Silencer for a blast nozzle

A noise suppressed blasting system comprising:

• a source of blasting gas in a predetermined pressure range with abrasive particles entrained therein;
• a blast nozzle comprises a nozzle inlet for connection, in use, to the source of blasting gas, a nozzle outlet for emission of the blasting gas, and a nozzle conduit) from the nozzle inlet to the nozzle outlet including a throat therebetween, wherein the blast nozzle has a nozzle outlet area (A) and a nozzle throat area (A*), wherein a ratio (A/A*) of the nozzle outlet area (A) to the throat area (A*) is selected so that in use blasting gas is emitted from the blast nozzle as a supersonic jet;
• a silencer connected, in use, to the blast nozzle to suppress operational noise of the blast nozzle, wherein the silencer comprises a silencer body with a silencer conduit therethrough, the silencer body having a length and diameter configured to cause a flow condition of a jet received from the nozzle outlet to be modified such that 1½ shock cells are created in a jet inside the silencer, and wherein no shock cells are created in a jet outside the silencer, and wherein a jet, in use, exits the silencer in the form of a core jet with an established turbulent shear layer thereabout and entraining an annular jet located around the core jet;
• wherein the silencer body includes a coupling portion arranged to connect to a portion of the blast nozzle adjacent the nozzle outlet and a sound suppression portion defining the silencer conduit, wherein the sound suppression portion extends from the coupling portion to a silencer outlet of the silencer;
• wherein the predetermined pressure range is 80 psi (551.58 kPa) to 120 psi (827.37 kPa) and the nozzle has an area ratio A/A* of 1.63±5%;
• wherein the nozzle comprises a #7 nozzle;
• and
• and wherein the length of the silencer is between 17.5 mm and 157.5 mm and the diameter (Ds) of the silencer is between 23 mm and 31.5 mm.