A device and method for detecting nitrogen concentration in the hydrogen circuit of a fuel cell engine

Abstract

This invention relates to the field of hydrogen fuel cells, specifically to a device and method for detecting nitrogen concentration in the hydrogen circuit of a fuel cell engine. It includes a U-shaped tube and two pressure sensors respectively disposed at both ends of the U-shaped tube. Based on the detection results of the two pressure sensors, a nitrogen venting valve is opened and closed to control the flow resistance of the U-shaped tube within a set range, thereby indirectly controlling the nitrogen concentration in the pipeline. This invention is small in size, simple to implement, and inexpensive.

Description

Technical Field

[0001] This invention relates to the field of hydrogen fuel cells, and in particular to a device and method for detecting nitrogen concentration in the hydrogen path of a fuel cell engine. Background Technology

[0002] Hydrogen fuel cell engines consist of stack modules, hydrogen systems, air systems, and control systems. During engine operation, nitrogen gas on the cathode side gradually permeates to the anode side and mixes with the hydrogen gas, causing the hydrogen concentration to gradually decrease. This leads to a drop in the voltage of a single cell and a reduction in overall efficiency. In severe cases, the stack may operate without hydrogen, causing irreversible damage to its lifespan. Therefore, it is necessary to monitor the nitrogen concentration in the circulating hydrogen of the stack and use a nitrogen venting valve to remove circulating hydrogen with a nitrogen concentration exceeding the allowable range in a timely manner to ensure the quality of the reactant gas on the anode side of the stack.

[0003] Existing methods mostly involve using an external hydrogen composition detection device to directly detect the hydrogen composition, and then calibrating the opening time and interval of the nitrogen venting valve. However, hydrogen composition detection devices are expensive, bulky, and complicated to operate. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the background technology by proposing a small, simple, and low-cost device and method for detecting nitrogen concentration in the hydrogen circuit of a fuel cell engine.

[0005] On one hand, the present invention proposes a nitrogen concentration detection device for hydrogen circuit of fuel cell engine, including a U-shaped tube and two pressure sensors respectively disposed at both ends of the U-shaped tube.

[0006] Preferably, the cross-section of the U-shaped tube is circular.

[0007] On the other hand, the present invention proposes a method for detecting nitrogen concentration in the hydrogen path of a fuel cell engine, which is implemented using the aforementioned fuel cell engine hydrogen path nitrogen concentration detection device. The detection method includes the following steps:

[0008] S1. High-speed hydrogen mixed with nitrogen and water vapor is introduced into the U-shaped tube. As the density of nitrogen, water vapor and hydrogen decreases in sequence, under the action of centrifugal force, nitrogen, water vapor and hydrogen gradually stratify from the outside to the inside of the U-shaped tube. Nitrogen is compressed to the outermost layer. The flow resistance of the U-shaped tube is mainly reflected in the flow resistance of nitrogen.

[0009] S2. Detect the pressure at both ends of the U-tube using a pressure sensor;

[0010] S3. Based on the results detected by the two pressure sensors, the nitrogen venting valve is opened and closed to control the flow resistance of the U-tube within the set range, thereby indirectly controlling the nitrogen concentration in the pipeline.

[0011] Preferably, the U-shaped tube has a diameter of 25 mm, a length of 130 mm, a flow rate of 1500 L / min, and a back pressure of 250 kPaA.

[0012] Preferably, if the U-tube contains pure hydrogen gas, the flow resistance is 160 Pa;

[0013] If the gas is wet hydrogen with 100% humidity, the flow resistance is 430 Pa.

[0014] If the humidity is 100% and the nitrogen / hydrogen volume ratio is 0.15, then the flow resistance is 570 Pa;

[0015] If the humidity is 100% and the nitrogen / hydrogen volume ratio is 0.3, then the flow resistance is 914 Pa;

[0016] By controlling the opening and closing of the nitrogen venting valve to keep the flow resistance of the U-tube below 570 Pa, the nitrogen concentration in the pipeline can be controlled to be below 15%.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects:

[0018] This invention, while meeting nitrogen removal requirements, takes a different approach. It utilizes the significant difference in density and flow resistance between water vapor and nitrogen mixed in hydrogen gas and hydrogen gas, which is much greater than that of hydrogen gas itself, to design a tooling for gas separation. This avoids the more difficult hydrogen composition detection scheme and indirectly reflects changes in gas composition within the pipeline by designing a small, simple, and low-cost tooling, thus solving practical engineering problems. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the U-shaped tube structure according to an embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of the local gas distribution inside the U-shaped tube. Detailed Implementation

[0021] like Figure 1 and Figure 2 As shown in this embodiment, a nitrogen concentration detection device for the hydrogen path of a fuel cell engine includes a U-shaped tube and two pressure sensors respectively disposed at both ends of the U-shaped tube. The U-shaped tube has a circular cross-section to allow for smooth gas flow. The U-shaped tube has a diameter of 25 mm, a length of 130 mm, a flow rate of 1500 L / min, and a back pressure of 250 kPaA, where kPaA is a unit of absolute pressure.

[0022] The detection method of the above-mentioned fuel cell engine hydrogen circuit nitrogen concentration detection device includes the following steps:

[0023] S1. High-speed hydrogen gas mixed with nitrogen and water vapor is passed into a U-shaped tube. Since the density of nitrogen, water vapor, and hydrogen decreases in that order, ... Figure 2As shown, under the action of centrifugal force, nitrogen, water vapor and hydrogen gradually stratify from the outside to the inside of the U-shaped tube. Nitrogen is compressed to the outermost layer and fully contacts the tube wall. The flow resistance of the U-shaped tube is mainly reflected in the flow resistance of nitrogen. As the nitrogen concentration in the gas gradually increases, the flow resistance of the U-shaped tube is significantly higher than that of the straight tube.

[0024] S2. Detect the pressure at both ends of the U-tube using a pressure sensor;

[0025] S3. Based on the results detected by the two pressure sensors, the nitrogen venting valve is opened and closed to control the flow resistance of the U-tube within the set range, thereby indirectly controlling the nitrogen concentration in the pipeline.

[0026] The flow resistance data under different conditions were obtained based on the gas composition and humidity inside the U-tube:

[0027] ①If the U-tube contains pure hydrogen, the flow resistance is 160 Pa;

[0028] ②If the gas is wet hydrogen with 100% humidity, the flow resistance is 430 Pa;

[0029] ③ If the humidity is 100% and the nitrogen / hydrogen volume ratio is 0.15, then the flow resistance is 570 Pa;

[0030] ④ If the humidity is 100% and the nitrogen / hydrogen volume ratio is 0.3, then the flow resistance is 914 Pa;

[0031] By controlling the opening and closing of the nitrogen venting valve to keep the flow resistance of the U-tube below 570Pa, the nitrogen concentration in the pipeline can be controlled below 15%, ensuring the normal operation of the fuel cell engine.

[0032] This invention, while meeting nitrogen removal requirements, takes a different approach. It leverages the significant difference in density and flow resistance between water vapor and nitrogen mixed in hydrogen gas and hydrogen gas itself. A fixture is designed to separate the gases, ensuring sufficient contact between water vapor / nitrogen and the pipe wall to increase flow resistance. This allows hydrogen gas to escape from the pipe wall as much as possible. Given the already significant difference in properties between hydrogen and water vapor / nitrogen, the impact of water vapor / nitrogen on pipeline flow resistance is amplified. Changes in pipeline flow resistance indirectly reflect changes in the gas composition of the hydrogen gas path. This invention avoids the difficult implementation of conventional hydrogen composition detection methods, instead using a small, simple, and low-cost flow resistance detection fixture to indirectly reflect changes in the gas composition within the pipeline, thus solving a practical engineering problem.

[0033] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A method for detecting a nitrogen concentration in a hydrogen passage of a fuel cell engine, characterized by comprising: a step of detecting a nitrogen concentration in a hydrogen passage of a fuel cell engine by using a hydrogen passage nitrogen concentration detecting device according to any one of claims 1 to 8. The fuel cell engine hydrogen path nitrogen concentration detection device comprises: A U-shaped tube, the cross section of the U-shaped tube is circular; A pressure sensor is arranged at each end of the U-shaped tube; The detection method comprises the following steps: S1, high-speed hydrogen gas mixed with nitrogen and water vapor is introduced into the U-shaped tube, because the densities of nitrogen, water vapor and hydrogen gas decrease in turn, under the action of centrifugal force, nitrogen, water vapor and hydrogen gas are gradually layered from the outside to the inside in the U-shaped tube, nitrogen is compressed in the outermost layer, and the flow resistance of the U-shaped tube is the flow resistance of nitrogen; S2, the pressures at both ends of the U-shaped tube are detected by the pressure sensors; S3, the nitrogen discharge valve is opened and closed according to the detection results of the two pressure sensors, the flow resistance of the U-shaped tube is controlled within a set range, and the nitrogen concentration in the pipeline is indirectly controlled.

2. The nitrogen concentration detection method according to claim 1, characterized by, The diameter of the U-shaped tube is 25mm, the length is 130mm, the flow rate is 1500L / min, and the back pressure is 250kPaA.

3. The nitrogen concentration detection method according to claim 2, wherein: If the U-shaped tube contains pure hydrogen gas, the flow resistance is 160Pa; If the U-shaped tube contains wet hydrogen gas with a humidity of 100%, the flow resistance is 430Pa; If the U-shaped tube contains wet hydrogen gas with a humidity of 100% and a nitrogen / hydrogen volume ratio of 0.15, the flow resistance is 570Pa; If the U-shaped tube contains wet hydrogen gas with a humidity of 100% and a nitrogen / hydrogen volume ratio of 0.3, the flow resistance is 914Pa; By controlling the opening and closing of the nitrogen discharge valve, the flow resistance of the U-shaped tube is controlled below 570Pa, and the nitrogen concentration in the pipeline can be controlled below 15%.

Images