Pressure compensating orifice for control of nitrous oxide delivery

Abstract

This invention is a variable orifice for controlling the mass flow rate of nitrous oxide used as an engine oxidizer, this orifice having an effective size, or area, which changes with changes in the nitrous oxide pressure applied to it. Several design parameters can be changed to provide the desired effective orifice area as a function of pressure. This variable orifice can be designed to maintain an essentially constant nitrous oxide delivery rate over a wide range of nitrous oxide pressures.

1. An orifice for control of mass delivery rate of nitrous oxide,
 said nitrous oxide being used as an engine oxidizer,    said orifice having an effective area for flow of said nitrous oxide,    said effective area of said orifice being the product of the area of said orifice times the discharge coefficient of said orifice,    said orifice having a first effective area at application of a first pressure of said nitrous oxide upstream of said orifice,    said orifice having a second effective area at application of a second pressure of said nitrous oxide upstream of said orifice,    said first pressure of said nitrous oxide being operationally higher than said second pressure of said nitrous oxide,    and wherein said first effective area and said second effective area are operationally different.    
     
     
       2. The orifice of  claim 1 , wherein said first effective area is less than said second effective area. 
     
     
       3. The orifice of  claim 1 , wherein said orifice delivers a first mass delivery rate of said nitrous oxide at said first pressure of said nitrous oxide and said orifice delivers a second mass delivery rate of said nitrous oxide at said second pressure of said nitrous oxide, and wherein said first mass delivery rate and said second mass delivery rate are essentially equal. 
     
     
       4. The orifice of  claim 1 , wherein said orifice is contained in a nozzle for delivery of said nitrous oxide. 
     
     
       5. The orifice of  claim 1 , wherein said effective area of said orifice contains a variable area of a variable orifice and a fixed area of a fixed orifice. 
     
     
       6. The orifice of  claim 1 , wherein said effective area of said orifice contains a variable area determined by a moveable member in a bore. 
     
     
       7. The orifice of  claim 6 , wherein said moveable member has its movement affected by the force of a spring. 
     
     
       8. The orifice of  claim 6 , wherein said moveable member has its movement affected by the pressure of said nitrous oxide. 
     
     
       9. The orifice of  claim 6 , wherein said bore has a taper which in operation affects said effective area of said orifice. 
     
     
       10. The orifice of  claim 9 , wherein said taper has a first included angle at a first effective position of said moveable member and a second included angle at a second effective position of said moveable member. 
     
     
       11. The orifice of  claim 6 , wherein said moveable member has a taper which in operation affects said effective area of said orifice. 
     
     
       12. The orifice of  claim 6 , wherein said bore has a taper which in operation affects said effective area of said orifice and said moveable member has a taper which in operation affects said effective area of said orifice. 
     
     
       13. The orifice of  claim 1 , wherein said nitrous oxide is principally a liquid in equilibrium with its vapor when upstream of said orifice,
 said orifice having a first pressure difference which is said first pressure of said nitrous oxide upstream of said orifice less a corresponding first downstream pressure,    said orifice having a second pressure different which is said second pressure of said nitrous oxide upstream of said orifice less a corresponding second downstream pressure,    said orifice having a first mass delivery rate essentially determined by the product of a proportionality constant times said first effective area of said orifice times the square root of the product of said first pressure different times the square root of the pressure of nitrous oxide upstream of said orifice,    and said orifice having a second mass delivery rate essentially determined by the product of said proportionality constant times said second effective area of said orifice times the square root of the product of said second pressure difference times the density of said nitrous oxide at said second pressure of said nitrous oxide upstream of said orifice.    
     
     
       14. The orifice of  claim 13 , wherein said first mass delivery rate and said second mass delivery rate are essentially equal. 
     
     
       15. An orifice for control of mass delivery rate of nitrous oxide,
 said nitrous oxide being used as an engine oxidizer,    said orifice having an effective area for flow of said nitrous oxide,    said effective area of said orifice being the product of the area of said orifice times the discharge coefficient of said orifice,    said orifice having a first effective area at application of a first pressure of said nitrous oxide upstream of said orifice,    said orifice having a second effective area at application of a second pressure upstream of said orifice,    and wherein said orifice delivers a first mass delivery rate of said nitrous oxide at said first pressure of said nitrous oxide and said orifice delivers a second mass delivery rate of said nitrous oxide at said second pressure of said nitrous oxide, and wherein the ratio of said first mass delivery of said nitrous oxide rate to said second mass delivery rate of said nitrous oxide is less than the ratio of said first mass delivery rate of said nitrous oxide to a third mass delivery rate of said nitrous oxide, said third mass delivery rate being at said second pressure of said nitrous oxide and said first effective area of said orifice.    
     
     
       16. An apparatus to control mass flow rate of nitrous oxide, the apparatus comprising:
   a body with an inlet for admission of pressurized nitrous oxide and an outlet for delivery of the nitrous oxide to an engine for use as an oxidizer, the pressurized nitrous oxide at the inlet having a first pressure and a second higher pressure;        a moveable member located within the body;        a pressure force on the moveable member resulting from the pressurized nitrous oxide, the pressure force being a first pressure force when the nitrous oxide pressure has the first pressure and a second pressure force when the nitrous oxide has the second pressure;        a spring which applies a spring force to the moveable member which opposes the pressure force;        a first position of the moveable member with respect to the body which is the position at which the spring applies a first spring force to the moveable member which essentially equally opposes the first pressure force on the moveable member;        a second position of the moveable member with respect to the body which is the position at which the spring applies a second spring force to the moveable member which essentially equally opposes the second pressure force on the moveable member;        whereby an orifice is established by the body and the moveable member, the orifice having a first area for flow of nitrous oxide when the moveable member is in the first position and a second area for flow of nitrous oxide when the moveable member is in the second position.     
     
     
       17. The apparatus of  claim 16  wherein the first area for flow of nitrous oxide is larger than the second area for flow of nitrous oxide. 
     
     
       18. The apparatus of  claim 16  wherein the moveable member moves in a tapered passage in the body. 
     
     
       19. The apparatus of  claim 18  wherein the orifice is established by the tapered passage and the moveable member. 
     
     
       20. The apparatus of  claim 16  wherein the mass flow rate of nitrous oxide has a first mass flow rate when the nitrous oxide has the first pressure and the moveable member is in the first position and a second mass flow rate when the nitrous oxide has the second pressure and the moveable member is in the second position, and the first mass flow rate is greater than the mass flow rate which would exist with the first pressure of nitrous oxide if the moveable member was in the second position and the second mass flow rate is smaller than the mass flow rate which would exist with the second pressure of nitrous oxide if the moveable member was in the first position.