Pressure Compensation Research Articles

Design and Experimental Study of Pressure Compensation System for Full-Ocean-Depth Gas-Tight Sediment Sampler

Aiming at the requirement of the full-ocean-depth (operating water depth 11000 m) manned submersible to carry out the gas-tight sampling operation of the abyss seabed sediment, a kind of full-ocean-depth carrier submersible mechanical hand-held, full-ocean-depth gas-tight sediment sampler (GTSS) with the function of pressure-retaining and coring is designed. Firstly, the volume change model of pressure compensator is established, and it is pointed out that the volume of pressure compensator is about 16.14% equal to the volume of gas-tight sediment sampler (GTSS). Secondly, the pressure compensator is analyzed and calculated, and the relationship between the precharge pressure of the pressure compensator, the nominal volume of the pressure compensator and the pressure holding effect of the gas-tight sediment sampler (GTSS) is studied. The results show that with the increase of gas precharge pressure in the pressure compensator, the final pressure of the sampler also increases. Under the same precharge pressure condition, the larger the nominal volume of the pressure compensator, the greater the final pressure of the sampler. Finally, the air tightness test method is designed by using the developed gas tightness sampler of the full-ocean-depth product, and the change of the final pressure in the gas tight sampler under different precharge pressure is observed. The test results are consistent with the simulation results, indicating the correctness of the pressure compensation system (PCS) model.

Energy Comparison between a Load Sensing System and Electro-Hydraulic Solutions Applied to a 9-Ton Excavator

With the increasingly stringent regulations on air quality and the consequent emission limits for internal combustion engines, researchers are concentrating on studying new solutions for improving efficiency and energy saving even in off-road mobile machines. To achieve this task, pump-controlled or displacement-controlled systems have inspired interest for applications in off-road working machines. Generally, these systems are derived from the union of a hydraulic machine coupled to an electric one to create compact components that could be installed near the actuator. The object of study of this work is a 9-ton excavator, whose hydraulic circuit is grounded on load sensing logic. The validated mathematical model, created previously in the Simcenter Amesim© environment, represents the starting point for developing electro-hydraulic solutions. Electric components have been inserted to create different architectures, both with open- and closed-circuit layouts, in order to compare the energy efficiency of the different configurations with respect to the traditional load sensing system. The simulations of a typical working cycle show the energy benefits of electro-hydraulic solutions that allow for drastically reducing the mechanical energy required by the diesel engine and, consequently, the fuel consumption. This is mainly possible because of the elimination of directional valves and pressure compensators, which are necessary in a load sensing circuit, but are also a source of great energy dissipations. The results show that closed-circuit solutions produce the greatest benefits, with higher energy efficiencies than the open-circuit solution. Furthermore, closed-circuit configurations require fewer components, allowing for more compact and lighter solutions, as well as being cheaper.

Лечение офтальмогипертензии у пациентов после витреоретинальной хирургии

Purpose. To evaluate the effectiveness of treatment of ophthalmic hypertension in patients after vitreoretinal surgery with various tamponade of the vitreal cavity. Material and methods. 344 case histories of patients aged 30 to 80 years who underwent vitreoretinal intervention for macular rupture, epiretinal membrane, hemophthalmos, retinal detachment with various tamponade of the vitreal cavity in the period from 2019 to 2021 were analyzed. To detect ophthalmohypertension, all the studied patients underwent tonometry before surgery and every month after during the entire follow-up period. The observation period was 2 years. Results. Of the 46 patients who were diagnosed with ophthalmohypertension after vitreoretinal surgery, 18 patients had intraocular pressure compensation during 2 years of follow-up, they did not require hypotensive therapy. 28 patients were prescribed hypotensive therapy (carbonic anhydrase inhibitors, α2-adrenomimetics), of which 4 patients had glaucoma before vitreoretinal intervention. 2 patients were implanted with an Express anti-glaucomatous device. Conclusion. The analysis of the effectiveness of treatment of ophthalmic hypertension in patients after vitreoretinal surgery showed that compensation of intraocular pressure occurs differently in each case, an individual approach is needed. One antihypertensive drug is not always enough, in some cases it is necessary to strengthen antihypertensive therapy, and sometimes anti-glaucoma surgical interventions. Keywords: vitreoretinal surgery, ophthalmohypertension, secondary glaucoma.

Working Performance of the Deep-Sea Valve-Controlled Hydraulic Cylinder System under Pressure-Dependent Viscosity Change and Hydrodynamic Effects

The valve-controlled hydraulic cylinder system (VCHCS) is commonly used for actuators such as manipulators in deep-sea equipment, whose working performance is crucial to subsea tasks. Affected by the ambient pressure introduced by the pressure compensator, the viscosity of the hydraulic oil increases significantly. On this basis, the viscosity changes further when flowing in the slender pipeline, making the pipeline pressure loss substantially increase and subsequently affecting the working performance of the deep-sea VCHCS. Aiming at this issue, a detailed nonlinear mathematical model of the deep-sea VCHCS is established, in which the viscosity-pressure characteristics of the hydraulic oil is considered to take the viscosity changes in the pipeline into account. Besides, the hydrodynamic effects are also included in the model. Then the corresponding numerical simulation model of the deep-sea VCHCS is established, and its working performance at different depths is simulated and analyzed. When the depth is 11km, the extension and retraction movements are delayed by 52.50% and 43.12% respectively. The root cause of the delay is then analyzed and discussed. Finally, the parameters that affect the working performance are studied, and suggestions to reduce or eliminate the delay phenomenon are given. The results can provide theoretical support for the performance optimization of the deep-sea VCHCS.

Collection sediment from Mariana Trench with a novel pressure-retaining sampler

Sediments in the hadal trenches have been proved to contain a large number of specific microorganisms. In this study, we developed a pressure-retaining sampler for the hadal trenches. A novel piston sampling mechanism was designed, the weight of which is light enough to be mounted on a lander for field tests. Furthermore, laboratory tests validated its high-pressure resistance and pressure-retaining performance. We tested the penetration force and the sampling performance in different clays. Moreover, a pressure compensator was designed based on the actual gas state under high pressure. Finally, a prototype of the sampler was built and field tested in the Mariana Trench. The results indicated that the sampler has an excellent pressure-retaining capacity and can collect sediment samples at the deepest point of the in the world's ocean.

Effect of the demethanizer improved control strategy on the separation train for the NGL separation process

In recent years the attention on natural gas production and utilization is growing due to different fundamental aspects. First, the availability of natural gas has increased thanks to technological improvements in the extraction techniques that have made possible the production from unconventional reservoirs. Second, the interest in clean energy is growing, aiming to reduce CO2 emission and thus global warming. Natural gas is a cleaner fossil fuel compared with other traditional energy sources such as oil and coal. Another reason that drives the attention on this fossil fuel is the increasing economic interest of recovering the heavier hydrocarbon fractions contained in it. The fractionation of natural gas liquids (NGL) is an energy-demanding process, often conducted with a separation train that includes cryogenic distillation columns. This work is intended to show how to achieve an energy-efficient recovery of NGLs with a proper control strategy and without composition analyzers. In particular, the effects of a combined cascade control with boilup approximation plus a pressure compensator control for the demethanizer section, on the desired NGL extraction product targets are investigated and compared under feed flowrate disturbances with conventional direct temperature controllers. Overall, it is shown that the cascade control plus pressure compensator provides the best performance and the lowest energy consumption.

ИССЛЕДОВАНИЕ ВЛИЯНИЯ ВИХРЕВЫХ ПОТОКОВ НА ЭЛЕМЕНТЫ ЯЭУ

The mechanisms of generation of stable large-scale eddies and flow swirling in complex channels of the 1st and 2nd circuits of transport nuclear power plants (NPP) are revealed. An analysis is given of the influence of vortex formation and flow swirling processes on failures in NPP systems. It is shown that with a complex geometry of the channels of the pipe systems of the thermohydraulic tract and the reactor plant (RP), the unauthorized swirl arising in certain dynamic modes can lead to the effect of blocking the flow caused by the swirl flow crisis. It has been established that the phenomenon of the crisis is accompanied by the generation of low-frequency acoustic vibrations and large pressure losses required to form a recirculation flow zone, which prevents the flow of fluids in complex channels of the nuclear power plant. In the presented work, the manifestation of a swirling flow crisis is considered by examples of modeling the processes of hydrodynamics and heat transfer in the channels of steam generators and the pressure compensation system of transport nuclear power plants. It is shown that the generation of stable vortex formations in the elements of the NPP equipment of the integral type can be directly related to the mechanism of excitation of hazardous vibroresonance effects. Methods for improving the design of pipe systems of steam generating plants are proposed to increase their thermal-hydraulic efficiency and vibration resistance.

A Variable Rate Drip Irrigation Prototype for Precision Irrigation

A new Variable Rate Drip Irrigation (VRDI) emitter that monitors individual water drops was designed, built, and tested. This new emitter controllers water application directly by monitoring the volume applied in contrast to uniform drip irrigation systems that control water application indirectly by pressure compensation and operational times. Prior approaches assumed irrigation volumes based on flow rates and time and typically did not verify the applied amount of water applied at each water outlet. The new VRDI emitter self-monitors the total volume of water applied and halts the flow once the desired total water application has been achieved. This study performed a test for a new VRDI emitter design with two inner diameters of 0.11 cm and 0.12 cm and two outer diameters 0.3 cm and 0.35 cm compared to a commercial drip emitter. Laboratory tests verify that the integrated volume measurements of the VRDI system are independent of pressure. Conversely, the flow rates of the commercial pressure-compensated drip lines were not independent of pressure. These results demonstrate that this form of VRDI is technically feasible and is shown to be energy efficient, requiring lower system operating pressures than pressure-compensated lines. The VRDI system can reduce water consumption and related water costs.

Modelling and pressure control of the expiratory cycle for mechanical ventilation systems

This study addresses the pressure control design of the expiratory cycle for mechanical ventilation systems. In particular, the study presented herein can be separated into two main stages: accurate system modelling, and suitable control design. Firstly, using generic modelling assumptions for pneumatic systems, the expiration dynamical model is presented and analysed. Secondly, a pressure tracking controller design, inspired by ‘traditional’ control structures, is proposed, considering both pressure and flow compensation combined with a gain-scheduling structure. Experimental results are presented throughout this study, both for modelling validation and controller implementation, using a commercial mechanical ventilation system. Such results show that the presented control strategy thoroughly verifies the specifications required by standard respiratory therapies, considering a broad range of patients features, in an extended dynamic range.

Simulation analysis of cooperative motion fuzzy control of distributed lifting units

In the technology of hydraulic lifting system, it is not only necessary to ensure that the displacement and velocity accuracy of each hoist reach a certain value, but also to ensure that under the control of load balance to make each hoist smooth lift. In the conventional method, the PID control method can realize the synchronization of the function. However, the system cannot be controlled and adjusted in real time during the control parameter period, resulting in instability and uncertainty of the system. Aiming at this problem, this paper adds the fuzzy adaptive controller to carry out the master-slave control of the system. AMESim and MATLAB co-simulation were used to model the overall model of the hydraulic system. At the same time, the pressure compensator and variable throttle port model in the hydraulic reservoir were selected to build. The pressure compensator is used to keep the pressure difference of the throttle orifice constant, so as to complete the control and design of the hydraulic lifting system. Finally, the simulation results obtained not only can effectively improve the instability of the hydraulic lifting process, but also greatly improve the operation speed of the system.

English

BACKGROUND Globally, radiodiagnosis is considered as one of the most sought after specialty in the field of medicine, based on the perceived notion that it is a high income, risk-averse, white-collared job. Radiologists are touted as being one of the highest paid specialists with defined work-hours; however, the ground reality appears to be in contradiction, particularly in the Indian context. The purpose of this study was to objectively assess the current day situation amongst the Indian radiologists. This gender-neutral survey not only dispels many of the prevailing assumptions but also brings to clear light the issues that assail the radiologist on a day to day basis. METHODS A cross-sectional descriptive study was performed with Google survey forms and collected data was obtained from 370 radiologists regarding various parameters, such as the workplace, years of experience, work hours per day, monthly income, peer, and work-related pressures, and their overall perceived happiness quotient. Issues concerning threats to radiology, the need for super or subspecialty training were also addressed. RESULTS Most of the young radiologists opted to work in either diagnostic centers or corporate hospitals as salary drawn was considerably higher than their counterparts in medical colleges. Nearly half the radiologists working at medical colleges augmented their income by working in diagnostic centers. Nearly 2/3rds of the young radiologists work for an average of 10 hours per day, six days a week with a take home salary of approximately 1 – 2 lakhs per month. Only 5 % of the radiologists stated that they were most happy with their work environment, nearly 57 % of them had some kind of occupational hazard and this was directly related to the years of work. Burn out predominated amongst the upcoming radiologists with less than 5 years of work experience and this was found to be compounded by work hours, work pressure and inadequate compensation. CONCLUSIONS Today, young radiologist is caught in a whirlpool of change that has not only threatened the “concept of a settled, satisfied, specialist”, furtherance to this, commoditization of radiology has led to increase in work hours, work pressure, leading to dissatisfaction and early burn out. KEY WORDS Radiologist, Psychosocial Aspects, Burn Out, Artificial Intelligence.

Research on back- pressure compensation characteristics of a pilot-assisted load control valve applied in overrunning load hydraulic systems

This paper reports the research of proportion flow control with back-pressure compensation feature on an LCV (load control valve). The back-pressure compensation feature means when back-pressure rises, flow of the LCV can be unchanged or lower. The back-pressure compensation feature is very important to the safety of the system, because high back-pressure will make the main valve open larger and lowering speed be undesired faster. In this paper, static equilibrium equations of LCV were established and influence relationship of back-pressure and other parameters was derived. In addition, back-pressure influence was simulated, based on above analysis a preliminary optimization scheme was proposed and tested. After that, the method of back-pressure compensation was proposed and has been verified by simulation. Finally, an LCV with back-pressure compensation feature was tested on the test rig. Experiment data validates that the main flow of the LCV with back-pressure compensation method was lower under a higher back-pressure and the pilot pressure control region was unchanged.

Dynamics and control of thermal- versus electrical-driven pressure-swing distillation to separate a minimum-boiling azeotrope

The implementations of heat integration (HI, thermal-driven), vapor recompression (VRC, electrical-driven), and self-heat recuperation (SHR, electrical-driven) in pressure-swing distillation (PSD) are available for providing energy saving and CO2 emission reduction over the conventional design (CONV, thermal-driven), exemplified by a minimum-boiling tetrahydrofuran/water. Approximately a 20 % decrease in total annual cost (TAC) and over 25 % CO2 emission reduction can be reached by using these measures. However, these steady-state advantages sometimes go along with decreases in controllability, so it is necessary to investigate the dynamics and control of these highly integrated and interacting processes. Robust temperature control structures based on decentralized proportional-integral (PI) feedback controllers are developed to tackle ± 20% disturbances in throughput and feed composition. For the thermal-driven processes, the PSD-CONV is easily controlled with the single-end control strategy. Based on that, the effective control of PSD-HI is achieved by either pressure compensation or bypass strategy. Regarding the complicated electrical-driven arrangements, the dynamic responses of PSD-VRC and PSD-SHR indicate their controllability is comparable to those of a regular sequence. These results demonstrate that there are no conflicts between the steady-state advantages and dynamic controllability for this specific separation. Meanwhile, these electrical-driven processes can be considered to extend to other minimum-boiling azeotropes owing to their economic and environmental advantages.

Combined treatment of post-thrombotic neovascular glaucoma (clinical case study)

PURPOSE. To present the features of the clinical course and evaluate the effectiveness of laser and surgical treatment of patients with neovascular glaucoma following central retinal vein thrombosis.MATERIALS AND METHODS. Two patients with neovascular glaucoma secondary to central retinal vein thrombosis were examined. Surgical interventions were performed: patient M. — micropulse cyclophotocoagulation (twice), intravitreal administration of an angiogenesis inhibitor (5 injections), retinal laser coagulation (two-stage); patient E. — micropulse cyclophotocoagulation, intravitreal administration of an angiogenesis inhibitor (2 injections), implantation of the Ahmed valve.RESULTS. The treatment resulted in compensation of intraocular pressure (IOP), improvement of visual functions, reduction of neovascularization in the structures of the anterior eye segment.CONCLUSION. Micropulse cyclophotocoagulation can be used in the complex treatment of neovascular glaucoma at any stage in order to reduce IOP and decrease the neovascularization in the iris and anterior chamber angle structures in the postoperative period.

Do positive stereotypes have a negative impact?

<p id="p00005">Positive stereotypes are defined as positive traits describing social groups. Previous research on stereotypes has mainly focused on negative stereotypes while overlooking positive stereotypes, especially their negative effects. Here, we will discuss positive and negative effects of positive stereotypes from racial, gender and aging stereotypes and conditions for their emergence and further future research. <p id="p00005">The positive effects of positive stereotypes are mainly evinced through the stereotype boost. For example, activation of positive racial stereotypes, positive gender stereotypes and positive aging stereotypes has a positive effect on targets’ minds and behaviors. The negative effects of positive stereotypes on targets’ behaviors and cognition are caused by the choking under pressure effect and compensation effect of social cognition, respectively. For example, targets with positive racial stereotypes have negative attitudes and evaluations towards the stereotyper. Targets are prone to underperform in stereotyped domains in positive gender stereotypes situation. As for positive aging stereotypes, the mental and psychical health of targets can be adversely affected. Generally, positive stereotypes still induce negative effect similar to negative stereotypes in certain conditions, although having the positive side. <p id="p00005">The effects (positive or negative) of positive stereotypes depend on the following four moderators: (1) Activation of positive stereotypes. Compared with the subtle activation of positive stereotypes, blatantly activating positive stereotypes easily cause the “choking under pressure” of targets and their sense of being depersonalized, finally resulting in a negative impact. (2) Accuracy of expressing positive stereotypes. Compared with accurately expressing positive stereotypes, the one who states positive stereotypes in an extreme way tends to generate the feeling of untruth, resulting in conflicted response of targets. (3) Individuals who state positive stereotypes. Compared with an ingroup member, positive stereotypes stated by an outgroup member easily cause the prejudice by targets, which then result in targets’ negative attitudes and evaluations towards the stereotyper. (4) Culture context of positive stereotypes. Compared with collectivistic culture, positive stereotypes in individualistic culture are prone to have a sense of being depersonalized and be thread. <p id="p00005">Further research on positive stereotypes can be discussed from the following aspects: (1) Exploration of effects of positive stereotypes in collectivistic culture. For example, China is the representative country of collectivistic cultures which emphasize “fundamental connectedness of human beings to each other”, and positive stereotypes as positive beliefs about members of social groups based on the category membership. Therefore, the Chinese feel less depersonalized when the stereotyper describe them in ways related positive stereotypes. (2) Exploration of positive stereotypes from research fields and targets, such as fields of sexual orientation and academic discipline. Academic discipline stereotypes deem that science students are superior to arts students in science, and arts students are superior to science students in arts. As a result, male science students may underperform on the science test and female arts students may underperform on the arts test when priming their major and gender identities simultaneously, due to the feeling of untruth present when activating two positive stereotypes. In addition, researchers can explore positive stereotypes of children as there are no stereotype awareness of children under 7 ages. That is one of the prerequisites for positive stereotypes having influence on targets. (3) Exploration of interventions of negative effects reduced by positive stereotypes. By far there is no research on the interventions of negative effects of positive stereotypes. However, it is not hard to assume that would be difficult to reduce the negative effects of positive stereotypes because of the complimentary nature of positive stereotypes. (4) Exploration of positive effects of negative stereotypes. Based on our knowledge, only two studies have found that negative stereotypes have positive consequences. Once more empirical evidence to support the findings can be confirmed, this would play a significant role in the domain of stereotype research, especially for the interventions of negative effects of stereotypes.

Conceptual design and selection of a bladder type pressure compensation system for subsea actuators to prevent failure due to seawater head

Conceptual design and selection of a bladder type pressure compensation system for subsea actuators to prevent failure due to seawater head

A Deep-Sea Sediment Sampling System: Design, Analysis and Experimental Verification

Abstract An airtight sampler with the function of holding pressure and coring was designed. First, using the sediment sampling test platform, taking high sampling rate as the goal and the motion speed of manipulator as the constraint condition, the sediment sampling rate (ratio of the sample retrieved by the sampling tube to the insertion depth of the sampling tube) test under different sampling tube inner diameters was carried out, respectively. Then, the pressure drop calculation and analysis of other components such as pressure retaining cylinder and sealing cylinder during the recovery of the airtight sampler to the deck are carried out, and the pressure drop compensation during the recovery of the airtight sampler is calculated and analyzed based on the pressure compensator. At last, the internal pressure test, high-pressure cabin test, and adaptability test between sampler and manipulator are carried out by using the developed prototype of an airtight sampler for sediments in the deep sea. The test results verify the feasibility of the design of an airtight sampler for sediments in the deep sea, which will provide strong support for the deep seabed sampling operation of the manned submersible in the deep sea.

Energy flow behavior and emission reduction of a turbo-charging and EGR non-road diesel engine equipped with DOC and DPF under NRTC (non-road transient cycle)

In the current study, the interaction between energy flow and aftertreatment is investigated by experiment to explore the energy distribution pattern changed by aftertreatment and the reversed impact on emission reduction. The temperature distribution, THC, CO/CO2, NOx and PN (particle number) emissions were measured in a non-road diesel engine with and without aftertreatment, DOC (diesel oxidation catalyst) and DPF (diesel particulate filter), under NRTC (non-road transient cycle) driving. With aftertreatment, the cooling loss is the main source for thermal efficiency reduction, a new concept “thermal delay effect” is proposed to explain this phenomenon. For emissions, overall CO and HC are almost reduced to zero through DOC, although CH4 conversion efficiency is only about 30%; NOx conversion efficiency is ~ 24.3%; and PN filtration efficiency is 99.99% through DPF. The engine meets the China national emission regulation even without aftertreatment except for PN, but PN decreases by five orders of magnitude through DPF. Finally, the emissions histories were analyzed in detail. The influencing factors were discussed thoroughly for original scenario. The exhaust temperature coupling with properties of catalytic converter were employed to analyze the aftertreatment’s performance and its impact patterns on pollutants. Under operation pattern of back pressure compensation, the average exhaust temperature (300 °C) under aftertreatment scenario increased by 6% relative to without aftertreatment, while during most time it did not exceed 350 °C at which the NOx conversion began to drop. Thus this operation made a good trade-off among reductions of various pollutants. Therefore, the energy distribution analysis must be from the view point of integration between engine body and whole exhaust system to be sure of clarification about aftertreatment’s behaviors.

Expression and Change of miRs 145, 221 and 222 in Hypertensive Subjects Treated with Enalapril, Losartan or Olmesartan

miR profile could be associated to CV risk, and also to prognosis/outcome in response to therapeutic approach. We aimed to evaluate if anti-hypertensive drugs enalapril, losartan or olmesartan have effects on monocyte miR profile in essential hypertensives without target organ involvement. For this purpose, 82 hypertensives and 49 controls were included; we evaluated SBP/DBP, lipid profile, glucose, CRP, fibrinogen, arterial stiffness indices (PWV; AIx), and cIMT at baseline (T0) and after 24 weeks of treatment (T1). Subjects with LDL-C ≥ 160 mg/dL, TG ≥ 200 mg/dL, BMI ≥ 30, and other additional CV risk factors were excluded. Patients who were prescribed to receive once-a-day enalapril 20 mg, losartan 100 mg or olmesartan 20 mg were eligible for the study. At T1, we found a significant improvement of SBP (−18.5%), DBP (−18%), HDL-C and LDL-C (+3% and −5.42%), glucose (−2.15%), BMI (−3.23%), fibrinogen (−11%), CRP (−17.5%,), AIx (−49.1%) PWV (−32.2%), and monocyte miR expression (miR-221: −28.4%; miR-222: −36%; miR-145: +41.7%) with respect to baseline. miR profile was compared to control subjects at baseline and at T1. We found some little difference in the behaviour of the three treatments on some variables: olmesartan was the most effective in reducing fibrinogen, DBP, CRP, and AIx (−13.1%, −19.3%, −21.4%, and −56.8%, respectively). Enalapril was the drug more significantly increasing the expression of miR-145. In conclusion, enalapril, losartan and olmesartan are effective in improving mechanical and humoral factors associated to AS and atherogenesis. These drugs appear to be able to modify miRs 221/222 and miR-145 expression in drug-naïve hypertensives, making it closer to that of control subjects; additionally, this provides a good blood pressure compensation, contributing to slow the progression of vascular damage.

Origin and distribution of an under-pressured tight sandstone reservoir: The Shaximiao Formation, Central Sichuan Basin

Abnormal pressure is of great significance for hydrocarbon generation, migration and accumulation. The tight gas reservoirs in the Middle Jurassic Shaximiao Formation of the Sichuan Basin are characterized by considerable underpressure, which origin and evolution are still unclear. In this study, the pressure distribution was characterized by repeat formation test and Bowers’ method using sonic and density well log data. The origins of underpressure were analysed by geological analysis and quantitative calculation. Basin modelling method was also applied for pressure evolutionary process reconstruction. The results showed that underpressure developed at depths of 1900–2300 m with pressure value of 9.24–17.19 MPa and the pressure coefficients of 0.45–0.89. Laterally, the pressure coefficient showed a decreasing tendency from the western to the eastern portion of the study area, which was characterized by considerable underpressure. The results of the underpressure origin analysis indicated that the elastic rebound and temperature reduction led to pressure reductions of approximately 12–15 and 3–4 MPa, respectively. However, the source rocks of Lower Jurassic Ziliujing Formation and Upper Triassic Xujiahe Formation provided pressure increasing by hydrocarbon generation as two of the main sources in the Sichuan Basin. The gas generating process in the source rocks of the Xujiahe Formation increased the pressure by more than 20 MPa which compensated for the pressure decrease in the western part of the Central Sichuan Basin. However, the gas generation of the Ziliujing Formation only provided less than 10 MPa of pressure compensation for the eastern part, which was then characterized by widely distributed underpressure. Consequently, the western and eastern portions of the Central Sichuan Basin underwent different pressure evolution processes, which lead to different pressure distributions at present. This study provided a basis for underpressure analysis of gas reservoirs in quality and quantity in the Central Sichuan Basin and may be helpful for similar gas fields worldwide.