时间内或者药柱通道直径增大10％的情况下,燃烧室压力与其氧化剂质量流量成正比.因此通过试验测量的燃烧室压力可计算得到发动机转级或者关机拖尾段中的氧化剂质量流量.据此,计算发动机拖尾段消耗的燃料质量,消除发动机拖尾段燃料消耗对平均燃速的影响,可以修正常用的计算试验燃速的起止点平均法.利用此方法对两种试验推进剂组合的燃速进行了计算,原偏高的燃速值降低约20％,不同尺寸发动机的燃速符合尺寸规律,偏差在5％以内,使小尺寸发动机测得的燃速可应用到大尺寸发动机的设计中.

Calculation of experimental regression rate of hybrid rocket motor

Combustion chamber pressure of hybrid rocket motor was estimated to be proportional to its oxidizer mass flow rate under the conditions of short work duration of less than 2s or minor variation of grain port diameter within 10%. The conclusion was deduced from the exponential relation between solid fuel regression rate of hybrid rocket motor and corresponding oxidizer mass flux. The oxidizer mass flow rate during motor throttling or shutdown was calculated through pressure curve from motor test and obtain the fuel mass consumed consequently. By eliminating the mass consumed during motor shutdown, the overestimated regression rate calculated from motor test through end point average method was improved. Regression rates of two sets of propellant were calculated through the improved method from test results. The rates reduce about 20% and the results between different motor sizes agree with the scale effect within an error of 5%. It is thusreasonable to apply the regression rate from small scale motor to the design of large scale motor design.