Morphogenetic modelling of in-flight icing

• US 20040155151A1
• Filed: 06/05/2003
• Published: 08/12/2004
• Est. Priority Date: 06/05/2002
• Status: Active Grant

• Current Assignee: National Research Council Canada
• Original Assignee: National Research Council Canada
• Inventors: Szilder, Krzysztof
• Granted Patent: US 6,868,721 B2
• Time in Patent Office: Days
• US Class Current: 244/134F
• CPC Class Codes: B64D 15/20 Means for detecting icing or initiating de-icing

Abstract

The accretion of ice on an aerodynamic surface is predicted by identifying predetermined atmospheric parameters relevant to ice formation in a particular fluid environment. Then the behaviour of individual fluid elements is simulated based on the identified parameters to create a model of the ice accretion.

Claims

1. A method of modelling in-flight icing on a surface in a fluid stream, comprising the steps of:

identifying predetermined macroscopic physical variables relevant to ice formation in a particular fluid environment;

calculating the behaviour of individual fluid elements based on said identified macroscopic physical variables taking into account the effect on collision efficiency of non-linear droplet trajectories and the distribution of heat transfer over the airfoil; and

predicting ice accretion based on the calculated behaviour of said individual fluid elements.

2. A method as claimed in claim 1, wherein said behaviour includes the freezing and shedding of said individual fluid elements.

3. A method as claimed in claim 2, wherein the behaviour of said individual fluid elements is assumed to be stochastic.

4. A method as claimed in claim 2, wherein said variables are selected from the group consisting of:

fluid stream velocity, fluid stream liquid water content, droplet volume median diameter, altitude and fluid temperature.

5. A method as claimed in claim 1, wherein an azimuthal distribution of the heat transfer to the airstream is taken into account in the calculation of the behaviour of said individual fluid elements.

6. A method as claimed in claim 2, wherein step of calculating the behaviour of said individual fluid elements involves calculating the freezing probability thereof in said particular fluid environment.

7. A method as claimed in claim 6, wherein the accretion domain for said ice is defined by a lattice and the freezing probability at a location n is calculated by determining the difference between a total upstream impinging mass of water

8. A method as claimed in claim 6, wherein said freezing probability is given by the expression

9. A method as claimed in claim 2, wherein the behaviour of said individual fluid elements is calculated successively for the total number of fluid elements in an intercepted mass flux.

10. A method as claimed in claim 9, wherein the distribution of freezing probability is recalculated after calculating the behaviour of each said fluid element.

11. A method as claimed in claim 6, wherein said freezing probability varies in a time-dependent manner.

12. A method as claimed in claim 7, wherein said lattice is a two-dimensional lattice.

13. A method as claimed in claim 7, wherein said lattice is a three-dimensional lattice.

14. A method as claimed in claim 1, wherein said surface is an airfoil.

21. A system as claimed in claim 6, wherein the accretion domain for said ice is defined by a lattice and the freezing probability at a location n is calculated by determining the difference between a total upstream impinging mass of water

26. A system as claimed in claim 21, wherein said lattice is a two-dimensional lattice.

27. A system as claimed in claim 21, wherein said lattice is a three-dimensional lattice.

15. A system for predicting in-flight icing on a surface in a fluid stream, comprising:

sensors for measuring predetermined macroscopic physical variables relevant to ice formation in a particular fluid environment;

a processor for calculating the behaviour of individual fluid elements based on said identified macroscopic physical variables taking into account the effect on collision efficiency of non-linear droplet trajectories and the distribution of heat transfer over the airfoil and predicting ice accretion based on the calculated behaviour of said individual fluid elements.

16. A system as claimed in claim 15, wherein said behaviour includes the freezing and shedding of said individual fluid elements.

17. A system as claimed in claim 16, wherein the behaviour of said individual fluid elements is assumed to be stochastic.

18. A system as claimed in claim 17, wherein said variables are selected from the group consisting of:

fluid stream velocity, fluid stream liquid water content, droplet volume median diameter, altitude and fluid temperature.

19. A system as claimed in claim 15, wherein an azimuthal distribution of the heat transfer to the airstream is taken into account in the calculation of the behaviour of said individual fluid elements.

20. A system as claimed in claim 16, wherein the behaviour of said individual fluid elements is determined by calculating the freezing probability thereof in said particular fluid environment.

22. A system as claimed in claim 20, wherein said freezing probability is given by the expression

23. A system as claimed in claim 16, wherein said processor is programmed to calculate the behaviour of said individual fluid elements successively for the total number of fluid elements in an intercepted mass flux.

24. A system as claimed in claim 23, wherein said processor is programmed to recalculated the distribution of freezing probability after calculating the behaviour of each said fluid element.

25. A system as claimed in claim 23, wherein said processor takes into account the time-dependent variation in freezing probability.

28. A system as claimed in claim 15, wherein said surface is an airfoil.