Particle delivery apparatuses including control junctions for use in abrasive-jet systems and related apparatuses, systems, and methods

A particle delivery apparatus, comprising:

• a cutting head;
• an abrasive delivery path extending from a hopper toward the cutting head;
• a gas flow path extending from a gas inlet toward the cutting head, the gas inlet including a vent configured to be open to the atmosphere, the gas inlet having a first state and a second, more open state;
• a first conduit coupled to the cutting head;
• a second conduit coupled to the hopper;
• and
• a T-shaped junction at an intersection of the first and second conduits,
• wherein—
• the junction is configured to collect abrasive particles in a pile that blocks a flow of abrasive particles along the abrasive delivery path when (a) a gas flow rate at a portion of the gas flow path extending through a free space around the pile is less than a flow rate sufficient to partially or entirely displace the pile and (b) a pressure differential between the hopper and a portion of the abrasive delivery path downstream from the junction is less than a pressure differential sufficient to partially or entirely displace the pile, and
• the cutting head is configured to form a jet that draws gas along the gas flow path.

A method for delivering abrasive particles within an abrasive-jet system, the method comprising:

• forming a jet with a cutting head, the jet drawing gas from a gas inlet toward the cutting head along a gas flow path extending through a control junction;
• partially or entirely displacing a pile of abrasive particles within the control junction with the gas;
• flowing abrasive particles from a hopper toward the cutting head along an abrasive delivery path extending through the control junction;
• stopping and/or slowing the jet to reduce (a) a gas flow rate through the control junction, (b) a pressure differential between the hopper and the abrasive delivery path downstream from the control junction, or (c) both;
• automatically re-forming the pile of abrasive particles within the control junction after stopping or slowing the jet;
• and
• blocking a flow of abrasive particles along the abrasive delivery path with the pile.