Refueling Process Research Articles

Estimation of final hydrogen temperature from refueling parameters

Compressed hydrogen storage is currently widely used in fuel cell vehicles due to its simplicity in tank structure and refueling process. For safety reason, the final gas temperature in the hydrogen tank during vehicle refueling must be maintained under a certain limit, e.g., 85 °C. Many experiments have been performed to find the relations between the final gas temperature in the hydrogen tank and refueling conditions. The analytical solution of the hydrogen temperature in the tank can be obtained from the simplified thermodynamic model of a compressed hydrogen storage tank, and it serves as function formula to fit experimental temperatures. From the analytical solution, the final hydrogen temperature can be expressed as a weighted average form of initial temperature, inflow temperature and ambient temperature inspired by the rule of mixtures. The weighted factors are related to other refueling parameters, such as initial mass, initial pressure, refueling time, refueling mass rate, average pressure ramp rate (APRR), final mass, final pressure, etc. The function formula coming from the analytical solution of the thermodynamic model is more meaningful physically and more efficient mathematically in fitting experimental temperatures. The simple uniform formula, inspired by the concept of the rule of mixture and its weighted factors obtained from the analytical solution of lumped parameter thermodynamics model, is representatively used to fit the experimental and simulated results in publication. Estimation of final hydrogen temperature from refueling parameters based on the rule of mixtures is simple and practical for controlling the maximum temperature and for ensuring hydrogen safety during fast filling process.

THE COMPLETE MODELLING OF THE FILLING PROCESS OF HYDROGEN ONBOARD VEHICLE CYLINDERS

Complete modelling of the filling process occurring in a hydrogen-fueled vehicle storage cylinder is examined. A simultaneous modelling of the flow and heat transfer within the cylinder and cylinder wall has not been considered in previous studies. Rapid filling may result to an unexpected temperature rise and breaching of the safety standards. In the present study, initially a correlation was developed based on a numerical simulation for predicting the heat transfer rate between in-cylinder flow and the cylinder inside wall. Then, a thermodynamic model was developed for predicting transient variations of temperature and pressure inside the cylinder and wall temperature during the filling. The model was applied to a type III onboard storage cylinder filling process. The numerical results are compared with previously measured values and showed good agreement. The results also show that a great portion of heat dissipation from the in-cylinder flow is stored in the cylinder wall. It is also found that ambient temperature during the refueling process has considerable effects on filling behavior in general and in particular on the final in-cylinder temperature and filled mass.

A New Methodology for Fuel Mass Computation of an operating Aircraft

The paper performs a new computational methodology for an accurate computation of fuel mass inside an aircraft wing during the flight. The computation is carried out using hydrodynamic equations, classically known as Navier-Stokes equations by the CFD community. For this purpose, a computational software is developed, the software computes the fuel mass inside the tank based on experimental data of pressure gages that are inserted in the fuel tank. Actually and for safety reasons, Optical fiber sensor for fluid level sensor detection is used. The optical system consists to an optically controlled acoustic transceiver system which measures the fuel level inside the each compartment of the fuel tank. The system computes fuel volume inside the tank and needs density to compute the total fuel mass. Using optical sensor technique, density measurement inside the tank is required. The method developed in the paper, requires pressure measurements in each tank compartment, the density is then computed based on pressure measurements and hydrostatic assumptions. The methodology is tested using a fuel tank provided by Airbus for time history refueling process.

Thermodynamic analysis of a CNG refueling station considering the reciprocating compressor

The reciprocating compressor is the heart of a CNG refueling station with dominating influence on refueling process. The main operating cost of a CNG refueling station arises from the compressor input work. The reciprocating compressor have not been subjected to previous studies which investigated the CNG refueling stations. The main objective of the present work is to apply a thermodynamic analysis for modeling a CNG refueling station, including on-board NGV cylinder, reservoir tanks, connecting pipes and especially reciprocating compressor. Unlike most previous researches, pressure variation of the reservoir tanks during the filling process have been considered which necessary for compressor modeling. The results of the present work have been validated against the previous experimental data and theoretical studies. The additional experimental data, measured by the present authors, is also used to analyze and identify the compressor performance in unsteady conditions. The simulation result of mass flow rate is a good agreement with the experimental values. The results show that variations in the compressor discharge pressure have no effect on the first and intermediate compressor pressure. It has also no effect on the compressor delivery mass flow rate. The energy consumption by the compressor for a cycle (including discharge and charge zones) is found to be 61.86 kWh. The average specific energy consumption to fill a vehicle is found to be 0.250 kWh/kg.

Vehicular volatile organic compounds losses due to refueling and diurnal process in China: 2010–2050

Volatile organic compounds (VOCs) are crucial to control air pollution in major Chinese cities since VOCs are the dominant factor influencing ambient ozone level, and also an important precursor of secondary organic aerosols. Vehicular evaporative emissions have become a major and growing source of VOC emissions in China. This study consists of lab tests, technology evaluation, emissions modeling, policy projections and cost-benefit analysis to draw a roadmap for China for controlling vehicular evaporative emissions. The analysis suggests that evaporative VOC emissions from China's light-duty gasoline vehicles were approximately 185,000ton in 2010 and would peak at 1,200,000ton in 2040 without control. The current control strategy implemented in China, as shown in business as usual (BAU) scenario, will barely reduce the long-term growth in emissions. Even if Stage II gasoline station vapor control policies were extended national wide (BAU+extended Stage II), there would still be over 400,000ton fuel loss in 2050. In contrast, the implementation of on-board refueling vapor recovery (ORVR) on new cars could reduce 97.5% of evaporative VOCs by 2050 (BAU+ORVR/BAU+delayed ORVR). According to the results, a combined Stage II and ORVR program is a comprehensive solution that provides both short-term and long-term benefits. The net cost to achieve the optimal total evaporative VOC control is approximately 62 billion CNY in 2025 and 149 billion CNY in 2050.

Thermo-mechanical investigation of composite high-pressure hydrogen storage cylinder during fast filling

The fast refueling process of hydrogen results in a significant temperature rise within the composite hydrogen storage cylinder, which may decrease the cylinder state of charge and cause complicated thermo-mechanical behaviors of the composite structure. This study presents an analytical model, as validated by computational fluid dynamics (CFD) simulations, to study the thermal properties of composite hydrogen storage cylinder during fast filling process. A simple analytical formula for the gas temperature within cylinder and the temperature distribution in solid walls are obtained, which show intuitively the effects of different material and geometry parameters on thermal properties of the cylinder. Furthermore, a 3D finite element analysis (FEA) model, using the analytical results of temperature distribution, is proposed to investigate the coupled thermo-mechanical behaviors of the cylinder. FEA results reflect that the plastic behavior of aluminum liner effectively isolate the thermal stress, and helps to relieve the thermal effects on the whole cylinder in a large extent.

Optimizing Control Methods of Airport Pipeline Refueling Process

Due to the non-linearity and long delay of airport pipe line refueling system, it is difficult for classical control methods to ensure stable pumping pressure and refueling flow. To improve the stability of the refueling process, the paper introduces human-simulated intelligent control (HSIC) method to the recognization of refueling status, online self-adjusting and control of refueling parameters. Simulation shows that the stability and accuracy of HSIC control methods were better than that of classical PID and fuzzy PID control.

Quantifying Space Heating Stove Emissions Related to Different Use Patterns in Mongolia

A major source of particulate matter pollution in Mongolia’s capital, Ulaanbaatar, is emissions from traditional coal-burning space-heating stoves. Significant investment has been made to replace traditional highly polluting heating stoves with improved low-emission high-efficiency stoves. Performance testing that has been undertaken to support the selection of replacement stoves is typically based on manufacturers’ recommended operating procedures, which may not be representative of the operating procedures used in homes. The objective of this research is to evaluate factors that influence stove emissions under typical field operating conditions. A highly-instrumented stove testing facility was constructed to allow for rapid and precise adjustment of factors influencing stove performance. Tests were performed using one of the improved stove models currently available in Ulaanbaatar. Complete burn cycles were conducted with coal from the Ulaanbaatar region using various startup parameters, refueling conditions, and fuel characteristics. Measurements were collected simultaneously from undiluted chimney gas, diluted chimney gas, and plume gas drawn from a dilution tunnel above the chimney. Ignition events lead to increased PM emissions with more than 98% of PM mass emitted during the startup and refueling process. However, emissions during refueling are of particular interest, both because refueling is common and because refueling associated emissions appear to be very high. CO emissions are distributed more evenly over the burn cycle, peaking during ignition and late in the burn cycle. We anticipate these results being useful, in combination with behavioral surveys, for quantifying public health outcomes related to the distribution of improved stoves and to identify opportunities for improving and sustaining performance of the new stoves.

The full simulation of rapid refueling of a Natural Gas Vehicle on-board cylinder

The full simulation of the rapid refueling of a Natural Gas Vehicle (NGV) on-board cylinder is presented. The cylinder is fueled with Compressed Natural Gas (CNG). A concurrent simulation of the heat transfer and flow inside the cylinder and its wall is a troublesome work. It has not been investigated in antecedent researches. Rapid refueling may cause a surprising temperature rise, which has a significant effect on final conditions and may breach the safety standards. In this research, Firstly, based on a numerical simulation, an equation has been developed for foretelling heat transfer rate between in-cylinder flow and inner surface cylinder wall. Afterwards, a thermodynamic method has been developed for foretelling pressure and temperature variations inside the cylinder and transient wall temperature during the refueling. The method has been applied to types I and III on-board storage cylinders. The numerical results compare well with prior related experimented values. The results showed that a major portion of heat dissipation from the in-cylinder flow is reserved in the cylinder wall. It was also found that ambient temperature during refueling process has sizeable outcomes on refueling behavior in general and in particular on the final in-cylinder temperature and filled mass. The results are also presented and compared for adiabatic cylinders.

Simultaneous thermodynamic simulation of CNG filling process

Abstract In CNG station, the fuel is usually stored in the cascade storage bank to utilize the station more efficiently. The cascade storage bank is generally divided into three reservoirs, commonly termed low, medium and high-pressure storage bank. The pressures within these reservoirs have huge effects on the performance of the stations. In the current study, a theoretical simulation based on mass balance and thermodynamic laws has been developed to study the dynamic fast fi lling process of vehicle’s (NGV) cylinder from the cascade storage bank. The dynamic change of the parameters within the storage bank is also considered. Natural gas is assumed to contain only its major component, methane, and so thermodynamic properties table has been employed for finding the thermodynamics properties. Also the system is assumed as a lumped adiabatic system. The results show that the initial pressure of the cascade storage bank has a big effect on the storage bank volumes for bringing up the NGV cylinder to its target pressure (200 bar). The results also showed that ambient temperature has effect on the refueling process, chiefly the final NGV cylinder and the cascade storage bank conditions

Microgravity Experiment Research on Orbital Refueling Process in the Vane Type Tank

Aiming at vented orbital refueling, the microgravity experiment research on orbital refueling process (ORP) is carried out in the paper. By using the microgravity test system of orbital refueling and proper experiment means, the microgravity drop tower (DT) test of all the ORP is accomplished triumphantly, then the transformation process of fuel surface and flow characteristic are obtained, and the extrusion efficiency of the refueling tank is gotten, and the on-orbit propellant resupply performance of VTT is validated. The results indicate that, the orbital refueling in the vane type tank is absolutely feasible, and the performance of propellant management device (PMD) in the tank is good.

Assessment of CFD models for hydrogen fast filling simulations

High injection pressures are used during the re-fueling process of vehicle tanks with compressed hydrogen, and consequently high temperatures are generated in the tank, potentially jeopardizing the system safety. Computational Fluid Dynamics (CFD) tools can help in predicting the temperature rise within vehicle tanks, providing complete and detailed 3D information on flow features and temperature distribution. In this framework, CFD simulations of hydrogen fast filling at different working conditions are performed and the accuracy of the numerical models is assessed against experimental data for a type 4 tank up to 70 MPa.

Experimental and numerical study on temperature rise within a 70 MPa type III cylinder during fast refueling

The fast refueling of hydrogen results in a temperature rise, which may lead to the failure of the hydrogen storage cylinder. Hence, study of temperature rise during refueling is a significant concern regarding hydrogen safety. In this research, a well-design system for 70 MPa hydrogen refueling was developed. Several refueling experiments on a type III cylinder have been conducted to study the temperature rise during the refueling process on this system. The experimental results show that the gas in caudal region and the aft domes junction surface achieved the maximum temperature rise. A Computational fluid dynamics (CFD) model was also validated by the experimental results. Finally, effects of initial pressure and ambient temperature on temperature rise were studied using this model. The results show that with the increase of initial pressure and the decrease of the ambient temperature, the final gas temperature decreases approximately linearly. This pilot research can provide invaluable guidance in developing advanced refueling standard.

Optimization of hydrogen vehicle refueling via dynamic simulation

A dynamic model has been developed to analyze and optimize the thermodynamics and design of hydrogen refueling stations. The model is based on Dymola software and incorporates discrete components. Two refueling station designs were simulated and compared. The modeling results indicate that pressure loss in the vehicle's storage system is one of the main factors determining the mass flow and peak cooling requirements of the refueling process. The design of the refueling station does not influence the refueling of the vehicle when the requirements of the technical information report J2601 from Society of Automotive Engineers are met. However, by using multiple pressure stages in the tanks at the refueling station (instead of a single high-pressure tank), the total energy demand for cooling can be reduced by 12%, and the compressor power consumption can be reduced by 17%. The time between refueling is reduced by 5%, and the total amount of stored hydrogen at high pressure is reduced by 20%.

车用高压储氢气瓶快充过程温升研究进展

随着氢能汽车的发展，相关的氢安全研究得到了重视。车用氢气瓶在快充过程中由于时间较短，充装速率较快，导致产生较高温升。而复合材料氢气瓶对温度有限制，要求不高于80℃。因此，针对氢气瓶的快充温升研究具有重要的实用意义。本文从试验、数值仿真、专利、标准等方面，介绍了目前氢气瓶快充过程温升的研究进展，并提出了仍待解决的问题。 With the development of the hydrogen automobile, the relevant hydrogen safety research is paid more attention. There is a high temperature rise because the refueling time is short with a fast refueling rate. And it is required for composite materials that the temperature should be limited under 80˚C. Therefore, the research on temperature rise in hydrogen cylinder refueling process has important practical significance. This paper introduced the current de- velopment of temperature rise in hydrogen refueling process from the perspectives of the test, numerical simulation, patents, standard, etc. In addition, the problems to be solved were put forward.

Studying transmission of fuel storage bank to NGV cylinder in CNG fast filling station

The exact modeling of the fast-fill process of Compressed Natural Gas (CNG) fueled storage bank occurring to Compressed Natural Gas Vehicle (NGV) cylinders is an unintelligible process, and should be thoroughly studied. In this paper, a theoretical model based on mass balance and thermodynamic laws has been developed to study dynamic fast filling process of CNG storage bank to vehicle's (NGV) cylinder. Because Methane occupies a large percentage (between 70% to 99%) of natural gas, for the sake of simplicity it is assumed that Methane is the only substance in Natural gas and thermodynamic properties table has been employed for case of real gas model based on methane. For modeling the heat transfer, the system has been treated as an adiabatic lump one. The result shows the initial pressure of storage bank has a big effect on the storage bank volume for bringing up the NGV cylinder to its target pressure (20 MPa). The storage bank volumes required for bringing up the NGV cylinder to its final (target) pressure (20 MPa) for various initial storage bank pressure, like 20.8 MPa (RPS = 1.04), 23 MPa (RPS = 1.15) and 25 MPa (RPS = 1.25) are respectively 22, 6 and 4 times the NGV cylinder volume. It is noted that RPS is the ratio of storage bank pressure (PS) to target pressure (PT) (In this research is 20 MPa). The results also showed that ambient temperature has a big effect on refueling process, chiefly on final NGV cylinder and storage bank conditions.

Numerical Simulation and Studies of Temperature Rise within a High-Pressure Vessel during Refueling

The refueling process of a high-pressure vessel fixed on the rocket-propelled spacecraft was analyzed by the gas kinetics theories and the thermodynamics of variable mass system. A mathematical model was built up to simulate and analyze the refueling process so as to get rules of the pressure and temperature changes and lay the foundation for the design of the fast refueling control algorithm. During the simulation, the thermodynamic model based on natural convection was adopted to make the simulation close to the actual process. The studies shows that the best way to decrease the temperature of the gas within cylinder during refueling and keep the whole time prolong slightly is increase the heat transfer coefficient of cylinder and decrease the volume of stationary tank within measure.

An optimized control method for a high utilization ratio and fast filling speed in hydrogen refueling stations

A well-designed control system with a high utilization ratio of hydrogen and a fast filling speed are two critical objectives to ensure the reduction of cost and time required in the refueling process. In this paper, the popular three-stage refueling process is modeled with the aim to address both objectives. Using the real gas law of hydrogen, the utilization ratio of hydrogen filling is analyzed and the filling flowrate and time of each stage are evaluated. A multi-objective iterative optimization model is established and an optimization algorithm for the filling process is proposed to achieve both fast refueling and high utilization. Numerical results can be applied to the optimization of an actual hydrogen filling process. Besides, the tests show that an optimized control method can significantly improve the utilization ratio and allow refueling in a widely acceptable time.

A thermodynamic analysis of refueling of a hydrogen tank☆

A thermodynamic analysis of refueling of a gaseous hydrogen fuel tank is described. This study may lend itself to the applications of refueling a hydrogen storage tank onboard a hydrogen fuel-cell vehicle. The gaseous hydrogen is treated as an ideal or a non-ideal gas. The refueling process is analyzed based on adiabatic, isothermal, or diathermal condition of the tank. A constant feed-rate is assumed in the analysis. The thermodynamic state of the feed stream also remains constant during refueling. Ideal-gas assumption results in simple closed-form expressions for tank temperature, pressure, and other parameters. The non-ideal behavior of high-pressure gaseous hydrogen is addressed using the newly developed equation of state for normal hydrogen, which is based on the reduced Helmholtz free energy formulation. Sample calculations are presented using initial tank and feed stream conditions commensurate to practical vehicular applications. Comparing to the non-ideal analysis, the ideal-gas assumption always results in under-prediction of the tank temperature and pressure irrespective of the filling condition. For a given target tank pressure, the refueling time is the shortest under adiabatic condition and is the longest under isothermal condition with the tank being maintained at the initial tank temperature. The adiabatic and isothermal conditions can be viewed, respectively, as the lower and upper bounds of the refueling time for a given final target tank pressure.

Simulation of fuel behaviour during aircraft in‐flight refueling

PurposeIn‐flight refueling is one of the most important technologies developed in military aviation. The purpose of this paper is to analyze the dynamic behaviour of fuel during a refuel process by means of an internal flow analysis software program.Design/methodology/approachThe dynamic behaviour of fuel during a refuel process is analyzed by means of an internal flow analysis software program called Flowmaster. The refueling system is analyzed by representing physical components as flow resistances and control volumes and calculating the flow rates and pressures along the system. Both steady and transient state analyses are performed to identify the locations where high‐pressure surges are likely. The peak pressures are compared to allowable proof pressures of system components to ensure that they are not exceeded.FindingsIt was found that a transient analysis of the fuel behaviour in the refuel pod system for a complete refueling process can be completed successfully with Flowmaster software.Originality/valueThe paper models a complete refueling process with the sequence of trail, fuel transfer and rewind phase in order to analyse the fuel‐transient behaviour, in particular near to the times where the valves are activated.