Aiming at the problems in existing research on scraping‑type ice makers，including insufficient investigation into the quantitative relationship and influence mechanism between core operating parameters （especially circulating water flow rate） and ice‑making performance，lack of in‑depth verification of the system supercooling phenomenon，and insufficient guidance for engineering applications，a continuous wall‑scraping ice‑making system is proposed in this study.Experiments were carried out on this system under three circulating water flow rates：6.2，9.2，and 12.2 m³/h.The ice‑making rate，inlet and outlet temperatures of circulating water in the ice slurry generator，and refrigerant temperature on the outer surface of the generator were measured to investigate the influence of circulating water flow rate on ice‑making performance.The results show that as the circulating water flow rate decreases from 12.2 m³/h to 6.2 m³/h，the steady average ice‑making rate of the system gradually increases from 1.88 kg/min to 2.03 kg/min.Furthermore，reducing the circulating water flow rate can shorten the total ice‑making time，lower equipment energy consumption，and improve the coefficient of performance （COP） of the system.In addition，the temperature of circulating cooling water after entering the evaporator is below 0 ℃，indicating that the water is in a supercooled metastable state，and nucleation and crystallization occur under disturbance.When the inlet temperature of circulating water drops to 0 ℃，the outlet temperature is slightly higher than the inlet temperature due to the heat released during crystallization.This study reveals the regulatory effect of circulating water flow rate on the performance of the scraping‑type ice‑making system，which provides a scientific basis for the optimal configuration of circulating water pumps and energy consumption reduction in engineering applications.

To address the threats of internal leakage in high‑pressure gate valves to equipment safety and system energy efficiency optimization，research on quantitative detection and condition diagnosis of internal leakage was carried out.An internal leakage test platform for high‑pressure gate valves was established，and ultrasonic testing technology was used to conduct internal leakage tests under various combined conditions involving two media （liquid/gas），inlet pressure from 10~70 MPa，defect sizes from 0.1~0.3 mm，and valve diameters from DN65~DN130.The results show that as inlet pressure and defect size increase，both the internal leakage flow rate and the ultrasonic signal of liquid/gate valves show an increasing trend；as valve diameter increases，both decrease，a phenomenon mainly influenced by wall thickness.Under the same conditions，the gas internal leakage flow rate is approximately 10~431 times that of liquid.The gas ultrasonic signal is generally stronger than that of liquid，with signal amplitude approximately 1.4~3.2 times that of liquid；during internal leakage in liquid/gas gate valves，the outlet ultrasonic signal is generally stronger than the inlet signal，with an average difference maintained at 7.2 dBμV RMS.Based on the Gaussian process regression （GPR） method，using the Matern 5/2 kernel function （length scale of 1，signal variance of 0.707 1），an internal leakage flow rate prediction model was constructed，achieving a prediction accuracy of 93.55%.The obtained laws and the model have good universality，providing reliable application basis and theoretical support for the quantitative assessment and operating condition diagnosis of internal leakage in high‑pressure gate valves under different working conditions.

To address the issue of liquid accumulation in long‑distance wet natural gas pipelines，a piggable gas‑liquid separator is proposed.This separator incorporates a drainage structure featuring "circumferentially uniformly distributed slits+stepped sleeve separation chambers" at appropriate pipeline locations to ensure pipeline safety.A numerical simulation method for the flow field was established using the VOF multiphase flow model to analyze the influence of key drainage structural parameters on the internal flow field and separation performance.Parameter combinations were screened，and separation performance tests were conducted for validation.The results show that when the stepped sleeve diameters D₂ and D₃ increase from 80 mm and 100 mm to 100 mm and 125 mm，respectively，the separation efficiency improves by 18%.When the slit location L₁ increases from 20 mm to 80 mm，the separation efficiency decreases by 2.7%.When the slit length L₂ increases from 85 mm to 115 mm，the separation efficiency improves by 9%.When the slit width L₃ increases from 4 mm to 12 mm，the separation efficiency improves by 51.6%.The optimal parameter combination is determined as D₂=80 mm，D₃=125 mm，L₁=35 mm，L₂=105 mm，L₃=10 mm，achieving a separation efficiency of 97.6%.Laboratory tests indicate that when the liquid holdup increases to 4%，the separation efficiency is approximately 95%.When the superficial gas velocity increases to 10 m/s，the separation efficiency remains above 92%，with a difference of less than 4% between the two conditions.The findings provide a theoretical basis for the development and application of engineering prototypes of piggable gas‑liquid separators.

Quantitatively predicting the motion trajectory and force characteristics of complexly shaped foreign objects （FOs） in confined turbulent flows is key to assess the safety risks of industrial pipeline systems.In response to the limitations of existing CFD software，particularly inefficient mesh reconstruction for complex moving boundaries and difficulties in accurately resolving transient collision processes，this study proposed an innovative coupled numerical method that integrated the immersed boundary method （IBM） and the discrete element method （DEM）.A fluid flow model for a variable‑diameter pipeline containing spherical FOs was developed，achieving bidirectional，multi‑physics coupling （among the fluid，the FOs and the pipe wall） by combining an adaptive SST k-ω turbulence model with DEM contact theory.A hydrodynamic experimental test rig was constructed to measure the suspended height of spherical FOs in the variable‑diameter pipe.This revealed an average error of less than 10% between the experimental and numerical results，thereby validating the numerical model's reliability.Furthermore，the dynamic flow behavior of a block‑shaped FOs in the same variable‑diameter pipe was investigated，revealing significant differences in trajectory and flow field characteristics compared to spherical FOs.These results lay the computational path for understanding FOs induced motion mechanisms and developing future risk assessment methods.

Aiming at the freezing problem on the hot side of the high‑pressure vaporizer，a core component of the Fuel Gas Supply System （FGSS） for dual‑fuel power vessels，a three‑dimensional numerical model with dual channels was established for the high‑pressure vaporizer to simulate the flow and heat transfer processes of supercritical liquefied natural gas （LNG） and 50% ethylene glycol aqueous solution.Parametric analyses were carried out to investigate the effects of inlet temperature and flow rate on the hot‑side freezing behavior for both the cold side （supercritical LNG） and the hot side （50% ethylene glycol aqueous solution）.The numerical results show that under the 1∶1 alternating arrangement of cold and hot plates，freezing is prone to occur in the outlet region of the hot side，especially at the channel corners，leading to a decrease in the Nusselt number （Nu） and a 16% increase in flow resistance in the frozen sections.The reduction in inlet velocity （from 3.0 m/s to 0.5 m/s） and temperature （from 328 K to 308 K） on the hot side，as well as the increase in inlet velocity （from 0.5 m/s to 2.5 m/s） and the decrease in temperature （from 130 K to 110 K） on the cold side，all contribute to the thickening of the ice layer.Severe freezing occurs when the inlet velocity of the cold side is higher than that of the hot side，with the ice layer occupying up to 81.6% of the outlet channel cross‑sectional area，which significantly elevates the risk of freeze blockage in the heat exchanger.The quantitative analysis model for freezing behavior under the coupling effect of multiple parameters established in this study provides a theoretical basis for the optimal structural design of anti‑icing configurations for LNG high‑pressure vaporizers.

To investigate the influence of inter‑stage propagation coupling phenomena and diffuser vane clocking positions on pressure pulsations within a multistage centrifugal pump，a multistage centrifugal pump was used as a model.Monitoring points were arranged inside the pump to conduct numerical calculations of the unsteady flow under different diffuser vane clocking positions.The numerical simulation results were validated by experiments and showed good reliability.Simultaneously，the pressure pulsation amplitudes at each monitoring point were compared，revealing the inter‑stage propagation law of pressure pulsation signals and the influence of different diffuser vane clocking positions on pressure pulsations within the pump.The results indicate that there is a significant inter‑stage propagation phenomenon of pressure pulsation signals.Pressure pulsation signals in the first‑stage flow channel propagate into the second‑stage flow channel and couple complexly with the pressure pulsation signals there.Low‑frequency pulsation signals exhibit strong propagation capability within the multistage centrifugal pump flow channels，leading to a progressive superposition characteristic of low‑frequency pulsation intensity.Altering the diffuser vane clocking phase can promote mutual cancellation of pressure pulsations generated by inter‑stage rotor‑stator interaction，combining the peaks and troughs of pulsation signals，thereby effectively reducing the intensity of inter‑stage rotor‑stator interaction and significantly lowering low‑frequency signals.Except at the diffuser outlet，the average time‑domain reduction at other monitoring points is approximately 50%，with the optimal time‑domain reduction reaching 60.7%.This study can provide theoretical guidance for the design and operation of multistage centrifugal pumps.

To address the issue of performance limitations of high‑temperature heat pumps under wide temperature lift conditions，a heat pump cycle scheme was proposed to efficiently generate 140 ℃steam using 70 ℃ industrial waste heat.Under typical operating conditions with an evaporation temperature of 60 ℃ and a condensation temperature of 145 ℃，four high‑temperature working fluids，namely R1233zd（E），R1336mzz（Z），R1234ze（Z） and R245fa were selected to analyze their suitability in a quasi‑second‑stage compression heat pump cycle.The effects of intermediate pressure，subcooling degree，superheat degree and operating condition fluctuation on the coefficient of performance （COP） of the system were investigated.Furthermore，a cascade compression heat pump system model was developed，taking the influence of intermediate temperature on COP as an example，a comparison between the cascade compression heat pump and the quasi‑second‑stage compression heat pump was conducted.The results indicate that in the quasi‑second‑stage compression heat pump cycle，the optimal intermediate pressure is approximately 1.2 times the geometric mean pressure，and the minimum superheat degree is significantly affected by the operating conditions.In the cascade compression heat pump system，the optimal performance is achieved when R1233zd（E） is used as the working fluid in both the high‑temperature and low‑temperature stages.With an intermediate heat exchange temperature difference of 5 ℃，the COP is improved by approximately 12% compared with the quasi‑second‑stage compression system.R1233zd（E） demonstrates significant comprehensive performance advantages under the operating conditions in this study.This research can provide a theoretical basis for the system optimization design of quasi‑second‑stage and cascade high‑temperature heat pumps，as well as for the selection of environmentally friendly and highly efficient working fluids.

To address the problems of restricted installation and insufficient heat dissipation capacity caused by the excessively large shaft diameter of magnetic fluid seals in existing stirred reactors，as well as seal leakage induced by axial oscillation under the action of centrifugal force during machine operation，a compact‑structured end face magnetic fluid sealing device for stirred reactors was designed.A pressure resistance calculation model of magnetic fluid seals considering the effect of centrifugal force was established，and the finite element numerical method was used to explore the influence laws of design parameters such as sealing clearance，tooth width，tooth height and groove width on sealing characteristics，and the parameters were optimized using orthogonal test method.The results show that the seal pressure resistance value decreases with the increase of sealing clearance，increases first and then tends to stabilize with the increase of tooth width，and shows a variation characteristic of increasing first and then decreasing with the increase of both tooth height and groove width.Based on the influence laws of each parameter on sealing performance，the value ranges of the structural parameters in the orthogonal test are determined as follows：sealing clearance L_g=0.1~0.5 mm，tooth width L_t=0.5~0.9 mm，tooth height L_h=1.3~1.7 mm，and groove width L_s=1.0~1.4 mm.The order of the degree of influence of each parameter on sealing performance from the highest to the lowest is sealing clearance，tooth width，groove width and tooth height.The optimized structural parameters of the magnetic fluid seal are L_g=0.1 mm，L_t=0.7 mm，L_h=1.7 mm，L_s=1.1 mm，under which the seal pressure resistance value reaches 0.39 MPa，significantly higher than the 0.25 MPa required by the actual working conditions.This research can provide solution to the installation problems of sealing devices under special working conditions and expands the application scenarios of magnetic fluid sealing technology in the field of reactor sealing.

To enhance the solid particle separation and collection capability during soil discharge in tunnel cast‑in‑place pile construction，an optimization study was conducted to optimize the cyclone separator.Computational Fluid Dynamics （CFD） was employed to simulate and optimize the key structural parameters of the cyclone separator.The effects of exhaust vent diameter，exhaust pipe insertion depth，and dust discharge outlet diameter on separation efficiency and pressure drop were systematically investigated.The results show that：at an exhaust vent diameter of 200 mm，separation efficiency reaches 87.0%；excessively small or large diameters induce flow disturbance or short⁃circuiting effects.With an exhaust pipe insertion depth of 400 mm，peak efficiency hits 87.7%；excessive depth causes backflow at the dust outlet.A dust discharge outlet diameter of 250 mm achieves maximum efficiency （88.3%）；larger diameters weaken the centrifugal force field.The optimized cyclone separator achieved a fine soil particle separation efficiency of 88.23% in field tests.This result，which aligns closely with simulation data，confirms the feasibility of the optimization scheme for engineering applications.The research can provide reference for the optimal design of cyclone separators.

To investigate the mechanism of how the blade exit angle affects the internal flow and energy loss in centrifugal pumps，five types of impellers with blade outlet angles of 20°，23°，26°，29°，and 32° were studied.A combined approach of numerical simulation and experiment was adopted to investigate the hydraulic performance，energy loss，and pressure fluctuation of a centrifugal pump，aiming to reveal the underlying correlation between its internal flow characteristics and pressure fluctuations under different blade outlet angles.The results show that at a design flow rate Q_d=1.5 m ³/h，as the blade outlet angle increases，the head and shaft power increase，and the efficiency decreases from 69.71% to 69.38%；the high energy loss areas with entropy production rates greater than 20 kW/（K⋅m³） are mainly concentrated at the inlet and outlet of the impeller，the back pressure surface of the blades，and the tongue of the snail shell，and the energy loss in the wake area of the impeller increases with the increase of the outlet angle；the main frequency of pressure pulsation is basically consistent with the shaft frequency，with a maximum decrease of 16.45% in pulsation amplitude at 0.95R₀ and a maximum increase of 16.98% at 0.4R₀.Based on the comprehensive entropy production and vibration characteristics，the optimal blade outlet angle range is proposed to be between 23°and 26°.Within this range，energy dissipation and pressure pulsation are relatively low，which can provide theoretical reference for the hydraulic design of centrifugal pump impellers.