Sensor arrangement method of vehicle-mounted refrigerator refrigerant leakage early warning system

Abstract

The invention discloses a sensor arrangement method of a vehicle-mounted refrigerator refrigerant leakage early warning system, and relates to the technical field of early warning system design, and the method comprises the steps: analyzing an accident reason based on an accident tree analysis method, determining working condition information when a refrigerant leakage accident occurs, designing boundary conditions according to the working condition information, and setting a sensor arrangement mode; simulating the leakage diffusion of the refrigerant of the vehicle-mounted refrigerator by adopting a fluid mechanics calculation method to obtain the concentration field distribution of the refrigerant in the vehicle; then, the space in the vehicle is divided into different safety levels based on the distribution of the concentration field of the refrigerant in the vehicle and the combustion lower limit of the refrigerant of the vehicle-mounted refrigerator, a plurality of leakage monitoring areas with different safety levels are obtained, and finally, concentration monitoring sensors are installed in the leakage monitoring areas according to the different safety levels. And an alarm threshold value corresponding to the concentration monitoring sensor is set according to the safety level of the leakage monitoring area. The design reasonability of the position and the threshold value of the refrigerant concentration monitoring sensor can be effectively improved, and the condition can be timely and accurately monitored.

Description

Technical Field

[0001] The present application relates to the technical field of early warning system design, and particularly to a method for arranging sensors of a refrigerant leakage early warning system for a vehicle-mounted refrigerator. Background Art

[0002] As a flammable and explosive refrigerant, during the operation of a vehicle, due to factors such as vibration, there is a risk of leakage of R290 refrigerant in the vehicle-mounted refrigerator. In the narrow space of the vehicle, the leaked R290 refrigerant may accumulate and reach a flammable and explosive concentration, thus triggering a serious combustion and explosion accident when encountering a fire source. In view of this, ensuring the safe operation of the vehicle-mounted refrigerator is particularly important. For this reason, a safety early warning system for R290 refrigerant leakage must be installed, which is achieved by deploying multiple R290 gas concentration monitoring sensors. When the monitored R290 gas concentration reaches a preset dangerous threshold, the system will issue an alarm and trigger corresponding safety protection measures.

[0003] However, at present, there is still a lack of a unified safety early warning system layout method that comprehensively considers the leakage and diffusion law of R290 refrigerant and the optimal layout of R290 gas concentration monitoring sensors. Summary of the Invention

[0004] The purpose of the present application is to provide a method for arranging sensors of a refrigerant leakage early warning system for a vehicle-mounted refrigerator, which can effectively improve the design rationality of the positions and thresholds of refrigerant concentration monitoring sensors.

[0005] To achieve the above purpose, the present application provides a method for arranging sensors of a refrigerant leakage early warning system for a vehicle-mounted refrigerator, including the following steps: Analyze the causes of refrigerant leakage accidents in the vehicle-mounted refrigerator based on the fault tree analysis method, and determine the working condition information when a refrigerant leakage accident occurs.

[0006] Based on the boundary conditions designed according to the working condition information when an accident occurs, use the fluid mechanics calculation method to simulate and calculate the leakage and diffusion of the refrigerant in the vehicle-mounted refrigerator, and obtain the distribution of the refrigerant concentration field in the vehicle; the distribution of the refrigerant concentration field in the vehicle is used to characterize the volume fraction of the refrigerant in different regions of the vehicle.

[0007] Based on the distribution of the refrigerant concentration field in the vehicle and the lower flammability limit of the refrigerant in the vehicle-mounted refrigerator, divide the safety level of the vehicle space to obtain several leakage monitoring regions with different safety levels.

[0008] Install concentration monitoring sensors in each of the leakage monitoring regions, and set the alarm threshold of the corresponding concentration monitoring sensor according to the safety level of the leakage monitoring region.

[0009] Optionally, analyze the causes of refrigerant leakage accidents in vehicle-mounted refrigerators based on the fault tree analysis method, and determine the operating conditions information when refrigerant leakage accidents occur. The specific steps are as follows: Analyze the refrigerant leakage accident of the vehicle-mounted refrigerator based on the fault tree analysis method, and construct a fault tree model; the fault tree model includes top events, intermediate events, and basic events.

[0010] Based on the Boolean operation of the fault tree model, obtain the structural importance ranking and probability importance ranking of the basic events.

[0011] According to the structural importance ranking and probability importance ranking of the basic events, determine the main causes leading to the refrigerant leakage accident of the vehicle-mounted refrigerator and the operating conditions information when the refrigerant leakage accident occurs.

[0012] Optionally, the operating conditions information when a refrigerant leakage accident occurs includes: the size of the leakage port, the leakage location, and the leakage pressure.

[0013] Optionally, based on the boundary conditions designed according to the operating conditions information at the time of the accident, use the fluid mechanics calculation method to simulate and calculate the leakage and diffusion of the refrigerant in the vehicle-mounted refrigerator, and obtain the distribution of the refrigerant concentration field in the vehicle, specifically including: Establish an overall geometric model of the vehicle and the vehicle-mounted refrigerator, and perform grid modeling on the air circulation area in the vehicle to obtain the three-dimensional modeling result of the vehicle interior space.

[0014] Based on the boundary conditions designed according to the operating conditions information at the time of the accident, use the fluid mechanics calculation method in combination with the three-dimensional modeling result of the vehicle interior space to simulate and calculate the leakage and diffusion of the refrigerant in the vehicle-mounted refrigerator, and obtain the distribution of the refrigerant concentration field in the vehicle.

[0015] Optionally, simulate and calculate the leakage and diffusion of the refrigerant in the vehicle-mounted refrigerator through the following conservation equations: .

[0016] Among them, t is time, is the partial derivative with respect to time, β v is the volume fraction, ρ is the density, x i and x j are the spatial coordinate components, β j is the diffusion coefficient, u i and u j are the velocity components, is the mass term, V is the volume, pFor pressure, is the stress tensor, ρ 0 is the initial value of density, g i is the gravitational acceleration component, F i is the external force term, h is the specific enthalpy, μ eff is the effective viscosity, is the energy diffusion coefficient, is the pressure material derivative, is the heat source term.

[0017] Optionally, the conservation equations can be modified by using the k-ε turbulence model. The turbulent kinetic energy and dissipation rate transport equations of the k-ε turbulence model are shown as follows: .

[0018] in, k is the turbulent kinetic energy, ε is the dissipation rate, is the turbulent Prandtl number for the dissipation rate, P k is the turbulent kinetic energy generation term, P ε is the dissipation rate generation term, C 2 is the empirical constant of the dissipation rate equation.

[0019] The formula for calculating effective viscosity is shown below: .

[0020] in, μ is the dynamic viscosity coefficient, C μ is the empirical constant in the turbulent viscosity formula.

[0021] According to the specific embodiments provided in this application, this application discloses the following technical effects: The present application provides a method for arranging sensors of a refrigerant leakage warning system for a vehicle-mounted refrigerator. In this method, first, the accident causes are analyzed based on the fault tree analysis method to determine the operating conditions when a refrigerant leakage accident occurs. Accordingly, the boundary conditions are designed, and the leakage diffusion of the refrigerant in the vehicle-mounted refrigerator is simulated by using the fluid mechanics calculation method to obtain the distribution of the refrigerant concentration field in the vehicle. Subsequently, based on the distribution of the refrigerant concentration field in the vehicle and the lower flammability limit of the refrigerant in the vehicle-mounted refrigerator, the vehicle space is divided into different safety levels to obtain several leakage monitoring areas with different safety levels. Finally, concentration monitoring sensors can be installed in each leakage monitoring area according to this, and the alarm thresholds of the corresponding concentration monitoring sensors are set according to the safety levels of the leakage monitoring areas. In the above solution of the present application, by using the fluid mechanics calculation method, the distribution of the refrigerant can be quickly calculated, and the areas where the refrigerant is likely to accumulate during leakage can be inferred by dividing the safety levels. Furthermore, based on this calculation result, the installation positions and alarm thresholds of the monitoring sensors are designed. In this way, when the refrigerant leaks and begins to accumulate in these areas, this situation can be monitored in a timely and accurate manner, avoiding the failure of the installation position of the concentration monitoring sensor to monitor the rapid accumulation after the refrigerant leakage in a timely manner, thereby causing a serious combustion and explosion accident when encountering a fire source. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0023] Figure 1 It is a flowchart of a method for arranging sensors of a refrigerant leakage warning system for a vehicle-mounted refrigerator provided by an embodiment of the present application.

[0024] Figure 2 It is a flowchart of step S1 in a method for arranging sensors of a refrigerant leakage warning system for a vehicle-mounted refrigerator provided by an embodiment of the present application.

[0025] Figure 3 It is a flowchart of step S2 in a method for arranging sensors of a refrigerant leakage warning system for a vehicle-mounted refrigerator provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0027] To make the above objects, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] A method for arranging sensors of a refrigerant leakage warning system for a vehicle-mounted refrigerator provided by the present application. In an exemplary embodiment, as Figure 1 shown, it includes the following steps: S1. Analyze the causes of refrigerant leakage accidents in vehicle-mounted refrigerators based on the fault tree analysis method, and determine the working condition information when a refrigerant leakage accident occurs. In this embodiment, as Figure 2 shown, step S1 specifically includes the following steps: S11. Analyze the refrigerant leakage accident in the vehicle-mounted refrigerator based on the fault tree analysis method, and construct a fault tree model; the fault tree model includes top events, intermediate events, and basic events.

[0029] S12. Based on the Boolean operation of the fault tree model, obtain the structural importance ranking and probability importance ranking of the basic events.

[0030] S13. According to the structural importance ranking and probability importance ranking of the basic events, determine the main causes leading to the refrigerant leakage accident in the vehicle-mounted refrigerator and the working condition information when the refrigerant leakage accident occurs. Specifically, the working condition information when a refrigerant leakage accident occurs includes: the size of the leakage port, the leakage position, and the leakage pressure.

[0031] For the commonly used R290 refrigerant in vehicle-mounted refrigerators, in this embodiment, the fault tree analysis method is used to analyze the R290 refrigerant leakage accident in the vehicle-mounted refrigerator. Construct a fault tree model, and determine the top event, intermediate event, and basic event; among them, the top event is the R290 refrigerant leakage accident in the vehicle-mounted refrigerator. Through the Boolean operation based on the fault tree model, the structural importance ranking and probability importance ranking of the basic events can be obtained, and it can be determined which events are more likely to cause accidents, and then the main causes leading to the R290 leakage in the vehicle-mounted refrigerator (such as basic events such as valve leakage and pipeline leakage, which can guide the subsequent simulated working conditions), as well as the working condition information such as the size of the leakage port, the leakage position, and the leakage pressure.

[0032] S2. Based on the boundary conditions designed according to the working condition information at the time of the accident, the leakage and diffusion of the refrigerant in the in-vehicle refrigerator are simulated and calculated by using the fluid mechanics calculation method to obtain the distribution of the refrigerant concentration field in the vehicle; the distribution of the refrigerant concentration field in the vehicle is used to characterize the volume fraction of the refrigerant in different regions of the vehicle. In this embodiment, as Figure 3 shown, step S2 specifically includes the following steps: S21. Establish an overall geometric model of the vehicle and the in-vehicle refrigerator, and perform grid modeling on the air circulation area in the vehicle to obtain the three-dimensional modeling result of the vehicle interior space. In the vehicle, the air circulation area in the vehicle is a fluid domain, and the leaked R290 refrigerant gas can diffuse and accumulate in the fluid domain. Perform three-dimensional grid division on the air circulation area. The grids are all regular hexahedrons. Through grid sensitivity verification, set the number of grids in the X, Y, and Z directions to determine the overall number of grids, and use a small number of grids while ensuring the accuracy of the results.

[0033] S22. Based on the boundary conditions designed according to the working condition information at the time of the accident, use the fluid mechanics calculation method combined with the three-dimensional modeling result of the vehicle interior space to simulate and calculate the leakage and diffusion of the refrigerant in the in-vehicle refrigerator to obtain the distribution of the refrigerant concentration field in the vehicle. The boundary conditions are set based on the above-mentioned working condition information, aiming to make the simulation results conform to the actual situation, because the physical properties of the fluid are affected by the environment and will also affect its leakage and diffusion. The boundary conditions for the simulation calculation include environmental pressure, environmental temperature, leakage port size, leakage gas pressure, etc.

[0034] Specifically in this embodiment, the leakage and diffusion of the refrigerant in the in-vehicle refrigerator are simulated and calculated through the following conservation equations: .

[0035] The above three equations are the mass conservation equation, the momentum conservation equation, and the energy conservation equation respectively. In the equations, t is time, is the partial derivative with respect to time, β v is the volume fraction, ρ is the density, x i and x j are the spatial coordinate components, β j is the diffusion coefficient, u i and u j are the velocity components, is the mass term, V is the volume, p is the pressure, is the stress tensor, ρ 0 is the initial value of the density, gi is the gravitational acceleration component, F i is the external force term, h is the specific enthalpy, μ eff is the effective viscosity, is the energy diffusion coefficient, is the pressure material derivative, is the heat source term.

[0036] By using the k-ε turbulence model to modify the conservation equations, the turbulent kinetic energy and dissipation rate transport equations of the k-ε turbulence model are shown as follows: .

[0037] in, k is the turbulent kinetic energy, ε is the dissipation rate, is the turbulent Prandtl number for the dissipation rate, P k is the turbulent kinetic energy generation term, P ε is the dissipation rate generation term, C 2 is the empirical constant of the dissipation rate equation.

[0038] The formula for calculating effective viscosity is shown below: .

[0039] in, μ is the dynamic viscosity coefficient, C μ is the empirical constant in the turbulent viscosity formula.

[0040] In some embodiments, the effective viscosity can also be calculated using the following formula: .

[0041] in, ε’ is the corrected dissipation rate.

[0042] S3. Based on the refrigerant concentration field distribution in the vehicle and the lower flammability limit of the refrigerant in the vehicle refrigerator, the safety level of the vehicle interior space is divided to obtain several leakage monitoring areas with different safety levels. Specifically, the lower flammability limit volume fraction of R290 refrigerant is 2.1%. In this embodiment, the safety level of the area is divided according to the three concentration values of 2.1% (1), 1.05% (1 / 2) and 0.525% (1 / 4). Among them, the area with a volume fraction greater than or equal to 2.1% is a flammable area, which can also be called a high-risk area, the area with a volume fraction between 0.525% and 1.05% is a low-risk area, and the area with a volume fraction between 1.05% and 2.1% is a medium-risk area.

[0043] S4. Install concentration monitoring sensors in each leakage monitoring area respectively, and set the alarm thresholds of the corresponding concentration monitoring sensors according to the safety levels of the leakage monitoring areas. After dividing the safety levels of each area in the previous step, install R290 gas concentration monitoring sensors according to the central positions of the areas with different safety levels, and set the corresponding thresholds to 2.1% (1), 1.05% (1 / 2), and 0.525% (1 / 4); thus, when the R290 concentration at the corresponding concentration monitoring sensor reaches the threshold, the concentration monitoring sensor can issue an alarm and trigger different safety protection measures.

[0044] By using the sensor layout method of the refrigerant leakage warning system for vehicle-mounted refrigerators provided in the above embodiments of the present application, after designing the concentration monitoring sensors of the refrigerant leakage warning system for vehicle-mounted refrigerators, the efficiency of the warning system in issuing alarms is higher, because when installing the concentration monitoring sensors in step S4, the possible dangerous areas are pre-calculated, reducing the time for the R290 refrigerant to reach the gas detector from the leakage point; and the hydrodynamic calculation method used in step S2 can quickly calculate the R290 dangerous areas, saving time, cost, and having high accuracy compared with on-site experiments or other methods. In addition, the fault tree analysis method used in step S1 provides effective information for the boundary condition design in step S2, which can ensure the accuracy of the simulation calculation.

[0045] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0046] In this article, specific examples are used to elaborate on the principles and implementation manners of the present application. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A method for arranging sensors of a refrigerant leakage warning system for a vehicle-mounted refrigerator, characterized in that Including: Analyze the causes of refrigerant leakage accidents in vehicle-mounted refrigerators based on the fault tree analysis method to determine the operating conditions information when refrigerant leakage accidents occur; Based on the boundary conditions designed according to the operating conditions information at the time of the accident, use the fluid mechanics calculation method to simulate and calculate the leakage and diffusion of the refrigerant in the vehicle-mounted refrigerator to obtain the distribution of the refrigerant concentration field in the vehicle; The refrigerant concentration field distribution in the vehicle is used to characterize the volume fraction of the refrigerant in different regions of the vehicle; Based on the refrigerant concentration field distribution in the vehicle and the lower flammability limit of the refrigerant in the vehicle-mounted refrigerator, divide the safety level of the vehicle space to obtain several leakage monitoring areas with different safety levels; Install concentration monitoring sensors in each of the leakage monitoring areas, and set the alarm threshold of the corresponding concentration monitoring sensors according to the safety level of the leakage monitoring area.

2. The method for arranging sensors of the refrigerant leakage warning system of the in-vehicle refrigerator according to claim 1, characterized in that, Analyze the causes of refrigerant leakage accidents in vehicle-mounted refrigerators based on the fault tree analysis method to determine the operating conditions information when refrigerant leakage accidents occur, specifically including: Analyze the refrigerant leakage accident of the vehicle-mounted refrigerator based on the fault tree analysis method to construct a fault tree model; the fault tree model includes top events, intermediate events and basic events; Based on the Boolean operation of the fault tree model, obtain the structural importance ranking and probability importance ranking of the basic events; According to the structural importance ranking and probability importance ranking of the basic events, determine the main causes of the refrigerant leakage accident in the vehicle-mounted refrigerator and the operating conditions information when the refrigerant leakage accident occurs.

3. The method for arranging sensors of the refrigerant leakage warning system of the vehicle-mounted refrigerator according to claim 1, characterized in that The operating conditions information when the refrigerant leakage accident occurs includes: the size of the leakage port, the leakage position, and the leakage pressure.

4. The method for arranging sensors of the refrigerant leakage warning system of the vehicle-mounted refrigerator according to claim 1, wherein, Based on the boundary conditions designed according to the operating conditions information at the time of the accident, use the fluid mechanics calculation method to simulate and calculate the leakage and diffusion of the refrigerant in the vehicle-mounted refrigerator to obtain the distribution of the refrigerant concentration field in the vehicle, specifically including: Establish an overall geometric model of the vehicle and the vehicle-mounted refrigerator, and perform grid modeling on the air circulation area in the vehicle to obtain the three-dimensional modeling result of the vehicle space; Based on the boundary conditions designed according to the operating conditions information at the time of the accident, use the fluid mechanics calculation method combined with the three-dimensional modeling result of the vehicle space to simulate and calculate the leakage and diffusion of the refrigerant in the vehicle-mounted refrigerator to obtain the distribution of the refrigerant concentration field in the vehicle.

5. The method for arranging sensors of the refrigerant leakage warning system of the in-vehicle refrigerator according to claim 4, characterized in that, Simulate and calculate the leakage and diffusion of the refrigerant in the vehicle-mounted refrigerator through the following conservation equations: ； wherein, t is time, is the partial derivative with respect to time, β v is the volume fraction, ρ is the density, x i and x j are the spatial coordinate components, β j is the diffusion coefficient, u i and u j are the velocity components, is the mass term, V is the volume, p is the pressure, is the stress tensor, ρ 0 is the initial value of density, g i are the components of gravitational acceleration, F i is the external force term, h is the specific enthalpy, μ eff is the effective viscosity, is the energy diffusion coefficient, is the material derivative of pressure, is the heat source term.

6. The method for arranging sensors of the refrigerant leakage warning system of the vehicle-mounted refrigerator according to claim 5, characterized in that, Modify the conservation equation by using the k-ε turbulence model. The turbulent kinetic energy and dissipation rate transport equations of the k-ε turbulence model are shown as follows: ； Among them, k is the turbulent kinetic energy, ε is the dissipation rate, is the turbulent Prandtl number of the dissipation rate, P k is the turbulent kinetic energy generation term, P ε is the dissipation rate generation term, C 2 is the empirical constant of the dissipation rate equation; The calculation formula of the effective viscosity is shown as follows: ； wherein, μ is the dynamic viscosity coefficient, C μ is the empirical constant in the turbulence viscosity formula.

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