In this paper, the effect of oil injection flow rate on the performance of a variable speed twin-screw compressor was investigated experimentally. Comprehensive experiments were conducted at different compressor rotational speeds and oil injection flow rates. As the rotational speed increased from 1000 to 3000 rpm, the compressor volumetric and adiabatic efficiencies increased while the specific power consumption decreased. However, the oil injection flow rate showed different influences on the compressor performance. As the oil injection flow rate increased from 27 to 50 L/min, the adiabatic and volumetric efficiencies increased while the compressor discharge temperature and specific power decreased. Further increases in the oil injection flow rate had little effect on compressor performance at flow rates above 50 L/min. The analysis indicated that the oil injection flow rate was limited by the discharge temperature at low compressor rotational speeds and was a trade-off among two efficiencies and specific power consumption at high rotational speeds.

The flow in the gap between the reed and the valve seat has a significant influence on the dynamic characteristics of the reed valve used in reciprocating compressors. The fluid–structure interaction (FSI) method is an effective method for studying reciprocating compressors. A three-dimensional FSI model of a reciprocating compressor with a reed valve is established in this paper, which has an important influence on the flow rate characteristic of reciprocating compressors. Furthermore, an experimental investigation is implemented to verify the FSI model. Based on the established FSI model, the pressure distribution on the reed valve surface is identified by varying the height of the suction valve limiter and the rotational speed of the compressor, which has an important effect on the dynamic characteristics of the reed valve. Although the low-pressure region, due to the Bernoulli effect on the surface of the reed, hinders the rapid opening of the valve to some extent, it is obviously beneficial to the timely closure of the valve and increases the volumetric efficiency of the compressor. Moreover, the optimal height of the valve limiter and the appropriate rotational speed of the compressor are obtained.

In order to accurately calculate the geometric characteristics of the twin-screw compressor and obtain the optimal profile parameters, a calculation method for the geometric characteristics of twin-screw compressors was proposed to simplify the profile parameter design in this paper. In this method, the database of geometric characteristics is established by back-propagation (BP) neural network, and the genetic algorithm is used to find the optimal profile design parameters. The effects of training methods and hidden layers on the calculation accuracy of neural network are discussed. The effects of profile parameters, including inner radius of the male rotor, protection angle, radius of the elliptic arc, outer radius of the female rotor on the comprehensive evaluation value composed of length of the contact line, blow hole area and area utilization rate, are analyzed. The results show that the time consumed for the database established by BP neural network is 92.8% shorter than that of the traditional method and the error is within 1.5% of the traditional method. Based on the genetic algorithm, compared with the original profile, the blow hole area of the screw compressor profile optimized by genetic algorithm is reduced by 54.8%, the length of contact line is increased by 1.57% and the area utilization rate is increased by 0.32%. The CFD numerical model is used to verify the optimization method, and it can be observed that the leakage through the blow hole of the optimized model is reduced, which makes the average mass flow rate increase by 5.2%, indicating the effectiveness of the rotor profile parameter optimization method.

Introduction: The spiral tube heat storage tank is a highly efficient device designed for storing and releasing heat, utilizing a spiral tube structure. Its key advantages include efficiency, reliability, and flexibility, making it suitable for a wide range of conditions, from high temperatures and pressures to low temperatures and high vacuums.Methods: This study aims to analyze phase change heat storage in spiral tube heat storage tanks using numerical simulation.Results: It explores the impact of varying water supply temperatures on heat transfer efficiency and the melting behavior of phase change materials within the tanks. Proposed enhancements, informed by numerical simulation results, seek to improve heat transfer efficiency. Simulation findings indicate that charging efficiency rises with increased temperature differentials, akin to sleeve-type heat exchangers.Discussion: Calculations suggest faster melting of phase change materials at the central position of the tank’s spiral tube, with slower melting near the vessel wall. Consequently, reducing the number of spiral tubes in the middle is suggested for future structural optimization.

Straight bevel gears are widely used in mining equipment, ships, heavy industrial equipment, and other fields due to their high capacity and robust transmission. Accurate measurements are essential in order to determine the quality of bevel gears. We propose a method for measuring the accuracy of the top surface profile of the straight bevel gear teeth based on binocular visual technology, computer graphics, error theory, and statistical calculations. In our method, multiple measurement circles are established at equal intervals from the small end of the top surface of the gear tooth to the large end, and the coordinates of the intersection points of these circles with the tooth top edge lines of the gear teeth are extracted. The coordinates of these intersections are fitted to the top surface of the tooth based on NURBS surface theory. The surface profile error between the fitted top surface of the tooth and the designed surface is measured and determined based on the product use requirements, and if this is less than a given threshold, the product is acceptable. With a module of 5 and an eight-level precision, such as the straight bevel gear, the minimum surface profile error measured was −0.0026 mm. These results demonstrate that our method can be used to measure surface profile errors in the straight bevel gears, which will broaden the field of in-depth measurements for the straight bevel gears.

The refrigerant mass flow rate of a refrigerator compressor can only be measured by a mass flow meter and heat balance method. This paper focuses on the expansion and compression phase in which the compressor cylinder is closed, and proposes a measurement method of instantaneous mass flow of the refrigerator compressor. The comparison of the experimental pressure variation in the p–V diagram and the theoretical adiabatic process implied that the expansion and compression process of the refrigerator compressor approximated the adiabatic process. Based on the approximations and the experimental p–V diagram, a calculation method for refrigerant mass in the cylinder during the expansion and compression phase is proposed. Subsequently, the mass flow of the refrigerator compressor can be obtained. Furthermore, compared with experimental data and based on the method proposed in this paper, the error of the mass flow rate obtained is less than 3.13%. Based on this calculation method and the experimental p–V diagram, the influence of suction pressure on compressor performance is investigated.