Natural Gas Cylinders Research Articles

Service Composition and Optimal Selection of Low-Carbon Cloud Manufacturing Based on NSGA-II-SA Algorithm

As a new model of networked manufacturing services, cloud manufacturing (CMfg) aims to allocate enterprise manufacturing resources, realize rational utilization of manufacturing resources, and adapt to increasingly complex user needs. However, previous studies on service composition and optimal selection (SCOS) in CMfg environments do not incorporate carbon emissions into the quality of service (QoS) evaluation indicators. Therefore, a SCOS model for CMfg under a low-carbon environment is firstly proposed in this paper. Secondly, based on the Non-dominated Sorting Genetic Algorithm (NSGA-II) algorithm, a hybrid multi-objective evolutionary algorithm, named the NSGA-II-SA algorithm, is proposed to solve the model and obtain the Pareto optimal solution set. Then, an algorithm result optimization strategy combining subjective and objective is proposed to filter the Pareto optimal solution set, so as to make the final decision. Finally, taking natural gas cylinder head production as an example, the proposed algorithm is compared with other algorithms, and the results show that the proposed algorithm can obtain more non-dominated solutions, and the quality of the solutions in the four dimensions is better than the other. Therefore, it is proved that the proposed algorithm has better comprehensive performance in SCOS under a low-carbon environment.

Fuzzy estimation for transient distribution of internal thermal excitation in composite overwrapped pressure vessel

• Set up a decentralized fuzzy inference for estimation of internal thermal excitation. • The inversion method possesses a good anti-ill-posedness character. • The transient temperature of gas cylinder is reconstructed by infrared thermography. • The infrared thermography of gas cylinder is collected at the actual inspection site. The representative composite overwrapped pressure vessel of vehicle-mounted composite compressed natural gas cylinder is taken as the research object. Based on the principle of double decentralized fuzzy inference with a temporal-spatial decoupling characteristic, an inversion scheme is established by which the infrared thermography of cylinder is employed to estimate the transient distribution of internal thermal excitation. In this scheme, the error vector of time series of the finite temperature measurement points on the surface of cylinder is processed by fuzzy inference, and then the transient distribution of internal thermal excitation is estimated. The influence of the number of measurement points and measurement errors on the inversion results is studied through numerical simulation. Furthermore, combined with the on-site gas cylinder inspection process, the internal thermal excitation of cylinder is estimated using the infrared thermography of cylinder under the steam flushing process obtained from the inspection site. According to the inversion results, the transient temperature field of cylinder is reconstructed, and the reliability of reconstruction results is also verified. The results show that under the experimental conditions in this paper, the maximum deviation of the surface temperature reconstruction results of cylinder is about 1.0 °C.

Deriving Major Fire Risk Evaluation Items Utilizing Spatial Information Convergence Technology in Dense Areas of Small Obsolete Buildings

As small obsolete buildings are exposed to high fire risks, governments are trying to evaluate their fire risks and preferentially improve fire protection performance for high risk buildings, however, the evaluation manpower and time are insufficient compared to the rapidly increasing number of obsolete buildings. Therefore, this study aimed to derive major fire risk index (FRI) evaluation items as part of developing a platform to quickly and efficiently evaluate fire risks in dense areas of small obsolete buildings utilizing spatial information convergence technology. To this end, 20 preliminary evaluation items specifically tailored to dense areas of small obsolete buildings were derived through a field survey, investigation of FRI evaluation items from existing works, and expert pre-reviews. Based on the derived 20 preliminary items, an importance survey was conducted with a total of 181 fire safety experts including fire officers, university professors, researchers, industry experts, and fire insurers. As a result, a total of 12 major evaluation items (e.g., outdoor fire extinguisher, distance to 119 Safety Center, building structure, building cladding, illegal alterations, illegal parking, and liquefied natural gas cylinder) were derived. Results can help to evaluate the fast and efficient fire risks in dense areas of small obsolete buildings.

Design, Fabrication and Validation of a Laboratory Flow Loop for Hydrate Studies

The peculiar nature of the offshore environment has necessitated the need for the Oil and Gas industry to develop durable subsea technologies and better hydrate inhibitors to prevent hydrate formation and assure flow. This paper discusses the design, fabrication and validation of a laboratory flow loop for hydrate studies. The laboratory loop is a closed loop of 12meters, fabricated using 0.5inch 316 stainless steel pipe enclosed in an insulated 4inch Polyvinylchloride (PVC) pipe. The skid mounted loop was fitted with pumps, temperature gauges, pressure gauges, differential pressure transmitters, a gas mixing vessel, an inhibitor mixing vessel, and a Natural Gas cylinder. Hydrate formed in the loop when natural gas was contacted with water under suitable hydrate forming temperature and pressure conditions and was indicated by an increased loop temperature, an increased differential pressure and a decreased loop pressure. Loop Validation was done by flowing a single phase fluid of water, a single phase fluid of gas and a 2 phase fluid of gas and water in three different experimental runs respectively. Each experimental run lasted 2 hours during which temperatures and pressures around the loop were recorded every minute. Hydrate formation was observed in the experimental run conducted with the two phase fluid (gas and water) and the experimental run conducted with gas alone due to water condensing out of gas during cooling. Hydrate did not form in the experimental run conducted with single phase fluid of water. The laboratory flow loop adequately predicts hydrate formation and has been used in screening and selection of Kinetic Hydrate Inhibitors (KHI).

Heat and Mechanical Response Analysis of Composite Compressed Natural Gas Cylinders at Vehicle Fire Scenario

With the worldwide popularization of compressed natural gas (CNG) vehicles, the use of composite cylinders has been growing at a high rate. Due to the flammable composite layers, safety performance of composite CNG cylinders under localized fire exposure caused by accidental vehicle fires has drawn extensive attention. Composite CNG cylinders would be degraded by the fire and even burst before the activation of pressure relief device. In this paper, a comprehensive model is developed for predicting heat and mechanical response of the cylinder subjected to localized fire. Firstly, a three-dimensional computational fluid dynamics (CFD) sub-model is developed for simulating localized fire impingement on the cylinder to obtain heat response data. Secondly, thermophysical and mechanical property degradation of cylinder's aluminum liner and carbon fiber/epoxy composite layers caused by fire is described in detail. Thirdly, a non-linear finite element analysis (FEA) sub-model is developed for predicting mechanical response of the cylinder exposed to fire. Heat response data coupling transfer between CFD sub-model and FEA sub-model is realized to accurately transfer thermo-mechanical boundary condition. Finally, heat and mechanical response of the cylinder subjected to localized fire is studied based on the modeling of a typical composite CNG cylinder. Pressure and temperature of internal CNG slowly rise, and temperature distribution of internal CNG and cylinder's outside surface is uneven during the localized fire. Stress distribution of the cylinder wall is also uneven, and maximum stress is located at the cylindrical shell near the rear head exposed to fire.

On the Microstructural Evolution of 4130 Steel During Hot Compression

This article first gives a brief patent review of recent trends of steel alloys used in the manufacturing of highpressure gas containers. 4130 steel is among such alloys and has been extensively used in natural gas cylinders that are manufactured through the hot deformation processes. Due to the importance of process parameters such as temperature and strain rate on the ensuing microstructure, primarily grain size, and mechanical properties of the cylinder, the dynamic recrystallization characteristics of 4130 steel are investigated in the second part of this article. Hot compression tests on 4130 steel specimens have been performed at a temperature range of 900-1100°C, strain rate range of 0.001-0.1s-¹ and the strain of 0.9. The resulting flow stress curves show the occurrence of dynamic recrystallization with single or multiple peaks, before reaching the steady state flow at different temperatures and strain rates. The effect of various processing parameters on the microstructure of the alloy is identified by microstructural examination focusing on revealing primary austenite grains using special etchant solutions. It is found that the average grains size of the deformed 4130 steel increases with an increase of the forming temperature and a decrease in the strain rate. The grain size is decreased with an increase of the steady state stress. Keywords: Austenite grain size, dynamic recrystallization, flow stress, hot compression, microstructure evolution, Zenner-Hollomon parameter, 4130 steel, CNG Cylinders, Hot Deformation, Steel Alloys

Failure Analysis of High Density Polyethylene Butt Weld Joint

This article discusses a detailed failure analysis conducted on high density polyethylene which acts as the liner of composite compresses natural gas cylinder. Leakage from the cylinder was observed after about 2000 cycles of hydrostatic pressure testing at 250 bars. Visual inspection revealed that the leakage occurred from the circumferential fusion joint between the cylinder and dome section. The cylinder and dome sections were produced from different techniques and joined together by using a heated tool butt welding process conducted by a local manufacturer. The joined components work as an integral part. The investigation was carried out using various techniques including mechanical, thermal and metallurgical examination. Fractography of the failed joint surface showed stepwise marks typical of a fatigue failure. Mechanical testing results showed that the strength of dome section was significantly lower than that of the cylinder section. Moreover, both the tensile and fatigue strength of joint was also almost half that of the cylinder. The fracture surface of the broken welded joint showed brittle failure. The melting points of both the cylinder and the dome sections were found almost same by differential scanning calorimeter but large difference was found between the melt point indexes of both sections. The results suggested that the failure was actually a stress cracking via a process of slow crack growth, which occurred due to use of a dome material having inferior properties and very high melt flow index. These properties inhibited proper fusion and resulted in a poor weld joint. Consequently, the weld joint of lower strength eventually failed in macroscopically brittle manner upon cyclic loading.

Hot Deformation Characteristics of 34CrMo4 Steel

Abstract The 34CrMo4 (AISI 4130) steel is extensively utilized in the compressed natural gas cylinders. Due to the importance of thermomechanical processing in the production of these cylinders, the dynamic recrystallization (DRX) characteristics of 34CrMo4 steel were investigated. The effect of hot deformation parameters such as temperature and strain rate on the dynamic restoration processes of a 34CrMo4 alloy was studied. Hot compression tests were performed in the temperature range of 900 to 1100 °C and the strain rate range of 0.001 to 0.1 s −1. Hot workability of this alloy has been analyzed by employing flow localization parameter. The flow curves observed are typical of occurrence of dynamic recrystallization and have exhibited single or multiple peaks in flow stress curve before reaching steady state, depending on the temperature and strain rates. The flow stress decreases with the increase of deformation temperature and the decrease of strain rate. Finally the activation energy obtained in this research is 490.749 kJ/mol.

CNG cylinder manufacturers test basalt fibre

Basalt fibre offers an alternative to carbon and glass in the filament winding of compressed natural gas cylinders. Dmitri Pavlovski, Boris Mislavsky and Andrey Antonov of Russian company Kamenny Vek report on some promising studies.