To address the challenges of lightweight and compact design in current spray devices caused by complex internal flow channel structures，multiple liquid supply pipelines and interfaces，and large space occupation，a nozzle structure design concept based on the integration of the inlet channel，swirl chamber，and orifice was proposed.A compact micro‑mist nozzle with a thickness of 5 mm was designed，and an experimental setup for measuring spray characteristics was established to investigate the influence of the compact micro‑mist nozzle's geometric structural parameters on atomization characteristics.The research shows that the flow rate and spray angle are significantly affected by the orifice diameter.Increasing the swirl chamber diameter reduces the liquid film breakup length，which is beneficial for achieving the primary atomization process within a shorter distance.At a spray height of 15 mm，the peak axial velocity of the compact micro‑mist nozzle is greater than 10 m/s，occurring inside the spray cone.When the swirl chamber diameter is small，the axial velocity proportion of droplets at the spray center is the largest.When the orifice diameter is large，the decay of the axial velocity proportion along the radial direction slows down.The sauter mean diameter of droplets from the compact micro‑mist nozzle is less than 40 μm.The droplet size and droplet number density distribution are less affected by the swirl chamber.An increase in orifice diameter results in a 25% increase in the proportion of droplets with a size below 20 μm.This study provides a new approach for achieving integrated and highly compact designs of atomization devices.

To suppress temperature fluctuations inside open‑type food refrigerated display cabinets caused by periodic defrosting，an optimized scheme of installing phase change cold storage materials （PCM） in the cold air ducts was proposed.By analyzing the temperature characteristics of the cold air ducts，ND-1 type PCM with a phase transition temperature of -3 ℃ was selected.The dosage of PCM was calculated based on the refrigeration system load，and the PCM was encapsulated into food‑grade cold storage packs and integrated into the cold air ducts.Under conditions of 25 ℃ and 60% relative humidity，the refrigeration performance of the refrigerated display cabinet before and after installing PCM was compared.The results show that compared with before the improvement，the vertical temperature uniformity of food packages on the first，third and fifth layers in the cabinet after the improvement has increased by 27.6%，21.2%，and 37.8% respectively，and the horizontal temperature uniformity has increased by 58.2%，15.9%，and 24.4% respectively.The average temperature of refrigerated food decreases by 1.12 ℃，the air curtain thermal suction coefficient decreases by 15.9%，the total energy consumption of the cabinet decreases by 6.2%，and the average air velocity attenuation rates at the supply and return air outlets decrease by 2.5% （supply air） and 6.5% （return air），respectively.This scheme effectively stabilizes the internal temperature field of the cabinet and improves energy efficiency.This study can provide a reference for the optimal design of food refrigerated display cabinets.

Aiming at the leakage problem of large vertical mixed flow pump，combined with its specific working conditions，a split type magnetic fluid sealing device was designed for easy disassembly and installation，and the magnetic field simulation of the sealing device was carried out by using the finite element analysis software.Training samples were designed using latin hypercube sampling across the range of critical structural parameters.BP neural networks and genetic algorithms（GA） were utilized to optimize these parameters.An experimental rig was constructed to conduct pressure endurance tests on the optimized seal device.

To improve the operational performance and service life of oil‑free compressors，a study on the friction and wear characteristics of the contact pair between piston rings and cylinder inner walls was conducted.Cylinder surfaces were coated with Teflon，SiC，and DLC，respectively，and filled PTFE was selected as the piston ring material for sliding friction and wear tests.The results show that the friction coefficient time series curve of the friction pair corresponding to the DLC‑coated cylinder is the most stable，with the lowest friction factor.The surface morphology of the DLC coating is favorable，and the wear rate of the piston ring is the lowest.The average friction coefficient of the friction pair corresponding to the Teflon coating is the lowest （0.074 6），but due to poor adhesion between the coating and the aluminum alloy substrate，wear is relatively severe.Both SiC and DLC coatings exhibit good adhesion to the substrate.The wear mechanism of all friction pairs is predominantly adhesive wear，with PTFE transfer films of varying morphologies formed on the surface of the counterpart during friction.Under room temperature （25 ℃） conditions，the transfer films exhibit a flaky structure，with the most complete transfer film observed on the surface of the DLC‑coated cylinder.This indicates that the DLC coating is a relatively ideal optimization solution for cylinder surfaces.The study provides a theoretical basis for the optimized design of oil‑free compressors.

To improve the performance of cavitation jet well‑cleaning and plugging removal guns，based on the design concept of multi‑cavitation synergy，a high‑efficiency well‑cleaning and plugging removal gun with multi‑cavitation synergistic effect was designed，and the flow field characteristics of the improved and conventional guns were comparatively analyzed.The results show that the performance of the new gun is significantly improved compared to the conventional gun，the inlet velocity of each nozzle layer increases by over 417.65%，the jet velocity correspondingly increases，and the jet core segment becomes longer and wider；the peak turbulent kinetic energy inside the new gun decreases by 26.95%，with less overall turbulent energy dissipation；the wall impact pressure of the new gun increases by 52.59%，indicating stronger jet impact；annular cavitation erosion zones exist around the jet impact area，and the erosion zone of the new gun expands by 195.42%；the new gun adopts a non‑uniform distribution strategy，with the first layer nozzles allocating 50% of the energy and the remaining energy equally distributed between the latter two layers；within the injection pressure range of 10~30 MPa，both the wall impact pressure and the cavitation cloud area of the new gun exhibit a linear growth trend with injection pressure.The research results can provide a theoretical basis for enhancing the field application effectiveness of cavitation jet well‑cleaning and plugging removal technology.

To address the issue of axial floating and angular deflection of the seal ring caused by changes in methane solubility and gas volume fraction in the oil phase within multiphase pumps，as well as slug flow impact，leading to seal ring wear failure，a transient dynamic model for oil-gas two‑phase flow lubricated sealing considering methane dissolution is established.The model is solved using the finite difference method and the Euler method.The transient response characteristics of the seal before and after considering methane dissolution are compared，and the effects of axial pulsation and angular impact on the seal under different gas volume fractions when considering methane dissolution are investigated.The results show that when methane dissolution is considered，the fluctuations in film thickness and leakage rate are smaller，and the opening force tends to be consistent；during stage Ⅱ of axial vibration，when the gas volume fraction is 0.8，the displacement of the stationary ring is reduced by 3.25 times compared to when the gas volume fraction is 0；the stationary ring is less affected by angular impact，with the maximum change in central film thickness not exceeding 0.1 μm；when the gas volume fraction ranges from 0 to 0.8，the response of sealing performance to axial pulsation follows the same pattern；when the gas volume fraction is 0，the impact of angular shock on sealing performance is relatively small.This study provides theoretical guidance for the application of oil-gas two‑phase sealing in multiphase pumps.

To investigate the flow and heat transfer characteristics of liquid indium-tin-bismuth alloy within tubes，a systematic analysis was conducted on the effects of different tube types （including circular，elliptical，flattened，square，and triangular tubes） under the same equivalent diameter condition on temperature，velocity，and pressure distributions，as well as the influence of key thermal parameters such as Reynolds number and heat flux density on the heat transfer dynamics of the indium-tin-bismuth alloy.The results indicate that the square tube exhibits superior overall heat transfer performance compared to other tube types.When the inlet Reynolds number increased from 5 419 to 13 548，the heat transfer coefficient increased from 4 695.962 W/（m²⋅K） to 9 357.478 W/（m²⋅K）.When the wall heat flux density increased from 110 W/cm² to 130 W/cm²，the heat transfer coefficient increased from 4 695.962 W/（m²⋅K） to 5 541.235 W/（m²⋅K）.Both increasing the inlet Reynolds number and increasing the tube wall heat flux density significantly enhance the heat transfer efficiency between the liquid metal and the tube wall.This study provides a reference for the optimal design and application of thermal management systems utilizing liquid metals.

To address the issue of flow channel blockage caused by mineral particle sedimentation and backflow in a lifting pump after an emergency pump shutdown，CFD-DEM coupling method was used to numerically simulate internal solid‑liquid two‑phase flow during pump shutdown backflow conditions.The effects of changes in the number of impeller blades and diffuser blades on particle concentration distribution，particle backflow time，particle collision behavior，and backflow pass‑through rate were analyzed，and the reliability of the numerical simulation was verified through experiments.The results show an increase in the number of blades exacerbates particle accumulation and collisions in the first‑stage diffuser；optimizing blade number matching can significantly improve performance.When the number of impeller blades is 3 and the number of diffuser blades increases from 4 to 5，particle collision count decreases by 28.18%，and backflow pass‑through rate increases by 2.56%；when the number of diffuser blades is 5，increasing the number of impeller blades from 3 to 4 further reduces collision count by 12.36% and increases backflow pass‑through rate by 4.48%.The research results provide a theoretical basis for optimizing the design of lifting pumps.

To further reduce the oil concentration in the water outlet of the cyclone pre‑separation device and to lessen the load of subsequent treatment，a novel mixed‑flow hydrocyclone structure was proposed.Its performance was systematically investigated through numerical simulation and experimental validation methods.The results indicate that when the oil phase density is below 890 kg/m³，the oil viscosity is less than 75 mPa⋅s，and the inlet water cut ranges from 75% to 99%，the device can achieve performance indicators of a water separation efficiency greater than 50% and an oil concentration in the water outlet below 200 mg/L.When the inlet water cut is between 70% and 75%，the split ratio can be adjusted in the range of 0.55 to 0.65 with the oil concentration at the water cut below 400 mg/L.When the inlet water cut is not less than 75%，the split ratio can be adjusted from 0.4 to 0.6 with the oil concentration in the water outlet below 200 mg/L.The proposed mixed‑flow hydrocyclone demonstrates excellent separation performance under different water cut conditions.The research can provide an effective way for efficient pre‑separation of produced fluids from high‑water‑cut oil wells.

To address the severe erosion issue in common elbows for gas‑solid two‑phase flow，a pre‑helical pipe elbow was designed.The anti‑erosion structure of the helical pipe section was optimized using Fluent software in terms of twist angle，installation distance，and intermediate helical pipe section length，resulting in a pre‑helical pipe elbow with optimal anti‑erosion performance.The anti‑erosion effectiveness of this optimized structure was verified under varying medium flow velocities，mass flow rates，and time factors.The results show that the pre‑helical pipe elbow exhibits anti‑erosion effects only when the twist angle is between 90° and 600°，with an average improvement of 34.13% compared to the common elbow when the twist angle ranges from 210° to 420°.At twist angles of 390°，300°，and 330°，the maximum erosion rates of the pre‑helical pipe elbow are lower than those of the common elbow across the studied installation distances and intermediate helical pipe section lengths.Particularly when the installation distance is 0 mm and the intermediate helical pipe section length is 200~400 mm，the anti‑erosion effect is more significant.The optimized structural parameters are as follows：helical pipe section twist angle of 390°，installation distance of 0 mm，and intermediate helical pipe section length of 300 mm.Under these conditions，the pre‑helical pipe elbow achieves the best anti‑erosion performance，improving by 47.32% compared to the common elbow.Furthermore，although the maximum erosion rates of both this elbow and the common elbow increase with medium flow velocity，mass flow rate，and time，the maximum erosion rate of this elbow consistently remains lower than that of the common elbow，indicating that it maintains its anti‑erosion effectiveness at all times.The research results can provide a reference for the anti‑erosion structural design of elbows.

To address the issue of insufficient model accuracy for the R290 heat pump dryer dehumidification evaporator under complex thermal and humid conditions，a combined simulation and experimental approach was employed to study the flow heat transfer characteristics and performance optimization of the evaporator.Based on the unique two‑phase flow and heat transfer characteristics of R290，the general in‑tube two‑phase flow heat transfer model and pressure drop model were modified，and a distributed parameter model for the evaporator applicable to the large temperature‑humidity span conditions of dryers was constructed.A heat pump dryer experimental platform was built to validate the model accuracy across a wide range of humid air conditions （temperature 20~65 ℃，relative humidity 20%~95%）.The average errors for temperature and humidity predictions were 1.8 K and 5.1%，respectively.The results indicate that the heat transfer coefficient reaches its maximum，approximately 110 W/（m²·K），when the refrigerant quality inside the tube is around 0.4.There exists a limit to the dehumidification and heat transfer capacity of the evaporator；when the superheat exceeds 10~12 K，further increases in load lead to insignificant improvement （less than 4%） in heat exchanger performance.The findings provide a theoretical basis for optimizing the design and operation control of R290 heat pump dryer evaporators and offer certain engineering value for enhancing equipment energy efficiency and operational reliability.

To address the issues of single pumping performance diagnosis methods，limited regeneration capabilities，and insufficient testing accuracy in traditional Gifford-McMahon （GM） refrigerator cryopump test platforms，a high‑precision test platform was designed based on JB/T 11081—2011 standards.This platform integrates key data acquisition and display modules for temperature and vacuum，and innovatively introduces a thermal purge heating subsystem，while using a residual gas analyzer （RGA） to monitor real‑time pressure changes of the tested gas.Through theoretical calculations，simulation analysis，and experimental testing，the hydrogen pumping speed performance of the cryopump was validated.The results show that：the designed thermal purge device uses 100 ℃ nitrogen to purge the cryogenic surface，effectively meeting the regeneration heating requirements for flammable and explosive gases；during the test，cooling and vacuum performance remained stable without fluctuations；by collecting partial pressure changes before and after hydrogen injection，the measured average pumping speed was 4 291 L/s，with errors less than 10% compared to theoretical calculations （4 514 L/s） and simulation results （4 552 L/s），falling within the allowable error range，validating the rationality of the platform design.This platform can provide high‑precision testing methods for the performance optimization of domestic cryopumps.

To address the sediment wear issue in a centrifugal pump with adjustable guide vanes within a large‑scale water diversion project，a numerical prediction method based on the Euler-Lagrangian approach and a shape‑factor‑modified Oka model was established to study the internal flow field characteristics and wear patterns under low‑concentration sediment conditions.The results indicate that when the sediment concentration does not exceed 0.135 kg/m³，its influence on the internal flow field of the centrifugal pump is no more than 5%.Wear is primarily concentrated at the trailing edge of the blade suction side，the junction with the front shroud，and the leading edge of the adjustable guide vanes.The average wear intensity on the suction side is approximately 8.3 times that on the pressure side.Sediment concentration predominantly governs the linear regulation of wear intensity，while particle size primarily governs the wear distribution pattern：small particles cause severe wear at the trailing edge of the suction side，whereas large particles，due to inertial effects，shift wear towards the pressure side and the rear shroud.This study provides a theoretical basis for the wear‑resistant design and safe operation of centrifugal pumps with adjustable guide vanes.

To comprehensively understand the cooling effect of spray evaporation in double skin facade spray systems，a CFD two‑phase flow model for spray cooling double skin facade was established，and a discrete phase model （DPM） based on the Euler-Lagrangian method was employed to track the droplets.Through numerical simulation combined with experimental validation，the effects of parameters such as droplet injection velocity，spray flow rate，and number of nozzles on the cooling performance of the spray system were analyzed.The results show good consistency between the two，with the mean absolute percentage error for most temperature measurements within 15%，indicating that the DPM model can be used for simulation analysis of spray cooling in double skin facade.When the droplet injection velocity increased from 20 m/s to 80 m/s，the evaporative cooling efficiency of the spray system improved by 14.9%.Meanwhile，the spray flow rate also significantly influenced the cooling performance of the spray system.When the spray flow rate increased from 0.01 L/min to 0.09 L/min，the evaporative cooling efficiency of the system improved by 57.2%，the droplet evaporation rate increased by 2.9 μg/s，and the temperature distribution in the cavity became more uniform.The number of nozzles had a considerable impact on the cooling performance of the spray system.With three nozzles，the evaporative cooling efficiency and droplet evaporation rate of the system were 4.29 times and 2.6 times higher，respectively，compared to the single‑nozzle scenario.This research provides theoretical references for the optimal design of spray cooling systems and holds significant importance for improving the cooling performance of double skin facade.