Twin-screw vacuum pumps (TSVPs) are key components in integrated circuit manufacturing processes that operate under high vacuum conditions. Accurately predicting the performance of TSVPs under rarefied gas and thermal deformation effects remains challenging. To address this challenge, this study proposes a coupled thermal-fluid-structure model that integrates a control chamber model, a rarefied gas leakage model, a thermal network model, and a variable thermal channel model. Unlike conventional approaches based on fixed channel dimensions or isothermal assumptions, the proposed model dynamically accounts for gas rarefaction, suction process, discharge backflow, heat transfer, and thermal deformation. This capability enables accurate performance prediction of TSVPs under both cold and thermal states. Temperature distributions and pumping characteristics of the TSVP were experimentally tested. Based on this model, influences of the inlet pressure, thermal and cold states, and channel dimensions on the thermodynamic characteristics and performance of TSVPs were systematically investigated. Results indicate that, as the inlet pressure decreases, an increasing number of chambers sequentially reach their specific ultimate pressure, from the discharge end to the suction end. Thermal deformation gradients, narrowing leakage channels and under-compression simultaneously occur after long-term operation. The leakage of the flat channel increases from 23% on the discharge side to 79% on the suction side. The leakage of the thin slit channel shows the opposite trend, dropping from 63% to 12%. Thin slit channel dimensions should be reduced in low pressure chambers, while flat plate channel dimensions should be reduced in high pressure chambers to optimize efficiency and power consumption.

Automotives with internal combustion engines inherently experience thermal losses. Waste heat recovery systems incorporating scroll expanders improve efficiency by converting thermal energy into output power, yet face challenges from variable heat sources. To address this, this study proposed a theoretical model for asymmetric scroll expanders to improve the expansion ratio and adapt to fluctuations in heat source temperature and mass flow rate. The influence of profile variables on the geometric performance was investigated, and a generalized numerical framework for the expansion process was established, analyzing unsteady flow in the working chambers. Under different input parameters, shaft power and filling factor were calculated, with variations in isentropic efficiency and total efficiency examined. Exergy analysis further assessed energy conversion efficiency during the expansion process. The results indicate that decreasing the initial angle optimizes modified area coefficient and increases the built-in volume ratio. Asynchronous discharge from working chambers induces localized high temperatures within the discharge region. Filling factor is more sensitive to rotational speed variations than to suction pressure. Efficiency increases with pressure ratio, reaching a peak of 78.46% for isentropic efficiency and 19.51% for total efficiency before declining. Exergy efficiency drops by approximately 11.61% due to greater flow losses and mechanical friction at higher rotational speeds.

As a critical component in the production of integrated circuits, the twin-screw vacuum pump (TSVP) faces increasingly stringent requirements in improving vacuum performance. However, under high vacuum conditions, rarefied gas flows span multiple flow regimes and exhibit complicated transport characteristics, which cannot be described by traditional prediction models based on the continuum assumption. In this study, the lattice Boltzmann method (LBM) was employed to simulate the rarefied gas flow in the microchannels of TSVP. Based on the simulation results, a novel prediction model for leakage flows with multiple flow regimes was developed in microchannels, considering effects of gas rarefaction, channel geometry and wall motion on gas flow behavior. The correctness of the prediction model was validated by experiments. Results show that the proposed model is more accurate than the traditional models in predicting leakage flows with multiple flow regimes, and its deviations is less than 2 % compared with the experimental data. In the thin slit microchannels of TSVP, as the rarefaction parameter increases from 0.02 to 100, the reduced flow rate increases by 175 %, indicating that the flow regime transitions to continuum flow. The findings of this study can support the development of TSVPs as well as other vacuum equipment.

Dry claw vacuum pumps (DCVPs), characterized by oil-free operation, high reliability, and particle handling capability, are widely used in many industries such as semiconductor manufacturing. To reveal the working mechanism and operating characteristics of DCVPs, this study proposed a novel profile of a symmetric involute double-claw rotor and established a zero-dimensional mathematical model of its working process. 3-D numerical simulations were conducted and the effectiveness of the model was validated through experiments. The pressure fields and compression processes under variable inlet pressures were investigated. Mass flow fluctuation, axial and radial gas forces, and gas resistance torques of the DCVP were analyzed. The effects of the inlet pressure on the power consumption and volumetric efficiency were systematically studied. Results indicate that the leakage pressurization process dominates when the inlet pressure is below 7.5 kPa. The decrease of the inlet and outlet port areas will intensify the mass flow fluctuation. As the inlet pressure decreases, the axial and radial forces as well as the gas resistance torque increase, whereas the volumetric efficiency and indicated work decrease significantly. The findings lay a theoretical foundation for the optimization of the pump and the enhancement of energy efficiency in vacuum systems.

The growing demand for high-efficiency vacuum equipment in semiconductor industry has driven the need for optimized TSVPs. Proper adjustment of the pitch distribution is an effective way to improve the thermodynamic performance of TSVPs. However, the strongly coupled effects of compression, leakage, and heat transfer hinder the optimization of multiple performance objectives. To address this, a multi-objective optimization framework based on NSGA-II was established to systematically optimize different screw pitch distribution strategies. Independent sets of optimization variables were defined for each pitch distribution strategy. The performance of the original and optimized TSVPs was evaluated to reveal the trade-offs among volumetric efficiency, specific power, and exhaust temperature. The pumping performance and thermal characteristics were experimentally obtained to validate the optimization results. Results show that the optimized rotors achieve smoother compression processes and higher gas pressures before the exhaust port opens, which reduces under-compression and improves energy efficiency. For the optimized TCP rotor, the specific power is decreased by 43.4 %, and the exhaust temperature is decreased by 17 %. Under rarefied conditions, gas pressure plays an important role in heat transfer; higher-pressure rarefied gas exhibits an enhanced heat transfer coefficient, leading to more efficient gas-casing heat transfer and higher casing temperatures.

Abstract Heat pumps are critical for enhancing the driving range of electric vehicles. Conventional scroll compressors suffer low efficiency and poor adaptability under extreme conditions, leading to insufficient heating and cooling performance and significant energy consumption. To address this issue, this study presented a theoretical framework for hybrid scroll profiles, demonstrating a compressor with fewer wraps and larger built-in volume ratio. The impact of base and modified scroll profile on geometric performance was analyzed. Numerical simulations were performed to investigate the refrigerant flow distribution and thermodynamic characteristics of the compressor. Furthermore, a performance prediction model for isentropic and volume efficiencies was developed using the Response Surface Methodology (RSM), revealing strong nonlinear interactions between operating parameters. The results show that increasing the modified angle alters the connection between the base and modified scroll profiles, impacting compression ratio and chamber volume. Flow in the working chamber is asymmetric, with high vorticity regions concentrated at clearances and the tail of scroll wraps. As the pressure ratio increases, thermal losses become more significant, resulting in a 6.9% decrease in isentropic efficiency. In addition, the increase in rotational speed has a more pronounced effect on volume efficiency, improving it more than isentropic efficiency. Further analysis identifies an optimal combination of operating parameters, achieving a predicted isentropic efficiency of 77.6% and volume efficiency of 88.1%.

With the integrated development of new energy and oil and gas production, introducing wind-solar-storage microgrids in coalbed methane well screw pump discharge systems enhances the renewable energy proportion while promoting green development. However, the cyclical, volatile, and random characteristics of wind and photovoltaic generation create scheduling challenges, with insufficient green power consumption reducing renewable energy utilization efficiency and increasing grid dependence. This study establishes an operation scheduling optimization model for coalbed methane well screw pump discharge systems under wind-solar-storage microgrids, minimizing daily operation costs with screw pump rotational speed as decision variables. The model incorporates power constraints of generation units and production constraints of screw pumps, solved using particle swarm optimization. Results demonstrate that energy storage batteries effectively smooth wind and photovoltaic fluctuations, enhance regulation capabilities, and improve green power utilization while reducing grid purchases and system operation costs. At different coalbed methane extraction stages, the model optimally adjusts screw pump rotational speed according to renewable generation, ensuring high pump efficiency while minimizing operation costs, enhancing green power consumption capacity, and meeting daily drainage requirements.

The Roots vacuum pump is widely adopted as a mechanical booster in dry vacuum systems, so improving its performance is essential. However, pump efficiency is significantly limited by gas leakage through radial clearances. Conventional Roots pumps adopt a constant radial clearance (CRC) at all rotor positions, and such a structure increases the risk of gas leakage under large pressure differences. This work proposed a novel Roots vacuum pump with variable radial clearance (VRC), which is realized by an eccentric cylindrical inner surface offset from the rotor rotation center. The effects of the design parameters of the VRC structure on the geometric performance of Roots pumps were investigated. A three-dimensional unsteady CFD model was developed and validated against experimental data during working process. The flow field distribution, pressurization characteristics and energy consumption of the VRC pump were compared with those of the conventional CRC pump. Results show that the VRC structure reduces external leakage and improves the actual pumping speed and volumetric efficiency. The VRC Roots pump reverses the flow direction of gas leakage through the radial clearance and reduces the pulsation coefficient of inlet pressure by 2.76%. The actual pumping speed is raised by 1.82%, with the volumetric efficiency increasing from 78.96% to 80.39%.

Metal and rubber-covered rotors represent the two most prevalent configurations in rotary lobe pumps, each exhibiting distinct performance characteristics tailored to specific applications. Metal rotors are predominantly employed in food processing, pharmaceuticals, and high-temperature fluid handling due to their robustness and chemical resistance, whereas rubber-covered rotors are widely utilized in petroleum/chemical, environmental protection, paper manufacturing, and corrosive chemical industries for their superior sealing and wear resistance. This study developed a dedicated self-priming performance test rig to systematically evaluate the external characteristics and self-priming behavior of both rotor types during water transport at room temperature (25 degrees C) and 7-m suction height. The investigation comprehensively compared operational performance across a wide rotational speed range (250-400 rpm), including self-priming duration, energy consumption, flow characteristics, and pressure-flow dynamics. Key findings reveal that rubber-covered rotors demonstrate significant advantages in low-speed self-priming performance, achieving a 50% reduction in self-priming time at 250 rpm (12.5% reduction at 400 rpm). While their volumetric efficiency increases by 13% with rising rotational speed during self-priming (compared to 28% for metal rotors), the beneficial effect of speed augmentation is more pronounced for metal rotors. Notably, rubber-covered rotors exhibit superior sealing performance but show greater instability in pressure and torque at high speeds, limiting their applicability in high-speed operations. These results provide critical insights for pump selection and design optimization, demonstrating that rubbercovered rotors are particularly suitable for low-speed, high-viscosity applications, while metal rotors offer better high-speed performance. The findings contribute to the theoretical foundation for rotor design in rotary lobe pumps.

Screw rotors, as the core components of twin-screw vacuum pumps, significantly determine their operational efficiency. The conventional cycloid-involute screw rotor suffers from problems such as an excessively large central angle, while the double-cycloid screw rotor demonstrates inferior meshing performance. In this study, two new smooth cross-sectional profiles were generated based on the screw rotor meshing principle. A "curveplane-solid" methodology was developed for rotor generation. The geometric properties of two novel types of screw rotors were comprehensively analyzed, and compared with those of conventional cycloid-involute screw rotors and double-cycloid screw rotors. The leakage characteristics of elliptical-arc screw rotors and doublecycloid screw rotors were investigated by numerical simulation, and their performance was compared by experiments. It is found that the elliptical-arc screw rotors feature a smaller leakage volume. The simulation results were experimentally verified. The ultimate pressure of the elliptical-arc screw rotors can reach 0.9 Pa based on the novel rotor generation method. Therefore, the new type of smooth screw rotors dramatically improves the pump geometric performance, and effectively alleviates the adverse effects of the working process. The finding of present study can provide support for the application development of screw vacuum pumps.

Transcritical CO2 presents broad application prospects in heat pump systems for electric vehicles, with the scroll compressor as the core component. The paper proposed a design method for asymmetric scroll wraps with variable thickness using trigonometric involutes. The relationship between modification parameters and geometric performance was discussed. Thermodynamic analysis was conducted to evaluate isentropic and volumetric efficiencies under different radial clearances. Exergy analysis examined the impact of suction temperature and rotational speed on exergy efficiency. Then, the flow characteristics of CO2 in the working chamber during the transcritical process were investigated. The results indicate that an increase in the modified arc radius R1 hinders the opening of the discharge port and adversely affects the improvement of the built-in volume ratio. Increasing radial clearance between 30 mu m and 200 mu m causes a decrease in isentropic efficiency by 40.82 % and volumetric efficiency by 28.91 % for the CO2 scroll compressor. Higher suction temperatures and rotational speeds reduce exergy destruction during compression, thereby improving exergy efficiency. Furthermore, the flow distribution is influenced by the thermophysical properties of CO2 across different phases, with the supercritical phase accounting for approximately 38.89 % of one cycle.

The claw circulating pump used in the proton exchange membrane fuel cell has a unique and inevitable overcompression process, which increases the power consumption, due to the special structure of claw rotors. With the aim of reducing the negative impacts of the over-compression process, a type of gear-claw rotors with a novel auxiliary working chamber was designed, and its geometric model was established. Then a new corresponding claw circulating pump was developed. The working process, pressure distribution, indicated power and specific power of the conventional circulating pumps were compared with those of the proposed gear-claw circulating pump by means of numerical simulations. It is found that the novel auxiliary working chamber effectively avoids secondary compression of the gas in the carryover by connecting the carryover and the suction chamber in the over-compression process. The indicated power of the gear-claw circulating pump with the auxiliary working chamber is reduced by 32.7 %, and its specific power is reduced by 33.0 %, compared with the conventional pump.

Multi-stage claw vacuum pumps are crucial in various industrial applications for efficiently achieving high vacuum levels compared to other positive displacement vacuum pumps. In order to elucidate the gas pressurization process of the multi-stage claw vacuum pump and clarify its structural design principles, the authors investigated a twin-stage claw vacuum pump as the main research subject, and analyzed its working characteristic. A thermodynamic model of the twin-stage claw vacuum pump describing the pressurization process was established, and the results were verified by means of experiments. Moreover, effects of the phase difference phi I-II, the first-stage discharge port angle theta d,I and the thickness ratio B1:B2 on pump performance were discussed. Results show that as phi I-II increases, the pump power of the first stage gradually increases, while the power of the second stage decreases and then increases. With the increase of theta d,I, the pump power decreases and then increases. When the suction pressure is 10 kPa, the specific power reaches its minimum value under B1: B2 = 2:1. As the suction pressure increases, the pump power gradually increases, and its specific power fells substantially and then levels out. These contents are of great significance for the design and optimization of multi-stage claw vacuum pumps.

Efficient and reliable structures are urgently needed for research on the output performance of scroll expanders, aimed at enhancing energy conversion efficiency in micro-compressed air energy storage (CAES) systems. To address these critical issues, this study proposed a fully meshing scroll expander with variable wrap thickness and presented a method for its generation. Thermodynamic characteristics of the expander were represented by establishing a quasi-dimensional model. An exergy analysis was conducted to determine the effect of the suction pressure on exergy efficiency. Furthermore, numerical simulations of unsteady flow within the expansion chamber were carried out to gain comprehensive understanding of working features. Factors contributing to the energy conversion performance in the expander were examined and the efficiency of the expander was evaluated. The results indicate that designing scroll wraps with variable thickness significantly enhances discharge capacity and increases built-in volume ratio. An ideal pressure ratio for the expander is identified as between 3.6 and 4.5. Additionally, by analyzing energy conversion performance under various combinations of rotational speeds and suction pressures, it has been determined that the expander exhibits an optimal efficiency region. Both energy and exergy evaluations revealed that increasing suction pressure does not effectively improve the performance of the expander.

The variable cross-sectional rotor is considered as a potential technology to further improve the performance of twin-screw vacuum pumps, due to its remarkable advantages of large internal volume ratio. In this study, a mathematical model of variable cross-sectional rotors was established to obtain its generation method. A novel type of variable cross-sectional rotor was constructed by using the proposed method, and this rotor exhibits superior sealing performance. The variable cross-sectional rotor was geometrically compared with the traditional equal cross-sectional rotor. Then the accuracy of the proposed generation method as well as the advance of the generated variable cross-sectional rotor were verified by experimental test results. Results show that this design method achieves the construction of high accuracy variable cross-sectional rotors by generating 3-D helical surfaces. Compared with the traditional equal cross-sectional rotor, the geometric pumping speed and internal volume ratio of the variable cross-sectional rotor are increased by 7.57 % and 10.45 %, respectively. The volumetric efficiency of the variable cross-sectional rotor is increased by 6.52 % and the time to reach the ultimate pressure is reduced by 9.42 %, demonstrating superior pumping and sealing performance.

Double-scroll can effectively increase the volume flow rate compared with the commonly used single-scroll structure, but its built-in volume ratio dramatically decreases. With the aim of improving the built-in volume ratio as well as compression ratio of the double-scroll compressor, this study presented a novel fully meshing profile for the double-scroll, or called double-scroll profile modification. A generation method of this modified double-scroll, general relationship between its geometric parameters, and its modified profile equations were obtained. The volume of the compression chamber under an arbitrary rotational angle was calculated, and effects of the geometric parameters on the performance of the modified double-scroll compressor were analyzed. A compressor performance test bench was built and experiments were carried out. Moreover, the thermodynamic characteristic and working process analysis of the double-scroll compressor were carried out. It is found out that the proposed modified double-scroll structure significantly increases the volume flow rate, reduces the friction velocity between the orbiting and fixed scroll, and decreases scroll dimension; meanwhile it also effectively increases the built-in volume ratio 33.8%.

Abstract Owing to the structure of the gear-claw rotor, working chambers of claw pumps are divided into small multi-chambers by a pair of intermeshing claw rotors in the mixing process, and the transient flow in multi-chambers is complicated, which results in the increase of the pump consumption. Hence, it is necessary to study the transient flow and working process of gear-claw hydrogen circulating pumps to optimize the pump performance. In this study, the meshing model of a high-order curve and its conjugate curve was proposed, and the profile composition of the gear-claw rotor was introduced. The influence of the radius ratio of claw addendum arc on the performance including relative carryover, built-in volume ratio and volume utilization was analyzed. The flow field of gear-claw hydrogen circulating pump including pressure and velocity field was analyzed by using numerical simulations. Furthermore, the p-V diagram of pumps was obtained. It is found that the gas in the compression chamber is mixed with the gas in the carryover, and the initial pressure in the compression chamber is 130.78kPa, which increases by 29.07% compared to the original initial pressure in the compression chamber. Therefore, an overcompression phenomenon at the end of the compression process (at the beginning of the discharge process) occurs.

The claw vacuum pump is extensively utilized in semiconductor, photovoltaic and aerospace industries because of its dry oil-free and compact structure. In order to reduce the power consumption of the claw vacuum pump caused by its special mixing process during operation, a novel pair of claw rotors was proposed. This innovation involves replacing the conventional circular arc at the dedendum of the claw rotors with an eccentric circular arc. A geometric model of the novel claw rotor was established, and the geometric characteristics of both the novel and conventional claw rotors were compared. Subsequently, the optimal design parameters were determined. The pressure distribution and power consumption of two claw vacuum pumps were analyzed with numerical simulations. Study results indicates that the power consumption of the proposed claw vacuum pump in the mixing process is reduced by 72.3 %, and the total power consumption is reduced by 12.6 % compared to the conventional pump. The study is of great significance for reducing power consumption of the claw vacuum pumps and improving application.

The number of lobes of multi-claw rotors determines the performance of claw vacuum pumps including the pumping speed, dynamic characteristics, and operating conditions. In order to reveal the effects of the number of lobes on rotor performance, in this study, a geometric model of multi-claw rotors was established. The structure and geometric performance of multi-claw rotors including suction port and discharge port, pumping speed, and volumetric utilization ratio were compared. Furthermore, a dynamic characteristic model of claw rotors was established, and, therefore, axial gas forces, radial gas forces, and gas resistance torques of multi-claw rotors were obtained. The results indicate that double-claw rotors increased 34.67 % and 4.59 % in terms of pumping speed and volumetric utilization ratio compared to single-claw rotors, and triple-claw rotors showed similar increases as double-claw rotors. The triple-claw rotors have a 49.39 % and 31.38 % reduction in compression duration compared to the double-claw rotors and single-claw rotors. The gas resistance torques of the multi-claw right rotors are consistently more than that of the left rotors, which demonstrates that the multi-claw right rotors are more suitable to serve as the driving rotors. The research contents of this paper are of great theoretical significance for the selection of rotor lobes and the design of claw vacuum pumps with prominent dynamic characteristics.