Icing partition judgment method based on water drop coverage rate

Abstract

The invention discloses an icing partition judgment method based on a water drop coverage rate, and belongs to the technical field of icing simulation of visual measurement. The problem that in the prior art, due to the fact that a traditional icing model cannot distinguish an icing continuous area and a non-continuous area, icing numerical simulation precision is low is solved. The method comprises the steps of defining a water drop coverage rate calculation formula; according to the size relation between the water drop coverage rate and a certain typical characteristic constant value, obtaining a relational expression for judging the subareas of the icing surface; enabling the water drop coverage rate to be equal to a certain typical characteristic constant value, and obtaining a water drop collection coefficient critical value corresponding to the certain typical characteristic constant value; water drop collection coefficient distribution characteristics of a water drop impact area are obtained through test measurement or simulation calculation, and the position of a water drop collection coefficient critical value is determined, namely, the partition boundary between an icing continuous area and a non-continuous area. According to the method, the icing numerical simulation precision is effectively improved, the boundary position of the two icing areas can be judged, and the method can be applied to icing numerical simulation.

Description

Technical Field

[0001] The invention relates to an icing partition determination method, in particular to an icing partition determination method based on water drop coverage, and belongs to the technical field of icing simulation of visual measurement. Background Art

[0002] Under certain meteorological conditions, there are a large number of supercooled water droplets in the clouds. Although the temperature of the supercooled water droplets is below zero, they still exist in liquid form. When an aircraft flies in the above-mentioned clouds, the supercooled water droplets will hit the surface of the aircraft and ice will form. Under different icing conditions, frost ice, clear ice or mixed ice may form on the aircraft. When frost ice forms, the supercooled water droplets will all freeze into ice after impact; when clear ice forms, the supercooled water droplets will not all freeze after impact, and the unfrozen liquid water will form a thin water film on the ice surface. The water film flows along the ice surface and gradually freezes at different rates; but no matter what type of icing situation, there is a certain zoning phenomenon on the surface.

[0003] In the prior art, the ice surface is usually divided into a rough ice formation zone, a feather ice formation zone, and the boundary between the two. The ice in the rough ice formation zone is continuous, and the roughness is relatively evenly distributed on its surface, while the ice in the feather ice formation zone is discontinuous, and discontinuously distributed ice particles or ice protrusions are formed in the initial stage of ice formation, and continue to grow to form feather ice. In the initial stage of ice formation, a relatively obvious boundary is formed between the rough ice formation zone and the feather ice formation zone. For the rough ice formation zone, since the ice formation is continuous, a relatively mature ice model has been established, but for the feather ice formation zone, there is no effective numerical simulation method. Although the ice formation in the feather ice formation zone cannot be numerically simulated, the judgment of the boundary position between the rough ice formation zone and the feather ice formation zone plays a very critical role in improving the accuracy of numerical simulation of ice formation. At present, there is no simple and fast method for determining the boundary position between the rough ice formation zone and the feather ice formation zone.

[0004] In summary, a method for determining ice partitions based on water droplet coverage is needed. Summary of the invention

[0005] A brief overview of the present invention is provided below in order to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to identify key or important parts of the present invention, nor is it intended to limit the scope of the present invention. Its purpose is merely to present certain concepts in a simplified form as a prelude to a more detailed description discussed later.

[0006] In view of this, in order to solve the problem of low accuracy of numerical simulation of icing caused by the inability of traditional icing models in the prior art to distinguish between continuous icing areas and discontinuous icing areas, the present invention provides an icing zoning determination method based on water droplet coverage.

[0007] The technical solution is as follows: A method for determining ice partitions based on water drop coverage, comprising the following steps: S1. The water drop coverage calculation formula is defined as the ratio of the sum of the cross-sectional areas of all water droplets per unit time to their impact area; S2. The ice surface is divided into a continuous ice zone, a discontinuous ice zone, and a zone boundary between the continuous ice zone and the discontinuous ice zone, and a relationship for determining the ice surface zone is obtained based on the relationship between the water droplet coverage and the typical characteristic constant; S3. According to the relationship formula for determining the icing surface partition, let the water droplet coverage be equal to the typical characteristic constant, and obtain the critical value of the water droplet collection coefficient corresponding to the typical characteristic constant; S4. Obtain the distribution characteristics of the water droplet collection coefficient in the water droplet impact area through experimental measurement or simulation calculation, and determine the location of the critical value of the water droplet collection coefficient, that is, the partition boundary between the ice continuous area and the ice discontinuous area.

[0008] Furthermore, in S2, the relationship for determining the ice surface partition is expressed as: when the water droplet coverage is Equal to the typical characteristic constant When , its location represents the partition boundary between the continuous freezing zone and the discontinuous freezing zone; when the water drop coverage Greater than the typical characteristic constant When , its location belongs to the continuous ice zone; when the water drop coverage Less than the typical characteristic constant ,Right now When , its location belongs to the icing discontinuous zone.

[0009] Furthermore, in S3, the water drop coverage is set to Equal to the typical characteristic constant , typical characteristic constant Corresponding critical value of droplet collection coefficient It is expressed as: ; in, is the liquid water content, its unit is g / m 3 , is the diameter of the water droplet, its unit is μm, is the air flow speed, the unit is m / s; When the droplet collection coefficient Equal to the critical value of the droplet collection coefficient When , its location represents the partition boundary between the continuous freezing zone and the discontinuous freezing zone; when the droplet collection coefficient Greater than the critical value of the droplet collection coefficient When , its location belongs to the continuous ice zone; when the water droplet collection coefficient Less than the critical value of the droplet collection coefficient When , and its location belongs to the ice discontinuous zone.

[0010] The beneficial effects of the present invention are as follows: the present invention defines the concept of water droplet coverage and its calculation formula, calculates the specific value of the water droplet coverage under given freezing conditions, and establishes a specific quantitative judgment criterion for the position of the partition boundary between the ice continuous area (rough area) and the ice discontinuous area (feather-like area) on the surface of an object, which is used to determine the partition boundary between the ice continuous area and the ice discontinuous area on the surface of an object. The present invention can be applied to the fields of ice mechanism research, ice test analysis and ice simulation calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 A schematic diagram of a flow chart of an ice partition determination method based on water droplet coverage; Figure 2 Schematic diagram of the distribution of droplet collection coefficient of NACA0012 airfoil under given icing conditions; Figure 3 It is a schematic diagram of the location of the critical value of the water droplet collection coefficient under given icing conditions; Figure 4 Schematic diagram of the comparison between the 3-minute icing surface and the critical value of the droplet collection coefficient in the NACA0012 airfoil icing wind tunnel under given icing conditions. DETAILED DESCRIPTION

[0012] In order to make the technical solutions and advantages of the embodiments of the present invention more clearly understood, the exemplary embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than an exhaustive list of all the embodiments. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0013] refer to Figure 1-Figure 4The present embodiment is described in detail, a method for determining ice partitions based on water droplet coverage, specifically comprising the following steps: S1. The water droplet coverage calculation formula is defined as the ratio of the sum of the cross-sectional areas of all water droplets per unit time to their impact area. The specific value of the water droplet coverage depends on the airflow, icing conditions and the impact position of the water droplets. S2. The ice surface is divided into an ice continuous area (rough area), an ice discontinuous area (feather area), and a partition boundary between the ice continuous area and the ice discontinuous area. According to the relationship between the water droplet coverage and the typical characteristic constant, a relationship formula for determining the ice surface partition is obtained; S3. According to the relationship formula for determining the icing surface partition, let the water droplet coverage be equal to the typical characteristic constant, and obtain the critical value of the water droplet collection coefficient corresponding to the typical characteristic constant; S4. Obtain the distribution characteristics of the water droplet collection coefficient in the water droplet impact area through experimental measurement or simulation calculation, and determine the location of the critical value of the water droplet collection coefficient, which is the partition boundary between the ice continuous area and the ice discontinuous area.

[0014] Furthermore, in S2, the relationship for determining the ice surface partition is expressed as: when the water droplet coverage is Equal to the typical characteristic constant When , its location represents the partition boundary between the continuous freezing zone and the discontinuous freezing zone; when the water drop coverage Greater than the typical characteristic constant When , which means that the number of water droplets in the airflow can completely cover the impact area. Its location belongs to the continuous ice formation area, and the ice surface mainly presents a relatively uniform roughness distribution. When the water droplet coverage rate Less than the typical characteristic constant ,Right now When , it means that the number of water droplets in the airflow cannot completely cover the impact area. Its location belongs to the ice discontinuity zone, and the ice is mainly composed of feather ice.

[0015] Furthermore, in S3, the water drop coverage is set to Equal to the typical characteristic constant , typical characteristic constant Corresponding critical value of droplet collection coefficient It is expressed as: ; in, is the liquid water content, its unit is g / m 3 , is the diameter of the water droplet, its unit is μm, is the air flow speed, the unit is m / s; When the droplet collection coefficient Equal to the critical value of the droplet collection coefficient When , its location represents the partition boundary between the continuous freezing zone and the discontinuous freezing zone; when the droplet collection coefficient Greater than the critical value of the droplet collection coefficient When , its location belongs to the continuous ice zone; when the water droplet collection coefficient Less than the critical value of the droplet collection coefficient When , and its location belongs to the ice discontinuous zone.

[0016] Specifically, the droplet collection coefficient The water drop coverage rate varies with the change of the water drop impact position. and droplet collection coefficient There is a one-to-one correspondence; Under normal icing conditions, assuming typical characteristic constants , then the corresponding critical value of the droplet collection coefficient is It is expressed as: ; In this embodiment, the liquid water content is 0.47g / m 3 , water droplet diameter 19.2μm, air flow speed is 75m / s, then the water drop coverage The critical value of the droplet collection coefficient when it is equal to 1 ; refer to Figure 2 , shows the distribution of droplet collection coefficient and critical value of droplet collection coefficient of NACA0012 airfoil under given icing conditions, S is the arc length coordinate of the airfoil surface, unit is m; refer to Figure 3 , showing the position of the critical value of the droplet collection coefficient on the upper and lower surfaces of the NACA0012 airfoil under given icing conditions, which respectively represent the specific position of the partition boundary between the icing continuous area and the icing discontinuous area on the upper and lower surfaces of the NACA0012 airfoil; refer to Figure 4 , showing the comparison of the 3-minute ice surface and the critical value of the droplet collection coefficient in the NACA0012 airfoil icing wind tunnel under given icing conditions. The red dot is the partition boundary between the icing continuous zone and the icing discontinuous zone.

[0017] Although the present invention has been described according to a limited number of embodiments, it will be apparent to those skilled in the art, with the benefit of the above description, that other embodiments may be envisioned within the scope of the invention thus described. In addition, it should be noted that the language used in this specification is selected primarily for readability and teaching purposes, rather than for explaining or defining the subject matter of the present invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the present invention is illustrative, not restrictive, with respect to the scope of the present invention, which is defined by the appended claims.

Claims

1. A method for determining ice partitions based on water drop coverage, characterized in that: The following steps are involved: S1. The water drop coverage calculation formula is defined as the ratio of the sum of the cross-sectional areas of all water droplets per unit time to their impact area; S2. The ice surface is divided into a continuous ice zone, a discontinuous ice zone, and a zone boundary between the continuous ice zone and the discontinuous ice zone, and a relationship for determining the ice surface zone is obtained based on the relationship between the water droplet coverage and the typical characteristic constant; S3. According to the relationship formula for determining the icing surface partition, let the water droplet coverage be equal to the typical characteristic constant, and obtain the critical value of the water droplet collection coefficient corresponding to the typical characteristic constant; S4. Obtain the distribution characteristics of the water droplet collection coefficient in the water droplet impact area through experimental measurement or simulation calculation, and determine the location of the critical value of the water droplet collection coefficient, that is, the partition boundary between the ice continuous area and the ice discontinuous area.

2. The method for determining ice partitions based on water drop coverage according to claim 1, characterized in that: In S2, the relationship for determining the ice surface partition is expressed as: when the water droplet coverage is equal to the typical characteristic constant When , its location represents the partition boundary between the continuous freezing zone and the discontinuous freezing zone; when the water drop coverage Greater than the typical characteristic constant When , its location belongs to the continuous ice zone; when the water drop coverage Less than the typical characteristic constant ,Right now When , its location belongs to the icing discontinuous zone.

3. The method for determining ice partitions based on water drop coverage according to claim 2, characterized in that: In S3, let the water drop coverage ratio Equal to the typical characteristic constant , typical characteristic constant Corresponding critical value of droplet collection coefficient It is expressed as: ； in, is the liquid water content, its unit is g / m 3 , is the water droplet diameter, its unit is μm, is the air flow speed, the unit is m / s; When the droplet collection coefficient Equal to the critical value of the droplet collection coefficient When , its location represents the partition boundary between the continuous freezing zone and the discontinuous freezing zone; when the droplet collection coefficient Greater than the critical value of the droplet collection coefficient When , its location belongs to the continuous ice zone; when the water droplet collection coefficient Less than the critical value of the droplet collection coefficient When , and its location belongs to the ice discontinuous zone.

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