A centrifugal compressor exhaust waste heat driven organic rankine cycle power generation system

Abstract

The application discloses a centrifugal compressor exhaust waste heat driven organic Rankine cycle power generation system, comprising: an adaptive variable structure waste heat collection module, which adjusts the spiral angle of the fin through a stepping motor, matches the exhaust temperature fluctuation, and realizes dynamic storage and release of waste heat by setting a double medium heat exchange loop; a step expansion power generation module, which adopts a two-stage expander in series and a pressure matcher, and configures a working medium shunt valve to dynamically adjust the working medium proportion; an intelligent coupled power generation and electric energy management module, which integrates a magnetic resistance switching type permanent magnet synchronous generator and a virtual synchronous generator technology, and configures a dynamic reactive power compensation device; and a multi-parameter collaborative control module, which optimizes system parameters based on a model prediction control algorithm, and introduces entropy production analysis to monitor irreversible loss. The application optimizes the heat exchange process through adaptive structure, widens the working condition adaptation range through step expansion, reduces irreversible loss through collaborative control, prolongs the maintenance cycle through self-repair system, and realizes deep utilization and efficient conversion of the centrifugal compressor waste heat.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of renewable energy utilization, and particularly relates to an organic Rankine cycle power generation system driven by exhaust waste heat of a centrifugal compressor. BACKGROUND

[0002] In modern industrial production, centrifugal compressors, as core power equipment, are widely used in petroleum chemical industry, metallurgy, power and other fields. The high-temperature gas discharged during the operation of the centrifugal compressor usually has a temperature of 150-300 DEG C and carries a large amount of waste heat. If the waste heat is not effectively utilized, not only energy is wasted, but also the environmental thermal load is increased. The organic Rankine cycle (ORC) power generation system becomes a common technical means for recovering the exhaust waste heat of the centrifugal compressor because it can adapt to the characteristics of the medium and low temperature heat source. However, the existing waste heat power generation system has many problems to be solved in actual application. The conventional waste heat collection device usually adopts a fixed structure finned heat exchanger, and the heat transfer efficiency thereof depends on stable working conditions. When the centrifugal compressor load fluctuates, the exhaust flow rate and temperature change, and the fixed fin is difficult to dynamically adjust the heat transfer area and flow field distribution, so that the heat transfer efficiency is significantly reduced. At the same time, during the long-term operation, impurities in the exhaust gas are easily attached to the surface of the fin to form ash and scale, which further increases the heat transfer resistance and reduces the heat transfer performance. In the energy conversion link, the single-stage expander has a fixed expansion ratio range and cannot be flexibly adjusted according to the changes of the exhaust temperature and pressure. When the actual working condition deviates from the design parameter, the energy conversion efficiency of the expander is greatly reduced, and it is difficult to realize the efficient utilization of the waste heat. In terms of system integration and control, the compatibility of the existing power generation system with the power grid is poor. The conventional generator has unstable operating efficiency under variable speed conditions, and the efficiency is greatly reduced at low load. In addition, the conventional generator lacks the ability to simulate the inertia of the power grid, and when connected to the microgrid, it is easy to cause frequency oscillation and affect the stability of the power grid. In terms of working medium management, the organic working medium will decompose to produce acidic substances and other impurities during long-term circulation in a high-temperature environment. The conventional purification method not only has low efficiency, but also needs to be regularly shut down for processing, resulting in poor system operation continuity and high maintenance cost. In addition, the conventional PID control strategy cannot meet the control requirements of the organic Rankine cycle system with multiple variables and strong coupling. The response speed to the waste heat transient is slow, the steady-state error is large, and the overall power generation efficiency is difficult to improve. Therefore, it is urgent to develop a new centrifugal compressor exhaust waste heat power generation system to overcome the shortcomings of the prior art. SUMMARY

[0003] The present application provides a centrifugal compressor exhaust waste heat driven organic Rankine cycle power generation system to solve the above-mentioned problems in the prior art.

[0004] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0005] A centrifugal compressor exhaust waste heat driven organic Rankine cycle power generation system, comprising the following modules:

[0006] Self-adaptive variable structure waste heat collection module: arranged in the centrifugal compressor exhaust pipeline, containing adjustable spiral angle finned tube heat exchanger, through the step motor drive fin rotation, real-time adjustment of spiral angle, realize the reynolds number Re flow state optimization; Set up double medium heat exchange loop, the main loop flow organic working medium, the secondary loop filled with phase change energy storage material, through Q store =m·ΔH fus Realize the dynamic storage and release of waste heat, compensate the energy supply when the load fluctuates, wherein m is the mass of the phase change material, ΔH fus Is the latent heat of fusion;

[0007] Step expansion power generation module: adopt two-stage expansion machine series structure, the first stage expansion machine is radial flow into type, the secondary is axial type, through the pressure matching device connection; Configure the working medium shunt valve, according to the exhaust temperature dynamic adjustment of the working medium proportion into two-stage expansion machine;

[0008] Intelligent coupling power generation and power management module: generator adopts magnetic resistance switching type permanent magnet synchronous generator, through the stator winding switching to realize wide speed range efficient power generation; Power management unit integrates virtual synchronous generator VSG technology, through inertia control algorithm Simulate the characteristics of synchronous generator, wherein J VSG Is the virtual inertia, k J Is the inertia coefficient, ω grid Is the grid angular frequency; Configure dynamic reactive power compensation device, according to the grid voltage fluctuation real-time adjustment of reactive power output, adjustment algorithm is: Q comp =k Q ·(V grid -V ref ), wherein Q comp Is the compensation reactive power, k Q Is the compensation coefficient, V grid , V ref Is the grid voltage and reference voltage respectively;

[0009] Multi-parameter collaborative control module: based on model predictive control MPC algorithm, establish multivariable prediction model containing waste heat collection, organic Rankine cycle, power generation system, through the rolling optimization solution Realize the global optimal control of system, wherein J is the objective function, N p Is the prediction time domain, y is the system output, r is the reference trajectory, Q, R is the weight matrix; Introduce entropy analysis, real-time monitoring of system irreversible loss, automatic adjustment of key parameters;

[0010] Self-repairing working fluid cycle module: integrate nanometer catalyst bed in working fluid circuit, load noble metal active component, through algorithm formula: Catalytic decomposition of working fluid pyrolysis products, where r is the reaction rate, k is the reaction constant, C impurity is the impurity concentration, E a is the activation energy, R is the gas constant, and T is the temperature; Set working fluid quality online detection unit, real-time monitoring by dielectric constant sensor, automatically trigger purification process when decomposition product concentration exceeds threshold.

[0011] Further, in the self-adaptive variable structure waste heat recovery module, the fin surface is provided with a micro-channel structure, the groove depth h, the groove width w, through the algorithm formula: Enhanced heat transfer, where Nu is the Nusselt number, and d is the pipe diameter; The phase change energy storage material adopts graphene modified composite salt, through the algorithm formula: Optimize the heat response speed, where λ eff is the effective thermal conductivity, λ m , λ p are the matrix and particle thermal conductivities, and φ is the particle volume fraction.

[0012] Further, in the stepped expansion power generation module, the first-stage expander impeller adopts a three-dimensional flow channel design, the blade outlet angle β, through the algorithm formula: Optimize the energy conversion efficiency, where ψ is the head coefficient, H t is the theoretical head, u is the impeller peripheral velocity, and φ is the flow coefficient; The secondary expander adopts an adjustable guide vane structure, the guide vane installation angle α, satisfies η pol = η0·(1-k α ·|α-α0|), where η pol is the variable efficiency, η0 is the design efficiency, k α is the efficiency correction coefficient, and α0 is the optimal installation angle.

[0013] Further, in the intelligent coupled power generation and power management module, the stator winding of the reluctance switching permanent magnet synchronous generator adopts a star-delta switchable structure, through the algorithm formula Achieve impedance matching in a wide load range, where Z Y , Z Δ are the star and delta connection impedances respectively; The primary frequency modulation coefficient formula of the virtual synchronous generator is: Where f rated , f min are the rated and minimum frequencies, P max , P min are the maximum and minimum active powers.

[0014] Further, in the multi-parameter coordinated control module, the weight matrix of the model predictive control algorithm is Q = diag(q1, q2, q3) and R = diag(r1, r2), which are adjusted online by particle swarm optimization (PSO) algorithm, satisfying where N is the number of iterations, J target is the objective function value; in the optimization strategy based on entropy production analysis, when S gen exceeds the reference value by 15%, the system parameter reconstruction is automatically triggered to adjust the working fluid flow.

[0015] Further, in the self-repairing working fluid cycle module, the nano-catalyst bed adopts a honeycomb structure, and the catalytic effect is optimized by the formula where η cata is the catalytic efficiency, k is the reaction rate constant, a is the specific surface area, D eff is the effective diffusion coefficient, and L is the bed thickness; the dielectric constant sensor of the working fluid quality online detection unit adopts a coaxial cylindrical structure, and the working fluid state is accurately monitored by the algorithm formula: where C is the capacitance value, L is the electrode length, and a and b are the inner and outer electrode radii.

[0016] Further, in the self-adaptive variable structure waste heat recovery module, a dynamic flow distribution valve is arranged in the double-medium heat exchange circuit, and the flow ratio is adjusted according to where m main , m phase are the flow rates of the main circuit and the phase change circuit, T pc is the melting point of the phase change material, and T amb is the environmental temperature; the micro-channel structure is deposited with a super-hydrophobic coating, and the contact angle θ is greater than or equal to 150°.

[0017] Further, in the stepwise expansion power generation module, the pressure matcher adopts a scaled nozzle structure, and the throat diameter where m mix is the mixed flow rate, ρ t and v t are the density and flow rate at the throat, respectively, and the pressure matching efficiency is optimized by the formula: where P1 and P2 are the inlet and outlet pressures, gamma is the specific heat ratio, and M1 is the inlet Mach number; the bearing of the two-stage expander adopts a magnetohydrodynamic sealing technology, and zero leakage is achieved by the formula F = μ0MH·A, where F is the sealing force, μ0 is the vacuum permeability, M is the magnetization, H is the magnetic field strength, and A is the sealing area.

[0018] Further, in the intelligent coupled power generation and power management module, the dynamic reactive power compensation device adopts a modular multilevel converter (MMC), and the sub-module capacitor where Qmax For maximum reactive capacity, f is the grid frequency, V dc For DC side voltage, through formula Control output voltage, wherein m is the modulation ratio, V ac For AC side voltage; power quality monitoring unit integrated harmonic source positioning function, based on the directional power method formula: When P h For positive time to determine that the harmonic source is located downstream of the measurement point, wherein P h For h harmonic power, V hi , I hi For h harmonic voltage and current, φ hi For phase difference.

[0019] Further, in the multi-parameter cooperative control module, the prediction time domain N p According to the dynamic characteristics of the system, the adjustment is satisfied Where N p0 For reference time domain, k p For adjustment coefficient, τ sys For system time constant, τ sam For sampling period; in the system reconstruction strategy based on entropy production analysis, the economic optimization target algorithm is introduced: Where C is the total cost, c i For each component entropy production cost coefficient, ΔS gen,i For entropy change, c energy For energy cost, ΔW is the change of power generation.

[0020] Compared with the prior art, the beneficial effects of the present application are:

[0021] The centrifugal compressor exhaust waste heat driven organic Rankine cycle power generation system provided by the present application has obvious advantages in waste heat recovery efficiency, system stability, power generation performance and operation and maintenance through a series of innovative design and technical improvement.

[0022] In the waste heat collection link, the self-adaptive variable structure waste heat collection module can adjust the spiral angle of the fin in real time according to the change of exhaust temperature and flow, optimize the flow field distribution, and significantly improve the heat exchange efficiency. The design of the double-medium heat exchange circuit, combined with phase change energy storage materials, effectively buffers the influence of heat source fluctuation, ensures efficient recovery of waste heat under different working conditions. At the same time, the application of micro-channel and super-hydrophobic coating technology suppresses the scaling phenomenon, reduces the maintenance frequency, and prolongs the service life of the equipment.

[0023] The stepwise expansion power generation module adopts two-stage expansion machine series connection and pressure matching technology, widens the adaptive range of expansion ratio, and realizes deep utilization of waste heat energy. Whether in high load or low load condition, the module can maintain high energy conversion efficiency, and compared with the traditional single-stage expansion system, greatly improves the power generation efficiency and part load performance.

[0024] In the intelligent coupling power generation and electric energy management module, the reluctance switching permanent magnet synchronous generator realizes efficient power generation in a wide speed range, the virtual synchronous generator technology gives the system good grid adaptability, can effectively suppress frequency fluctuation and improve power quality. The dynamic reactive power compensation device can adjust the reactive power output in real time, reduce the harmonic distortion rate, and ensure stable access to the grid.

[0025] The multi-parameter collaborative control module based on model predictive control algorithm and entropy production analysis can quickly respond to working condition changes, accurately adjust system parameters, effectively reduce irreversible loss, and improve overall energy efficiency of the system. The self-repairing working fluid circulation module uses nano catalysts and online detection technology to purify the working fluid in real time, inhibit working fluid decomposition, extend purification cycle, and reduce maintenance cost.

[0026] Overall, the technical scheme of the present application significantly improves the recovery rate of exhaust waste heat of the centrifugal compressor, improves the stability and economy of the power generation system, reduces the operation and maintenance cost, and has wide application prospect and great popularization value in the field of industrial waste heat recovery. BRIEF DESCRIPTION OF DRAWINGS

[0027] Fig. 1 A schematic block diagram of an organic Rankine cycle power generation system driven by exhaust waste heat of a centrifugal compressor is provided for the present application;

[0028] Fig. 2 A system energy efficiency comparison column chart;

[0029] Fig. 3 A control strategy optimization comparison chart. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0031] In the description of the present application, it needs to be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0032] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited. In addition, the terms "mounting", "connecting", "connecting" should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances, and the present application will be further described in detail below with reference to the drawings.

[0033] Referring to Figs. 1 to 3 An organic Rankine cycle power generation system driven by exhaust heat of a centrifugal compressor, comprising the following modules:

[0034] Self-adaptive variable structure waste heat collection module: arranged in the exhaust pipe of the centrifugal compressor, containing finned tube heat exchanger with adjustable spiral angle, rotating the fin through the stepping motor, adjusting the spiral angle in real time, realizing the optimization of Reynolds number Re flow state; setting a double-medium heat exchange loop, the main loop circulating organic working medium, the auxiliary loop filled with phase change energy storage material, through Q store = m·ΔH fus Realize dynamic storage and release of waste heat, compensate for energy supply during load fluctuation, where m is the mass of the phase change material, ΔH fus is the latent heat of fusion;

[0035] Step expansion power generation module: adopting a two-stage expansion machine series structure, the first stage expansion machine is a radial inflow type, and the second stage is an axial type, connected through a pressure matcher; configure a working medium shunt valve, dynamically adjust the working medium ratio entering the two-stage expansion machine according to the exhaust temperature;

[0036] Intelligent Coupled Generation and Power Management Module: The generator adopts a reluctance-switching permanent magnet synchronous generator, which achieves high-efficiency power generation over a wide speed range through stator winding switching; the power management unit integrates virtual synchronous generation (VSG) technology, using inertia control algorithms. Simulate synchronous generator characteristics, where J VSG For virtual inertia, k J ω is the inertia coefficient. grid The grid angular frequency is used; a dynamic reactive power compensation device is configured to adjust the reactive power output in real time according to grid voltage fluctuations. The adjustment algorithm is: Q comp =k Q ·(V grid -V ref ), where Q comp To compensate for reactive power, k Q V is the compensation coefficient. grid V ref These are the mains voltage and the reference voltage, respectively.

[0037] Multi-parameter collaborative control module: Based on the Model Predictive Control (MPC) algorithm, a multivariate predictive model is established, including waste heat harvesting, organic Rankine cycle, and power generation system, and solved through rolling optimization. Achieve global optimal control of the system, where J is the objective function and N is the target function. p For the prediction time domain, y is the system output, r is the reference trajectory, and Q and R are weight matrices; entropy production analysis is introduced to monitor irreversible system losses in real time and automatically adjust key parameters.

[0038] Self-healing working fluid circulation module: Integrates a nano-catalyst bed in the working fluid loop, loaded with noble metal active components, through an algorithmic formula: Catalytic decomposition of the working fluid pyrolysis products, where r is the reaction rate, k is the reaction constant, and C impurity E represents the impurity concentration. a The activation energy is R, the gas constant is T, and the temperature is T. An online detection unit for the working fluid quality is set up, which monitors the fluid in real time through a dielectric constant sensor. When the concentration of decomposition products exceeds the threshold, the purification process is automatically triggered.

[0039] In this invention, the adaptive variable structure waste heat collection module has a microchannel structure on the fin surface, with a channel depth of h and a channel width of w, determined by the following algorithm formula: Enhanced heat transfer, where Nu is the Nusselt number and d is the pipe diameter; the phase change energy storage material uses graphene-modified composite salt, obtained through the algorithm formula: Optimize thermal response speed, where λ eff For effective thermal conductivity, λ m , λ p φ represents the thermal conductivity of the matrix and the particles, respectively, and φ is the volume fraction of the particles.

[0040] In this invention, the first-stage expander impeller of the cascade expansion power generation module adopts a three-dimensional flow channel design, and the blade outlet angle β is determined by the following algorithm formula: Optimize energy conversion efficiency, where ψ is the head coefficient and H t The theoretical head is given by u, the impeller circumferential velocity is given by φ, and the flow coefficient is given by φ. The secondary expander adopts an adjustable guide vane structure with a guide vane installation angle α that satisfies η. pol =η0·(1-k α ·|α-α0|), where η pol For variable efficiency, η0 is the design efficiency, and k α α0 is the efficiency correction factor and the optimal installation angle.

[0041] In this invention, the stator winding of the reluctance-switching permanent magnet synchronous generator in the intelligent coupled power generation and power management module adopts a star-delta switchable structure, which is achieved through algorithm formulas. To achieve impedance matching over a wide load range, where Z Y Z Δ The impedances for star and delta connections are respectively; the formula for the primary frequency regulation coefficient of the virtual synchronous generator is: Where f rated f min For the rated and minimum frequencies, P max P min The maximum and minimum active power.

[0042] In this invention, the weight matrices of the model predictive control algorithm in the multi-parameter collaborative control module are: Q = diag(q1,q2,q3) and R = diag(r1,r2), which are tuned online using the particle swarm optimization (PSO) algorithm to satisfy... Where N is the number of iterations, J target The objective function value; in the optimization strategy based on entropy production analysis, when S gen When the value exceeds the baseline by 15%, the system parameters are automatically reconfigured to adjust the working fluid flow rate.

[0043] In this invention, the self-healing working fluid circulation module employs a honeycomb structure in its nanocatalyst bed, which is achieved through a formula... Optimize catalytic effect, where η cata For catalytic efficiency, k is the reaction rate constant, a is the specific surface area, and D is the specific surface area. eff The effective diffusion coefficient is L, and the bed thickness is L. The dielectric constant sensor of the online working fluid quality detection unit adopts a coaxial cylindrical structure, and is determined by the following algorithm formula: To achieve accurate monitoring of the working fluid state, where C is the capacitance value, L is the electrode length, and a and b are the inner and outer electrode radii.

[0044] In the application, the double medium heat exchange circuit in the adaptive variable structure waste heat collection module is provided with a dynamic flow distribution valve, and the flow ratio is adjusted according to m main , m phase are the flow rates of the main circuit and the phase change circuit respectively, T pc is the melting point of the phase change material, and T amb is the ambient temperature; an ultrahydrophobic coating is deposited on the surface of the microchannel structure, and the contact angle θ is greater than or equal to 150°.

[0045] In the application, the pressure matching device in the step expansion power generation module adopts a converging-diverging nozzle structure, and the throat diameter is m mix is the mixed flow rate, ρ t and v t are the density and flow rate at the throat respectively, and the pressure matching efficiency is optimized through the formula: P1, P2 are the inlet and outlet pressures, gamma is the specific heat ratio, and M1 is the inlet Mach number; the bearings of the two-stage expander adopt a magnetic fluid sealing technology, and zero leakage is achieved through the formula: F = μ0MH·A, wherein F is the sealing force, μ0 is the vacuum permeability, M is the magnetization, H is the magnetic field strength, and A is the sealing area.

[0046] In the application, the intelligent coupling power generation and electric energy management module adopts a modular multilevel converter (MMC), and the sub-module capacitor Q max is the maximum reactive capacity, f is the grid frequency, V dc is the DC side voltage, and the output voltage is controlled through the formula V ac is the AC side voltage; the power quality monitoring unit integrates a harmonic source positioning function, and is based on the formula of the directional power method: When P h is positive, it is determined that the harmonic source is located downstream of the measurement point, wherein P h is the hth harmonic power, V hi and I hi are the hth harmonic voltage and current, and φ hi is the phase difference.

[0047] In the application, the model predictive control algorithm in the multi-parameter cooperative control module has a prediction time domain N p which is adaptively adjusted according to the dynamic characteristics of the system, and satisfies N p0 is the reference time domain, k p is the adjustment coefficient, and τ sys is the time constant of the system.sam is the sampling period; in the system reconstruction strategy based on entropy generation analysis, an economic optimization target algorithm is introduced: where C is the total cost, c i is the entropy generation cost coefficient of each component, ΔS gen,i is the entropy generation change, c energy is the energy cost, and ΔW is the power generation change.

[0048] The centrifugal compressor exhaust waste heat driven organic Rankine cycle power generation system of the application adopts integrated design of waste heat collection, energy conversion, power generation control and working medium management. The system mainly comprises a self-adaptive variable structure waste heat collection module, a cascade expansion power generation module, an intelligent coupled power generation and electric energy management module, a multi-parameter collaborative control module and a self-repairing working medium circulation module. Through data interaction and collaborative control, the modules realize efficient recovery and power generation of the centrifugal compressor exhaust waste heat.

[0049] The overall working process of the system is as follows: the high-temperature exhaust gas (150-300℃) discharged by the centrifugal compressor enters the self-adaptive variable structure waste heat collection module, and through the adjustable spiral angle finned tube and the double medium heat exchange circuit, heat is transferred to the organic working medium (such as R245fa) and the phase change energy storage material; the organic working medium is heated and evaporated to enter the cascade expansion power generation module, and the working medium drives the generator to generate power through two-stage expanders; the electric energy is processed through the intelligent coupled power generation and electric energy management module and then connected to the power grid or directly supplied with energy; the multi-parameter collaborative control module monitors the system state in real time, and optimizes the operating parameters based on the model predictive control algorithm; the self-repairing working medium circulation module continuously purifies the working medium to ensure long-term stable operation of the system.

[0050] The self-adaptive variable structure waste heat collection module is composed of an adjustable spiral angle finned tube heat exchanger, a double medium heat exchange circuit, a stepping motor driving mechanism and temperature and pressure sensors. The finned tube is made of stainless steel (such as 316L), with a tube diameter of 25mm, a wall thickness of 2mm, a fin height of 15mm, a fin spacing of 4mm, and a spiral angle θ that can be adjusted within the range of 5°-45°. The double medium heat exchange circuit includes a main circuit (organic working medium R245fa) and a secondary circuit (graphene modified composite salt phase change material with a melting point of 58℃).

[0051] The spiral angle dynamic adjustment formula is: θ=θ0+k·ΔT_exhaust;

[0052] Where θ0 is the initial spiral angle (20°), k is the adjustment coefficient (0.5° / ℃), and ΔT_exhaust is the exhaust temperature fluctuation value. When the exhaust temperature rises from 200℃ to 250℃, the spiral angle is automatically adjusted from 20° to 45°, so that the Re number is maintained in the high-efficiency heat exchange interval of 5000-8000.

[0053] Optimization formula of thermal conductivity of phase change energy storage material: λ_eff = λ_m·(1+3φ(λ_p-λ_m) / (λ_p+2λ_m))

[0054] Wherein, λ_m is the thermal conductivity of the matrix material (0.5 W / (m·K)), λ_p is the thermal conductivity of graphene particles (5000 W / (m·K)), and φ is the volume fraction of particles (5%). It is calculated that the thermal conductivity of the composite salt is improved to 4.2 W / (m·K), and the thermal response speed is increased by 30%.

[0055] Micro-channel enhanced heat transfer formula: Nu = 0.23Re^0.65Pr^0.4(1+h / d)^0.2

[0056] Wherein, h is the groove depth (0.3 mm), and d is the pipe diameter (25 mm). Compared with the light pipe, the micro-channel structure makes the Nu number increase by 25%, and the heat transfer coefficient increases from 800 W / (m 2 ·K) to 1000 W / (m 2 ·K).

[0057] Implementation case and effect verification:

[0058] The module is applied to the exhaust system of a centrifugal compressor in a certain chemical enterprise, and the measured data are shown in the following table:

[0059]

[0060] From the data in the table, it can be seen that the self-adaptive variable structure design of the application significantly improves the waste heat recovery efficiency and system response speed. The adjustable spiral angle enables the fins to maintain the best heat transfer state under different working conditions, and the combination of micro-channels and super-hydrophobic coating suppresses the fouling phenomenon and prolongs the equipment maintenance period. The phase change energy storage material effectively compensates the energy supply when the load fluctuates, so that the system can still operate stably within the range of ±30℃ of the exhaust temperature fluctuation.

[0061] The stepped expansion power generation module is composed of a radial inflow first-stage expander, an axial second-stage expander, a pressure matcher, and a working medium shunt valve. The impeller of the first-stage expander adopts a three-dimensional flow channel design, and the blade outlet angle β is 20°. The second-stage expander is equipped with adjustable guide vanes, and the installation angle α can be adjusted within the range of 25°-65°. The pressure matcher connects the two-stage expanders to realize the optimal control of the intermediate pressure.

[0062] Pressure matching formula: P_int = √(P_high·P_low)

[0063] In some embodiments, the high-pressure side pressure P_high = 2.5 MPa, the low-pressure side pressure P_low = 0.3 MPa, and the intermediate pressure P_int = 0.87 MPa is calculated. In actual operation, the intermediate pressure is accurately controlled in the range of 0.85-0.9 MPa by the pressure matcher to maximize the system efficiency.

[0064] The working medium split ratio formula is: a = (T_exhaust-T_ref) / (T_max-T_ref)

[0065] Wherein, T_exhaust is the exhaust temperature, T_ref is the reference temperature (180℃), and T_max is the design maximum temperature (300℃). When the exhaust temperature is 240℃, a = (240-180) / (300-180) = 0.5, that is, 50% of the working medium enters the primary expander, and 50% enters the secondary expander.

[0066] The secondary expander efficiency formula is: η_pol = η_0·(1-k_α·|α-α_0|)

[0067] Wherein, η_0 is the design efficiency (85%), k_α is the efficiency correction coefficient (0.003 / °), and a_0 is the optimal installation angle (45°). When the guide vane installation angle a = 55°, η_pol = 85% × (1-0.003 × |55-45|) = 82.45%;

[0068] Embodiment and effect verification:

[0069] In a steel enterprise application case, compared with single-stage expansion and the cascade expansion system of the present application, the data are shown in the following table:

[0070]

[0071] The cascade expansion design significantly improves the system efficiency and the adaptation range. The intermediate pressure is optimized by the pressure matcher to reduce the irreversible loss in the expansion process. The adjustable guide vane structure enables the secondary expander to maintain high efficiency under variable working conditions, and the performance improvement under partial load is particularly obvious. The magnetic fluid sealing technology realizes zero leakage, prolongs the service life of the equipment, and reduces the maintenance cost.

[0072] The intelligent coupled power generation and electric energy management module is composed of a magnetic resistance switching type permanent magnet synchronous generator, a virtual synchronous generator control unit, a dynamic reactive power compensation device, and an electric energy quality monitoring unit. The generator stator winding can be switched between star and delta connection, the virtual synchronous generator unit simulates the inertia and damping characteristics of the synchronous generator through software algorithm, and the dynamic reactive power compensation device adopts MMC topology structure;

[0073] The winding impedance matching formula is: Z_Y = 1 / 3Z_Δ

[0074] When the generator is running at low load, switch to star connection (Z_Y), reduce impedance to 1 / 3 of delta connection (Z_Δ), reduce copper loss. Test shows that at 30% load, star connection efficiency is improved by 2.3% compared with delta connection.

[0075] Virtual synchronous generator inertia formula: J_VSG=k_J·W_turbine / ω_grid 2

[0076] Where k_J is the inertia coefficient (0.5), W_turbine is the output power of the expander (kW), and ω_grid is the grid angular frequency (rad / s). When the grid frequency fluctuates, by dynamically adjusting J_VSG, the system inertia response time is shortened to 1 / 3 of the traditional system.

[0077] MMC sub-module capacitance formula: C=Q_max / (2fV_dc 2 )

[0078] In some embodiments, Q_max=100kvar, f=50Hz, V_dc=1000V, and C=2000μF is calculated. A 2200μF capacitor is actually selected to ensure stable operation of the device under rated conditions;

[0079] Implementation cases and effect verification:

[0080] In an industrial park microgrid, the module is applied to compare with the traditional power generation system, and the data is shown in the following table:

[0081]

[0082]

[0083] The multi-parameter collaborative control module is based on PLC controller and industrial computer, including data acquisition unit, model predictive control algorithm unit, entropy production analysis unit and parameter optimization unit. The system collects more than 20 parameters such as temperature, pressure and flow, realizes global optimization control through MPC algorithm, and identifies the low-efficiency link of the system based on entropy production analysis;

[0084] MPC objective function: min J=∑(k=0→N_p)‖y(k+1|k)-r(k+1)‖ 2

[0085] _Q+‖u(k)‖ 2 _R

[0086] Where, N_p is the prediction horizon (10 steps), y is the system output, r is the reference trajectory, Q is the state weight matrix (diag(10, 5, 2)), and R is the control weight matrix (diag(0.5, 0.3)). By optimizing the Q and R matrices online through the PSO algorithm, the system response speed is improved by 20%.

[0087] Entropy production calculation formula: S_gen = ∑Q_i / T_i - Q_o / T_o

[0088] Under certain working conditions, the waste heat collection module Q_i = 500kW, T_i = 250℃ (523K), Q_o = 420kW, T_o = 80℃ (353K), and the calculation result is S_gen = 500 / 523 - 420 / 353 = -0.32kW / K. When S_gen exceeds the reference value by 15%, the system automatically adjusts the working fluid flow.

[0089] Working fluid flow adjustment formula: m_ref = m_0·√(S_gen,base / S_gen)

[0090] Assuming that the reference entropy production S_gen,base = 0.25kW / K, the current S_gen = 0.3kW / K, and the initial flow m_0 = 5kg / s, then the adjusted flow m_ref = 5·√(0.25 / 0.3) = 4.56kg / s;

[0091] Implementation case and effect verification:

[0092] In an application case in a pharmaceutical factory, the traditional PID control and the MPC collaborative control of the present application were compared, and the data are shown in the following table:

[0093]

[0094] Multi-parameter collaborative control significantly improves the dynamic performance and operating efficiency of the system. The MPC algorithm predicts future system behavior and adjusts control variables in advance, effectively suppressing parameter fluctuations. The optimization strategy based on entropy production analysis enables the system to always operate in a thermodynamically optimal state, reducing irreversible losses. Actual operating data show that under complex working conditions, the control strategy of the present application can still maintain high-efficiency and stable operation of the system.

[0095] The self-repairing working fluid circulation module is composed of a nano-catalyst bed, an online working fluid quality detection unit, a purification circuit, and an intelligent switching valve. The catalyst bed adopts a honeycomb structure with a pore density of 300cpsi and loaded with Pt / Pd active components (particle size 10nm). The online detection unit monitors the working fluid state in real time through a coaxial cylindrical dielectric constant sensor;

[0096] Catalytic efficiency formula: η_cata = 1 - 1 / tanh(mL), where m = √(ka / D_eff), k is the reaction rate constant (0.05 s -1 ), a is the specific surface area (1500 m 2 / m 3 ), D_eff is the effective diffusion coefficient (1 x 10 -5 m 2 / s), L is the bed thickness (0.2 m). Calculation: η_cata = 92.3%.

[0097] Dielectric constant and decomposition product concentration relationship: ε = ε_0·(1 + k_ε·C_decomp), where ε_0 is the dielectric constant of pure working medium (9.8), k_ε is the correlation coefficient (0.05 / %) When ε = 10.2 is detected, C_decomp = (10.2 / 9.8-1) / 0.05 = 8.16%, which exceeds the threshold (5%), triggering the purification process.

[0098] Capacitance calculation formula: C = 2πεL / ln(b / a)

[0099] Sensor inner and outer electrode radius a = 5 mm, b = 10 mm, L = 100 mm, when ε = 9.8, C = 2πx8.85x10-12x9.8x0.1 / ln(2) = 8.5 pF. Actual measurement accuracy is ±0.05 pF, corresponding to concentration detection accuracy ±0.5%;

[0100] Implementation case and effect verification:

[0101] In a certain thermal power plant continuous operation for 12 months test, compared with the traditional system and the self-repairing system of the invention, the data are shown in the following table:

[0102]

[0103] The self-repairing working medium cycle module effectively prolongs the service life of the working medium and reduces the system maintenance cost. The nano-catalyst bed layer controls the working medium decomposition product concentration within a safe range through high-efficiency catalytic decomposition. The online detection unit monitors the working medium state in real time, realizing intelligent triggering of the purification process. Actual operation shows that the module makes the system maintain high efficiency and stability in long-term operation, greatly reducing the working medium replacement and equipment maintenance frequency.

[0104] System overall performance verification:

[0105] In a comprehensive application case of a certain large petrochemical enterprise, the system of the invention is compared with the traditional waste heat recovery system, and the data of continuous operation for 6 months are shown in the following table:

[0106]

[0107] The system of the present application is significantly superior to the traditional system in terms of waste heat recovery efficiency, power generation efficiency, stability, etc. The combination of the self-adaptive variable structure waste heat collection module and the cascade expansion power generation module realizes the deep recovery and efficient conversion of waste heat. The intelligent coupled power generation and power management module improves the power quality and grid adaptability. The multi-parameter collaborative control module and the self-repairing working fluid circulation module ensure the long-term stable operation of the system. In summary, the system of the present application has significant economic and environmental benefits and can be widely applied in the field of waste heat recovery of centrifugal compressors.

[0108] The bar chart attached to the specification Fig. 2 It can be seen that the bar chart intuitively presents the technical advantages by comparing the energy efficiency of the traditional single-stage system and the cascade system of the present application under different operating loads (50%, 75%, 100%). The energy efficiency of the traditional single-stage system decays significantly at low load and it is difficult to break through the efficiency bottleneck at high load, which is due to its fixed expansion ratio and single energy conversion path. The system of the present application uses two-stage expansion machine series connection and pressure matching technology, which can dynamically adjust the working fluid power process according to the load and maintain high efficiency within the full load range. For example, under the 75% load condition, the efficiency of the traditional system is only 20.5%, while the efficiency of the system of the present application reaches 25.8%, with a significant improvement. The average energy efficiency improvement of 26.8% indicates that the design effectively solves the efficiency loss problem of the traditional system under variable working conditions, especially for the centrifugal compressor exhaust waste heat which has a large fluctuation, providing a more optimal solution for industrial waste heat recovery

[0109] The graph attached to the specification Fig. 3 It can be seen that the graph compares the performance of traditional PID control and model predictive control (MPC) of the present application in system optimization. Due to the dependence on fixed parameter adjustment, the PID control cannot reach the ideal objective function value even after 50 iterations in the face of the multivariable strongly coupled organic Rankine cycle system, with large steady-state error and response lag. The MPC algorithm can predict the future behavior of the system and the objective function value is lower than the final value of the PID control at 10 iterations, and it converges to the optimal value at 30 iterations, which is 61% faster than the PID control. Combined with parameter optimization based on entropy production analysis, MPC can identify inefficient links in the system in real time, such as quickly adjusting the working fluid flow and expansion ratio during waste heat transients, reducing irreversible losses. This intelligent control strategy enables the system to quickly respond and maintain high efficiency in the face of complex working conditions, significantly improving overall energy efficiency and stability.

[0110] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can make equivalent substitutions or changes within the technical scope disclosed by the present application and according to the technical solutions and inventive concepts of the present application, which should be covered within the protection scope of the present application.

Claims

1. A centrifugal compressor exhaust waste heat driven organic Rankine cycle power generation system, characterized by, The modules include the following: Adaptive variable structure waste heat collection module: arranged in the exhaust pipeline of centrifugal compressor, containing adjustable helix angle finned tube heat exchanger, through the step motor drive fin rotation, real-time adjustment of helix angle, realize the reynolds number Re flow state optimization; Set up double medium heat exchange loop, main loop flow organic working medium, vice loop filling phase change energy storage material, through Realize the dynamic storage and release of waste heat, compensate the energy supply when the load fluctuates, wherein m is the mass of the phase change material, The melting latent heat; The step expansion power generation module adopts a two-stage expander series structure, the first stage expander is a radial inflow type, and the second stage is an axial type connected through a pressure matching device; a working medium shunt valve is configured to dynamically adjust the working medium proportion entering the two-stage expander according to the exhaust temperature; Intelligent coupling power generation and power management module: the generator adopts a reluctance switching permanent magnet synchronous generator, which realizes high-efficiency power generation in a wide speed range through stator winding switching; the power management unit integrates virtual synchronous generator (VSG) technology, and realizes inertia control algorithm Simulate the characteristics of a synchronous generator, wherein is the virtual inertia, is the inertia coefficient, is the grid angular frequency; a dynamic reactive power compensation device is configured, which adjusts the reactive power output in real time according to the grid voltage fluctuation, and the adjustment algorithm is: , wherein is the compensation reactive power, is the compensation coefficient, , are the grid voltage and the reference voltage, respectively; Multi-parameter coordinated control module: based on model predictive control (MPC) algorithm, a multi-variable prediction model including waste heat collection, organic Rankine cycle and power generation system is established, and the global optimal control of the system is realized through rolling optimization solution , wherein J is the objective function, is the prediction time domain, y is the system output, r is the reference trajectory, Q and R are weight matrices; the entropy production analysis is introduced to monitor the irreversible loss of the system in real time and automatically adjust the key parameters; Self-repairing working fluid cycle module: integrate a nanometer catalyst bed in the working fluid circuit, which is loaded with noble metal active components, and catalytically decompose the thermal decomposition products of the working fluid through an algorithm formula: , where r is the reaction rate, k is the reaction constant, is the impurity concentration, is the activation energy, R is the gas constant, and T is the temperature; an online working fluid quality detection unit is provided, which monitors in real time through a dielectric constant sensor and automatically triggers the purification process when the decomposition product concentration exceeds the threshold value.

2. A centrifugal compressor exhaust waste heat driven organic Rankine cycle power generation system according to claim 1, characterized by, The fin surface is provided with a micro-channel structure, the groove depth h, the groove width w, through an algorithm formula: Strengthen heat transfer, wherein Nu is the Nusselt number, d is the pipe diameter; the phase change energy storage material is a graphene modified composite salt, through an algorithm formula: Optimize the heat response speed, wherein The effective thermal conductivity is , The thermal conductivities of the matrix and the particles are The particle volume fraction is 3. The ORC system of claim 1, wherein the ORC system further comprises a heat exchanger configured to transfer heat from the exhaust gas to the working fluid. In the stepwise expansion power generation module, the first-stage expander impeller adopts a three-dimensional flow channel design, the blade outlet angle β is determined by an algorithm formula: Optimizing energy conversion efficiency, wherein is the head coefficient, is the theoretical head, u is the impeller peripheral velocity, is the flow coefficient; the secondary expander adopts an adjustable guide vane structure, the guide vane installation angle α satisfies wherein is the polytropic efficiency, is the design efficiency, is the efficiency correction coefficient, is the optimal installation angle.

4. The ORC system of claim 1, wherein, The stator winding of the reluctance switching permanent magnet synchronous generator adopts a star-delta switchable structure, impedance matching in a wide load range is realized through an algorithm formula , wherein , are the star and delta connection impedances respectively; the primary frequency modulation coefficient formula of the virtual synchronous generator is: , wherein , are the rated and minimum frequencies, , are the maximum and minimum active powers.

5. The ORC system of claim 1, wherein, In the multi-parameter cooperative control module, the weight matrix of the model predictive control algorithm is: The particle swarm optimization (PSO) algorithm is used for online setting to meet Wherein, N is the iteration number, is the target function value; in the optimization strategy based on entropy production analysis, when the entropy production exceeds the reference value by 15%, the system parameter reconstruction is automatically triggered, and the working medium flow is adjusted.

6. A centrifugal compressor exhaust waste heat driven organic Rankine cycle power generation system according to claim 1, characterized by, In the self-repairing working medium cycle module, the nano catalyst bed layer adopts a honeycomb structure, and the formula Optimizes the catalytic effect, wherein The catalytic efficiency is , k is the reaction rate constant, a is the specific surface area, The effective diffusion coefficient is L, the bed layer thickness; The dielectric constant sensor of the working medium quality online detection unit adopts a coaxial cylindrical structure, and the algorithm formula is: Realize accurate monitoring of working medium state, wherein C is the capacitance value, L is the electrode length, and a and b are the inner and outer electrode radii.

7. A centrifugal compressor exhaust waste heat driven organic Rankine cycle power generation system according to claim 2, characterized by, The adaptive variable structure waste heat collection module, the double medium heat exchange circuit is provided with a dynamic flow distribution valve, and the flow ratio is adjusted according to , , are the flow rates of the main circuit and the phase change circuit respectively, is the melting point of the phase change material, is the ambient temperature; an ultrahydrophobic coating is deposited on the surface of the microchannel structure, and the contact angle θ is greater than or equal to 150°.

8. A centrifugal compressor exhaust waste heat driven organic Rankine cycle power generation system according to claim 3, characterized by, The pressure matching device adopts a zoom nozzle structure, the throat diameter of the zoom nozzle structure is gradually reduced from the inlet to the outlet wherein, is the mixed flow, 、 respectively, the density and the flow rate at the throat, through the formula: the pressure matching efficiency is optimized, wherein 、 is the inlet and outlet pressure, is the specific heat ratio, is the inlet Mach number; the bearing of the two-stage expander adopts a magnetic fluid sealing technology, through the formula: zero leakage is achieved, wherein F is the sealing force, is the vacuum permeability, M is the magnetization, H is the magnetic field strength, and A is the sealing area.

9. A centrifugal compressor exhaust waste heat driven organic Rankine cycle power generation system according to claim 4, characterized by, The intelligent coupling power generation and power management module, the dynamic reactive power compensation device adopts modular multilevel converter MMC, and the sub-module capacitor Wherein is the maximum reactive capacity, f is the grid frequency, is the DC side voltage, through the formula control output voltage, wherein m is the modulation ratio, is the AC side voltage; the power quality monitoring unit integrates the harmonic source positioning function, and the formula based on the directional power method is: When is positive, it is determined that the harmonic source is located downstream of the measurement point, wherein is the hth harmonic power, , is the hth harmonic voltage and current, is the phase difference.

10. A centrifugal compressor exhaust waste heat driven organic Rankine cycle power generation system according to claim 5, characterized by, The prediction time domain of the model prediction control algorithm in the multi-parameter coordinated control module According to the adaptive adjustment of the system dynamic characteristics, the system can meet Wherein The reference time domain is The adjustment coefficient is The system time constant is The sampling period is; in the system reconstruction strategy based on entropy production analysis, the economic optimization target algorithm is introduced: Wherein C is the total cost, The entropy production cost coefficient of each component is The entropy production change is The energy cost is The power generation change is.

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