Start-up Process Research Articles

Study on start-up characteristics of single piston free piston linear generator for small-scale compressed air energy storage system

This study presents a new idea of applying single piston free piston linear generator (FPLG) to small-scale compressed air energy storage (CAES) system. Firstly, a single piston FPLG prototype for CAES is built. Then, the thermodynamic, motion and output characteristics of FPLG during start-up process are studied based on the experimental data. The results show that the start-up process of single piston FPLG can be divided into three stages, and the order of achieving a steady state is movement and output > in-cylinder pressure > the in-cylinder temperature. The in-cylinder temperature increases in a spiral pattern, and the temperature difference between adjacent cycles at the same state point decreases. In the 0th cycle, when the free piston assembly (FPA) moves from top dead center (TDC) and bottom dead center (BDC), the peak current and power output are greater than the other cycles. The peak current and power output when FPA moves from TDC to BDC are greater than those when FPA moves from BDC to TDC. The maximum current and power output can reach 0.8 A and 62.25 W. At the beginning of the expansion stage, as the intake duration (tin) increases, the in-cylinder pressure increases first and then decreases. As the intake pressure (pin) increases, the in-cylinder pressure continues to increase. In addition, the in-cylinder temperature of working chamber A (TA) is lower than in-cylinder temperature of working chamber B (TB), and the temperature difference between TA and TB can reach 12.4 K. At higher pin condition, the intake point cannot be too close to the two ends and tin cannot be too long. At lower pin condition, the intake point cannot be too close to both ends and tin cannot be too short to ensure the system starts. The purpose of this paper is to provide valuable insights and guidance for the practical application of small-scale CAES system.

Non-linear cascade control with gain-scheduling and startup control strategy study for thermionic space reactor TOPAZ-II

The TOPAZ-II thermionic space reactor system, which was designed by the Soviet Union, is characterized by its high degree of nonlinearity and positive temperature reactivity feedback. The thermionic space reactor exhibits characteristics of high inertia and significant delay in controlling its electrical power and outlet temperature. The simple PID controller is difficult to achieve good performance. To carry out controller design for thermionic space reactor, the simulation platform for thermionic space reactor is developed based on coupling between reactor system thermal-hydraulic code RESYS and control system simulator in this study. After that, based on the cascade control strategy and gain-scheduling, the reactor thermal controller, electric power controller, outlet temperature controller applicable for the full power range is designed with transfer function model and frequency domain analysis method. To validate the nonlinear electric power controller performance, the continuous minor step disturbances, major step disturbances, and ramp variation of electric power setpoint is simulated. The performance of outlet temperature controller is verified with the simulation result of step and ramp variation of outlet temperature setpoint. Thereafter, the start-up process of the thermionic space reactor TOPAZ-II is simulated and analyzed. The simulation result reveals that the controller designed in this paper can overcome the nonlinearity of the thermionic space reactor system and has good performance throughout the entire power range. Compared to traditional simple PID controller, the cascade controller has better performance and can achieve good control performance even in situations where simple PID controllers cannot function properly.

Dynamic strain distribution monitoring and fatigue damage analysis on a 100 kW wind turbine blade based on field aerodynamic measurements

Abstract Operation and maintenance (O&M) costs can account for 10%–20% of the total costs of electricity for a wind project. Structural health monitoring method is a form of preventive maintenance consisting of regular monitoring of the wind turbine components to detect potential faults. The strain measurements on the blades are typically used for load monitoring and damage detection, but only obtain a small amount of concentrated load information. In this work, a strain distribution monitoring method was proposed and validated based on aerodynamic measurements in the field. Then the contribution and evolution of the strain distribution from the aerodynamic load, gravity load, inertial load, and centrifugal load in the complex start-up process of the wind turbine were analyzed. The results shows that the mean value of the synthetic strain is mainly determined by the aerodynamic load and the centrifugal load, while the fluctuation amplitude is mainly determined by the gravity and the aerodynamic load. Furthermore, the fatigue damage of the blade root was evaluated based on strain extrapolation, rainflow cycle-counting algorithm, Goodman diagram and Miner’s linear superposition principle. It is found that the fatigue damage is generally greatest near the pressure side and suction side, and least near the leading edge and trailing edge. The strain distribution monitoring method can capture the location of maximum stress and the most severe fatigue damage on the blade, which are helpful for damage detection and load control, and further reduces O&M costs.

Intelligente Anlaufsteuerung für die Batteriezellenproduktion

Abstract The ramp-up of production lines as a result of changing product variants or production processes puts battery cell manufacturers under enormous quality and cost pressure due to high reject rates. A control system based on artificial intelligence methods can help to speed up the start-up processes. The InTeAn research project developed a procedure for developing a process control system to reduce ramp-up times and costs in battery cell production.

Development of double-layer rotors for asynchronous drives of mining and transport machines

Due to the simplicity of the design and high energy indicators, asynchronous electric motors (AM) are the main consumers in the power supply systems of mining enterprises. Large starting currents of motors lead to heating and damage to the insulation of the stator windings. An urgent problem to improve the reliability of mining and transport machines is the development of AM, providing smooth transients with increased starting torque and reduced starting current. In an AM with a closed-loop rotor, a magnetic conductor is performed by a charged cylinder on the rotor shaft, which is made of electrotechnical steel with high magnetic permeability. The electrical conductor is often a squirrel cage-type short-circuited rotor made of a material with high specific conductivity. A technology has been developed for producing ferro-copper alloys for the active outer cylinder of a double-layer rotor, replacing a "squirrel cage". These alloys combine the properties of an electric current conductor and a magnetic flux. This allows us to obtain the effect of displacement and reduction of current in the rotor, which is accompanied by an increase in the effective resistance of the rotor and the electromagnetic torque during the start-up process. Full-scale experiments have been carried out with asynchronous motors with various rotors having a displacement effect. Motors having double-cage or deep-groove rotors develop an increased starting torque at a relatively lower starting current. The starting quality of these motors is, on average, 1,5 times higher than that of a motor without current displacement. Replacing a double-cage rotor with a double-layer rotor leads to a decrease in the starting current by 25% and an increase in the starting torque by an average of 2,5 times. The quality factor of starting an asynchronous motor with a double-layer rotor is 3-4 times higher than the quality factor of starting similar motors with a conventional rotor cage without current displacement, 2-2,5 times compared with a double cage or a deep groove and 1,3-1,5 times compared with a rotor with a high electrical resistivity. The use of double-layer rotors limits voltage fluctuations in the network, ensures a reliable, smooth start, eliminates vibration and extends the service life of all equipment.

Internal temperature prediction and control strategy design of anode-supported solid oxide fuel cell for hot start-up process

Anode-supported solid oxide fuel cell (SOFC) has a high energy efficiency while suffering from a poor transient performance such as start-up. In this study, a model-based design method is proposed to develop a suitable strategy for the rapid hot start-up of anode-supported SOFC (AS-SOFC). First, a mathematical model is established for a 25-kW SOFC system and the internal temperature is predicted. Subsequently, three different strategies are compared during hot start-up process. The results indicate that the positive-electrolyte-negative (PEN) temperature variation magnitude is 50 K and the response time is 1300 s when the hydrogen and the air flow rates are fixed for the afterburner and the cathode. If a PID controller is employed to regulate the flow rate of H2 to the afterburner, the PEN temperature variation magnitude decreases to 16 K with a shorter response time of 158 s. When increasing the air flow rate synchronously, the PEN temperature variation magnitude is merely 8 K, reduced by 84 % and 50 % compared with the previous strategies. Additionally, the gas temperature exiting from the afterburner declines significantly for the third control strategy. Thus, the lifetime and reliability of AS-SOFC is enhanced. The results provide a reference for the SOFC systems control such as domestic combined heat and power (CHP) and mobile applications.

Sustainable Entrepreneurial Process in the Deep-Tech Industry

To date, deep-tech entrepreneurship and sustainable entrepreneurship are both attracting the interest of researchers. Indeed, deep-tech is being employed to address future sustainable challenges in the present. Nevertheless, the process of deep-tech startups is filled with distinct obstacles. These types of startups may necessitate a more targeted sustainable entrepreneurial process and specialised knowledge compared to conventional technological startups or general sustainable entrepreneurial processes. Currently, most publications discuss either a sustainable entrepreneurial process or conventional technical startups. Therefore, this article aims to investigate the process of sustainable entrepreneurs as they transition from startup ventures to scaleup enterprises within the context of the deep-tech industry. Based on previous sustainable entrepreneurial processes, a multiple case study was conducted within six deep-tech startups, using a narrative progress research strategy, to find the sustainable process pattern. A conceptual model of a sustainable entrepreneurial process in deep-tech industry is established, including five phases with six activities: (i) Sustainable idea definition; (ii) Sustainable opportunity recognition and evaluation; (iii) Venture launch; (iv.i) Sustainable products/services development; (iv.ii) New sustainable enterprise financing; and (v) Sustainable enterprise scaleup. This process enables sustainable deep-tech entrepreneurs, policymakers, and financial investors to necessarily have an overview of the key entrepreneurial stages to navigate from the startup to the scaleup process.

Clutch Torque Optimization for Heavy-Duty Vehicles Starting Based on Intelligent Identification of Driver’s Starting Intention, Vehicle Mass, and Road Grade

<div>For heavy-duty vehicles equipped with automated mechanical transmission (AMT), the control of automatic clutch torque is crucial during the start-up process. However, the difficulty of controlling clutch torque is exacerbated by differences in driver’s starting intentions, changes in vehicle mass, and road gradient. Therefore, this article proposes the clutch starting torque optimization strategy based on intelligent recognition of driver’s starting intention, vehicle mass, and road gradient. First, an intelligent recognition strategy is proposed based on the combination of data-driven and onboard transmission control unit (TCU) algorithms, which improves the accuracy of recognizing the driver’s intention to start as well as the vehicle mass and road gradient. Based on the vehicle’s historical state data information, the predictive model is trained offline using a long–short-term memory (LSTM) network to obtain predicted parameter identification results, which are then used to calibrate the computed values of the onboard TCU algorithm. Second, the clutch torque optimization strategy is designed based on the driver’s starting intention, while considering the effects of road gradient and vehicle mass on the clutch starting resistance torque. The weight coefficients of the objective performance function are adjusted according to the driver’s starting intention, and the Pontryagin’s minimum principle (PMP) is used to solve the clutch target torque. Finally, offline data training and real-vehicle testing are performed. The results show that the optimization strategy can effectively reduce the friction work and the degree of impact during the starting process, minimize the clutch slipping time, and improve the smoothness of vehicle starting and driving comfort.</div>

Transient mixed thermal elastohydrodynamic lubrication analysis of aero ball bearing under non-steady state conditions

A transient mixed thermal elastohydrodynamic lubrication model of bearing considering the thermal effect and the changes in velocity, load, and contact geometry is proposed. Based on the bearing dynamic and lubrication analysis, the effects of bearing rotational speed and start-stop conditions on the dynamic behavior and lubrication performance are studied. Results show that when the bearing rotational speed exceeds a certain critical value, the increasing speed will reduce the film thickness, especially the outer raceway. The increasing bearing acceleration can cause a higher slide-roll ratio and film temperature at the initial start-up process. Compared with the start-up process, the lubrication change in the shut-down process has a similar opposite trend, but the overall lubrication performance is better.

Challenges and Perspectives of the Startup Ecosystem for the Development of Innovative Economy in Georgia

The processes of introduction of technology and innovation ecosystem in the economic development of the country have attracted special attention in the global world in the conditions of pandemic and post-pandemic. Accordingly, the research focuses on the formation and development models of modern start-up ecosystems, processes and determinants that ensure their transformation into innovations and the transfer of resources for economic development in the regions. The aim of the paper is to determine the main directions that will contribute to the development of startup ecosystems, taking into account global trends and state-specific practices; The research is based on the methods of grouping, comparison, analogy, analysis, generalization and systemic-structural approaches. As a result of the research, startup ecosystems were defined as an institutional mechanism that is open to the expansion of intersectoral networks and changes the competitive market environment in favor of the architecture of a stable innovative economy. The examples of Estonia, Spain, and Britain show the potential of developing a national startup ecosystem model that prioritizes long-term development, state technical self-sufficiency, and the ability to expand to new markets. Keywords: innovative economy, ecosystems, technoparks, startups, innovations, R&D, economic development

Reduction of the Emission Footprint of Gas Turbines in Future Energy System Scenarios Through Optimized Hydrogen Admixture Strategies

Abstract Due to the inherent volatility of renewable power generation technologies, dispatchable components, such as gas turbines (GT) will have to be used increasingly for residual load balancing. In addition, GTs are expected to operate fewer hours per year, more flexibly, and at lower capacities. However, fuel utilization in GT is inherently linked to emissions. As a potentially CO2-free energy carrier, hydrogen is a promising fuel for GTs and manufacturers are working on suitable combustor technologies. However, the availability of large quantities of CO2-free H2 remains unclear in the near future. In this study, a physical-based gas turbine performance model and an emission calculation tool are used to derive an optimized H2 admixture strategy for different load profiles. Characteristic load demand scenarios are derived from actual load profiles of gas power plants and the emission footprints are comprehensively evaluated by different environmental impact categories. In general, the emission footprint is increased significantly and moderately for capacity reduction and flexibility increase of GT operation. The availability of H2 in the near future is derived from forecasts for Germany, and the corresponding quantities are allocated to the partial loads according to the optimized strategy. In most scenarios, the addition of H2 is associated with a reduction in emissions compared to conventional fossil fuel operation. The greatest leverage of H2 admixture in reducing the environmental footprint is found when applied from the lowest load up, thus assisting in the start-up and shut-down process.

Start-up of a full-scale two-stage partial nitritation/anammox (PN/A) process treating reject water from high solid anaerobic sludge digestion (HSAD)

High solid anaerobic digestion (HSAD) achieves the benefits of high volumetric loading rates and lower reject water production, which, however, results in much more concentrated reject water with a remarkable increase in organics and nitrogen compared with that from conventional AD with low solid content. The high concentrations of ammonium (2000–3500 mg/L) and COD (3000–4000 mg/L) were reported to exert inhibition on anammox bacteria (AnAOB), posing challenges to the application of the partial nitritation/anammox (PN/A). To date, no cases of PN/A process start-up for sludge HSAD reject water were reported. This study demonstrated the start-up process of a 480 m3/d PN/A project without anammox sludge inoculation and treating HSAD reject water from a centralized dewatered sludge treatment plant. The project did not construct new infrastructures but utilized previously constructed tanks to upgrade the process from existing short-cut nitrification-denitrification to a two-stage PN/A process. Although no external anammox sludge inoculation was performed to save seeding sludge cost, the start-up was successfully achieved in about 9 months (273 days) based on a three-step method of “AnAOB enrichment - sludge acclimation - capacity doubling”. During start-up, the relative abundance of AnAOB (Candidatus_Kuenenia) increased from near zero to 12.0%. After start-up, the total inorganic nitrogen (TIN) removal load reached 0.74 kgN/(m3•d), with a total nitrogen removal efficiency of over 90%. Compared to the traditional nitrification-denitrification process, the PN/A process remarkably reduces the addition of organic chemicals and aeration energy consumption, saving approximately 4.2 million yuan (RMB) in operational costs annually. In summary, this research provides a full-scale reference for the start-up of the PN/A process treating sludge HSAD reject water.

Multiphase time-varying batch process monitoring based on stage moving model migration

To improve product qualities and obtain maximum comprehensive economic benefits from batch process production, it is of great practical significance to optimize the operation of batch production processes. Considering the multiphase and slow time-varying characteristics, a multiphase time-varying batch process monitoring method is proposed based on stage moving model migration technology. Firstly, the sliding windows are constructed with moving phases, where the moving of different phases is decided by the influence of the process variables to the final product. And time slices are the basic units for building the regression models. Secondly, to analyze and capture the relationship between the process variables of both the old mode and new mode and the final quality variable, the JY-PLS algorithm is utilized on each time slice within sliding windows for quality prediction. Then, monitoring indexes and corresponding control limits are calculated and used for process monitoring. The application to a real multiphase time-varying batch process, the start-up process of injection molding process, proved the effectiveness of the proposed method.

The Influence of Pre-Lift Gate Opening on the Internal and External Flow Characteristics During the Startup Process of an Axial Flow Pump

This paper focuses on a vertical axial flow pump and employs a 1D-3D coupling method to investigate the effects of different gate pre-opening angles on the internal and external flow characteristics of the axial flow pump during startup. Through comparative analysis, the following conclusions are drawn: In the study, a fully open gate is defined as 1, while a fully closed gate is defined as 0. When starting the axial flow pump with different valve pre-opening degrees, backflow occurs within the first 20 s of startup, and the backflow rate inside the pump gradually increases with the increase in the valve pre-opening degree. At a valve pre-opening degree of 0.6, the maximum backflow rate inside the pump reaches 5.89% of the rated flow rate. When starting the pump with the valve fully open, the maximum backflow rate reaches 10.98% of the rated flow rate, and the efficiency is affected by the backflow rate. The valve pre-opening degree has little impact on the axial force acting on the impeller during startup. When starting with a valve pre-opening degree of 0.6, the internal pressure difference in the pump is minimized. Within the first 20 s of startup, the internal pressure difference in the impeller is 28.96% higher and the flow velocity is 14.62% higher with valve pre-opening degrees of 0.8 and 1.0 compared to a 0.6 degree opening. During the initial stage of pump startup, with valve pre-opening degrees of 0.8 and 1.0, the pressure fluctuation amplitude inside the pump is minimal, with maximum relative amplitudes of only 0.621 and 0.525, which are 41.00% and 28.51% lower than the maximum amplitudes at 0 and 0.2 degrees, respectively. In summary, the peak pressure inside the pump is minimized when the valve pre-opening degree is around 0.8, while the pressure difference and flow velocity are relatively lower at a pre-opening degree of 0.6. It is recommended to start the pump with a valve pre-opening degree of around 0.6 to 0.8.

Numerical method research and characteristics analysis on frozen start-up process of high-temperature heat pipe

Future space exploration technology requires a long-life and reliable power source that is not reliant on solar energy. Space micro-reactors are able to meet this need, with Heat Pipe Cooled Reactors (HPR) emerging as a notable type of space micro-reactor that has attracted widespread attention in recent years. The HPR utilizes high-temperature alkali metal heat pipes for heat transfer, which presents certain complexities due to the solid state of the alkali metals working medium at room temperature. This results in a three-phase transition during the high-temperature heat pipes start-up process, which significantly impacts the heat transfer characteristics and dynamic behavior of the HPR start-up process. Consequently, thorough research is necessary in this area. Numerical simulation is a crucial tool that can effectively analyze, predict, and guide experiments. This article utilizes the Finite Volume Method (FVM) to develop a simulation code for high-temperature heat pipe frozen start-up. Various physical models are integrated to describe different components of the heat pipe: the container is represented by a two-dimensional axisymmetric heat conduction equation, the wick region utilizes a Fixed Grid Method (FGM) to depict the melting process of the medium, and the vapor channel is described through a two-dimensional axisymmetric compressible laminar flow. The wick region and vapor channel are coupled through the evaporation and condensation of the medium. For the vapor channel, numerical methods such as SIMPLE and PISO are used for solving. Adaptive time step and OpenMP acceleration are employed in the code to enhance computational efficiency. Finally, by comparing the calculated results with experimental data, the feasibility and accuracy of the code are assessed, highlighting special phenomena during the start-up process. The findings confirm that the developed code accurately predicts parameter changes during start-up, and can serve as a heat pipe analysis module for multi-physics coupling analysis of HPR.

Investigations into Hydraulic Instability during the Start-Up Process of a Pump-Turbine under Low-Head Conditions

To investigate the hydraulic characteristics during the start-up process of a full-flow pumped storage unit under low-head conditions, numerical simulations were conducted to study the dynamic characteristics during the process, providing a detailed analysis of the dynamic behavior of the internal flow field during the transition period as well as the associated variation in external performance parameters. Study results revealed a vortex-shedding phenomenon during the initial phase of the start-up process. These vortices restrict the flow, initiating a water hammer effect that abruptly elevates the upstream pressure within the runner. As the high-pressure water hammer dissipated, the flow rate rapidly increased, leading to a secondary but relatively weaker water hammer effect, which caused a momentary drop in pressure. This series of events ultimately resulted in significant oscillations in the unit’s head. After the guide vanes stop opening, the vortex structures at the runner inlet and outlet gradually weaken. As the runner torque continues to decline, the unit gradually approaches a no-load condition and enters the S-shaped region. Concurrently, pressure pulsations intensify, and unstable vortex formations reemerge along the leading and trailing edges of the runner blades. The escalated flow velocity at the runner’s exit contributes to the elongation of the vortex band within the draft tube, ultimately configuring a double-layer vortex structure around the central region and the pipe walls. This configuration of vortices precipitates the no-load instability phenomenon experienced by the unit.

Experimental and numerical study on dynamics of viscoelastic liquid cone in flow focusing

The effects of viscoelasticity on the stability and morphology of the liquid cone in liquid–liquid flow focusing are investigated experimentally and numerically. The particle tracers are utilized in experiments to visualize the flow fields, and the Oldroyd-B model is applied in numerical simulations to describe the viscoelastic characteristics of the liquid cone. Based on the quantitative analyses on the elastic stresses and forces inside the cone, the influence of viscoelasticity on the startup process of the liquid cone is first investigated. The stretching and shrinking stages of the viscoelastic cone are identified, and the startup process of the Newtonian cone is also studied for comparison. By considering the force balance at local jet position, a scaling analysis is proposed to give the criterion for the establishment of the stable cone, which indicates that the axial elastic stress can promote the cone stability. Upon a stable liquid cone, the influences of viscoelasticity on the interface profile and flow field of the cone are further analyzed, indicating that an increase in viscoelasticity leads to more shrinkage of the cone interface. The shrinkage of cone leads to the acceleration of focused liquid and thus the decrease in the recirculation flow size. This fundamental work provides scientific guidance for understanding the influences of viscoelasticity in flow focusing process, contributing to the industrial applications of microdroplets production.

What makes women entrepreneurs happy: The life stage, entrepreneurial ladder, and subjective well-being

ABSTRACT This study explores the effects of women’s age, education level, and exposure to knowledge on the likelihood of engaging in different entrepreneurial stages, which drives their happiness. The proposed model was empirically evaluated from 304 samples in Taiwan. Results reveal that the age of women entrepreneurs positively affects the move through start-up processes. However, their age negatively impacts their education level, which also negatively influences entrepreneurial engagement. Furthermore, exposure to external knowledge is significantly associated with entrepreneurial engagement. Finally, passing different entrepreneurial stages acquires a feeling of self-fulfillment and is significantly associated with women entrepreneurs’ well-being, representing that happiness belongs to perseverance. These findings suggest that policy makers should improve the networking skills of aging females to help them overcome challenges at various stages and enhance their subjective well-being, which should be considered an integral part of entrepreneurship education.

Theoretical modeling and investigation of the influence of deaerator on the transient process in power plants

Deaerator is one of the most important equipment for steady state and dynamic operation of power plants. The deaerator energy storage utilization process is one of the most essential ways to enhance the variable load rate of power plants. The purpose of this study is to improve the dynamic simulation performance of the deaerator during unit load changes by constructing a more reasonable deaerator model, aiming to provide guidance for practical operations. In this paper, a thermal mass microelement algorithm is proposed for the heat transfer between droplets and steam in the deaerator, followed by segmental modeling of the deaerator. By comparing with the operation data of a power plant, the steady state operation error of the deaerator model is within 0.6 %. Subsequently, the unit load variation process is simulated and the dynamic variation accuracy of the model proposed in this paper is enhanced by 1–2 % compared to the lumped parameter model. The dynamic characteristics of the deaerator are obtained by simulating the step and ramp changes of the deaerator boundary conditions and the deaerator start-up process. In addition, during the simulation of condensate throttling, the maximum power of the unit using the deaerator model in this paper is 0.2–1.5 MW larger than that of the lumped parameter model.

Phase classification and transient effects of the start-up process of multi-functional pump station in pump mode

In the context of achieving the goal of carbon neutrality, multi-functional pump stations (MFPS) have been greatly developed as a new energy system in recent years. The MFPS can operate in forward direction in pump mode to pump water and in turbine mode in reverse direction to generate electricity. At present, the instability of the MFPS during start-up process (SUP) in pump mode has become the key to restricting the operating life and further development of MFPS. In this paper, based on the motion characteristics of the pump and the cut-off facility (COF), the SUP of the MFPS in pump mode is clearly classified. In order to reveal the transient effect during the SUP, the steady-state full characteristic experiment (SFCE) of the pump was carried out. The occurrence phase of the transient effect during the SUP is analyzed, and the deviation between the steady-state external characteristics and the transient characteristics is revealed. In this study, the evaluation formula of the start-up completion degree (SUCD) of the MFPS in pump mode is proposed for the first time, and the evaluation and identification of the start-up progress at different phases are completed. The results show that the water flow in the system is in a reverse flow state in the Phase I. The SUCD of Phase I is 17 %. In the Phase II, The high-speed jet flow in the pump flows to the inlet of the guide vane (GV), which gradually changes the mainstream direction in the GV. A certain vortex structure can be observed at the exit of the flap gate (FG). The SUCD of Phase II is 61 %. In the Phase I and II, the dimensionless head of transient simulation is much larger than that of SFCE. In the Phase III, the flow state in the impeller will gradually stabilize. The transient effect disappears and the pressure fluctuation intensity decreases. The SUCD of Phase III is 93 %. In the Phase IV, the separation vortex that persists from Phase I-III at the tail of the GV blades disappears. The diversion capacity at the gate increases, and significant annular flow can be observed near the FG.