Pressure produced by burned lifting charge was measured in a closed or an opened small mortar without projectile using four pressure sensors in the research. The change of pressure at the bottom of a motor, where the lifting charge is set, will instantly cause the change of pressure everywhere in the mortar because pressure propagates with speed of sound. Pressure gradient doesn't occur if the burned gas doesn't flow out, but pressure gradient occurs in the mortar otherwise. The pressure before and behind the projectile in the mortar is more complex when the burned gas flows out through the gap between projectile and mortar. Further, with measured pressure-time curve at the bottom of mortar for lifting No.3 firework shell, the pressure rise rate-time curves were calculated, and with these results the complex flow of burned gas was discussed. Finally, with measured pressure-time curves by four pressure sensors, the muzzle velocity can be calculated, and the calculation results are near the experiment results even if a lot of burned gas flows out.
本研究では，小型鋼管を用いて，発射体を筒に入れない密閉状態と開放状態および発射体を筒に入れた状態での筒内圧力を４つの圧力センサーで測定した。圧力が音速で伝わるため，筒内底部における揚薬の燃焼ガスによる圧力の変化は瞬時に筒口まで伝わる。密閉状態では，燃焼ガスの流失がないため，筒内全域の圧力分布は均等で，勾配が生じない。開放状態では，ガス流失があるため，圧力の勾配が生じる。煙火玉のような発射体を打ち上げるとき，玉と筒との隙間から燃焼ガスが流失するため，発射体を境にその前後の圧力分布が複雑となる。また，３号煙火玉を打ち上げるときの筒内圧力を測定した。筒内底部における圧力―時間カーブから圧力上昇速度―時間カーブを求め，筒内の燃焼ガスの複雑な流れを定性的に解析した。最後に，筒から燃焼ガスの流失が多い場合でも，４つの圧力センサーで得られた圧力―時間カーブから計算した打上げ速度は実験値に近い。
firework shell, lifting charge, pressure, muzzle velocity, mortar