Research on the Synchronization and Shock Characteristics of an Air Adjustment Mechanism for Cluster-Type DTH Hammers under Partial Loads

Abstract

Cluster down-the-hole (DTH) hammers are often used in large-diameter hard rock drilling operations. Due to complex rock formation conditions, cluster DTH hammers cannot adjust the working airflow in time according to rock formation conditions, resulting in frequent damage to cluster DTH hammers and low work efficiency. Aiming at this problem, this paper proposes an airflow adjustment mechanism as a solution. In this paper, the operation stability and airflow adjustment characteristics of the adjustment mechanism are studied. The impact characteristics and driving force variation characteristics of the adjustment mechanism under different speeds and loading modes are analyzed, and the results show that the movement impact of the adjustment mechanism increases with the increase of the movement speed of the driving actuator under the same loading mode. With the increase of the eccentric load, the critical movement speed of the driving actuator decreases when the adjustment mechanism moves without impact. The test verifies the synchronization characteristics of the adjustment mechanism under different load modes and different control valves. The results show that, under the condition of uniform load, the synchronization accuracy of the dividing/focusing valve and the proportional valve is good. With the increase of the eccentric load difference, the synchronization performance of the dividing/focusing valve becomes worse, and the average error increases. The test results in this paper are of great significance for guiding the engineering design of cluster DTH hammers.