High-pressure Leakage Research Articles

Progress in spontaneous ignition of hydrogen during high-pressure leakage with the considerations of pipeline storage and delivery

High-pressure pipeline storage presents a promising method for widespread and efficient hydrogen transfer. However, challenges arise in mitigating pressurized hydrogen leakage due to hydrogen embrittlement issues associated with conventional pipeline materials. Experimental findings indicate that pressurized hydrogen is prone to spontaneous combustion, even at relief pressures as low as approximately 2 MPa - well below the permissible pipeline pressure in most countries. Despite this, there remains a lack of consensus regarding the mechanism of spontaneous ignition from high-pressure hydrogen leakage, and current research in this area is deemed insufficient. This study aims to analyze and discuss the presumed mechanisms of spontaneous ignition comparatively, review the progress in the study of spontaneous ignition of hydrogen in high-pressure leakage based on diffusion ignition theory, and statistically compare and discuss the influences of significant factors existing in pipelines (e.g., macro size factors and internal structure) and/or pipe failures (e.g., rupture factors) on spontaneous ignition. It is hoped that this article will provide scholars involved in the development of hydrogen energy and the theories of spontaneous combustion with a systematic understanding of these phenomena.

Test on High Pressure Leakage of Diesel Needle Valve Coupler Based on Artificial Intelligence Algorithm

Test on High Pressure Leakage of Diesel Needle Valve Coupler Based on Artificial Intelligence Algorithm

A pressure-ratio equivalent method for ultra-high pressure hydrogen spontaneous ignition experiment

Increasing hydrogen storage pressure brings high economic benefits and high risks. Pressurized hydrogen leakage spontaneous ignition experiment is an important means to reveal the mechanism of hydrogen leakage spontaneous ignition and improve the safety of hydrogen storage equipment. However, due to the extremely high cost and danger of ultra-high pressure, there is a serious lack of experimental data. In this paper, a pressure-ratio equivalent (PRE) method of experiments is proposed based on the theory of the shock tube problem. By keeping the hydrogen-air pressure ratio constant while reducing the absolute pressure of air and hydrogen, the difficulty of the experiment is greatly reduced. The effectiveness of the PRE method is evaluated theoretically and experimentally. The results show the PRE method retains the ignition characteristics of hydrogen leakage spontaneous ignition largely when the air pressure is within 0.05–0.1 MPa. It is found the pressure ratio of hydrogen to air dominates the leakage spontaneous ignition process. In the experiments of different air pressures, the shock Mach numbers are close to theoretical values. In addition, leakage spontaneous ignition of hydrogen mixed with 30% (vol.) CO is found in experiments using the PRE method, with pressure ratios of up to 250. This indicates that when the storage pressure is high enough, there is also a risk of spontaneous ignition of syngas from high-pressure leakage. The PRE method can widely broaden the pressure scope of experimental research on leakage spontaneous ignition, and it provides a new idea for obtaining the experimental data of gas high-pressure leakage spontaneous ignition.

Lost circulation materials for deep and ultra-deep wells: A review

The number of deep wells and ultra-deep wells drilled worldwide is gradually increasing, and the problem of deep well leakage has become one of the challenges in drilling. The high-temperature and high-pressure environment in deep formations severely test the drilling leakage control. The lost circulation material and its nature largely determine the success rate of deep well leakage control. The paper discusses the failure and instability mechanism of the lost circulation materials in deep wells and the plugging zone formed by them. The lost circulation materials are classified as physical and chemical lost circulation materials. It includes bridge plugging materials, high filtration loss plugging materials, organic gel plugging materials, expansion plugging materials, resin plugging materials, and inorganic gel plugging materials. According to the published evaluation and analysis of temperature and pressure resistance of leakage lost circulation materials, the characteristics of different types of temperature and pressure resistance leakage lost circulation materials are summarized. Based on a large number of existing researches and the practice of the team on high temperature and high-pressure leakage plugging, the research on the theory of high temperature and high-pressure leakage plugging and the research adaptability of high temperature and high-pressure resistant materials, the research on new physical and chemical temperature and pressure-resistant materials, the composite leakage plugging method and its suitability Prospects are put forward in terms of temperature and pressure plugging technology and strive to improve the success rate of loss control in deep wells.

Jet fires involving releases of gas and solid particle

The high-pressure leakage of underground pipeline could entrain the nearby sands and soils, and thus cause the jet fire of gas-solid mixtures. In addition, the thermal runaway of Lithium ion batteries could also cause a typical gas-solid jet diffusion flame. In comparison with the gaseous jet diffusion flame and the gas-solid-air jet premixed flame, the gas-solid jet diffusion flame lacks of exploration. Thus, a new facility consisting of a jet fire apparatus and a sand feeder, was designed to explore the gas-solid jet fire. The test repeatability was justified for the proposed facility. The dynamical differences of gas-solid and gaseous jet fires are clarified. It is found that the gas-solid jet fire holds a larger lift-off height, a less visible flame height and a less radiative fraction than the purely gaseous jet fire. In particular, for gas-solid jet fires at high exit velocities, the lift-off height increases, but the visible flame height and radiative fraction seem to decrease, as the particle size of sand decreases to increase the jet height of sand. (1) Inside the flame volume, the sand plays a role of heat sink to decrease the flame temperature and thus the flame burning velocity. Moreover, in the lift-off region, the sand dilutes the gas fuel and isolates the surrounding oxygen to inhibit the combustion. Both effects of sand cause a large lift-off height, especially for the sand of little particle size. (2) A large lift-off height means the increase of the air mass entrained from flame base or the portion of the premixed flame to the whole flame. In addition, the sand particle-laden flow would significantly increase the ambient air entrainment rate of fire plume. Both effects result in a less visible flame height. (3) The portion of the premixed flame increases in the bottom, which reduces the total soot amount inside the whole flame volume. The decrease of the flame temperature and the total soot amount reduces the radiative fraction. (4) The sand significantly affects the flame geometry and radiative fraction, which alters the radiant heat flux distribution and challenges the development of thermal radiation model for gas-solid jet fires. The gas-solid jet fire holds a less peak radiant heat flux but a higher positon of peak radiant heat flux than the gaseous jet fire. In addition, the line source radiation model available in literature is revised to well predict the radiant heat flux distribution of the gas-solid jet fires.

Kinetic Analysis on Spontaneous Combustion of Pressurized Hydrogen in Tubes.

Highly pressurized hydrogen storage is considered as one of the best methods currently due to its economic performance. However, the highly pressured storage technology is facing the threat of spontaneous combustion of high-pressure leakage, and there is still a lack of research on the kinetics of chemical reactions in the spontaneous combustion process, which greatly restricts the development of safe and efficient hydrogen-storage technology. Therefore, in this study, a three-dimensional simulation using the open-source packages OpenFOAM with a detailed kinetic model is proposed to analyze the hydrogen spontaneous combustion process in tubes. Subsequently, the effects and mechanisms of release pressures and tube geometry parameters are studied by means of kinetic simulation. The results show that the magnitude of the release pressure and tube diameter and length directly affects the spontaneous ignition and the location. In order to get more deep insights into the pressurized hydrogen release, reaction path analysis is performed. Three different hydrogen-consumed channels are found by reaction path analysis. The special performances found in spontaneous ignition with different release pressures and tube geometry parameters are caused by the competition between the chain-terminating channel and chain-branching channel. This work provides novel insights to understand the hydrogen spontaneous combustion process and enhances the theoretical basis for seeking safe hydrogen-storage means.

Feasibility study of detecting gas leakage in buried pipeline based on resistivity method

Urban gas pipe networks are mostly buried underground and it is hard to monitor, detect and locate the leakage area effectively. The primary structure of the soil could change before and after aeration, so the detection method of gas leakage based on resistivity method has some physical basis. Based on the theoretical research of the predecessors, corresponding geoelectric model is established by combining two typical gas leakage geological models to study the influences of testing device, leakage mode and leakage intensity on the distribution characteristics of gas leakage geoelectric field. Obtained by using forward and inverse numerical computation methods, the theoretical resistivity profile image is compared with the resistivity profile measured by outdoor gas leakage simulation experiment to evaluate comprehensively the feasibility and effectiveness of detecting gas leakage of buried pipelines based on resistivity differential characteristics. The research results show that resistivity method could describe the spatial distribution location effectively and the electrical resistivity has positive correlation with leakage pressure. And the pressure inside the pipeline also determines the migration path of the gas leakage, which diffuses outwards in the shape of “smoke ring” in high-pressure leakage.

Influence of Impeller Gap Drainage Width on the Performance of Low Specific Speed Centrifugal Pump

The centrifugal pump is one of the most important pieces of energy-consuming equipment in various hydraulic engineering applications. This paper takes a low specific speed centrifugal pump as the research object. Based on the research method combining numerical calculation and experimental verification, the influence of the gap drainage structure on the performance of the low specific speed centrifugal pump and its internal flow field distribution were investigated. The flow field inside the low specific speed centrifugal pump impeller under different gap widths was studied. The comparison between the numerical calculation results and the experimental results confirms that the numerical calculations in this paper have high accuracy. It was found that the gap drainage will reduce the head of the low specific speed centrifugal pump, but increase its hydraulic efficiency. Using a smaller gap width could greatly improve the performance of the low specific speed centrifugal pump on the basis of a slight reduction in the head. The high-pressure leakage flow at the gap flows from the blade pressure surface to the suction surface can effectively suppress the low-pressure area at the impeller inlet. The flow rate of the high-pressure leakage flow increases with the gap width. Excessive gap width may cause a low-pressure zone at the inlet of the previous flow passage. These results could serve as a reference for the subsequent gap design to further improve the operating stability of the low specific speed centrifugal pump.

Prediction of the failure probability of the overhead power line exposed to large-scale jet fires induced by high-pressure gas leakage

A thermal failure model (TFM) is proposed to predict the failure probability of Aluminum Conductor Steel-Reinforced (ACSR) typed power line close to a large-scale jet fire of leaked high-pressure gases. It introduces a newly developed method for heat transfer from jet fires and a distribution model for conductor failure probability via IEEE Standard 738–2012. Comparisons covering van der Waals equation, jet flame length correlations (Chamberlain, Schefer, Molkov and Bradley) and thermal radiation models (point source, multi-point source and line source) were made to illustrate priority with respect to experimental measurement of large hydrogen and natural gas jet fires. Results show that a theoretical framework incorporating van der Waals equation, Molkov's correlation for jet flame length, radiative fraction model and point source model is adequately precise to predict high-pressure leakage process, total flame length and received radiant heat flux (far-field). Predicted total flame lengths of a large jet fire for nearby power lines within 50–200 m to the accident site correspond well to reported results and the conservative hazard ranges are predicted based on harm criteria of wood and Probit equations. In simulations, an acceptable safety distance for power line carrying 907 A and below is determined to be 150 m.

Prediction of Flame Length of Horizontal Hydrogen Jet Fire during High-pressure Leakage Process

Abstract In recent years, jet fire accidents caused by gas tank or pipe leakage are often reported to cause more serious losses and even induce a series of other accidents, especially for high pressure jet fires. This paper presents an integrated model which couples the leakage process model of Abel-Noble equation of state (AN-EOS), the notional nozzle model and the flame size (flame length and lift-off height) model. The model can be used to predict the variation of jet flame length induced by the unsteady leakage of high pressure flammable gas. The lift-off height correlation is proposed after a review on the jet fire behavior, and then the AN-EOS leakage process model is evaluated through a testing on the vessel gas pressure variation against the measurement in literature. The integrated model is finally evaluated through a testing on the variation of flame length with vessel gas pressure against the measurement in literature. Results indicate that the integrated model is applicable for jet flame length prediction. More experimental data on high pressure horizontal hydrogen jet fires is needed for evaluation and validity of the integrated model.

Novel microfluidic interconnectors for high temperature and pressure applications

Reliable microfluidic interconnectors are one of the basic building blocks of integrated fluidic and chemical reaction systems-on-chip. Though many ideas have been proposed and implemented in the literature for creating different kinds of macro-to-micro fluidic connections, development of integrated on-chip connectors for high temperature and pressure microfluidic applications has not been properly studied. Such connectors will be indispensable in true on-chip chemical processing applications for reactions which require more severe operating conditions than those possible using currently available interconnection techniques. In this paper we present novel microfluidic interconnects that can be used in applications involving operating temperatures of up to 275 °C and pressures in excess of 315 Psi (21.43 atm). The only wetted surfaces in this design are teflon, silicon and pyrex glass, making the design inert to most chemicals. High-pressure leakage, pull-out and high-temperature durability tests conducted on the interconnect show that the connections obtained are superior to those reported in the literature using other techniques. Structural analysis of the interconnect is carried out to illustrate the effect of interconnect geometry on strength and high-pressure performance.