Research on the performance of a high pressure 5.3MPa twin screw compressor

High pressure twin screw compressors have been widely employed in fuel gas boosting and petrochemical industry. Recently, such compressors, whose maximum of discharging pressure is 5.3MPa, are also adopted in high temperature NH3 heat pumps and NH3/CO2 cascade refrigeration system. However, high pressure twin screw compressors are required to have large capacity, good performance and excellent stability at high operating pressure. In this paper, a semi-empirical model for open-type high pressure twin screw compressor is developed. Experimental research is conducted for identification of parameters, while validation is also made on the accuracy of the model. On the basis of theoretical and experimental research, the performance of the compressor, which includes volumetric efficiency, adiabatic efficiency, discharge temperature and lubricant oil flow rate/temperature, are illustrated. The change pattern of such features on the operating conditions, slide valve loadings and ambient features are then analyzed. Additionally, the stability test results of the high pressure twin screw compressor including the vibration and noise are also shown

Experimental Investigation on the Operating Characteristics of a Semi-hermetic Twin Screw Refrigeration Compressor by means of p-V Diagram

In this paper, a comprehensive experimental investigation is carried out to evaluate the operating characteristics of a semi-hermetic twin screw refrigeration compressor at different oil flow rates and slide valve positions under various conditions. The working volume pressure of the compressor is recorded by a serial of sensors arranged in consecutive positions in the housing. These measured pressure data are then transformed into an indicator diagram. Based on the p-V diagrams, the effect mechanism of some factors such as evaporation temperature, condensation temperature, slide valve positions, oil flow rates for the suction and discharge end bearings lubricating and oil flow rate returned from the suction pipe on the compressor performance and working process is analyzed. These results can be useful for optimum design of oil flow passage assembly and selection of optimal built-in volume ratio to improve the energy efficiency of refrigeration system with semi-hermetic twin screw compressor

Real-time tracking of surgical instruments based on spatio-temporal context and deep learning

Real-time tool tracking in minimally invasive-surgery (MIS) has numerous applications for computer-assisted interventions (CAIs). Visual tracking approaches are a promising solution to real-time surgical tool tracking, however, many approaches may fail to complete tracking when the tracker suffers from issues such as motion blur, adverse lighting, specular reflections, shadows, and occlusions. We propose an automatic real-time method for two-dimensional tool detection and tracking based on a spatial transformer network (STN) and spatio-temporal context (STC). Our method exploits both the ability of a convolutional neural network (CNN) with an in-house trained STN and STC to accurately locate the tool at high speed. Then we compared our method experimentally with other four general of CAIs’ visual tracking methods using eight existing online and in-house datasets, covering both in vivo abdominal, cardiac and retinal clinical cases in which different surgical instruments were employed. The experiments demonstrate that our method achieved great performance with respect to the accuracy and the speed. It can track a surgical tool without labels in real time in the most challenging of cases, with an accuracy that is equal to and sometimes surpasses most state-of-the-art tracking algorithms. Further improvements to our method will focus on conditions of occlusion and multi-instruments

Study on the characteristics of a novel wrap-around cooled diaphragm compressor for hydrogen refueling station

This study introduces a novel wrap-around cooled diaphragm compressor, designed for employment in hydrogen refilling station. The performance of this innovative compressor is evaluated using a specially developed experimental platform. The analysis focused on the impact of pressure ratio and suction gas temperature on the compressor's performance, and the cooling effect is assessed under varying temperatures of the cooling medium. The findings indicate that both the isentropic and volumetric efficiencies of the diaphragm compressor decrease with an increase in pressure ratio, with maximum values reaching 70% and 65% respectively. Under constant pressure ratio conditions, the exhaust temperature is found to increase with the rise in suction temperature. For a given suction temperature, a higher-pressure ratio resulted in a higher exhaust temperature. Furthermore, the cooling effect of the wrap-around cooling pipeline is found to be more pronounced under high pressure ratio conditions, with a maximum temperature reduction of 189.5 °C

Surgical tool tracking based on two CNNs: from coarse to fine

International audienc

Dynamics of a Turbine Blade with an Under-Platform Damper Considering the Bladed Disc’s Rotation

High-cycle fatigue (HCF) failure of the turbine blades of aero-engines caused by high vibrational stresses is one of the main causes of aero-engine incidents [...

Evaluation of Water Quality of Collected Rainwater in the Northeastern Loess Plateau

Water resources are scarce in the Northeastern Loess Plateau, and water cellar water (WCW) is a vital water resource available in the vast rural areas of the region. The quality of WCW was assessed by principal component analysis (PCA) and Nemerow’s pollution index (NPI) for different rainfall catchment areas, depths, and storage times. Eleven indicators were measured, including pH, electrical conductivity (EC), F−, Cl−, NO3−, SO42−, Na+, NH4+, Ca2+, Mg2+, and K+. The results show that the tap water quality in the rural areas of the Northeastern Loess Plateau is above the second level and meets the drinking water standard (DWS), which is similar to the tap water quality in the region. The main component score of water quality from tile roof + cement ground (I) is 0.32, and the Nemero index is 0.41; the principal component score of water quality from cement ground (I) is 0.45, and the Nemero index is 0.29; the principal component score of water quality from trampled land (I) is 0.59, and the Nemero index is 0.44; the principal component score of water quality from tile roof + trampled land (II) is 1.87, and the Nemero index is 1.10. The rainwater harvesting catchment area of tile roof + cement ground (I) ensured the highest water quality, followed by cement ground (I), trampled ground (I), and tile roof + trampled ground (II). The water quality of the catchment area for artificially collected rainwater (roof tile surface, cement ground, etc.) was better than that of the original soil (trampled ground). The highest water quality was found at a storage time of 1 year (I), followed by 2.5 years (I), and 2 months (II). A depth of 4 m (I) contributed to the highest water quality, followed by 2 m (II), 3 m (II), and 1 m (II). Water quality improved with the increasing depth of WCW. The rainfall and WCW in the area were weakly alkaline, and the groundwater was contaminated with NO3−. PCA’s water quality assessment results were similar to the NPI method, indicating that both methods can be used in combination for unconventional water quality assessment

High-elastic and strong hexamethylene diisocyanate (HDI)-based thermoplastic polyurethane foams derived by microcellular foaming with co-blowing agents

Thermoplastic polyurethane (TPU) foams have exhibited promising prospect in many industries such as automobile, sportswear and packaging, due to their outstanding mechanical properties. However, the application of TPU foams prepared by microcellular foaming with CO2 as blowing agents is still limited, due to the serious shrinkage after foaming. Herein, in this study microcellular foaming with mixed CO2 and N2 as co-blowing agents was used to control the shrinking behavior of hexamethylene diisocyanate (HDI)-based TPU foams, and further, the effects of shrinkage, expansion ratio, and cell size on the mechanical properties of TPU foams were decoupled. The results show that the stretching degree of the molecular chain and the solubility of co-blowing agents play a vital role in stabilizing TPU foams. Foams with an expansion ratio of up to 16-fold can be prepared with both pure CO2 and co-blowing agents. The shrinkage ratio of TPU foams prepared with co-blowing agents is 6.3 %, while that of foams prepared with pure CO2 is 37.8 %. Moreover, it is also found that the mechanical properties of TPU foams with a smaller shrinkage ratio are much higher than those with a larger initial expansion ratio and a similar final expansion ratio

Real-microcellular poly(ether-block-amide)/carbon fiber foams with improved mechanical property and surface quality for high-performance electromagnetic interference shielding applications

Challenges remain in large-scale and successive preparation of porous polymer composite component, which limits its practical applications for high-performance electromagnetic interference (EMI) shielding. Herein, a scalable and efficient method based on mold-opening foam injection molding was developed to fabricate carbon fiber (CF) reinforced polymer composite foams for EMI shielding applications. Thanks to the novel foaming process and heterogeneous nucleation effect of CF, real microcellular poly(ether-block-amide) (PEBA)/CF composite foams with an average cell size of 6.6 μm and a cell density of up to 109 cells/cm3 were achieved. Due to the significantly refined cellular morphology, the PEBA/CF composite foams exhibit superior EMI shielding performance over the unfoamed composites which was characterized by absorption-dominated shielding characteristics and significantly enhanced EMI shielding effectiveness. Furthermore, compared with the unfoamed case, the foamed PEBA/CF composites with refined cellular morphology shows greatly improved cold toughness and duality, and the tensile strain at break and specific tensile toughness are increased by 88.6% and 109.1%, respectively. Moreover, real-microcellular PEBA/CF composite foams have remarkably enhanced surface quality than those fabricated by regular foam injection molding process, and the surface roughness can be maximumly increased by 91.6%. Thus, this study provides a promising strategy for producing lightweight and strong components for high-performance EMI shielding applications