Design method for supercritical carbon dioxide compressor

Abstract

The present application relates to the technical field of turbomachinery. Provided is a design method for a supercritical carbon dioxide compressor. The design method for a supercritical carbon dioxide compressor comprises: on the basis of a fluid similarity theory, obtaining a performance curve of a supercritical carbon dioxide compressor; on the basis of the performance curve of the compressor, correcting the off-design performance of the supercritical carbon dioxide compressor; on the basis of the correlation between temperature and pressure, controlling the dry-gas seal temperature of the supercritical carbon dioxide compressor; and providing a hydrodynamic clearance between a high-speed shaft gear (101) and a low-speed shaft gear (111) in a gearbox of the supercritical carbon dioxide compressor, so as to adjust the thrust of the gearbox by means of the hydrodynamic clearance. The design method for a supercritical carbon dioxide compressor provided in the present application can effectively meet the design requirements for the supercritical carbon dioxide compressor, namely, a small volume and a high rotation speed.

Description

Supercritical carbon dioxide compressor design method

[0001] The present application claims priority to the Chinese patent application No. 2024109811956, filed on July 22, 2024, and entitled "Supercritical carbon dioxide compressor design method", the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the field of turbomachinery, in particular to a supercritical carbon dioxide compressor design method. BACKGROUND

[0003] Supercritical carbon dioxide thermodynamic cycle power generation technology is a new common power technology scheme that utilizes the physical property characteristics of supercritical carbon dioxide working medium, is based on the principle of Brayton cycle, and is formed by comprehensive matching of working medium properties, cycle process and equipment innovation. It is expected to be rapidly popularized and applied in the fields of nuclear energy, solar thermal, gas power plants, waste heat, biomass power generation, etc., bringing about technical and industrial changes in the above-mentioned fields, and driving the development of energy equipment manufacturing industry.

[0004] As the core equipment of the supercritical carbon dioxide power conversion system, the compressor is responsible for providing cycle power for the power conversion system. The supercritical carbon dioxide compressor inlet working medium has the characteristics of high density, which can effectively reduce the compressor power consumption and improve the cycle efficiency of the power conversion system. It is one of the key points for research institutes to design supercritical carbon dioxide turbine equipment. The high density of supercritical carbon dioxide makes the compressor design have the characteristics of small volume and high speed, which further poses the following challenges to the compressor design:

[0005] The inlet temperature of the supercritical carbon dioxide compressor is usually very close to the critical point (7.38 MPa, 31.1℃), but the sharp change of carbon dioxide properties near the critical point leads to large property interpolation and insufficient compressor cavitation / cavitation margin, making the compressor design difficult.

[0006] Under actual operating conditions, the compressor inlet temperature and pressure need to fluctuate within a certain range and deviate from the design operating point. The sharp change of properties near the critical point will cause the inlet working medium density to deviate from the design point, resulting in the need for off-design condition checking of the compressor aerodynamic performance. Performing numerical simulation and checking for each newly established working medium temperature and pressure will result in a very large amount of work and cannot meet the rapid checking requirements of system operation or simulation.

[0007] The existing supercritical carbon dioxide compressor usually adopts dry gas seal and uses the gas extracted from the main gas system to which the supercritical carbon dioxide compressor belongs as the source of isolation gas. Since the carbon dioxide working medium pressure in the main gas system is usually 6-20 MPa, and the isolation gas outlet pressure is only slightly positive, the carbon dioxide gas flow temperature changes greatly under such a large pressure difference, and the gas outlet temperature needs to be effectively managed to ensure the stable operation of the dry gas seal.

[0008] The gear box of the supercritical carbon dioxide compressor needs to run continuously at high speed, so that the bearing loss in the gear box is particularly large, which not only restricts the system output power, but also affects the effective operation of the system.

[0009] Therefore, based on years of production and design experience in this field and related fields, the applicant has designed a supercritical carbon dioxide compressor design method through repeated tests, in order to solve the problems existing in the prior art.

[0010] Application content

[0011] The purpose of the present application is to provide a supercritical carbon dioxide compressor design method, which can effectively meet the design requirements of small volume and high speed of the supercritical carbon dioxide compressor.

[0012] In order to achieve the above purpose, the present application provides a supercritical carbon dioxide compressor design method, wherein the supercritical carbon dioxide compressor design method comprises:

[0013] Obtaining the performance curve of the supercritical carbon dioxide compressor based on the fluid similarity theory;

[0014] Performing off-design performance correction of the supercritical carbon dioxide compressor based on the compressor performance curve;

[0015] Controlling the dry gas seal temperature of the supercritical carbon dioxide compressor based on the corresponding relationship between temperature and pressure;

[0016] A fluid dynamic pressure gap is arranged between the high-speed shaft gear and the low-speed shaft gear in the gear box of the supercritical carbon dioxide compressor, and the gear box thrust is adjusted through the fluid dynamic pressure gap.

[0017] Compared with the prior art, the present application has the following characteristics and advantages:

[0018] The supercritical carbon dioxide compressor design method provided in the application equates the property interval of supercritical carbon dioxide to the property interval of an ideal working medium, avoids the problem of sharp change of the property of supercritical carbon dioxide in the critical region, and then designs the rated working condition and variable working condition of the compressor according to the equivalent ideal working medium, and finally scales the performance curve of the equivalent ideal working medium compressor back to the performance curve of the supercritical carbon dioxide compressor according to the fluid similarity theory, thereby solving the problem of sharp change of the property of supercritical carbon dioxide in the critical region, which leads to inaccurate property interpolation and difficulty in designing a supercritical carbon dioxide compressor, and providing technical support and guidance for the design of a supercritical carbon dioxide compressor and a high-efficiency supercritical carbon dioxide cycle.

[0019] The supercritical carbon dioxide compressor design method provided in the application can quickly obtain the performance curve of the supercritical carbon dioxide compressor under the partial working condition through the performance curve under the partial working condition, and quickly and accurately calculate the compressor performance of the supercritical carbon dioxide compressor under the partial working condition, thereby simplifying the calculation workload of the compressor under the partial working condition, greatly saving the calculation time and calculation resources, and meeting the corresponding requirements of the rapid iteration of the compressor.

[0020] The supercritical carbon dioxide compressor design method provided in the application limits the relationship between the temperature and pressure of the injection gas flow introduced into the dry gas seal to ensure that the temperature of the leakage gas flow of the dry gas seal is close to the oil inlet temperature of the oil bearing in the gear box, so as to ensure the safety of the bearing.

[0021] The supercritical carbon dioxide compressor design method provided in the application sets a hydrodynamic pressure gap between the high-speed shaft gear and the low-speed shaft gear of the gear box, transmits the thrust of the high-speed shaft gear to the low-speed shaft gear through the hydrodynamic pressure gap, and then balances the thrust of the low-speed shaft gear, which can significantly improve the efficiency of the gear box and the overall output power of the compressor unit. BRIEF DESCRIPTION OF DRAWINGS

[0022] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the disclosure in any way. In addition, the shapes and scale sizes of the components in the drawings are only illustrative and are used to help understand the application, and are not specific limitations on the shapes and scale sizes of the components. Those skilled in the art can select various possible shapes and scale sizes to implement the application according to specific circumstances under the guidance of the application.

[0023] Fig. 1 is a schematic diagram of a supercritical carbon dioxide cycle in the application;

[0024] Fig. 2 is a schematic diagram of the partial working condition correction method based on the compressor performance curve check provided in the application;

[0025] Fig. 3 is a plot of the pressure ratio performance of a supercritical carbon dioxide compressor under design conditions;

[0026] Fig. 4 is a plot of the efficiency performance of a supercritical carbon dioxide compressor under design conditions;

[0027] Fig. 5 is a plot of the pressure ratio performance of a supercritical carbon dioxide compressor under off-design conditions;

[0028] Fig. 6 is a plot of the efficiency performance of a supercritical carbon dioxide compressor under off-design conditions;

[0029] Fig. 7 is a layout of the dry gas seal device in the present application;

[0030] Fig. 8 is an enlarged view of a part of the dry gas seal device in the present application;

[0031] Fig. 9 is a schematic view of the thrust transmission structure of the gear box in the present application;

[0032] Fig. 10 is an enlarged view of a part of the thrust transmission structure of the gear box in the present application (I);

[0033] Fig. 11 is an enlarged view of a part of the thrust transmission wedge surface of the gear box in the present application (II);

[0034] Fig. 12 is an enlarged view of a part of the thrust transmission wedge surface of the gear box in the present application (III);

[0035] Fig. 13 is a schematic view of the thrust balance structure of the gear box in the present application.

[0036] BRIEF DESCRIPTION OF THE DRAWINGS 1, compressor inlet; 2, compressor outlet; 3, turbine inlet; 4, turbine outlet; 5, critical point of carbon dioxide; 6, surge line; 7, choke line; 81, point of maximum total static isentropic efficiency; 82, point of reference flow rate; 9, gear box body; 10, high speed shaft; 101, high speed shaft gear; 11, low speed shaft; 111, low speed shaft gear; 12, high speed rotating shaft bearing; 13, low speed rotating shaft bearing; 15, resistance element; 16, pressure reducing valve; 17, orifice; 18, pressure regulating groove; 20, seal cylinder; 23, dynamic ring; 24, static ring; 25, spring; 27, shaft thrust disc; 28, thrust bearing; 29, thrust disc; 30, left side gap; 31, right side gap; 32, maximum height; 33, radial height of wedge surface; 34, radial height of low speed shaft gear. DETAILED DESCRIPTION

[0037] The details of the application can be more clearly understood in conjunction with the accompanying drawings and the description of the embodiments of the application. However, the embodiments of the application described herein are only for the purpose of explaining the application and should not be understood as limiting the application in any way. Based on the teachings of the application, a skilled person can conceive any possible modification based on the application, which should be considered as falling within the scope of the application.

[0038] The application provides a supercritical carbon dioxide compressor design method, which comprises the following steps:

[0039] Obtaining a supercritical carbon dioxide compressor performance curve based on fluid similarity theory;

[0040] Performing off-design performance correction of the supercritical carbon dioxide compressor based on the compressor performance curve;

[0041] Controlling the dry gas seal temperature of the supercritical carbon dioxide compressor based on the corresponding relationship between temperature and pressure;

[0042] A fluid dynamic pressure gap is arranged between the high-speed shaft gear and the low-speed shaft gear in the gear box of the supercritical carbon dioxide compressor, and the gear box thrust is adjusted through the fluid dynamic pressure gap.

[0043] The supercritical carbon dioxide compressor design method provided by the application equates the property interval of supercritical carbon dioxide to the property interval of an ideal working medium. Since the properties of the ideal working medium do not change sharply in a heat cycle, the problem of sharp change of the properties of supercritical carbon dioxide is avoided. Then, the rated working condition design and the variable working condition design are performed according to the equivalent ideal working medium. Finally, the performance curve of the equivalent ideal working medium compressor is scaled back to the performance curve of the supercritical carbon dioxide compressor according to the fluid similarity theory, thereby solving the problem of inaccurate property interpolation and difficult design of the supercritical carbon dioxide compressor caused by the sharp change of the properties of supercritical carbon dioxide, and providing technical support and guidance for the design of the supercritical carbon dioxide compressor and the high-efficiency supercritical carbon dioxide cycle.

[0044] The supercritical carbon dioxide compressor design method provided by the application performs off-design aerodynamic performance correction based on the performance curve diagram under the design working condition, can quickly obtain the performance curve diagram of the supercritical carbon dioxide compressor under the off-design working condition, and can quickly and accurately calculate the compressor performance of the supercritical carbon dioxide compressor under the off-design working condition through the performance curve diagram under the off-design working condition. Not only is the calculation workload of the off-design working condition of the compressor simplified, but also the calculation time and resources are greatly saved, and the corresponding requirement for fast iteration of the compressor is met.

[0045] The design method of the supercritical carbon dioxide compressor limits the relationship between the temperature and pressure of the injection gas flow introduced into the dry gas seal to ensure that the temperature of the dry gas seal leakage flow is close to the oil inlet temperature of the oil bearing in the gearbox, thereby ensuring the safety of the bearing.

[0046] The design method of the supercritical carbon dioxide compressor sets a hydrodynamic pressure gap between the high-speed shaft gear and the low-speed shaft gear of the gearbox, transmits the thrust of the high-speed shaft gear to the low-speed shaft gear through the hydrodynamic pressure gap, and then balances the thrust of the low-speed shaft gear, thereby significantly improving the efficiency of the gearbox and the overall output power of the compressor unit.

[0047] In an optional embodiment of the present application, as shown in FIG. 2, the design method of the supercritical carbon dioxide compressor is based on the fluid similarity theory to equivalently map each property interval of the supercritical carbon dioxide to the corresponding property interval of an ideal working fluid, to design the rated working condition and the variable working condition of the compressor according to the ideal working fluid and obtain the performance curves of the ideal working fluid compressors, and to scale the performance curves of the ideal working fluid compressors back to the performance curves of the supercritical carbon dioxide compressor according to the fluid similarity theory.

[0048] In an optional embodiment, at the inlet of the supercritical carbon dioxide centrifugal machine, the carbon dioxide is in a supercooled liquid state; and at the outlet of the supercritical carbon dioxide centrifugal machine, the carbon dioxide is in a supercritical state.

[0049] As shown in FIG. 1, the supercritical carbon dioxide cycle refers to a carbon dioxide cycle mode in which the temperature and pressure at the inlet of the compressor (the position of point 1 in FIG. 1) are lower than the critical point (the position of point 5 in FIG. 1). Compared with the supercritical carbon dioxide cycle, the reduced inlet temperature of the supercritical carbon dioxide cycle compressor is conducive to improving the cycle efficiency and thus improving the system power generation, thereby achieving considerable economic benefits.

[0050] It should be noted that the pressure of the critical point is 7.38 MPa, and the temperature is 31.1℃.

[0051] In an optional embodiment of the present application, the performance indicators of the supercritical carbon dioxide include the pressure ratio, the mass flow rate, and the isentropic efficiency.

[0052] In this embodiment, the pressure ratio and the mass flow rate of the supercritical carbon dioxide are equivalently mapped to the corresponding property interval of an ideal working fluid based on the fluid similarity theory. The ideal working fluid can be one kind or multiple kinds.

[0053] In an optional example of this embodiment, the fluid similarity theory includes the Reynolds number similarity, the Prandtl number similarity, the geometric similarity, and the approximate empirical relationship.

[0054] In an alternative example of the present application, the design point includes calculating parameters of the compressor, including, in particular, the compressor head coefficient and specific speed, the compressor inlet diameter, the compressor wheel exit velocity and the compressor wheel exit diameter.

[0055] In particular, the Reynolds number is a basic similarity criterion that ensures similar fluid flow characteristics, and is defined as follows:

[0056] where p is the fluid density, V is the fluid velocity, D is the compressor inlet diameter, μ is the dynamic viscosity coefficient, and Re is the Reynolds number. D

[0057] The specific heat coefficient at constant pressure and other physical parameters of supercritical carbon dioxide vary sharply, so the Prandtl number, which characterizes the fluid heat transfer capacity, is used as a similarity criterion, and is defined as follows:

[0058] where v is the kinematic viscosity coefficient, a is the thermal diffusion coefficient, and Pr is the Prandtl number.

[0059] Further, the Prandtl number similarity requires that the compressor head coefficient and the specific speed be equal, and the compressor head coefficient and the specific speed are defined as follows, respectively:

[0060] where H is the compressor head coefficient, z is the average compression coefficient between the inlet and outlet of the compressor, R is the carbon dioxide gas constant, T t,in is the inlet total temperature, k is the specific heat ratio, π c is the pressure ratio between the inlet and outlet, ω is the rotor angular velocity, Q is the inlet volume flow rate, and n s is the specific speed.

[0061] The geometric similarity is ensured by the equality of the flow coefficient, the volume flow rate, and the speed. The flow coefficient is defined as follows:

[0062] where V2 is the compressor wheel exit velocity, D2 is the compressor wheel exit diameter, Q is the inlet volume flow rate, is the flow coefficient.

[0063] In this embodiment, the compressor design method in each equivalent ideal working fluid is a 2D average line method, i.e., a compressor speed triangle diagram considering various loss models is used to predict the compressor off-design variation.

[0064] In an alternative embodiment of the present application, the performance curve of the ideal working fluid is scaled back to the supercritical carbon dioxide performance curve, including:

[0065] ​The pressure ratio of supercritical carbon dioxide is converted according to Prandtl similarity and equal isentropic head coefficient; specifically, the pressure ratio of the supercritical carbon dioxide compressor is converted according to the isentropic head coefficient as follows:

[0066] In the formula, π C is the pressure ratio of the supercritical carbon dioxide compressor; Z ideal , K ideal , D ideal , T ideal , π C * respectively are the average compression coefficient of the compressor inlet and outlet of the equivalent ideal working medium, gas constant, inlet total temperature, specific heat ratio, and pressure ratio of the inlet and outlet; Z co2 , K co2 , D co2 , T co2 respectively are the average compression coefficient of the compressor inlet and outlet of the carbon dioxide, gas constant, and inlet total temperature.

[0067] The mass flow rate of supercritical carbon dioxide is converted according to geometric similarity, and the mass flow rate of the supercritical carbon dioxide compressor after conversion is as follows:

[0068] In the formula, ρ co2 , ρ ideal , m ideal respectively are the density of carbon dioxide, the density of the equivalent ideal working medium, and the mass flow rate of the equivalent ideal working medium, and m co2 is the mass flow rate of the supercritical carbon dioxide compressor.

[0069] The isentropic efficiency of supercritical carbon dioxide is obtained by scaling according to an approximate empirical relationship, and the empirical relationship used is as follows:

[0070] In the formula, η CO2 is the expansion index of carbon dioxide, η ideal is the expansion index of the equivalent ideal working medium, D 2， ideal is the total temperature of the compressor outlet of the equivalent ideal working medium, and D 2，co2 is the total temperature of the compressor outlet of carbon dioxide.

[0071] At the same time, under the rated operating condition, the impeller outlet diameter ratio is solved as follows:

[0072] In the formula, h t1 is the inlet total enthalpy, ε is the slip factor, D 2，ideal is the total temperature of the compressor outlet of the equivalent ideal working medium, D 2，co2 is the total temperature of the compressor outlet of carbon dioxide, and π Cwhere P is the pressure ratio of the supercritical CO2 compressor, k is the specific heat ratio.

[0073] Therefore, the expansion index n can be obtained according to the impeller outlet diameter ratio under the rated working condition of the compressor and equation (7), so that the complete empirical relationship of the isentropic efficiency is obtained.

[0074] In an optional embodiment of the present application, as shown in FIG. 2, the off-design performance correction of the supercritical CO2 compressor based on the performance curve of the compressor includes: drawing a performance curve diagram of the supercritical CO2 compressor under the design working condition of the compressor;

[0075] Finding the inlet flow rate equal condition under the same speed on the performance curve diagram under the design working condition;

[0076] Correcting the performance curve diagram based on the inlet flow rate equal condition and obtaining the performance curve diagram under the off-design working condition.

[0077] The off-design performance correction method of the performance curve of the supercritical CO2 compressor provided in the present application corrects the off-design aerodynamic performance based on the performance curve diagram under the design working condition, and obtains the entire off-design performance curve diagram through single off-design calculation simulation, which greatly shortens the calculation time and calculation workload and can meet the rapid and high-frequency iteration requirements of system operation or simulation.

[0078] In the present application, the off-design working condition refers to that the temperature and pressure of the inlet of the supercritical CO2 compressor deviate from the design values. When the temperature or pressure of the inlet of the supercritical CO2 compressor deviates from the design values, the performance curve of the supercritical CO2 compressor changes significantly, and the performance curve of the supercritical CO2 compressor needs to be recalculated to accurately predict the actual performance of the supercritical CO2 compressor, such as the pressure boosting capacity and work efficiency.

[0079] In an optional embodiment, as shown in FIG. 3 and FIG. 4, the performance curve diagram includes at least a total static pressure ratio performance curve diagram and a total static isentropic efficiency performance curve diagram.

[0080] In an optional example of the embodiment, as shown in FIG. 5, the total static pressure ratio performance curve diagram under the off-design working condition is obtained by correcting the total static pressure ratio performance curve diagram using the principle of constant enthalpy rise under the same inlet flow rate (as shown in FIG. 5).

[0081] Specifically, when the compressor inlet temperature is increased by 2℃ and the pressure remains unchanged, the design operating point is taken as an example with full speed and flow rate of 22kg / s. The compressor inlet temperature is increased by 2℃, which makes the inlet density decrease to 69.4% of the original design condition. The compressor flow rate is proportional to the product of density, flow velocity and inlet area. Therefore, under the condition of constant flow velocity and fixed inlet area, the decrease of density leads to the decrease of compressor operating flow rate under the same flow velocity. The specific satisfaction is as follows:

[0082] In the formula, m x is the corrected flow rate under the same speed and flow rate; p x is the inlet density under the off-design condition of the compressor; p o is the inlet density of the compressor under the original design condition, m o is the flow rate of the compressor under the original design condition.

[0083] Under the design condition of the compressor, the work done by the compressor is actually the increase of enthalpy value. However, since the change of outlet pressure of the compressor is irrelevant to the change of entropy, the outlet pressure of the compressor can be calculated according to the isentropic enthalpy value, i.e. h=h inlet +Δh (11)

[0084] In the formula, h is the isentropic enthalpy value of the compressor outlet under any operating condition, h inlet is the inlet enthalpy of the compressor, and Δh is the isentropic pressure rise enthalpy value of the compressor.

[0085] Therefore, when the enthalpy value remains unchanged under the same flow rate, the isentropic work capacity of the compressor under the off-design condition is corrected as follows: h′=h inlet ′+Δh (12)

[0086] In the formula, h' is the isentropic enthalpy value of the compressor outlet under any operating condition under the off-design condition, h inlet ' is the inlet enthalpy of the compressor under the off-design condition, and Δh is the isentropic pressure rise enthalpy value of the compressor which remains unchanged.

[0087] According to the isentropic enthalpy value recalculated, the static pressure of the compressor outlet under the off-design condition can be found from the supercritical carbon dioxide property library. Then, the ratio of the static pressure of the compressor outlet under the off-design condition to the total pressure of the compressor inlet under the off-design condition is the total static pressure ratio under the off-design condition.

[0088] In fact, the corrected total static pressure ratio is highly consistent with the recalculated total static pressure ratio, because for the supercritical carbon dioxide compressor, the energy process of the impeller work satisfies the following equation: Δh=C 2u U2-C 1uU1 (13)

[0089] wherein C 2u , C 1u are the tangential velocity of the outlet flow and the tangential velocity of the inlet flow of the impeller respectively; U2, U1 are the outlet peripheral velocity and the inlet peripheral velocity respectively, and Δh is the isentropic enthalpy rise of the compressor.

[0090] For the axial inlet compressor, the axial velocity of the inlet flow is 0, so the above equation can be further simplified as follows: Δh = C 2u U2 (14)

[0091] wherein C 2u is the tangential velocity of the outlet flow of the impeller; U2 is the outlet peripheral velocity, and Δh is the isentropic enthalpy rise of the compressor.

[0092] Further, for the compressor, most of the velocity in the outlet flow velocity of the impeller is the tangential velocity, and the proportion of the radial velocity is very small, so in the simplified calculation, C 2u can be approximately equivalent to U2, so the equation can be further simplified as follows: Δh ≈ U2 2 ≈ (ωR2) 2 (15)

[0093] wherein ω is the angular velocity, R2 is the outlet radius of the impeller, U2 is the outlet peripheral velocity, and Δh is the isentropic enthalpy rise of the compressor which remains unchanged.

[0094] Therefore, based on the above, it can be found that when the rotational speed and the impeller geometric parameters remain unchanged, the work capacity of the compressor remains basically unchanged, which is the reason why the enthalpy rise is unchanged in the present embodiment to correct the pressure ratio and obtain good results.

[0095] In an alternative example, the surge line 6 and the choke line 7 are established on the total static pressure ratio performance curve at the design operating condition according to the principle that the inlet flow velocity remains unchanged at the same rotational speed.

[0096] The surge line and the choke line are important boundaries and evaluation indexes for safe operation of the compressor, the surge line represents the minimum flow operating boundary of the compressor, and the choke line represents the maximum flow operating boundary of the compressor, when the inlet temperature or pressure of the compressor deviates from the design operating condition, the surge line and the choke line need to be recalculated according to the following calculation formula:

[0097] wherein m x is the corrected flow at the deviated operating condition; ρ xρin is the inlet density of the compressor under the off-design condition o ρin,0 is the inlet density of the compressor under the original design condition, m / s o ρin,0 is the inlet density of the compressor under the original design condition, m / s

[0098] In an optional embodiment of the present application, the overall correction coefficient of the total static isentropic efficiency is used to correct the total static isentropic efficiency performance curve under the design condition to obtain the total static isentropic efficiency performance curve under the off-design condition (as shown in FIG. 6), so that the performance relationship curve of the efficiency-flow rate under all rotating speeds including full speed, 80% speed and 60% speed can be obtained through single correction, greatly simplifying the calculation amount.

[0099] In the present embodiment, the principle of overall correction is proposed on the basis of keeping the compressor speed triangle unchanged (i.e. keeping the inlet flow rate unchanged, keeping the impeller axial speed unchanged and keeping the geometric structure unchanged), so that the impeller work capacity remains unchanged. When the compressor inlet temperature increases, the pressure increasing capacity decreases, resulting in a decrease in density, which will result in a decrease in friction loss and the like under the off-design condition compared to the design condition, so that the predicted value under the off-design condition is slightly higher than the corrected value when the compressor inlet temperature increases. However, overall, in the present embodiment, the deviation between the corrected efficiency and the predicted efficiency under the off-design condition is not more than 3%, and this precision level can already meet the requirements for rapid prediction.

[0100] In an optional example of the present embodiment, the calculation method of the overall correction coefficient of the total static isentropic efficiency comprises:

[0101] As shown in FIG. 4, the design flow rate and the design rotating speed corresponding to the maximum total static isentropic efficiency point 81 under the rated rotating speed in the total static isentropic efficiency performance curve under the design condition are obtained.

[0102] As shown in FIG. 6, the off-design reference flow rate point 82 corresponding to the maximum total static isentropic efficiency under the design condition is found according to the principle of equal inlet flow rate, and the total static isentropic efficiency at the reference flow rate point is calculated.

[0103] The overall correction coefficient of the total static isentropic efficiency is calculated according to the total static isentropic efficiency at the reference flow rate point and the maximum total static isentropic efficiency under the design condition.

[0104] In an optional example, the off-design reference flow rate point 82 is found according to the principle of equal inlet flow rate through the design flow rate at the maximum total static isentropic efficiency point 81 under the rated rotating speed.

[0105] Further, the converted total static isentropic efficiency is obtained through simulation calculation according to the inlet pressure, temperature under the off-design condition and the flow rate, converted rotating speed of the reference flow rate point.

[0106] Further, the design rotating speed is converted into the converted rotating speed of the reference flow point under the partial working condition according to the constant rotating speed principle.

[0107] In an optional example, the overall correction coefficient of the total static isentropic efficiency is the ratio of the total static isentropic efficiency at the reference flow point to the maximum total static isentropic efficiency under the design working condition.

[0108] In an optional embodiment of the present application, the dry gas seal temperature of the supercritical carbon dioxide compressor is controlled based on the corresponding relationship between temperature and pressure, and the method comprises the following steps:

[0109] A dry gas seal device for realizing dry gas seal is hung on the gear box of the supercritical carbon dioxide compressor, and an injection gas flow is introduced into the dry gas seal device.

[0110] The relationship between the gas flow pressure and the temperature of the injection gas flow is as follows: T min =-0.0032P 3 +0.0041P 2 +6.0759P+42.262 (17) T max =0.0118P 3 -0.5304P 2 +11.581P+48.113 (18)

[0111] In the formula, T min is the minimum temperature of the introduced injection gas flow; T max is the maximum temperature of the introduced injection gas flow; and P is the gas flow pressure of the introduced injection gas flow.

[0112] In the embodiment, the temperature of the dry gas seal leakage gas is adjusted by the limiting relationship between the temperature and the pressure of the total gas flow at the inlet of the dry gas seal device, and the deviation amplitude of the temperature of the dry gas seal leakage gas from the bearing inlet oil temperature is controlled within the range of ±0.4℃, so as to ensure the safety of the bearing.

[0113] In an optional embodiment, the gas flow pressure of the injection gas flow is in the range of 6MPa-20MPa.

[0114] In an optional embodiment, 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. As shown in FIGS. 7 and 8, specifically, the main gas flow is used to flow into the seal cylinder of the dry gas seal device, so as to form a rigid gas film between the dynamic ring and the static ring; the isolation gas flow is parallel to the main gas flow, and the isolation gas flow is used to flow into the gearbox, so as to play an oil-gas isolation role. By limiting the relationship between the temperature and the pressure of the total gas flow before the dry gas seal main gas flow and the isolation gas flow are split upstream, the temperature of the dry gas seal leakage gas flow and the outlet gas flow of the isolation gas flow are ensured to be close to the bearing oil inlet temperature, so that the oil inlet temperature of the oil bearing in the downstream gearbox can be kept within the use range, thereby ensuring the safety of the bearing use.

[0115] In an optional example, when the outlet gas flow of the dry gas seal leakage gas flow and the isolation gas flow is highest up to 62°C, the highest temperature of the total gas flow at the inlet of the dry gas seal device is not more than 162°C under the condition that the pressure of the total gas flow is 20 MPa; when the outlet gas flow of the dry gas seal leakage gas flow and the isolation gas flow is lowest down to 20°C, the lowest temperature of the total gas flow at the inlet of the dry gas seal device is not less than 139°C under the condition that the pressure of the total gas flow is 20 MPa.

[0116] In an optional example, the dry gas seal device includes a seal cylinder 20 and a dynamic ring 23 and a static ring 24 arranged inside the seal cylinder 20. As known from the prior art, the side of the static ring 24 away from the dynamic ring 23 is usually provided with a spring 25 to exert a close contact force thereon, so as to ensure the close contact of the dynamic ring and the static ring under the static condition. During the operation of the dry gas seal, the dynamic ring 23 and the static ring 24 cooperate with each other, and the injection gas flow can form a rigid gas film between the dynamic ring 23 and the static ring 24. When the static pressure of the fluid and the closing force of the spring 25 load are equal to the opening force generated in the gas film, a stable gap between the radial surfaces is formed.

[0117] In an optional embodiment, a resistance member 15, a pressure reducing valve 16 and a throttle hole 17 are sequentially arranged along the flow direction of the isolation gas flow, and the isolation gas flow is gradually depressurized through the resistance member 15, the pressure reducing valve 16 and the throttle hole 17, so as to meet the requirements of large final pressure drop of the isolation gas flow and no frosting of the throat of the pressure reducing valve 16, and provide support for the design and safe operation of the supercritical carbon dioxide compressor or turbine.

[0118] In an alternative example, the pressure drop distribution principle of the isolated gas flow is that the minimum isentropic expansion temperature at the throat of the pressure reducing valve 16 is higher than zero Celsius to further ensure the requirement that the throat of the pressure reducing valve 16 is not frosted. When the temperature at the throat of the pressure reducing valve 16 is lower than zero Celsius, the water in the external air working medium will be frosted on the surface of the valve stem of the pressure reducing valve 16, which may cause the pressure reducing valve 16 to be stuck and automatic control to be difficult, and thus needs to be avoided. The throat of the pressure reducing valve 16 is suddenly expanded, and the temperature at this position is considered in the isentropic state. To avoid that the temperature of the supercritical carbon dioxide is lower than zero Celsius in the isentropic expansion state of a large pressure drop, the pressure difference before and after the pressure reducing valve 16 needs to be limited, and it is suggested that the pressure difference before and after the pressure reducing valve 16 is not more than 9-11 MPa, and the rest of the pressure drop is borne by the resistance element 15 upstream of the pressure reducing valve 16 and the throttling hole 17 downstream of the pressure reducing valve 16.

[0119] In an alternative example, a pressure regulating groove 18 is further arranged on the flow branch of the isolated gas flow, and the isolated gas sequentially passes through the resistance element 15, the pressure reducing valve 16, the throttling hole 17 and the pressure regulating groove 18 to enter the downstream of the dynamic ring 23 and the static ring 24 of the dry gas seal device for oil and gas isolation.

[0120] Further, the pressure regulating groove 18 is arranged on the gear box body, so that the wall thickness advantage of the gear box body can be fully utilized to reduce the axial length of the rotating shaft and improve the critical speed of the rotor, and thus it is beneficial to increase the critical speed avoidance rate margin and reduce the vibration amplitude during operation.

[0121] In an alternative example, the gas flow pressure downstream of the dynamic ring 23 and the static ring 24 of the dry gas seal device is 0.11-0.15 MPa(a). According to the design specification, the gas outlet flow of the isolated gas flow needs to meet the requirement that the flow rate is not less than 5 m / s to effectively prevent the reverse stringing of oil and gas. Considering that the gas source of the isolated gas flow comes from the main loop system of the compressor or turbine, in order to reduce the power loss caused by the isolated gas, it is necessary to reduce the use amount of the isolated gas as low as possible. Under the condition that the geometric size is determined, reducing the pressure can effectively improve the gas flow speed and improve the use effect by controlling the density of the isolated gas flow. On the other hand, if the bearing oil pressure in the downstream gear box is too high, the power consumption of the configured oil circuit system will increase, the bearing wear loss will increase, and the lubricating oil may be sprayed out of the bearing. After comprehensive consideration, the downstream gas flow pressure is selected to be 0.11-0.15 MPa(a).

[0122] Further, the total mass of the leakage flow and the isolation flow downstream of the dynamic ring 23 and the static ring 24 of the dry gas seal device is not higher than 5% of the mass of the bearing oil inlet. Specifically, the bearing oil inlet temperature can make the lubricating oil viscosity too high, causing the unit loss to increase, the bearing temperature to rise too high, and thus possibly triggering an alarm shutdown, and the bearing oil inlet temperature can cause the oil to oxidize and deteriorate, triggering a bearing failure accident. It is generally recommended that the bearing inlet oil temperature be controlled within the range of 36-46°C. Since the leakage flow and the isolation flow of the dry gas seal in the zero leakage scenario directly flow through the bearing, too high a mass of the leakage flow can cause the bearing oil inlet temperature to be more susceptible to fluctuations in the temperature of the flow. Therefore, in order to reduce the sensitivity of the flow temperature to the bearing oil temperature, according to existing design experience, the total mass of the leakage flow and the isolation flow is required to be not higher than 5% of the mass of the bearing oil inlet. Under this design condition, a deviation of 4°C in the outlet flow temperature of the dry gas seal and the isolation gas will cause a deviation of 0.1°C in the bearing inlet oil temperature, greatly improving the safety and convenience of operation.

[0123] In an optional embodiment of the present application, as shown in FIGS. 9-13, a hydrodynamic gap is provided between the high-speed shaft gear 101 and the low-speed shaft gear 111 in the gearbox of the supercritical carbon dioxide compressor, and the gearbox thrust is adjusted through the hydrodynamic gap, including:

[0124] The shaft thrust disc 27 is arranged on both sides of the high-speed shaft gear 101 in the gearbox of the supercritical carbon dioxide compressor;

[0125] The shaft thrust disc 27 is tightly matched with the high-speed shaft gear 101, and the shaft thrust disc 27 is gap-matched with the low-speed shaft gear 111 to form a hydrodynamic gap;

[0126] The hydrodynamic effect generated by the two hydrodynamic gaps transmits the thrust of the high-speed shaft gear 101 to the low-speed shaft gear 111;

[0127] The counter-fitted thrust disc 29 and thrust bearing 28 are arranged on the low-speed shaft 11, and the thrust disc 29 and thrust bearing 28 balance the thrust of the low-speed shaft gear 111.

[0128] In this embodiment, the shaft thrust disc 27 is added on both sides of the high speed shaft gear 101, the fluid dynamic pressure gap is formed between the shaft thrust disc 27 and the low speed shaft gear 111 to ensure the gear can transfer thrust force, then the thrust disc 29 and thrust bearing 28 are arranged on the low speed shaft to balance the thrust force, so the compressor thrust force can be successfully balanced on the low speed shaft 11. The friction power consumption caused by the bearing thrust is proportional to the square of the rotational speed, so this method of transferring the thrust force to the low speed shaft for balancing can significantly improve the friction power consumption of the thrust bearing and thus improve the efficiency of the gearbox and the overall output power of the compressor unit. On the other hand, the thrust force is transferred to the low speed shaft 11, which can effectively reduce the number of thrust bearing arrangements, reduce the axial span and reduce the bearing oil supply, especially for the case where thrust bearings are arranged on multiple high speed shafts.

[0129] In an optional embodiment, a wedge-shaped surface is machined on the inner side wall of the shaft thrust disc 27 and / or the outer side wall of the low speed shaft gear 111. The wedge-shaped surface is the core key to form the fluid dynamic pressure effect. In this embodiment, the wedge-shaped surface is machined on the shaft thrust disc 27 on both sides of the high speed shaft gear 101, or on the low speed shaft gear 111, or on both the shaft thrust disc 27 and the low speed shaft gear 111.

[0130] Specifically, when the compressor finally generates positive thrust force, the gap 30 between the shaft thrust disc 27 and the left side of the low speed shaft gear 111 decreases, the fluid dynamic pressure effect increases to generate greater thrust force, the gap 31 between the shaft thrust disc 27 and the right side of the low speed shaft gear 111 increases, the fluid dynamic pressure effect weakens or even disappears, so the thrust force decreases or is insufficient to generate thrust force. Therefore, the thrust force is transferred through the relationship between the change of the gap between the shaft thrust disc 27 and the low speed shaft gear 111 and the force and reaction force, and the transferred thrust force is balanced in the positive direction and the negative direction by the thrust disc 29 and the thrust bearing 28 on the low speed shaft 11 (from left to right, the positive direction). When the compressor finally generates negative thrust force, the gap 31 between the shaft thrust disc 27 and the right side of the low speed shaft gear 111 decreases to generate stronger fluid dynamic pressure effect and thrust force, and the gap 30 between the shaft thrust disc 27 and the left side of the low speed shaft gear 111 increases to generate weaker fluid dynamic pressure effect and smaller thrust force. Through the relationship between the force and the reaction force of the shaft thrust disc 27 and the low speed shaft gear 111, the thrust force on the high speed shaft is transferred to the low speed shaft 11 through the shaft thrust disc 27 and the low speed shaft gear 111, and then to the low speed shaft thrust disc 29 and the thrust bearing 28 for thrust force balancing. If the number of high speed shafts exceeds one, this method of transferring thrust force is still applicable, and the above analysis can be carried out for a single shaft.

[0131] In an optional example, the ratio of the minimum oil film thickness to the maximum height of the wedge surface 32 is in the range of 0.8-1.0. When the ratio of the minimum oil film thickness to the maximum height of the wedge surface is too low, the hydrodynamic effect is increased, the lubricating oil pressure between the shaft thrust disc 27 and the low-speed shaft gear 111 is significantly increased, thereby increasing the thrust, but too high pressure will result in increased friction loss and poor economic effect; when the ratio of the minimum oil film thickness to the maximum height of the wedge surface is too high, the hydrodynamic effect is weakened, the lubricating oil pressure between the shaft thrust disc 27 and the low-speed shaft gear 111 is significantly reduced, thereby reducing the thrust, which may not meet the starting thrust requirement of the unit and the thrust requirement during wide load operation. Therefore, according to the use experience, it is more appropriate to select the ratio of the minimum oil film thickness to the maximum height of the wedge surface in the range of 0.8-1.0.

[0132] In an optional example, the axial gap (left gap 30 or right gap 31) between the shaft thrust disc 27 and the low-speed shaft gear 111 is designed to be 0.15-0.25mm.

[0133] In an optional example, in order to fully utilize the hydrodynamic effect of the wedge surface to be able to transmit greater thrust, the ratio of the radial height 33 of the wedge surface to the overlapped radial height 34 of the low-speed shaft gear is 0.4-0.8.

[0134] In an optional example, the ratio of the roughness of the wedge surface to the maximum height 32 of the wedge surface is ≤2%.

[0135] In an optional example, the shaft thrust disc 27 on both sides of the high-speed shaft gear 101 can freely move left and right with the high-speed shaft 10 to ensure that the right and left thrust transmission can be realized.

[0136] In an optional example, the axial gap between the shaft thrust disc 27 and the low-speed shaft gear 111 is 0.15-0.25mm.

[0137] In an optional example, the thrust disc 29 on the low-speed shaft 11 is machined integrally with the low-speed shaft 11, which can significantly improve the machining accuracy of the low-speed shaft 11, thereby reducing the assembly link, and further improving the shafting dynamic balance accuracy.

[0138] In an optional example, in order to facilitate later replacement and maintenance, the shaft thrust disc 27 and the high-speed shaft 10 are fixed in a sleeved manner.

[0139] The design method of the supercritical carbon dioxide compressor provided in the application aims at the problem that the sharp change of the properties of carbon dioxide in the near-critical region leads to inaccurate interpolation of the properties and difficulty in designing the carbon dioxide compressor, the near-critical carbon dioxide is equivalent to a property interval of an ideal working medium based on the fluid similarity theory to avoid the problem of the sharp change of the properties of the near-critical carbon dioxide, then the rated working condition design and the variable working condition design are performed according to the equivalent ideal working medium, and finally the performance curve of the equivalent ideal working medium is scaled back to the performance curve of the near-critical carbon dioxide according to the fluid similarity theory.

[0140] The design method of the supercritical carbon dioxide compressor provided in the application aims at the demand for simplifying the calculation workload of the off-design condition of the compressor and fast iteration response, the off-design aerodynamic performance is corrected based on the performance curve diagram under the design condition, the same speed is searched for the equal inlet flow rate condition on the performance curve diagram under the original design condition, then the total static pressure ratio is corrected based on the principle of constant enthalpy rise, and the total static isentropic efficiency searched is corrected to obtain a new off-design performance curve in the form of overall correction. The correction method obtains the entire off-design performance curve diagram through single off-design calculation simulation, greatly shortens the calculation time and calculation workload, and can meet the fast and high-frequency iteration demand of system operation or simulation.

[0141] The design method of the supercritical carbon dioxide compressor provided in the application aims at the requirement for safe operation of the gear box and the dry gas seal under the supercritical carbon dioxide zero leakage scenario, the relationship between the temperature and the pressure of the total gas flow upstream of the dry gas seal main gas flow and the isolation gas flow before the flow is branched is limited to ensure that the temperature of the leakage gas flow and the isolation gas flow at the outlet of the dry gas seal is close to the bearing oil inlet temperature, and the remaining pressure reduction structure except the pressure reduction valve is introduced into the isolation gas flow branch to meet the demand for step-by-step pressure reduction of the isolation gas flow to achieve the final large pressure drop and the non-frosting of the throat of the pressure reduction valve.

[0142] The design method of the supercritical carbon dioxide compressor provided in the application aims at the problem of low power loss and thrust balance of the compressor, thrust discs are added on both sides of the high-speed shaft gear of the gear box, a wedge-shaped surface is processed between the thrust disc and the low-speed shaft gear to form a hydrodynamic pressure gap to ensure that the gear can transmit thrust, then a thrust disc and a thrust bearing are arranged on the low-speed shaft to balance the thrust, so that the thrust balance of the compressor can be successfully performed on the low-speed rotating shaft, and the power loss of the thrust bearing is effectively reduced.

[0143] The detailed explanation of the above-mentioned embodiments is only for the purpose of explaining the present application so as to make it possible to better understand the present application, but these descriptions cannot be interpreted as a limitation on the present application for any reason, and in particular, various features described in different embodiments can be arbitrarily combined with each other to constitute other embodiments, and these features should be understood as being applicable to any one of the embodiments, not being limited to the described embodiments, except for the explicitly opposite description.

Claims

1. A method of designing a supercritical carbon dioxide gas compressor, wherein, The supercritical carbon dioxide compressor design method comprises: The supercritical carbon dioxide compressor performance curve is obtained based on the fluid similarity theory; The off-design performance of the supercritical carbon dioxide compressor is corrected based on the compressor performance curve; The dry gas seal temperature of the supercritical carbon dioxide compressor is controlled based on the corresponding relationship between temperature and pressure; A fluid dynamic pressure gap is arranged between the high-speed shaft gear and the low-speed shaft gear in the gear box of the supercritical carbon dioxide compressor, and the gear box thrust is adjusted through the fluid dynamic pressure gap.

2. The supercritical carbon dioxide gas compressor design method of claim 1, wherein, The supercritical carbon dioxide compressor performance curve is obtained based on the fluid similarity theory, comprising: Based on the fluid similarity theory, each property interval of supercritical carbon dioxide is equivalent to the property interval of an ideal working medium, the compressor rated operating condition design and off-design operating condition design are carried out according to the ideal working medium, and the performance curve of the ideal working medium is obtained, and the performance curve of the ideal working medium compressor is scaled back to the supercritical carbon dioxide compressor performance curve according to the fluid similarity theory.

3. The supercritical carbon dioxide gas compressor design method of claim 2, wherein, The performance indicators of the supercritical carbon dioxide include pressure ratio, mass flow and isentropic efficiency.

4. The supercritical carbon dioxide gas compressor design method of claim 3, wherein, The performance curve of the ideal working medium compressor is scaled back to the supercritical carbon dioxide compressor performance curve according to the fluid similarity theory, comprising: The pressure ratio of the supercritical carbon dioxide is converted according to the Prandtl similarity and the equal isentropic head coefficient; The mass flow of the supercritical carbon dioxide is converted according to the geometric similarity; The isentropic efficiency of the supercritical carbon dioxide is obtained according to the approximate empirical relationship.

5. The supercritical carbon dioxide gas compressor design method of claim 2, wherein, The fluid similarity theory includes Reynolds number similarity, Prandtl number similarity, geometric similarity and approximate empirical relationship.

6. The supercritical carbon dioxide gas compressor design method of claim 5, wherein, The Prandtl number similarity requires that the isentropic head coefficient and specific speed of the supercritical carbon dioxide compressor are equal.

7. The supercritical carbon dioxide gas compressor design method of claim 5, wherein, The geometric similarity is ensured by the equal flow coefficient, volume flow and speed.

8. The supercritical carbon dioxide gas compressor design method of claim 1, wherein, The off-design performance of the supercritical carbon dioxide compressor is corrected based on the compressor performance curve, comprising: The performance curve graph of the supercritical carbon dioxide compressor at the design operating condition is drawn; The inlet flow rate equal operating condition is found at the same speed on the performance curve graph at the design operating condition; The performance curve graph is corrected based on the inlet flow rate equal operating condition and the performance curve graph at the off-design operating condition is obtained.

9. The supercritical carbon dioxide gas compressor design method of claim 8, wherein, The performance curve graph at least includes total static pressure ratio performance curve graph and total static isentropic efficiency performance curve graph.

10. The supercritical carbon dioxide gas compressor design method of claim 9, wherein, The total static pressure ratio performance curve graph at the off-design operating condition is obtained by correcting the total static pressure ratio performance curve graph according to the principle that the enthalpy rise is constant at the same inlet flow rate.

11. The supercritical carbon dioxide gas compressor design method of claim 10, wherein, The surge line and the choke line are determined on the total static pressure ratio performance curve graph at the design operating condition according to the principle that the inlet flow rate remains unchanged at the same speed.

12. The supercritical carbon dioxide gas compressor design method of claim 9, wherein, The total static isentropic efficiency performance curve graph at the off-design operating condition is obtained by overall correcting the total static isentropic efficiency performance curve graph according to the total static isentropic efficiency overall correction coefficient.

13. The supercritical carbon dioxide gas compressor design method of claim 12, wherein, The calculation method of the total static isentropic efficiency overall correction coefficient comprises: The design flow rate and design speed corresponding to the maximum total static isentropic efficiency point at the rated speed in the total static isentropic efficiency performance curve graph at the design operating condition are obtained; According to the principle of equal inlet flow rate, a reference flow rate point under the partial working condition corresponding to the maximum overall static isentropic efficiency point under the design working condition is found, and the overall static isentropic efficiency at the reference flow rate point is calculated; The overall static isentropic efficiency overall correction coefficient is calculated according to the overall static isentropic efficiency at the reference flow rate point and the maximum overall static isentropic efficiency under the design working condition.

14. The supercritical carbon dioxide gas compressor design method of claim 13, wherein, According to the principle of equal inlet flow rate, a reference flow rate point under the partial working condition corresponding to the maximum overall static isentropic efficiency point under the rated rotating speed is found.

15. The supercritical carbon dioxide gas compressor design method of claim 13, wherein, The overall static isentropic efficiency at the reference flow rate point is calculated according to the inlet pressure and temperature under the partial working condition and the flow rate and conversion rotating speed of the reference flow rate point.

16. The supercritical carbon dioxide gas compressor design method of claim 15, wherein, According to the principle of constant rotating speed, the design rotating speed is converted into the conversion rotating speed of the reference flow rate point under the partial working condition.

17. The supercritical carbon dioxide gas compressor design method of claim 13, wherein, The overall static isentropic efficiency overall correction coefficient is the ratio of the overall static isentropic efficiency at the reference flow rate point to the maximum overall static isentropic efficiency under the design working condition.

18. The supercritical carbon dioxide gas compressor design method of claim 1, wherein, The dry gas seal temperature of the supercritical carbon dioxide compressor is controlled based on the corresponding relationship between temperature and pressure, comprising: A dry gas seal device for realizing dry gas seal is hung on a gear box of the supercritical carbon dioxide compressor, and an injection gas flow is introduced into the dry gas seal device; The relationship between the gas flow pressure and the temperature of the injection gas flow is as follows: T min = -0.0032P 3 + 0.0041P 2 + 6.0759P + 42.262 T max = 0.0118P 3 - 0.5304P 2 + 11.581P + 48.113 where T min is the minimum temperature of the incoming injection gas stream; T max is the maximum temperature of the incoming injection gas stream; P is the pressure of the incoming injection gas stream.

19. The supercritical carbon dioxide gas compressor design method of claim 18, wherein, The gas flow pressure of the injection gas flow is applicable to the range of 6 MPa-20 MPa.

20. The supercritical carbon dioxide gas compressor design method of claim 18, wherein, After the injection gas flow is introduced into the dry gas seal device, the injection gas flow is divided into a main gas flow and an isolation gas flow.

21. The supercritical carbon dioxide gas compressor design method of claim 20, wherein, A resistance, a pressure reducing valve and a throttle hole are sequentially arranged along the flow direction of the isolation gas flow, and the isolation gas flow is gradually depressurized through the resistance, the pressure reducing valve and the throttle hole.

22. The supercritical carbon dioxide gas compressor design method of claim 21, wherein, The pressure drop distribution principle of the isolation gas flow is that the lowest isentropic expansion temperature at the throat of the pressure reducing valve is higher than zero Celsius.

23. The supercritical carbon dioxide compressor design method of claim 1, wherein, Axial thrust discs are respectively arranged on both sides of a high-speed shaft gear of a gear box of the supercritical carbon dioxide compressor; The axial thrust discs are tightly matched with the high-speed shaft gear, and the axial thrust discs are gap matched with a low-speed shaft gear and form hydrodynamic pressure gaps; The fluid dynamic pressure effect generated by the two hydrodynamic pressure gaps is used to transmit the thrust of the high-speed shaft gear to the low-speed shaft gear; A counter thrust disc and a counter thrust bearing are arranged on the low-speed shaft in a position matched manner, and the low-speed shaft gear is thrust balanced through the counter thrust disc and the counter thrust bearing. A wedge surface is processed on the inner side wall of the axial thrust disc and / or the outer side wall of the low-speed shaft gear.

24. The supercritical carbon dioxide gas compressor design method of claim 23, wherein, The ratio of the minimum oil film thickness in the gear box to the maximum height of the wedge surface ranges from 0.8 to 1.

0.

25. The method of designing a supercritical carbon dioxide gas compressor as recited in claim 24, wherein, The axial gap between the axial thrust disc and the low-speed shaft gear is 0.15-0.25 mm.

26. The supercritical carbon dioxide gas compressor design method of claim 23, wherein, ​

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