In response to challenges in monitoring the full‑life degradation state of dry gas seals and insufficient research on vibration signals，a condition monitoring method for dry gas seals based on vibration acceleration signals is proposed.Through dynamic analysis and COMSOL simulation，the mechanism of sealing performance degradation caused by the reduction in dynamic pressure groove depth is revealed.A dry gas seal test rig is built to collect vibration acceleration data under different rotational speeds （1 000~2 500 r/min），pressures （0.15~0.25 MPa），and groove depths （8，6，4，2 μm），simulating the full‑life degradation process.A condition monitoring model based on support vector data description （SVDD） is established.This model trains hypersphere parameters using healthy data to enable online detection of degraded data.The results show that the root mean square （RMS） value of axial vibration acceleration at a groove depth of 2 μm increases significantly compared to that at 8 μm.Within a certain parameter range，the RMS value of axial vibration acceleration is positively correlated with rotational speed and negatively correlated with pressure and groove depth.The SVDD model can identify degradation trends at an early stage （groove depth of 6 μm），enabling failure warning.This study provides technical support for the intelligent monitoring and health management of dry gas seals.

To address the common failure caused by erosion‑thinning and perforation in industrial pipelines，a rapid prediction and simulation study on erosion damage in tee reducing pipes was carried out based on the POD‑Kriging reduced‑order model.The results show that the established reduced‑order model improves the efficiency of numerical simulation by three orders of magnitude，with the prediction error of erosion damage controlled at approximately 4%.Regularly selected design points can significantly enhance prediction stability，yielding a relative mean absolute error （RMAE） of erosion rate of 2.1%，whereas irregular design points cause the error to surge to 86.6%.Optimization of the number of modes is critical for capturing complex erosion characteristics，and the error decreases to 4.1% when 9 modes are used.The number of design points should be matched coordinately with the number of modes；increasing both simultaneously enables effective capture of the multi‑parameter coupling effect，reducing the erosion rate prediction error from 28.3% to 4.1%.The proposed model provides important support for erosion location prediction，digital inspection and monitoring，as well as damage prevention and control of pressure pipelines.

To address the vibration over‑limit issue of a horizontally split multistage pump in the water intake system of a coastal city's pipeline network，vibration velocity testing and spectrum characteristic analysis were carried out using the LMS testing and analysis system.The results showed that the peak vibration velocity in the vertical direction at the non‑drive end of the pump reached 13.8 mm/s，far exceeding the limit specified in the GB/T 29531—2013 standard，posing a serious challenge to the safety and stability of the equipment.To accurately identify the root cause of the fault，a quantitative risk assessment of potential failures was conducted based on the failure mode and effects analysis （FMEA） method.Through failure mode identification，risk priority number （RPN） calculation，and screening of key fault factors，pump shaft misalignment and rotor‑stator interaction between the impeller and casing were determined to be the core causes of the excessive vibration.Accordingly，improvement measures including high‑precision shaft alignment correction，impeller hydraulic profile optimization，and clearance matching adjustment were proposed and implemented.After the improvements，the dominant vibration frequency of the pump was effectively shifted.The dominant frequency amplitudes in the horizontal and vertical directions at the non‑drive end were reduced by 52.6% and 51.5%，respectively.The vibration severity met the operational requirements for Class Ⅱ equipment specified in the GB/T 29531—2013 standard，and the equipment operating condition was significantly improved.This study provides a reference for the accurate diagnosis and efficient treatment of vibration faults in fluid machinery equipment，and holds important engineering application value for ensuring the reliable operation of urban pipeline network water intake systems.

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.