To address the heat transfer deterioration caused by dust accumulation on outdoor heat exchangers of air‑source heat pumps，a visual dust removal test rig was constructed.Using mixed particles with diameters of 10 µm and 20 µm，dust removal tests were conducted on plain finned‑tube heat exchangers at different jet angles and wind speeds.Results show that under frontal horizontal jetting，when wind speed reaches 21 m/s，dust removal rate reaches 97%.Under reverse horizontal jetting at 28 m/s，dust removal rate is 40%.At 16 m/s frontal jetting speed，during the initial stage，dust removal rate increases with rising airflow angle，reaching a maximum of 94.7% at approximately 30° above horizontal.When airflow angle further increases，dust removal rate begins to decline.Dust removal mass ratio at 21 m/s frontal jetting speed also peaks around 30° at 92.9%.These findings provide important references for optimizing dust removal strategies of air‑source heat pump outdoor heat exchangers.

In order to investigate the leakage law of gas-liquid two‑phase flow in the first type leakage channel of single screw compressor under different conditions，the first type of leakage channel of a single screw compressor was simplified as a narrow channel，and the meshing clearance was the height.Using nitrogen as the gas phase medium and deionized water and glycerol solution as the liquid phase medium to study the influence low of pressure loss of gas-liquid two‑phase flow in narrow channels with the changes of gas‑liquid velocity，channel height and liquid viscosity.The results show that the pressure drop increases with the increase of gas‑liquid velocity，and the influence of liquid velocity on pressure drop is significantly greater than that of gas velocity.At a same gas‑liquid velocity，the pressure drop rapidly decreases with the increase of channel height.The pressure drop decreases the most when the height increases from 0.03 mm to 0.05 mm，and the pressure drop decreases less when the height increases from 0.05 mm to 0.08 mm.When the liquid phase velocity increases from 0.14 m/s to 0.28 m/s，the pressure drop of water，20% glycerol solution and 40% glycerol solution increase from 3.01 kPa，4.39 kPa and 8.61 kPa to 5.81 kPa，7.80 kPa and 15.5 kPa，respectively.A new correlation equation is fitted by modifying the Chisholm parameters of the split phase flow model，which can effectively predict the pressure drop in narrow channels with heights ranging from 0.01 mm to 0.08 mm，and a maximum deviation of no more than 25%.The research can provide theoretical reference for the design and manufacturing of single screw compressors.

In order to quantitatively explore the influence of cyclic oil injection quantity on the heat transfer performance of screw air compressors，experiments were conducted to study the effects of changing oil injection quantity and suction temperature on exhaust temperature，overall temperature difference，inlet and outlet oil temperature of oil coolers，logarithmic mean temperature difference and convective heat transfer coefficient under different operating conditions.At the same time，the curve of convective heat transfer coefficient and oil injection quantity was fitted using experimental data.The results show that the oil injection quantity and input power should be accurately matched under the rated exhaust pressure at full load.When the oil injection quantity decreases from 262 L/min to 134 L/min，the convective heat transfer coefficient of the oil cooler to decreases by 12.4%，the temperature difference of the lubricating oil will increase from 16.0 ℃ to 29.8 ℃，resulting in an 8.3% decrease in the logarithmic mean temperature difference of convective heat transfer under the original calculation conditions，increasing exhaust temperature.The research can provide theoretical guidance for solving the problem of high exhaust temperature in screw air compressor.

To further enhance aerodynamic efficiency and effectively reduce noise of air‑conditioning axial fans，a cross‑species multi‑element bionic design was applied to fan blades by combining the superior flight characteristics of seagull airfoils with the noise‑reducing non‑smooth functional structures of butterfly wing surfaces.First，CFD simulated internal flow characteristics and aerodynamic performance，with numerical model validity confirmed through experimental comparisons.Subsequently，large eddy simulation （LES） and FW-H acoustic analogy methods predicted noise levels of fans with composite bionic blades.Results demonstrate that cross‑species composite blades effectively reduce flow separation losses at blade tip clearances and decrease surface pressure fluctuations.Compared to the prototype fan at identical conditions （rotational speed 730 r/min），the composite blade fan shows：9.07% higher aerodynamic efficiency，126.4 m³/h increased airflow，70.2 W reduced power consumption，and 2.6 dB noise reduction.This study provides solution references for axial fan blade design and performance optimization.

Aiming at the problem of seal failure caused by thermal deformation of an aero‑engine fuel pump under extreme conditions such as high temperature and high speed，this study establishes a thermal-fluid-solid interaction model for an upstream pumping mechanical seal based on the mechanical seal structure of an afterburner fuel pump.Professional computational fluid dynamics software and a thermal-fluid-solid coupling platform are employed to calculate the stress and strain on the seal rings under extreme conditions.The influences of varying operating parameters—rotational speeds ranging from 20 000 to 40 000 r/min and pressure differences from 0.5 to 9 MPa—on the stress and strain of the mechanical seal rings are analyzed.Results indicate that when the liquid film thickness on the seal face is 2 μm，the spiral groove depth is 6 μm，the number of grooves is 12，and the spiral angle is 18°（serving as baseline parameters），both the dynamic and static seal rings experience measurable stress and strain as the rotational speed increases.Notably，the maximum stress and deformation of the dynamic ring exceed those of the static ring，with the maximum deformation difference between the two rings reaching 2.5 μm.As the sealing pressure difference increases，the stress and strain values of the seal rings increase linearly.However，the seal rings exhibit low sensitivity to pressure changes：for every 1 MPa increase in pressure difference，the strain increases by approximately 0.02 μm，and the maximum stress increases by approximately 0.3 MPa.Under all tested operating conditions，the seal rings generate corresponding stress and strain.Therefore，during the design and calculation processes，the impact of these stresses and strains on overall sealing performance must not be overlooked.The research results can provide valuable references for multi‑physical field coupling calculations of upstream pumping mechanical seals under extreme conditions.

In order to improve the heat transfer performance of the evaporator in the cold storage refrigeration system，a new type of plate evaporator was designed.The influence of refrigerant mass flow rate and air side velocity on the heat transfer characteristics of the plate evaporator was discussed by using the method of simulation combined with experiments，and an optimized structure with an intermediate channel was proposed.The heat transfer characteristics of the plate evaporator were studied when the inlet dryness of refrigerant R22 was 0.27，the temperature was -5 ℃，the saturation pressure at this temperature was 0.421 8 MPa，the mass flow rate was 0.017 kg/s，the air inlet temperature was 6 ℃，the relative humidity was 80%，and the flow rate was 3 m/s.The results show that in the design conditions，the cooling capacity in this design condition is 2.86 kW，the refrigerant side pressure drop is 1 150 Pa，and the air side pressure drop is 412 Pa.As the mass flow rate of refrigerant increases，the cooling capacity increases，but the growth rate slows down significantly after reaching 0.017 kg/s.The pressure drop on the refrigerant side also increases，and the growth rate gradually increases.As the inlet flow rate on the air side increases，the cooling capacity increases，but the growth rate slows down significantly after reaching 3 m/s.The pressure drop on the air side also increases，and the growth rate gradually increases.The refrigerant mass flow rate should match the air inlet conditions.Compared with the original structure，the plate evaporator with a middle connected structure has increased cooling capacity by more than 9.4%，increased refrigerant side pressure drop by 18.3%，and increased air side pressure drop by 20.2%.The intermediate connected structure can improve the heat transfer performance of the evaporator.The research results can provide reference for the study and design of evaporators in cold storage refrigeration systems.

To address the prevalent issues of high water content，associated gas，and difficult separation of small‑diameter bubbles in oilfields，a gas‑liquid‑inertial cyclone separator structure was designed based on inertial pre‑separation and centrifugal separation principles.This structure achieves bubble size reconstruction and pre‑separation by distributing bubbles of different sizes at distinct positions at the inlet，enabling smaller bubbles to migrate more easily toward the cyclone center，thereby improving separation efficiency.Numerical simulations comprehensively analyzed the pre‑separation effectiveness，flow field characteristics，and separation performance under various operating conditions.Results demonstrate that under conditions of inlet bubble size less than 50 μm，split ratio 13%，processing capacity 2.0 m³/h，and gas concentration 10%，maximum separation efficiency reaches 99.98%.The gas‑liquid‑inertial cyclone separator significantly enhances separation efficiency for micro‑bubbles，achieves efficient separation for bubbles of different sizes，and is suitable for complex industrial applications.

To address the low volumetric efficiency caused by significant leakage in small‑displacement submersible progressive cavity pumps，this study takes the GLB-20 pump as the research object.Using Ansys Fluent software，a fluid simulation model was constructed based on user‑defined functions（UDF） and dynamic mesh technology to simulate transient and steady‑state flow fields.The influence laws of structural parameters including eccentricity，stator lead，and clearance on flow velocity and leakage were investigated.Experimental validation of optimization results yielded the optimal design scheme.Results show the pump exhibits significant harmonic variation during operation，with flow pulsating twice per cycle matching the stator‑rotor lead ratio.Transient flow fields conform better to actual conditions than steady‑state fields.Clearance is the most critical factor affecting leakage and flow velocity：stator lead influences flow velocity more than eccentricity，while eccentricity affects leakage more than stator lead.Optimized parameters via Box-Behnken design （BBD） method are eccentricity 1.8 mm，stator lead 78 mm，clearance 0.3 mm.Leakage decreased by 12.7%，volumetric efficiency significantly improved，and flow stability enhanced.This research provides design basis for small‑displacement submersible progressive cavity pumps.

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.