Thermodynamic Analysis of CNG Fast Filling Process of Composite Cylinder Type IV

Due to ecological and economic advantages, natural gas is used as an alternative fuel in the transportation sector in the form of compressed natural gas (CNG) and liquefied natural gas (LNG). Development of infrastructure is necessary to popularize vehicles that use alternative fuels. Selected positive factors from EU countries supporting the development of the CNG market were discussed. The process of natural gas vehicle (NGV) fast filling is related to thermodynamic phenomena occurring in a tank. In this study, the first law of thermodynamics and continuity equations were applied to develop a theoretical model to investigate the effects of natural gas composition on the filling process and the final in-cylinder conditions of NGV on-board composite cylinder (type IV). Peng–Robinson equation of state (P-R EOS) was applied, and a lightweight composite tank (type IV) was considered as an adiabatic system. The authors have devised a model to determine the influence of natural gas composition on the selected thermodynamic parameters during fast filling: Joule–Thomson (J-T) coefficient, in-cylinder gas temperature, mass flow rate profiles, in-cylinder mass increase, natural gas density change, ambient temperature on the final natural gas temperature, influence of an ambient temperature on the amount of refueled natural gas mass. Results emphasize the importance of natural gas composition as an important parameter for the filling process of the NGV on-board composite tank (type IV).

Effects of salinity on growth performance, survival rate, digestive enzyme activities and physiological parameters of striped catfish (Pangasianodon hypophthalmus) at larval stage

The present study was to investigate the effects of different salinities (0 (control), 3, 6, 9, 12, 15‰) in striped catfish (Pangasianodon hypophthalmus) at larvae stage. Four-hundred individuals were randomly distributed to each 500-L composite tank (containing 250-L water) in triplicates. After 60 days, fish was sampled to determine survival rate, growth performance, hematological parameters, stress response indicators, and enzymatic activities. The results showed that the survival rate was highest in 6‰ (60.9%) and lowest in 15‰ (1.25%) (p<0.05). Fish exposed to salinities from 0 to 9‰ showed an increasing trend in growth. The osmolality of fish reared in 9 and 12‰ was significantly higher than that in the lower salinities (p<0.05). Similarly, concentrations of Na+, K+, and Cl- increased remarkably at high salinities. Chymotrypsin and trypsin activities were reduced by increased salinities (p<0.05), which were lowest at 15‰ (69.2±2.46 U/min/mg protein and 1.46±0.01 mU/min/mg protein, respectively). Stress indicators such as glucose and cortisol concentrations were not significantly depended on the salinity in the range of 0 to 12‰. Striped catfish larvae showed an adaptable response to high salinity and the appropriate salinity range for larvae rearing was below 6‰.

An Optimum Fatigue Design of Polymer Composite Compressed Natural Gas Tank Using Hybrid Finite Element-Response Surface Methods

The main purpose of this research is to design a high-fatigue performance hoop wrapped compressed natural gas (CNG) composite cylinder. To this end, an optimization algorithm was presented as a combination of finite element simulation (FES) and response surface analysis (RSA). The geometrical model was prepared as a variable wall-thickness following the experimental measurements. Next, transient dynamic analysis was performed subjected to the refueling process, including the minimum and maximum internal pressures of 20 and 200 bar, respectively. The time histories of stress tensor components were extracted in the critical region. Furthermore, RSA was utilized to investigate the interaction effects of various polymer composite shell manufacturing process parameters (thickness and fiber angle) on the fatigue life of polymer composite CNG pressure tank (type-4). In the optimization procedure, four parameters including wall-thickness of the composite shell in three different sections of the CNG tank and fiber angle were considered as input variables. In addition, the maximum principal stress of the component was considered as the objective function. Eventually, the fatigue life of the polymer composite tank was calculated using stress-based failure criterion. The results indicated that the proposed new design (applying optimal parameters) leads to improve the fatigue life of the polymer composite tank with polyethylene liner about 2.4 times in comparison with the initial design.

Experimental study of the strength and durability of metal-composite high-pressure tanks

The results of unique experimental studies of the strength and service life of a metal-composite high-pressure tank are presented. The goal of the study is to analyze the fracture mechanisms and evaluate the strength characteristics of the structure. The methodology included tests of full-scale samples of the tank for durability under short-term static, long-term static and cyclic loading with internal pneumatic pressure. Generalized test results and data of visual measurements, instrumental and acoustic-emission control of deformation processes, accumulation of damages and destruction of full-scale tank samples are presented. Analysis of the strength and stiffness of the structure exposed to internal pneumatic pressure is presented. The types of limiting states of the tanks have been established experimentally. Change in the stress-strain state of the tank under cyclic and prolonged static loading is considered. Specific features of the mechanisms of destruction of a metal-composite tank are determined taking into account the role of strain of the metal liner. The calculated and experimental estimates of the energy potential of destruction and the size of the area affected upon destruction of the tank are presented. Analysis of test results showed that the tank has high strength and resource characteristics that meet the requirements of the design documentation. The results of the experiments are in good agreement with the results of numerical calculations and analysis of the stress-strain state and mechanisms of destruction of the metal-composite tank.