Initial Gas Pressure Research Articles

Quantitative study on gas dynamic characteristics of two-phase gas-solid flow in coal and gas outbursts

The dynamic effect of coal and gas outburst seriously threatens the safety of underground equipment and workers in mines. In this paper, the models for outbursts are established, and according to the energy transformation during gas expansion process, three parameters of the release of gas pressure potential energy are defined and the gas dynamic characteristics of two-phase flow in the initiation stage are quantitatively studied under the four factors: initial gas pressure, particle volume fraction, particle size and outburst hole size. The gas dynamic characteristics in numerical simulations are verified by experiments. The results show that for the influence of the factors on the gas dynamic characteristics of two-phase flow, initial gas pressure >outburst hole size >particle volume fraction ≈particle size. The solid particles block the pressure potential energy release from chamber, so does the caliber. However, the maximum of pressure drop occurs when the caliber is 80% of the chamber, which explains the outbursts in mines are so violent due to the caliber smaller than the internal space. This paper provides a novel quantitative research method of gas dynamic characteristics of coal and gas outburst, which is of guiding significance to the design of outburst prevention facilities and emergency rescue measure.

Production of Cast Materials Based on the Cr2AlC MAX Phase by SHS Metallurgy Using Coupled Chemical Reactions

It is known that materials based on MAX phases possess a large potential for use in aerospace, automobile, and industrial spheres because they have a unique combination of features of both metals and ceramics with high mechanical, chemical, thermal, and electrical properties. In this work, the experimental results of fabricating cast materials in the Cr–Al–C system with different ratios between the Cr2AlC MAX phase and chromium aluminides and carbides by SHS metallurgy are presented. The experiments were performed in an SHS reactor 3 L in volume at an initial inert gas (argon) pressure of 5 MPa. The synthesis was performed based on chemically coupled reactions: weakly exothermic (heat acceptor)—Cr2O3/3Al/C and strongly exothermic (heat donor)—3CaO2/2Al. The experimental results have good correlation with the preliminary thermodynamic calculations. It is shown that, when varying the composition of initial mixtures, it is possible to substantially affect the calculated and experimental synthesis parameters, as well as the phase composition and microstructure of final products. Optimal synthesis conditions of the material providing the maximal yield of the Cr2AlC phase in the ingot composition are established. The determining factor affecting the Cr2AlC content in the product is the occurrence time of the liquid phase under the synthesis conditions. It is shown that the maximal content of the Cr2AlC MAX phase and target product yield are attained at the 30% content of the strongly exothermic additive (3CaO2/2Al) in the initial charge.

Comparison of megaampere channel temperature value measured by different methods at its maximal contraction in high density hydrogen

Comparison of discharge channel temperature in gaseous hydrogen of high density with current amplitude of ~ 1 MA at initial gas pressure of 5–7 MPa, determined by two methods, was done under stage of its maximal contraction. In the first case determination of the temperature value of 72–73 eV was made by intensity of soft x-ray radiation from the channel for experiments with current amplitude of 1.1–1.5 MA. The estimation of the temperature on the basis of the data received by magnetic probe method and specified electric characteristics of the channel was of ≈ 140 eV for experiment with initial gas pressure of 5 MPa at current amplitude of 0.93 MA. The temperature determination by the last procedure has small accuracy caused by the limitation of the magnetic probe technique in determination of the channel contraction ratio and some assumptions for near-electrode voltage drops calculations by this way. Apparently, the channel temperature in stage of maximal contraction is of ~ 100 eV.

Gas-driven rapid fracture propagation under unloading conditions in coal and gas outbursts

Coal and gas outbursts have long posed a serious risk to safe and efficient production in coal mines. It is recognised that coal and gas outbursts are triggered by excavation unloading followed by gas-driven rapid propagation of a system of pre-existing or mining-induced fractures. Gas-filled fractures parallel to a working face are likely to experience opening first, then expansion and rapid propagation stages under unloading conditions. The fracture opening is driven by the effective stress inside the fracture, while the fracture expansion and rapid propagation is propelled by the pressure build-up of desorbed gas in the vicinity of the fracture. Based upon this understanding, this research aimed to identify the key factors affecting outburst initiation and its temporal evolution during roadway developments. Specifically, the response of pre-set fractures in a thin coal seam sandwiched between rock layers to roadway development is simulated using a geomechanical model coupled with fracture mechanics for fracture opening and propagation. In addition, kinetic gas desorption and its migration into open fractures is considered. During simulations outburst is deemed to occur when the fracture length exceeds the dimension of a host element. The findings of this research suggest that the simulated coal and gas outburst caused by roadway development may be considered as a dynamic gas desorption-driven fracture propagation process. The occurrence of coal and gas outbursts is found to be influenced mainly by the coal properties, fracture attributes, and initial gas pressure and the in situ stress conditions. Furthermore, the model predictions in terms of dome-shaped erupted-zone and layer-by-layer coal breakage are consistent with the field reports. In addition, the model results suggest that delayed occurrence of coal and gas outbursts, especially after sudden exposure of a coal seam or after blasting disturbance, reported in the literature may be related to the gas desorption behaviour.

Numerical investigation of energy deposition in spark discharge in adiabatically and isothermally compressed nitrogen

The paper presents a comparative study of a spark discharge evolution in nitrogen for cases of its isothermal and adiabatic compressions. A numerical model of a spark channel expansion which was previously tested in a wide range of spark discharge energies was used for this purpose. The model takes into account electric circuit parameters, gas-dynamic expansion processes, thermal gas ionization, non-equilibrium chemical reactions, electron heat transfer and radiation. The initial pressure of adiabatically and isothermally compressed discharge gas was varied in a range from 1 to 20 atm. A capacitor with capacitances of 0.1 and 0.01 μF and a circuit inductance of 2 μH were applied in the calculation. The charge voltage was 30 kV. An influence of initial gas pressure on energy deposited by spark discharge, the efficiency of spark energy deposition, the parameters of the shock wave generated by the spark discharge, the efficiency of the discharge-to-radiation energy conversion and the resistance of the spark channel were finally evaluated. A correlation coefficient was introduced to reflect the initial pressure influence on the energy deposition. The coefficient can be used to imitate an equivalent spark load for any initial pressure.

A reduced chemical kinetic reaction mechanism for kerosene-air combustion

Development of a new reduced chemical kinetic reaction mechanism for kerosene-air combustion is presented. The new mechanism uses a modular based development technique and is a further development on previously presented kerosene-air mechanisms. The new mechanism consists of 30 species and 77 irreversible reactions and is developed to accurate reproduce key flame parameters yet being small enough to be used in finite rate Large Eddy Simulations (LES), Direct Numerical Simulations (DNS) and in Reynolds Average Navier-Stokes (RANS) simulations. The well-proven development technique uses a refined fuel breakdown oxidation sub-mechanism, a simplified C2 intermediate species sub-mechanism and a more detailed set of reactions for the H/C1/O chemistry. The mechanism has been modified to be able to predict ignition delay times for a wide range of temperatures, including in the negative temperature regime.The mechanism has been evaluated for combustion parameters related to flame propagation and ignition over a wide range of equivalence ratios, initial gas temperatures and pressures. Agreements to experimental data and a set of detailed and skeletal mechanisms are good for all target parameters. The proposed mechanism shows good agreement at a computational cost far below all tested reference mechanisms, making it highly suitable for use in combustion computational fluid dynamic (CFD) simulations.

Measurement and modeling of temperature evolution during methane desorption in coal

The decrease of coal temperature has been confirmed by many tests during methane desorption in coal, including coal and gas outburst, but the thermal-dynamic process for methane desorption has not been quantitatively studied. Therefore, firstly, the coal temperature and gas pressure are measured by temperature and pressure sensors in the process of methane desorption. Secondly, isosteric heats of adsorption are calculated according to the adsorption isotherm. Finally, heat transfer model is established and simulate the temperature evolution during methane desorption in coal under different conditions (initial temperature and gas pressure). The real tests and simulation results show that a lot of heat will be absorbed from coal as methane desorbing, which causes the coal temperature will go down by 5.5 K, and methane desorption is no longer isothermal process. In the initial stage of methane desorption in coal, the coal temperature will decrease sharply to an extremely low value, then slowly rise to the previous ambient temperature. And at the same ambient temperature, the higher the initial methane equilibrium pressure is, the larger the temperature at the coal body center drops in the process of methane desorption. In the coal body, the farther away from the wall of the coal sample canister, the more significant the decrease of the coal body temperature is, and the longer the time is to reach extremely low value, which is mainly due to the different heat transfer coefficients at different positions in the coal body. The total specific power, which is a key index in heat transfer model to simulate the change of coal temperature, sharply decreases during methane desorption, because the methane desorption quantity in unit time decreases gradually. This study has an important practical significance to reveal the evolution mechanism of coal and gas outburst, and predict outburst with temperature change as an index.

Quasi-0D-Model Mapping of Reflected Shock Tunnel Operating Conditions

Reflected shock tunnels have been widely used for ground testing of hypersonic airbreathing engines. These facilities are able to replicate the total enthalpy and pressures experienced along hypersonic flight trajectories. Designing the relevant operating conditions is complex, and extensive guidance about operation condition design in reflected shock tunnels is scarce. To facilitate the operation of a reflected shock tunnel, it may be advantageous to develop a database of attainable conditions and the operation parameters required to achieve them. For this, a model to calculate global thermodynamic states and shock speeds also accounting for piston location and tube length (quasi-0D-model) is proposed. This model uses the NASA Chemical Equilibrium with Applications code to solve real gas and high-temperature effects. A number of conditions are calculated to produce maps of operating conditions. As test cases, the reflected shock tunnel under development at Tokai University, and T4 at the University of Queensland are used. Maps obtained sweeping rupture pressure or compression ratio, and initial test gas pressure for different driver compositions are presented. This methodology can be adapted to similar facilities. Moreover, observation of the presented maps provides a quick reference of the influence of each parameter when modifying existing conditions or fine-tuning tunnel operation.

Hybrid Finite‐Discrete Element Modelling of Excavation Damaged Zone Formation Process Induced by Blasts in a Deep Tunnel

A brief literature review of numerical studies on excavation damage zone (EDZ) is conducted to compare the main numerical methods on EDZ studies. A hybrid finite‐discrete element method is then proposed to model the EDZ induced by blasts. During the excavation by blasts, the rock mass around the borehole is subjected to dynamic loads, i.e., strong shock waves crushing the adjacent rocks and high‐pressure gas expanding cracks. Therefore, the hybrid finite‐discrete element method takes into account the transition of the rock from continuum to discontinuum through fracture and fragmentation, the detonation‐induced gas expansion and flow through the fractured rock, and the dependence of the rock fracture dynamic behaviour on the loading rates. After that, the hybrid finite‐discrete element method is calibrated by modelling the rock failure process in the uniaxial compression strength (UCS) test and Brazilian tensile strength (BTS) test. Finally, the hybrid finite‐discrete element method is used to model the excavation process in a deep tunnel. The hybrid finite‐discrete element method successfully modelled the stress propagation and the fracture initiation and propagation induced by blasts. The main components of the EDZ are obtained and show good agreements with those well documented in the literature. The influences of the initial gas pressure, in situ stress, and spacing between boreholes are discussed. It is concluded that the hybrid finite‐discrete element method is a valuable numerical tool for studying the EDZ induced by blasts in deep tunnels.

A method for simultaneously determining axial permeability and transverse permeability of tight reservoir cores by canister degassing test

AbstractPermeability anisotropy of shale and tight gas reservoirs is critical for applications in unconventional gas recovery, but laboratory measurements are still limited. This paper presents an experimental method for determining permeability anisotropy of shale and tight reservoirs. The method uses gas production data from a canister and an analytical solution of continuity equation in anisotropic core sample. Axial permeability and transverse permeability of the core are estimated by matching experimental data with analytical solution. The proposed method is verified by comparing with true values and calculated values through numerical simulations that cover variations in rock permeability. The method is applied to real data measured in canister degassing tests (CDT) involving two different directional shale core samples. Then, the experimental results are compared with the results from pulse pressure decay (PPD) method. Both the verification from numerically calculated results and the comparison between PPD results and CDT results exhibit the practicality of the proposed method. At last, the effects of permeability anisotropy, porosity, initial gas pressure, rock dimensions, and adsorption on the profiles of gas production are investigated.

Production of cast materials based on Cr<sub>2</sub>AlC MAX phase by SHS metallurgy using coupled chemical reaction

It is known that materials based on MAX phases have great potential for aerospace, automotive and industrial applications due to a unique combination of features offered by both metals and ceramics with high mechanical, chemical, thermal and electrical properties. This paper provides the results obtained by the SHS metallurgy of Cr–Al–C materials with different ratios between the MAX-Cr 2 AlC phase, carbides and chromium aluminides. Experiments were carried out in a 3-liter SHS reactor at an initial pressure of inert gas (Ar) of 5 MPa. The synthesis process was carried out based on coupled chemical reactions: weakly exothermic (heat acceptor) – Cr 2 O 3 /3Al/C and strongly exothermic (heat donor) – 3CaO 2 /2Al. The obtained experimental results have a good correlation with previously performed thermodynamic calculations. It is shown that varying the composition of the initial mixtures can significantly influence the calculated and experimental synthesis parameters as well as the phase composition and microstructure of final products. The paper establishes optimal conditions for material synthesis providing a maximum output of the Cr 2 AlC MAX phase in the ingot composition. A determining factor influencing the Cr 2 AlC content in the final product is the time of liquid phase presence under synthesis conditions. It is shown that the maximum content of the Cr2AlC MAX phase and the target product yield is achieved at the highly exothermic additive (3CaO 2 /2Al) content of 30 % in the initial mixture.

A new catalyst (colemanite) for coal-to-liquid technology; a case study for the liquefaction of Elbistan Lignite: the effect of colemanite and Fe2O3 catalyst blending

In this study, the colemanite (a natural calcium borate mineral, NCBM) and Fe2O3 used as a catalyst on the liquefaction of Elbistan Lignite (EL, which has the most reserves in the east of Turkey). The liquefaction experiments were carried out at the reaction temperature of 400 °C, the reaction time of 90 min, the solvent/solid ratio of 3/1, stirring speed of 400 rpm, and initial nitrogen gas pressure of 20 bar. Fe2O3 and colemanite were together prepared as a new catalyst. Research has been made the recent observation that the highest liquefaction product yields, especially from a series of valuable fractions, obtained, with the highest mineral content of lignite. According to that model colemanite mixed with Fe2O3 to decide if the mineral content effect on total conversion if mineral substances added separately from coal. Fe2O3 selected as the most suitable catalyst type. To understand how to affect colemanite (as an economical catalyst source and also has high reserves in Turkey) as a catalyst on the liquefaction of EL with waste paper. The experiment conditions fixed and so compared due to the total conversion values. Unlike previous studies, this study was 67.1% of the total fluid conversion without catalyst, but this value increased to 77.6% when 15% NCBM catalyst was used. The total conversion was up to 83.8% with the catalyst concentration of 3% Fe2O3. On the other hand, when only 3% of Fe2O3 was used, the total conversion was only 75%. As a result, the mixture of NCBM and Fe2O3 increased the liquefaction efficiency by 15% by the synergistic effect.

Effect of Sodium Boron Hydride (NaBH4) on Waste Polyethylene Terephthalate Pyrolysis

Polyethylene terephthalate, which is used in many applications today, is very important in terms of nature and source in order to ensure recycling by appropriate methods after use. Because polyethylene terephthalate is a durable and long-lasting thermoplastic which is resistant to many environmental influences. Recovering residual plastics has become mandatory. In this study, the conversion of waste plastic to a new liquid fuel by polyethylene terephthalate (PET) pyrolysis method was investigated. Sodium boron hydride (NaBH4) was used as both catalyst and hydrogen donor in the pyrolysis experiments. Pyrolysis experiments were carried out in a batch reactor under catalytic and non-catalytic conditions, reaction time of 15-90 minutes, reaction temperature of 325-425 °C, solid/solvent ratio of 1/4 and initial nitrogen gas pressure of 20 bar. According to the results obtained, the most suitable reaction temperature was found to be 375-425 °C and the reaction time was 30 minutes. At the reaction times of 30 minutes, the maximum total conversion in non-catalytic conditions of waste polyethylene terephthalate samples was 53.1% at 400 °C reaction temperature and the highest oil + gas yield was 43.7% at 425 °C reaction temperature. In the pyrolysis of polyethylene terephthalate samples in the presence of sodium boron hydride, the maximum total conversion was 55.3% at 400 °C reaction temperature and the highest oil + gas yield was 44.6% at 425 °C reaction temperature. As a result, it can be argued that sodium boron hydride used in pyrolysis experiments of waste polyethylene terephthalate acts as both catalytic and hydrogen donor.

A Thermo–Hydro–Mechanical Model: Capturing the Effects of Initial Permeability and Gas Pressure on Outburst-Prone Indicators

Coal and gas outbursts often result in a large number of casualties and economic losses. Its complex processes involve the multi-field coupling of gas flow, coal stress, and temperature variation. A coal temperature drop and an initial rate of the gas emission (qm) of boreholes are often used as indicators for the outburst-proneness of the heading face during the excavation of a coal roadway. However, the threshold values of these two indicators are empirical; few theoretic studies have been reported on their influence factors and laws. In order to investigate the influence laws of the initial gas pressure and permeability on these two indicators, a coupled thermal–hydraulic–mechanical (THM) model is proposed. This model considers the heat of absorption by gas from coal due to desorption and expansion. The presented THM model is verified using experimental data from the literature. Based on the verification of the model, the THM model is applied to a local prediction of outburst-proneness during the heading face advancement. The study indicates that the temperature drop and the qm both decrease as the initial permeability and gas pressure decrease; more specifically the relationship between the temperature drop and qm is a power function. The temperature drop of the borehole wall reduces with elapsed time, but the larger variation rate of the temperature drop occurs at the beginning of forming the borehole. Therefore, when temperature drop is adopted to indicate the outburst-proneness of heading faces, the temperature measurement moment needs to be pre-specified, a value of 20–30 min after borehole forming is recommended. Adopting the variation magnitude of qm during the advancement of the roadway heading face as an indication of coal and gas outburst-proneness may be more reasonable than qm itself. This study provides a reference for the prevention of coal and gas outbursts and a new idea for the application of a multi-field-coupled model of coalbed gas flow in practical engineering.

A new experimental apparatus for sudden unloading of gas-bearing coal

To study the characteristics of the deformation and failure of coal during a coal and gas outburst, we developed an experimental apparatus that subjected coal samples to sudden unloading under various gas conditions. The apparatus consisted of a coal sample cell, a fast pressure unloading system, a monitoring and control system, and a gas filling system. The gas filling system was equipped with safe, explosion-proof solenoid valves for gas pressure unloading and an accurate strain chip for measuring sample strain. The apparatus was designed to probe the influence of the gas on coal and gas outbursts. The study focused on the mechanism by which high-pressure gas influences coal and gas outbursts, leading to the deformation characteristics of the sudden unloading process. The experimental results showed that the plastic deformation of coal samples in the presence of methane gas can be divided into three stages: compression induced by increased pressure, expansion induced by adsorption, and deformation or failure induced by sudden unloading. The results of tests performed in the presence of helium revealed that the deformation could be divided into just two stages: a compression stage induced by increased pressure and a recovery stage induced by sudden pressure unloading. Coal samples were found to deform much more rapidly and to a greater degree in methane than in helium, and the expansive deformation and failure of the coal sample become increasingly apparent with increasing initial gas pressure. Overall, our results demonstrate that the experimental apparatus developed here provides a feasible means to test the characteristics of the coal damage and gas migration that occur during a coal and gas outburst.

Dynamic Compressive Test of Gas-Containing Coal Using a Modified Split Hopkinson Pressure Bar System

In deep mine, coal is usually subjected to coupled high gas pressure and static compressive stress. The coal may be also subjected to dynamic loading due to the sudden fracture of hard roof during mining. In our previous study, the behaviour of gas-containing coals with initial gas pressure was investigated subjected to uniaxial static compression. In this study, the dynamic compressive behaviour of gas-containing coals with gas pressure and static axial preloading is investigated using a modified Split Hopkinson Pressure Bar (SHPB) system. The dynamic behaviours of gas-containing coals under SHPB tests are studied by varying initial gas pressure and axial static preloading. The testing results include strain measurements and energy dissipation. In addition, the wave impedance method is used to quantify damage of gas-containing coals under coupled gas-static-dynamic load. It is found that the dynamic compressive strength of gas-containing coal under coupled load decreases with the increasing initial gas pressure. The gas-containing coal with higher gas pressure and axial static preloading is more vulnerable to dynamic loading. The findings can be applied to mining design or support design in deep mining of high-gas-containing coal seam.

NUMERICAL SIMULATION OF INITIAL PRESSURE EFFECT ON ENERGY INPUT IN SPARK DISCHARGE IN NITROGEN

An influence of initial gas pressure on energy deposited by spark discharge in nitrogen during the spark channel expansion is evaluated. Influence of the pressure on efficiency of energy deposition and emitted energy in a discharge channel is simulated. Dependencies of dynamic of energy input and an energy correlation coefficient on the pressure are found out. It was suggested to use an average value of the correlation coefficient to model a load of spark channel by the any initial pressure when a spark load is formed by atmospheric conditions.

Why Coal Bed Methane (CBM) Production in Some Basins is Difficult

The changes in the permeability of coal-bed reservoirs with methane, as associated with gas depletion, are the consequence of two opposing processes, namely geomechanical compaction that narrows down fractures, and matrix shrinkage, which, in turn, widens fractures. Many previous studies on the effects of these processes have emphasised, albeit not always, the circumstances and conditions that led to a greater coal permeability, with a natural decrease in the pore pressure of methane during its production, and, in consequence, to an increase in the cumulative volume of this gas. However, in some coal basins, there are beds where the methane production has failed to reach the appropriate level, whether in economic or engineering terms. This paper identifies some reasons for the failed attempts at well exploration of gas from such coal beds. Specifically, it describes seven parameters to be considered in relation to CBM, including geomechanical parameters such as Young’s modulus, Poisson’s ratio, and the initial porosity, which define coal cleat compressibility, a very important parameter, and parameters related to methane desorption, i.e., desorption-induced volumetric strain, the Langmuir pressure, and the initial pressure of gas within the bed. In addition to cleat compressibility, there are other, equally important parameters, such as the rebound pressure and recovery pressure, which are defined by the following parameters in order of importance: Young’s modulus, desorption-induced volumetric strain, initial pressure of methane, the Langmuir pressure, and Poisson’s ratio. To assess the impact of these parameters on changes in permeability, we used the Cui-Bastin model. The simulation results were analysed to allow us to present our findings.

The research of coal seam gas pressure and initial gas emission characteristics of borehole

AbstractGas pressure is one of the major factors to characterize the outburst danger of coal seams. Generally, the process of gas pressure determination is complicate and cannot ensure the accuracy of results, which may cause a wrong identification of outburst danger. This paper discussed and revealed a positive correlation between initial gas emission and gas pressure, which provides a new approach to identify the outburst danger by initial gas emission. Through theoretical analysis and numerical simulation, the liner equation of gas pressure and initial gas emission was deduced. Laboratory experiments under adsorption and desorption of CO2 and N2 were performed using coal samples from Weishe coal mine. The data of initial gas emission under different gas pressure were recorded, and the fitting curves were obtained. The results show a positive correlation between initial gas emission and gas pressure, and the curve of N2 was below the CO2. Especially, while the adsorption gas pressure was under 0.663 and 0.675 MPa, the difference of corresponding initial gas emission was only 0.01 L/s, which indicates the high degree of correlation. The results validated the theoretical and practical feasibility to identify the coal and the gas outbursts through initial gas emission.

Non-Embedded Ultrasonic Detection for Pressure Cores of Natural Methane Hydrate-Bearing Sediments

An apparatus for the analysis of pressure cores containing gas hydrates at in situ pressures was designed, and a series of experiments to determine the compressional wave response of hydrate-bearing sands were performed systematically in the laboratory. Considering the difficulties encountered in performing valid laboratory tests and in recovering intact hydrate bearing sediment samples, the laboratory approach enabled closer study than the marine environment due to sample recovery problems. The apparatus was designed to achieve in situ hydrate formation in bearing sediments and synchronous ultrasonic detection. The P-wave velocity measurements enabled quick and successive ultrasonic analysis of pressure cores. The factors influencing P-wave velocity (Vp), including hydrate saturation and formation methodology, were investigated. By controlling the initial water saturation and gas pressure, we conducted separate experiments for different hydrate saturation values ranging from 2% to 60%. The measured P-wave velocity varied from less than 1700 m/s to more than 3100 m/s in this saturation range. The hydrate saturation can be successfully predicted by a linear fitting of the attenuation (Q−1) to the hydrate saturation. This approach provided a new method for acoustic measurement of the hydrate saturation when the arrival time of the first wave cannot be directly distinguished. Our results demonstrated that the specially designed non-embedded ultrasonic detection apparatus could determine the hydrate saturation and occurrence patterns in pressure cores, which could assist further hydrate resource exploration and detailed core analyses.