Nitrogen oxide sensor double-cavity test system

Abstract

A double-cavity test system for a nitrogen oxide sensor relates to the technical field of nitrogen oxide sensors and comprises a tubular furnace, a quartz tube, an aluminum oxide tube, an exhaust port, a platinum wire, a gas supply device, an exhaust pipe and other core components. The tubular furnace provides a high-temperature environment of 350-850 DEG C, the quartz tube is inserted into the tubular furnace, one end of the quartz tube is a test end, and the other end of the quartz tube is a gas inlet end; the alumina tube is inserted into the quartz tube, is used for placing a to-be-tested sensor and is hermetically connected with the orifice of the quartz tube through a sealing ring; the platinum wire is used for conductively leading out terminals of a reference electrode and a sensitive electrode of the sensor; the gas supply device comprises a buffer tank, a gas inlet pipeline, a valve body, a Venturi tube, a turbulent flow tube and a turbulent flow net, and is used for supplying test gas to the reference electrode and the sensitive electrode respectively and uniformly mixing and scattering the gas through the turbulent flow device; according to the invention, a stable and uniform test gas environment is provided for the sensor, and the accuracy and repeatability of a test result are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of nitrogen oxide sensors, and more particularly to a dual-chamber test system for nitrogen oxide sensors. Background Art

[0002] With the development of the automotive industry and the increase in the number of motor vehicles, motor vehicle exhaust emissions have become the main source of air pollution. Automobile exhaust pollution has accounted for 65% - 80% of all air pollution. The main harmful components in the exhaust are: carbon monoxide, unburned hydrocarbons, nitrogen oxides, and particulate matter, etc. The emissions of these exhaust pollutants have posed a serious threat to human health and the living environment. In response to this situation, many countries have formulated increasingly strict automobile exhaust emission regulations to restrict this problem in order to control the emissions of automobile exhaust pollutants. In order to achieve the goal of reducing exhaust emissions, it is necessary to monitor and control the exhaust in real time. Oxygen sensors, nitrogen oxide sensors, and ammonia sensors for automobile exhaust have become key monitoring components of the automobile exhaust control system.

[0003] The quality of nitrogen oxide sensors directly determines the accuracy of measuring the content of nitrogen oxides in the exhaust. Moreover, in recent years, the development of domestic nitrogen oxide sensors has not been mature enough, and most of them are in the research and experimental stage. There is a lack of effective methods for detecting nitrogen oxide sensors. The traditional method for testing the electrode performance of NOx sensors is to connect the signal end to the NOx sensor at room temperature, but this method is easily affected by the external climate and is inconsistent with the actual application environment, thus affecting the research and quality control of NOx sensors. For this reason, in the prior art, the sensor to be evaluated is placed in a constant temperature and humidity chamber and the electrode performance of the NOx sensor is tested using a multimeter, but the measurement stability is poor and the test efficiency is relatively low, which is not suitable for large-scale use. Therefore, those skilled in the art urgently need to develop a test system that can stably test nitrogen oxide sensors. Summary of the Invention

[0004] In order to overcome the deficiencies in the background art, the present invention discloses a dual-chamber test system for nitrogen oxide sensors.

[0005] To achieve the above-mentioned invention purpose, the present invention adopts the following technical solutions:

[0006] A dual-chamber test system for nitrogen oxide sensors, comprising:

[0007] A tube furnace for providing a temperature measurement environment of 350°C to 850°C;

[0008] A quartz tube inserted into the cavity of the tube furnace, and one end of the quartz tube is a test end and the other end is an air inlet end;

[0009] An exhaust port, which is correspondingly communicated with the part where the quartz tube extends out of the tube body of the tube furnace;

[0010] An alumina tube, one end of which is inserted into the quartz tube, and there is a sealed connection between the outer wall of the extending end of the alumina tube and the inner wall of the tube orifice of the quartz tube; one end of the alumina tube located inside the quartz tube is provided with a nitrogen oxide sensor to be measured, and the nitrogen oxide sensor to be measured can hermetically seal one end of the alumina tube located inside the quartz tube. The reference electrode of the nitrogen oxide sensor to be measured is located inside the alumina tube, and the sensitive electrode of the nitrogen oxide sensor to be measured is exposed inside the quartz tube;

[0011] Platinum wires, there are two platinum wires, which are respectively used for conducting and leading out the wiring ends of the reference electrode and the sensitive electrode of the nitrogen oxide sensor to be measured;

[0012] Gas supply devices, there are two gas supply devices, which are respectively installed at the intake end of the quartz tube and the extending end of the alumina tube; used for supplying test gases to the reference electrode and the sensitive electrode respectively;

[0013] An exhaust pipe, which is installed at the extending end of the alumina tube.

[0014] Preferably, the gas supply device includes:

[0015] A buffer tank, used for buffering the test gas;

[0016] Intake pipelines, multiple intake pipelines are correspondingly communicated with the buffer tank;

[0017] A first valve body, installed on the intake pipeline;

[0018] A flow disturbance device, which is correspondingly communicated with the air outlet of the buffer tank;

[0019] A second valve body, installed between the buffer tank and the flow disturbance device;

[0020] The flow disturbance device includes:

[0021] Venturi tubes, multiple Venturi tubes are connected in series;

[0022] A flow disturbance tube, installed between two adjacent Venturi tubes;

[0023] A flow disturbance net, filled in the flow disturbance tube, and the flow disturbance net is formed by curling multiple filaments into a disordered mass, used for dispersing the test gas and playing a role in blocking the flow.

[0024] Preferably, a spiral blade is arranged in the reduced-diameter section of the Venturi tube.

[0025] Preferably, a connecting flange is arranged at the air outlet end of the flow disturbance device.

[0026] Preferably, a sealing ring is arranged between the alumina tube and the inner wall of the tube orifice of the quartz tube.

[0027] Preferably, the sealing ring is a flexible graphite sealing ring, and a corrugated elastic metal support ring is embedded inside the flexible graphite sealing ring.

[0028] Preferably, a thermocouple for temperature measurement is provided inside the quartz tube.

[0029] Preferably, the nitrogen oxide sensor to be measured is bonded to the nozzle of the alumina tube through a ceramic adhesive that can withstand heat above 1000 °C.

[0030] Preferably, a necking part is provided at the air inlet end of the quartz tube.

[0031] Preferably, a partition for separating the inlet air and the outlet air is provided inside the alumina tube; one-way valves are installed at both the exhaust port and the outlet end of the exhaust pipe.

[0032] Due to the adoption of the above-mentioned technical solutions, the present invention has the following beneficial effects:

[0033] (1) The structure of the present invention is simple. Through the multi-stage mixing design of the venturi tube, the turbulence tube and the turbulence net in the air supply device, the precise control of the test gas concentration can be achieved, and the concentration uniformity reaches within ±0.5%. This high-precision gas mixing ability ensures the accurate and reliable test results of the sensor in different concentration NO X environments.

[0034] (2) Further, through the combination of the flexible graphite sealing ring and the elastic metal support ring and the precise gas mixing control in the present invention, the long-term stable test performance can be maintained in a high-temperature environment. The heat resistance performance of the sealing ring and the adaptable design of the elastic metal support ring ensure that in a high-temperature environment above 850 °C, the system can operate continuously without leakage, thus providing a reliable platform for the long-term stability test of the nitrogen oxide sensor.

[0035] (3) Through the collaborative design of multiple components such as the tube furnace, the quartz tube, the air supply device, and the sealing structure in the present invention, the whole process from gas configuration, mixing, transportation, testing to exhaust can operate efficiently, significantly improving the efficiency and accuracy of the nitrogen oxide sensor test BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a schematic structural diagram of the present invention;

[0037] Figure 2 is a schematic structural diagram of the air supply device;

[0038] Figure 3 is a schematic structural diagram of the sealing ring.

[0039] In the figure: 1. Tube furnace; 2. Quartz tube; 3. Exhaust port; 4. Alumina tube; 5. Platinum wire; 6. Gas supply device; 6-1. Buffer tank; 6-2. Inlet pipeline; 6-3. First valve body; 6-4. Second valve body; 6-5. Venturi tube; 6-6. Spiral blade; 6-7. Turbulence tube; 6-8. Turbulence net; 6-9. Connecting flange; 7. Exhaust pipe; 8. Sealing ring; 9. Thermocouple; 10. Partition board; 11. Check valve. Detailed implementation mode

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "upper" and "lower" is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product of the present invention is usually placed. It is 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 should not be construed as a limitation of the present invention.

[0042] In this application, unless otherwise clearly specified and limited, terms such as "installation", "connection", "connection", "fixation" and other terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be directly connected, or indirectly connected through an intermediate medium, and can be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific situations.

[0043] Embodiment 1:

[0044] Combined with the attached Figures 1 to 3 , a double-chamber test system for a nitrogen oxide sensor includes a tube furnace 1, a quartz tube 2, an exhaust port 3, an alumina tube 4 and a gas supply device 6. Among them, the tube furnace 1 is the core heating component of the system and can provide a stable temperature environment of 350°C to 850°C to simulate the high-temperature operating conditions of the nitrogen oxide sensor in actual working conditions. The quartz tube 2 is inserted into the cavity of the tube furnace 1. One end of the quartz tube 2 is the test end, and the other end is the intake end. The material of the quartz tube 2 is selected as high-purity quartz glass because it has excellent high-temperature resistance and chemical stability and can withstand gas corrosion in a long-term high-temperature environment.

[0045] The intake end of the quartz tube 2 is provided with a necking part as shown in the attachedFigure 1 As shown, this design enables the test gas to be blown towards the sensitive electrode in a directional manner, thereby improving the test efficiency and reducing the interference of gas diffusion on the test results. The other end of the quartz tube 2, the test end, is connected to the external environment through the exhaust port 3 for discharging the excess test gas. A one-way valve 11 is installed at the gas outlet end of the exhaust port 3 to prevent external air from flowing back into the quartz tube 2 and avoid affecting the test accuracy due to changes in oxygen concentration.

[0046] The alumina tube 4 serves as the isolation cavity for the reference electrode. One end of it is inserted into the quartz tube 2, and the other end extends out of the quartz tube 2 and is connected to the gas supply device 6. The material of the alumina tube 4 is selected as high-purity alumina ceramic, because it has good high-temperature resistance and chemical stability, and can effectively isolate the gas environments where the reference electrode and the sensitive electrode are located.

[0047] A sealing connection is achieved between the outer wall of the extended end of the alumina tube 4 and the inner wall of the orifice of the quartz tube 2 through the sealing ring 8. The sealing ring 8 is made of flexible graphite material and is embedded with a corrugated elastic metal support ring to adapt to the deformation of the alumina tube 4 and the quartz tube 2 due to thermal expansion and contraction in a high-temperature environment. The flexible graphite sealing ring has the performance of withstanding heat above 1000°C. At the same time, its flexible characteristics can effectively buffer the thermal stress and ensure the long-term stability of the sealing performance. The design of the elastic metal support ring further enhances the mechanical strength of the sealing ring 8, enabling it to still maintain a tight fit with the alumina tube 4 and the quartz tube 2 in a high-temperature environment.

[0048] The nitrogen oxide sensor to be tested is installed at one end of the alumina tube 4 located inside the quartz tube 2 and is fixed and sealed with a ceramic adhesive that can withstand heat above 1000°C. The ceramic adhesive can not only withstand the high-temperature environment but also effectively isolate the gas environments where the reference electrode and the sensitive electrode are located, ensuring that the two are in different test gas environments respectively.

[0049] The reference electrode of the nitrogen oxide sensor is located inside the alumina tube 4, and a reference gas with a known concentration is introduced into the alumina tube 4 through the gas supply device 6 to establish a stable reference potential. The sensitive electrode is exposed inside the quartz tube 2 and directly contacts the test gas environment. The connection terminals of the sensitive electrode and the reference electrode are respectively led out through platinum wires 5. The platinum wires 5 are made of high-purity platinum metal, because it has excellent high-temperature resistance and conductivity, and can ensure the stability and accuracy of signal transmission.

[0050] The function of the gas supply device 6 is to accurately configure NO X test gases with different concentrations and achieve uniform mixing of the gases through the turbulence device. The gas supply device 6 mainly includes a buffer tank 6-1, an inlet pipeline 6-2, a flowmeter, a first valve body 6-3, a second valve body 6-4, a Venturi tube 6-5, a turbulence tube 6-7, and a turbulence mesh 6-8.

[0051] The buffer tank 6-1 is connected to the nitrogen storage tank, oxygen storage tank, nitric oxide storage tank and nitrogen dioxide storage tank respectively through a plurality of inlet pipelines 6-2. A first valve body 6-3 and a flowmeter are installed on each inlet pipeline 6-2. By precisely controlling the opening degree of the flowmeter, quantitative regulation of the flow rates of different gases can be achieved.

[0052] After the gas enters the buffer tank 6-1, it enters the flow disturbance device through the second valve body 6-4. The flow disturbance device is composed of a plurality of serially connected Venturi tubes 6-5. A spiral blade 6-6 is arranged in the reduced-diameter section of the Venturi tube 6-5. The gas flow rate is accelerated through the Bernoulli effect, enabling the gas to achieve preliminary mixing during the high-speed flow process. A flow disturbance tube 6-7 is installed between adjacent Venturi tubes 6-5, and a multi-layer flow disturbance net 6-8 is filled in the flow disturbance tube 6-7. The flow disturbance net 6-8 is formed by randomly curling stainless steel wires into a ball. Its irregular structure can effectively disperse the gas flow, further enhance the mixing effect, and play a role in blocking the flow. After multi-stage flow disturbance, the concentration uniformity of the test gas can reach within ±0.5%, thus ensuring the accuracy of the test results.

[0053] A connection flange 6-9 is provided at the gas outlet end of the flow disturbance device, facilitating quick connection with the inlet end of the quartz tube 2 or the extended end of the alumina tube 4. The connection flange 6-9 is made of a high-temperature-resistant metal material and is equipped with an O-ring seal to ensure the airtightness of the connection part.

[0054] Furthermore, a thermocouple 9 is arranged inside the quartz tube 2 for real-time monitoring of the internal environment temperature of the tube. The thermocouple 9 is a K-type thermocouple, and its temperature measurement range covers -200°C to 1370°C, which can meet the accurate temperature measurement requirements of the system in the temperature range of 350°C to 850°C. The signal of the thermocouple 9 is led out through a shielded cable and connected to a temperature controller to achieve closed-loop regulation of the heating power of the tube furnace 1. The temperature controller adopts a PID algorithm and can control the temperature fluctuation within ±1°C, thereby providing a stable high-temperature environment for the test.

[0055] Furthermore, a partition 10 is arranged inside the alumina tube 4, dividing the tube cavity into an inlet part and an outlet part. The reference gas enters the inlet part of the alumina tube 4 through the gas supply device 6, directly blows towards the reference electrode, and then enters the exhaust pipe 7 along the outlet part and is discharged. A one-way valve 11 is also installed at the gas outlet end of the exhaust pipe 7 to prevent external air from flowing back and ensure the stability of the gas composition in the environment where the reference electrode is located.

[0056] The test gas in the quartz tube 2 is discharged through the exhaust port 3. The exhaust port 3 is connected to an external exhaust system and is equipped with a flow regulating valve for controlling the exhaust speed to avoid the formation of negative pressure inside the quartz tube 2 due to too fast exhaust.

[0057] The parts not detailed in the present invention are prior arts. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive, aiming to encompass all changes falling within the meaning and scope of the equivalent elements in the present invention.

Claims

1. A dual-chamber test system for a nitrogen oxide sensor, characterized in that, Comprising: A tube furnace (1) for providing a temperature measurement environment of 350°C to 850°C; A quartz tube (2) inserted into the cavity of the tube furnace (1), with one end of the quartz tube (2) being the test end and the other end being the air inlet end; An exhaust port (3) corresponding to and communicating with the part of the quartz tube (2) extending out of the body of the tube furnace (1); An alumina tube (4) with one end inserted into the quartz tube (2), and there is a sealed connection between the outer wall of the extending end of the alumina tube (4) and the inner wall of the orifice of the quartz tube (2); One end of the alumina tube (4) located inside the quartz tube (2) houses the nitrogen oxide sensor to be tested, and the nitrogen oxide sensor to be tested can seal the end of the alumina tube (4) located inside the quartz tube (2). The reference electrode of the nitrogen oxide sensor to be tested is located inside the alumina tube (4), and the sensitive electrode of the nitrogen oxide sensor to be tested is exposed inside the quartz tube (2); Platinum wires (5), there are two platinum wires (5), respectively used for conducting and leading out the connection terminals of the reference electrode and the sensitive electrode of the nitrogen oxide sensor to be tested; Gas supply devices (6), there are two gas supply devices (6), respectively installed at the air inlet end of the quartz tube (2) and the extending end of the alumina tube (4); Used to supply test gases to the reference electrode and the sensitive electrode respectively; An exhaust pipe (7) installed at the extending end of the alumina tube (4).

2. The dual-chamber test system for nitrogen oxide sensors according to claim 1, characterized in that, The gas supply device (6) includes: A buffer tank (6-1) for buffering the test gas; Inlet pipelines (6-2), multiple inlet pipelines (6-2) corresponding to and communicating with the buffer tank (6-1); A first valve body (6-3) installed on the inlet pipeline (6-2); A flow disturbance device corresponding to and communicating with the air outlet of the buffer tank (6-1); A second valve body (6-4) installed between the buffer tank (6-1) and the flow disturbance device; The flow disturbance device includes: Venturi tubes (6-5), multiple Venturi tubes (6-5) are connected in series; A flow disturbance tube (6-7) installed between two adjacent Venturi tubes (6-5); A flow disturbance net (6-8) filled inside the flow disturbance tube (6-7), the flow disturbance net (6-8) is formed by randomly curling multiple filaments into clusters, used to disperse the test gas and play a role in blocking the flow.

3. The nitrogen oxide sensor double-chamber test system according to claim 2, characterized in that: A spiral blade (6-6) is provided inside the reduced-diameter section of the Venturi tube (6-5).

4. The nitrogen oxide sensor double-chamber test system according to claim 1, characterized in that: A connecting flange (6-9) is provided at the air outlet end of the flow disturbance device.

5. The nitrogen oxide sensor double-chamber test system according to claim 1, characterized in that: A sealing ring (8) is provided between the alumina tube (4) and the inner wall of the orifice of the quartz tube (2).

6. The nitrogen oxide sensor double-chamber test system according to claim 5, characterized in that: The sealing ring (8) is a flexible graphite sealing ring, and a wavy elastic metal support ring is embedded inside the flexible graphite sealing ring.

7. The nitrogen oxide sensor double-chamber test system according to claim 1, characterized in that: A thermocouple (9) for temperature measurement is provided inside the quartz tube (2).

8. The dual-chamber test system for a nitrogen oxide sensor according to claim 1, characterized in that: The nitrogen oxide sensor to be tested is bonded to the nozzle of the alumina tube (4) through a ceramic adhesive that can withstand heat above 1000 °C.

9. The dual-chamber test system for a nitrogen oxide sensor according to claim 1, characterized in that: The intake end of the quartz tube (2) is provided with a necking portion.

10. The dual-chamber test system for a nitrogen oxide sensor according to claim 1, characterized in that: A partition (10) for separating the intake air and the exhaust air is provided inside the alumina tube (4); check valves (11) are installed at the exhaust port (3) and the outlet end of the exhaust pipe (7).

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