Changes In Chamber Pressure Research Articles

Experimental Research on Thermal-Venting Characteristics of the Failure 280 Ah LiFePO4 Battery: Atmospheric Pressure Impacts and Safety Assessment

With the widespread application of lithium-ion batteries (LIBs) energy storage stations in high-altitude areas, the impact of ambient pressure on battery thermal runaway (TR) behavior and venting flow characteristics have aroused wide research attention. This paper conducts a lateral heating experiment on 280 Ah lithium iron phosphate batteries (LFPs) and proposes a method for testing battery internal pressure using an embedded pressure sensor. This paper analyzes the battery characteristic temperature, internal pressure, chamber pressure, and gas components under different chamber pressures. The experiment is carried out in a N2 atmosphere using a 1000 L insulated chamber. At 40 kPa, the battery experiences two instances of venting, with a corresponding peak in temperature on the battery’s side of 136.3 °C and 302.8 °C, and gas generation rates of 0.14 mol/s and 0.09 mol/s, respectively. The research results indicate that changes in chamber pressure significantly affect the center temperature of the battery side (Ts), the center temperature of the chamber (Tc), the opening time of the safety valve (topen), the triggering time of TR (tTR), the time difference (Δt), venting velocity, gas composition, and flammable limits. However, the internal pressure and gas content of the battery are apparently unaffected. Considering the TR characteristics mentioned above, a safety assessment method is proposed to evaluate the TR behavior and gas hazard of the battery. The results indicate that the risk at 40 kPa is much higher than the other three chamber pressures. This study provides theoretical references for the safe use and early warning of energy storage LIBs in high-altitude areas.

Experimental Study of Low-Thrust, End-Burning Solid Rocket Motors Including Plume Radiant Emission

Low-thrust, end-burning solid rocket motors have applications as propulsion systems for a class of small, transonic, uncrewed aerial vehicles. This paper provides new experimental measurements for characterizing small, low-thrust, end-burning motors. Four static fires measured the effects of motor chamber pressure and propellant oxamide content on exhaust plume radiant intensity, which could be important for vehicle visibility and tracking. Exhaust plume radiant intensity was found to be sensitive to a change in oxamide content and relatively insensitive to a change in chamber pressure for these motors. Thrust, chamber pressure, and burn rate were also measured for these motors, and a model for the minimum burn pressure of oxamide-doped propellants was improved.

Thermal Runaway Characteristics and Gas Analysis of LiNi0.9Co0.05Mn0.05O2 Batteries

Layered ternary materials with high nickel content are regarded as the most promising cathode materials for high-energy-density lithium-ion batteries, owing to their advantages of high capacity, low cost, and relatively good safety. However, as the nickel content increases in ternary layered materials, their thermal stability noticeably decreases. It is of paramount importance to explore the characteristics of thermal runaway for lithium-ion batteries. In this study, two high-nickel LiNi0.9Co0.05Mn0.05O2 batteries were laterally heated to thermal runaway in a sealed chamber filled with nitrogen to investigate the thermal characteristics and gas compositions. The temperature of the battery tabs was measured, revealing that both batteries were in a critical state of thermal runaway near 120 degrees Celsius. A quantitative analysis method was employed during the eruption process, dividing it into three stages: ultra-fast, fast, and slow; the corresponding durations for the two batteries were 3, 2, 27 s and 3, 3, 26 s. By comparing the changes in chamber pressure, it was observed that both batteries exhibited a similar continuous venting duration of 32 s. However, the pressure fluctuation ranges of the two samples were 99.5 and 68.2 kPa·m·s−1. Compared to the other sample, the 211 Ah sample exhibited larger chamber pressure fluctuations and reached higher peak pressures, indicating a higher risk of explosion. In the experimental phenomenon captured by a high-speed camera, it took only 1 s for the sample to transition from the opening of the safety valve to filling the experimental chamber with smoke. The battery with higher energy density exhibited more intense eruption during thermal runaway, resulting in more severe mass loss. The mass loss of the two samples is 73% and 64.87%. The electrolyte also reacted more completely, resulting in a reduced number of measured exhaust components. The main components of gaseous ejections are CO, CO2, H2, C2H4, and CH4. For the 211 Ah battery, the vented gases were mainly composed of CO (41.3%), CO2 (24.8%), H2 (21%), C2H4 (7.4%) and CH4 (3.9%), while those for the other 256 Ah battery were mainly CO (30.6%), CO2 (28.5%), H2 (21.7%), C2H4 (12.4%) and CH4 (5.8%). Comparatively, the higher-capacity battery produced more gases. The gas volumes, converted to standard conditions (0 °C, 101 kPa) and normalized, resulted in 1.985 L/Ah and 2.182 L/Ah, respectively. The results provide valuable guidance for the protection of large-capacity, high-energy-density battery systems. The quantitative analysis of the eruption process has provided assistance to fire alarm systems and firefighting strategies.

Fluid Dynamic Characteristics and Flow Distribution ‎Structure Optimization of Axial Piston Pump Considering ‎Cavitation Bubble Evolution

An axial piston pump can produce a serious cavitation phenomenon in the high- and low-pressure ‎transition process. Cavitation bubbles expand, compress, rebound and collapse when they enter the high-‎pressure oil drainage area. This affects the outlet flow ripple as well as the pressure pulsation of the ‎piston pump. However, the effect of the cavitation bubbles is ignored in the current outlet flow ripple ‎model of axial piston pumps. It affects the optimization design of the axial piston pump distribution area ‎structure parameters with the objective of reducing the pressure and flow rate. Therefore, a method of ‎optimizing the fluid dynamic characteristics and the flow distribution area structure parameters of an axial ‎piston pump considering the cavitation bubble evolution is proposed. A single-cavity dynamic model was ‎established to study the bubble evolution as the piston chamber pressure changes. According to the ‎cavitation cloud (group cavitation) characteristics of the axial piston pump, theoretical models of the ‎outlet flow ripple and the pressure pulsation of a piston pump were established considering the cavitation ‎bubble characteristics. The influence of cavitation characteristics on the outlet flow ripples and pressure ‎pulsation of the axial piston pump was analyzed and compared with that without cavitation. Comparison ‎with the experimental results, verified that the outlet flow ripple model becomes more accurate when ‎cavitation bubble characteristics are considered. Based on the multi-agent particle swarm optimization ‎‎(MAPSO) algorithm, an optimization model of the piston pump outlet flow ripple was established ‎considering the cavitation bubble characteristics. The optimized design parameters for the flow ‎distribution area of the axial piston pump were evaluated. The proposed method can provide theoretical ‎guidance for the design of a low flow ripple axial piston pump.‎

Mathematical Model and Simulation Analysis of a New Underwater Launching System

In order to solve the problems of air turbines about complex structure, difficult processing and material requirements, a new type of vaneless underwater launch prime mover scheme is proposed. After simplification and assumption of working conditions, the launching system of the prime mover and pump is modeled and simulated by matlab. The results show that the change of chamber pressure in launcher tube is reasonable, the head and the flow of the pump is enough to provide the power for pushing the torpedo, and the other parameters such as power and speed of the prime mover scheme meet the requirements of each index, which provides theoretical support for practical application.

Dynamic vacuum pressure tracking control with high-speed on-off valves

A vacuum pressure tracking system with high-speed on-off valves is a discontinuous system due to the discrete nature of high-speed on-off valves. Chamber pressure changes in the system are determined by the mass flow rates during the processes of charging and discharging. Here, a sliding mode controller with an asymmetric compensator based on average mass flow rate is designed for accurate vacuum pressure tracking. The controller output signal is converted into the duty cycles of the high-speed on-off valves via a pulse width modulation pulsing scheme. Owing to the extreme asymmetry of the processes, an asymmetric structure comprising one high-speed on-off valve in the charging unit and three high-speed on-off valves in the discharging unit is applied to weaken the impact of asymmetry. In addition, an asymmetric compensator is also designed to modify the pulse width modulation pulsing scheme to further eliminate the asymmetry. Experimental results indicate that the proposed controller achieves better performance in pressure tracking with the asymmetric compensator overcoming process asymmetry and enhancing system robustness.

Freeze‐drying of ceftriaxone sodium solution frozen with prefabricated porosity

Initially unsaturated material frozen with prefabricated porosity was prepared to experimentally investigate its effect on freeze‐drying of liquid material. Ceftriaxone sodium, a kind of commonly used antibiotic, was selected as the primary solute in an aqueous solution. The liquid nitrogen ice cream‐making method was employed to prepare frozen materials with different initial porosities. Results showed that freeze‐drying was significantly enhanced with the initially unsaturated frozen material and substantial drying time was saved compared with conventional freeze‐drying. Drying time for the unsaturated sample (0.3 of saturation or 0.67 of initial porosity) was more than 20 % shorter than that required for the saturated one (1.0 of saturation without initial porosity). SEM images displayed that the dried products of the unsaturated frozen material had a pierced solid skeleton and uniform pore space with a fine and tenuous structure compared with those of the saturated one. The freezing rate exhibited little influence on the freeze‐drying process. Annealing can be moderately beneficial to shortening the drying time and further improving the energy utilization. An appropriate increase in operating temperature was able to enhance the freeze‐drying rate while changes in chamber pressure had a negligible effect on the process.

Kevlar/EPDM 내열고무의 압력 변화에 따른 열반응 비교

Kevlar/EPDM 내열고무의 압력 변화에 따른 열반응 비교

Efficient Thrust Distribution with Adaptive Pressure Control for Multinozzle Solid Propulsion System

An integrated approach for chamber pressure control and thrust distribution for multiple nozzles of a solid propulsion system is presented. In this study, a solid propulsion system with variable nozzle throat area controlled by a pintle actuator is considered. To keep the hardware configuration simple and lightweight, multiple nozzles share a combustion chamber. Consequently, changing the throat area of one nozzle results in an unintended change of chamber pressure and thrust from other nozzles. Therefore, pressure stabilization and thrust distribution for multiple nozzles should be conducted simultaneously to achieve the desired performance. For the inner control loop, an adaptive sliding mode controller with feedback linearization is used for pressure stabilization. With the pressure control loop working properly, a thrust distribution algorithm into 10 nozzles for translation and attitude maneuver is developed as an outer control loop.

Manipulation of intraocular pressure for studying the effects on accommodation

A reliable experimental system in which IOP can be manipulated or a rapid IOP change can be induced while simultaneously and continuously measuring IOP and the ocular accommodative changes would be useful for understanding the physiological effect of intraocular pressure (IOP) on the accommodative mechanism. In this study, an IOP perfusion and recording system was developed and tested using 13 enucleated pig eyes. The vitreous chamber of the pig eyes was cannulated with a needle connected to two fluid reservoirs at different heights. One reservoir was set to achieve one of three baseline pressures of 5.5 mmHg, 13.0 mmHg and 20.5 mmHg. The other reservoir was moved to achieve pressures of 1.5 mmHg, 3.0 mmHg, 4.5 mmHg and 6.0 mmHg higher than the baseline pressure. The height differential between the reservoirs determined the amplitude of IOP changes. Rapid IOP changes were induced by switching the reservoirs with a solenoid pinch-valve. Two needles, one each attached to a pressure transducer were inserted into the anterior chamber and vitreous chamber respectively. Custom developed software was used to measure the anterior chamber pressure and vitreous chamber pressure at 80 Hz. A high-resolution continuous A-scan ultrasound biometer (CUB) was used to dynamically measure changes in ocular biometry including anterior chamber depth (ACD), lens thickness (LT) and vitreous chamber depth (VCD) while the vitreous chamber pressure was manipulated. The changes in ACD, LT and VCD were analyzed as a function of the pressure change. Perfusion-induced axial biometric changes were quantified by the slopes of linear regression relationships. Both anterior chamber pressure and vitreous chamber pressure changed relatively systematically with the induced vitreous chamber pressure changes (anterior chamber: y = 0.863x + 0.030, r2 = 0.983; vitreous chamber: y = 0.883x + 0.009, r2 = 0.981). At perfusion pressures of 5.5, 13.0 and 20.5 mmHg, the slopes for ACD were −5.72, −2.75 and −2.36 μm/mmHg, for LT were −3.31, −1.59 and −1.03 μm/mmHg and for VCD were 19.05, 8.63 and 5.18 μm/mmHg. The system was able to manipulate and monitor IOP while axial biometry changes were recorded. This system will allow the relationship between IOP and accommodation to be studied in non-human primate eyes.

Effects of initial droplet diameter and pressure on burning of ATF gel propellant droplets

The increasing demand for higher energy density fuels and the ever-increasing concern for their safety have propelled research in the field of gel propellants. For studying the fundamental parameters without the interference of neighbouring droplets, isolated droplet burning of organic ATF (aviation turbine fuel) gel propellants was chosen to investigate experimentally the effects of initial droplet diameter and chamber pressure on the burning under normal gravity conditions at room temperature. Under ambient pressure condition, an increase in the burning rate constant was observed with increase in initial droplet diameter. For a given range of diameters, the burning rate constant also continued to increase with pressure. Experiments were also carried out to study how these variations were affected by initial droplet diameter and chamber pressure changes, respectively. The intensity of microexplosions was observed to decrease with increase in chamber pressure. A balance between the heat loss by the droplet to the surroundings and the heat gain by the droplet has been put forward to explain the variations of burning rate constant with varying pressures as well as varying initial droplet diameters.

Simultaneous Water Uptake, Diffusivity and Permeability Measurement of Perfluorinated Sulfonic Acid Polymer Electrolyte Membranes

Water diffusivity in perfluorinated sulfonic acid polymer exchange membranes (PEMs) is tested using two new methods. In the first "static" method the membrane is placed in a water activity gradient in a previously evacuated chamber to eliminate all gas/gas diffusion. In a second "dynamic" method the membrane is placed in an evacuated chamber, and known quantities of water vapor are added to the chamber. Diffusivity and water uptake are calculated by monitoring the change in chamber pressure. Rates of diffusivity were found to be identical regardless of method, or if the membrane was undergoing adsorption or desorption.

Transient effects of magma ascent dynamics along a geometrically variable dome-feeding conduit

The transient dynamics of magma ascent during dome-forming eruptions were investigated and the effects of magma chamber pressure perturbations on eruption rate are illustrated. The numerical model DOMEFLOW, developed by the authors for this work, is applied to the problem. DOMEFLOW is a transient 1.5D isothermal two-phase flow model of magma ascent through an axisymmetric conduit of variable radius, which accounts for gas exsolution, bubble growth, crystallization induced by degassing, permeable gas loss through overlying magma and through conduit walls, as well as viscosity changes due to crystallization and degassing. For runs in which chamber pressure increases, the time required to reach the new steady state (transition time) is a complex function of the pressure perturbation, while for decreasing chamber pressure, transition time is a monotonic function of the magnitude of the pressure perturbation. The transition to the new steady state is mainly controlled by magma compressibility, travel time (time required for one parcel of magma to travel from chamber to surface), and the time over which the pressure perturbation occurs. Results of many runs (> 300) were analyzed using dimensional analysis to reveal a general relationship which predicts the temporal evolution of magma effusion rate for a given sudden increase in chamber pressure; the product of the change in steady-state extrusion rate and the time required to reach the new steady state is linearly proportional to the normalized change in chamber pressure, the volume of the conduit, and the ratio of top and bottom conduit radii, and inversely proportional to the cubic root of volatile fraction. This relationship is used to interpret observed variations in two ongoing dome-building eruptions, the Soufrière Hills volcano, Montserrat, and Merapi volcano, Indonesia.

Simultaneous Voltammetric Determination of Zn, Cd and Pb at Bismuth Nanopowder Electrodes with Various Particle Size Distributions

AbstractEffect of particle size distribution on sensor characteristics of nano‐Bi fixed electrode has been investigated using square wave anodic stripping voltammetry. Bi nanopowders with various particle size distributions were synthesized by gas condensation (GC) method with the change of chamber pressure. As the chamber pressure decreased, the size of Bi nanopowder became smaller with narrower distribution due to a shorter residence time of Bi vapor. The square wave anodic stripping voltammograms (SWASV) showed well‐defined and highly reproducible peaks at −1.2 V, −0.8 V and −0.6 V (vs. SCE), which are closely related to the oxidation of Zn, Cd and Pb, respectively. The sensitivity and detection limit of the nano‐Bi fixed electrode were quantitatively estimated from the analyses of SWASV. From the results, it is concluded that as the size of Bi nanopowder becomes smaller with narrower particle size distribution, the sensitivity and detection limit of sensor electrode for Zn, Cd and Pb are improved, which is ascribed to the increase in electrochemical‐active surface area.

Effects of conduit geometry on magma ascent dynamics in dome-forming eruptions

We develop a steady-state, two-phase flow model of magma ascent through an axisymmetric conduit of variable radius R and length L in order to quantify relationships between conduit geometry and magma ascent dynamics. Holding boundary conditions and chamber magma properties constant, we vary conduit geometry systematically and independently, such that the upper conduit radius increases or decreases by a factor of R t / R b (radius ratio; 0.4 ≤ R t / R b ≤ 2.5), above a change initiation height H (0.1 ≤ H/ L ≤ 0.7), and over length L e ( L e / L = 0.2), where R t and R b are conduit radius above ( t) and below ( b) the radius change and H is the height above the top of the magma chamber. Conduit widening causes a drop in overpressure and corresponding increase in gas volume fraction and magma acceleration over the whole length of the conduit, with all changes increasing in magnitude with increasing radius ratio. Magma ascent rate increases roughly as R 2 and volumetric flow rate subsequently increases as R 4 when R t = R b = R. Both increasing R t for a fixed R b (increasing radius ratio) and increasing R b for a fixed R t (decreasing radius ratio), increase volume flow and magma ascent rates. Compared to changes in geometry, small changes in chamber pressure (< 5%) have a weak effect on flow rate. Many model runs produce a magma plug at the top of the conduit, largely due to permeable gas loss through conduit walls. In general, large radii and low radius ratios (i.e., nearly cylindrical conduits) favor thin, low-density plugs, which may facilitate sudden destruction of a plug, and thus enhance the likelihood of explosive over extrusive eruptions. These findings suggest that changes in conduit geometry, such as those caused by conduit erosion during explosive eruptions or by accretion of magma along conduit walls, are strongly coupled to magma ascent dynamics and should not be ignored when interpreting changes in eruptive behavior.

Dynamics of magma ascent and lava extrusion at Soufrière Hills Volcano, Montserrat

Abstract Growth of the andesitic lava dome during eruption of Soufrière Hills Volcano, Montserrat involved general increases in discharge rate and dome height with superposed fluctuations on timescales from hours to months. We have modelled magma conduit flow incorporating viscosity variations caused by degassing and crystallization. Gas loss is modelled by permeable flow, with variations of permeability constrained by measurements. Crystallization kinetics is modelled by an Avrami law. Observations and petrological studies constrain conduit diameter ( c . 30 m), magma chamber crystal content ( c . 60-65%), melt water content ( c . 5%), magma temperature ( c . 850°C) and chamber depth ( c . 5 km). Gas loss and rheological stiffening cause a maximum in magma overpressure (magma pressure minus lithostatic pressure) at depths of a few hundred metres below the dome. This maximum can explain ground deformation patterns, shallow seismicity, and short-lived Vulcanian explosions. Crystallization kinetics causes a strong feedback mechanism and multiple steady solutions for discharge rate. Small changes in chamber pressure, magma viscosity and conduit diameter strongly amplify discharge rate. Multiple solutions allow cyclic variation of discharge rate. Escalation of activity is attributed principally to influx of hot mafic magma into the chamber, resulting in chamber pressure increasing with time. Dome growth can be intrinsically unpredictable due to non-linear effects.

On the barometric method for measurements of ventilation, and its use in small animals

The barometric method is a common technique for measurements of pulmonary ventilation in unrestrained animals. It basically consists of recording the changes in chamber pressure generated during breathing. In fact, as the air inspired is warmed and humidified from the ambient to the pulmonary values, the total pressure in the animal chamber increases; the opposite occurs in expiration. The present commentary is an introduction to this method, briefly reviewing its historical development, the conceptual pitfalls, and potential sources of errors during practical applications.Key words: barometric technique, plethysmography, pulmonary ventilation, respiratory techniques, tidal volume.

On the barometric method for measurements of ventilation, and its use in small animals

The barometric method is a common technique for measurements of pulmonary ventilation in unrestrained animals. It basically consists of recording the changes in chamber pressure generated during breathing. In fact, as the air inspired is warmed and humidified from the ambient to the pulmonary values, the total pressure in the animal chamber increases; the opposite occurs in expiration. The present commentary is an introduction to this method, briefly reviewing its historical development, the conceptual pitfalls, and potential sources of errors during practical applications.

Spatial density distributions of C2, C3, and CH radicals by laser-induced fluorescence in a diamond depositing dc-arcjet

Quantitative measurements of C2(a3Πu), C3(X,1Π), and CH(X,2Π) have been made by calibrated linear laser-induced fluorescence in the plume of a dc-arcjet (Ar/H2/CH4 1.1:1:0.005) reactor during the chemical vapor deposition of diamond. The peak number density in the arcjet plume for CH is (3.7±0.8)×1012 molecules/cm3, for C2(3a)(3.1±1.3)×1010 cm−3, and for C3∼3×1012 cm−3 with 25 Torr reactor pressure. The radial spatial distributions for C2 and CH have a maximum in the center of the plume; however, C3 is distributed as a hollow cylinder with a pronounced minimum at the center. The variation in number density and in spatial distribution is investigated for changes in chamber pressure, methane flow, and distance from the nozzle.

Effect of External Chest Wall Oscillation on Gas Exchange in Healthy Subjects

Effective gas exchange can be maintained in animals without the need for endotracheal intubation using external chest wall oscillation (ECWO). The clinical application of this technique has been limited by equipment which was either impractical or uncomfortable. We evaluated a prototype of a new oscillator in which an oscillatory profile of negative and positive pressure was imposed on a negative baseline pressure within a cuirass. In seven healthy subjects, we identified an oscillatory cuirass pressure that could effectively ventilate but would not result in severe hypocapnia over 5 min. We then measured the influence of changing the frequency of oscillation (fo) on PaCO2 and spontaneous ventilation. Lastly, we evaluated the capability of this prototype to achieve targeted changes in chamber pressure. Subjects were ventilated with an inspiratory chamber pressure of -20 +/- 4 cm H2O, an expiratory chamber pressure of 5 cm H2O and an inspiratory-expiratory ratio of 1:1 at 9 oscillatory frequencies (fo: 1 to 5 Hz at 0.5-Hz increments). Each subject was ventilated for 5 min with consecutive periods of ECWO being separated from each other by 10 min of unassisted breathing. Oscillatory tidal volume (Vo) was sampled and PaCO2 was determined from the expired carbon dioxide concentration (FECO2) measured at the mouth. The change in PaCO2 (delta PaCO2) was the difference in PaCO2 immediately before and after ECWO. We found that delta PaCO2 and Vo were inversely related to fo. At 1 Hz the delta PaCO2 was -13 +/- 1 mm Hg and Vo was 344 +/- 34 mL in the absence of spontaneous breathing (fb = 0). At 3 Hz and above, at the chamber pressures used, the delta PaCO2 was small (-1 to -2 mm Hg) and the Vo was less than the predicted dead space. Subjects breathed spontaneously but at a frequency below that of their resting fb. With this prototype, chamber pressure changes up to 30 cm H2O could be accurately achieved at 1, 2.5, and 4 Hz. In conclusion, ECWO can provide effective ventilation among healthy adults in the presence or absence of spontaneous breathing, and further studies are warranted to explore its effectiveness in a variety of clinical circumstances.