The influence of pulse frequency on the energy evolution law and rock-breaking effect of pulsed abrasive water jet

Compared to continuous abrasive jet and high-pressure water jet, pulsed abrasive water jet can intermittently generate high water hammer pressure and is commonly used in applications such as coal mining and petroleum engineering for rock-breaking purposes. Pulse frequency is one of the key factors affecting the evolution of abrasive acceleration and jet impact energy, thereby influencing the system's energy transfer efficiency and cutting ability. The equation of motion for abrasive acceleration is established based on the two-phase flow theory, and the variation law of abrasive velocity with pulse frequency is solved. Fluent-EDEM (Extended Discrete Element Method) was used to simulate the abrasive water jet flow field structure and abrasive acceleration process under different pulse frequency conditions, and the intrinsic influence mechanism of pulse frequency on impact energy was clarified. Combined with rock-breaking experiments using pulsed abrasive water jets, the following conclusions are drawn: as the pulse frequency increases, the inertia of the abrasive makes it unable to respond in a timely manner to the high pulsation frequency of water, resulting in a reduction in the exchange rate of intermittent energy and a gradual decrease in the maximum velocity of the abrasive. This trend is more pronounced at a higher pulse frequency. Within the same time period, the cumulative impact energy of the pulsed abrasive water jet decreases first and then increases with the increase in pulse frequency, indicating the existence of an optimal impact frequency that maximizes the cumulative impact energy of the pulsed abrasive water jet. Under fixed jet pressure conditions and the same erosion time, the pulsed abrasive water jet with a frequency of 30 Hz exhibits the best rock-breaking capability.