According to HAF regulations and the quality management standards of the nuclear power plant，in combination with ASME nuclear power codes & standards and by fully considering the functionality，complexity，maturity，utilization rate and cost of the components，the division criteria of the quality assurance level and safety classification for the HPR1000 RCP are analyzed. The division purpose is to reduce the cost of the manufacturing activities and decrease the labor and material resources required for the control of quality assurance activities appropriately.Based on such four aspects as of the ASME design codes，function，stress retaining and whether it is in contact with the medium，the definition principles of the quality assurance level are proposed，and the definition principles of the safety classification are proposed according to the requirements of ASME Ⅲ Division 1-Subsection NB，NC and ND.The division principles of the quality assurance are compared with those of the safety classification to ensure that the quality assurance level is not lower than the safety classification.

In order to analyze the influence of different impeller structure on the performance of engine cooling pump,an unshrouded and a shrouded impeller were designed respectively for an engine cooling pump. The full 3D flow simulations were conducted for internal flow of impeller using Fluent 6.2 for these two configurations. And the shrouded impeller was chosen for test verification,and the reliability of the simulation results was validated. The test results show that,the hydraulic efficiency of shrouded impeller is higher. The numerical simulation results show that the static pressures in both impellers increase from inlet to outlet gradually,but there is an obviously low pressure area at the inlet of the unshrouded impeller,which is liable to cavitation. On the other hand,there are remarkable vortex and secondary flows in the unshrouded impeller,whereas the flow in the shrouded impeller is more stable. So it can be seen that,the structure of impeller has greater influence on the pump performance,therefore, use of shrouded impeller is more helpful to improvement of hydraulic performance of the engine cooling pump.

To increase the flow rate of the centrifugal fan used in the air purifier,an optimization process was proposed based on Kriging model and genetic algorithm. 25 sets of schemes containing the outlet angle of the volute θ,radius of tongue r and the cutoff clearance t were designed using the orthogonal experiment methods. The steady numerical simulation of the 25 sets of volute schemes was carried out using ANSYS FLUENT software. The flow rate of the fan system was selected as the optimization design objective.The Kriging approximation models between the flow rate and the three parameters of the volute were built. And,the genetic algorithm was used to optimize the approximation models to obtain the optimum parameters of the volute. By simulation tests on the optimized volute,the flow rate of the fan was increased by 19.683%.Meanwhile,by comparing the distribution of such parameters as internal speed,total pressure,of the fan before and after optimization,the velocity distribution inside the optimized volute was more reasonable and the flow loss was relatively small at the tongue.The optimization method of volute proposed can provide an effective reference for the improvement of centrifugal fan performance.

The ground heat exchanger is a device which directly contacts with the soil to extract and release heat,and its heat transfer performance determines the operation efficiency of the ground source heat pump system. The purpose of enhanced heat transfer of ground heat exchangers is to improve the operating efficiency and geothermal energy utilization of ground source heat pump systems. Through the review of the research on the ground heat exchanger for ground source heat pump,the research status and development trend of the buried pipe heat exchanger were discussed,and the main factors affecting the heat transfer of the ground heat exchanger and the enhancement measures of heat transfer were analyzed. Through concurrent consideration of theoretical knowledge and engineering characteristics,the problems existing in current research were proposed,and future research directions and priorities were pointed out,and prospects for the development of ground source heat pumps were anticipated.

In order to improve the calculation accuracy and efficiency of the leakage rate of the annular clearance seal when sealing oil,an accurate numerical calculation method was obtained through grid independence test and experimental verification.Based on this method,the theoretical calculation research under the influence of different key factors(surface roughness,axial taper,eccentricity and circumferential linear velocity) was carried out. The results show that in industrial application,the oil flow in the clearance is mostly laminar flow,the number of oil film grid layers is not less than 4,and when the aspect ratio is 1~1.5,the numerical result is stable;when the oil flow is laminar flow,the surface roughness has no effect on the leakage rate,when it is turbulent flow,the greater the roughness,the smaller the leakage rate;the convergence or divergence of the clearance is almost independent of the leakage,and the leakage rate obtained by multiplying the comprehensive film thickness by 2 is almost in good agreement with the numerical results;the calculated deviation between the two methods increases with the increase of eccentricity,and the agreement is good when the eccentricity is no more than 0.2 mm;the leakage rate decreases obviously with the increase of rotating speed,which is different from the general conclusion.

As the key heat exchanger plays an important role in the process industry,this paper points out its role in two aspects that it plays in the process industry,and explains the essence of integrated energy-saving innovation of equipment and process, and clarifies the relationship between equipment and process. This paper focuses on introduction of the basic structure of two types of high-pressure and high-efficiency energy-saving heat exchangers,namely the spiral wound heat exchanger in the oil refining field and the heat exchanger for printed circuit board in gas processing. Based on the spiral wound heat exchanger,the integrated innovation of equipment and processes for the energy-saving hydrocracking/hydroupgrading process was introduced,and based on the printed circuit board heat exchanger,the improvement of cooling process of mixed refrigerant in natural gas liquefaction plant was introduced. Examples of failures of the seawater-mixed refrigerant heat exchanger in the Hammerfest liquefaction plant were given,and the importance of synergy between safety and energy efficiency was emphasized. The experimental results of three prototypes of seawater-mixed refrigerant heat exchangers were introduced,and the development of seawater-mixed refrigerant heat exchangers in China was introduced to seek a balance between safety and energy efficiency. Finally,it is pointed out that it is not enough to only consider the safety or energy efficiency of the heat exchange equipment. It is necessary to consider the interrelationships and interactions between the heat exchange equipment and the process technology.At the level of the system,we should consider the integrity based on the harmony between energy efficiency and intrinsic safety in order to achieve the integrated energy-saving innovation of equipment and process.

Based on the built performance test rig of the electric automotive heat pump air conditioning system,the effects of variation in EXV opening on condensation and evaporation pressure,subcooling,air outlet temperature of heat pump,heating capacity,compressor power consumption and coefficient of performance (COP) were experimentally investigated. The results show that under the condition of fixed compressor rotational speed,condenser air inlet temperature and air flow rate,as the EXV opening increased,the condensing pressure decreased,but the change in evaporating pressure was relatively small,and subcooling,heating capacity and air outlet temperature of heat pump all decreased and their decrease magnitudes became gentle when the EXV opening increased to a certain extent,and the compressor power consumption decreased at first and then remained basically unchanged,and the system COP increased first then decreased. When the air outlet subcooling of the condenser was relatively big,the air outlet temperature of the heat pump could be effectively adjusted by changing the EXV opening,and when the opening was relatively small, increasing EXV opening was conducive to obtaining a higher COP. The research results can provide a reference for the regulation and control strategy of the performance of the air conditioning system of pure electric automotive heat pump.

Range hood volute design unreasonable will produce uneven wind noise,thus affecting the product's psychological acoustics comfort.In this paper,the design method of centrifugal volute has been introduced,and the causes of the uneven wind of the centrifugal volute are analyzed.Then through numerical analysis the optimal design scheme of weakening the centrifugal volute uneven wind has been proposed.The measured data show that the new design volute average sound pressure level reduced by 1.2dB (A) and the sound of uneven wind has been improved,while maintaining the outlet flow and the total pressure of the outlet.

In order to meet people's high requirements for the comfort of the car's internal environment and solve the impact of the noise of a certain car's air-conditioning centrifugal fan on the comfort,the finite element method was used to simulate and analyze the aerodynamic noise and mechanical noise.The research results show that the main cause for the abnormal noise of the fan was the aerodynamic noise in the fan blade area.The maximum noise in the internal flow domain reached 82.076 dB.Finally,grooves with a depth of 0.5~2 mm,a diameter of 5 mm and a spacing of 7~20 mm were added to the flange,which effectively stabilized the airflow in the fan blade area and eliminated abnormal noise.

In order to systematically study the influence of the throttling structure parameters on the step-down performance of the control valve,the internal flow and throttling characteristics of the spool of the tandem multi-stage step-down control valve were studied and the influence of different structural parameters on its internal flow characteristics was analyzed.The results show that the overall flow coefficient of the multi-stage step-down control valve increases with the increase of the opening;the flow channel inclination angle has an important influence on the pressure control performance of the throttling structure,and the lowest turbulence can be obtained when the flow channel inclination angle of the throttling structure is set to 48°;the chamfering can significantly reduce the generation of vortices;the average turbulence energy is reduced by 73% compared to the nonchamfering solution when a 6mm chamfer is used in the flow channel chamfering position, and the turbulence dissipation rate can be effectively reduced.The chamfering also reduces the turbulent dissipation rate,reduces the pressure drop at the outlet to avoid cavitation.The results of the study can provide theoretical support for the structural design and optimization of the tandem multistage step-down control valve.

In order to study the flow separation phenomenon of centrifugal pump under different working conditions,the low specific speed centrifugal pump was used as the research object to explore the flow structure in the pump under different working conditions based on LES numerical calculation,and verify the accuracy of numerical calculation by using the performance test on the closed test bench.It was found that the highest efficiency point of the pump is at the location of about 1.1Q_d,and under the designed flow rate,the LES calculation error is less than 1.5%.Based on the distribution characteristics of flow field structure at the outlet of the impeller,the flow separation phenomenon under different working conditions was compared and analyzed,and the changing characteristics of flow separation phenomenon at the outlet in the process of the impeller sweeping the tongue and its influence on the flow field structure in the impeller were obtained.The results show that the flow separation phenomenon appears as reflux formation of the separation bubbles on the blade surface,which makes the flow at the outlet of the impeller present uneven distribution characteristics and strengthens the jet-wake structure.Especially under the condition of low flow,flow separation provides energy for the rotation of outlet vortex,resulting in large area blockage of outlet flow passage,with the blocked area up to about 55%,inducing the hump phenomenon of small flow.

Fluid-structure interaction refers to the phenomenon of interaction between fluid and solid,which is manifested as fluid acts on solid to deform or displace it,while solid acts on fluid to cause the change of flow field. In valves,when the fluid-structure interaction phenomenon reaches a certain degree,it will damage valves and many parts connected with valves,and eventually lead to the decline of the working efficiency and even failure of valves.In order to understand the fluid-structure interaction phenomena in valves more comprehensively,the current research status at home and abroad were reviewed from the aspects of fluidstructure interaction theory,experimental method and numerical simulation.Firstly,the mechanism of fluid-structure interaction was introduced;secondly,the characteristics of single-field analysis and fluid-structure interaction analysis were explained, and the advantages of fluid-structure interaction were pointed out.At the same time,the application of different test methods and components in the research of fluid-structure interaction of valves was summarized.In addition,in the numerical simulation, according to the direction of data transmission,the unidirectional fluid-structure interaction simulation and bidirectional fluidstructure interaction simulation were introduced;according to the number of interaction fields and in combination with the related work of valve research,the double-field interaction and multi-field interaction were introduced. Finally,the development direction of fluid-structure interaction simulation was summarized.

Carbon fiber composite is a typical hard-to-machine material. High-quality and high-efficiency cutting and milling technology of carbon fiber composite aircraft skin components is a research focus of advanced aviation manufacturing technology at home and abroad. The mechanism of ultra-high pressure water cutting for carbon fiber composite was discussed,and the design difficulties of precision water cutting equipment for large-size carbon fiber composite aircraft skin components were analyzed. The key technologies of 500 MPa pressure level waterjet unit,five-axis linkage water cutting machine tool,floating lattice flexible bracket,water cutting head mechanism,numerical control system and other components were described. The precision water cutting test of rudder skin shows that it meets relevant machining requirements.

During the daily operation of the high-pressure multistage centrifugal pump，under the condition of sufficient inlet pressure（cavitation allowance of the device），cavitation still occurs in the pump，which causes some noise and vibration，in severe cases，the shaft is even locked and cannot rotate.When repairing the pump，it is often found that the surface of guide vane，volute and wear ring and other area have different degrees of cavitation damage.The cause of cavitation in the clearance and the effect on the pump components are preliminarily analyzed first，then CFD computation software is used to simulate the cavitation generation process in the clearance，and finally the solutions to improve the clearance cavitation are proposed.It is of great significance for long-term safe and stable operation of multistage centrifugal pump.

The innovative design of the piston compressor is of great significance for exploring new and high-efficiency compressor structures.A new type of double opposed piston compressor is proposed，and it has the advantages of lighter weight，fewer parts and high space utilization.The new compressor has two cylinders on both sides of the crankshaft. Each cylinder has two opposed pistons，and the internal piston is connected through an internal connecting rod，the external piston is connected through two external symmetrical external connecting rods，the compressor omits the structure of the cylinder head and crankcase.In addition，based on of detailed introduction of its working principle，the thermal and dynamic calculations are carried out.The results show that the gas force of the compressor can be completely balanced；Through its power calculation，its first-order inertial force is zero，and its second-order inertial force is relatively small；Also，the relatively uniform tangential force and good balance performance of piston force and normal force show that the compressor has good mechanical performance，and has the advantages of smooth operation and low vibration and noise.

A multi-blade centrifugal fan for air conditioning was chosen as the research object to establish the models for 3 kinds of impellers with different blade outlet angles. The external performance of the centrifugal fan was predicted through CFD simulation,the pressure,velocity,turbulent energy distribution at middle section of impeller and fan outlet,and the pressure pulsation at the impeller inlet and outlet were obtained and analyzed comparatively. The results show that as the outlet blade angle increases,the pressure and efficiency of the fan increase in the flow range of 420~725 m³/h.The area of the low-speed zone at the fan outlet increases,the uniformity of the total pressure at the volute outlet and the volute tongue area decreases,and the vorticity in the impeller flow passage increases. Meanwhile,the pressure pulsation amplitude of the impeller inlet and outlet has a certain degree of reduction at the blade frequency and its multiple frequencies. In order to obtain a fan wit better aerodynamic and noise performance,it is necessary to control the blade outlet angle within a reasonable range.The research results prove a better guidance for the design of aerodynamic performance and noise reduction performance of the fan.

Many pumps run between the critical cavitation condition and the initial cavitation condition for a long period of time, which will cause damage such as pitting erosion and perforation on the blade surface,thus making the pump unable to reach the expected life due to cavitation.In this paper,a single-stage single-suction centrifugal pump was selected as the research object, and unsteady cavitation was calculated numerically based on k-ε turbulence model and Z_wart cavitation model.The determination of initial cavitation was based on the cavitation just occurred on the blade surface,and no influence of the bubble produced on the external characteristics.Moreover,the volume fraction of the vapor body was taken as a variable,and the volume fraction of the vapor body in the cavitation region was based on 10%,which was used as the determination basis of initial cavitation.The results show that the initial cavitation allowance first decreases slowly with the increase of flow rate,and the cavitation allowance corresponding to the initial cavitation point is the smallest under the rated flow rate condition,and then increases slowly with the further increase of flow rate.Through analysis,it was put forward to arrange a pump suction system to make its NPSHa greater than the initial cavitation allowance (NPSH_R),namely the NPSH_a>NPSH_R,and plus safety margin based on initial cavitation allowance value (NPSH_R) make the pump run under the working condition of completely no cavitation,and further make the pump does not shorten its life expectancy due to cavitation.

By taking the quasi-secondary compression cycle with economizer vapor injection as the research object,R1233zd(E) and R245fa were selected as the representative high temperature working fluid under the cyclic temperature rise of 40~65℃ to establish the cycle analysis model,and the software Refprop was used to query the physical properties of the working fluid for theoretical simulation. The effects of intermediate vapor injection pressure,primary compression volume ratio,evaporation temperature and condensation temperature on cycle heating capacity,compressor power and COP were analyzed in comparison with single-stage compression cycle. The results show that the heating performance of the quasi-secondary compression cycle was better than that of the single-stage compression cycle under the high temperature conditions of 45℃ evaporating temperature and 110℃ condensing temperature;The optimal relative vapor injection pressure coefficient was 1.1~1.3,the COP of R1233zd(E) and R245fa was increased by 8.7% and 11.1%,respectively;The COP decreased with the increase of the primary compression volume ratio,and the COP reduction rate of the working fluid was 2.7% and 2.2%,respectively;The COP increased with the increase of evaporation temperature,the COP increase rate of working fluid was 10.1% and 10.7%,respectively;The COP decreased with the increase of condensation temperature,and the COP reduction rate of working fluid was 9.7% and 10.8%, respectively.

For the problem of gas-liquid transportation in the test circuit of natural gas hydrate synthesis system,a design of axialflow multiphase pump was proposed. Based on N-S equation and SST k-ω turbulence model,numerical simulation of the internal flow was applied to the multiphase pump,the difference of external characteristics under different inlet gas volume fractions (IGVF=0 and IGVF=50%) was compared and analyzed,and the internal flow law was revealed. The results show that when IGVF=0 and IGVF=50%,the head decreases monotonously with the increase of flow rate;the efficiency increases first and then decreases with the increase of flow rate,and the efficiency when IGVF=0 is about 1% higher than that when IGVF=50%;the shaft power decreases monotonously with the increase of flow rate,and the shaft power when IGVF=0 is about two times of that when IGVF=50%. And the prototype was made and applied in the test circuit of natural gas hydrate synthesis system,and it was verified that the multiphase pump has strong gas-liquid transportation capacity. The multiphase pump developed can be used in the test circuit of natural gas hydrate synthesis system or other high-pressure gas-liquid transportation scenarios.

At present,the structural optimization of the cyclone separator is mainly limited to the single-factor optimization of the control variable method,which can not accurately reflect the separation efficiency of the cyclone separator under the comprehensive factor condition,and the subtle changes in the structure and the interaction are difficult to control,therefore,it is difficult to further improve its separation efficiency. In order to solve this problem,a parameter optimization method based on response surface method was proposed for the first stage cyclone separator in catalytic cracking unit. The structural parameters of the cyclone separator were optimized by using the inclination angle α of taper pipe section,the inserting depth s of the exhaust pipe and the diameter De of the exhaust pipe,which have significant influence on separation efficiency,as the design variables and by using the separation efficiency and the pressure drop as the objective function. The results show that the efficiency of the cyclone separator was increased from the original 84.3% to 90.4% by using the response surface optimization method,and the velocity,pressure drop and separation efficiency before and after optimization were compared and analyzed. The response surface optimization method can intelligently optimize the combination of structural parameters from global perspective,shorten the CAD modeling and grid division time,and can achieve interactive optimization at the same time under multi-parameter conditions,effectively improving the efficiency;through numerical simulation and test, it was proved that the separation efficiency of optimized cyclone separator was better than that before optimization,the optimized cyclone separator has good symmetry of the velocity distribution,big speed difference and high separation efficiency,and can complete full separation task of smaller particles (particle size=12 μm) those before optimization.

The efficiency of the reciprocating compressor is mainly determined by air valves.The unsteady flow of the gas causes the abnormal movement (flutter and delayed closing) of the valve,and is also the main cause of the loss of gas flow. In this paper,the standard k-ε model is used to numerically simulate the flow field of suction valve and the ratio of inlet area to outlet area. The results show that the vortex areas on both sides of the valve outlet increase with the inclination angle of suction valve port,which will cause higher pressure loss of fluid. In addition,the smaller the ratio of the inlet area to outlet flow area of the suction valve,the less the pressure loss of the fluid. Finally,the correctness of the simulation was verified by tests.

The performance of oil-gas separator of scroll compressor for electric vehicle air conditioner plays a significant role in the stable operation of the air conditioning system and the lubrication and sealing of compressor. In view of small size of such oil-gas separator,it is required to have the characteristics of low pressure drop,high separating efficiency and wide application range of rotational speed. In order to explore the internal flow law,pressure drop and separation efficiency with the change of rotational speed,the Reynolds stress model (RSM) suitable for strongly swirling flow was chosen firstly,and the streamline diagram and velocity distribution of the fluid in the oil-gas separator were simulated. The DPM model was used to simulate the gas-liquid two-phase flow,and calculate the separation efficiency and fluid pressure drop of the lubricating oil in the oil-gas separator. The analysis results show that the gas performs quasi-free vortex flow and quasi-forced vortex flow in the oil-gas separator. The separation efficiency increases with the increase of the oil droplet size. When the compressor speed is low,the separation efficiency decreases sharply with the decrease of the rotational speed,and the pressure drop increases in proportion to the square of the rotational speed. Finally, the method for optimizing the design of the electric scroll compressor oil-gas separator was given.

This paper is aimed at the realization method and control logic of variable-pressure and energy-saving water supply strategy for parallel pumps by theoretical and experimental research. The PLC, combined with frequency converters, has been used as control-system of the new control strategy. In addition, the intelligent variable-pressure control was realized by modeling water demand estimation for piping system, variable-pressure control and the pump increased or decreased control, based on energy-efficiency condition. Suggested by the experiment results, the water demand estimation model is reliable with high sensibility and accuracy up to 90%. Besides, the control effect and energy-efficiency of pumps are improved effectively owing to the optimization control strategy. The obtained results can be referred by both the energy-saving optimization of parallel pumping system and the development of variable-pressure water supply mode.

In order to study the effect of blade thickness distribution on the performance of the centrifugal pump,three models of different blade thickness distribution were designed with other parameters of the volute and impeller fixed. The external characteristic and pressure pulsation were obtained by using steady-state and unsteady numerical simulations,respectively,and comparative analysis was made in combination with the internal flow structure. The results show that the parabolic non-uniform blade thickness distribution can significantly improve the performance of the centrifugal pump. Compared with the initial model,the model with larger thickness increases the head by 0.38 m and the efficiency by 3.07% under design conditions. The non-uniform blade thickness distribution can improve the flow field in the pump. By reducing the variation gradient of the blade load at the middle of the impeller,the axial vortex between the blades is effectively reduced,but the flow separation at the trailing edge is aggravated to a certain extent.The main frequency of unsteady pressure pulsation in the pump is concentrated on the blade passing frequency. Due to the nonuniform blade thickness distribution,the amplitudes of pressure pulsation at different position in the pump can be effectively reduced.Compared with the initial model,the average pulsation amplitudes at blade passing frequency of the two thickness optimization models are reduced by 21.7% and 33.5%,respectively,which weakens the flow-induced vibration of the pump during operation.

By taking a single-stage centrifugal compressor as the research object,a real-time monitoring system for the dynamic operation characteristics of the compressor was established.The surge experiment was carried out by controlling the opening of the exhaust regulating valve.Based on this,the active control casing injection (ACCI) for stability enhancement was designed and realized,and the surge margin was improved by hole-injecting high-speed air flow into the impeller passage.The research results show that the amplitude of pressure fluctuation at the outlet is much higher than that at the inlet,and the initial moment when the flow in the intake pipe enters the deep surge lags behind the initial moment when the flow in the exhaust pipe enters the deep surge.The casing injection increases the exhaust pressure while increasing the surge margin,and the increase of the injection massflow makes the stability enhancement effect more significant.The casing injection improves the flow condition in the region near the blade tip.

The characteristics of molten salt were briefly introduced,type selection requirements,structural features of the pump and precautions in the design were analyzed,the application fields and production status of molten salt pump at home and abroad were introduced,and finally the future development direction of the molten salt pump was pointed out.

For the key O-ring seal in current blind mating fluid connector for an equipment could not be plugged under pressure when the connector was turned on and it was in the flow passage,and a filter device needs to be equipped,the causes for potential reliability and safety risks and problems occurring in use were analyzed. The working principle of a new type of blind mating connector was introduced. All the seal rings were not exposed in the fluid with relatively large speed when the connector was turned on,they are not easy to damage due to plugging misoperation under certain pressure and the requirements for purity of the cooling liquid are low,which makes them possible to work without filtration assistors. In the final part,the related verification experiments for the new connector were introduced.

With the development of underwater cleaning technology for Marine structures,a new cavitation jet cleaning technology with the characteristics of high efficiency,safety,environmental protection and energy saving has also begun to emerge in underwater cleaning operations.The self-excited vibration cavitation jet can be used to perform the functions of rapid cleaning and cutting which combine the characteristics of cavitation jet and pulse jet. It is important to achieve a better cavitation effect. Based on the traditional Helmholtz nozzles,this paper adds an expansion tube at the nozzle's exit part which is used to enhance the effect of cavitation. In the meanwhile,a parametric study based on the main dimensions of the new Helmholtz nozzle such as the nozzle's height,width,angle of expansion pipe and pump pressure has been conducted using the numerical simulation method.. Critical parameters for creating a better cavitation effect have been found. The research findings can not only lay a theoretical foundation on the future experiments,but also provide some references for the design optimization of Helmholtz nozzles.

The change of working condition puts forward higher requirements to the optimization of air source heat pump system, and the ambient temperature as an important influence parameter need a large number of experiments to find its influence rule to the air source heat pump water heater to make the corresponding control strategy. In this paper, air-source heat pump water heater experiment is carried out in different simulated ambient temperature. It could be concluded by analyzed the result that the superheat temperature decreases with the decreasing of ambient temperature, the heating capacity of the system is related to the superheat degree. The lower the superheat temperature is, the larger the heating capacity is. The heating capacity begins to drop when the superheat temperature is 0℃. Moreover, as the ambient temperature decreases, the pressure ratio of the system increases, the exhaust gas temperature rises and the superheat temperature decrease. Compressor suction liquid entrainment will increase the power consumption, but it can effectively reduce the exhaust temperature. Furthermore, the average COP of COP_a is decreased with the decrease of ambient temperature. In sum, the lower the temperature is, the worse the heating effect is, and the longer the heating time is.

Heat pump steam system is a kind of energy-saving and environment-friendly steam generation system.In order to research the actual application of the heat pump steam system,a test platform for the heat pump steam system was designed and built. The running effect of the heat pump steam system was researched through theoretical analysis and testing. The results show that when the heat pump steam system generates steam at the temperature of 110℃(0.11 MPa,7.68 kg/h),the entrainment coefficient of the ejector is 0.60 and COP_hps of the system is 1.15;and when it generates steam at 115℃(0.12 MPa,14.10 kg/h),the entrainment coefficient of the ejector is 0.47 and COP_hps of the system is 1.17.

In view of the problem that outdoor heat exchanger frosting of electric vehicle heat pump system will seriously degrade the system performance and increase the instability,based on the study of the reverse cycle defrosting mode commonly used in automobiles,a hot gas bypass defrosting system was designed and built. The defrosting performance of the two modes under different environmental conditions was experimentally studied,and the operation characteristics of the two defrosting modes were analyzed,and the range of electric vehicle under two defrosting modes was estimated by theoretical derivation. The results show that,at 5 ~ -5 ℃ ambient temperature,the reverse cycle defrosting time is 80~400 s,and the average power consumption during the defrosting is 618~1 008 W. The hot gas bypass defrosting takes 350~600 s,and the average power consumption is 1 383 ~ 1 621 W. Compared with the reverse cycle defrosting,the hot gas bypass defrosting time increases by 200~270 s,the power consumption increases by 613~765 W,and the range decreases by 1.9%~3.8%. However,it is beneficial to ensure the comfort in the cabin during the defrosting process. When the ambient temperature is below 0 ℃,closing the outdoor heat exchanger fan during the defrosting process can reduce the air side heat transfer loss and improve the defrosting efficiency.

Concerning the fan system with the long pipelines connected on the inlet and outlet,the structural vibration noise is the main component of the external radiated noise,and is caused by the volute vibration which is excited by the unsteadyflow.Based on the vibrational noise of fan volute casing,a method of numerical calculation of unidirectional coupling of fluid-structure-sound was proposed,and the rationality of this method was verified by vibration measurement of the volute casing.Then the positions of the noise source of the volute casing was studied and revealed applying the panel acoustic contribution analysis (PACA) method. It can be concluded that the vibrational noise of volute casing at blade passing frequency (BPF) is predominant,and the normal vibration of the volute was the decisive factor that determined the volute surface acoustic radiation.The analysis results of the PACA of each component of the volute show that the outlet of the side volute close to the volute tongue area,and the volute front and back panel at 180° near the volute tongue,were the main noise source regions.

For the problem of the severe cavitation caused by the water droplet labyrinth regulating valve in the super-(super-) critical unit under high temperature and high pressure conditions, based on the theory of computational fluid dynamics and cavitation mechanism, the standard k-ε turbulence model, Mixture model and Schnerr-Sauer cavitation model were selected to compare the structural performance of the control valves before and after improvement at typical openings in terms of pressure, velocity, gas volume fraction, etc. The calculation results show that the original disc structure has a large pressure drop, up to 19.95 MPa at maximum, and a high flow rate, up to 237 m/s at maximum, which leads to severe cavitation, and the gas phase volume fraction is even as high as 1. The maximum pressure drop in the disc flow passage was reduced by 52.5%, the maximum speed was reduced by 38.8%, and the maximum gas phase volume fraction was reduced to 0.18. It was proved that increasing the cofferdam can effectively control the pressure drop and flow velocity in the valve and reduce the degree of cavitation damage. In addition, appropriately increasing the height of the cofferdam is conducive to suppressing the occurrence of cavitation, but an excessively high height will cause the cavitation area to shift to the cofferdam, and at the same time, an unstable flow field will be formed, which will affect the valve opening and closing characteristics.

The phase change thermal storage device was combined with air source heat pump air conditioning system to mainly study the condensing heat recovery experimentally under mode of partial condensing heat recovery by using the single phase change material (pure paraffin) and composite phase change material (pure paraffin/foamed copper) in the phase change heat storage tank. Through the experimental data, the improvements in system parameters such as change rates of heat storage temperature of the heat storage material during partial condensing heat recovery as well as suction and exhaust pressure,refrigeration energy efficiency ratio and comprehensive energy efficiency coefficient of the system were compared with/without addition of thermal conductive materials.The results show that the heat storage rate of the composite phase change material was increased by 6.5%, and the temperature difference was decreased by 44.1%,and the temperature distribution was more uniform compared with those of single phase change material when the air source heat pump air-conditioning system was under partial condensation heat recovery condition.In terms of system performance, EER and COP_t was increased by 4.1% and 30.5%,respectively,and all values of heat storage system with composite phase change materials were improved. The experimental results and conclusions provide reference for the promotion and further research of heat storage with composite phase change materials.

The ambient temperature and the water temperature in the tank are important factors affecting the performance of air source heat pump water heater(ASHPWH),the coefficient of performance (COP) about an air source heat pump water heater during water heating and hot water supplying were tested in enthalpy-difference test-bed.The main tested results are as follows:the COP of ASHPWH is more than 3 when the water demand is guaranteed at the temperature of 45℃ with the ambient temperature above 20℃,the COP of ASHPWH is more than 4 when the water demand is guaranteed at the temperature of 50℃ with the ambient temperature above 30℃,the COP of ASHPWH maintains at around 2 when the water demand is guaranteed at the temperature of 40℃ with the ambient temperature below 2℃.In accordance with the typical annul average daily temperature distribution,5 temperature ranges are divided.The operating performance of each temperature range was characterized by the COP of the water heating stage under 5 tested conditions.Considering the influence of seasonal cold degree on the frequency of water consumption,given constant heating capacity,the annul performance of the tested ASHPWH is evaluated respectively in cold area,hot summer and cold winter area,hot summer and warm winter area.It is shown that ASHPWH is most applicable in hot summer and warm winter area,it also has the potential to be used in cold areas.

The orbiting scroll of the existing electric scroll compressor is subjected to axial gas force and axial balance force in the direction of the spindle axis,and the axial balance force frequently changes due to the operation of the electric scroll compressor often under variable speed conditions,resulting in instability of the axial stress of the orbiting scroll,which further influences the compressor performance.For this problem,the transient process of lubricating oil stirring in the back pressure chamber of the balance weight at different speeds was simulated using FLUENT sliding grid technology,and the speed cloud and streamline diagram of the lubricating oil were obtained,and it was found that the stirring of the balance weight would cause periodical fluctuation of the axial balance force,and as the rotational speed increases,the axial balance force increases and the average axial balance force decreases. Finally,in combination with the variation law of axial balance force and axial gas force with the rotation angle of the main shaft,the optimization design method of coordinated superposition of variable phase and axial force was proposed. It was found that the method can reduce the amplitude of the axial balance force and make the orbiting scroll run more smoothly, which can provide a basis for the design of the electric scroll compressor.

The geometric parameters of the suction valve of the reciprocating compressor will affect the flow characteristics of the inlet fluid channel.In order to visualize the process，Solidworks is used to establish a three-dimensional model of the cylinder suction channel and valve tongue for a reciprocating compressor produced by a company.FLUENT software is used to set the fluid-structure coupling surface at the interface between the valve tongue and the fluid channel，and the dynamic grid option is loaded to simulate the transient dynamics of the compressor suction process.Predefinition is made for the compressor piston motion equation by writing into the Profile，and finally，the time-dependent characteristics of the valve tongue surface and the cylinder stress distribution，the valve tongue displacement and the inlet flow rate of the suction valve plate of different thicknesses in the open and fully opened state are obtained，and in combination with experiments，the accuracy of the numerical simulation is verified，which provides a theoretical basis for further optimizing the valve structure and studying the aerodynamic noise caused by the pressure pulsation in the cylinder.

For the problem of insufficient aerodynamic performance of cleaning fans in textile workshops,a combination of numerical simulation and experiments was used to study it.With static pressure,air volume and efficiency as the main parameters,the blade profile and inlet and outlet installation angles were designed separately by group optimization,and the aerodynamic performance of the fans and their flow fields were analyzed by numerical calculation for each scheme.The results show that for the new blade profile fitted by Bezier function,the blade runner area is increased by 9.4%,the increase of the curvature of the windward side and the width makes the distribution of the flow field in the blade channel better than the original blade,and the pressure distribution smoother,the effect on the static pressure increase is most obvious,an increase of 10.9% compared with the original fan;With reduction of flow loss as the goal,through the particle swarm optimization method,it is known that the appropriate change in the inlet and outlet angle has the most obvious effect on increase of the air volume and the efficiency.the increase is 7.2% and 5.1% respectively compared with the original fan.The final fan model was determined by combining the optimal solutions of the two groups of solutions.After optimization,the static pressure of the fan is increased by 12.9%,the air volume is increased by 8.1%,and the efficiency is increased by 7.2%,which are greater than the results of single optimization of each scheme in the group design and meet the actual production requirements.The grouping optimization can avoid the synergistic interference effect between the rotating and stationary components and maximize the performance of the fan.

The radiator with heat pipe and the radiator without heat pipe were designed on the hot ends of two types of semiconductor cooler--TEC1-12704 and TEC1-12706, at the same time, the experimental device for two-stage cooling radiator with heat pipe was designed under the condition of separated current input, and the influence of hot end heat dissipation condition on the cold end temperature was analyzed by the experiment. The experimental results show that the radiator with a heat pipe for dissipation heat can enhance the heat dissipation at the hot end. The cold end temperature of the semiconductor cooler is related to the heat dissipation capacity of the radiator. Under the condition of limited heat dissipation capacity, the temperature of the cold end first increases and then decreases with the increase of the input current. Under the condition of ensuring the heat dissipation capacity, the temperature of the cold end decreases with the increase of the input current, and decreases with the decrease of the temperature of the hot end. The minimum temperature of the cold end can reach -38.6℃ when two-stage refrigeration with separated current input is adopted for the two-sheet TEC1-12706 semiconductor cooler. The experimental results show that improving the heat dissipation conditions of the hot end can improve the performance of the monolithic semiconductor cooler. At the same time, the temperature of the cold end can be substantially reduced by using two-stage refrigeration with separated current input under the optimal heat dissipation condition, which is of great significance to improve the working temperature difference of semiconductor cooler.

Impeller parameters have great effect on the performance of the cross flow fan. Based on the blade provided by a company,the influences of several important blade parameters such as leading radiu(R_i),rear radiu(R_o),blade tilt angle (a) and camber angle(γ) on the flow field and performance of the cross flow fan,has been studied by two-dimensional steady simulation.The results show that,the ratio of R_i and R_o has great effect on boundary-layer separation of the blade surface,the boundary layer separation is inhibited and higher outlet flow rate is obtained when R_i/R_o >1. Blade tilt angle a of the prototype blade can be chosen in the ranges 25° ≤ a ≤ 30°,and in which range,the fluctuation of the impeller inlet flow decreases with a increases. The greater the camber angle γ,the more the impeller works on the airflow. Moreover,when γ is equal to 90°,the flow rate achieves the maximum of 716.47 m³/h,enhanced 4.04% compared to the original impeller.