ABSTRACT

In this study, the performance of a single-stage gas gun with a natural gas-air mixture as the propellant gas is investigated by measuring the explosion pressure and the projectile velocity. In this work, the combined effect of elevated initial pressure, mixing, equivalence ratio, and ignition energy on the explosion pressure and projectile velocity is studied. To assess the performance of the natural gas-air combustion, a series of tests with helium and air as the propellant gas are carried out to measure the projectile velocity. The fuel used in this study consisted of 84.2% methane, 9.5% ethane, and 3.7% propane. The helium gas was 99.999% pure. The volume fraction of fuel in the natural gas-air mixture varied between 4.98% and 17.3%, and the flammability limits of the natural gas were between 4.41% and 14.47%. The equivalence ratio Φ was used to control the fuel concentration in the mixture. The equivalence ratio in this study was 0.5, 0.75, 1, 1.5, and 2. The experimental results indicated that despite the low percentage of methane and high percentage of higher hydrocarbons in natural gas, the maximum pressure still occurs at the equivalence ratio 1, the finding which had already been proved to be the case for pure methane. However, the maximum combustion pressure is reduced compared to other fuels with higher methane and lower hydrocarbon content. Also, the study showed that the maximum combustion pressure increased with rising the ignition energy also when the mixer was used to blend the natural gas-air mixture. The experimental results showed that at low pressures, the projectile velocity was higher using helium compared to the same pressures produced by the combustion of methane-air mixture. However, at higher pressures, the projectile velocity was much higher for the pressures produced by combustion due to its lower molecular weight and the heat produced in the combustion process. The price analysis also indicated that for the same output pressure, the cost of a test with a methane-air explosion is 78 times lower than that of a test with helium.

摘要

在这项研究中，通过测量爆炸压力和弹丸速度来研究以天然气-空气混合物作为推进剂气体的单级气枪的性能。在这项工作中，研究了升高的初始压力、混合、当量比和点火能量对爆炸压力和弹丸速度的综合影响。为了评估天然气-空气燃烧的性能，采用氦气和空气作为推进剂气体进行了一系列测试，以测量弹丸速度。本研究中使用的燃料由 84.2% 的甲烷、9.5% 的乙烷和 3.7% 的丙烷组成。氦气纯度为 99.999%。天然气-空气混合物中燃料的体积分数在 4.98% 和 17.3% 之间变化，天然气的可燃性极限在 4.41% 和 14.47% 之间。当量比 Φ 用于控制混合物中的燃料浓度。本研究的当量比分别为0.5、0.75、1、1.5和2。实验结果表明，尽管天然气中甲烷含量较低，高级烃含量较高，但当当量比为1时，最大压力仍然出现，这一发现已经被证明是纯甲烷的情况。然而，与具有较高甲烷和较低碳氢化合物含量的其他燃料相比，最大燃烧压力降低了。此外，研究表明，当使用混合器混合天然气-空气混合物时，最大燃烧压力也会随着点火能量的增加而增加。实验结果表明，在低压下，与甲烷-空气混合物燃烧产生的相同压力相比，使用氦的弹丸速度更高。然而，在较高压力下，由于其较低的分子量和燃烧过程中产生的热量，燃烧产生的压力的弹丸速度要高得多。价格分析还表明，在相同的输出压力下，甲烷-空气爆炸试验的成本比氦气试验的成本低 78 倍。