To efficiently produce ice particles of targeted sizes for ice air jet applications，ice particles were generated using a direct contact cryo genic settling method.The effects of water flow rate （Q） and atomizing‑nozzle exit diameter （D） on the particle size distribution were systematically investigated. In addition，the atomization behavior and solidification heat transfer characteristics were analyzed using the Weber number （We），Stefan number （St），and Biot number （Bi）.The results show that the atomization process is jointly governed by D and Q.At a fixed flow rate，increasing D reduces the exit velocity and the diameter ratio （d/D），shifting the atomization mechanism from inertia‑dominated breakup to a surface‑tension‑dominated regime.At a fixed nozzle diameter，increasing Q drives the atomization mode from a transitional regime toward inertia‑dominated breakup.During solidification，sensible‑heat transfer is dominant.Internal conduc‑tion resistance is non‑negligible，while external convection remains an important limiting factor.Small ice particles，with large specific surface area and low internal temperature gradients，exhibit faster solidification，whereas large particles suffer from delayed core cooling，which significantly prolongs the phase‑change time.Ice particles produced using nozzles with D=2.5~3.5 mm exhibit a circularity close to 1，indicating favorable wear performance.The optimal operating parameters are identified as D=3.0 mm and Q=0.02 L/s. This study elucidates how process parameters govern ice‑particle size and heat‑transfer characteristics，providing theoretical support for the optimized design and engineering implementation of ice‑particle jet technologies

To address the challenges of limited downhole space in single‑well injection‑production systems and the difficulty in efficiently separating small‑diameter oil droplets from oil‑water mixtures，miniature hydrocyclones with better separation performance for small oil droplets were selected.Combining computational fluid dynamics （CFD） numerical simulation and experimental methods，the effects of produced fluid physical parameters and operational parameters of miniature hydrocyclones on downhole oil‑water separation performance were analyzed，and their adaptability under different conditions was investigated.The results show that when the oil concentration in the produced fluid is set to 2%，5%，8%，10%，and 13%，the corresponding optimal overflow split ratios are 20%，23%，26%，28%，and 31%，respectively；when the oil density is 800 kg/m³，the miniature hydrocyclone demonstrates good separation performance across the oil concentration range of 2% to 13%；when the oil density is 850 kg/m³ and 900 kg/m³，the optimal adapted produced fluid oil concentration ranges for the miniature hydrocyclone are below 8% and below 5%，respectively.This study can provide references for the efficient application of miniature hydrocyclones in downhole oil‑water separation.

To improve the energy efficiency of new energy vehicle air conditioning systems，educe their heating energy consumption，and lower the global warming potential （GWP） and ozone depletion potential （ODP） of the refrigerant，a performance test system for a new energy vehicle R290 compressor was established.Experimental studies were conducted on the effects of charge amount and system parameters on the oil circulation rate （OCR），and the influence of OCR on the performance of the R290 compressor.The results indicate that the system oil charge amount significantly affects the system OCR，showing an exponential increase.The optimal operating range for OCR is 2% to 10%.For every 10 ℃ decrease in evaporation temperature，the OCR decreases by approximately 3%，while for every 5 ℃ increase in condensation temperature，the OCR decreases by about 1.5%.The condensation temperature has a greater influence on OCR than the evaporation temperature.The cooling capacity increases with higher oil content；the nominal cooling capacity is greater than the actual cooling capacity，and the cooling capacity attenuation rate also increases.At a compressor speed of 3 600 r/min，when the OCR is around 5%，the cooling capacity attenuates by approximately 8.0%，whereas when the OCR is around 10%，the cooling capacity attenuates by about 13.5%，but the actual cooling capacity increases by approximately 3.5%.As the compressor speed increases，the isentropic efficiency increases while the discharge temperature decreases.When the oil circulation rate increases from 5% to 10%，the compressor discharge temperature decreases by about 5 ℃.Appropriately increasing the compressor speed，lubricant charge amount，evaporation temperature，or lowering the condensation temperature is beneficial for improving compressor operating performance and ensuring stable operation.This study provides a reference for the optimal design of new energy vehicle air conditioning systems.

To address the issues of large footprint and low thickening efficiency in traditional tailings thickening equipment in the mining sector，a vertical separator utilizing spiral flow channels to enhance particle migration and sedimentation is proposed for tailings concentration，aiming to improve tailings thickening performance.Using underflow concentration and overflow concentration as evaluation metrics，experimental studies were conducted to investigate the effects of flocculant dosage，flow rate，and split ratio on the separator's thickening performance.Response surface methodology （RSM） was employed to optimize the operational parameters，and further investigations were carried out to examine the impact of inlet concentration and the presence or absence of blades on separator performance.The results show that under conditions of a tailings median particle size of 13.5 μm and an inlet concentration of 20%，the optimal operational parameter combination is an inlet flow rate of 3.509 L/min，a split ratio of 0.244，and a flocculant dosage of 29.9 g/t.At these settings，the underflow concentration reached 65.46%，and the overflow concentration was 282.9 mg/L，representing a 5.76% increase in underflow concentration compared to the initial value of 59.7%.The group with blades exhibited a 19.92% higher underflow concentration （45.54%） compared to the group without blades.The findings provide insights and references for the development and application of novel compact and efficient slurry thickening equipment.

To address the aerodynamic noise issue in axial flow fans caused by tip leakage flow，a noise reduction structure combining “bionic serrations-suction surface tip winglet modification-multi‑scheme grooving” was designed.Using the SBES（stress‑blended eddy simulation） turbulence model coupled with the FW-H acoustic analogy method，the noise reduction mechanisms of each structure were analyzed.The results show that the combination of a biomimetic wavy leading‑edge serration with a suction side tip winglet modification can reduce the overall sound pressure level by 4.5dB.Further combining this with a tip longitudinal airfoil ribbed slot structure leads to a reduction of 7.9dB in the overall sound pressure level.The biomimetic leading‑edge serration-suction side tip winglet modification reduces the discrete noise peaks by disrupting the periodic shedding of leakage vortices，optimizes the flow uniformity at the tip，and suppresses abrupt local pressure fluctuations.The combined structure of biomimetic leading‑edge serrations，tip longitudinal airfoil ribbed slots，and suction side tip winglets accelerates vortex energy dissipation by dynamically dividing the leakage flow paths.In experiments，the prototype demonstrated significant noise reduction effects，and the observed phenomenon of “low‑frequency noise energy shifting to high frequencies” was consistent with the numerical simulation results，verifying the reliability of the proposed method.This study provides a reference for the optimization design of low‑noise axial flow fan tips.

In response to the insufficient research on existing stratified injection nozzles regarding the “large diameter+strong throttling” structure，as well as the complexity of multi‑component injection conditions involving CO₂，N₂，and CH₄ and the unclear flow characteristics of the nozzles，this study proposes applying the Helmholtz nozzle to stratified injection.A real gas flow model considering the variation of multi‑component fluid properties with temperature and pressure was established.The flow characteristics and influencing laws of the nozzle under different component concentrations，nozzle contraction section diameters，and confining pressures were investigated.The results show that under the same volumetric flow rate，the throttling pressure drop of the Helmholtz nozzle significantly decreases with a reduction in CO₂ mass fraction.Compared to the pure CO₂ control group，when the mass ratio of CO₂，N₂，and CH₄ is 0.34∶0.42∶0.24，the throttling pressure drop reduction can reach 69.56%.The jet temperature is significantly affected by the CO₂ mass fraction.Compared to the pure CO₂ control group，when the mass ratio of CO₂，N₂，and CH₄ is 0.65∶0.25∶0.10，the temperature drop increase can reach 40.56%.Under high confining pressure conditions，a high throttling pressure drop and a smaller temperature drop can be achieved.The relationship between the throttling pressure drop and the nozzle contraction section diameter exhibits an inflection point.Under specific nozzle diameter combinations，a multi‑stage throttling effect can be achieved，enabling adaptive transfer and adjustment of the throttling effect while maintaining high flow capacity.Therefore，the feasibility of using the Helmholtz nozzle as a stratified injection nozzle is high.The research findings can provide a theoretical basis for the structural design of downhole stratified injection tools and the optimization of gas injection process parameters.

To address the issue that traditional plunger‑type melt three‑way directional valves cannot meet the process requirements for discharge switching at the outlet of the final polymerization reactor in nylon 66 continuous polymerization units，a novel self‑lift plug‑type melt three‑way directional valve has been developed.The structural principles of this final polymerization reactor outlet three‑way valve were analyzed，and calculations and verifications were performed for the valve body wall thickness，the thrust required by the actuator for sealing between the plug and valve seat，and the assembly interference required for sealing between the valve seat and valve body.This valve features outstanding performance characteristics such as compact structure，small overall dimensions，excellent melt flow adaptability，reliable sealing，and fast，flexible directional switching.The results show that with a unilateral assembly interference of 0.175 mm for the valve seat，the unilateral interference can reach 0.270 mm under design temperature，with an interface pressure of 75.70 MPa and a high‑viscosity melt sealing safety factor of 2.44.Industrial applications demonstrate that the structural design of the final polymerization reactor outlet three‑way directional valve is reasonable，its high‑temperature sealing performance meets the GB/T 13927—2022 Class A sealing requirements （no visible leakage），online switching is fast and smooth，and the mean time between failures （MTBF） is ≥12 months.This research provides a reference for the improved design of three‑way directional valves.

To investigate the influence of pile‑soil parameters on the thermo‑mechanical coupling characteristics of energy pipe piles with phase change materials，a combined method of 3D numerical simulation and experimental validation was adopted to analyze the effects of heat exchange tube form，pile material，soil type，and layered conditions.The results show that the heat exchange capacity per unit pile depth follows a descending order for coaxial pipe，double U‑tube，and single U‑tube heat exchangers，measuring 81，71.44，54.51 W/m，respectively，at the end of operation.The coaxial pipe configuration delays the recovery of the summer phase change material （PCM-S） under long‑term operation，expands the thermal influence zone of the surrounding soil，and intensifies the changes in the mechanical performance of the pile.Different pipe pile materials lead to variations in heat exchange capacity and PCM-S liquefaction rate due to differences in thermal conductivity：during the PCM-S phase change period，C80 exhibits the highest heat exchange，while C100 shows the lowest；after phase change completion，C100 achieves the highest heat exchange （55.77 W/m），and C80 the lowest （54.5 W/m）.The axial force and side friction resistance of the pile are highest for C80，followed by C90，and lowest for C100.Increasing the thermal conductivity of the soil enhances heat exchange performance and reduces the thermo‑mechanical response of the pile.In layered soils，an arrangement with increasing thermal conductivity from top to bottom is most conducive to heat exchange，and high thermal conductivity soil layers accelerate heat diffusion，reducing thermo‑mechanical changes in the pile.This research provides a theoretical basis for the optimal design of pile‑soil parameters in energy pipe piles with phase change materials.

In response to issues such as temperature rise and uneven temperature distribution within the hydrogen pressure reducing valve （HPRV） caused by the Joule-Thomson effect，the relationship between key geometric structure of the HPRV and its internal flow characteristics as well as temperature distribution was investigated.Sixteen reducing valve structures were designed based on the Taguchi method.The flow characteristics inside the valve were numerically analyzed using computational fluid dynamics （CFD），and a valve test platform was built to validate the numerical results.Taking the flow coefficient and temperature distribution uniformity in the control chamber as response indicators，the contribution rates of different geometric parameters were analyzed.The results show that the spool angle θ has the greatest effect on the flow coefficient of the reducing valve，while the control chamber area A_r and the thin pipe diameter D exerts the most significant influence on the temperature distribution uniformity in the control chamber.The optimal combination of geometric parameters is A_r=1 800 mm²，D=2.5 mm，and θ=55°.Compared with other schemes，the flow coefficient of the optimal parameter combination is increased by up to 88.2%，and the uniformity of temperature distribution is reduced by up to 93.2%.The increase of θ and D leads to a rise in the pressure gradient of the main valve core，intensifying the Joule-Thomson temperature rise effect.The fine pipe structure delays the diffusion of low‑pressure hydrogen in the control chamber to the outlet，promoting the uniform distribution of hydrogen temperature in the control chamber.However，variations in the tube diameter do not affect the pressure stabilization characteristics of the control chamber.The study can provide a reference for the design of hydrogen pressure reducing valve.

To investigate the key influencing parameters on the performance of a coupled system of gas boilers and high‑temperature heat pumps（HTHP），an existing gas boiler was retrofitted to establish a boiler‑coupled high‑temperature heat pump experimental platform.The effects of boiler load，circulating water flow rate，and condenser water supply flow rate on system performance were explored.The study shows that within the boiler load range of 35% to 95%，for every 10% increase in load，the flue gas waste heat recovery amount，high‑temperature heat pump outlet water temperature，and heating coefficient of performance （COP） increased by an average of 8.08%，4.72% and 3%，respectively.Under the condition of 90% boiler load and within the circulating water flow rate range of 3 to 11 m³/h，for every increase of 2 m³/h in flow rate，the flue gas waste heat recovery amount and recovery rate increased by an average of 4.86% and 2.06%，respectively，while the high‑temperature heat pump outlet water temperature and COP increased by an average of 3.46% and 3.4%，respectively.Within the condenser water supply flow rate range of 0.5 to 0.7 m³/h，for every increase of 0.05 m³/h in flow rate，the high‑temperature heat pump outlet water temperature decreased by an average of 7.1 ℃.By using the high‑temperature heat pump to raise the condenser water supply temperature from 29.3 ℃ to 123.7 ℃，the high‑temperature heat pump COP reached 3.13，the boiler exhaust gas temperature dropped to 43.5 ℃，and a flue gas waste heat recovery rate of 5.02% was achieved.This study provides a theoretical basis for optimizing the operational parameters of gas boiler‑coupled high‑temperature heat pump systems and facilitates the promotion and application of high‑temperature heat pump products in boiler flue gas waste heat recovery.

Aiming at the problems of low operating efficiency and excessive energy consumption of pumping stations in the oilfield water injection system，taking the oilfield water injection pumping station as the research object，a multi‑objective operation optimization model was constructed with the minimum electricity cost，the maximum average efficiency，the minimum flow deviation degree，and the minimum start‑stop frequency of the pumping station.The third‑generation non‑dominated sorting genetic algorithm （NSGA-Ⅲ） was adopted to solve it for operation optimization.Then，the analytic hierarchy process （AHP） and the weight assignment method based on the correlation between indicators （CRITIC） were combined to assign weights to it.Meanwhile，the near‑ideal solution ranking method （TOPSIS） was introduced to optimize the scheme，achieving comprehensive decision‑making for multi‑objective optimization.The comparative analysis with the original operation scheme of the oilfield water injection pumping station shows that the optimized scheme has achieved remarkable results.The average efficiency of the water pump has increased from 66.99% to 70.31%，the improvement rate reaches 4.96%.The traffic deviation has decreased from 17.32% before optimization to 13.71%，a reduction of 20.8%.Meanwhile，the start‑stop frequency of the water pump has decreased from the original 0.500 to 0.314，a decrease of up to 37.2%.The daily electricity cost has decreased from 22 528 yuan to 20 116 yuan，a decrease of 10.71%.The research can provide a basis for the scientific operation and management of oilfield water injection pump stations.

To address the noise and vibration issues of high‑speed，large‑displacement scroll compressors，a dynamic model of the shaft system was established based on multibody dynamics theory.The force characteristics of the main and auxiliary bearings under high‑speed operating conditions were analyzed，followed by the optimized design of the motor counterweights.Subsequently，whole‑machine vibration tests were carried out for verification.The results indicate that，over the entire speed range of the scroll compressor，the loads on both the main and auxiliary bearings increase with the rise in rotational speed before and after optimization.After optimization，the bearing loads are significantly lower across the entire speed range.Specifically，at 8 000 r/min，the load on the main bearing is reduced by 21.06 N，and that on the auxiliary bearing by 7.73 N.Furthermore，over the full speed range，the optimized prototype exhibits lower vibration acceleration than the original prototype at most rotational speeds.At 6 000 r/min，the total vibration acceleration decreases from 20.41 m/s² to 9.88 m/s².This study provides theoretical support for improving the dynamic balance performance of high‑speed scroll compressors.

To improve the pressure retention and sand mixing effects of high‑energy mixing tanks，computational fluid dynamics methods and orthogonal experiment methods were used to analyze the influence patterns of different parameters on evaluation indicators such as inlet‑outlet pressure ratio，outlet particle volume fraction，and unit volume mixing energy of the mixing tank，determining the corresponding impacts of each parameter.The results show that the order of influence of outlet diameter，impeller rotational speed，sand inlet diameter，liquid inlet diameter，and number of blades on the three evaluation indicators （inlet‑outlet pressure ratio of mixing tank，outlet particle volume fraction，and unit volume mixing energy） exhibits differences.The influence of outlet diameter and impeller rotational speed on the inlet‑outlet pressure ratio shows a significant relationship at the 0.1 level；impeller rotational speed has a significant impact on unit volume mixing energy，with higher impeller rotational speed leading to greater unit volume mixing energy of the mixing tank；the optimal combination scheme to improve the sand mixing effect and pressure retention effect of the high‑energy mixing tank is：number of blades 4，liquid inlet diameter 203 mm，outlet diameter 240 mm，sand inlet diameter 365 mm，impeller rotational speed 800 r/min；the optimized mixing tank shows improvements in mixing time and energy consumption by approximately 12% and 22%，respectively.The relevant results can provide references for structural optimization and efficiency enhancement of similar high‑energy mixing tanks.