Gas valve group chamber fan and air brake type selection method suitable for LNG ship

Abstract

The invention relates to the technical field of LNG (Liquefied Natural Gas) ships, in particular to a gas valve bank chamber fan and air brake type selection method suitable for an LNG ship. The method comprises the steps that firstly, the minimum required air volume is calculated according to the volume of a gas valve bank chamber and the required air exchange frequency in unit time; 2, selecting a plurality of fans meeting the minimum required air volume, drawing up a plurality of air brakes with different net flow areas, keeping the room at a set pressure value, and analyzing the flow field model of the gas valve bank room by using CFD software; 3, establishing a fan outlet exhaust duct model, and analyzing by using CFD software to obtain the relationship between the fan demand static pressure and the fan air volume under different air brakes; and 4, the models of the fan and the air brake are selected from the fan static pressure requirement meeting the ventilation requirement at the same time, and then the problem that in the prior art, the negative pressure and ventilation requirements in the gas valve set chamber need to be kept through the fan and the air brake, and selection of the fan and the air brake contradicts with each other can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of LNG ships, and in particular to a method for selecting a fan and a damper in a gas valve group room suitable for LNG ships. Background Art

[0002] In view of the special potential risks of LNG dual-fuel ships, classification societies and other standard-setting departments have put forward a number of design requirements to ensure the standardization of the design of this type of ship and minimize safety hazards. Among them, for the gas valve group room, due to its high potential risk of gas leakage, it is necessary to ensure good ventilation, stable negative pressure and timely leakage alarm, and the specification requirements are particularly strict. Usually, an exhaust port is opened on the side wall of the gas valve group room, a damper is installed on the exhaust port, and a fan is installed outside the gas valve group room. The fan is used to continuously suck the gas valve group room to keep the gas valve group room in a state of continuous ventilation.

[0003] That is to say, the gas valve group room has negative pressure and ventilation frequency requirements. Generally speaking, considering the negative pressure and ventilation requirements of the gas valve group room, a larger fan exhaust volume needs to be set to maintain an efficient ventilation frequency. A good room negative pressure requires a smaller room inlet grille flow area. However, the increase in the fan exhaust volume will increase the wind speed in the fan inlet and outlet pipelines, increase the corresponding pipeline pressure loss, and also increase the cost of using the fan. The reduction in the room inlet grille flow area will also cause changes in the pressure loss in the room, increasing the exhaust resistance. It may even happen that the fan meets the exhaust volume requirements during the design process, but under the influence of exhaust resistance or fan static pressure and other factors, the exhaust volume does not reach the design air volume during actual operation. How to choose a suitable fan and damper is the key to designing a gas valve group room. Summary of the invention

[0004] In view of this, the present invention provides a method for selecting a fan and a damper in a gas valve group room of an LNG ship, so as to solve the problem in the prior art that a fan and a damper are needed to maintain the negative pressure and ventilation requirements in the gas valve group room, while the selection of the fan and the damper are contradictory.

[0005] A method for selecting fans and dampers for a gas valve group room of an LNG ship comprises the following steps: step 1: calculating the minimum required air volume according to the volume of the gas valve group room and the number of ventilation times per unit time required; step 2: selecting multiple fans that meet the minimum required air volume, and setting multiple dampers with different net flow areas to keep the room at a set pressure value; using CFD software to analyze the flow field model of the gas valve group room, and obtaining the room outlet static pressure P under different working conditions. S2 And the required air volume of different fans under different wind gate net flow areas; Step 3: Establish the fan outlet exhaust duct model, and use CFD software to analyze and output the fan outlet static pressure PS1 , calculate the fan required static pressure P S1 -P S2 , get the relationship between the fan required static pressure and fan air volume under different dampers; Step 4: Select the fan and damper models from those that simultaneously meet the ventilation frequency requirements, the negative pressure in the gas valve group room, and the fan static pressure requirements.

[0006] Furthermore, when calculating the minimum required air volume, the calculation is performed based on at least 1.1 times the volume of the gas valve group chamber.

[0007] Furthermore, the wind gate has a square opening, and the side length of the wind gate is selected to be between 0.5-0.9m.

[0008] Furthermore, in the process of selecting the models of the fan and the damper, a chart is generated showing the relationship between the required static pressure of the fan and the air volume of the fan under different dampers, an area meeting the selection criteria is delineated in the chart, and points within the area are selected.

[0009] The beneficial effects of the method for selecting a fan and a damper in a gas valve group chamber of an LNG ship in the present invention are as follows: in the method for selecting a fan and a damper in a gas valve group chamber of an LNG ship in the present invention, the minimum air volume of the fan is first calculated by volume. If the number of ventilation times per unit time is to be met, the minimum air volume cannot be less than the product of the volume of the gas valve group chamber and the number of ventilation times per unit time; since it is necessary to study and analyze the gas valve group chamber, in order to speed up the experimental progress and facilitate the acquisition of experimental results, CFD software is used to simulate and analyze the gas valve group chamber, so as to facilitate the acquisition of different results; since the factors affecting the ventilation effect of the gas valve group chamber include the fan model and the net flow area of ​​the damper, a plurality of fans that meet the above-mentioned minimum air volume and a plurality of dampers with different net flow areas are selected, and CFD software is used for simulation. Since a model of the gas valve group chamber is already available, the real working condition can be simulated in combination with the model of the gas valve group chamber, the fan type and the net flow area of ​​the damper, and the static pressure P at the room outlet under different working conditions can be obtained. S2 As well as the air volume of different fans under different wind gate net flow areas; since the shape, length and diameter of the exhaust duct can affect the air outlet resistance, the fan will also be affected by the air outlet resistance during actual use, it is also necessary to establish a model of the real exhaust duct and simulate the exhaust duct model in the CFD software, output the fan outlet static pressure PS1, and calculate the fan demand static pressure P S1 -P S2, and the relationship between the fan required static pressure and the fan air volume under different dampers is obtained; in the process of simulation, the coordination forms of multiple sets of fans and dampers are simulated, and the results that meet various parameters can be selected from the simulation results, that is, each parameter is quantified, thereby solving the problem in the prior art that fans and dampers are needed to maintain the negative pressure and ventilation requirements in the gas valve group room, while the selection of fans and dampers is contradictory. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0011] Figure 1 The figure is a schematic diagram of a ventilation system for a method for selecting a fan and a wind gate in a gas valve group room of an LNG ship according to the present invention (wherein the arrow represents the direction of wind flow);

[0012] Figure 2 It is a schematic diagram of simulation using CFD software in the method for selecting the fan and damper in the gas valve group room applicable to LNG ships in the present invention;

[0013] Figure 3 The corresponding relationship between the flow area and the minimum design air volume of the fan is obtained by using CFD software to analyze in step 2 of the method for selecting the fan and wind gate of the gas valve group room applicable to LNG ships in the present invention;

[0014] Figure 4 yes Figure 3 The fan air volume that satisfies the set pressure of the gas valve group chamber is obtained through calculation;

[0015] Figure 5 The exhaust pipe model in step 3 of the method for selecting a fan and a damper in a gas valve group room applicable to an LNG ship in the present invention;

[0016] Figure 6 The fan outlet static pressure P is output by CFD flow field analysis of the fan exhaust pipeline in the third step of the method for selecting the fan and wind gate in the gas valve group room of the LNG ship in the present invention. S1 ;

[0017] Figure 7 The relationship curve between the required static pressure of the fan and the air volume of the fan under different net flow areas of the air lock obtained by analyzing step 3 of the method for selecting the fan and air lock for the gas valve group room of the LNG ship in the present invention;

[0018] Figure 8The selection range that meets the selection requirements in step 4 of the method for selecting a gas valve group room fan and a wind gate applicable to an LNG ship in the present invention;

[0019] Fig. 9 The standard flow chart of the method for selecting the fan and damper in the gas valve group room applicable to LNG ships in the present invention.

[0020] The meanings of the numbers in the figure are: 1. Gas valve group room; 2. Fan; 3. Exhaust duct. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0022] The terms used in this disclosure are for the purpose of describing specific embodiments only and are not intended to limit the disclosure. The singular forms of "a", "said" and "the" used in this disclosure and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0023] It should be understood that although the terms first, second, third, etc. may be used in the present disclosure to describe various information, such information should not be limited to these terms and should not be understood as indicating or implying relative importance. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present disclosure, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0024] In the description of the present invention, it is necessary to understand that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0025] In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection between two components. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0026] In the following description, the suffixes such as "module", "component" or "unit" used to represent elements are only used to facilitate the description of the present invention, and have no specific meanings. Therefore, "module" and "component" can be used interchangeably.

[0027] In order to better understand the technical solution of the present invention, the present invention is described in detail below with reference to the accompanying drawings.

[0028] In the embodiment 1 of the method for selecting a fan and a damper in a gas valve group room of an LNG ship (hereinafter referred to as the selection method), the present invention is applicable to:

[0029] In the selection method of the present invention, the minimum required air volume is calculated based on the required number of ventilation times per unit time and the volume that needs to be ventilated, and based on the minimum required air volume, several fans with actual air volumes greater than the minimum required air volume are selected for simulation, and then a plurality of wind gates with different net flow areas are used to participate in the simulation to obtain multiple groups of data, and the relationship between the flow area of ​​the wind gate and the fan air volume when the set pressure value of the room is met is obtained; then the exhaust duct model is added to analyze the relationship between the required static pressure and air volume of the fan, and finally selection is performed to select a suitable fan and wind gate combination that meets the requirements.

[0030] Specifically, Fig. 9 and Figure 1 As shown, in the selection method of the present invention, step 1 is first performed: Figure 2 As shown, a 1:1 model of the gas valve group chamber 1 in the three-dimensional software is established, which is convenient for calculating the volume of the gas valve group chamber 1 in the CFD software. The volume of the room is determined by the software calculation, that is, the volume that needs to be ventilated. At the same time, the establishment of the model of the gas valve group chamber 1 this time also facilitates the subsequent flow field analysis. According to the industry design specifications, the ventilation frequency per hour is set to 30 times, and then the ventilation volume required per unit time is calculated to obtain the minimum required air volume. It is worth noting that in the design process, in order to prevent various losses in the actual process, a margin is generally set. In this embodiment, when calculating the minimum required air volume, it is calculated at least according to 1.1 times the volume of the gas valve group chamber 1, so that even if losses occur due to other factors such as indoor sealing, the ventilation requirements can be met.

[0031] As a preferred technical solution, the three-dimensional flow field model is to input the 1:1 equal-size three-dimensional solid model established in the three-dimensional modeling platform into the Ansys Workbench software, and fill the room internal flow field model through the Fill operation. After filling, the total volume of the flow field in the room can be output as 450m3. According to the ventilation demand of at least 30 times per hour, the minimum air volume is determined as: 450×30=13500m 3 / h, add 10% margin, that is, the fan air volume needs to be controlled at 13500×110%=14850m 3 / h or more.

[0032] Of course, in other implementations, if unnecessary losses can be reduced in actual engineering, the actual volume can be calculated, or 1.05 times the actual volume can be calculated. Of course, if the expected losses are large, the actual volume can be calculated at 1.2 times the actual volume. Of course, in other implementations, the three-dimensional software modeling can be omitted first. Since the shape of the gas valve group chamber is generally regular, the volume of the gas valve group chamber can be directly calculated, and the three-dimensional model of the gas valve group chamber can be established in subsequent steps.

[0033] Then proceed to step two, according to the minimum required air volume calculated in step one, select multiple fans that can meet the minimum required air volume, and measure these multiple fans. During the use of the fan, its air volume is not fixed, and its air volume will change according to different usage conditions. For example, in actual use, the net flow area of ​​the wind gate can also affect the air volume of the fan, so multiple wind gates are also selected. In this embodiment, square wind gates are selected, and the side lengths of the wind gates are the more common 0.5m, 0.6m and 0.8m, respectively, which are tested in conjunction with the different fans that have been selected. In this embodiment, three types of fans are selected, and the working condition of fan 2 with three gears higher than the minimum air volume is 14000m 3 / h、17000m 3 / h、20000m 3 / h Of course, in other implementations, different fan types can also be selected. In actual use, it is necessary to maintain a certain negative pressure in the gas valve group room. When the negative pressure is maintained, once a gas leak occurs, the gas will not flow from the gas valve group room to other parts, but will be directly discharged through the fan to avoid the spread of danger. Therefore, when performing simulation, the pressure in the gas valve group room is maintained at a certain negative pressure. Specifically, in this embodiment, the negative pressure of the room is equal to -96pa. On this basis, simulation is performed to output the static pressure P of the room outlet under different working conditions. S2 And the negative pressure of the room P i , we can get the corresponding air volume under different wind damper net flow areas when the negative pressure in the room is equal to the alarm value of -96pa, such as Figure 3and Figure 4 shown.

[0034] Then proceed to step 3 to establish the fan outlet exhaust pipe model, such as Figure 5 Different exhaust ducts mean different exhaust resistances, and exhaust resistance can affect the use of the fan. That is, the fan needs to be able to maintain the static pressure in the room within a certain range and maintain the required exhaust volume while overcoming the resistance. This is crucial for the fan itself. Specifically, a fan outlet exhaust duct model is established, and then flow field analysis is performed in CFD software to output the fan outlet static pressure P S1 , calculate the fan required static pressure is P S1 -P S2 , and then the relationship between the fan required static pressure and fan air volume under different wind gate net flow areas can be obtained, such as Figure 6 Combining the data obtained in step 2 and step 3, the coordinate axis is established with the fan flow rate as the horizontal coordinate and the fan required static pressure as the vertical coordinate, and then the corresponding curve between the fan required static pressure and the fan air volume under different wind gates (i.e., different net flow areas) can be obtained, as shown in Figure 7 shown.

[0035] After that, step 4, comprehensive selection, needs to be carried out. In the selection process, it is necessary to combine the required air volume and required static pressure of the fan at the same time, so as to meet the ventilation frequency requirement per unit time and the negative pressure requirement in the room. Specifically, the ventilation frequency required in this embodiment is 30 times per hour, and the negative pressure to be maintained in the room is -96Pa. In the above figure, the required air volume under different net flow areas of the wind damper is marked and compared with the simulation results. It can be seen from the figure that the simulation results on the right side of the required air volume meet the requirements. When the net flow area of ​​the wind damper is 0.64m 2 When the required air volume is too large, if the required air volume is to be met, the required static pressure of the fan will be too large, which will greatly increase the cost of the fan, so it is not suitable for use. When the net flow area of ​​the wind gate is 0.25m 2 When the air volume is too low, it is far lower than the air volume required to meet the ventilation requirements of 30 times. If the ventilation frequency is to meet the design requirements, the negative pressure in the room will be too large, and even the door opening will fail. The required static pressure is too large, which is not suitable. Therefore, the net flow area of ​​the damper selection is first determined to be 0.36 square meters. Then, the operating point with the coordinates marked in the lower left corner of the shaded part is the minimum fan air volume and the lowest fan static pressure value, which can be used for fan selection.

[0036] It should be clear that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A method for selecting fans and dampers for gas valve group rooms of LNG ships, characterized in that: Step 1: Calculate the minimum required air volume according to the volume of the gas valve group room and the number of ventilation times per unit time required; Step 2: Select multiple fans that meet the minimum required air volume, formulate multiple dampers with different net flow areas, keep the room at the set pressure value, and use CFD software to analyze the flow field model of the gas valve group room to obtain the room outlet static pressure P under different working conditions. S2 And the required air volume of different fans under different wind gate net flow areas; Step 3: Establish the fan outlet exhaust duct model, and use CFD software to analyze and output the fan outlet static pressure P S1 , calculate the fan required static pressure P S1 -P S2 , get the relationship between the fan required static pressure and fan air volume under different dampers; Step 4: Select the fan and damper models from those that simultaneously meet the ventilation frequency requirements, the negative pressure in the gas valve group room, and the fan static pressure requirements.

2. The method for selecting a fan and a damper in a gas valve group room of an LNG ship according to claim 1, characterized in that: When calculating the minimum required air volume, it should be calculated at least 1.1 times the volume of the gas valve group chamber.

3. The method for selecting a fan and a damper for a gas valve group room of an LNG ship according to claim 1 or 2, characterized in that: The wind gate uses a square opening, and the side length of the wind gate is selected between 0.5-0.9m.

4. The method for selecting a fan and a damper in a gas valve group room of an LNG ship according to claim 1 or 2, characterized in that: In the process of selecting the fan and damper models, a chart is generated to show the relationship between the fan required static pressure and the fan air volume under different dampers. An area that meets the selection criteria is delineated in the chart, and points within the area are selected.

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