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.

To address the effective sealing of lost fish boreholes in old wells within gas storage zones，a high‑pressure abrasive jet erosion perforation method was developed.Experimental studies on abrasive jet erosion of lost fish drill pipes were conducted，with perforation time and hole diameter as evaluation indicators.The effects of jet parameters and abrasive parameters on perforation performance were analyzed，and the maximum standoff distance diagrams under different jet pressures were obtained.Results show that different abrasives exhibit varying perforation efficiencies：silicon carbide>ceramic particles>quartz sand，with silicon carbide recommended for its higher hardness.Under the same jet pressure，abrasive particle size （40~60 mesh） and volume fraction （6%~8%） significantly affect perforation quality.Reducing standoff distance and increasing pump pressure are critical for improving efficiency.Erosion efficiency decreases with increasing jet angle （not exceeding 25°）.Abrasive jet perforation effectiveness declines with standoff distance，with maximum standoff distances predicted between 24.7~42.5 cm at 10~30 MPa.The method can perforate ⌀127 mm drill pipe bodies in 2~4 minutes and tool joints in 10~12 minutes，creating holes of 11~26.9 mm diameter.This study validates the feasibility of high‑pressure abrasive jet erosion for lost fish perforation，providing theoretical and methodological guidance for sealing complex old wells in gas storage.

In response to the problem of incomplete combustion of hazardous waste paste after it enters the pre‑decomposition furnace，which causes fluctuations in carbon monoxide emissions from cement kilns and makes the emissions exceed the standard，a method of using multiple gas jets to break up and atomize hazardous waste paste is proposed.A hazardous waste paste containing 40% sludge mass fraction is determined for compatibility based on the experimental results of slump and viscosity，The feasibility of break up and atomization of hazardous waste paste is demonstrated based on the effects of rotational shear and structural flow shear.An experimental platform for breakup and atomization characteristics is built，and the influence of nozzle number i，nozzle to spray gun discharge edge distance d，and feeding speed v on atomization angle，spray distance，geometric shape，particle size，and mass distribution was studied.The research results indicate that the slump of hazardous waste paste containing 40% sludge mass fraction is 100 mm，the viscosity is 224 200 mPa·s，the yield stress is 219.2 Pa，the calorific value is 27.18 MJ/kg，the suitable combustion temperature is 1 000 ℃，and the residence time in the furnace is at least 400 s，with the highest burnout rate.It is determined that the fluid belongs to a Bingham fluid based on the relationship between shear rate and shear stress，as well as the phenomenon of shear thinning.The research on atomization characteristics shows that the atomization angle is between 60°~80°，which is basically consistent with the theoretical value of 70°，and the atomization geometry is in the shape of a bullet.According to the study of mass distribution，the atomization effect is optimal when i=3，followed by i=5，and i=2 has the worst effect.When d=160 mm，the atomization effect is optimal，followed by d=240 mm，and d=80 mm，the effect is the worst.As the pushing speed v increases，the atomization effect gradually deteriorates.The new sprayer adopts the staggered layered three‑dimensional impact jet method，with i=3 and d=160 mm as the optimal design input parameters.The research results can provide reference for the study of new gas jet spray guns.

To address the heating capacity degradation caused by outdoor unit frosting during winter operation of air‑source heat pumps，an electric heater was installed at the inlet pipe of the outdoor heat exchanger to elevate evaporation temperature，delay frosting，and reduce defrosting frequency. Experimental prototypes were tested to compare system performance with/without the electric heater，analyze differences between constant operating parameters and automatic adjustment，and investigate the effects of heater power，compressor frequency，expansion valve opening，and outdoor fan speed on heating performance.Results show that a 560 W heater extends heating duration by 15.1% and increases average heating capacity by 1.6%.Within the 0~735 W power range，heating duration linearly increases with heater power，extending by 2.4 minutes per 100 W increment.This study provides reference for defrosting optimization in air‑source heat pumps.

Aiming at the problems of poor cooling effect，energy efficiency ratio （EER） and low operational reliability of air source heat pump system under extreme working conditions，a three‑pressure heat pump system was developed and an experimental platform was built.The cooling performance of the single‑stage heat pump system and the three‑pressure heat pump system was compared and analyzed through the experimental research.The results show that with the increase of compressor speed，the cooling capacity of the three‑pressure system is higher than that of the single‑stage system.At 4 500 r/min，the cooling capacity is higher by 9.7%，the EER is higher by 4.72%，and the exhaust temperature of the three‑pressure system is lower by 4.23%.When the outdoor temperature is greater than 43 ℃，the cooling capacity and EER of the three‑pressure system increase compared with that of the single‑stage system.When the outdoor temperature is 43 ℃ and 46 ℃，the cooling capacity of the three‑pressure system increase 26.06% and 37.9%，and the EER increase 8.6% and 20.5%.With the increase of the outdoor temperature，the effect of the three‑pressure system on suppressing the compressor exhaust temperature is more obvious.When the outdoor temperature is 46 ℃，the exhaust temperature is reduced by 12.33%.The research results provide a reference for the application of air source heat pump system in extreme working conditions.

In order to improve the hydrodynamic characteristics and reduce energy consumption of reciprocating plate column，an energy saving reciprocating plate column based on electro‑permanent magnet technology was proposed. Through the finite element simulation of magnetic field，the average magnetic induction intensity of the electro‑permanent magnet device was 1.48 T，which satisfies its feasibility as a driving mechanism. Subsequently，the water-kerosene system was used in a reciprocating plate column with an inner diameter of 55 mm. The results show that with the increase of vibration frequency，the ratio of dispersed holdup decreases first and then increases，up to 16.7%；The sauter mean diameter decreases with the increase of vibration frequency，and the minimum is 2.75 mm；Due to the introduction of the electro‑permanent magnet device，the reciprocating plate column can enter the dispersion zone when the vibration frequency is higher than 1 time/min；Under low frequency vibration，the reciprocating plate column exhibits a mass transfer surface area of up to 314.5 m^-1；The electro‑permanent magnet device consumes only 450.8 J/min，indicating a significant energy‑saving effect.The research provides a theoretical basis for the promotion and application of reciprocating plate column based on electro‑permanent magnet technology in processes such as mixing and separation.

To address the challenges of difficult and time‑consuming repairs when a refrigerated display cabinet malfunctions，which can lead to spoilage of the products inside，a new modular drawer‑type refrigeration system for refrigerated display cabinets is proposed.This system integrates the components of the refrigeration system，including the compressor‑condenser unit，evaporator，and capillary tube. A modular drawer‑type refrigeration system refrigerated display cabinet was constructed，and its disassembly and assembly characteristics，food storage performance，and 24 hour power consumption were analyzed under environmental conditions of 25 °C and 60% relative humidity.The research results indicate that the disassembly and assembly of the proposed modular refrigeration system take only 2.3 minutes，and the replacement of the refrigerated display cabinet's dual refrigeration modules can be completed within 5 minutes. Additionally，the temperature of the test package stored in the modular drawer‑type refrigeration system refrigerated display cabinet can be maintained between 3.8 °C and 7.1 °C，which meets the requirements for food storage in refrigerated display cabinets. The modular refrigeration system also ensures uniform temperature distribution inside the refrigerated display cabinet.These findings provide a research foundation for the widespread application of easily replaceable，reliable，and high‑performance modular refrigeration systems in refrigerated display cabinets.

In order to solve the problem of the mismatched supply and demand of cooling capacity in the cooling system，the charging and discharging characteristics of the chilled water storage tank are simulated through software.The influences of the position of the perforated plate，the pore diameter of the perforated plate and the opening ratio on the thickness of the thermocline layer in the tank and the charging and discharging efficiency are studied，and verified through experiments.The results show that improving the structure of the orifice plate can reduce the thickness of the thermocline layer and improve the charging and discharging efficiency.When the chilled water storage tank under study has the best effect，the pore diameter of the orifice plate is 20 mm，the opening ratio is 40%，and it is set in the middle position of the chilled water storage tank.Compared with the situation where the orifice plate is placed at the lower part，the charging and discharging efficiency of this structure is increased by 5.2% and 5.4% respectively.Compared with the opening ratio of 30%，the charging and discharging efficiency is increased by 3.2% and 2.1% respectively.Compared with the structure with an opening ratio of 50%，the charging and discharging efficiency is increased by 6.7% and 5.4% respectively.The research results can provide a reference for the optimized design of the cold storage water tanks.

To address the issues of excessive mass flow at surge boundary in the high‑pressure stage and increased surge susceptibility in two‑stage centrifugal compressors，this study investigates the key structural parameter of impeller exit blade angle affecting surge characteristics. Based on CFD numerical simulations validated by the classical Krain impeller model，the influence of exit blade angles in low and high‑pressure stage impellers on overall compressor performance was analyzed. Results show that at the design speed of 70 000 r/min，smaller exit blade angles in both stages improve compressor efficiency at low flow conditions （0.02~0.07 kg/s） with slight pressure ratio reduction. Optimized smaller exit blade angles enhance efficiency by over 3% at low flow rates，reduce surge boundary mass flow by more than 25%，and significantly improve flow stability. The maximum static entropy increase in low and high‑pressure stages decreases by approximately 50% and 25%，respectively，reducing flow losses. This study provides design guidelines for developing two‑stage boosting systems for PEMFC applications.

In order to optimize the elicitation performance of the elicitor of the hydrogen recirculation system of a proton exchange membrane fuel cell in the low‑power region，structural parameters of the elicitor of a 40 kW‑class fuel cell were simulated.Univariate influence tests were carried out at a given power to investigate the influence of nozzle throat diameter，mixing chamber diameter，mixing chamber length and the distance between the outlet of nozzle and the inlet of the mixing chamber on the performance of the ejector.The orthogonal tests were carried out by selecting the better three parameters from each of the four factors mentioned above，and the extreme deviation of the test results was analyzed to get the optimal combinations of the parameters mentioned above and the sequence of the degree of influence on the ejection performance of the ejector.Finally，the optimized ejector was simulated.The results show the maximum hydrogen reflux ratio of 2.315 is obtained when the nozzle throat diameter，mixing diameter，mixing chamber length，and the distance between the outlet of nozzle and the inlet of the mixing chamber are taken as 0.8，3.0，18，2.5 mm，respectively，under the working condition of 60 A.The results of the study show that among the four parameters mentioned above，low power condition has a significant effect on the ejection coefficient，while low power condition has a significant effect on the ejection coefficient，and low power condition has a significant effect on the ejection coefficient.Among the four parameters mentioned above，the parameter that has the greatest influence on the ejection coefficient under low power condition is the nozzle throat diameter，and the parameter that has the least influence on the ejection coefficient is the distance between the outlet of nozzle and the inlet of the mixing chamber.The results of the study provide a reference for the optimization of the structural parameters of the ejector under low‑power working conditions.