Optimization of pressurization process in low-pressure casting of a 5.4-ton gigantic C95800 copper alloy casting

During the low-pressure casting of extra-large size C95800 copper alloy components,traditional linear pressurization technique leads to a rapid surge of liquid metal inlet velocity at the regions where the mold cavity cross-section enlarges.This rapid increasement of liquid metal inlet velocity causes serious entrapment of gas and oxide films,and results in various casting defects such as the bifilm defects.These defects detrimentally deteriorate mechanical properties of the castings.To address this issue,an innovative nonlinear pressurization strategy timely matching to the casting structure was proposed.The pressurization rate decreases at sections where the cross-section widens,but it gradually increases as the liquid metal level rises.By this way,the inlet velocity remains below a critical threshold to prevent the entrapment of gas and oxide films.Comparative analyses involving numerical simulations and casting verification illustrate that the nonlinear pressurization technique,compared to the linear pressurization,effectively diminishes both the size and number of bifilm defects.Furthermore,the nonlinear pressurization method enhances the casting yield strength by 10%,tensile strength by 14%,and elongation by 10%.Examination through scanning electron microscopy highlights that the bifilm defects arising from the linear pressurization process result in the reduction of the castings’mechanical properties.These observations underscore the efficacy of nonlinear pressurization in enhancing the quality and reliability of gigantic castings,as exemplified by a 5.4-ton extra-large sized C95800 copper alloy propeller hub with complex structures in the current study.

Development of a 100 MPa water–gas two-phase fluid pressurization device

This paper introduces a 100 MPa water gas twophase fluid pressurization device.The device can provide 100 MPa gas pressure and 200 MPa liquid pressure for small volume(<20 mL)high-pressure experimental devices.This device can make the pressure control independent of the temperature control without changing the material components of the system.The resolution of this device in adjusting the pressure is±0.2 MPa in the process of boosting and depressurizing.This pressure boosting device generates very little vibration during work and it can be used in experiments with strict requirements on vibration.As a thermodynamic parameter,pressure has a great influence on matter.In the field of experimental geochemistry,pressure is not only an experimental method and an extreme condition but an important physical parameter independent of temperature and chemical composition.

Estimation of surface geometry on combustion characteristics of AP/HTPB propellant under rapid depressurization

The 2D sandwich model serves as a potent tool in exploring the influence of surface geometry on the combustion attributes of Ammonium perchlorate/Hydroxyl-terminated polybutadiene(AP/HTPB)propellant under rapid pressure decay.The thickness of the sandwich propellant is derived from slicing the 3D random particle packing,an approach that enables a more effective examination of the micro-flame structure.Comparative analysis of the predicted burning characteristics has been performed with experimental studies.The findings demonstrate a reasonable agreement,thereby validating the precision and soundness of the model.Based on the typical rapid depressurization environment of solid rocket motor(initial combustion pressure is 3 MPa and the maximum depressurization rate is 1000 MPa/s).A-type(a flatter surface),B-type(AP recesses from the combustion surface),and C-type(AP protrudes from the combustion surface)propellant combustion processes are numerically simulated.Upon comparison of the evolution of gas-phase flame between 0.1 and 1 ms,it is discerned that the flame strength and form created by the three sandwich models differ significantly at the beginning stage of depressurization,with the flame structures gradually becoming harmonized over time.Conclusions are drawn by comparison extinction times:the surface geometry plays a pivotal role in the combustion process,with AP protrusion favoring combustion the most.

Theoretical study on the pressurization characteristics of disc-seal single screw pump used in high viscosity oily sludge conveying field

The disc-seal single screw pump(DSSP)used in the field of high viscosity oily sludge transport has a huge advantage.However,there is no research on the pressurization characteristics of the DSSP at present,which makes its application limited.In view of this,the pressurization process mathematical model of the DSSP was established based on the geometric model of the pump.By using this model,the pressurization characteristics of DSSP and the influence of working parameters on the pressurization process were studied combined with the principle of back-flow pressurization.Analysis results show that the instantaneous pressurization process could be realized mainly depending on the reflux pressurization from the outlet chamber to the pressurization chamber when the screw rotor rotating angle is located at-5°to+5°.The pressure in the pressurization chamber will increase with the increase of working parameters which include inlet pressure,outlet pressure,screw rotation velocity and dynamic viscosity of fluid medium in the area of flow-back pressurization.The screw rotation velocity and the viscosity of the conveying medium have significant effects on the peak pressure in the pressurization chamber,and the peak pressure in the pressurization chamber is proportional to the screw rotation velocity and the dynamic viscosity coefficient of the conveying medium.The proportional coefficient between the peak pressure and the screw rotation velocity is 6.29×10~4.The proportional coefficient between the peak pressure and the dynamic viscosity of the conveying medium is 6.28×10~6.

Density and Mechanical Properties of Aluminum Lost Foam Casting by Pressurization during Solidification

Porosity is thought to be severe in aluminum alloy castings produced by lost foam process due to the pyrolysis of the polystyrene foam pattern during pouring, which results in detrimental effect in mechanical property. The slow solidification rate promotes the formation of gassing pin holes, and relative weakness of the thermal gradients can cause micro-shrinkage if the outline of the part complicates feeding in the lost foam casting. One of the methods to eliminate the porosity is to apply high pressure to the molten metal like an isostatic forging during solidification. Fundamental experiments were carried out to evaluate the effect of the external pressure on the porosity and mechanical properties of A356.2 alloy bar in the lost foam casting. Solidification time and porosity decreased with increasing the applied pressure during solidification. Applying external pressure was effective in decreasing the porosity and increasing the elongation of the lost foam casting.

Simulation of landslide run-out by considering frictional heating and thermal pressurization

Some of the remarkable characteristics of natural landslides, such as surprisingly long travel distances and high velocities, have been attributed to the mechanisms of frictional heating and thermal pressurization. In this work, this mechanism is combined with a depth-averaged model to simulate the long runout of landslides in the condition of deformation. Some important factors that influence frictional heating and thermal pressurization within the shear zone are further considered, including velocity profile and pressurization coefficient. In order to solve the coupled equations, a combined computational method based on the finite volume method and quadratic upwind interpolation for convective kinematics scheme is proposed. Several numerical tests are performed to demonstrate the feasibility of the computational scheme, the influence of thermal pressurization on landslide run-out, and the potential of the model to simulate an actual landslide.

Pressurization control system for low pressure crucible casting

A new compact pressurization control system of the low pressure casting machine for crucible pressure casting has been developed. It is especially designed for the production of high-quality aluminum or magnesium alloy parts with low input cost. This machine with such a system has the virtue of economical and compact, and combines the Fuzzy-PID technology and achieves accuracies of ±2.5 mbar. At present, this machine has been adopted by several users in China for the production of aluminum alloy castings with high property requirements. Furthermore, for magnesium alloy castings, this machine can be used with the gas protect unit.

Determination of Thermodynamic Parameters of Some Fluorochlorohydrocarbons in Acetone by Gas Chromatography at Low Temperature and Pressurization

1 INTRODUCTIONGas chromatography(GC)has been proved to perform satisfactorily in vapor-liquid equilib-rium measurements and in the study of solution theory.Infinite dilution data are useful notonly for design calculations but also for theoretical development of correlations.Studies inthis field have been carried on at the Zhejiang University.

A new numerical model of ring shear tester for shear band soil considering friction-induced thermal pressurization

In this study,a new numerical model of ring shear tester for shear band soil of landslide was established.The special feature of this model is that it considers the mechanism of friction-induced thermal pressurization,which is potentially an important cause of high-speed catastrophic landslides.The key to the construction of this numerical ring shear model is to realize the THM(thermo-hydro-mechanical)dynamic coupling of soil particles,which includes the processes of frictional heating,thermal pressurization,and strength softening during shearing of solid particles.All of these are completed by using discrete element method.Based on this new model,the characteristics of shear stress change with shear displacement,as well as the variation of temperature and pore pressure in the specimen,are studied at shear rates of 0.055 m/s,0.06 m/s,0.109 m/s and 1.09 m/s,respectively.The results show that the peak strength and residual strength of specimen are significantly reduced when the mechanism of frictioninduced thermal pressurization is considered.The greater the shear rate is,the higher the temperature as well as the pore pressure is.The effect of shear rate on the shear strength is bidirectional.The simulation results demonstrate that this model can effectively simulate the mechanism of friction-induced thermal pressurization of shear band soil during ring shear process,and the shear strength softening in the process.The new numerical ring shear model established in this study is of great significance for studying the dynamic mechanism of high-speed catastrophic landslides.

Development of the Separate Air-Supply Type of Pressurization Smoke Control System for the Stairwells of High-Rise Buildings in Korea

The pressurization smoke control system has been commonly used as a smoke control system at the emergency stairs of high-rise buildings. However, a higher possibility of overpressure between the lobby and the accommodation or pressure drop in the lobby could lead to failure in achievement of the purpose of pressurization system, particularly when supplying the leakage and supplementary air flow through one air-supply path at a time. To improve this particular issue, the devise configurations, as well as the different ways to supply the leakage and supplementary air flow through the different flow passages have been proposed. The performance of the trial product was evaluated on the test bed, ultimately providing a safe evacuation environment if high-rise buildings fired.

Performance of a Score-Stove with a Kerosene Burner and the Effect of Pressurization of the Working Fluid

Score-StoveTM a clean-burning cooking stove that also generates electricity was tested using a pressurized kerosene burner. The Score-Stove works on the principle of thermo-acoustics to gen- erate small-scale electricity. The device having hot-end, cold-end and regenerator acts in a way similar to a stirling cycle generating acoustic power, which is then converted to electricity using a linear actuator. It can supply small power for applications such as LED lighting, mobile phone charging and radios particularly in rural areas without grid electricity as well as improving house- hold air pollution. After assessing the needs of the rural communities through a survey, tea-stalls and small restaurants owners were identified as clients with the most potential of using the stove in Bangladesh. Bangladesh University of Engineering and Technology ((BUET) modified a Score- Stove to use both wood and a pressurized kerosene burner of a design that is widely used for cooking in rural areas of Bangladesh. The design was adapted to meet performance needs such as: heating rate, cooking efficiency, energy distribution, electric power generation, exhaust emissions and time taken to boil water using standardized water boiling tests. Performance was also compared with conventional (non-electrically generating) stoves that use a pressurized kerosene burn- er. The Score-Stove performance was then evaluated while increasing the pressure of the sealed working fluid (air in this case) from atmospheric to about 1.4 bar. The pressurization was found to almost double the power generation. An arrangement for utilizing cooling water waste heat was also devised in order to improve the thermal performance of the stove by 18%. Technical deficiencies are documented and recommendations for improvements and future research in order to obtain wider end-user acceptance are made.

The Reliable and Intelligent Propulsion Pressurization System of the Long March 7 Launch Vehicle

The reliable and intelligent propulsion pressurization system is one of the key technologies of new Chinese generation launch vehicles; a high reliability design is an important guarantee for the success of launching. This paper analyzes the domestic and overseas liquid launch vehicles in the area of propulsion pressurization systems, based on comprehensive analysis, demonstrating the reliable and intelligent propulsion pressurization system of the Long March 7(Simplified as LM-7) has been raised. By applying a full chain redundancy design, setting proper pressure control bandwidth and control mode reconstruction under extreme fault conditions, the reliability and adaptability of the propulsion pressurization system has enhanced significantly. In addition, the complete system has been verified by the first two flights of LM-7.

First Systematic Testing Platform for Pressurization Feed System Developed for Liquid Rocket Propellant in China

Beijing Aerospace System Engineering Institute of China Academy of Launch Vehicle Technology (CALT) declared recently that theinstitute has set up a laboratory whichwould operate a newly

The New Pressurization System for the Upper Stage

The paper describes the new pressurization system for the upper stage of launch vehicles and spacecraft and the flight test results of the vehicle which conform to the design of the system.

Prediction Model of Coal Reservoir Pressure and its Implication for the Law of Coal Reservoir Depressurization

The main methods of coalbed methane(CBM)development are drainage and depressurization,and a precise prediction of coal reservoir pressure is thus crucial for the evaluation of reservoir potentials and the formulation of reasonable development plans.This work established a new reservoir pressure prediction model based on the material balance equation(MBE)of coal reservoir,which considers the self-regulating effects of coal reservoirs and the dynamic change of equivalent drainage area(EDA).According to the proposed model,the reservoir pressure can be predicted based on reservoir condition data and the actual production data of a single well.Compared with traditional reservoir pressure prediction models which regard EDA as a fixed value,the proposed model can better predict the average pressure of reservoirs.Moreover,orthogonal experiments were designed to evaluate the sensitivity of reservoir parameters on the reservoir pressure prediction results of this proposed model.The results show that the saturation of irreducible water is the most sensitive parameter,followed by Langmuir volume and reservoir porosity,and Langmuir pressure is the least sensitive parameter.In addition,the pressure drop of reservoirs is negatively correlated with the saturation of irreducible water and the Langmuir volume,while it is positively correlated with porosity.This work analyzed the reservoir pressure drop characteristics of the CBM wells in the Shizhuangnan Block of the Qinshui Basin,and the results show that the CBM reservoir depressurization can be divided into three types,i.e.,rapidly drop type,medium-term stability type,and slowly drop type.The drainage features of wells were reasonably interpreted based on the comprehensive analysis of the reservoir depressurization type;the latter was coupled to the corresponding permeability dynamic change characteristics,eventually proving the applicability of the proposed model.

Pressurization System in Low Pressure Tube Hydroforming

Advanced high strength steels are the group of material with high strength and good formability, because high strength lesser gauge thickness can be used without compromising the function of component. In terms of economic forming process, hydroforming is the manufacturing option which uses a fluid medium to form a component by using high internal pressure. This process gained steep interest in the automotive and aerospace industries because of its many advantages such as part consolidation, good quality of the formed part etc. The main advantage is that the uniform pressure can be transferred to whole projected part at the same time. Low pressure tube hydroforming considered an inexpensive option for forming these advanced high strength steel. This paper investigates the pressurization system used during the low pressure tube hydroforming cycle. It is observed that the usage of ramp pressure cycle during forming the part from low pressure tube hydroforming results in lesser die holding force. Also, the stress, strain and thickness distribution of the part during low pressure tube hydroforming are critically analysed.

Study on an novel composite gel material solving serious lost circulations and pressurization sealing

Lost circulations have presented great challenges to the petroleum industry, causing great expenditures of cash and time to fighting the problem. Probably the most problematic situations are the naturally fractured formations where the operator may face total loss with no mud return in the annular. The voids or large fracture encountered in this case are often far too large to be plugged with conventional Lost Circulation Material. This paper will give a detailed introduction on a novel composite gel material usable to control severe losses and pressurization sealing. The plugging mechanics of this new composite gel material, which is different from conventional lost circulation materials, were elaborated as well. In addition, the properties of the new composite gel material such as thermostability, sealing strength and bearing resistance are characterized with specific experimental devices. The experimental results proved that the breakdown pressure of the new plugging reached more than 20MPa, and the maximum degraded temperature can be exceed 130℃. The field application at 4 wells in Puguang gas field, SINOPEC, demonstrated that the new composite gel material solved the serious loss in Ordovician carbonate fractured formation successfully and guaranteed the following completion cement operation smoothly. The composite gel sealing slurries, which was easily prepared on site, gives remarkable properties regarding pumping through drill pipes, adjustment of setting time and excellent sealing strength of the lost zone sealing, additionally, the whole pressurization sealing process was complicated within only ten hours. The on-site results show that the plugging ratio of the new composite gel was reached 100%, and the success rate of sealing operation kept above 80%.Thus the new LCM can guarantee safe drilling jobs and save operation cost more effectively.

Changes in Texture, Structure and Pectin of Peach during Pressurization, Heating or Processing of High-pressure-induced and Heat-induced Jam

The objectives of this study are to research the relationship between pectin and the softening of peach by soaking in citric acid solutions for 24 h at 35 ℃, pressurizing for 30 rain at 500 MPa or heating for 10 min. Also, comparing high-pressure-induced jam （HP-jam） and heat-induced jam （H-jam） were evaluated. It was found that firmness of the peach decreased greatly when soaked at pH 2.0 〉 heated 〉 soaked at pH 2.2 or 2.5 〉 pressurized, respectively. About 88% of the peach pectin was water-soluble-pectin and high-methoxyl pectin, while low-methoxyl pectin was slight. During pressurization, the pectin did not change. However, pectin degraded through hydrolysis during heating; consequently, the middle lamella separated. Also, eight kinds of peach jam （65% sugar, pH 2.0 or pH 2.2, and 50% or 60% sugar, pH 2.5） were compared. Both color and flavor of HP-jam were better than H-jam. As the pH values were lower, L-, a-, b-values of jam became higher, and the jam became pinker. Raw peach contained about 0.3%-0.4% pectin, therefore, an addition of 0.6% pectin was needed for both HP- and H-jams. However, there was no great difference in rheology or sensory evaluation between HP- and H-jams.

Study on the Influence of Radial Pressurization on Anchoring Performance of Bolts

Supporting soft rock roadways in coal mines has long posed a formidable challenge. Addressing issues such as the formation of soft rock strata, poor fracture development, limited tolerance, and the frequent and severe damage sustained by conventional bolts due to their low elongation and bearing capacity, this study employs bottom expansion and filling technology. It combines theoretical analysis with booster bolt pull-out tests to scrutinize the radial stress distribution of bolts under extrusion forces. Moreover, it conducts a comparative analysis of bolt bearing characteristics under varying radial pressurization conditions, delving into the impact of radial directional increases in compressive stress on bolt anchoring performance.

Theoretical and experimental studies of gas preparation system for pressurization and reactive control system of launch vehicle

A new gas preparation system(GasPS-RCS)is proposed to solve two tasks:(A)to heat helium gas for tank pressurization;(B)to prepare gas for the Launch Vehicle(LV)Reactive Control System(RCS)at the LV orientation and stabilization sections of the LV on passive parts of the flight trajectory,to provide conditions for launching the Liquid Rocket Engine(LRE).The system includes a gas generator based on hydrogen peroxide,a separator for water separation,heat exchangers independent of the LRE,and gas-jet nozzles.The proposed new system allowed to reduce the length of pressurizing gas lines and reduce the increased helium gas consumption during the heat exchanger warm-up interval of the LRE during its launch.A special advantage of the proposed system is the possibility of ground testing of heat exchangers without an operating LRE.A mathematical model based on the first law of thermodynamics was used to perform a comparative analysis of GasPS-RCS with traditional pressurization and RCS systems.To validate the mathematical model,the experimental studies of helium pressurizing of a liquid nitrogen tank were conducted.The results show that the deviation of experimental and calculated values for pressure is 1.1%and for temperature up to 2%.According to the results of comparative analysis,the GasPS-RCS is 259 kg lighter for the first stage and 80 kg lighter for the second stage of the LV.