To deeply investigate the complex flow mechanisms inside a jet pump，2D visual measurement and quantitative analysis of the confined space jet flow field inside the jet pump were carried out based on a high‑precision particle image velocimetry （PIV） system.The study focused on the regulatory mechanisms of the area ratio m and the flow rate ratio q on its flow characteristics.The results indicate that the length of the potential core decreases as q decreases，and the smaller the m，the faster the shortening rate.The axial velocity accelerates first and then decays within the suction chamber，and the decay rate is negatively correlated with q.The height and width of the recirculation zone are negatively correlated with q and positively correlated with m.When m=4 and q=0.534，the dimensionless height and width of the recirculation zone are 0.26 and 0.73，respectively；when q drops to 0.04，the height increases to 0.6，while the width increases significantly to 4.37.The jet half‑width first increases with axial distance and then stabilizes，with q influencing the half‑width distribution in the midstream.The velocity distribution in the midstream and upstream exhibits a partial self‑similarity state，while the downstream displays pipe flow characteristics.The radial velocity shows an antisymmetric distribution，with the peak velocity decreasing as q decreases；the change in velocity direction affects the acceleration and deceleration of the jet.The throat inlet is the point of minimum pressure，and q has a significant influence on the magnitude of the pressure rise along the throat and diffuser.Complex flow structures such as jet boundary fluctuations，wake oscillations，and potential core intermittency appear in the transient flow field.Spanwise vortices are generated at the nozzle exit and distributed along the shear layer；a decrease in q intensifies the erosion of the vortex core region，promoting turbulent mixing and vorticity dissipation.The results of this study provide a reliable experimental basis for the optimal design of jet pumps.

To address the issue of substantial waste heat generated during proton exchange membrane fuel cell operation not being effectively recovered，a water-steam dual‑heat source plate heat exchanger was designed to improve energy utilization efficiency.By varying its inlet conditions，the effects of steam and coolant temperature changes on the thermal characteristics of the heat exchanger were systematically analyzed.The results show that as the steam temperature increases，the proportion of steam heat exchange can reach up to 40% of the total heat exchange.As the coolant temperature increases，the proportion of coolant heat exchange can reach up to 82% of the total heat exchange.During the experiments，the heat transfer coefficients on the steam side and the coolant side reached maximum values of 156.9，783.44 W/（m²⋅K），respectively，indicating that the coolant side plays a dominant role in the dual‑heat source plate heat exchanger.Furthermore，as the steam temperature increases，the heat exchange efficiency gradually decreases；as the coolant temperature increases，the heat exchange efficiency gradually increases.Among these，steam temperature has a more significant impact on heat exchange efficiency：for every average increase of 1 ℃ in steam temperature，the heat exchange efficiency decreases by approximately 0.74%.The findings provide a reference for multi‑heat source waste heat recovery.

To address the challenges of conventional heating terminals in balancing rapid response with temperature uniformity，energy efficiency with comfort，and the inability to store excess heat or integrate heating and domestic hot water supply，a novel dual heat source natural convection terminal was proposed.This terminal was coupled with an air source heat pump to enable simultaneous heat exchange among three media：water，refrigerant，and air.The system could operate in three modes，single heating mode，heating and heat storage mode，and heat pipe discharge mode，through valve switching.An experimental system was set up in an artificial climate chamber to test the temperature characteristics of the novel terminal and the operational performance of the system under different outdoor ambient temperatures.The results indicated that in single heating mode，the time required for the novel terminal's surface temperature to reach 50 ℃ did not exceed 30 min，with a maximum surface temperature difference below 3.4 ℃，demonstrating uniform temperature distribution and the ability to achieve the required surface temperature for heating in a relatively short time.In heating and heat storage mode，the refrigerant heated the room air while simultaneously producing hot water.When the outdoor temperature was -10 ℃，the system's heating capacity reached 2.60 kW，and the heating COP remained stable at 2.96.In heat pipe discharge mode，the time for hot water to cool from 55 ℃ to 40 ℃ exceeded 5 h indicating that the stored heat could meet long duration heating demands.This study provides an effective technical pathway for addressing challenges related to response speed，temperature uniformity，and multi energy complementarity in air source heat pump heating systems，offering significant reference value for advancing efficient，comfortable，and low carbon heating technologies.

To address the performance optimization and operational stability issues of multiphase compressors under variable operating conditions，a systematic study was conducted on a self‑developed multiphase contra‑rotating axial compressor through a combination of numerical simulation and experimental validation.The influence of different rotational speed ratios on compressor performance was analyzed，with evaluation metrics covering aerodynamic performance （polytropic efficiency，total pressure ratio） and structural performance （blade load distribution，vibration characteristics）.The results indicate that when the rotational speed ratio （RSR） is below 0.77 or above 1.3，the compressor operation becomes unstable，and aerodynamic stall occurs in the contra‑rotating impeller.Within the optimal RSR range （0.77≤RSR≤1.3），optimizing the RSR can significantly improve compressor performance.Specifically，when RSR=0.91，the total pressure ratio reaches its maximum value of 1.181 4，which is 1.84% higher than that under the baseline condition （RSR=1）.In terms of structural performance，appropriate adjustment of the RSR can effectively improve the blade stress state and suppress vibration.When RSR=1.1，the maximum amplitude of the outer rotor is reduced by 5.18×10^-3 mm compared to that at RSR=1.Further analysis shows that increasing the rotational speed N₁ of the forward‑rotating inner rotor can simultaneously optimize aerodynamic efficiency and blade stability，whereas increasing the rotational speed N₂ of the contra‑rotating outer rotor may weaken the overall system stability.Reasonable selection of the rotational speed ratio is a key strategy for optimizing the comprehensive performance of multiphase compressors.The relevant conclusions can provide a theoretical basis and practical reference for the design and stable operation of similar compressors.

To study the working characteristics of the hydraulic system of a 90 MPa diaphragm compressor，a mathematical model of its hydraulic system was established，and a simulation model was built based on this mathematical model.The reliability of the simulation model was verified with measured data.The model considered the working characteristics of components such as the hydraulic cylinder，servo valve，make‑up oil pump，and plunger‑cylinder liner，while also accounting for the compressibility of the hydraulic oil and the oil‑gas interaction during actual operation.Using this simulation model，the dynamic variation curve of hydraulic oil pressure was obtained，and the influence of make‑up oil volume on the maximum oil‑gas pressure difference，as well as the impact of hydraulic oil compressibility on the p-V curve，were analyzed.The results show that as the make‑up oil volume increased from 0.2% to 1.2%，the maximum oil‑gas pressure difference in the first stage increased by 2.9 MPa，and in the second stage by 2.2 MPa.The compressibility of the hydraulic oil significantly affects the compressor suction volume，while it has a smaller impact on the indicated work per unit suction volume.When considering the compressibility of the hydraulic oil，the first‑stage suction volume of the 90 MPa diaphragm compressor decreased by 4.29%，and the second‑stage suction volume decreased by 19.6%.This research can provide a theoretical basis for the design of diaphragm compressors with high reliability and volumetric efficiency.

To address the issues of low reliability and poor flexibility associated with existing refueling hose connection schemes，a set of adaptive rotating devices for rotary pipelines was developed.A rotary dynamic sealing scheme suitable for aerospace fuel media was established，which solves the dynamic error compensation problem encountered during the operation of large‑diameter multi‑channel cylindrical sealing rotary devices.Simulation analyses were performed on structural motion，external flow erosion，and internal flow fields，and static and dynamic tests of the device were designed and conducted according to actual service conditions.The results show that no interference was observed within the full 0°~180° rotational range.The structural safety factor of the device under gas flow erosion ranges from 5 to 10，and the maximum flow velocity in both channels of the internal flow field does not exceed 4.5 m/s.Parameters such as the structural strength of the adaptive rotating device and internal flow velocity all meet the specified standard requirements.By adjusting the valve opening，the system can realize full‑flow regulation from 300 L/min to 1 500 L/min.At a flow rate of 1 500 L/min and an upstream pump pressure of 0.2 MPa，the pressure difference across the device is 0.207 MPa.The local pressure drop variation during fuel passage does not affect the pump's operating point，which remains within the high‑efficiency region.The device can be successfully applied to the construction and upgrading of existing refueling pipeline interface systems.This study can provide a new solution for similar problems in the industry.

In order to improve the sealing performance of the CO₂ slant disc axial plunger pump distribution pair，a spiral groove dynamic pressure hole was opened on the surface of the rotating cylinder of the plunger pump.The sliding mesh transient numerical simulation technology was used to compare and analyze the sealing performance of the planar distribution pair liquid film and the spiral groove distribution pair liquid film.The results show that compared with the unopened planar liquid film，the leakage volume of the spiral groove‑type distribution pair liquid film is significantly reduced，with the leakage volume reduction of 34.17%.The flow velocity of the liquid film area near the waist groove in the high‑pressure zone is higher，which is the main area of leakage.While in the liquid film area near the waist groove in the low‑pressure zone，the fluid only flows in the liquid film，and almost no fluid flows out，and the leakage can be negligible.The volume of leakage to the plunger pump housing side is the largest，accounting for approximately 61.5%，followed by the amount of leakage to the pump shaft，accounting for approximately 35.99%.The volume of leakage to the waist groove side of the low‑pressure area is the smallest，accounting for approximately 2.51%.Driven by the rotation of the spiral groove，the periodic extrusion fluid produces a dynamic pressure effect，the opening force of the liquid film becomes larger，and the dynamic pressure effect of the spiral groove‑type dispensing pair liquid film is stronger.The research results can provide a reference for the optimization of the sealing performance of the distribution pair.

To improve the energy efficiency of high‑pressure water jets in ship rust removal operations，a high‑pressure gas‑liquid mixed jet nozzle was designed.Numerical simulation of the designed nozzle structure was conducted using LES and VOF methods.A comparative analysis was performed on the jet flow velocity，liquid phase distribution，liquid phase interface，and pressure on the impact target surface with and without aeration.Nozzle derusting experiments were carried out to verify the influence of the aeration process on jet performance.The results indicate that the aeration process significantly affects jet characteristics.By entraining air，momentum exchange occurs within the jet，enabling it to maintain a higher flow velocity in the throat.Under a water jet pressure of 195 MPa，the average flow velocity in the throat is approximately 400 m/s.Simultaneously，the aeration process promotes jet breakup into discrete droplets within the throat，forming a high‑energy gas‑liquid mixed jet that enhances the jet impact pressure.The maximum instantaneous impact pressure reaches 317.7 MPa，and the average impact pressure reaches 165.8 MPa，representing a 30.8% increase compared to the average impact pressure generated by a free jet.Compared to the inlet pressure，the average impact pressures of the aerated jet and the free jet decreased by 15.0% and 35.0%，respectively.This demonstrates that the aeration process helps reduce the attenuation of jet impact pressure.Under the premise of achieving the same impact effect，the aerated jet can reduce equipment operating pressure to some extent，which is beneficial for improving equipment reliability.Experimental results further validate the performance of the aerated jet nozzle.The findings provide guidance for the engineering application of aerated jets.

To address the issue of degraded insulation performance and non‑uniform temperature field on the outer wall of cryogenic vessels due to flow field reconstruction on the outer surface induced by environmental wind speed during the application of vacuum multi‑layer insulation （MLI），a heat transfer model for a high‑vacuum multi‑layer insulation fast‑fill cryogenic vessel was established.The influence patterns of wind speed conditions on the vessel's temperature distribution characteristics and insulation performance were systematically analyzed.By employing a layer‑by‑layer numerical iterative algorithm for heat transfer，the heat transfer characteristics of each insulation layer within the MLI were revealed，clarifying the changes in the heat transfer mechanism of the multi‑layer insulation structure under different wind speeds.The research results indicate that within the wind speed range of 0~5 m/s，radiative heat transfer within the MLI significantly increases with higher wind speeds，leading to a noticeable rise in the outer wall temperature of the cryogenic vessel，with a 42% increase in specific heat flux.When the wind speed exceeds 5 m/s，the changes in temperature and heat leak tend to level off.At this stage，radiative heat transfer accounts for more than 50%，becoming the dominant heat transfer mechanism.This study provides a theoretical basis and technical support for the non‑destructive testing of heat leak in cryogenic vessels and their installation site selection.

The fluid dynamic pressure wavy‑tilt‑dam mechanical face seal has become a key component ensuring the long‑term stable operation of nuclear main pumps due to its controllable leakage，stable performance，and high reliability.This paper systematically reviews the research progress of fluid dynamic pressure wavy‑tilt‑dam mechanical seals for nuclear main pumps both domestically and internationally.Although relevant research in China started relatively late，driven by the national nuclear power development strategy，domestic research has achieved a transition from following to running in parallel with international efforts.Concurrently，advancements in computational technology have deepened the study of seal friction and lubrication theory.At present，theoretical models for wavy‑tilt‑dam face seals primarily focus on three major subjects：the fluid characteristics of the liquid film，the fluid‑structure interaction between the seal face and the liquid film，and the interaction between the seal ring and the fluid medium.The research paradigm is expanding from single‑physics‑field analysis to multi‑physics‑field coupling simulations.Existing research has been reviewed and summarized from three core perspectives：the design of the fluid film wavy shape，the mechanism of hydrodynamic lubrication，and the collaborative deformation of friction pair components.On this basis，optimization suggestions for future research are proposed：establishing a composite topography fluid film model incorporating roughness and wavy‑tilt‑dam characteristics；developing a hydrodynamic lubrication theory applicable to the coexistence of mixed lubrication and hydrodynamic lubrication；and conducting in‑depth research on the multi‑component collaborative deformation laws specific to nuclear main pump operating conditions，aiming to provide theoretical references for the design and engineering application of high‑performance seals.

With the advancement of electrification and intelligent technologies，higher demands have been placed on human‑centric air conditioning systems.Based on image recognition technology，a deep learning model using ResNet50 as the backbone network and incorporating a spatial attention module （Attention-ResNet50） was constructed for human‑centric air conditioning systems.By collecting infrared image data under different thermal comfort conditions and classifying them into three categories，cold，comfort，and hot，for training and testing，this method significantly improved prediction accuracy.Experimental results showed that the introduction of the spatial attention mechanism increased the overall model accuracy by approximately 5%.The best model accuracy exceeded 94% for male subjects and surpassed 96% for female subjects.The study confirms the effectiveness of the attention mechanism in feature extraction，providing a reliable and universal technical pathway for personalized thermal comfort control.

To address the issue of pressure overshoot during the reversing process of piston pumps，experimental tests and numerical simulations were conducted using coal slurry with a solid concentration of 68.5% as a case study.Cyclic pumping experiments were carried out under two pressure conditions，and the results were compared with numerical predictions.The study revealed that as the distance from the pipeline inlet increases，the rate of decrease in pressure overshoot accelerates，while the overshoot ratio gradually rises.For instance，at a steady‑state transport pressure of 5.17 MPa，the experimental overshoot ratio increased from 11.9% at the inlet to 15.23% near the outlet.Near the pipeline inlet，both maximum velocity and steady‑state velocity demonstrate minimal changes with distance，but beyond a certain point，the maximum velocity incrementally rises.Furthermore，the velocity overshoot at measurement point 11^# under the two conditions is 66.9 mm/s and 17.3 mm/s，with overshoot ratios of 1.53% and 0.43%，respectively.The variation in overshoot magnitude was more pronounced than that of the velocity itself，with the transport velocity differing by 9.5%，while the overshoot ratio differed by as much as 255%.The findings provide valuable insights for optimizing the pumping strategy and the design of coal slurry pipeline systems.