Simulation on flow, heat transfer and stress characteristics of large-diameter thick-walled gas cylinders in quenching process under different water spray volumes

Cooling strength is one of the important factors affecting microstructure and properties of gas cylinders during quenching process,and reasonable water spray volume can effectively improve the quality of gas cylinders and reduce production costs.To find the optimal water spray parameters,a fluid-solid coupling model with three-phase flow was established in consideration of water-vapor conversion.The inner and outer walls of gas cylinder with the dimensions of d914 mm×38 mm×12000 mm were quenched using multi-nozzle water spray system.The internal pressure,average heat transfer coefficient(have)and stress of the gas cylinder under different water spray volumes during quenching process were studied.Finally,the mathematical model was experimentally verified.The results show that both the internal pressure and have increase along with the increase of spray volume.The internal pressure increases slowly first and then rapidly,but have increases rapidly first and then slowly.To satisfy hardenability of gas cylinders,the minimum spray volume should not be less than 40 m^3/(h·m).The results of stress indicate that water spray quenching will not cause deformation of bottle body in the range of water volume from 40 to 290 m^3/(h·m).

AN ADVANCED TECHNOLOGY OF DRAWING IN GAS-STORAGE CYLINDER MAKING

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Heavy Duty Natural Gas Single Cylinder Research Engine Installation, Commissioning, and Baseline Testing

Natural Gas (NG) Internal Combustion Engines (ICE) are a promising alternative to diesel engines for on-road heavy-duty applications to reduce greenhouse gas and harmful pollutant emissions. NG engines have not been widely adopted due to the lower thermal efficiency compared with diesel engine counterparts. To develop the base knowledge required to reach the desired efficiency, a Single Cylinder Engine (SCE) is the most effective platform to acquire reliable and repeatable data. A SCE test cell was developed using a Cummins 15-liter six-cylinder heavy-duty engine block modified to fire one cylinder (2.5-liter displacement). A Woodward Large Engine Control Module (LECM) is integrated to permit implementation of real-time advanced combustion control. Intake and exhaust characteristics, fuel composition, and exhaust gas recirculated substitution rate (EGR) are fully adjustable. A high-speed data acquisition system acquires in-cylinder, intake, and exhaust pressure for combustion analysis. The baseline testing shows reliable and consistent results for engine thermal efficiency, indicated mean effective pressure (IMEP), and coefficient of variance of the IMEP over a wide range of operating conditions while achieving effective control of all engine control and operation variables. This test cell will be used to conduct a research program to develop new and innovative control algorithms and CFD optimized combustion chamber designs, allowing ultra-high efficiency and low emissions for NG ICE heavy-duty on-road applications.

A numerical study on dispersion of particles from the surface of a circular cylinder placed in a gas flow using discrete vortex method

The dispersion of particles emitted from the surface of a circular cylinder placed in a gas flow at the Reynolds number of 200 000 is numerically investigated using the discrete vortex method coupled with a Lagrangian approach for solid particle tracking. The wake vortex patterns, the temporal-spatial distributions and trajectories as well as the dispersion functions for particles with various Stokes numbers（St） ranging from 0.001 to 1.0 are obtained. The numerical results reveal that：（1） Solid particles on the cylinder surface are picked up and then transported away from the cylinder by the wake vortex flow.（2） Solid particles emitted from the cylinder surface always follow the vortices in the cylinder wake, and the response of particles to wake vortices is directly related to their Stokes numbers（particles with St= 0.001, 0.0038, 0.01 can distribute both in the vortex core and around the vortex periphery, whereas those with St= 0.1, 1.0 can not enter the vortex core and congregate mainly around the vortex periphery）.（3） The particles move in rolling state in the wake region, and the dispersion intensity of particles in the lateral direction decreases remarkably as the Stokes number of particles is increased from 0.001 to 1.0.

Fatigue Analysis of Liquefied Petroleum Gas Cylinders for Safety Risk Assessment

With the widespread application of liquefied petroleum gas (LPG),the safety of LPG cylinder has received more and more attention.For the safety of LPG cylinder,we conduct a safety risk assessment of cylinder using the failure mode and effect analysis (FMEA) method.Taking the most influential inflatable fatigue under normal conditions as the research object,we use FE-safe software to analyze the fatigue failure.The risk compliance coefficients of various failure modes are calculated and classified according to the risk level.In this way,the service life of the LPG cylinder weld is determined.The presented method improves the safety risk assessment process of LPG cylinder and provides a good theoretical and practical basis for similar pressure vessel risk assessment.

Rotational Flow in a Narrow Annular Gap Based on Lattice Boltzmann Method

For comprehensive characteristics of flow in a gas bearing,lattice Boltzmann method(LBM)is applied for study of the two-dimensional flow between two eccentric cylinders with the inner one rotating at a high speed.The flow pattern and circumferential pressure distribution are discussed based on critical issues such as eccentricity ranging from 0.2 to 0.9,clearance ratio varying from 0.005 to 0.01 and rotating speed in the range of 3×104—1.8×105 r/min.The analysis and discussion on the circumferential pressure distribution affirmed the quasilinear relation between the extremum pressure and rotating speed.Furthermore,a high eccentricity and small clearance ratio contributes most to the fluctuation of the circumferential pressure distribution.The flow pattern inside the channel exhibits separation vortex under a large eccentricity.The conclusions drawn in this work give rise to prediction of the flow pattern in the gas bearing which is beneficial for evaluating the performance of as well as instructing the design and development.

Performance,combustion,and emission characteristics of on a diesel engine fuelled with hydrogen compressed natural gas and Kusum seed biodiesel

Renewable fuels have many advantages over fossil fuels because they are biodegradable and sustainable,and help mitigate social and environmental problems.The objective of the present study is to evaluate the performance,combustion,and emission characteristics of a compression–ignition engine using hydrogen compressed natural gas(HCNG)-enriched Kusum seed biodiesel blend(KSOBD20).The flow rate of HCNG was set at 5 L/min,10 L/min,and 15 L/min,and the injection pressure was varied in the range of 180 bar to 240 bar.Brake thermal efficiency(BTE)and brake-specific fuel consumption(BSFC)were improved when HCNG was added to the KSOBD20.Combustion characteristics,namely,cylinder pressure(CP)and net heat release rate(NHRR),were also improved.Emissions of carbon monoxide(CO),hydrocarbons(HC),and smoke were also reduced,with the exception of nitrogen oxides(NO_(x)).The higher injection pressure(240 bar)had a positive effect on the operating characteristics.At an injection pressure of 240 bar,for KSOB20+15 L/min HCNG,the highest BTE and the lowest BSFC were found to be 32.09%and 0.227 kg/kWh,respectively.Also,the CP and NHRR were 69.34 bar and 66.04 J/°.CO,HC,and smoke levels were finally reduced to 0.013%,47×10^(-6)and 9%,respectively,with NO_(x)levels at 1623×10^(-6).For optimum results in terms of engine characteristics,the fuel combination KSOBD20+15 L/min HCNG at FIP 240 bar is recommended.

Particle acceleration by stimulated emission of radiation in cylindrical waveguide

In particle acceleration by stimulated emission of radiation（PASER）, efficient interaction occurs when a train of micro-bunches has periodicity identical to the resonance frequency of the medium. Previous theoretical calculations based on the simplified model have only considered the energy exchange in the boundless condition.Under experimental conditions, however, the gas active medium must be guided by the metal waveguide. In this paper, we have developed a model of the energy exchange between a train of micro-bunches and a gas mixture active medium in a waveguide boundary for the first time, based on the theory of electromagnetic fields, and made detailed analysis and calculations with Math CAD. The results show that energy density can be optimized to a certain value to get the maximum energy exchange.