INFLUENCE OF SHAPE OF PRESSURE VESSEL SHELL ON BOLT WORKING LOAD AND TIGHTNESS

The area of flange joints with gasket includes many types of pressure vessels, which are mainly defined by the purpose of use and specific load conditions. These differences in definitions caused the existence of many types of pressure vessels with different shell shapes. Calculations of basic shapes are defined by standards. However, in some fields of engineering practice, these shapes are atypical. The article discusses the issue of circular sealed flange joints with a nonstandard shape of the pressure chamber shells. The aim of this article is to describe influence of shape of pressure vessel shell on bolt working load and the final tightness of the sealed joint using FEM.

Research on Novel Multi-Way Hydraulic Quick Connector for Underwater Production System

The underwater hydraulic connector is one of the most important components of an underwater oil production system. The equipment is mainly used to transport oil, chemical reagents, and other high-pressure fluids. We developed a novel underwater hydraulic multi-way quick connector system (MQCS) that is able to realize simultaneous, rapid, and precise plugging and unplugging of 10 underwater pipelines. It can be widely used for connection between subsea oil production equipment. The MQCS consists of a fixed plate assembly that is fixed to the oil production equipment and a free plate assembly that is connected to the pipelines on the drilling platform. This study describes the structure and working principle of the MQCS in detail. In addition, the process of the elastic collet clamping the mandrel was studied. Based on the finite element analysis software Abaqus, we investigated how the key geometric parameters of the elastic collet influence the axial force that needs to be provided by the underwater robot. A prototype was built based on the simulation results. To verify the performance of MQCS, a high-pressure chamber test was conducted. The results show that MQCS can accurately connect 10 high-pressure lines (about 69 MPa) in a high-pressure chamber and there is no pressure drop for 3 h after docking.

Study of metabolic disorders in rats under exposure to hypobaric hypoxia and development of ­correction approaches by simultaneous action on different elements of pathogenesis

Aim. To study the indicators of metabolic changes in the blood and brain structures of rats after exposure to hypobaric hypoxia and to determine possible pharmacological approaches to correction these changes. Methods. Hypobaric hypoxia in rats was simulated for 30 minutes in a pressure chamber, simulating an ascent to 8500 m. 3 and 24 hours after hypoxia, the activity of alanine aminotransferase, aspartic aminotransferases, alkaline phosphatase, creatine phosphokinase, lactate dehydrogenase, the content of glucose, total protein, triglycerides, cholesterol, -lipoproteins, iron and uric acid were determined in the blood serum. The level of malondialdehyde in the hippocampus and frontal cortex was examined. The studies of the effect of 2-chloroethoxy-aryl-dimethyl-aminophenylphosphorylacetohydrazide (CAPAH) (1 mg/kg) and Рiracetam (100 mg/kg) after intraperitoneal injection 40 minutes before hypoxia and 1 hour after removing the rats from the pressure chamber were carried out. Statistical analysis was carried out using the GraphPad Prism software version 8.0.1, and the Student's t-test was used to test statistical significance. Results. After 3 hours of hypobaric hypoxia, rats showed hyperenzymemia and dyslipidemia, the activity of almost all studied enzymes in the blood serum of rats was increased, the content of triglycerides was decreased, and the concentration of cholesterol was increased, the content of malondialdehyde in the hippocampus and frontal cortex was increased. In 24 hours after hypoxia, an increased level of creatine phosphokinase in the blood serum and malondialdehyde in the brain structures were noted. The use of 2-chloroethoxy-aryl-dimethyl-aminophenylphosphorylacetohydrazide prevented the development of hyperenzymemia, dyslipidemia and corrected the increased level of creatine phosphokinase after 24 hours; in both modes of administration, it reduced the serum level of malondialdehyde. Piracetam showed little effect only when administered prophylactically, preventing an increase in serum alkaline phosphatase activity and cholesterol levels. Сonclusion. The revealed efficacy of 2-chloroethoxy-aryl-dimethyl-aminophenylphosphorylacetohydrazide and its previously studied complex mechanism of action suggest that 2-chloroethoxy-aryl-dimethyl-aminophenylphosphorylacetohydrazide is a potential drug for the prevention of hypoxic disorders and acceleration of adaptation to high-altitude hypoxia.

DESIGN AND TEST OF NEGATIVE PRESSURE CHAMBER ROTARY BUCKWHEAT SEED METERING DEVICE

A negative pressure chamber rotary precision seed metering device was designed to achieve the buckwheat precision sowing goal, solving the problems of traditional negative pressure chamber poor sealing and air suction seed metering device high power consumption. The planting plate of the device was fixedly connected with the shell of the air chamber forming a negative pressure chamber, which rotates around an axis. A planting plate suitable for buckwheat seed metering was designed. Single factor test and response surface test were carried out on the seed metering device. Results showed that the buckwheat precision seed metering achieved best performance when the negative pressure, suction hole diameter and rotation speed was 2.4 kPa, 2.0 mm and 25 r/min respectively. The qualified index, multiples index and miss-seeding index were respectively 88.32%, 7.35%, and 4.33%, which met the technical requirements of buckwheat precision sowing. The results of the study provided references for the design and application of buckwheat precision seed metering device.

Shock Tube Combustion Analysis

The shock tube is a metal tube that the gas at low pressure and high pressure are separated by a diaphragm. When the diaphragm (make of material copper and aluminum) breaks on predetermined conditions (high pressure in this case) produces shock waves that move from the high-pressure chamber (known the compression chamber or Driver section) for low pressure chamber (known the expansion chamber or Driven section). The objective of this work is the correlate the ignition delay times of convectional Diesel and Biodiesel from soybean oil measured in a shock tube. The results were correlated with the cetane number of respective fuels and compared with the ignition delay times of Diesel and Biodiesel with cetane numbers of known. The ignition delay time of biodiesel from soybean oil was approximately three times greater than the ignition delay time of convectional Diesel. The contribution of this work is that it shows why pure biodiesel should not be used as substitutes for Diesel compression ignition engines without any major changes in the engines.

Design and Experimental Verification of Pressurized Cylinders in Hydraulic Rubber Hose Pressure Washers

Hydraulic rubber hoses are subject to great hydraulic impact during the actual working process, which causes a great potential safety hazard. Therefore, it is necessary to carry out pressure tests on hose assemblies to ensure its quality, so providing a high pressure for the hydraulic hose has become the key technology of this problem. Aiming at solving the problem of detection of pressure resistance in hydraulic rubber hose cleaning machines, this paper analyzed the pressurization mechanism of the hydraulic pressurized cylinder and proposed a method of continuous pressurization. This paper also theoretically analyzed the pressure expansion of the rubber hose, and the conclusion is that for the maximum hose capacity (hose size is Φ25 mm × 6 m), the volume of water required to provide water in the hose from 10 MPa to 100 MPa is 0.59 L. The pressurized cylinder was designed and checked theoretically and analyzed by the finite element method. It is concluded that the maximum stress of the pressurized cylinder is concentrated at the bottom of the high-pressure chamber, and the outlet hole at the bottom of the cylinder barrel of the high-pressure chamber is the weakest part of the pressurized cylinder. The performance of the supercharging cylinder is verified by experiments, which proves the feasibility, rapidity and stability of the supercharging cylinder.

Prospective study on the Eustachian tube function during Frenzel maneuver in a hypobaric/hyperbaric pressure chamber

Introduction The Frenzel maneuver describes a technique for middle ear equalizing which is frequently used by apnea divers. It offers advantages compared to the most commonly used techniques such as the Valsalva or Toynbee maneuver. Until now, there is insufficient literature about the pressure dynamics and Eustachian tube (ET) function during the Frenzel maneuver. The aim of the present study was to characterize the ET function during the Frenzel maneuver. Materials and methods By means of an established standardized profile of compression and decompression in a hypo/hyperbaric pressure chamber, we examined different parameters such as the ET opening pressure (ETOP), ET opening duration (ETOD), and ET opening frequency (ETOF) in 11 experienced apnea divers and compared them to the parameters during the Valsalva and Toynbee maneuver. Results Standard values for ETOP, ETOD, and ETOF could be established for the Frenzel maneuver under standardized conditions in a hypo/hyperbaric pressure chamber. Compared to the Frenzel maneuver, ETOP was higher and ETOD longer (both p < 0.001) during the Valsalva maneuver whereas ETOP was lower and ETOD shorter (both p < 0.001) during the Toynbee maneuver. No difference regarding ETOF was observed between the Frenzel, Valsalva, and Toynbee maneuver. Discussion The Frenzel maneuver was shown to be at least as effective as the Valsalva maneuver concerning ET opening. We believe that knowledge of the Frenzel technique might facilitate the pressure equalization during diving and recommend implementation of an appropriate equalization training in apnea and scuba diving education.