In order to explore the feasibility of efficient rock breaking and cavitation by abrasive jets with conical nozzles，abrasive jet cavitation tests were carried out.A visualization experimental method based on digital image correlation （DIC） was adopted to study the distribution characteristics of the strain field in horizontal well cavity completion.Combined with the finite-discrete element method （FDEM），the morphological characteristics of cavitation‑induced fractures and the evolution process of stress in cavity completion were characterized.The effects of cavity diameter and in‑situ stress on the stress evolution and fracture extension of the cavity in coalbed methane （CBM） horizontal wells were investigated.The research results show that under the condition of submerged jet，the abrasive jet with a conical nozzle can penetrate a coal body with a length of 62 cm within 30 s under a pressure of 25 MPa and produce a volume‑breaking effect.With the increase of vertical stress and cavity diameter，the strain localization zones increase significantly，and the strain localization zones distributed vertically gradually appear.Natural fractures are the main factor affecting the damage degree of coal rock plates.Stress concentration occurs first around the cavity，and then cracks initiate at the intersection of the bedding/cleat weak planes and the cavity.When the vertical stress is greater than the horizontal stress，a fracture network is more likely to be formed，thus inducing stress release.The research findings provide a theoretical basis for the stress release mechanism of cavity completion in CBM horizontal wells.

To achieve the control objective of “on‑demand defrosting” for heat exchangers，a frost performance test rig was constructed.Image recognition technology was employed to study frost characteristics of finned heat exchangers under different face velocities，and changes in refrigeration capacity during dynamic frosting were analyzed.Results show that within a 1 h test period under identical air inlet temperature and humidity conditions：As wind speed increased from 0 m/s to 1 m/s and 2 m/s，frost accumulation gradually decreased.Frost blockage rates were 88.99%，74.93%，and 39.88%，with frost thickness at fin tips measuring 1.169 mm，0.729 mm and 0.321 mm respectively.Higher wind speeds reduced frost blockage rates，enhancing heat transfer capacity and increasing system refrigeration capacity.Lower wind speeds increased frost blockage rates，degrading heat transfer capacity and reducing refrigeration capacity.This study provides theoretical and technical support for achieving “on‑demand defrosting”.

To address the dual challenges of high building energy consumption and increasing occupant comfort demands，a direct‑condensation capillary radiant floor heating terminal was designed.A refrigerant direct‑condensation floor heating air‑source heat pump system was constructed in an environmental chamber.Temperature characteristics of the heating terminal and heat pump heating performance variations under different outdoor temperatures were investigated，with comparative analysis against bare‑tube capillary radiant terminals.Results show that under varying outdoor temperatures，bare‑tube capillary walls heat faster than capillary walls under cement layers.Cement floor surface temperature stabilization lags behind capillary wall temperature stabilization.At 0 ℃ outdoor temperature，the temperature difference between exhaust and subcooled sections of bare‑tube capillaries is only 1.6 ℃，whereas for cement floors it reaches 4.4 ℃.At -10 ℃ outdoor temperature，the cement‑embedded capillary floor system achieves heating capacity of 1.67 kW and COP of 4.20，representing 21.6% and 13.9% decreases compared to bare‑tube capillary terminals.This study provides reference for designing capillary radiant floor heating systems.

Aiming at the issue of excessively high pressure pulsation amplitude in a certain centrifugal pump，a steady‑state numerical simulation method was employed to analyze the internal flow field of the pump，and a design for locally thickening the middle section of the impeller blades was proposed.This design is intended to adjust the internal flow field of the pump，enhance the uniformity of the circumferential energy distribution at the impeller outlet，and thereby reduce pressure pulsation.Steady‑state and unsteady‑state numerical simulations were conducted on the centrifugal pump before and after the improvement.The pump before improvement was also subjected to hydraulic performance tests，the head is 23.4 m at design flow rate which is 120 m³/h.The pump characteristic curves obtained from the tests were consistent with those from the steady‑state numerical simulations.Comparing the numerical simulation results of the centrifugal pump before and after the improvement.The difference between the simulated heads of the two impellers is only 0.3 m，and the difference of the best efficiency is less than 1%，and the best efficiency point of the improved impeller is shifted from 130 m³/h to 120 m³/h compared to the prototype impeller.It is found that the improved impeller with the design of locally thickening the middle section of the blades has hydraulic performance close to that of the prototype impeller.Moreover，the improved impeller exhibites a more uniform circumferential energy distribution at the outlet compared to the prototype impeller.The blade frequency pressure pulsation amplitude at the monitoring points within the pump is reduced by 16.4% to 49.4% relative to the prototype impeller，and the overall level of pressure pulsation intensity within the pump also decreases.The comparison results indicate that the design of locally thickening the impeller blades can help reducing the pressure pulsation within the pump，thereby suppressing pump vibration.The blade local thickening design involved in this study can serve as a reference for the improvement of other centrifugal pumps that require reduced pressure pulsation.

To address the inadequacy of conventional stem packing seal ring and clearance design methods for high‑pressure ball valves，this study investigates internal flow characteristics and sealing structures based on the configuration and mechanical behavior of high‑pressure hydrogen ball valve packings.The effects of graphite packing height，compression ratio，friction coefficient，and clearance on stem sealing performance were examined.Results show that during valve closure，the maximum flow velocity （32.4 m/s） occurs at the spool channel outlet.At the fluid‑solid interface of the packing ring，pressure fluctuation is 13 700 Pa with flow velocity ranging 0~4 m/s，negligible for sealing design，while compression ratio and clearance significantly impact sealing performance.Increased friction coefficient enhances contact pressure but accelerates seal ring wear.Optimized parameters were determined：total height 20 mm，clearance 0.1 mm，compression ratio 22%，friction coefficient 0.1.A stem sealing test rig verified leak‑free performance under room temperature and 45 MPa high pressure，confirming design reliability.This study provides reference for designing stem packing seals in high‑pressure ball valves.

To investigate the effects of ice slurry flow velocity，inlet ice concentration，and ice crystal size on the cooling storage period of ice storage tanks，a dynamic ice slurry storage model was established and experimentally validated.Experimental and simulation studies examined dynamic ice slurry cooling storage characteristics in open ice storage tanks.Results show that at an ice crystal size of 0.8 mm，the maximum cooling storage capacity corresponds to an ice concentration of 29.5%，with the ice‑rich layer extending to the tank bottom.Increasing slurry velocity and inlet ice concentration significantly shorten the cooling storage period：when inlet velocity increases from 0.5 m/s to 0.9 m/s，the period reduces by approximately 41%；when inlet ice concentration rises from 1% to 3%，the period shortens by about 66%，and from 5% to 9%，by approximately 42%.Considering ice blockage risks during transportation，using 5%~7% inlet ice concentration and 0.5~0.7 m/s inlet velocity ensures economically effective short storage periods.For identical cooling capacities，ice crystal size negligibly affects the storage period.These findings provide theoretical reference for ice slurry cooling storage system operation and power regulation response applications.

Aiming at the problem of reduced ventilation efficiency due to wear and tear caused by dust particles eroding the blade surface in dusty environments，this paper carries out a study on the dynamic prediction of erosion and wear of axial fan airfoil segments.By simulating the erosion process of the three‑dimensional airfoil section of the fan under the action of gas-solid two‑phase flow，the dynamic evolution process of dust particles eroding the surface of the straight airfoil section was studied，and the changes in the wear morphology of the airfoil surface under different incoming flow velocity conditions and their effects on aerodynamic performance were analyzed.The research results show that with the progress of erosion time，the cumulative effect of erosion and wear on the leading edge of the airfoil surface is significant，the degree of wear of particles on the airfoil surface gradually increases，and the depth of erosion pits continues to increase.When the relative velocity between dust and the airfoil surface is 25 m/s and the erosion time reaches 80 h，the maximum erosion depth on the airfoil surface approaches 1 mm.The change in the wear morphology of the airfoil surface causes fluctuations in the pressure coefficient and disorder in the static pressure on the airfoil surface.In addition，with the increase in incoming flow velocity，the position where flow separation occurs on the suction surface gradually moves backward，and the flow in the near‑wall region tends to be unstable.The research results can provide a scientific basis for the optimization of fan design and the improvement of its durability in harsh environments.

To address the performance deficiencies of a molten salt pump in a 50 MW solar thermal power plant and the low flow efficiency of its flow components，the space guide vane was selected as the research subject for multi‑objective optimization design.Principal component analysis identified geometric parameters of the guide vane，determining five significant geometric parameters affecting pump performance as optimization variables：maximum outer streamline diameter of guide vane （D₂），guide vane inlet angle （α₁），guide vane outlet angle （α₂），guide vane blade wrap angle （φ），and radial installation clearance between impeller and guide vane （L₂）.Support vector regression combined with RBF neural network established surrogate models between pump efficiency，head，and optimization variables.Model accuracy was analyzed by R² method （>0.95），meeting error requirements.MOEA/D algorithm optimized geometric parameters，obtaining optimal values for the guide vane.Engineering design produced optimized guide vane prototypes.Comparative analysis examined performance impacts before and after optimization.Results show optimal parameters：D₂=451 mm，a₁=21.2°，a₂=88.1°，φ=94.5°，L₂=4.5 mm.After optimization，pump head increased by 4.98%，efficiency by 4.32%.Hydraulic performance improved significantly：pressure gradient transitions became smoother，dynamic‑static pressure energy conversion efficiency increased，flow separation vortex intensity and size reduced noticeably，hydraulic losses decreased，and flow characteristics improved substantially.This study provides reference for molten salt pump optimization design.

Aiming at the issues of complex structure and poor self‑sealing in traditional positive displacement pumps，a double‑acting five‑blade scraper pump was designed.Using the up‑and‑down scrapers to replace the reciprocating vanes found in traditional vane pumps，creating a novel non‑valved，compact fluid power device.Based on the 2.5D dynamic grid coupled viscous wall strategy and experimental testing，a fluid-solid coupling analysis was conducted on a double‑acting five‑blade scraper pump.The stress distribution and deformation distribution characteristics of the rotor scraper under pressure load were obtained under the influence of flow field characteristics，as well as the modal characteristics of the rotor scraper.The results indicate that the fluid-solid coupling significantly affects the structure of the rotor‑scrapers.The stress and deformation of the rotor scrapers decrease with the increasing of rotational speed.Specifically，with the rotational speed increased from 900 r/min to 2 700 r/min，the maximum equivalent stress decreases by 24.56%，and the maximum deformation decreases by 13.79%.The vibration frequency of rotor and scraper under different load pressure has no obvious change，and the wet mode vibration frequency is slightly lower than that under fluid-solid coupling.This study provides valuable insights into the structural optimization and design of double‑acting five‑blade scraper pumps.

To enhance the heat transfer efficiency of heat exchangers，a synergistic method combining helical twisted tapes with nanofluids is proposed，and the thermal performance of this composite enhancement approach is investigated.Using Al₂O₃‑H₂O nanofluid as the working medium，key thermophysical properties （density，specific heat，viscosity，and thermal conductivity） are calculated based on classical nanofluid models.A 3D numerical model is established via computational fluid dynamics （CFD） to simulate flow and heat transfer characteristics in heat exchange tubes with inserted twisted tapes，validated against experimental data from literature （maximum relative error：10.9%）.Comparative analysis shows that the composite nanofluid‑twisted tape configuration increases the surface heat transfer coefficient by 35.18% compared to the plain tube with pure water，albeit with a 576 Pa pressure drop increase.The study reveals coupling effects of nanoparticle volume fraction and mass flow rate：as the volume fraction rises from 0.5% to 4%，the Nusselt number （Nu） decreases from 57.1 to 51.5 due to viscosity‑induced convection suppression.When mass flow increases from 0.1 kg/s to 0.4 kg/s，the Nu number enhancement of twisted tape tubes over plain tubes expands from 4.3% to 11.7%，demonstrating synergistic mechanisms between secondary flow and nanoparticle thermal transport under high‑flow conditions.These findings provide theoretical support for designing high‑efficiency heat exchangers.

Industrial decarbonization is a critical challenge for China as it strives to achieve the "carbon peak and carbon neutrality" goal.While current research efforts on industrial decarbonization primarily concentrate on the supply side，there is a notable scarcity of investigations on the demand side，despite it constituting nearly 30% of the total industrial energy consumption，specifically for producing industrial steam.This significant proportion underscores the importance of directing attention towards the demand side as a key aspect of industrial decarbonization endeavors.Steam generation heat pumps emerge as a promising alternative for achieving decarbonization in the industrial sector due to their ability to substantially enhance energy quality in meeting the demands for industrial steam.This study provides an overview of the existing research landscape on steam generation heat pumps both domestically and abroad.Furthermore，it puts forth recommendations for future research directions relating to improving system efficiency and raising output temperatures.The results show that the prediction of the properties of high‑temperature mixed refrigerants using artificial intelligence and neural networks will be a pivotal focus area.Additionally，enhancements to refrigerant compressors through innovations such as new profile combinations，sealing structures，as well as advancements in axial force balance mechanisms for scroll compressors and innovative sealing methods for piston compressors are suggested.Moreover，optimizing screw compressor geometrical parameters，operational conditions，system structures，and drive configurations will form the primary research trajectory for refrigerant compressors.In the realm of water vapor compressors，the proposed research endeavors entail reducing exhaust temperatures in centrifugal compressors，developing cost‑effective high‑performance blades，implementing precise water spray controls for screw compressors，and enhancing system reliability through design improvements.

To meet the requirements for stable operation monitoring and safety early warning of 90 MPa diaphragm hydrogen compressors used in hydrogen refueling stations，a self‑learning monitoring and early warning method based on a clustering matrix was proposed.Initially，a moving window method with a window length of 10 was used to group the monitored operational conditions in time series.Then，12 combined statistical indicators were employed to mine the implicit information from 18 monitored parameters.Subsequently，a clustering matrix algorithm was constructed to model and identify the states of the selected 10 monitored parameters.Combining expert experience，a weight matrix was established based on accuracy，recall rate，and time consumption.Considering the long‑term and variable operational characteristics of hydrogen compressors，KL and JS divergences and KS tests are introduced to construct a self‑updating strategy，with thresholds set at 1.0 and 0.3 and a significance level of 0.05.The experimental results show that for over 8 000 data sets in iterative testing，the model's average accuracy recovers from a low of 66.75% to 94.87%，and the average recall rate improves to 90.64%，with a total core computation time of 111.37 s，validating the model's self‑updating capability and sensitivity to data from different operational distributions.This study provides support for the full lifecycle monitoring and early warning of diaphragm hydrogen compressors.

To address the insufficient digitalization and intelligence of pumped storage units during operation，as well as the long computation time of existing simulation software that fails to meet real‑time requirements for digital twin systems，this study proposes a digital twin‑based solution to enhance monitoring and prediction capabilities for pump‑turbines.A reduced‑order model was established using proper orthogonal decomposition （POD） and integrated into the system via the FMI protocol，achieving visual interaction through Open3D point cloud with the entire process taking only 728.6 milliseconds.Simultaneously，a pressure pulsation prediction model based on long short‑term memory （LSTM） networks was developed for operational condition forecasting，with prediction accuracy exceeding 96%.Additionally，a complete digital twin system was developed using the Unity3D platform and validated for effectiveness and feasibility.This research provides a novel solution for the digitalization and intelligence of pumped storage units，holding significant implications for the intelligent upgrade and modern transformation of the hydropower industry.

To address the characteristic that dry gas seal acoustic emission signals are susceptible to background noise interference，a denoising method based on complete ensemble empirical mode decomposition with adaptive noise （CEEMDAN） and adaptive collaborative wavelet threshold filtering is proposed.CEEMDAN decomposes the dry gas seal acoustic emission signal to obtain a series of intrinsic mode function （IMF） components.Based on the weak correlation of IMF components containing higher noise，an autocorrelation attenuation indicator is constructed to automatically screen noise‑contaminated IMF components.Wavelet threshold denoising processes the noisy components，which are then reconstructed with the remaining components to obtain the denoised signal.Validation using simulated signals and experimentally acquired real dry gas seal acoustic emission signals shows that，compared with conventional wavelet threshold denoising methods，the signal‑to‑noise ratio （R_SN） increases by an average of 4.91 dB，and the root mean square error （E_RMS） decreases by an average of 44%.Compared with methods without autocorrelation attenuation‑based IMF screening，R_SN increases by an average of 0.45 dB，and E_RMS decreases by an average of 4.8%.After denoising，the peak characteristic frequencies in the spectrum of real acoustic emission signals become clearer，with significant background noise removal.This study provides support for dry gas seal fault prediction and health management technologies.