Leakage Flow Rate Research Articles

Leakage reduction mechanism of supercritical CO2 scallop damper seal: Vortex structure and turbulence dissipation

The scallop damper seal (SDS) is a new sealing solution utilized in supercritical CO2(S-CO2) turbomachinery, and its sealing performance is of great interest. Analyzing the energy dissipation of fluid in the seal is critical for understanding the leakage characteristics of SDS. In this paper, we develop a high-order compressible flow solver with real gas thermophysical modeling. The vortex structure and turbulence dissipation of leakage flow are investigated to uncover the leakage reduction mechanism of SDS. By comparing the flow fields within a labyrinth seal (LABY) and a full-partition pocket damper seal (FPDS), we demonstrate that SDS has better leakage reduction performance for S-CO2. The results indicate that S-CO2 fluid flows into the SDS cavity and expands significantly. The formed vortex dissipates sufficiently more energy, reducing the leakage flow rate (LFR). The increase in the Mach number of the fluid flowing through the SDS gap is limited. Still, the gas permeability phenomenon caused by the throttling effect is observed in the clearance of LABY and FPDS, resulting in an increased LFR. At the differential pressure of 5 MPa, the LFR of SDS is 36.6% and 54.4% lower than that of LABY and FPDS, respectively. Although the rotor rotation leads to an asymmetric distribution of vortex in the SDS cavity, the vortex develops rapidly and occupies the entire space. For the seal design of S-CO2 turbomachinery, enhancing the turbulence dissipation of fluid in the cavity and reducing the gas permeability of fluid in clearance should be the focus of attention.

Study on hydrogen dynamic leakage and flame propagation at normal-temperature and high-pressure

Experiments of two nozzle diameters at three ignition positions under three initial pressure conditions were carried out. The dynamic leakage characteristics and the stagnation parameters of flame propagation under normal temperature and high pressure conditions were studied. Based on van der Waal's equation, a model for predicting stagnation parameters, jet velocity and flow rate of hydrogen leakage was proposed. Compared with the experimental results, it was found that the maximum error occurred when the initial pressure was 200 bar. Theoretical leakage time was 1.66 s, experiment leakage time was 1.84 s, the error was 9.8%. Background-Oriented Schlieren image technology was used to record the flame development and propagation process after ignition. For the same nozzle diameter and ignition location, the higher pressure caused the flame to propagate faster upstream and downstream. For the same initial pressure and ignition position, a flame with a large nozzle diameter propagated faster upstream and downstream. For the same initial pressure and nozzle diameter, the farther the ignition point was, the greater the slope of flame attenuation when propagating upstream. Due to the attenuation of hydrogen concentration and jet velocity, the flame propagation velocity to the downstream decreased linearly with the increase of distance from the ignition location.

Endwall geometric uncertainty and error on the performance of TUDA-GLR-OpenStage transonic axial compressor

The hub and casing walls of axial compressors are often modeled as smooth continuous surfaces in CFD simulations, but in real geometries, non-smooth pinches, steps and leakage cavities may exist. In the GPPS first Turbomachinery CFD Workshop, a comprehensive validation and verification campaign of RANS flow solvers was conducted, and all the simulation results consistently over-predicted the total pressure ratio at the rotor exit near the casing and the stator exit near the hub. From a recent examination of the test rig geometry, a pinched casing wall over the rotor and a leakage cavity below the stator were found, which were not considered in the workshop. In this paper, the effects of these endwall geometric uncertainties and errors are analyzed via numerical simulation. When considering the rotor casing pinch of the test geometry, the predicted total pressure ratio and choke mass flow of the compressor stage are smaller than that without the pinch, leading to better agreement with the measured data. When considering a stator hub cavity with a leakage flow rate of about 0.2% of the compressor inlet mass flow, the near-hub total pressure ratio distribution matches slightly better with the experimental data, but the effects on the global compressor stage characteristics are not visible. The relevant mechanisms of these changes in performances are analyzed in detail. The updated geometries and grids will be released to the public as a benchmark test case for turbomachinery CFD validation and verification.

Effects of the Shock Wave Structure on the Tip Clearance Leakage Flow in Transonic Compressor Rotors

The interaction between shock waves and the tip clearance flow in a transonic compressor rotor has important effects on the tip clearance flow and the rotor aerodynamic performance. In this paper, two transonic rotors with a high pressure ratio are selected to study the tip flow, one of which has one normal shock wave at the blade tip and the other has two shock waves (an oblique shock wave and a normal shock wave) at the tip. The two rotors have the same meridional flow channel, design point flow rate, pressure ratio, and rotation speed to focus on the influence caused by the effect of the shock wave structure. The numerical results for the flow fields show the following conclusions. The strength of the two shock waves at the blade tip is weaker than that of one normal shock, and the former two shock waves are less stable than the latter. Therefore, with increasing tip clearance, the efficiency, pressure ratio, and stall margin of the rotor with the two shock waves decrease more rapidly. The static pressure difference between the pressure and suction sides of the tip clearance is the only driving factor of the tip clearance leakage flow, and the leakage flow depends on the local pressure difference and the secondary leakage caused by adjacent blades. The movement speed of the annular wall is less than that of the leakage flow, which has a minor blocking effect on the tip clearance leakage flow. The change in tip clearance has little effect on the chordal distribution of the static pressure difference and leakage flow rate per unit area, so the total leakage flow varies linearly with the tip clearance size.

Excitation characteristics of lobe hydrogen circulating pump in polymer electrolyte membrane fuel cell under different clearances and pressure ratios

More specifications for the suction volume, hydrogen return volume, and pressure ratio of the hydrogen circulating system are needed with the development of high-power and high-efficiency vehicular polymer electrolyte membrane fuel cells (PEMFC). The working clearance and pressure ratio are essential in parameters such as pulsation characteristics, radial excitation force, leakage flow rate, and volumetric efficiency of hydrogen circulating pumps. These parameters are closely related to the noise level, reliability, and service life of the fuel cell. Transient numerical simulations of lobe hydrogen circulating pump for fuel cell vehicles (FCVs) based on CFD and dynamic mesh method were employed. The effects of four working clearances on the pulsation characteristics, flow field distribution, and radial excitation force were studied. The relationship between different pressure ratios on internal flow characteristics and volumetric efficiency was analyzed. The results showed that the pressure pulsation in the pump chamber and the radial excitation force on the lobe rotor have distinct periodicity. The radial force pulsation is minimized when the rotor-rotor clearance ζL is 0.18 mm, and the rotor-casing clearance ζr is 0.21 mm. It was found that the increase of the working clearance helps to reduce the amplitude. Moreover, as the pressure ratio rises, the pressure pulsation amplitude at the rotor-casing clearance and the leakage flow rate increase, while the volumetric efficiency decreases. The pressure ratio is the main factor affecting exhaust temperature rise.

Development of a New Loss Model for Turbomachinery Labyrinth Seals

Abstract The preliminary design of labyrinth seals requires fast and accurate estimate of the leakage flow. While the conventional bulk flow models can quickly predict labyrinth seal discharge characteristics, they lack the accuracy and pragmatism of modern computational fluid dynamics (CFD) techniques and vice-a-versa. This paper presents a new one-dimensional loss model for straight-through gas labyrinth seals that can provide quick seal leakage flow predictions with CFD-equivalent accuracy. The present seal loss model is developed using numerical experimentation technique. Multiple CFD computations are conducted on straight-through labyrinth seal geometries for a range of pressure ratios. A distinct postprocessing methodology is developed to extract the through-flow stream tube in seal. Total pressure losses and flow area variations experienced by the flow in seal stream-tube are systematically accounted for based on the well-known knife-to-knife (K2K) methodology. Regression analyses are conducted on the trends of variations of loss and area coefficients to derive the independent pressure loss and flow area correlations. These novel correlations can predict the bulk leakage flow rate, windage flow rate, and interknife static pressures over a wide range of variations of flow and geometry parameters. Validation study shows that the leakage mass flow rate predicted by this model is accurate within ±8% of measured test data. This fast and accurate model can be employed for various applications such as in seal design-analysis workflows, for secondary air system (SAS) performance analysis, and for the rotor-dynamic and aeroelastic assessments of seals.

Rupture Leakage Model for a Natural Gas Pipeline

A study to develop a rupture leakage calculation model for a natural gas pipeline was conducted. The model was based on the unsteady flow equations in the pipeline combined with the orifice outflow principle. In this article, a description of the rupture and leakage process of the gas pipeline is given. An analytical method that produces functions such as the pressure change in the leakage process, the leakage flow rate, and the cumulative leakage amount was employed. By introducing a balance factor and calculating natural gas capacity using the pipeline state equation before leakage as a reference state, the model results for the leakage process became more credible and useful. A limited exhaustive comparison method is proposed for estimating the leakage process. In the calculations, actual pipeline operational parameters were employed. The model and the proposed method are suitable for analysis and calculations of the rupture leakage of gas pipelines with cutoff devices situated at intervals of 8, 16, 24, and 32 km.

Experimental analysis and preliminary model of non-conventional lip seals

The paper describes the tests carried out to determine the applicability of a simple means for reducing friction force in linear pneumatic actuators. The idea is based on the use of commercial lip seals mounted in the direction opposite to that used in conventional systems. Two different non-conventional installations were tested using commercial spring-energized seals consisting of two different materials: virgin PTFE and graphite-filled PTFE. Tests assessed the effect of bore manufacturing tolerances with nominal bore diameters of 50.0 mm and 50.2 mm. Performance was evaluated in terms of leakage flow rate and friction force, comparing the proposed installation with conventionally mounted seals. Friction coefficient and stiffness of the two seal materials were measured on a seal segment mounted on a pin-on-disk tribometer featuring a special pin design. Tests were carried out by loading the seal segment against a portion of the cylinder barrel in reciprocating motion. Stiffness and friction coefficient measurements served as the basis for developing a preliminary lumped parameter model of the lip seal which was used to analyze lip deflections, exchanged forces and leakage flow rate between seal and barrel.

A reduced-scale experimental study of dispersion characteristics of hydrogen leakage in an underground parking garage

A medium-scale model (1/10) of an underground parking garage is designed and built to study the characteristics of the release and dispersion of hydrogen leaked from hydrogen fuel cell vehicles (HFCVs) in underground garages. Helium is used in place of hydrogen for safety reasons. The helium release experiments are conducted and the variations in helium concentrations at different locations and times in the garage model are obtained. The influence mechanisms of the leakage flow rate and nozzle diameter on the spatial and temporal distributions of the helium concentration are revealed. The experimental results show that the initial release rate of helium is the key factor affecting the distribution of helium concentrations. Both leakage flow rate and nozzle diameter have a significant influence on helium concentrations by affecting the initial release rate. If the release time is long enough, the helium concentrations will experience three stages during release, namely, rapid growth, slow growth and relatively stable. Furthermore, the beams of the garage can reduce the area on the ceiling where the hydrogen concentration exceeds the lower flammable limit (LFL). On the other hand, the beams can make it easier for local hydrogen concentrations to reach the LFL. This work can provide theoretical support for the design and construction of underground parking garages and the arrangement of hydrogen detectors.

Leakage Dynamics of Glass Bottles on Container Closure Integrity Testing: Influence of Different Laser-Drilled Microhole Geometries

Container closure integrity testing (CCIT) is a critical step in ensuring package integrity and providing feedback on package designs. In practical applications, CCIT methods, namely physical and probabilistic methods, must be appropriately selected and validated to ensure their suitability for the intended use. However, the industry still lacks practical recommendations regarding the choice of CCIT methods and artificial leaks to set the acceptance criteria. The main reason is the lack of correlation between testing methods. Artificially introduced leak microholes are the only way to determine the sensitivity of a CCIT method and to implement the method correlation. However, the type of artificial leakage is a key factor because in most studies, leakage is described and valued using a single parameter, such as size. This can significantly affect the credibility of the relevant test results, especially in the case of microbial invasion, where the difference in test conditions and samples will severely affect the probability of microbial invasion. Therefore, it is vital to conduct a systematic study on the influence of leakage conditions on CCIT methods. In this study, the influence of the shapes of artificial leaks on the two kinds of testing methods was systematically studied based on a laser-drilled microhole—a highly potential and non-exogenous artificial leak manufacturing method that can fabricate different leakage geometries. The reason for the influence of the shape of an artificial leak on the CCIT is that the deterministic method takes defects as an idealized model and ignores the influence of the leak shape, wall thickness, and other factors on leakage and pollution risks. However, these factors seriously affect the dynamic process of leakage and microbial invasion. The pressure decay method is used to test the leakage flow rate of conical and straight holes. Microbial challenge tests are then used to verify the impact of leakage shapes on the pollution risk. The results of the tests indicated that the probability of microbial invasion in the conical holes is much higher than that in straight holes with the same flow test results and that the wall thickness can also affect microbial invasion. Thus, it can be proven that the risk of leakage and invasion or the sensitivity of different methods cannot only be compared through the leak diameter. Numerous influencing factors, including leakage geometry (e.g., shape and thickness), must be considered in practical applications.

Research on measurement method for high-frequency pulsation flow of hydrogen circulating pump

The hydrogen circulating pump (HCP) used for hydrogen recovery and utilization, affects the performance of the hydrogen fuel cell system. In this paper, aiming at the measurement research blank of the output pressure and flow high-frequency pulsation curve of the HCP, a pressure-based flow measurement method and an overlapping grid-based simulation calculation method are proposed and then compared in multiple directions for mutual verification. The research results show that the waveform errors of the pressure pulsation curves are under 2.4%, and that of the flow pulsation curves are 6.2% and 8.3%, comparing the experimental data and simulation data when the average outlet pressure is 9kpa and 27kpa respectively. Further study of the internal fluid characteristics, the pressure and the density change the same and produce the lowest value before the meshing point, the leakage flow rate at the rotor-rotor gap is greater than that at the rotor-pump casing gap, and the vortices show cyclical change of co-evolution and co-growth in the low-pressure area and the high-pressure area. The research results can optimize the structural design of the HCP itself, and can also refine the input conditions of the fuel cell system and contribute to performance improvement.

Numerical Investigation on the Leakage and Rotordynamic Characteristics for a Hole-Pattern Seal in Wet-Gas Conditions

Abstract For turbomachinery working in wet-gas conditions, liquid-phase fluid may worsen the rotordynamic characteristic of an annular seal, which induces a subsynchronous vibration problem and destabilizes the rotor-bearing system. The hole-pattern seal, demonstrated as effective to eliminate synchronous or subsynchronous vibrations for gas turbomachinery, is an ideal seal scheme to increase rotor stability and liquid tolerance capability of wet-gas turbomachinery. In this paper, the leakage and rotordynamic characteristics of a hole-pattern seal are numerically investigated under wet-gas conditions, using a three-dimensional transient CFD-based perturbation method. The accuracy and reliability of the present numerical method are demonstrated based on published experimental data. The rotordynamic force coefficients are presented and compared for the wet-gas hole-pattern seal with various inlet liquid volume fractions (LVF = 0%–20%), rotor speeds (ω = 0–20 krpm), inlet preswirl ratios (Sr = −0.2–0.5), and pressure ratios (Pr = 0.3–0.7). Numerical results show that the hole-pattern seal possesses desired tolerance capability for high inlet liquid volume fraction (LVF) of up to 20%. With inlet LVF increasing from 0 to 20%, the effective damping of the hole-pattern seal increases by about 50%, suggesting an improvement in rotor stability. The leakage flow rate of the oil-air mixture increases by 97.5%, combined with the sharply increasing oil leakage flow rate (by 636%) and decreasing air leakage flow rate (by 40%). The increasing rotor speed and inlet preswirl ratio both result in an obvious increase (by 50%) in the cross-coupled stiffness, yielding a smaller effective damping and worse rotor stability. With the increase in pressure ratio, all the rotordynamic force coefficients show a weaker frequency dependency and smaller magnitudes. The swirl velocity in the seal clearance can cause an accumulation of the liquid component in the hole cavities. With the increase of swirl velocity, more liquid component accumulates in the hole cavities, and the main accumulation position gradually moves upstream.

Experimental and Numerical Investigation of High Load Turbine Blade Tip Cavity Structures

Abstract Leakage flow loss is an important factor affecting the aerodynamic efficiency of turbines. In this paper, experimental and numerical computational studies were used to investigate three different tips of a highly loaded turbine rotor. The single-cavity tip formed by squealers was considered as the original structure. Based on this, two improved structures were developed, namely, cavity winglet tip (CWT) and double-cavity combined winglet tip (DCWT). Five-hole probe and oil flow visualization were used for experimental studies, and numerical calculations were used to analyze vortex system structure and loss development. It was found that the double-cavity combined winglet tip structure can effectively change the vortex structure inside the cavity and reduce the leakage flowrate. At the same time, the aerodynamic performance was optimized by 4%.

Adaptive Dynamic Programming-Based Method for Signal Evaluation of Energy Transportation System

When a leak event happens in energy transportation system, emergency procedures would be taken by staff according to the abnormal signal evaluation result. The wrong evaluation result leads to inadequate treatment and preparation, and then the leak event would evolve to fire and explosion hazards. To solve it, a data-driven signal evaluation method based on adaptive dynamic programming is proposed in this paper. First, a signal estimation model based on three-layer neural networks is proposed to describe the pressure signal change along pipeline. Then, based on the estimation result of pressure change, a flow signal evaluation method based on value iteration scheme is proposed to obtain the leak flow rate. Moreover, the abnormal signal analysis principles are added into the iterative solving process to close to the actual leak event situation. For different leak scenarios, the proposed method could give the reasonable and reliable result through the designed neural network structures. Finally, different types of case results demonstrate that the proposed method could be applied to the signal evaluation problem.

Evaluation of the Air Leakage Flowrate in Sintering Processes

Evaluation of the Air Leakage Flowrate in Sintering Processes

Numerical investigation of the dispersion features of hydrogen gas under various leakage source conditions in a mobile hydrogen refueling station

The leakage and dispersion of hydrogen gas in a mobile hydrogen refueling station is being numerically investigated in this paper. The investigated geometry is derived from the mobile hydrogen refueling station in China. The numerical models are verified by experimental data. The hydrogen gas leaks from the hydrogen buffer tank in the form of momentum-dominated jet. The combustible danger region, the hydrogen concentration distribution, and the volume of hydrogen gas cloud are investigated. The effects of leakage positions and leakage flow rates on the characteristics and evolution of hydrogen diffusion in the mobile hydrogen refueling station and the open space are analyzed. The results show that the hydrogen concentration in the 3-way corner of the ceiling opposite the leakage orifice first reaches 0.4% and 4%. When the leakage orifice faces the sidewall of the truck container, the liquid hydrogen storage is completely surrounded by hydrogen gas clouds in the flammability limit. The maximum diffusion height of hydrogen at the lower flammable limit increased as the leakage flow rate increased, and the volume of hydrogen in the flammability limit increased virtually exponentially in the open space. The research findings provide a significant reference for potential explosion and risk assessment studies of mobile hydrogen refueling station.

TPTF horizontal flow prediction by SYS-TH codes – Recent analyses made within the FONESYS network

The horizontal stratification occurrence in water cooled nuclear reactors (WCNR) plays an important role in many transients such as loss of coolant accidents and loss of residual heat removal by influencing the liquid mass repartition, the natural circulation and reflux condenser modes, and the break or leak flowrate. A benchmark activity on horizontal flow prediction conducted in the framework of FONESYS is here presented. FONESYS is a network among code developers who share the common objective to strengthen current technology. The aim of the network is to highlight the capabilities and the robustness as well as the limitations of current SYS-TH codes to predict the main phenomena during transient scenarios in nuclear reactors for safety issues.One-hundred-twenty-six runs performed with the Two-Phase Test Facility (TPTF) are considered. Tests were selected aiming to support and complement an ongoing activity on the scalability of codes’ closure laws, currently focusing on the horizontal stratification criteria, the onset of droplet entrainment and entrainment fraction criteria. Therefore, experimental tests performed with the 4-inch and 8-inch tests sections, at pressure ranging from 30 bar to 118 bar, in different flow regimes are considered. Focus is put on the capability of ATHLET, CATHARE 3, MARS-KS, RELAP5, RELAP5-3D, SPACE and TRACE in predicting void fractions, the transition to slug flow and the onset of droplet entrainment.Overall, the benchmark results show reasonably good capabilities of codes in predicting horizontal flow. However, some noticeable limitations emerged related to flow regime transition criteria, interfacial friction, and to the prediction of non-established flow. The scalability of closure laws and possible ways for improving them are discussed.

A Comparison of Static and Rotordynamic Characteristics for Three Types of Impeller Front Seals in a Liquid Oxygen Turbopump

Abstract Annular seals are widely used to minimize the leakage, and improve efficiency and rotordynamic stability in turbomachinery. In a liquid oxygen turbopump, the operating conditions of annular seals are harsher with the high-pressure cryogenic propellant. Researches show that the primary leakage of a liquid oxygen turbopump is from the front and rear shoulder seals of the impeller. Moreover, the impeller shoulder seal sustains the largest pressure drop and highest swirl velocity in machine. Therefore, the shoulder seal plays an important role in rotor stability and successful full load operation of the turbopump, due to the significant seal fluid response forces. Previous literature shows that the hole-pattern seal has excellent performance in rotordynamic characteristics, and its leakage rate shows a very weak sensitive to the rotating speed. For helical-groove seal, however, the leakage shows a significant decrease with the increasing rotating speed and the roughness on stator surface can enhance the “pump effect” of helical-groove. The static and rotordynamic characteristics of annular seals with cryogenic liquid oxygen are limited in the previous literature. To make use of the advantages of both types of seals and address the sealing challenge in liquid oxygen turbopump, three types of liquid annular seals were designed for the front shoulder seal of a liquid oxygen turbopump, which include a hole-pattern seal (HPS), a double helical-groove seal (DHG), and a hybrid damper seal (HDS, with hole-pattern on stator and helical-groove on rotor). Computational fluid dynamics (CFD), as an important method to solve fluid dynamic problems, has been widely used to solve fluid governing equations. To assess and compare the leakage and rotordynamic characteristics of the present three types of annular seals under the liquid oxygen medium, a steady three-dimensional CFD method was developed to predict the seal leakage, based on the Frozen Rotor interface model. A transient three-dimensional CFD-based perturbation method was also proposed to predict the seal rotordynamic characteristics, based on the subdomain method, mesh deformation technique, and multiple-frequency elliptical-orbit whirling model. The accuracy and reliability of the present numerical methods were demonstrated based on the experimental data of leakage rates and rotordynamic coefficients for an experimental hole-pattern seal and an experimental helical-groove seal using water as working fluid. The leakage rate and rotordynamic coefficients of these three types of annular seals were calculated and compared under six variable load-operating conditions of a liquid oxygen turbopump, focusing on the seal leakage rate, effective stiffness, and damping. The numerical results show that compared with the traditional hole-pattern seal and helical-groove seal, the novel hybrid damper seal possesses the much less leakage flow rate and much better rotordynamic characteristics, so is a desired seal scheme for the impeller shoulder seal.

A novel approach for suppressing leakage flow through turbine blade tip gaps

Tip clearance leakage flow of the turbine bade is an important factor limiting the augment of the high pressure turbine efficiency, which should be suppressed utilizing certain methods. However, the passive control method with the traditional structure is more and more difficult to satisfy the suppressing ability of the advanced turbine demand. In the present paper, a synergetic suppressing method by combining the approach of blade shape modification and spontaneous injection is adopted, to construct a novel tip structure. The aerodynamic characteristics of the tip leakage flow (TLF) with different blade tip configurations, such as the squealer, squealer-winglet (SW) and squealer-winglet-spontaneous injection holes (SWS) composite configurations, are numerically investigated. The impacts of several key geometric parameters, such as the winglet width and the space ng of spontaneous injection holes, are also discussed. Due to the adjustment of the winglet, the SW tip configuration can get better suppressing effect on TLF than the squealer tip. The SWS synergetic suppression tip decrease the leakage flow rate and the leakage mixing loss on the basis of the SW tip due to the blocking effect of the spontaneous injection flow. The key geometric parameters study shows that the suppressing effect of the TLF can be improved by reasonably increasing the winglet width and reducing the spacing between spontaneous injection holes.

The effect of hydrogen leakage positions and leak flow rate on its dispersion in a small fuel cell bus

AbstractStudies on hydrogen leakage mainly have focused on the influences of the leakage locations and geometrical configurations on the distribution of hydrogen in various spaces. In this study, a simplified model was developed to examine the diffusion of the hydrogen leaked into a small fuel cell bus with seats. The impact of leakage positions and leak flow rate on the dispersion of hydrogen in a cuboid ventilation space (with dimensions L x W x H = 5 m × 2 m × 2 m) was investigated, and concentrations of hydrogen in the vicinity of the corner at the ceiling were of particular interest. It was shown the peak average concentration at the ceiling increased with increasing the leak flow rate. However, the duration from the appearance to the disappearance of the combustible hydrogen‐air mixture decreased with the increase of the leak flow rate. This study highlights the importance of leakage positions and demonstrates that the dispersion of hydrogen is faster for leakage in the horizontal direction. The proposed approach is useful for improving the design of the arrangement of hydrogen storage tanks to eliminate consequent accidents or minimize the harmful impacts during an accident.