Percussion characteristic analysis for hydraulic rock drill with no constant-pressurized chamber through numerical simulation and experiment

Abstract

Considering the insufficiency of numerical study on the percussion characteristic of hydraulic rock drill, which restricts the improvement of efficiency and reliability, a coupling model including the impact piston, spool valve, impact accumulator, and connecting pipelines was established taking into account the oil compressibility, oil leakage, and pressure drop in valve ports. The rebound velocity of impact piston was calculated based on the stress wave theory. The simulation results revealed the coupling mechanism of percussion system. Pressure curves of the piston's front-chamber and rearchamber, and valve's left-chamber and right-chamber were obtained by field rock drilling test. Then, the velocity curve of impact piston was obtained after judging the striking point through the feature of rear-chamber's pressure spike, so were the rock drill's impact energy, impact frequency, and impact power. The simulation and experimental results have consistency. And, on this basis, the influence of spool valve's damping clearance (d) and pipeline diameters (d 1 , d 2) connecting the impact piston and spool valve on the percussion performance and system cavitation was researched. The results show that the larger d is better considering reversal time of spool valve, the impact frequency of rock drill, pressure fluctuation, and cavitation relief. But too large d will cause over quick impact velocity of the spool valve, which may lead to strong vibration and the damage of spool valve. The optimal value of d is 0.01 mm by comprehensive consideration. The pipeline diameters have an important influence on the pressure fluctuation and negative pressure in rear-chamber. The diameters should be larger than 18 mm to alleviate the cavitation. This article provides means for the design and research of rock drills.

Impact performance optimization for hydraulic rock drill based on stroke and flow compensation factors

“…When the displacement at the interface of the piston and shank collision caused by the reflected wave is greater than 0, the piston rebounds. The rebound criterion is shown in equations ( 12) and ( 13), and the formula for rebound velocity is shown in equation (14).…”

“…This study validates the anti-jamming characteristics of the bi-directional pneumatic submerged hammer and finds that the total weight of the submerged hammer does not exert a significant impact on drilling performance. Ma et al 14 incorporate factors like oil compressibility, impact leakage, and pressure loss to develop a coupled dynamics model for the impact system. They investigate the impact of spool valve damping clearance and pipeline diameter on impact performance.…”

Influence of Piston Mass and Working Pressure on the Impact Performance of a Hydraulic Rock Drill Using the Stress Wave Method

“…A hydraulic rock drill is usually composed of an impact system, a shank adapter rebound absorption system, a rotary system, and a head. When the rock drill is installed on the trolley in preparation for rock drilling, it also needs to be equipped with an auxiliary water supply, dust prevention, propulsion systems, and so on [2]. The operational process of the hydraulic rock drill comprises four functions: propulsion, impact, rotation, and flushing (see Figure 1).…”

“…The hydraulic rock drill is the external working mechanism of a rock drill jumbo and is the most important component for rock drilling [1]. It is widely used in mining, tunnel excavation, urban construction, and other engineering operations [2]. A hydraulic rock drill uses oil as its working medium, converting the pressure energy of the oil into the impact energy of the piston, and then transmits this energy through the drill rod into the rock in the form of a stress wave [3].…”