Low Suction Pressure Research Articles

Comparison of efficacy and safety of different suction pressure for speeding non-ventilated lung collapse in uniport video-assisted thoracoscopic surgery: a randomized-controlled trial

BackgroundThe bronchial suction has been applied in speeding lung collapse. Low suction pressure may not speed lung collapse, but high pressure causes occult lung injury. The aim of the study was to explore efficacy and safety of different suction pressure for speeding lung collapse.MethodsEighty-four subjects undergoing uniport video-assisted thoracoscopic surgery (VATS) were randomly assigned for non-suction (Group 0), -10 cmH2O suction pressure (Group − 10), and − 30 cmH2O suction pressure (Group − 30). The primary outcome were the lung collapse scores (LCS) at 0 min (T0) after the visualization of the lung using a 10-point visual analogue scale and area under the curve (AUC) of LCS over time. The secondary outcomes included disconnection from the ventilator, the assessment of occult lung injury using NOS-3 expression, histologic scores of lung injury, and lung W/D weight ratio, intraoperative hypoxemia, the incidence of perioperative pulmonary complications.ResultsBoth the LCS at T0 and AUC analysis showed that compared with Group 0, Group − 10 and Group − 30 significantly achieved good lung collapse (P < 0.05), but no difference between Group − 10 and Group − 30. Four patients in Group 0 were treated with disconnection maneuver. The assessment of occult lung injury showed no differences.ConclusionsApplying − 10 cmH2O suction pressure for 1 min when pleural incision is a relatively safe method to promote lung collapse without the occurrence of occult lung injury.Trial registrationChinese Clinical Trial Registry number, ChiCTR2200062991. Registered on 26/08/2022.

Dynamic modeling and characteristics analysis of sliding vane in a high-speed rotary compressor considering groove distribution and multi-body coupling

As one significant component in high-speed rotary compressors, sliding vane undergoes complex motions within the vane slot. The requirements for high-performance compressors result in the applications of low-viscosity lubrication techniques and high working frequency, thus worsening the operation conditions of the vane. To investigate the service performance of the sliding vane, a new tribo-dynamic model considering groove distribution and multi-body coupling is established in this study. Based on the solution with the modified extended backward differentiation formulae (MEBDF), the tribo-dynamic behaviors of the vane-related friction pairs are revealed. After comparison, the optimal scheme of the vane width is determined as 3.188 mm, with which the maximum wear load of the vane slot on the suction side is reduced obviously and the wear volume changes little. With the conical structure scheme of Lcs=1.5mm and hcs=1μm, the maximum wear load of the vane slot can be greatly reduced, thus increasing the wear uniformity. To improve the operation performance of the vane-slot conjunction, the lower suction pressure is suggested. This work provides comprehensive information for manufacturers to understand the working state of the sliding vane and conduct the optimal design.

Simulation and experimental study on dynamic characteristics of R290 split heat pump during start-up

As a new generation of heat pump refrigerant, R290 (propane) not only has advantages in environmental protection, but also has the good performance. However, reliability problems remain in the start-up process of R290 heat pumps, and hence it is necessary to study the dynamic characteristics of the start-up process. This paper establishes a mathematical model based on the physical properties of R290 and the system characteristics of R290 split heat pumps. The model is used to calculate the dynamic start-up characteristics. The proposed mathematical model is validated by experiments, and an error analysis of the heating start-up is carried out, and the mechanism of continuous low suction pressure during start-up is analysed. Taking a variable frequency rated heating condition as an example (indoor and outdoor temperature 20/7 ℃), the maximum deviation between the calculated pressure and the experimental value is within 5% during stable process. The refrigerant mass in the compressor shell is 164.76 g at most and the liquid separation process lasts 370 s during heating start-up process. The continuous suction of low pressure in the R290 split heat pump is attributed to the accumulation of liquid phase refrigerants in the accumulator and the presence of refrigerant condensation in the compressor shell.

Probabilistic Analysis of Highly Nonlinear Models by Adaptive Sparse Polynomial Chaos: Transient Infiltration in Unsaturated Soil

Polynomial chaos expansion (PCE) is widely adopted in geotechnical engineering as a surrogate model for probabilistic analysis. However, the traditional low-order PCE may be unfeasible for unsaturated transient-state models due to the high nonlinearity. In this study, a temporal-spatial surrogate model of adaptive sparse polynomial chaos expansions (AS-PCE) is established based on hyperbolic truncation with stepwise regression as surrogate models to improve computational efficiency. The uncertainty of pore water pressure of an unsaturated slope under transient-state rainfall infiltration considering hydraulic spatial variability is studied. The saturated coefficient of permeability [Formula: see text] is chosen to be spatial variability to account for the soil hydraulic uncertainty. The effects of location and time and the performances of AS-PCE are investigated. As rainfall goes on, the range of the pore pressure head becomes larger and the spatial variability of [Formula: see text] has little influence in the unsaturated zone with high matric suction. The pore pressure head under the water table suffers more uncertainty than it in the unsaturated zone. The [Formula: see text] in the high matric suction zone has a trend of rising first and then falling. Except for the high matric suction zone, the [Formula: see text] rise over time and they are almost 1 at the end of the time. It can be concluded that the AS-PCE performs better for low matric suction and positive pore pressure head and the fitting effect gradually increases as the rainfall progresses. The quartiles and at least up to second statistical moments can be characterized by the AS-PCE for transient infiltration in unsaturated soil slopes under rainfall.

Investigations on the coupling principle of the four-stage DC linear compressor unit used in a hybrid cryocooler operating in 1–2 K

In a hybrid cryocooler developed for operating in 1–2 K, a four-stage DC linear compressor (DCLC) unit used in a Joule-Thomson cooler (JTC) is designed to provide the extremely low suction pressure of below 3.1 kPa. An equivalent non-linear dynamic model is proposed to analyze the gas spring force within the cylinder, and the coupling principles among stages of the DCLC unit are analyzed and summarized for the optimal design. In a standalone test platform, the experimental results show that the designed four-stage DCLC unit can provide a suction pressure of 2.1 kPa, for which a total pressure ratio (TPR) of 102.5 is reached with a pressure ratio loss (PRL) of 13.4%. Furthermore, in the actual hybrid cryocooler, the acquired values of suction pressure, TPR and PRL are 1.75 kPa, 101.7 and 14.1%, respectively, which is of great significance for the hybrid cryocooler in achieving 1.8 K. The rationality and feasibility of the coupling principle are experimentally verified.

About the “Heat Shock” Phenomenon

At present, depletion and diminished performance of oil formations take place. Operation of low production wells is carried out using ESP units at the rate of max. 35 m3/per day under low suction pressure of centrifugal pumps. The drop of the centrifugal pump suction pressure below the saturation pressure leads to liberation of free gas in the pumped mixture. Operation of a centrifugal pump during pumping of gas-cut mixtures results in reduction of the ESP unit efficiency. The loss of the pump efficiency leads to the fact that the substantial part of energy is consumed on heating and temperature rise of the centrifugal pump. Operation of a centrifugal pump at elevated temperatures results in frequent faults of the ESP units and in salt deposition. In some cases, faults of the ESP units may occur out of the blue due to the uncontrolled heat release and temperature rise. Let us call a sudden uncontrolled heating of a centrifugal pump a “heat shock”. The pump failure as a result of a heat shock is normally classified as the “wrongdoing of the oil producing organization personnel”. This article addresses the possibility of detection and elimination of the “heat shock” moment - a sudden ESP failure. Solution of this problem will be useful for design engineering of the pump automatic control.

Suppression of Cavitation Instabilities in an Inducer by the Circumferential Groove With Swirl Breakers

Abstract A circumferential groove with swirl breakers was designed and its effect on the suppression of cavitation instabilities in an inducer was investigated in experiments. The circumferential groove with the swirl breakers could suppress almost all cavitation instability phenomena effectively and improve suction performance. Observations of flow fields in CFD showed that the swirl breakers reduced the circumferential velocity of the flow near the blade tip at the inlet of the inducer. It was suggested that such a flow pattern succeeded in suppressing cavitation instability phenomena, including pressure fluctuations with high frequencies caused by the interaction of the blades with backflow vortices which were visible as backflow vortex cavities in low suction pressure.

Lung injury induced by different negative suction pressure in patients with pneumoconiosis undergoing whole lung lavage

BackgroundPneumoconiosis is a diffuse interstitial fibronodular lung disease, which is caused by the inhalation of crystalline silica. Whole lung lavage (WLL) is a therapeutic procedure used to treat pneumoconiosis. This study is to compare the effects of different negative pressure suction on lung injury in patients with pneumoconiosis undergoing WLL.Materials and methodsA prospective study was conducted with 24 consecutively pneumoconiosis patients who underwent WLL from March 2020 to July 2020 at Emergency General Hospital, China. The patients were divided into two groups: high negative suction pressure group (group H, n = 13, negative suction pressure of 300–400 mmHg) and low negative suction pressure group (group L, n = 11, negative suction pressure of 40–50 mmHg). The arterial blood gas, lung function, lavage data, oxidative stress, and inflammatory responses to access lung injury were monitored.ResultsCompared with those of group H, the right and left lung residual were significantly increased in the group L (P = 0.04, P = 0.01). Potential of hydrogen (pH), arterial partial pressure of oxygen (PaO2), arterial partial pressure of carbon dioxide (PaCO2), lactic acid (LAC) and glucose (GLU) varied from point to point in time (P < 0.01, respectively). There was statistical difference in the trend of superoxide dismutase (SOD) and interleukin-10 (IL-10) over time between the two groups (P < 0.01, P = 0.02). In comparison with the group H, the levels of IL-10 (P = 0.01) and SOD (P < 0.01) in WLL fluid were significantly increased in the group L. There was no statistical difference in the trend of maximal volumtary ventilation (MVV), forced vital capacity (FVC), forced expiratory volume in one second (FEV1%), residual volume (RV), residual volume/total lung capacity (RV/TLC), carbon monoxide dispersion factor (DLCO%), forced expiratory volume in one second/ forced vital capacity (FEV1/FVC%) over time between the two groups (P > 0.05, respectively).ConclusionLow negative suction pressure has the potential benefit to reduce lung injury in patients with pneumoconiosis undergoing WLL, although it can lead to increased residual lavage fluid. Despite differing suction strategies, pulmonary function parameters including FEV1%, RV and DLCO% became worse than before WLL.Trial Registration Chinese Clinical Trial registration number ChiCTR2000031024, 21/03/2020.

Internal Flow and Cavitation Analysis of Scroll Oil Pump by CFD Method

In this study, a three-dimensional model with actual clearances was established for a scroll oil pump, and the internal flow was simulated by the CFD method. The internal flows at different rotation angles were studied, and the cavitation and pressure pulsation in the scroll pump under different working conditions were analyzed. The results show that the flow in the two working chambers of the scroll pump is asymmetric due to its structural characteristics and motion mode. The high-pressure pulsation occurs in the working chamber during the end of the suction and the beginning of discharge. Under the action of high-pressure difference, there is a high-speed jet in the clearance between the orbiting and fixed scrolls, which causes a large area of cavitation downstream of the clearance. Under a low suction pressure, cavitation intensifies with the increase in rotating speed, which leads to a decrease in volumetric efficiency. It can effectively improve cavitation by increasing the suction pressure and volumetric efficiency of the pump. The pressure pulsation can be effectively improved by increasing the axial clearance and reducing the rotating speed. The method of reducing pressure pulsation by shortening the scroll profile is proposed.

Surge protection of centrifugal compressors using advanced anti-surge control system

Centrifugal Compressors (CCs) are widely used equipment to transport the natural gas over long-distance pipelines from the gas processing facility to end consumers. Surge protection is of vital importance for such compressors to avoid costly damage to machine and production loss due to process interruption. In this paper, the dynamic behaviour of CCs has been studied during four critical scenarios: high header pressure, low suction pressure, startup of the new unit, and emergency shutdown of the unit. The dynamic simulation has been carried out using HYSYS software and validated with an industrial scale CC plant. The advanced Anti-Surge Control (ASC) consists of a split PID control in contrast to conventional PID control. The simulation results demonstrate the superior performance of advanced ASC over a conventional one for the severe surge in the event of high header pressure and low suction pressure. The occurrence of surge during start-up and the emergency shutdown was handled with the full open operation of the Anti-Surge Valve (ASV). The proposed algorithm has proved successful in protecting the compressor during fast transients of the operating point towards the surge limit line. The study is significant for the oil and gas plants and other process industry professionals for designing effective ASC systems.

Prediction on the operation performance of axial piston pump at low suction pressure

The operation performance of the axial piston pump is affected by external environment pressure, and its conditions at low suction pressure are less studied. The oil model and fluid dynamic model of the axial piston pump are developed and a novel approach for predicting the operation performance of such machines at low suction pressure based on this model is presented. It was found that the inlet pressure of the suction chamber changes linearly with the environment pressure. Compared to the present data from the product manual, this approach is proved to be valid and is used to predict the maximum operating speed and suction pressure at other environment pressure, therefore the low-pressure operating performance map is enriched for the referring of more users of the pump. In future, this study provides a new method for the prediction and the design guide of pump operation at low suction pressures.

Prediction on the operation performance of axial piston pump at low suction pressure

Prediction on the operation performance of axial piston pump at low suction pressure

A new cyclone design with adjustable inlet angle and external geometry for optimal PM10 removal

In this study, a 2D2D cyclone layout was used as the base structure for the design of a new cyclone with an adjustable inlet angle and vortex finder height. The optimal conditions for the removal of fine particles were studied analytically and experimentally in the laboratory. The purpose of this study is to optimize the performance of the cyclone with different inlet angles to enhance particulate matter PM10 removal efficiency. The ASTM_D3685 method was used for sampling and testing the main factors. To determine the relationship between the variables and the study purpose, the data were analyzed using Minitab software (19). The results showed that the efficiencies of the removal of PM and particles with diameters of 10 μm, 4.7 μm, and 1 μm were 73.5%, 90%, 75%, and 60%, respectively. The cyclone was effective under a low suction pressure and 90° inlet angle, and a vortex finder height $$h_{\text{vf}} = \frac{1}{2}D$$. By optimizing the geometric structure, cyclones can be used as the main device to remove particulates, especially those of 1–10 μm, in a variety of industries and in particular sensitive industries.

Effect of straw addition on soil infiltration characteristics and model-fitting analysis

This study explored the influence of straw addition on the soil water characteristic curves and the soil water holding capacity. Using two different soil bulk densities, soil infiltration was investigated using differently treated straw, i.e., comminuted ammoniated, and blended with inorganic soil conditioner. The experimental results showed that the addition of long straw significantly obstructed soil infiltration. Compared with the control experiment and the comminuted straw treatment, both the addition of ammoniated comminuted straw and the inorganic soil conditioner (Fe (OH)3) effectively improved the soil stable infiltration rate and the cumulative infiltration. After 30 days of culturing, the ammoniated straw treatment affected a more remarkable improvement of the soil structure by reducing the soil bulk density and increasing the soil porosity than did the inorganic soil conditioner treatment. Using a straw and inorganic soil conditioner in combination did not result in a positive interaction for soil improvement. The relative ranking of each treatment on soil infiltration performance was the same for both soil bulk densities. For the soil water characteristic curve of each treatment, both the Philip infiltration model and the van Genuchten (VG) fitting model using RETC software had excellent fitting accuracy. The excellent soil water holding capacity arising from the use of ammoniated comminuted straw at low suction pressures is of significance for soil water preservation in the dry season of the humid region of southern China.

An Advanced Surge Dynamic Model for Simulating Emergency Shutdown Events and Comparing Different Antisurge Strategies

The compressor surge is a phenomenon which has to be avoided since it implies the deterioration of performance and leads to mechanical damage to the compressor and system components. As a consequence, compression system models have a crucial role in predicting the phenomena which can occur in the compressor and pipelines during operation. In this paper, a dynamic model, developed in the matlab/simulink environment, is further implemented to allow the study of surge events caused by rapid transients, such as emergency shutdown events (ESD). The aim is to validate the model using the experimental data obtained in a single-stage centrifugal compressor installed in the test facility at Southwest Research Institute. The test facility consists of a closed loop system and is characterized by a recycling circuit, and thus a recycling valve, which is opened in case of surge or driver shutdown. Simulations were carried out at 17,800 and 19,800 rpm; the comparison with experimental data showed the accuracy of the model in simulating different opening rates and different sizes of the recycle valve, at both low and high suction pressure (HSP). Moreover, different actions for recovering/preventing surge were simulated by controlling different valves along the piping system and by adding a check valve immediately downstream the compressor. The results demonstrated the fidelity of the model and its capability of simulating piping systems with different configurations and components, also showing, qualitatively, the different effects of some alternative actions which can be taken after surge onset.

Permanent gully increases the heterogeneity of soil water retention capacity across a slope-gully system

The coexistence of permanent gully and slope farmland in the northern Loess Plateau catchment has experienced great changes since the implementation of the Grain for Green project in 1999. This program swaps agricultural production in the slope land for soil and water conservation measures. To date, the slope-gully system soil water retention capacity are poorly understood. In our study, undisturbed soil samples at 0–25 cm depth were taken from three transects along a gully bottom, bank and nearby slope, and the effects of gully terrain and slope position on the soil water retention curves (WRC) in two soil layers (surface layer: 0–12 cm; sub-surface layer: 12–25 cm) were evaluated. The results showed that: (1) with the increasing suction, soil water retention capacity within the vertical direction of the gully bottom was constant and increased on the nearby slope. For all the slope positions on the gully bank, the WRC shapes of surface soil differed from those of sub-surface soil; (2) The capillary rupture moisture in the surface soil at the lower (L-) slope of the gully bank occurred at low suction pressure. The available water content of the L-slope was lower than the upper (U-) slope in the gully bank; (3) The gully increased the complexity of soil pore distribution across the slope-gully system. The gully bank reduced the water retention capacity of surface soil. In conclusion, the permanent gully enhanced the heterogeneity of soil water retention capacity. These results provide specific information about hydrological functioning in gullied areas and improves our understanding of soil hydrology in the post-farmland environment in the northern Loess Plateau.

Respiratory failure caused by impending tension pneumothorax after extrapleural pneumonectomy: a case report

BackgroundCardiac herniation is a serious postoperative complication of extrapleural pneumonectomy (EPP) and is reportedly preventable by reducing the suction pressure of the chest drain.Case presentationWe describe a patient in whom respiratory failure, which was caused by impending tension pneumothorax after EPP, was successfully treated via normal suction pressure of the chest drain. A lower suction pressure (− 7 cmH2O) was chosen as an alternative to the setting typically used for postoperative drainage (− 15 cmH2O). As a result, the wound in the chest wall functioned as an antireflux check valve, leading to the development of impending tension pneumothorax.ConclusionsImpending tension pneumothorax presents with an abnormal elevation of intrapleural pressure on the affected side. This phenomenon can be effectively treated by increasing the suction pressure in the chest drain.

Role of drain in early clinical outcomes following primary total knee arthroplasty

PurposeTo compare and study the short-term clinical outcome in patients with or without a drain usage in primary total knee arthroplasty (TKA). MethodsA prospective cohort study in a consecutive series of 61 women and 39 men (mean age, 66 years) with primary osteoarthritis underwent unilateral TKA. In the first 50 patients a low suction pressure drain was used for six hours, and in the next 50 patients no drain was used following TKA. ResultsThe 2 groups were comparable in terms of preoperative characteristics, age group, the proportion of patients with pharmacological prophylaxis for deep vein thrombosis, usage of anti fibrinolytics before surgery, the tourniquet time, mode of anaesthesia, operative approach and steps and type of implant used. The mean drain output in the drain group was 92ml. The time to achieve straight-leg raising was earlier in the drain group (2.1 vs. 3.2 days, p<0.005), and time to achieve knee flexion to 90° is earlier in patients with drain group (6.2 vs. 7.7 days, p<0.005). In addition, patients of drain group had lesser postoperative wound soakage, need for dressing change and analgesics. The fall in haemoglobin rate was slightly more in drain group however there was no significant difference in the rate of blood transfusions in both groups and no significant difference in infection rate. ConclusionThe use of a short duration (six hours), low suction pressure drain following total knee replacement enabled earlier return of quadriceps power, and range of motion, without increasing infection and blood transfusion rate. It also resulted in less pain and reduction in analgesic requirement in early postoperative period.

Effects of inducer tip clearance on the performance and flow characteristics of a pump in a turbopump

A turbopump is used to pressurize propellants to gain high thrust in a projectile and consists of two pumps and a turbine. The pumps usually employ an inducer upstream to prevent performance deterioration by lowering net positive suction head required of the main impeller. However, several types of cavitation and instabilities take place in the flow field. Therefore, numerous experiments and CFD analysis for turbopumps have been conducted. Especially, there were some previous studies on inducer tip clearance, but they were limited to inducer regions due to the complexity of simulating the entire pump. In this study, the flow through an oxidizer pump in a turbopump was numerically investigated with four different sizes of inducer tip clearances. ANSYS CFX 13.0 with Rayleigh–Plesset equation was used to test flows in both non-cavitating and cavitating conditions. In the non-cavitating condition, the pump with the largest inducer tip clearance showed the worst head rise, efficiency and huge size of backflow arose near inducer casing. Also, the vortex was generated between the inducer blades in the case of large inducer tip clearance due to weak tip leakage flow. In the cavitating condition, the inducer with large tip clearance was found to be vulnerable to low suction pressure and floating cavity was observed between the inducer blades. However, the heads of the pumps with different inducer tip clearances were broken down at similar cavitation numbers due to the blade cavitation near the impeller throat. In addition, the transferred cavity from the inducer region also induced head breakdown of the pump.

Numerical simulation of three-dimensional external gear pump using immersed solid method

External gear pumps are typically used as positive displacement machines that are capable of developing high pressures while operating at low suction pressures in hydraulic systems. Considerable attention has paid recently been given to investigating the flow characteristics and enhancing pump efficiency using theoretical, numerical, and experimental approaches. In this study, three-dimensional (3D) numerical simulations of an external gear pump were conducted to study the effects of 3D geometrical design parameters on pump performance characteristics such as the flow rate. The characteristics of internal flow are also presented with respect to the internal pressure peak, local cavitation, and delivery pressure ripple. The immersed solid method (ISM) was used to simulate the operation of a gear pump under extreme conditions of high rotational speed. We found that the maximum flow rate of the gear pump is a strong function of the gear tip clearance and lateral clearance. Using the 3D model, the effect of the lateral clearance on flow rate is highlighted.