Aiming at the common problem of nonuniformity of the temperature field within refrigerated cabinet，perforated plates were used to structurally modify the shelf to optimize the air flow organization inside the refrigerators.The mathematical and physical models of the closed food refrigerated cabinet were established using the method of CFD，and the temperature distribution of the refrigeration cabinet was simulated and studied.By comparing with the experimental data，the reliability of the model was verified.On this basis，the effect of different pore diameters（10，20，30 mm） and porosity rates（6%，9%，12%） were analyzed on the temperature field in the refrigerator.The results show that when the pore diameter is 30 mm and the porosity rate is 9%，the uniformity of the temperature field in the refrigerator is optimal.The food preservation performance is also ideal.Compared with the shelf without pore，the shelf with holes can promote air flow and heat exchange between different layers，significantly improving the uniformity of the temperature field inside the refrigerated cabinet.The research provides important theoretical basis and reference for the design and optimization of refrigeration equipment.

To address the problem of large errors between the calculation results of the theoretical formula for the volumetric efficiency of electrohydraulic proportional pumps and the experimental results under different working conditions，a study on the volumetric efficiency model of electrohydraulic proportional pumps based on machine learning was carried out.Firstly，a nonlinear regression model was constructed，and a significance test was performed on the regression model. Then，a prediction model for the volumetric efficiency of the electrohydraulic proportional pump was built based on the random forest model，and the prediction model was trained and verified using experimental data. Finally，the prediction accuracies of the above two models were analyzed and evaluated. The research results show that under different working conditions，compared with the theoretical calculation formula for the volumetric efficiency of the electrohydraulic proportional pump，the calculation accuracies of the volumetric efficiency of the electrohydraulic proportional pump obtained from the nonlinear regression model and the random forest prediction model are significantly improved.The average relative errors of the volumetric efficiency obtained by the two methods are reduced from 6.68% to 1.25% and 1.24%，respectively.The research results have certain guiding significance for the in‑depth study of high‑precision pump volumetric efficiency prediction models.

To address the dynamic interference issue between the disc and seat during the opening/closing process of quadruple‑offset butterfly valves，precise mathematical modeling enables motion trajectory prediction and parameter optimization.Based on the eccentric structure，a three‑dimensional surface model of the sealing pair was established，deriving motion trajectory equations for any point on the disc.A dual interference detection method combining coordinate comparison and opening/closing angle inspection was proposed.Analysis of 200 cross‑sections of a DN300 valve's sealing pair shows：under initial parameters （first offset 31 mm），interference risks exist during operation；after optimization （first offset adjusted to 43 mm），the opening/closing angle deviation δ improves from initial negative values to zero interference risk on selected sections.This research provides precise theoretical guidance for designing and manufacturing quadruple‑offset butterfly valves，enhancing design efficiency and reliability.

To investigate the feasibility of a CO₂/R1270 mixed refrigerant heat pump system for electric vehicles，the thermophysical properties of the mixed refrigerant were analyzed.A single‑stage transcritical heat pump system model with an internal heat exchanger was established，and the effects of mass ratios and different operating parameters on system performance were examined.The results show that the optimal mass ratio of the CO₂/R1270 mixture is 0.96∶0.04，with the system COP increasing by 13% compared to the single‑refrigerant CO₂ system；the optimal high pressure is 8 MPa，representing a 20% reduction.The refrigeration performance of the system improves as the evaporator inlet temperature rises and decreases as the ambient temperature increases.The impact of changing the evaporator inlet temperature on COP_c is greater than that of ambient temperature.When the ambient temperature is 30 ℃，the COP_c varies most significantly with the evaporation temperature，increasing from 1.18 to 2.81.The most notable factor affecting the system's heating performance is the gas cooler outlet temperature；the system COP_h decreases as the gas cooler outlet temperature rises.Maintaining the gas cooler outlet temperature near the critical temperature of the mixed refrigerant （approximately 42 ℃） yields the optimal heating performance，and the effect of changing the gas cooler outlet temperature on COP_h becomes more pronounced at higher ambient temperatures.This research can provide a reference for the optimal design of mixed refrigerant heat pumps in electric vehicles.

To address the high power consumption of gas storage compressor units under off‑design conditions，the overall performance curve of multiple compressor units was synthesized based on similarity theory and series‑parallel operation rules.Using this curve with optimization algorithms，the impact of speed regulation on total power consumption during gas injection was investigated，obtaining optimal speed control schemes minimizing total power under varying injection demands.The influence of flow rate and pressure ratio distribution on total power consumption at different speeds was also studied.Results show that for this multi‑unit configuration，energy consumption differences between control schemes reach 3% to 6%.When flow ratios are excessively high or low，unit power remains high regardless of pressure ratio adjustments.At moderate flow ratios，power consumption decreases moderately，and further reduction is achievable through proper pressure ratio regulation：for September operation of A1 and A2 compressors in series，optimal pressure ratio ratio is 1.1；for October operation of B1 and B2 in series，optimal ratio is 1.3.This research provides theoretical and technical support for efficient operation of gas storage compressor units.

To investigate the flow noise characteristics in reducer pipes，unsteady numerical simulations of the flow field were performed using large eddy simulation （LES） coupled with the Smagorinsky subgrid‑scale model.Fluctuating pressure analysis was employed to study the distribution of acoustic source intensity inside the pipes.Acoustic sources were extracted using the Lighthill acoustic analogy method，and the acoustic field in the reducer pipe was calculated via the acoustic finite element method.Experimental comparisons validated the reliability of the numerical approach.With overall sound pressure level （OSPL） as the optimization criterion，a hyperbolic structure was adopted to optimize the reducer pipe.Results show that this computational method effectively predicts flow‑induced noise in reducer pipes，with a relative error below 3% compared to experimental results.Peak pressure fluctuation intensity occurs at the inlet and outlet transition sections，with maximum fluctuating pressure root mean square （C_p，RMS） values of 0.086 3 and 0.083 1，respectively.OSPL values at the transition section，outlet，and inlet are 138.07 dB，135.48 dB，134.35 dB，respectively.The hyperbolic structure significantly reduces pressure fluctuations at the transition section and internal flow noise，decreasing OSPL at the inlet，transition section，and outlet by 7.37%，8.85%，and 8.23%.This study provides theoretical references for structural optimization of reducer pipes.

In response to the efficient and safe cleaning needs of bulk cargo holds，starting from the analysis of the mechanical characteristics of the four‑wheel drive robot，key components of the robot were designed.A detailed analysis was conducted on the force and torque characteristics during the process of crawling through obtuse angled walls，reverse inclined surfaces，and obstacle crossing in cargo holds.A mechanical equilibrium equation was then constructed considering the friction force of the wheels and the magnetic adsorption force.Combined with the actual working conditions on site，the adsorption ability of the robot was analyzed and verified.A cargo hold water jet cleaning robot carrying an adaptive cleaning robotic arm is developed and applied on site.The results show that the safety factor of the developed cleaning robot is 1.98，indicating excellent wall attachment ability of the robot.During cleaning operations，the jet radius can reach 25 m at a rated pressure of 1 MPa.Compared with manual cleaning，the cleaning efficiency has been improved to 900 m²/h，and the cleaning time has been reduced by about 50%.The research results can provide reference for the application of automated cleaning of cargo holds in bulk carriers.

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.