US-20260127342-A1 - DESIGN METHOD FOR SUPERCRITICAL CARBON DIOXIDE COMPRESSOR

US20260127342A1US 20260127342 A1US20260127342 A1US 20260127342A1US-20260127342-A1

Abstract

A design method for a supercritical carbon dioxide compressor includes: obtaining a performance curve of the supercritical carbon dioxide compressor based on the fluid similarity theory; performing off-design performance correction of the supercritical carbon dioxide compressor based on the performance curve; controlling a dry gas seal temperature of the supercritical carbon dioxide compressor based on a correspondence between temperature and pressure; and providing a fluid dynamic pressure gap between a high-speed shaft gear and a low-speed shaft gear in a gearbox of the supercritical carbon dioxide compressor, and adjusting a gearbox thrust through the fluid dynamic pressure gap.

Inventors

Yanping Huang
Liqin Zhang
Yaoxing CHEN
Lv YE
Le Ma
Xiuting Liu
Houjun GONG
Wenbin ZHUO
Yu Jiang
Bitan QIN

Assignees

NUCLEAR POWER INSTITUTE OF CHINA

Dates

Publication Date: 20260507
Application Date: 20251226
Priority Date: 20240722

Claims (20)

1 . A design method for a supercritical carbon dioxide compressor, comprising: obtaining a performance curve of the supercritical carbon dioxide compressor based on the fluid similarity theory; performing off-design performance correction of the supercritical carbon dioxide compressor based on the performance curve of the compressor; controlling a dry gas seal temperature of the supercritical carbon dioxide compressor based on a correspondence between temperature and pressure; and providing a fluid dynamic pressure gap between a high-speed shaft gear and a low-speed shaft gear in a gearbox of the supercritical carbon dioxide compressor, and adjusting a gearbox thrust through the fluid dynamic pressure gap.
2 . The design method for the supercritical carbon dioxide compressor according to claim 1 , wherein the obtaining the performance curve of the supercritical carbon dioxide compressor based on the fluid similarity theory comprises: equating each thermophysical property range of supercritical carbon dioxide to a corresponding thermophysical property range of an ideal working medium based on the fluid similarity theory; performing rated operating condition design and off-design condition design of the compressor based on the ideal working fluid, and obtaining a performance curve of the ideal working fluid; and scaling the performance curve of the compressor for the ideal working fluid back to the performance curve of the supercritical carbon dioxide compressor based on the fluid similarity theory.
3 . The design method for the supercritical carbon dioxide compressor according to claim 2 , wherein the performance index of the supercritical carbon dioxide comprises a pressure ratio, a mass flow rate, and an isentropic efficiency.
4 . The design method for the supercritical carbon dioxide compressor according to claim 3 , wherein the scaling the performance curve of the compressor for the ideal working medium back to the performance curve of the supercritical carbon dioxide compressor based on the fluid similarity theory comprises: obtaining the pressure ratio of the supercritical carbon dioxide based on Prandtl similarity and by equating an isentropic head coefficient; obtaining the mass flow rate of the supercritical carbon dioxide according to geometric similarity; and obtaining the isentropic efficiency of the supercritical carbon dioxide according to an empirical approximation relationship.
5 . The design method for the supercritical carbon dioxide compressor according to claim 2 , wherein the fluid similarity theory comprises Reynolds number similarity, Prandtl similarity, geometric similarity, and an empirical approximation relationship.
6 . The design method for the supercritical carbon dioxide compressor according to claim 5 , wherein the Prandtl similarity requires that an isentropic head coefficient and a specific speed of the supercritical carbon dioxide compressor are equal.
7 . The design method for the supercritical carbon dioxide compressor according to claim 5 , wherein the geometric similarity is ensured by equal flow coefficient, volumetric flow rate and rotational speed.
8 . The design method for the supercritical carbon dioxide compressor according to claim 1 , wherein the performing off-design performance correction of the supercritical carbon dioxide compressor based on the performance curve of the compressor comprises: drawing a performance curve graph of the supercritical carbon dioxide compressor under a design condition; searching, at the same rotational speed, for an operating condition with a same inlet flow rate on the performance curve graph under the design condition; and correcting the performance curve graph based on the operating condition with the same inlet flow rate to obtain the performance curve under an off-design condition.
9 . The design method for the supercritical carbon dioxide compressor according to claim 8 , wherein the performance curve graph at least comprises a total-to-static pressure ratio performance curve graph and a total-to-static isentropic efficiency performance curve graph.
10 . The design method for the supercritical carbon dioxide compressor according to claim 9 , wherein the total-to-static pressure ratio performance curve graph is corrected under a principle of constant enthalpy rise at the same inlet flow rate to obtain a total-to-static pressure ratio performance curve graph under the off-design condition.
11 . The design method for the supercritical carbon dioxide compressor according to claim 10 , wherein a surge line and a choke line are established on the total-to-static pressure ratio performance curve graph under the design condition based on a principle of constant inlet flow rate at the same rotational speed.
12 . The design method for the supercritical carbon dioxide compressor according to claim 9 , wherein the total-to-static isentropic efficiency performance curve graph is globally corrected according to an overall correction factor of the total-to-static isentropic efficiency to obtain the total-to-static isentropic efficiency performance curve graph under the off-design condition.
13 . The design method for the supercritical carbon dioxide compressor according to claim 12 , wherein the overall correction factor of the total-to-static isentropic efficiency is calculated by: obtaining a design flow and a design rotational speed corresponding to a point of maximum total-to-static isentropic efficiency at a rated speed in the total-to-static isentropic efficiency performance curve graph under the design condition; finding, according to a principle of equal inlet flow speed, a reference flow rate point under the off-design condition corresponding to the point of maximum total-to-static isentropic efficiency under the design condition, and calculating the total-to-static isentropic efficiency at the reference flow rate point; and calculating the overall correction factor of the total-to-static isentropic efficiency based on the total-to-static isentropic efficiency at the reference flow rate point and the maximum total-to-static isentropic efficiency under the design condition.
14 . The design method for the supercritical carbon dioxide compressor according to claim 13 , wherein the reference flow rate point under the off-design condition is located based on a design flow rate at the point of maximum total-to-static isentropic efficiency at the rated speed, according to the principle of equal inlet flow speed.
15 . The design method for the supercritical carbon dioxide compressor according to claim 13 , wherein a simulation calculation is performed to obtain the converted total-to-static isentropic efficiency based on an inlet pressure, an inlet temperature, the flow rate at the reference flow rate point, and a converted rotational speed under the off-design condition.
16 . The design method for the supercritical carbon dioxide compressor according to claim 15 , wherein the design rotational speed is converted into the converted rotational speed at the reference flow rate point under the off-design condition according to a principle of constant rotational speed.
17 . The design method for the supercritical carbon dioxide compressor according to claim 13 , wherein the overall correction factor of the total-to-static isentropic efficiency is a ratio of the total-to-static isentropic efficiency at the reference flow rate point to the maximum total-to-static isentropic efficiency under the design condition.
18 . The design method for the supercritical carbon dioxide compressor according to claim 1 , wherein controlling the dry gas seal temperature of the supercritical carbon dioxide compressor based on the correspondence between temperature and pressure comprises: suspending a dry gas seal device for implementing dry gas sealing on the gearbox of the supercritical carbon dioxide compressor, and introducing an injection gas flow into the dry gas seal device, wherein a relationship between pressure and temperature of the injection gas flow is as follows: T min = - 0 . 0 ⁢ 0 ⁢ 3 ⁢ 2 ⁢ P 3 + 0 . 0 ⁢ 0 ⁢ 4 ⁢ 1 ⁢ P 2 + 6 . 0 ⁢ 7 ⁢ 5 ⁢ 9 ⁢ P + 42.262 ; and T max = 0 . 0 ⁢ 1 ⁢ 1 ⁢ 8 ⁢ P 3 - 0 . 5 ⁢ 3 ⁢ 0 ⁢ 4 ⁢ P 2 + 11.581 P + 48.113 ; wherein T min is a lowest temperature of the introduced injection gas flow; T max is a highest temperature of the introduced injection gas flow; and P is the pressure of the introduced injection gas flow.
19 . The design method for the supercritical carbon dioxide compressor according to claim 18 , wherein an applicable range of the pressure of the injection ranges from 6 MPa to 20 MPa.
20 . The design method for the supercritical carbon dioxide compressor according to claim 18 , wherein the injection gas flow is split into a main gas flow and an isolation gas flow after being introduced into the dry gas seal device.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application is a continuation application of International Application No. PCT/CN2024/124447, filed on Oct. 12, 2024, which claims priority to Chinese Patent Application No. 202410981195.6, filed with the China National Intellectual Property Administration on Jul. 22, 2024. All of the aforementioned applications are incorporated herein by reference in their entireties. TECHNICAL FIELD The present application relates to the technical field of turbomachinery, and in particular to a design method for a supercritical carbon dioxide compressor. BACKGROUND The supercritical carbon dioxide thermodynamic cycle power generation technology is an emerging generalized power solution that leverages the unique physical properties of supercritical carbon dioxide as the working fluid, and achieves integrated matching of working fluid properties, cycle processes, and equipment innovations based on the principles of the Brayton cycle. This technology holds promise for rapid deployment in fields such as nuclear energy, solar thermal power, gas-fired power plants, waste heat recovery, and biomass power generation. It is expected to drive technological and industrial transformation in these areas, while also promoting the development of equipment manufacturing in the energy sector. As a core component of the supercritical carbon dioxide power conversion system, the compressor is responsible for providing the circulating power required by the system. The working fluid at the inlet of the supercritical carbon dioxide compressor is characterized by high density, which can effectively reduce the compressor's power consumption and thereby improve the cycle efficiency of the power conversion system. This makes the design of supercritical carbon dioxide turbomachinery a key area of focus for many research institutions. The high-density property of supercritical carbon dioxide results in compressor designs that feature compact size and high rotational speed, which in turn presents the following challenges in compressor design. The inlet temperature of the supercritical carbon dioxide compressor is usually very close to the critical point (7.38 MPa, 31.1° C.). However, the thermophysical properties of carbon dioxide undergo rapid changes near the critical point, resulting in large property interpolation errors and insufficient cavitation margin, which in turn makes compressor design challenging. Under actual operating conditions, the inlet temperature and the pressure of the compressor need to fluctuate within a certain range and deviate from the design operating condition point. However, the sharply varying thermophysical properties near the critical point can cause the inlet fluid density to deviate from the design value, thereby requiring off-design aerodynamic performance verification of the compressor. Performing numerical simulation and validation for each newly established combination of fluid temperature and pressure would result in a tremendous workload, making it difficult to meet the demands of rapid performance verification during system operation or simulation. The existing supercritical carbon dioxide compressors usually adopt dry gas seals and use bleed gas extracted from the main gas system, of which the compressor is a part, as the source of sealing gas. Since the pressure of the carbon dioxide working fluid in the main gas system generally ranges from 6 to 20 MPa, while the outlet pressure of the sealing gas is only slightly above atmospheric pressure, the large pressure differential can result in significant temperature changes in the carbon dioxide gas flow. Therefore, it is necessary to effectively regulate the outlet temperature of the sealing gas to ensure the stable operation of the dry gas seal. The gearbox of the supercritical carbon dioxide compressor needs to continuously operate at a high speed, resulting in significant bearing losses within the gearbox. This not only restricts the output power of the system, but also affects the effective operation of the system. In view of this, based on years of experience in production design in this field and related areas, has developed a design method for a supercritical carbon dioxide compressor through repeated experiments, aiming to solve the existing problems. SUMMARY The purpose of the present application is to provide a design method for a supercritical carbon dioxide compressor, which can effectively meet the design requirements of small volume and high rotating speed of the supercritical carbon dioxide compressor. In order to achieve the above purpose, the present application provides a design method of a supercritical carbon dioxide compressor. The design method includes: obtaining a performance curve of the supercritical carbon dioxide compressor based on the fluid similarity theory; performing off-design performance correction of the supercritical carbon dioxide compressor based on the performance curve; c