A method for guiding the manufacture of a draw resistance standard rod

Abstract

The present invention provides a method for guiding the manufacture of a draw resistance standard rod. Given the total flow rate, the initial flow rate of each capillary pore is calculated, the flow velocity of each capillary pore is calculated, the flow resistance of each capillary pore is calculated, the pressure drop of the first capillary pore is calculated, the flow rates of the remaining capillary pores are calculated, the flow rate of the first capillary pore is obtained, and the above calculation process starts an iterative loop until the residual converges to a stable state; through the above steps, a relatively accurate draw resistance value can be obtained based on the diameter d and length L of the capillary pores. This prediction method establishes a mathematical model for the internal gas flow of the draw resistance standard rod, obtains the relationship between the pore diameter and length of the capillary pores of the draw resistance standard rod and the flow rate and draw resistance, and further guides the manufacture of the draw resistance standard rod, providing a mathematical and physical support for the design of the draw resistance standard rod.

Description

Technical Field

[0001] The present invention relates to the technical field of standardized detection of tobacco equipment. Specifically, it relates to a method for guiding the manufacture of draw resistance standard rods. Background Art

[0002] The draw resistance of cigarettes and the pressure drop of filter rods have a significant impact on the sensory quality and smoke components of cigarettes, and their values are measured by draw resistance and filter rod pressure drop detection equipment.

[0003] The draw resistance standard rod is a standard instrument for calibrating draw resistance and filter rod pressure drop detection equipment, and its accuracy and stability directly affect the test results of draw resistance and filter rod pressure drop.

[0004] GB / T 22838.5-2009 "Determination of physical properties of cigarettes and filter rods - Part 5: Draw resistance of cigarettes and pressure drop of filter rods" stipulates the basic characteristics of draw resistance standard parts: 1. The pressure drop transfer standard part should be made of inert materials that are not affected by the service life; 2. It should be very similar to the typical cigarette size and shape; 3. It has a repeatable value of draw resistance or pressure drop; 4. It is not easily affected by the environment and changes; 5. The air flow through the pressure drop standard part is in a laminar flow state.

[0005] The pore diameter and length of the capillary through holes in the draw resistance standard rod directly determine the draw resistance value of the draw resistance standard rod.

[0006] Currently, the common draw resistance standard rods on the market mainly rely on experience to design the diameter and length of the capillary through holes, and are formed by one-time encapsulation of capillary glass tubes and epoxy or acrylic resin, without theoretical basis as a guide, and the qualified rate is relatively low.

[0007] In order to make the production of draw resistance standard rods more stable and precise and provide data support for the production of draw resistance standard rods has become an urgent technical problem to be solved by those skilled in the art. Summary of the Invention

[0008] The purpose of the present invention is to overcome the deficiencies of the prior art, and thus provide a method for guiding the manufacture of draw resistance standard rods, which establishes a mathematical model for the internal air flow of the draw resistance standard rod, obtains the relationship between the pore diameter and length of the capillary holes of the draw resistance standard rod and the flow rate and draw resistance, and provides guidance and mathematical support for the manufacture of draw resistance standard rods.

[0009] In order to achieve the above purpose, the technical solution adopted by the present invention is: a method for guiding the manufacture of draw resistance standard rods, including the following steps:

[0010] Step 1) Given the total flow rate Q t ;

[0011] Step 2) Calculate the initial flow rate of each capillary hole

[0012] where N is the number of capillary pores;

[0013] Step 3) Calculate the flow velocity of each capillary pore

[0014] where A k is the cross-sectional area of each capillary pore;

[0015] Step 4) Calculate the flow resistance of each capillary pore:

[0016]

[0017] where, Re is the Reynolds coefficient of the gas in the capillary pore;

[0018] L is the total length of the suction resistance standard rod;

[0019] L D is the length of the non-fully developed section;

[0020] ρ is the gas density;

[0021] d is the capillary pore diameter;

[0022]

[0023] Step 5) Calculate the pressure drop of the first capillary pore, ΔP 1 = R 1 ·Q 1 2 ;

[0024] Step 6) Calculate the flow rates of the remaining capillary pores,

[0025] Step 7) Calculate the flow rate of the first capillary pore,

[0026] Step 8) Return to Step 3) and start an iterative loop, iterating until the residual converges to a stable value;

[0027] Through the above steps, a relatively accurate suction resistance value ΔP = ΔP 1 .

[0028] Based on the above, in Step 4), is obtained through the following steps:

[0029] The fluid flows into the capillary tube in an incompressible manner at a uniform velocity and undergoes laminar flow. Under the viscous action of the capillary tube, a boundary layer symmetric about the tube axis is formed in the inlet section, and fully developed laminar flow is formed at the end of the inlet section;

[0030] Among them, the length of the dimensionless development section is expressed as:

[0031] ξ e = 0.0288Re (1)

[0032] The length of the underdeveloped section is expressed as:

[0033] L D = 0.0288Re·d (2)

[0034] The pressure loss coefficient of the underdeveloped section is expressed as:

[0035]

[0036] Among them, P 0 is the inlet pressure of the circular pipe, P is the pressure at a certain point, and u m is the average flow velocity;

[0037] From formulas (1)-(3), the pressure drop of the underdeveloped section of the capillary pores in the suction resistance standard rod can be obtained and expressed as:

[0038]

[0039] The underdeveloped section is divided into n segments, and the pressure drop from the inlet to the i-th segment can be expressed as:

[0040]

[0041] The pressure loss coefficient λ pi from the capillary inlet to the i-th segment and the pressure loss coefficient λ i of the i-th segment have the following relationship:

[0042]

[0043] Among them, λ p is obtained by looking up a table;

[0044] When the boundary layers intersect at the circular pipe wall, the pipe length that the gas passes through is L D = 0.0288Re·d. At this time, λ p = 4, that is

[0045] Based on the above, in step 5), the pressure drop formula of the first capillary pore is obtained through the following steps:

[0046] Also, the volume flow rate: Q = u m ·A (7)

[0047] u m is the average flow velocity, and A is the cross-sectional area of the capillary pore;

[0048] Combined with formula (4), it can be obtained that:

[0049]

[0050] Among them, the flow resistance R is:

[0051]

[0052] Among them, L is the total length of the standard rod.

[0053] The present invention has prominent substantive features and remarkable progress compared with the prior art. Specifically, through mathematical, physical, and chemical operations, the theoretical knowledge of gas flowing through a circular tube, and the existing publicly available technical materials, the present invention decomposes the process of gas passing through the capillary pores into an underdeveloped section and a fully developed section, and based on the mathematical, physical, and chemical calculations of gas pressure in these two processes, obtains a series of operation formulas for pressure drop;

[0054] Then, based on the obtained operation formulas, a mathematical model of gas flow in the suction resistance standard rod is constructed. Given the total flow rate, the pressure drop and flow rate of a single capillary pore are calculated, and the mathematical model is iterated until the residual approaches stability. Since the model involves the length and pore diameter data of the capillary pores, through the relationship between suction resistance (pressure drop), flow rate, length, and pore diameter, the relevant production indexes of the suction resistance standard rod are guided, and then products meeting the requirements are produced, providing a guiding basis and mathematical support for the production of the products. Description of the Drawings

[0055] Figure 1 is a schematic diagram of the boundary layer development of gas passing through the suction resistance standard rod in the present invention. Detailed Embodiments

[0056] The technical solutions of the present invention will be further described in detail below through specific embodiments.

[0057] As Figure 1 shown, in existing theoretical research, there is research on the correction coefficient of the entrance section effect of laminar flow and turbulent flow in a circular tube, which points out that the assumptions are as follows: 1. The fluid is incompressible, the flow is steady, the entrance of the circular tube is smooth, and the velocity at the entrance is uniform as a constant; 2. A boundary layer symmetric about the tube axis is formed in the entrance section. The flow in the boundary layer is laminar or turbulent, and the flow outside the boundary layer is potential flow; 3. The flow at the end of the entrance section forms fully developed laminar flow or fully developed time-averaged turbulent flow, and its velocity distribution is in a parabolic law or approximately in a power-law velocity law.

[0058] This application is based on this theoretical basis. That is, an incompressible fluid flows into the capillary at a uniform velocity and undergoes laminar flow. Under the viscous action of the capillary, a boundary layer symmetrical about the tube axis is formed in the inlet section, and fully developed laminar flow is formed at the end of the inlet section.

[0059] Among them, the length of the dimensionless development section is expressed as:

[0060] ξ e = 0.0288Re (1)

[0061] Re is the Reynolds coefficient of the gas in the capillary;

[0062] The length of the underdeveloped section is expressed as:

[0063] L D = 0.0288Re·d (2)

[0064] d is the diameter of the capillary;

[0065] The pressure loss coefficient of the underdeveloped section is expressed as:

[0066]

[0067] Among them, P 0 is the inlet pressure of the circular tube, P is the pressure at a certain point, and u m is the average flow velocity;

[0068] From formulas (1)-(3), the pressure drop of the underdeveloped section of the capillary in the suction resistance standard rod can be obtained and expressed as:

[0069]

[0070] The underdeveloped section is divided into n segments, and the pressure drop from the inlet to the i-th segment can be expressed as:

[0071]

[0072] The pressure loss coefficient λ pi from the capillary inlet to the i-th segment and the pressure loss coefficient λ i of the i-th segment have the following relationship:

[0073]

[0074] Among them, λ p is obtained by looking up a table;

[0075] Δ 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 ξ / Re 0.0001 0.0005 0.0013 0.0026 0.0045 0.0072 0.0109 0.0157 0.0216 0.0288 <![CDATA[λ p > 1.1438 1.3111 1.5055 1.7313 1.9930 2.2956 2.6439 3.0421 3.4937 4

[0076] Table 1 Pressure Loss Coefficient Table

[0077] When the boundary layer intersects at the wall of the circular tube, the tube length that the gas passes through is L D = 0.0288Re·d, and at this time, λ p = 4, that is

[0078] Based on the formula deduced from the above mathematical, physical, and chemical deductions as the basis, a mathematical model is designed, and the process is as follows:

[0079] Step 1) Specify the total flow rate Q t ;

[0080] Step 2) Calculate the initial flow rate of each capillary pore

[0081] where N is the number of capillary pores;

[0082] Step 3) Calculate the flow velocity of each capillary pore

[0083] where A k is the cross-sectional area of each capillary pore;

[0084] Step 4) Calculate the flow resistance of each capillary pore:

[0085]

[0086] where, Re is the Reynolds coefficient of the gas in the capillary pore;

[0087] L is the total length of the suction resistance standard rod;

[0088] L D is the length of the non-fully developed section;

[0089] ρ is the gas density;

[0090] d is the diameter of the capillary pore;

[0091]

[0092] Step 5) Calculate the pressure drop of the first capillary pore, ΔP 1 = R 1 ·Q 1 2 ;

[0093] The pressure drop formula of the first capillary pore is obtained through the following steps:

[0094] Also, the volume flow rate: Q = u m ·A (7)

[0095] u m is the average flow velocity, and A is the cross-sectional area of the capillary pore;

[0096] Combined with formula (4), it can be obtained that:

[0097]

[0098] Among them, the flow resistance R is:

[0099]

[0100] Among them, L is the total length of the standard rod.

[0101] Step 6) Calculate the flow rates of the remaining capillary pores

[0102] Step 7) Calculate the flow rate of the first capillary pore

[0103] Step 8) Return to step 3) and start the iterative loop, and iterate until the residual approaches stability;

[0104] Through the above steps, according to the diameter d and length L of the capillary pores, a relatively accurate suction resistance value ΔP = ΔP 1 .

[0105] In this embodiment, in step 1), the given total flow rate is provided by a gas flow generator, which can provide a stable and controllable total gas flow rate.

[0106] This method is mainly used to guide the production process, aiming to find the correlation between the suction resistance required for the suction resistance standard rod, the length of the suction resistance standard rod, and the diameter of the capillary pores, so as to determine the parameters required for production and obtain the standard rod product with the required suction resistance.

[0107] Specifically, during use, the mathematical model can be trained by specifying an existing suction resistance standard rod, or the mathematical model can be trained by setting parameters. After the training is completed, by inputting the desired suction resistance value, the relevant physical dimensions of the corresponding suction resistance standard rod can be output, and then the production process can be guided to improve the yield rate.

[0108] The suction resistance standard rod contains multiple capillary pores. The pore diameters and lengths of the multiple capillary pores are the same, and most of them are distributed in a circular shape.

[0109] The capillary pores of the suction resistance standard rod are prepared from capillary glass tubes, and the rod body of the suction resistance standard rod is encapsulated with epoxy resin or acrylic resin. Or the capillary pores and the rod body of the suction resistance standard rod are integrally prepared from quartz glass.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: it is still possible to modify the specific implementation manners of the present invention or perform equivalent replacements for some technical features; without departing from the spirit of the technical solutions of the present invention, they should all be covered within the scope of the technical solutions claimed by the present invention.

Claims

1. A method for guiding the manufacture of a draw resistance standard rod, characterized in that: It includes the following steps: Step 1): Given the total flow rate Q t ; Step 2) Calculate the initial flow rate of each capillary pore where N is the number of capillary pores; Step 3) Calculate the flow rate of each capillary pore where A k is the cross-sectional area of each capillary pore; Step 4) Calculate the flow resistance of each capillary pore: Among them, Re is the Reynolds coefficient of the gas in the capillary pores; L is the total length of the draw resistance standard rod; L D is the length of the underdeveloped section; ρ is the gas density; d is the diameter of the capillary pore; Step 5) Calculate the pressure drop of the first capillary pore, ΔP 1 = R 1 ·Q 1 2 ; Step 6) Calculate the flow rates of the remaining capillary pores, Step 7) Calculate the flow rate of the first capillary pore. Step 8) Return to Step 3) and start an iterative loop, iterating until the residual tends to be stable; Through the above steps, a relatively accurate suction resistance value ΔP = ΔP can be obtained based on the diameter d and length L of the capillary pores 1 .

2. The method for guiding the manufacture of a draw resistance standard rod according to claim 1, characterized in that: In step 4), is obtained through the following steps: The fluid flows into the capillary tube incompressibly at a uniform speed to perform laminar flow. Under the viscous action of the capillary tube, a boundary layer axisymmetric with the tube is formed in the inlet section, and the flow at the end of the inlet section forms a fully developed laminar flow; Among them, the length of the dimensionless development section is expressed as: ξ e = 0.0288Re (1) The length of the underdeveloped section is expressed as: L D = 0.0288Re·d (2) The pressure loss coefficient of the underdeveloped section is expressed as: Among them, P 0 is the inlet pressure of the circular pipe, P is the pressure at a certain point, and u m is the average flow velocity; From formulas (1)-(3), the pressure drop of the underdeveloped section of the capillary pores in the draw resistance standard rod can be obtained and expressed as: The underdeveloped section is divided into n segments, and the pressure drop from the inlet to the i-th segment can be expressed as: The pressure loss coefficient λ from the capillary inlet to the i-th section pi and the pressure loss coefficient λ of the i-th section i are related as follows: where λ p is obtained by looking up a table; When the boundary layer intersects at the wall of the circular tube, the tube length that the gas passes through is L D = 0.0288Re·d, and at this time λ p = 4, that is 3. The method for guiding the manufacture of a draw resistance standard rod according to claim 2, characterized in that: In Step 5), the pressure drop formula of the first capillary pore is obtained through the following steps: And volumetric flow rate: Q = u m ·A(7) u m is the average flow velocity, and A is the cross-sectional area of the capillary pore; Combined with formula (4), it can be obtained that: Among them, the flow resistance R is: where L is the total length of the standard rod.

4. The method for guiding the manufacture of a draw resistance standard rod according to any one of claims 1-3, characterized in that: The draw resistance standard rod contains multiple capillary pores, and the pore diameters and lengths of the multiple capillary pores are the same.

5. The method for guiding the manufacture of a draw resistance standard rod according to any one of claims 1-3, characterized in that: The capillary pores of the draw resistance standard rod are prepared from capillary glass tubes, and the rod body of the draw resistance standard rod is encapsulated with epoxy resin or acrylic resin.

6. The method for guiding the manufacture of a draw resistance standard rod according to any one of claims 1-3, characterized in that: The capillary pores and the rod body of the draw resistance standard rod are integrally prepared from fused quartz glass.

7. The method for guiding the manufacture of a draw resistance standard rod according to any one of claims 1-3, characterized in that: The demarcation point between the underdeveloped section and the fully developed section, that is, the end position of the length of the underdeveloped section, is based on the position where the boundary layer intersects at the tube wall.

8. The method for guiding the manufacture of a draw resistance standard rod according to any one of claims 1-3, characterized in that: In Step 1), the given total flow rate is provided by a gas flow generator.

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