Method and apparatus for enhanced blast stream
A method and apparatus produce an enhanced blast stream which may be directed at a workpiece. The enhanced blast stream has higher energy allowing the blast stream to remove difficult to remove coatings from substrates. A heated flow is combined with an entrained particle flow and expelled through a nozzle. The heated flow results in more energy being imparted to the coating.
1. A particle blast system configured to expel a stream of entrained particles from a blast nozzle while the particle blast system is operating within its operating parameters, the particle blast system comprising:
a. a source of heated fluid;
b. a source of transport fluid;
c. a particle feeder connected to the source of transport fluid, the particle feeder configured to entrain particles into a flow of the transport fluid flowing from the source of transport fluid thereby creating an entrained particle flow;
d. an injector comprising:
i. a first flow passageway comprising a first flow passageway inlet and a first flow passageway outlet wherein the first flow passageway comprises
(a) a first portion in fluid communication with the first flow passageway inlet; and
(b) a second portion in fluid communication with the first flow passageway outlet, the second portion comprising a length extending from the first portion to the first flow passageway outlet, the second portion comprising a generally constant to converging cross-sectional area along its length; and
ii. a second flow passageway comprising a second flow passageway inlet and a second flow passageway outlet,
the second portion comprising a junction area, located upstream of the first flow passageway outlet, at which the second flow passageway is in fluid communication with the first flow passageway via the second flow passageway outlet;
e. an entrained flow passageway in fluid communication with the second flow passageway inlet and configured to deliver the entrained particle flow from the particle feeder to the second flow passageway; and
f. a heated fluid passageway which places the source of heated fluid in fluid communication with the first flow passageway inlet.
2. The particle blast system of claim 1 , wherein the first portion comprises a converging portion.
3. The particle blast system of claim 1 , wherein the first flow passageway is configured to produce sonic flow in the first flow passageway downstream of the junction area when the particle blast system is operating within its operating parameters.
4. The particle blast system of claim 3 , wherein the blast nozzle is in fluid communication with the first flow passageway outlet, the blast nozzle being configured for supersonic expansion of flow therein.
5. The particle blast system of claim 1 , wherein the second flow passageway comprises a third portion, the third portion comprising converging portion.
6. The particle blast system of claim 5 , wherein the second flow passageway comprises a fourth portion downstream of the third portion, the fourth portion comprising a portion of constant cross-sectional area leading to a portion of converging cross-sectional area.
7. The particle blast system of claim 1 , wherein the particles comprise cryogenic particles.
8. The particle blast system of claim 1 , wherein the first flow passageway is straight between the first flow passageway inlet to the first flow passageway outlet.
9. The particle blast system of claim 1 , wherein when the particle blast system is operating within its operating parameters, the static wall pressure of the heated fluid flowing through the first flow passageway at the junction area is lower than the total pressure of the entrained particle flow flowing through the second flow passageway.