Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/50—Carbon dioxide
  • C01B32/55—Solidifying

Definitions

• the present invention relates generally to injection nozzles, and is particularly directed to injection nozzles which cause the phase change of carbon dioxide from the liquid state to the solid state by flowing pressurized liquid CO- through an orifice.
• the invention will be specifically disclosed in connection with an injection nozzle which precools a flow of liquid CO, prior to the flow passing through a plurality of orifices by directing a portion of the flow through a pilot orifice.
• Injection nozzles have long been used to convert a continuous flow of a liquid under pressure into a continuous, flow of solid particles.
• CO carbon dioxide
• CO is the medium which is transformed from liquid into solid particles through the use of such injection nozzles. This is particularly true when there is a need for a continuous flow of solid CO, particles, such as is needed by particle blast apparatuses which utilize C0 2 .
• U.S. Patent No. 4,744,181 discloses an apparatus used for cryogenic cleaning in which a continuous flow of C0 2 pellets are directed against an object to be cleaned.
• Such an apparatus requires a continuous supply of CO, pellets in order to allow the operator to use the apparatus for continuous cleaning.
• the C0 2 particles may actually be crushed dry ice (solid C0 2 > created by the apparatus by crushing large blocks of dry ice, the cleaning effect of the apparatus is more efficient if a uniform supply of solid C0 2 particles having a size and density within a controlled range is used. Crushing of dry ice results in unpredictable particle sizes and densities, thereby decreasing the efficiency of a cryogenic cleaning apparatus.
• One method for supplying a flow of solid CO, particles within the parameters necessary for the cryogenic cleaning apparatus is to convert liquid C0 2 to the solid state and then to feed the particles directly into the apparatus. For maximum efficiency and economics, this requires that the actual phase change occur in close physical proximity to the cleaning apparatus.
• a supply of pressurized liquid CO is caused to flow through an injection nozzle where it is converted to solid CO, particles or CO, snow.
• the solid CO is then forced through a die and formed into pellets by a breaker plate associated with the die. The pellets can then be transferred into the cryogenic particle blast cleaning apparatus in a continuous fashion.
• Prior art injection nozzles have typically comprised a nozzle body having a single large orifice through which the entire flow of C0 2 passes.
• the pressure of the C0 2 drops as it flows through the orifice, causing the liquid C0 2 to flash to the solid state.
• the temperature of the C0 2 drops to approximately -90° to -100 ⁇ F.
• Such a single orifice nozzle is known to have a low efficiency and results in a large amount of C0 2 remaining in the liquid state after passing through the orifice.
• this excess liquid can result in converting some of the solid CO, back to liquid or to gas.
• liquid quickly boils off into gas. Any CO, in the liquid or solid state after passing through the injection nozzle is wasted.
• the Brody Horn has three small orifices formed in the nozzle body. These orifices are angled outward from the center of the nozzle, at an angle to the direction of the flow, which helps to disperse the CO, solid particles downstream of the nozzle.
• the Brody Horn has a higher efficiency than a single large orificed nozzle. Still, the efficiency of the Brody Horn only ranges as high as 40%, which is an industry standard.
• a problem with prior art nozzles is a condition known as "snowing the nozzle" which occurs when the orifice or orifices become blocked by solid CO,. This can occur in the orifices during operation or, especially, when the flow of pressurized C0 2 liquid is shut off. As the pressure drops after shut off, the liquid C0 2 can flash to the solid state upstream of the nozzle, thereby blocking the nozzle and preventing immediate subsequent use.
• Yet another object of the present invention is to provide an injection nozzle which precools the liquid prior to it flowing through the primary orifices.
• a still further object of the present invention is to provide an injection nozzle which, itself, is cooled by the phase change and resultant flow of solid particles of a pilot flow of liquid.
• an improved injection nozzle for transforming a continuous flow of liquid from the liquid state to the solid state.
• the nozzle includes a body with an inlet surface and an outlet surface, at least one primary orifice formed through the body, and precooling means connected to the body for cooling the liquid prior to when the liquid flows through the primary orifices.
• the precooling means is a pilot nozzle connected to the body and extending upstream therefrom.
• the pilot nozzle has a pilot orifice formed in it which communicates with a central cavity formed through the pilot nozzle and the body, creating a continuous flow path between the upstream cavity and the downstream cavity through the pilot orifice and the central cavity.
• an exit nozzle is connected to the body and extends downstream therefrom, and terminates in an exit surface.
• the central cavity is formed continuously through the exit nozzle, remaining in communication with the downstream cavity at the exit surface.
• the central cavity is tapered and has a cross sectional area which increases in the downstream direction.
• means are provided for causing the liquid to mix while flowing past the pilot nozzle which increase the transfer of heat from the liquid to the pilot nozzle, cooling the liquid.
• a spring is disposed about the pilot nozzle and connected to the body.
• the primary orifices have aspect ratios of at least 4.0.
• the pilot orifice has an aspect ratio of at least 4.0.
• the exit nozzle has an exterior surface which at least a portion of which is an inclined surface of increasing circumference in the downstream direction.
• the nozzle is disposed in a housing which extends downstream of the body, and forms an exit cavity between the housing, the outlet surface of the body, and the exterior surface of the nozzle.
• the final portion of the exit cavity has a decreasing cross sectional area in the downstream direction.
• a nozzle body has at least one primary orifice and an exit nozzle connected to the body and extending downstream thereof. At least a portion of the exterior surface of the exit nozzle is an inclined surface of increasing circumference in the downstream direction.
• Figure 1 is a simplified side elevational view of. an apparatus for forming CO, pellets from snow created by a phase change nozzle.
• Figure 2 is an end view of a single orifice prior art nozzle mounted in a housing.
• Figure 3 is a cross sectional view along line 3-3 of figure 2 showing the single orifice prior art nozzle.
• Figure 4 is a fragmentary cross sectional side view of the nozzle of figures 2 and 3, shown in an installed position.
• Figure 5 is an end view of a Brody Horn.
• Figure 6 is a cross sectional view taken along line 6-6 of figure 5 showing the Brody Horn.
• Figure 7 is a cross sectional view of a preferred embodiment of the present invention showing the - 8 -
• nozzle disposed in a housing.
• Figure 8 is a cross sectional view of the body of the nozzle, pilot nozzle, and exit nozzle taken along A-A of figure 9.
• Figure 9 is a cross sectional view of the body of the nozzle taken along 9-9 of figure 8.
• Figure 10 is a cross sectional view of the housing of figure 7.
• Figure 11 is a fragmentary cross sectional view of the nozzle of figure 7 shown in an in use location.
• Figure 12 is a cross sectional view of the nozzle of figure 7, including a turbulator.
• figure 1 shows an apparatus 1 for forming CO, snow into pellets for use with a cryogenic cleaning apparatus (not shown) .
• Apparatus 1 may, however, be incorporated as an integral part of such a cryogenic cleaning apparatus.
• Pressurized liquid C0 2 flows through hose or pipe 2 from a source of liquid C0 2 (not shown) to phase change nozzle 3.
• As the CO, liquid under pressure flows through the orifice of nozzle 3 from the upstream cavity 4 to the lower pressure downstream cavity 5, it flashes to the solid state due to its physical properties, a process which is well known in the art.
• the solid C0 2 particles which may be formed of fine particles referred to as snow, flows from downstream cavity 5 into cylinder 6 where is accumulates due to the continuous flow of C0 2 .
• piston assembly 7 moves to the right and compresses the C0 2 snow. forcing it into die breaker plate assembly 8. As piston assembly 7 forces the snow through die breaker plate assembly 8, pellets of C0 2 are formed and forced into chamber 9, and flowing therefrom to the cryogenic cleaning apparatus (not shown) .
• typical prior art nozzles use a body 10 having a single orifice 11 formed therethrough.
• the body is disposed in a housing 12 which is then installed in a high pressure CO, liquid line, such as in an apparatus la as shown in figure 4.
• the supply of C0 2 is through hose 2 which is shown in figure 4 as being attached by the use of an intermediate fitting 13 which is threaded into engagement with housing 12 and hose 2.
• liquid CO flows from hose 2 into upstream cavity 4, flows through orifice li where it flashes to the solid state and flows into downstream cavity 5, flowing therefrom into cylinder 6.
• Figures 5 and 6 show a Brody Horn, having a body 10a with three orifices 14 which are angled relative to the direction of flow indicated by lines 15. The angle of orifices 14 assists in dispersing the CO, snow downstream of the body 10.
• Figure 7 shows a preferred embodiment of the present invention.
• Nozzle 16 is comprised of two parts, housing 17 and nozzle 18.
• Nozzle 18 is formed as body 19, pilot nozzle 20 and exit nozzle 21.
• Body 19 has an inlet surface 22 which is on the upstream side of body 19 and immediately adjacent the upstream cavity 24 (figure 11).
• Body 19 also has outlet- surface 23 located on the downstream side of body 19.
• a step 26 is formed in the outside surface 27 of body 19 for installation and assembly purposes.
• Housing 17, as shown in figures 7 and 10 has a complimentary step 28 to allow nozzle 18 to be securely disposed within and carried by housing 17.
• Three primary orifices 29 are formed through body 19 which communicate with inlet surface 22 and outlet surface 23, respectively.
• Pilot nozzle 20 is connected to body 19 and extends upstream therefrom. Pilot nozzle 20 is generally cylindrical in shape and extends from the approximate center of body 19, approximately equal distance from each of the primary orifices 29. Tip 30 of pilot nozzle 20 is tapered, having an increasing circumference in the direction of flow of the liquid C0 2 , so as to the creation of turbulence in the flow of C0 2 .
• Exit nozzle 21 extends in a downstream direction from body 19 adjacent outlet surface 23.
• Exit surface 31 is formed at the end of pilot nozzle 21, and is substantially perpendicular to the direction of flow of the C0 2 . It should be noted that exit surface 31 is also substantially perpendicular to the longitudinal axis of primary orifices 29.
• Exit nozzle 21 has an exterior surface 32 which is continuous with outlet surface 23 and terminates at exit surface 31. A portion 33 of exterior surface 32 is inclined having an increasing circumference in the downstream direction indicated by line 34. The inclined wall portion 33 terminates at exit surface 31.
• pilot orifice 35 is formed in pilot nozzle 20, which communicates with upstream cavity 24.
• central cavity 36 Formed in pilot nozzle 20, body 19, and exit nozzle 21 is central cavity 36, which communicates at one end 37 with pilot orifice 35, and, at the other end 38, downstream cavity 25.
• Central cavity 36 has a circular cross section, with wall 39 tapered in the l downstream direction 34. Thus, the cross sectional area, and circumference of central cavity 36 is larger at end 38 than at end 37.
• housing 17 has a lower portion 41 which extends downstream of outlet surface 23.
• the inner surface 42 has a
• exit cavity 43 is formed annularly by inner surface 42 of housing 17, outlet surface 23 of body 19, exterior surface 32 of exit nozzle 21.
• Exit cavity 43 has a decreasing cross sectional area adjacent the inclined wall portion 33 in the downstream direction 34.
• Primary orifices 29 communicate with downstream cavity 25 through exit cavity 43.
• Figures 11 and 12 also show a helical spring 44 connected to body 19 and disposed around pilot nozzle 20.
• FIG 11 shows nozzle 16 in an in use ppsition.
• Housing 17 has internal threads 45 which mesh with
• Fitting 47 is connected to hose pipe 48 which supplies a continuous flow of liquid CO,.
• Lower portion 41 of housing 17 has external threads 49 which intermesh with internal threads 50 of mating
• liquid C0 2 flows from the source, through upstream cavity 24 and into nozzle 18, where the phase change occurs.
• pilot orifice 35 The portion of the flow which goes through pilot orifice 35 is flashed from the liquid state to the solid state prior to exiting orifice 35.
• the temperature of the pilot flow of the CO drops to about -90° to -100° F when it flashes and thereafter exits pilot orifice 35 as solid particles and continues to flow through central cavity 36.
• the temperature drop of the C0 2 which occurs in pilot orifice 35, as well as the low temperature of the solid particles flowing through central cavity 36 causes pilot nozzle 20 to be cooled substantially below the temperature of the liquid C0 2 flowing along the outside of pilot nozzle 20.
• the continuous flow of C0 2 through the pilot orifice 35 and central cavity 36 acts as a constant temperature heat sink, because the solid particles flowing through central cavity 36 absorb heat so they sublimate to the gas state at a constant temperature due to the lower pressure of the downstream side of pilot orifice 35.
• This continuous flow/constant temperature sublimation acts as a heat sink to lower the temperature of pilot nozzle 20, as well as all other portions of nozzle 18, including body 19 and exit nozzle 21, which are in contact with the central cavity 36.
• Pilot nozzle 20 cooled by the pilot flow flowing therethrough, has a lower temperature than the temperature of the liquid C0 2 flowing past the outside of pilot nozzle 20.
• the lower temperature of pilot nozzle 20 results in heat being transferred from the higher temperature liquid C0 2 flowing along pilot nozzle 20. This causes a drop in the temperature of the liquid CO, in the area of the upstream cavity 24 which is downstream of the tip 30 of pilot nozzle 20.
• the liquid C0 2 which does not flow through pilot orifice 35 is precooled prior to entering primary orifices 29 located to body 19.
• spring 44 is located about the outside of pilot nozzle 20 to cause the liquid
• a device such as the spring is commonly called a turbulator, and results in more an even temperature distribution throughout the liquid CO, in this region.
• heat is transferred by conduction and by the mixing of the liquid C0 2 prior to flowing through the primary orifices 29.
• the cooled liquid C0 2 passes through primary orifices 29, a large portion of which flashes to the solid state due to the pressure drop encountered in primary orifices 29.
• the flow exits primary orifices 29 as a mixture of all three states of C0 2 ⁇
• the precooling of the liquid C0 2 prior to entering primary orifices 29 and the associated pressure drop, results in a higher percentage of C0 2 in the solid state being present in the flow as it exits primary orifices 29.
• pilot orifice 35 also reduces the temperature of body 19, and primary orifices.
• the efficiency of primary orifices 29 in producing solid C0 2 from liquid CO, is increased due to the lower temperature of primary orifices 29, which absorbs heat from the C0 2 as it flows through.
• the liquid C0 2 as it flows through an orifice, whether it is the pilot orifice 35 or primary orifices 29, changes to the solid state at approximately one half the length of the orifice.
• the location of the change of state in the orifice is a function of the pressure drop through the orifice. If the pressure drop is too great, the phase change will snow the nozzle or orifice, causing it to become clogged and operate inefficiently.
• the pressure drop in a particular orifice is a function of the inlet pressure, the outlet pressure, the orifice diameter, and the orifice length.
• the ratio of the length of an orifice to the diameter of the orifice is called the aspect ratio.
• the present embodiment of this invention utilizes an aspect ratio of approximately 7.7, based on the parameters described above.
• the minimum aspect ratio to prevent clogging the orifice based on the above parameters has been found imperatively to be 4.0.
• the upstream pressure does not drop rapidly enough to snow the upstream side. Enough back pressure must be created on the upstream side so that the liquid remaining in the upstream cavity, and supply hoses thereto, will boil off as gas and pass through the nozzle.
• a primary orifice diameter of .052 inches and length of .400 inches is shown.
• the pilot orifice has a diameter of .040 inches and a length of .250 inches.
• the walls 39 of central cavity 26 are tapered to prevent the pilot flow of solid particles from blocking the central cavity 36, thereby diminishing or eliminating the pilot flow. Through this construction, "snowing" of the pilot orifice 35 and central cavity 36 is prevented.
• the preferred embodiment described herein has a central cavity diameter of .450 inches at end 37, and a taper of

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Inorganic Chemistry (AREA)
• Nozzles (AREA)
• Disintegrating Or Milling (AREA)

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• 1990
  • 1990-02-07 JP JP2504023A patent/JPH03504825A/ja active Pending
  • 1990-02-07 WO PCT/US1990/000691 patent/WO1990009347A2/en not_active Application Discontinuation
  • 1990-02-07 EP EP90904054A patent/EP0423259A1/de not_active Withdrawn

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