Variable Pressure Research Articles

Pressure-Driven Batch Distillation Optimal Control for Acetone-Methanol Separation

Over the last fifteen years, immense progress has been made in the research of pressure-swing batch distillation. The challenge lies in the fact that certain pressure-sensitive azeotropic mixtures cannot be separated in a regular open batch mode with an acceptable outcome. Throughout most of this text, findings contradict previously established facts. The separation of acetone-methanol by pressure-swing batch distillation in a mixed double system, consisting of a regular and inverted column, is the process under investigation. In this work, a comprehensive global solution to the optimal control problem is derived in the form of a sequential synthesis of controlled trajectories. A thorough analysis of the control variables, with and without parametric sensitivity of manipulated variables, on the optimal control pattern with variable reflux is presented. Most authors did not achieve significant results by simultaneously optimizing reflux and liquid division ratios or by using a "variable pressure gap." This study challenges previous findings, emphasizing the importance of simultaneous optimization of all three factors mentioned. During this study, the optimal reflux strategy through cyclic operation was extended to optimize energy expenditure over a fixed time horizon. Moreover, the proposed scheme offers a high level of operational flexibility, allowing units to be operated independently or as a system. Additionally, the facility of connecting additional devices is highlighted by the significant difference in output temperatures and the potential for using evaporated fluids consecutively. Lastly, the research provides a solid basis for future investigations into internal and external heat integration, potentially leading to conclusions about expanding the network using well-known heat cycles.

Impact of Overpressure on the Preservation of Liquid Petroleum: Evidence from Fluid Inclusions in the Deep Reservoirs of the Tazhong Area, Tarim Basin, Western China

The complexity of petroleum phases in deep formations plays an important role in the evaluation of hydrocarbon resources. Pressure is considered to have a positive impact on the preservation of liquid oils, yet direct evidence for this phenomenon is lacking in the case of deep reservoirs due to late destruction. Here, we present fluid-inclusion assemblages from a deep reservoir in the Tazhong area of the Tarim Basin, northwestern China, which formed as a direct consequence of fluid pressure evolution. Based on thermodynamic measurements and simulations of the coexisting aqueous and petroleum inclusions in these assemblages, the history of petroleum activities was reconstructed. Our results show that all analyzed fluid-inclusion assemblages demonstrated variable pressure conditions in different charging stages, ranging from hydrostatic to overpressure (a pressure coefficient of up to 1.49). Sequential petroleum charging and partial oil cracking may have been the main contributors to overpressure. By comparing the phases of petroleum and fluid pressures in the two wells, ZS1 and ZS5, it can be inferred that overpressure inhibits oil cracking. Thus, overpressure exerts an important influence on the preservation of liquid hydrocarbon under high temperatures. Furthermore, our results reveal that the exploration potential for liquid petroleum is considerable in the deep reservoirs of the Tarim Basin.

Impact of variable hydrostatic pressure and intermittent operation on filtration performance and biofouling layer in gravity-driven membrane system for practical decentralized water supply

The gravity-driven membrane (GDM) systems offer a promising solution for decentralized drinking water supply due to its low maintenance and energy consumption. However, research on the practical application of GDM under variable hydrostatic pressure (variable load) and intermittent operation conditions, particularly in response to high-turbidity water, remains limited. This study investigates the long-term performance and characteristics of the biofouling layer of GDM under ultra-low variable hydrostatic pressure (20–60 mbar) and intermittent operation (8–12 h) conditions in practical decentralized water supply. The results indicate that the membrane flux (1.9–6.0 L∙m−2∙h−1, LMH) remained relatively stable despite variations in gravity-driven pressure (ΔP). Long-term operation of GDM can stably remove turbidity and potential pathogens from raw water. The total protein/polysaccharide ratios of extracellular polymeric substances (EPS) in the biofouling layer were below 0.50, reducing contaminant adhesion on the membrane surface. The 0.2–0.4 μm transparent exopolymer particles (TEP) fraction might be crucial for biofouling layer formation. The key species, belong to Proteobacteria and Patescibacteria, significantly alleviated membrane fouling by degrading polysaccharide and proteins in biofouling layer. Comammox Nitrospira were significantly enriched, contributing to efficient nitrification. GDM with variable load maintained a stable flux of 2.2–5.2 LMH under high-turbidity water conditions (300–1200 NTU), and simple forward flushing combined with sludge discharge can quickly restore ΔP. Overall, the variable load GDM system effectively manages membrane fouling and maintains stable filtration performance through the combined effects of variable load and intermittent operation, ensuring long-term and low-maintenance operation for decentralized water supply.

Variable frequency constant pressure water supply system based on Siemens S-1200

Abstract This paper presents the design of an efficient, cost-effective, and intelligent variable frequency water supply control system. The system consists of a PLC, frequency converters, water pumps, pressure sensors, and other components to form a closed-loop control system. It enables closed-loop control of water pressure, ensuring a dynamic balance between water consumption and water supply. A user-friendly HMI is designed based on a software platform for easy operation by management personnel. It allows for seamless switching of the system’s operating modes and the running status of water pumps. Real-time display of pump operation and monitoring of system performance are also provided. Compared to traditional water supply methods, this system exhibits superior reliability, speed, and performance. It is capable of meeting the daily water consumption needs of residents in high-rise buildings.

Effect of deposition parameters on structural and mechanical properties of Novel h-BN doped TiCrNbN coatings

In this paper, the novel h-BN doped TiCrNbN thin films was deposited on the DIN 1.2714 steel using closed field unbalanced magnetron sputtering (CFUBMS) technique with variable working pressure, bias voltage, and LaB6 target voltage. The main goal is to determine the contribution of degrees of these parameters on structural and mechanical properties using Analysis of Variance (ANOVA). The deposition parameters were leveled based on L9 (33) orthogonal Taguchi design method. Microstructural and thickness of coatings were investigated using SEM. The coatings had granular and flawless surface properties. The thickness of the coatings was determined in the range of 874 nm and 1.69 μm. The deposition parameter that has the highest contribution to coating thickness is working pressure. Hardness and adhesion strength of coatings were determined employing nanohardness and scratch tester, respectively. The highest hardness among the coatings was 24.67 GPa, obtained with the 3x10-3 Torr working pressure, 100 V bias voltage and 600 V LaB6 target voltage parameters. The deposition parameter that has the highest contribution to hardness is working pressure. The coating conditions with the highest hardness exhibited the highest adhesion strength. The superiority of the contribution of working pressure on the adhesion strength was prominent compared to other parameters.

Application of an energy recovery device with RO membrane for wave powered desalination

A Wave-Driven Desalination System (WDDS) represents an efficient method for harnessing wave energy to facilitate water desalination. Nonetheless, various challenges impede its path to commercial viability. There is a requirement to connect the WDDS to an Energy Recovery Device (ERD), but this is challenging due to the inherent variations in pressure and flow. This unique study demonstrates the working of a small scale WDDS system using a Spiral Wound Reverse Osmosis (SWRO) membrane with a permeate capacity of ∼2 m3/day. The study demonstrates the possibilities to reduce high specific energy consumption (SEC) in WDDS by incorporating a Clark pump as an ERD. The study is the first time an evaluation of an SWRO membrane and Clark pump in-the-loop has been evaluated using variable feed flow and pressure. The utilization of the Clark pump notably reduces SEC to about 3.5 kWh/m3, which is comparable to that of commercial desalination plants. Furthermore, the Clark pump aids in maintaining a consistent permeate recovery rate of 10 % under rectified sinusoidally varying flow conditions – representing the operating conditions more closely to that of practical devices.

Characterization of membrane pore size using statistical model by facile method of air bubbling in liquid media

Research has shown the correlation between porous membrane pore size and bubble formation including bubble size, frequency, and operating parameters. However, attempts to create a governing equation to establish this correlation have often suffered from low accuracy due to variable interactions. Therefore, it is necessary to identify the significant effects of membrane pore size on bubble formation to establish effective correlations. This study aimed to identify the significant effect of porous membrane pore size on bubble formation using analysis of variance (ANOVA) to establish a mathematical model that predicts porous membrane pore size using bubble formation. To achieve this, various porous membranes were fabricated by varying hydrophilic silica loadings. The resulting membranes were characterized regarding pore size and employed in an aeration device under variable air flow rates and inlet pressures to obtain bubble size and frequency data. JMP software developed a statistical model to characterize membrane pore sizes. The results show a significant effect of bubble formation information on pore size, with a p-value of 0.0089, R2 of 0.96, and root mean squared error (RMSE) value of 0.02. Validation of the model using three membranes demonstrated minor deviations of 0–6.5 %, emphasizing the model's effectiveness in predicting membrane pore size.

Optimal control for district heating systems based on imbalance analysis of pipe networks

In district heating (DH) systems, the transmission and distribution process occupy large amount of energy consumption. Hydraulic and thermal imbalance in pipe networks often lead to uneven heating, affecting user comfort and resulting in energy losses. To solve this problem, this study investigates the root causes of hydraulic and thermal imbalances in DH systems. Key factors have been identified such as initial flow rates, initial loads, and positions in the network of end-users. And the relationship between hydraulic and thermal imbalances have been analyzed. Building on this analysis, we further propose a novel strategy for differential pressure set-point adjustment. This strategy is developed based on a quantitative understanding of the flow rate changes and positions of end-users. It aims to rectify imbalances efficiently, thus enhancing the overall performance of the network. The effectiveness of the proposed strategy is validated through comparative analysis with the conventional constant differential pressure (CCDP) control strategy and an exist variable differential pressure (VDP) control strategy. Results demonstrate significant improvements in network performance, including enhanced stability and reduced energy losses. The proposed strategy reduces the average pressure difference in the main pipe by up to 10.9 %, improves the supply and return temperature difference by 10.9 %, and maintains valve openings above 70 % during peak periods. Additionally, it achieves 23.5 % energy savings in transmission and distribution, highlighting its potential to enhance system performance and efficiency. In addition, this strategy is more in line with the actual situation of end-user demand change for valve adjustment.

An All‐in‐One Wearable Device Integrating a Solid‐State Zinc‐Ion Battery and a Capacitive Pressure Sensor for Intelligent Health Monitoring

AbstractThis study introduces a novel wearable device that combines dual‐functional modules for energy storage and sensing. The device features an ionic gel serving as both the battery electrolyte and sensor dielectric layer, along with VO2‐nanoneedles electrodes. The solid‐state zinc‐ion battery module demonstrates a specific capacity of 286 mAh g−1, delivering consistent and long‐lasting power output even under variable pressure conditions. Moreover, the iontronic pressure sensor module exhibits high sensitivity, achieving 2.3 × 104 kPa−1, enabling precise detection of fingertip pulses and identification of respiratory patterns. The device's flexibility and structural resilience allow it to endure complex deformations, ensuring continuous operation in challenging environments. These results highlight the potential of the all‐in‐one device for wearable smart healthcare monitoring and management.

A Review of Machine Tool Motorized Spindle Variable Pressure Preload Technology Research

High-precision spindles are a vital study topic because of the growing demand for highspeed, high-precision, reliable, and long-lasting machine tools. Bearing preload is the primary means of improving the accuracy of the spindle rotor system. This study aims to summarize the research results, systematically analyze and evaluate the machine tool motorized spindle variable pressure preload technology, and provide a scientific basis for the practical application of the motor spindle variable pressure preload technology. This study is an in-depth analysis of the basic principles of the electric spindle preloading technology, the study of its influence mechanism on the thermal deformation, stiffness, slewing error, and life of the spindle system, and a discussion of the current shortcomings in the field of spindle preloading to provide a reference for the subsequent optimization. In the spindle system, the performance of rolling bearings and the design of bearing preload have an important impact on the spindle's accuracy and stability. The traditional preload method has yet to meet the requirements of modern high-speed machine tools. Real-time controllable preload has become the new direction of development, but the current preload technology still has certain limitations and needs to be further improved. In the future, the spindle bearing variable pressure preload technology will be more efficient and intelligent.

Dynamic Simulation Model and Performance Optimization of a Pressurized Pulsed Water Jet Device

Pulsed water jet technology has broad application prospects in the field of rock breaking. The pressurized pulsed water jet (PPWJ) is a new type of pulsed jet that offers high-amplitude pressurization, variable pulse pressure and frequency, and a high energy usage rate. To achieve a more destructive and powerful pulsed water jet, a dynamic simulation model of the device was established by using the AMESim software (v1400) based on the operational principle of PPWJs, and the simulation model was validated against the experimental results. The relationships between the key structural parameters of the PPWJ device and the pulse parameters were quantitatively investigated. The pulse pressure and frequency can be increased by appropriately increasing the nozzle diameter or boost ratio, and the pulse pressure will drop if the nozzle diameter or boost ratio exceeds a threshold value. Increasing the maximum displacement or action area of the piston will increase pulse length while decreasing pulse frequency; a proper match of the maximum displacement or action area of the piston will assure pulse peak pressure. The maximum outer diameter of the piston only affects the pulse frequency. The key structural parameters of the device were optimized on that foundation. Compared to the original device, the optimized device resulted in an increase in pulse frequency and jet output energy, leading to larger diameter and volume of erosion pits at the same stand-off distance and erosion time. The findings of this study offer valuable scientific insights for achieving efficient rock breaking with PPWJ.

Modeling Pressure Effect of Circular Tourniquet Based on Digital Arm

Background: This study aims to investigate displacement deformation of human tissue in the force region subjected to annular pressure. Methods: In this patent, 727 images of a Chinese digital human arm, captured from shoulder to fingertip, were used as the reconstruction data. The geometric entities of tissue structure were obtained after tissue segmentation, three-dimensional modeling, and reverse engineering to establish the working mechanism model of the tourniquet of the human forearm in the finite element simulation software (COMSOL Multiphysics 5.5). By setting different parameter models (tourniquet pressure and width models), we analyzed the force conduction mechanism and the displacement deformation mechanism of the viscoelastic and rigid tissues of the forearm when subjected to annular pressure. Results: Modeling analysis showed that when a pressure of 800 kPa was applied on a width of 40 mm, the annular pressure on the viscoelastic tissues was converted into displacement deformation, thus changing the tissue structure in the body and realizing the hemostatic effect of the tourniquet. In the case of fixed tourniquet width but variable tourniquet pressure, with the gradual increase of the pressure, displacement deformation showed an increasing trend. When the externally applied pressure was fixed and the tourniquet width was different, with the gradual increase of the tourniquet width, the displacement deformation showed a decreasing trend. Conclusion: This patent study demonstrates that both the amount of externally applied pressure and the width of the tourniquet affect the hemostatic effect of the tourniquet. The hemostatic effect on the damaged body will be more obvious under a small tourniquet width and large pressure.

A new insight into the oxygen reduction reaction of the Ca3Co4O9+δ/CGO composite air electrode

The calcium cobaltite Ca3Co4O9+δ (CCO) is an emerging electrode for Solid Oxide Fuel Cells or Solid Electrolyser Cells. Thanks to a thermal expansion coefficient which is in the same range of magnitude than the commonly used electrolytes, it should lead to improved durability. However, because the material suffers of a lack of oxide ion conductivity, it has to be used in composite with an ionic conductor. Displaying good compatability with ceria, first studies were carried out on composite with Ce0.9Gd0.1O1.95 (CGO). At 700 °C, an optimal Area Specific Resistance of 0.5 Ω cm2 was obtained for a 50/50 wt.% CCO/ CGO, 21 μm thick electrode, with CCO powder prepared by a solid-state route whose synthesis method led to large grains compared to the CGO powder. Here, to increase the density of triple-phase boundaries between the gas and the two materials, a CCO powder with smaller grain size was prepared using a citrate route. For screen printed 50/50 wt.% CCO (citrate)/CGO composite electrode deposited on symmetrical cell with a CGO electrolyte, an ASR of 0.35 Ω cm2 was achieved at 700 °C, under air. To go further in the understanding of the oxygen reduction reaction, the cell was then carefully studied at variable temperatures and under variable oxygen partial pressures, combining calculation of the distribution function of relaxation times (DFRT) and complex nonlinear least squares fitting (CNLS) of impedance spectra. At 700 °C, under air, it was shown that 55 % of the ASR was due to the oxygen molecule dissociation and diffusion of atomic oxygen species at the surface of the electrode materials. It was only 37 % at 600 °C. Experiment carried out under 21 % of oxygen in helium proved that gas diffusion was a limiting step at temperature higher that 650 °C whereas the redox of CCO was limiting at lower temperature. When deposited on a commercial anode supported 2R-Cell™ half cell, the maximum power density was improved by 284 %, reaching 532 mW/cm2 at 700 °C with a 50/50 wt.% CCO (citrate)/CGO composite air electrode against 187 mW/cm2 for a 50/50 wt.% CCO (solid-state)/CGO composite air electrode at the same temperature.

Research on variable pressure oil supply servo system based on accumulator

Research on variable pressure oil supply servo system based on accumulator

Multipressure Sampling for Improving the Performance of MOF-based Electronic Noses.

Metal-organic frameworks (MOFs) are a promising class of porous materials for the design of gas sensing arrays, which are often called electronic noses. Due to their chemical and structural tunability, MOFs are a highly diverse class of materials that align well with the similarly diverse class of volatile organic compounds (VOCs) of interest in many gas detection applications. In principle, by choosing the right combination of cross-sensitive MOFs, layered on appropriate signal transducers, one can design an array that yields detailed information about the composition of a complex gas mixture. However, despite the vast number of MOFs from which one can choose, gas sensing arrays that rely too heavily on distinct chemistries can be impractical from the cost and complexity perspective. On the other hand, it is difficult for small arrays to have the desired selectivity and sensitivity for challenging sensing applications, such as detecting weakly adsorbing gases with weak signals, or conversely, strongly adsorbing gases that readily saturate MOF pores. In this work, we employed gas adsorption simulations to explore the use of a variable pressure sensing array as a means of improving both sensitivity and selectivity as well as increasing the information content provided by each array. We studied nine different MOFs (HKUST-1, IRMOF-1, MgMOF-74, MOF-177, MOF-801, NU-100, NU-125, UiO-66, and ZIF-8) and four different gas mixtures, each containing nitrogen, oxygen, carbon dioxide, and exactly one of the hydrogen, methane, hydrogen sulfide, or benzene. We found that by lowering the pressure, we can limit the saturation of MOFs, and by raising the pressure, we can concentrate weakly adsorbing gases, in both cases, improving gas detection with the resulting arrays. In many cases, changing the system pressure yielded a better improvement in performance (as measured by the Kullback-Liebler divergence of gas composition probability distributions) than including additional MOFs. We thus demonstrated and quantified how sensing at multiple pressures can increase information content and cross-sensitivity in MOF-based arrays while limiting the number of unique materials needed in the device.

Unloading Technology and Application Research of Variable Diameter Drilling in Dynamic Pressure Roadway

Theoretical analysis and numerical simulation are used to study the influence of different parameters of variable diameter borehole pressure relief technology on the surrounding rock and support. A strain-softening model was established to analyze the intrinsic connection between the parameters of variable diameter boreholes and the evolution of surrounding rock stress, deformation law, and support strength. The results show that: (1) With the increase in shallow borehole diameter, it is easy to cause anchor de-anchoring phenomenon. (2) After the deep borehole diameter is more than 250 mm, it transfers the peak of the shallow vertical stress to the deep surrounding rock (about 16 m away from the coal wall). (3) If the position of the variable borehole aperture is set between the anchorage zone and the stress peak of the roadway, the stress transfer effect is better, and the influence and effective binding force on the surrounding rock is smaller. (4) When the spacing is 1.0 m~2.0 m, the vertical stress starts to transfer to the deep surrounding rock, the deformation of the surrounding rock is smaller, and the reduction in the effective binding force of the anchors is smaller. The result can provide a reference for similar production conditions.

Dynamic characteristic analysis and key parameter optimization of throttling orifice type air damping air spring

Abstract The unique hysteretic characteristic of rubber bellows and the nonlinear flow of internal airflow in the system results in the significant nonlinear dynamic characteristic of throttling orifice type air damping air springs (OADASs). To solve the problem of mathematical representation of dynamic characteristic and key parameters optimization of throttling OADAS, this paper comprehensively considers the hysteretic characteristic of rubber bellows under variable pressure, the nonlinear dynamic characteristic model and linear model of throttling OADAS are established based on the concepts of gas thermodynamics and fluid mechanics. The static and dynamic characteristic tests of the throttling OADAS are conducted, to verify the accuracy and effectiveness of the proposed model, and to reveal the influence laws of excitation amplitude, excitation frequency, and throttling orifice diameter on the quantitative characterization indexes. Finally, a complete throttling orifice diameter optimization method is proposed based on the eight-degree-of-freedom model of the entire vehicle. Optimization results illustrate that the RMS values of the vertical acceleration of the body and the vertical acceleration of the driver are decreased by 19.02% and 38.44%, respectively. Overall, the outcomes of this paper can provide the design idea and theoretical basis for air damping matching and active suspension control.

Harvest of transboundary grey wolves from Yellowstone National Park is largely additive

Abstract Large carnivores are globally threatened due to habitat fragmentation and loss, prey depletion and human exploitation. Human exploitation includes both legal and illegal hunting and trapping. Protected areas can create refugia from hunting and trapping; however, hunting can still threaten wide‐ranging large carnivores when they leave these areas. Large carnivore reintroductions to protected areas are often motivated to restore ecological processes, including wolf reintroduction to Yellowstone National Park (YNP). Determining if harvest is compensatory or additive is essential for informed conservation strategies, as it influences the overall impact on wolf populations and their ecosystems. If harvest was compensatory, then increasing harvest pressure outside YNP should not decrease overall survival for transboundary wolves. Alternatively, if increasing harvest was additive, then increasing harvest pressure outside YNP should decrease overall survival for transboundary wolves. We tested the effects of variable harvest pressure following delisting on the survival of YNP grey wolves (Canis lupus) from 1995 to 2022. We defined three harvest levels: no harvest, harvest with limited quotas and unlimited harvest. We used Cox‐proportional hazards models and cumulative incidence functions to estimate survival rates, factors affecting survival and cause‐specific mortality between these three harvest periods to test predictions of the additive mortality hypothesis. Most harvested wolves that primarily lived in YNP were killed adjacent to the park border. Cox‐proportional hazards models revealed that mortality was highest during years of unlimited harvest during winter outside YNP. Cause‐specific mortality analyses showed that natural mortality from other wolves and harvest were the two leading causes of death, but that harvest mortality had additive effects on wolf mortality. Wolf survival decreased with increased harvest mortality, while natural mortality remained relatively unchanged. Synthesis and applications. High rates of additive harvest mortality of wolves could negatively impact wolf survival in YNP. Harvest mortality of transboundary wolves is additive possibly due to source‐sink dynamics of uneven spatial susceptibility of wolves to harvest mortality across protected area borders, as well as effects of harvest on complex social dynamics of wolves in YNP. Transboundary management of large carnivores is challenging, yet cooperation between agencies is vital for wolf management in and around YNP. Our results support the use of small quota zones surrounding protected areas, that minimize transboundary mortality impacts on large carnivores living primarily inside protected areas.

Beyond Hypertension: Examining Variable Blood Pressure's Role in Cognition and Brain Structure.

Hypertension or high blood pressure (BP) is one of the 12 modifiable risk factors that contribute to 40% of dementia cases that could be delayed or prevented. Although hypertension is associated with cognitive decline and structural brain changes, less is known about the long-term association between variable BP and cognitive/brain changes. This study examined the relationship between variable BP and longitudinal cognitive, white matter hyperintensity (WMH), gray matter (GM), and white matter (WM) volume change over time and postmortem neuropathology. A total of 4,606 participants (32,776 follow-ups) from RADC Research Resource Sharing Hub (RUSH) and 2,114 participants (9,827 follow-ups) fromtheAlzheimer's Disease Neuroimaging Initiative (ADNI) were included. Participants were divided into 1 of 3 groups: normal, high, or variable BP. Linear-mixed models investigated the relationship between BP and cognition, brain structure, and neuropathology. Older adults with variable BP exhibited the highest rate of cognitive decline followed by high and then normal BP. Increased GM volume loss and WMH burden were also observed in variable compared to high and normal BP. In postmortem neuropathology, both variable and high BP had increased rates compared to normal BP. Results were consistent across the RUSH and ADNI participants, supporting the generalizability of the findings. Damages potentially associated with variable BP may reduce resilience to future dementia-related pathology and increased the risk of dementia more than that caused by high BP. Improved treatment and management of variable BP may help reduce cognitive decline in the older adult population.

Synchrotron vacuum ultraviolet photoionization mass spectrometry and modeling study of iso-octane low temperature oxidation at varied pressures

Because of its excellent anti-knock properties, iso-octane has been selected as the main component of gasoline surrogates, and a thorough understanding of its low temperature oxidation process is essential for the development of kinetic models. Although iso-octane has been studied for decades, a comprehensive understanding of its low temperature oxidation chemistry has not been realized, and kinetic models were not well developed. In this work, the previously developed, variable pressure jet-stirred reactor-synchrotron vacuum ultraviolet photoionization mass spectrometry system was used to study the low temperature oxidation of iso-octane at five bar, with an initial fuel mole fraction of 0.01, residence time of 2 s, and equivalence ratio of 0.25. Dozens of oxidation intermediates were qualitatively and quantitatively analyzed, helping to reveal the low temperature oxidation reaction processes of iso-octane and examine the kinetic models. Comparing iso-octane studies at high pressure in the literature, a highly detailed species pool was probed, which included H2O2, carbonyl acids, alkyl hydroperoxides, and keto-hydroperoxides (KHP). By combining the atmospheric pressure data in the literature, the recently developed model of iso-octane low temperature oxidation was examined. Further improvement of the kinetic model was achieved by carefully tuning the reaction rate constant of the KHP decomposition. Finally, according to the variation of mole fraction of products at different pressures, the pressure effects on key reaction pathways were discussed, and the selectivity of products at varied pressure conditions clarified.