To address the issue of seal failure in drilling pump piston‑cylinder liner sealing pairs caused by excessive friction resistance and severe temperature rise under high‑speed and high‑pressure operating conditions，surface microstructure specimens with varying diameters，depths，area ratios，and arrangements were designed and fabricated using nitrile rubber （NBR） pistons and high‑chromium cast iron cylinder liners.A sealing pair simulation test platform was established using a friction and wear tester to systematically investigate the influence of microstructure geometric parameters on the friction coefficient，surface temperature rise，and wear amount of the sealing pair.The friction reduction and temperature reduction mechanisms were revealed by analyzing the microscopic wear morphology.The results indicate that when the microstructure parameters are a diameter of 100 μm，a depth of 40 μm，and an area ratio of 4% to 5%，the comprehensive performance of the sealing pair is optimal.Compared with the non‑textured specimen，the average friction coefficient is reduced by approximately 50%，the surface temperature rise is reduced by 62.5%，and the piston wear amount is reduced by 40.7%.Under these parameters，the microstructure can achieve continuous lubrication and wear debris storage by forming a "micro‑oil reservoir"，thereby reducing abrasive wear，dispersing contact stress，and avoiding local overheating，synergistically enhancing the friction reduction，temperature reduction，and wear resistance performance of the sealing pair.This study can provide a reference for the surface structure optimization of drilling pump piston‑cylinder liner sealing pairs.

In order to improve the heat transfer performance of the heat recovery device in the closed system of heat pump dryer，a heat recovery device with a convex structure （truncated cone‑shaped and cylindrical） was proposed.The influence of the shape and arrangement of the convex structure on the heat transfer performance was analyzed by the method of experiment and numerical simulation.The results show that when Re=542~1 692，the heat transfer enhancement multiples of Nu_{truncated cone}/Nu_plate and Nu_cylinder/Nu_plate are 1.29~1.42 and 1.22~1.26，respectively，which are larger than those of smooth plate.The comprehensive thermal performance evaluation factor PEC of the truncated cone‑shaped convex heat recoverer is 1.09~1.15，which is better than that of the cylindrical convex structure with the same Re.The PEC of the staggered arrangement of the cone‑shaped convex heat collectors is 1.09~1.15.Among them，the PEC of Re=542~1 490 staggered arrangement is larger than that of grouping arrangement，and the comprehensive heat transfer performance of staggered arrangement is better.The research results provide a theoretical basis for the structural optimization of the heat recovery device of the heat pump dryer.

To investigate the hydraulic characteristics of centrifugal pumps during rapid transient processes and optimize their startup strategies，transient tests under various startup conditions were carried out on a marine centrifugal pump with a specific speed of 102.Based on a transient hydraulic performance test platform with a synchronous data acquisition system，the effects of five rotational speed variation curves and four startup times on the transient characteristics of pump startup were compared and analyzed under the conditions of rated speed of 1 450 r/min and design flow rate of 25 m³/h.The results show that under a fixed startup mode，the impact head decreases with increasing startup time.The startup acceleration has a significant effect on the impact head.Under the same startup time，the exponential startup curve produces the smallest impact head due to its lower acceleration in the final stage，with corresponding values of 6.923，6.872，6.865 and 6.836 m for the four startup times.The head overshoot rate is proposed as an indicator for evaluating the transient response of centrifugal pumps during startup.This parameter gradually decreases with time，and its variation trend exhibits an obvious concave curve characteristic.The head overshoot rate for the exponential startup mode is always the lowest，with values of 1.011 8，1.004 7，1.002 7，and 1.001 3，respectively.The exponential startup mode can effectively suppress head impact and is an ideal startup scheme for centrifugal pumps.This study can provide experimental basis and reference for the evaluation of startup status and optimization of operating performance of centrifugal pumps.

To explore the unsteady flow characteristics and evolution mechanisms of the stern jet of a pump‑jet propulsor，based on the numerical simulation results of the DES model，the dynamic mode decomposition method was used to decompose and reconstruct the stern jet flow field of the pump‑jet under different cruising conditions.By comparing the numerical simulation with experimental data，it was found that the average error of thrust performance was 6.6%，verifying the effectiveness of the model.The results indicate that the stern jet flow field of the pump‑jet can be decomposed into flow features with different energies and frequencies.The first five modes account for more than 99.9% of the total energy.The fundamental mode with zero frequency represents the steady‑state structure of the unsteady flow field，reflecting the steady‑state flow field characteristics of the pump‑jet wake under different speeds and rotor rotations.Other major modes reveal the influence of the development process of high‑energy fluid masses in the wake on the wake flow bundle.Through the dynamic mode decomposition method，a low‑dimensional approximation of the high‑dimensional multi‑scale flow field can be effectively achieved，with reconstruction errors of 4.5% （low speed），5.3% （medium speed），and 4.4% （high speed），reflecting the unsteady characteristics of the complex flow field.As the speed increases，the energy becomes more concentrated in a few dominant modes.The proportion of the first‑order mode in the total energy gradually increases，approximately 95.2% at low speed，97.6% at medium speed，and 98.9% at high speed.The period of the modal coefficients increases，the flow field stability is enhanced，the wake flow bundle fluctuation of the first‑order mode decreases，and the velocity variation becomes more uniform.This study can provide a theoretical basis for the structural optimization design of pump‑jet propulsors and wake field stability control.

Aiming at the challenge of efficient treatment and utilization of oil‑contaminated sludge generated during petroleum exploitation，processing and gathering-transportation，the distribution characteristics of turbulent flow field as well as the movement and distribution behavior of oil‑contaminated sludge particles were conducted.A DN50 axial‑flow hydrocyclone model was established and verified by experimental tests.The Eulerian multiphase flow model and RSM turbulence model was adopted to explore the turbulent desorption mechanism of oil‑contaminated sludge under rotating flow field.The results show that within the research range （flow rate of 2~6 m³/h，overflow ratio of 2%~20%），the optimal operating conditions are flow rate of 4.5 m³/h and overflow ratio of 10%，under which the crude oil recovery rate and sludge reduction rate reach 96.72% and 99.27% respectively.During the treatment of oil‑contaminated sludge，variation of flow rate affects both the rotating separation process and the desorption process of oil‑contaminated sludge simultaneously.The influence of overflow ratio on the rotating separation process is significantly greater than that on the desorption process of oil‑contaminated sludge.The turbulent effect of the rotating flow field enables efficient desorption of oil‑contaminated sludge.This study provides a reference for the industrial application of a two‑stage rotating process integrating "intensive turbulent desorption" and "enhanced cyclonic separation".

Aiming at the problems of low head and low efficiency of a high‑speed centrifugal pump used for cooling specific equipment under strict space constraints，a study on cavitation characteristic analysis and inducer wrap angle optimization was carried out.The reliability of the numerical analysis results of the pump was verified by comparing the experimental test results with the simulation calculation results.Based on the basic cavitation equation，cavitation specific speed and suction specific speed methods，the required net positive suction head （NPSH_r） of the pump was initially calculated.Combined with the CFD cavitation flow field simulation，the accuracy of the theoretical calculation results and the critical conditions for cavitation occurrence were clarified.On this basis，an inducer was designed，and the effects of wrap angles （ranging from 100° to 200°） on the performance of the inducer and the entire pump were systematically studied.The results show that the inducer wrap angle has a significant impact on the head and efficiency of both the inducer itself and the entire pump.When the wrap angle is 140°，the inducer achieves the optimal efficiency and provides a head of 11.86 m，which can meet the anti‑cavitation requirements.After assembling this inducer，the head of the optimized entire pump is increased to 71.29 m，and the efficiency reaches 81.76%，which are 4.47% and 5.44% higher than those before optimization，respectively.In addition，the critical cavitation point shifts leftward after optimization，and the available net positive suction head （NPSH_a） increases to 21.37 m，with an increase of about 1.25 times，indicating that the anti‑cavitation capacity of the system is significantly enhanced，and both the head and efficiency meet the design requirements.This study can provide a theoretical basis and engineering reference for the high‑performance design of high‑speed centrifugal pumps under lightweight constraints.

To improve the separation performance of a spiral pipe separator，a novel two‑stage cyclone separator using a spiral pipe assembly as the feed channel was developed.The structural parameters of the device were optimized through orthogonal experiments，and the optimal structure was determined as follows：the spiral pipe has one turn，the ratio of the curvature radius to the cyclone body radius is 0.76，and the outlet of the spiral pipe is located one pipe diameter below the interface between the cylindrical and conical sections of the separator.The separation performance before and after optimization was compared using numerical simulation methods，and validation experiments were conducted on the optimized structure.The results show that after optimization，the pressure distribution in the central region of the device becomes more uniform，the negative pressure region shrinks significantly，and the pressure loss is reduced.The swirling velocity increases，the centrifugal force is enhanced，promoting particle movement toward the wall，thereby strengthening liquid-solid separation.With the radial position r/R=0.5 as the boundary，the average solid phase concentration on the side near the wall increases by 5.1%，while the average concentration in the central region of the separator decreases by 28%.The residence time of solid particles inside the cyclone is shortened，and the number of particles escaping from the overflow port is reduced.The optimization of the spiral pipe structural parameters enhances the flow near the wall in the secondary cyclone region while reducing the disturbance to the central fluid，which is beneficial for the liquid-solid separation process in the two‑stage cyclone separator.This study can provide a reference for the engineering design and application of two‑stage cyclone separators.

Aiming at the problems of limited accuracy，high cost and poor real‑time performance of traditional centrifugal pump test systems，an automated test system based on Siemens S7-1500 PLC and the .NET platform was designed.The system employed high‑precision sensors and PID closed‑loop control，Breaking through the middleware limitations of traditional commercial configuration software，the system utilizes an underlying asynchronous Socket mechanism based on TCP/IP to directly interact with the PLC for lightweight data exchange，achieving a communication delay of ≤50 ms.Taking a centrifugal pump with a rated speed of 894 r/min，rated flow of 1 090 m³/h，and rated power of 221 kW as an example，the system underwent experimental validation.The results demonstrate that measurement uncertainties of all key performance parameters of the system meet Class 1 accuracy in GB/T 3216—2016.The measurement uncertainties for flow rate，head，power，rotational speed，and efficiency are ±1.06%，±1.20%，±0.91%，±0.19%，and ±1.79% respectively，all falling below their permissible limits （±2.0%，±1.5%，±1.5%，±0.5%，±2.9%）.Leveraging the .NET open‑source ecosystem and modular design，it significantly reduces development and maintenance costs Furthermore，through a dependency injection （DI） decoupled design，it provides underlying architectural support for intelligent expansions，such as the native integration of ML.NET machine learning algorithms.This system combines the advantages of high precision，low latency，low cost，ease of operation，and strong scalability.This research offers a reliable integrated solution for high‑precision，low‑cost automated test of industrial pumps.

Aiming at the prominent problems including hump characteristics and poor operation stability of nuclear reactor charging pumps under off‑design low‑flow conditions，this paper adopts numerical simulation combined with experimental tests to explore the effects of balance chamber flow passages on the hydraulic external performance and internal flow field of the charging pump，and optimizes the internal flow state by improving impeller structural parameters.Single‑stage model pump experiments and numerical results reveal that the leakage flow rate of the balance drum accounts for merely 3%~6% of the rated design flow.Such leakage exerts a marginal effect on pump head prediction and cannot change the qualitative law of hydraulic hump characteristic prediction；hence，a simplified numerical model ignoring the balance chamber flow passage is applicable for hydraulic performance optimization.Comparative tests on pump hydraulic performance with different blade lean angles （θ=0°，3°，4°，5°） under low‑flow hump working conditions verify that the blade lean design is an efficient method to restrain the hydraulic hump.Specifically，the hydraulic hump phenomenon of the pump is completely eliminated within the full operating flow range when the blade lean angle is set to 5°.Adopting the combined optimization scheme with tapered convergent flow passage and 5° blade lean toward the blade pressure side，the proposed design not only restrains the hump characteristic of the charging pump under low‑flow conditions，but also optimizes the internal flow field of the impeller.Meanwhile，the generation of internal low‑speed flow zones and flow vortices is weakened，which further improves the cavitation resistance and operational stability of the pump.This study can provide technical support and theoretical references for the optimal hydraulic design of nuclear reactor charging pumps.

To address the shortcomings of traditional vapor‑compression refrigeration technology in terms of volume，energy efficiency，and operational reliability，thermoelectric refrigeration technology has attracted widespread attention due to its high efficiency，environmental friendliness，and high reliability.This paper reviews the latest research progress in thermoelectric refrigeration technology，with a focus on the current status of thermoelectric materials，numerical modeling methods for thermoelectric cooling，and their application scenarios.First，the development history of thermoelectric materials is introduced，and the major achievements are summarized.Second，to improve the performance of thermoelectric cooling systems，models of thermoelectric elements and thermoelectric coolers at different dimensions are compared and analyzed，and the results show that 3D models can more comprehensively describe the microscopic mechanisms during the actual operation of thermoelectric modules.Finally，the application status of thermoelectric refrigeration is summarized from the aspects of electronic cooling，medical equipment，and automotive air conditioning，and it is pointed out that the key to future development lies in improving the intrinsic properties of thermoelectric materials，optimizing the heat dissipation path on the hot side of thermoelectric devices，and further enhancing the system COP，thereby achieving collaborative design of materials，devices，and systems.This study can provide a theoretical reference for the design optimization and engineering application of thermoelectric cooling systems.

To address the problem of excessive time cost when adopting fluid-structure interaction CFD simulations to study the effect of low‑temperature characteristics of boil‑off gas （BOG） on screw compressor efficiency，this study establishes a numerical model of a twin‑screw compressor using MATLAB.The PDE toolbox is employed to calculate the temperature distribution and thermal deformation of the screw rotors.The new clearance caused by rotor deformation is then incorporated into the numerical model to obtain the compressor efficiency considering rotor deformation.The computation time of this process is approximately 1/100 of that required for CFD simulations，greatly reducing the time cost.The numerical results were compared with those from an experimentally validated CFD model，and the errors in volumetric efficiency and isentropic efficiency were both within 3%.Furthermore，a low‑temperature intake test rig was constructed to measure volumetric efficiency at different intake temperatures.The maximum error between the measured data and the numerical results was within 5%，thereby verifying the reliability of the model.Based on the model，the influence of rotational speed on compressor performance was analyzed.The results show that as the rotational speed increases from 4 000 r/min to 10 000 r/min，the volumetric efficiency rises from 55.1% to 73.2%.The isentropic efficiency first increases and then decreases with rotational speed，reaching a maximum value of 62.2% at 8 000 r/min.This model can quickly and accurately predict the performance of the BOG twin‑screw compressor under various operating conditions，providing a reference for the efficiency design and optimization of high‑speed twin‑screw compressors.

To address the issues of repetitive design，high cost，and optimization difficulties in the series development of blower volutes caused by a single design process and limited software functionality，an adjustable partition plate is adopted to achieve serialized structural design of the volute.By optimizing the width and height of the partition plate to adapt to the flow channel cross‑section requirements of different volutes，the maximum sharing of volute components across blower units is realized.Combined with CFD calculations and flow field analysis，the performance quality and operating condition adaptability of the serialized products are ensured，and the reliability of the numerical simulation is verified through experiments.The results show that when using the adjustable partition plate for volute serialization design，the optimal range for the partition plate height D₄/D₂ is 1.65~1.72；when the partition plate width is greater than 5 mm，optimizing its structure can improve the flow field performance of the serialized volute.The blower units adopting the serialized volute structure have a wide operating range，with relative variability efficiencies of each unit all exceeding 82.5%，and total pressure ratios greater than 1.8，and they have been well applied in wastewater treatment energy‑saving projects.This study can provide a reference for the serialized design of blower volutes.

To address the issue of power fluctuations caused by disturbances and parameter variations in the pitch control of wind turbines，a pitch angle control strategy based on the fusion of an improved genetic algorithm and predictive control （PID+ImGA+MPC） is proposed.This method introduces a Cauchy-uniform distribution hybrid crossover and adaptive mutation mechanism to enhance global search capability，and combines ARIMA wind speed prediction with model predictive control to achieve feedforward adjustment of the pitch angle. By deeply integrating the improved genetic algorithm，ARIMA wind speed prediction，and MPC，an integrated "prediction-optimization-feedforward" pitch control framework is formed，which compensates for the shortcomings of existing strategies，such as insufficient utilization of predictive information and reliance on offline optimization for parameter tuning.Hardware‑in‑the‑loop verification is conducted using a pitch control system intelligent loading test bench based on Bladed.The results show that the error between simulation and measured results is controlled within ±3%，verifying the engineering feasibility and real‑time performance of the strategy.In simulations on a 1.5 mW doubly‑fed wind turbine model，under step wind conditions，the proposed strategy reduces the power overshoot from 4.025% to 0.69% and shortens the settling time from 3.66 s to 2.2 s；under turbulent wind conditions，the standard deviation of output power is reduced by 12.40% compared with conventional PID.This study can provide a theoretical basis and engineering reference for the stable control of wind turbines under high wind power penetration conditions.