A design method for a single stage of an axial flow hydrogen compressor

Abstract

This invention relates to a design method for a single stage of an axial-flow hydrogen compressor. The initial design parameters of this single stage are limited by a low flow coefficient. Its aerodynamic design employs a high-response design to improve the efficiency of the moving blades. Furthermore, its geometric design utilizes a tandem stator design to facilitate axial hydrogen exhaust and improve the flow field within the stator blades. Then, through three-dimensional CFD calculations, the performance and internal flow field of the axial-flow hydrogen compressor at the design point and different speeds are obtained to verify whether the design requirements are met. Finally, through iterative iterations, a single stage of the axial-flow hydrogen compressor that meets the design requirements is obtained. This design method allows each single stage to function as a module, facilitating multi-stage stacking and effectively simplifying the design of axial-flow hydrogen compressors.

Description

Technical Field

[0001] This invention relates to axial flow compressors, and more specifically to a design method for a single stage of an axial flow hydrogen compressor. Background Technology

[0002] In the future, when hydrogen is used as an energy source, its application scenarios and scale will far exceed those of today. The establishment of a large-scale hydrogen energy transportation system will become the foundation and support for the development of the hydrogen economy. The establishment of a large-scale hydrogen energy transportation system means that hydrogen transportation will develop in the direction of large scale and long distance. Combined with hydrogen production from renewable energy sources, pipeline transportation is expected to become the optimal transportation mode, and the demand for hydrogen compressors suitable for large flow rates will become increasingly stronger.

[0003] Currently, centrifugal hydrogen compressors are mainly used for pipeline hydrogen transportation, with efficiencies generally around 80%. However, they suffer from complex flow channel structures and high manufacturing costs. Compared to centrifugal compressors, axial-flow compressors are better suited for large-scale, high-flow-rate transportation systems, and are simpler in structure and easier to maintain. By improving the pressurization capacity and efficiency of axial-flow hydrogen compressors, they can replace centrifugal compressors, significantly improving the economics of hydrogen pressurization. Centrifugal compressors typically have a much lower flow coefficient than axial-flow compressors; therefore, research is needed to develop low-flow-coefficient axial-flow hydrogen compressors to replace centrifugal hydrogen compressors.

[0004] To achieve good aerodynamic performance, the flow coefficients of existing axial compressors are mostly in the range of 0.3-0.6. For specific working conditions, performance is often improved by adding pre-swirl. However, the design of each stage must take into account the outlet angle of the previous stage, which leads to problems such as complicated design and time consumption. The working fluid is also mainly air, and there is little research on axial compressors with low flow coefficients and axial hydrogen compressors. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a novel design method for a single-stage axial-flow hydrogen compressor, used to study the use of low-flow-coefficient axial-flow hydrogen compressors to replace centrifugal hydrogen compressors. The technical solution is as follows:

[0006] A design method for a single-stage axial-flow hydrogen compressor is provided, which includes: initial design parameters are limited by a low flow coefficient; aerodynamic design employs a high reaction force design to improve blade efficiency; and geometric design uses a tandem stator design to allow hydrogen to exit axially. Then, three-dimensional CFD calculations are used to obtain the performance and internal flow field of the axial-flow hydrogen compressor at the design point and different speeds to determine whether the design requirements are met. The aerodynamic and geometric designs are iteratively performed until the design requirements are met.

[0007] Furthermore, the flow coefficient is less than 0.3.

[0008] Furthermore, the flow coefficient is 0.2.

[0009] Furthermore, the initial design includes: firstly, selecting aerodynamic parameters and designing a scheme based on the given initial conditions, calculating and evaluating the velocity triangle and airflow turning angle with the goal of maximizing efficiency and pressure ratio, and determining the initial impeller geometry parameters.

[0010] Furthermore, the initial conditions of the initial design include: inlet pressure, inlet temperature, single-stage pressure ratio, and inlet flow rate; based on the initial conditions, the aerodynamic parameters are selected by querying the hydrogen physical property parameters using the REFPROP real gas database.

[0011] Furthermore, the aerodynamic design includes: using a high-reaction force method to improve the degree of blade twist, obtaining the blade efficiency through three-dimensional calculation, so that the overall blade efficiency can reach the standard of centrifugal hydrogen compressor; calculating aerodynamic parameters for each section of the blade along the blade height, substituting the parameters into NREC software for design point-accurate three-dimensional aerodynamic calculation and flow channel shape optimization, and determining the impeller shape based on the flow channel calculation results.

[0012] Furthermore, the number of stationary blades in the tandem is two.

[0013] This invention achieves the following technical effects:

[0014] 1. An axial flow hydrogen compressor that goes beyond the comfort zone of flow coefficient and whose initial design parameters are based on a low flow coefficient;

[0015] 2. The aerodynamic design adopts a high reaction force design, which can effectively improve the efficiency of the axial flow hydrogen compressor motor blades;

[0016] 3. The geometric design adopts a tandem stator design to ensure axial hydrogen output and improve the flow field of the stator, thereby making the axial flow hydrogen compressor a single-stage modular unit that can be easily stacked with multiple stages. Attached Figure Description

[0017] Figure 1 This is a design flowchart of the present invention;

[0018] Figure 2 This is the position of the moving blade of a single stage of an axial flow hydrogen compressor according to an embodiment of the present invention on a Smith chart;

[0019] Figure 3 This is a schematic diagram of a velocity triangle according to an embodiment of the present invention;

[0020] Figure 4 This is a streamline diagram at the average diameter of the tandem stator blades according to an embodiment of the present invention;

[0021] Figure 5This is a pressure ratio-mass flow rate characteristic curve of an embodiment of the present invention;

[0022] Figure 6 This is an efficiency-mass flow rate characteristic curve of an embodiment of the present invention. Detailed Implementation

[0023] To further illustrate the various embodiments, the present invention provides accompanying drawings. These drawings are part of the disclosure of the present invention, primarily used to illustrate the embodiments, and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these drawings, those skilled in the art should be able to understand other possible implementations and the advantages of the present invention.

[0024] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0025] like Figure 1 As shown, this invention provides a design method for a single stage of an axial-flow hydrogen compressor, including the following design constraints and design process:

[0026] A single-stage axial-flow hydrogen compressor was designed with a low flow coefficient (less than 0.3) as its initial design parameter to accommodate hydrogen as the working fluid and to replace centrifugal hydrogen compressors with low flow coefficients. Its aerodynamic design employs a high-reaction force design to improve blade efficiency, and its geometric design uses a tandem stator design to allow hydrogen to exit axially. Then, three-dimensional CFD calculations were used to obtain the performance and internal flow field of the axial-flow hydrogen compressor at the design point and different speeds to determine if it meets the design requirements. The aerodynamic and geometric designs were iteratively refined until the design requirements were met.

[0027] The following provides further explanation of each step in the design process.

[0028] I. Low flow coefficient and high reaction force

[0029] First, aerodynamic parameters are selected and schemes are designed based on the given initial conditions (constraints). Under the given initial conditions, parameters such as velocity triangle and airflow turning angle are calculated and evaluated with the goal of maximizing efficiency, and the initial impeller geometry parameters are determined.

[0030] In this application, the working fluid is hydrogen. Therefore, the specific limitation of the axial flow hydrogen compressor is a low flow coefficient. Other initial conditions include inlet pressure, inlet temperature, single-stage pressure ratio, and inlet flow rate. The aerodynamic parameters can be selected by querying the hydrogen physical properties in the REFPROP real gas database, as shown in Table 1. Under these initial conditions, the aerodynamic parameters such as the load coefficient ψ and reaction force Ω are selected and the scheme is designed with the goal of maximizing efficiency and pressure ratio, thus determining the initial impeller geometry parameters.

[0031] The position of the moving blades of a single stage of this axial-flow hydrogen compressor on the Smith chart is as follows: Figure 2 As shown, the vertical axis represents the load factor ψ, and the horizontal axis represents the flow factor. This exceeds the comfort zone of conventional axial compressor design.

[0032] In this design, the flow coefficient The flow coefficient is below the range of conventional axial compressor designs, which is assumed here. Right now Its velocity triangle is as follows Figure 3 As shown, where c 1z Represents the axial inlet velocity (absolute inlet velocity), u m c1 represents the circumferential velocity at the average radius, c2 represents the absolute velocity at the outlet, W1 and W2 represent the relative velocities at the inlet and outlet respectively, Δc represents the degree of inflection of the absolute velocity, and α1 and α2 represent the absolute inlet angle and the absolute outlet angle respectively.

[0033] To improve the efficiency of the moving blades while ensuring high performance, a high counter-force (counter-force greater than 0.7) was used to reduce the blade twist, thereby decreasing airfoil and secondary flow losses. The final three-dimensional calculation yielded a moving blade efficiency of 86.4%. This allows the overall stage efficiency to reach the standard of a centrifugal hydrogen compressor, effectively replacing it. Data simulations show that the data is even better when the counter-force is equal to 0.9.

[0034] Then, aerodynamic parameters are calculated for each section of the moving blade along the blade height. The parameters are then substituted into NREC software (a special CAE / CAM software for turbomachinery design / machining) for design-point three-dimensional aerodynamic calculation and flow channel shape optimization. Based on the results of the flow channel calculation, the impeller shape is determined, and geometric parameters such as flow channel, blade angle, and blade thickness are optimized.

[0035] II. Serial still leaves

[0036] In a typical axial compressor design, the airflow deflection angle of the stator blades is only about 30 degrees, and a single row of stator blades can complete the operation. This is because Δc=ψu m Δc refers to the degree of absolute velocity change, ψ refers to the load factor, and u m This refers to the circumferential velocity at the average radius. When u... m The larger the value, the greater the degree of inflection of the airflow angle, and u m =5c 1z Due to limitations, the intake velocity should not be too low, meaning the Δc value is relatively large, which would result in a smaller α2. To achieve axial exhaust, the absolute airflow angle α2 needs to be rotated back to 90 degrees, at which point the stationary blade airflow turning angle will reach 65 degrees or even 70 degrees.

[0037] In a single-stage hydrogen compressor, under large airflow turning angles, a single stationary vane struggles to redirect the airflow to axial outlet, resulting in significant blade back separation, a chaotic flow field, and impacts overall stage efficiency. For example... Figure 4 As shown, the stator in a single stage of the hydrogen compressor uses a tandem stator consisting of stator blades 1 and 2. The tandem stator blades divide the airflow into two parts, directing the hydrogen to the axial outlet. This allows each stage to be stacked as a relatively independent module according to specific operating conditions, while also reducing the separation phenomenon of the stator blade suction surface and improving the flow field.

[0038] III. Three-dimensional CFD (Computational Fluid Dynamics) Calculation

[0039] The three-dimensional airfoil is subjected to three-dimensional CFD calculations and software analysis, including full three-dimensional CFD numerical simulation analysis of the compressor at the design point and under varying operating conditions. Through three-dimensional CFD calculations, the compressor's performance and internal flow field conditions at the design point and different speeds are obtained to determine if they meet the design requirements. If they do, the current compressor aerodynamic design scheme is the final design scheme; if not, based on the specific analysis results of the compressor's internal flow field, aerodynamic parameters and schemes are returned for design optimization, including flow channel calculations and airfoil geometry design. Through this iterative process, a final axial compressor aerodynamic design scheme that meets the design specifications is obtained. Figure 5 and Figure 6 The figure shows the characteristic curve of a single-stage blade of this low-flow-coefficient axial-flow hydrogen compressor.

[0040] In summary, the design method for a single stage of an axial-flow hydrogen compressor of the present invention has the following innovations:

[0041] 1. Stepping out of the comfort zone of flow coefficient, a low flow coefficient axial flow hydrogen compressor was designed;

[0042] 2. The aerodynamic design employs a high reaction force design, which can effectively improve the moving blade efficiency of the hydrogen compressor;

[0043] 3. For large airflow turning angles, a tandem stator blade is used to divert hydrogen to the axial outlet in two stages, making the single-stage modular and improving the stator blade flow field.

[0044] Table 1. Physical properties of hydrogen gas

[0045]

[0046] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A design method for a single stage of an axial-flow hydrogen compressor, characterized in that, This method is applied to a single stage of an axial-flow hydrogen compressor, including: initial design parameters limited by a low flow coefficient; aerodynamic design employing a high reaction force design to improve blade efficiency; and geometric design using a tandem stator design to allow hydrogen to exit axially. Then, through three-dimensional CFD calculations, the performance and internal flow field of the axial-flow hydrogen compressor at the design point and different speeds are obtained to determine whether the design requirements are met. The aerodynamic and geometric designs are iterated repeatedly until the design requirements are met. The initial design includes: firstly, selecting aerodynamic parameters and designing a scheme based on the given initial conditions; secondly, calculating and evaluating the velocity triangle and airflow turning angle with the goal of maximizing efficiency and pressure ratio; and thirdly, determining the initial impeller geometry parameters. The initial conditions for the initial design also include: inlet pressure, inlet temperature, single-stage pressure ratio, and inlet flow rate; based on the initial conditions, the aerodynamic parameters are selected by querying the hydrogen physical property parameters using the REFPROP real gas database. The aerodynamic design includes: using a high-reaction method to improve the degree of blade twist, obtaining the blade efficiency through three-dimensional calculation, so that the overall blade efficiency can reach the standard of centrifugal hydrogen compressor; using a high-reaction method to calculate aerodynamic parameters of each section of the blade along the blade height, substituting the parameters into NREC software for design point-accurate three-dimensional aerodynamic calculation and flow channel shape optimization, and determining the impeller shape based on the flow channel calculation results.

2. The design method for a single stage of an axial-flow hydrogen compressor as described in claim 1, characterized in that: The flow coefficient is less than 0.

3.

3. The design method for a single stage of an axial-flow hydrogen compressor as described in claim 2, characterized in that: The flow coefficient is 0.

2.

4. The design method for a single stage of an axial-flow hydrogen compressor as described in claim 1, characterized in that: The number of static leaves in the tandem is two.

Images