High Suction Pressure Research Articles

Control system for suction valves within gas compressors skids located in potentially explosive zones

The paper presents the implementation of a feedback loop controller for the suction valves used within the gas compressors skids manufactured by Romanian Research and Development Institute for Gas Turbines COMOTI. These compressors are installed at beneficiaries, in potentially explosive environments (e.g., gas extraction and transportation applications). The proposed solution addresses the problems observed due to the high suction pressures of screw compressors, which may occur at start-up or during operation, leading to failed start-ups or emergency shutdowns. An automatic sequence implemented in the control software and displayed on the operating panel, could assist the operator during high suction pressures (above 1.2 bar). These pressure conditions normally lead to alarm limits and to performing an automatic shutdown sequence for protecting the compressor. The paper herein discusses the implementation of a start-up sequence in the programmable logic controller’s software, which can be applied without critical interventions on the compressor packages, only through minor control software modifications which can safely extend the inlet pressure range and the exploitation of the compressors. Thus, since no hardware modifications are required, we also ensure maintaining the ATEX certifications of equipment and assemblies.

CFD modelling of longwall goaf atmosphere under vertical boreholes gas drainage

To effectively control and utilise large amounts of gas emissions from underground coal mining, Australia and many other countries rely heavily on a series of vertical boreholes to capture the gas during mining. This gas capture not only reduces the greenhouse gas impact but also recovers a significant amount of energy. Vacuum pumps are connected to surface boreholes to drive gas flow from the goaf and overlying fractured strata. However, applying high suction pressure to the boreholes may cause more oxygen to enter the goaf from the longwall working face. This influx of oxygen can potentially react with residual coal in the goaf, accelerating coal self-heating and possibly resulting in endogenous fires. By analysing extensive goaf gas drainage data collected from Australian longwalls, researchers have established the normal trend of goaf gas concentration and flow rate as a result of intensive goaf gas drainage. This paper further developed goaf gas flow CFD models with the operating vertical boreholes, which were then calibrated using field borehole production data under certain operating conditions. The CFD model simulated the distribution of O2 and CH4 as well as the gas flow pathways in the goaf, considering the complication of goaf gas drainage. This study found that the O2 concentration is higher on the goaf tailgate side under the influence of tailgate side boreholes compared to the maingate side. Furthermore, for the well-compacted goaf, a significant proportion of the ventilation air travels through ‘high permeability flow channels’ provided by the goaf edge on tailgate side, and then circulates back into the goaf boreholes. These CFD modelling results not only enable ventilation engineers to visualize the goaf gas flow patterns under the impact of multiple operating boreholes, but also to understand the impact on goaf atmosphere through sensitivity analysis of natural goaf characteristics, such as goaf permeability distributions and gas emission rates.

Safe Removal of Sticky Silicone Oil Using Perfluorocarbon Liquid Injection and Emulsification with a Fragmatome.

We examine the safe removal of a sticky silicone oil (SO) with an inconspicuous perfluorocarbon liquid (PFCL) layer. In the first experiment, we injected PFCL into the SO bubble on the bottom of a transparent container or into the chili oil layer of an immiscible droplet composed of PFCL and chili oil on the posterior retina of a vitrectomized pig eye, in order to release the SO bubble or the chili oil layer from the downward adhesion. In the second experiment, we sucked out the SO layer of an immiscible droplet composed of PFCL and SO on the bottom of a transparent container or on the posterior retina of a vitrectomized pig eye using a fragmatome. In the first experiment, the PFCL injection caused the SO bubble to move from the bottom of the transparent container and the chili oil to move from the posterior retina of the pig eye. In the second experiment, when the suction pressure was high, this made it easy and possible to remove the SO layer in the transparent container or the vitrectomized pig eye when emulsification was done by a fragmatome. Moving the SO layer of a sticky SO from the posterior retina after a PFCL injection followed by sucking out of the relocated SO layer using emulsification and high suction pressure through the utilization of a fragmatome can safely remove sticky SO with an inconspicuous PFCL layer.

Dynamics and morphological evolution of a fiber conveyed in a three-dimensional rotor spinning unit: a numerical study

To interpret why rotor-spun yarns have fewer straight fibers, numerical simulations are performed to explore the fiber dynamics and morphological evolution during its conveyance in a rotor spinning unit by the airstream. Results show that the fiber experiences a sharp speed increase after reaching the shear boundary layer of the rotating wall. The sharp speed increase ends when the fiber arrives at the rotor groove where its morphology and speed barely change. The fiber straightness undergoes a process of first decreasing and then increasing during the conveyance and the worst fiber straightness is obtained halfway during the fiber’s sliding process. Compared with the fiber transport channel (FTC) angle, the rotor speed and the suction pressure play a more important role in affecting the fiber dynamics and morphological evolution. Fiber can be more efficiently conveyed as the rotor speed increases or/and the suction pressure decreases, and its straightness varies non-monotonically with these two parameters. Too low or too high rotor speed and suction pressure could result in a decrease in the fiber straightness, and the straightest fiber is obtained at a medium rotor speed of 80,000 rpm and a medium suction pressure of −8000 Pa for our considered system parameters.

Identifying the performance and losses of a scroll compressor with vapour injection and R1234ze(E).

This work investigates a vapour injection scroll compressor integrated in a heat pump using the refrigerant R1234ze(E). The water-to-water heat pump was tested under a wide temperature range at the evaporator and condenser sides. The test results revealed that the performance is significantly reduced for lifts of over 30 K with the coefficient of performance being even below 2 and the maximum 2 nd law efficiency was just 28%. In order to enlighten the reasons behind such significant compressor underperformance, a semi-empirical model has been extended to include vapour injection, and a new improved modelling approach for the suction pressure drop was developed and implemented considering both the turbulent and laminar inlet flow regimes. Once the accuracy of the developed semi-empirical model was verified, the model was then adjusted to account for the R1234ze(E) operation, by fine-tuning its parameters based on the test data. The main loss mechanism identified is the high suction pressure drop, due to the high friction factor, with the inlet refrigerant flow possibly being laminar instead of turbulent. This resulted in a significant reduction of the mass flow rate and volumetric efficiency, while the standard model for suction pressure drop was not able to capture this effect.

A theoretical goaf resistance model based on gas production analysis in goaf gas drainage

Over the past few years, the Australian coal mines heavily relied on drilling vertical goafholes to capture coal mine methane and monitor methane levels, which is named goaf gas drainage. The suction pressure applied on the surface goafholes may change goaf pressure distribution and goaf gas flow pathways. Besides, high suction pressure may cause more air leakage in the goaf and increase the risk of gas explosion and spontaneous combustion, posing a significant threat to mine safety. This paper focuses on analysing goaf gas production data from different goafholes in two active Australian longwall panels. The correlation between suction pressure, total flow rate, gas flow rate and air leakage rate were analysed in detail as the face-to-hole distance changed. Suction pressure is found to be positively correlated with total flow rate, and their correlation also varies at different goaf locations due to various goaf compaction and flow resistance. As a result, instant control strategies are suggested for different scenarios based on adjusting goafhole suction pressure. This paper also proposed a theoretical method to calculate the goaf resistance of ventilation air leakage pathways. The model results suggested that the resistance of air leakage pathways from the working face to individual goafholes increased with the face-to-hole distance, and the resistance results can be used to calculate the corresponding permeability at the same goaf position. These results may be applied to calibrate other geomechanical models and as input data for CFD or Ventsim models with a clear understanding of simulation tool limitations.

Full versus half suction drainage after modified radical mastectomy for breast cancer

Background: Suction drains are routinely used after modified radical mastectomy and are an important factor contributing to increased hospital stay as the patients are often discharged only after their removal. Amongst various factors that influence the amount of postoperative drainage, the negative suction pressure applied to the drain has been reported to be of great significance. While a high negative suction pressure is expected to drain the collection and reduce the dead space promptly, it may also prevent the leaking lymphatics from closing and lead to increased drainage from the wound. Against this background a prospective randomized clinical study was conducted to compare the amount and duration of drainage between a half negative suction and full vacuum suction drainage in patients following modified radical mastectomy. The associated postoperative morbidity was also compared between the two groups. Methods: 40 FNAC (fine needle aspiration cytology) proven cases of locally advanced breast cancer were randomized. (Using randomly ordered sealed envelops, which were opened immediately before the closure of the wound) in to 20 patients with full vacuum suction (pressure = 700 g/m2) and 35 cases in to half vacuum suction drainage (pressure = 350 g/m2) groups.

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.

Identifying the performance and losses of a scroll compressor with vapour injection and R1234ze(E)

This work investigates a vapour injection scroll compressor integrated in a heat pump using the refrigerant R1234ze(E). The water-to-water heat pump was tested under a wide temperature range at the evaporator and condenser sides. The test results revealed that the performance is significantly reduced for lifts of over 30 K with the coefficient of performance being even below 2 and the maximum 2nd law efficiency was just 28%. In order to enlighten the reasons behind such significant compressor underperformance, a semi-empirical model has been extended to include vapour injection, and a new improved modelling approach for the suction pressure drop was developed and implemented considering both the turbulent and laminar inlet flow regimes. Once the accuracy of the developed semi-empirical model was verified, the model was then adjusted to account for the R1234ze(E) operation, by fine-tuning its parameters based on the test data. The main loss mechanism identified is the high suction pressure drop, due to the high friction factor, with the inlet refrigerant flow possibly being laminar instead of turbulent. This resulted in a significant reduction of the mass flow rate and volumetric efficiency, while the standard model for suction pressure drop was not able to capture this effect.

Development of a Hose Reel (Swivel Joint) Suitable for High Suction Pressures

Development of a Hose Reel (Swivel Joint) Suitable for High Suction Pressures

Experimental Investigation of Leakage in the Modified Revolving Vane Expander

Abstract This study focuses on the leakage characteristics of a modified revolving vane expander (M-RVE) using both static and dynamic leakage analysis. The no-expansion scenario showed a maximum volumetric efficiency of 18.7% was achieved at 5.5 bar(g) suction pressure, showing the severity of internal leakages. The blocker angle study demonstrated the importance of the correct opening-angle selection to avoid under or over-expansion. The maximum volumetric efficiencies for opening angles of 94 deg and 145 deg were 2.8% and 8.3%, respectively, at suction and discharge pressures of 6.5 bar(g) and 1 atm, respectively. The static leakage test demonstrated that the M-RVE housing was properly sealed, and the observed leakage in the dynamic test was mostly due to internal leakages. The results showed that the leakages through the radial clearance, endface, and vane side gaps make up 54%, 33%, and 8.5% of the overall leakage. Comparison between the theoretical and experimental data of the leakages through the radial clearance gap showed significant deviations at higher suction pressures. The reasons are thought to be due to the shafts' tilt, and the cylinder and rotor head deflections. It is believed that the deflection of the shaft created new leakage paths or changed the geometry of the current paths.

Role of Mesh Pore Size in Dynamic Membrane Bioreactors

Two identical bench-scale Self-Forming Dynamic Membrane BioReactors (SFD MBR) were set-up and operated for the treatment of real urban wastewater. The two bioreactors were equipped with meshes of different mesh pore size. Meshes having pore size values of 20 and 50 µm were tested under solid retention time (SRT) of 15 d, whereas meshes with 50 and 100 µm pore sizes were compared under SRT of 50 d. The results of long-term experiments showed very good overall performances by all systems at the steady state. High flux (in the range 61–71 L m−2 h−1) and very good effluent quality were obtained, with average suspended solids and chemical oxygen demanding values below 10 mg L−1 and 35 mg L−1, respectively. The mesh pore size did not have a major influence on the average cleaning frequency. However, the pore size affected the effluent quality in correspondence of two particular conditions: (i) immediately after mesh cleaning; and (ii) during operation under high suction pressures (mesh clogging not promptly removed through cleaning). Moreover, the mesh cleaning frequency was observed to be dependent on the SRT. In tests with 50 d SRT, the cleaning requirements were very low (one every five days), and this limited the influence of the mesh pore size on the effluent quality. In conclusion, in SFD MBR, the role of the mesh pore size on the effluent quality may be more or less relevant depending on the operating conditions that directly influence the Dynamic Membrane formation.

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.

Suction Feeding by Small Organisms: Performance Limits in Larval Vertebrates and Carnivorous Plants.

Suction feeding has evolved independently in two highly disparate animal and plant systems, aquatic vertebrates and carnivorous bladderworts. We review the suction performance of animal and plant suction feeders to explore biomechanical performance limits for aquatic feeders based on morphology and kinematics, in the context of current knowledge of suction feeding. While vertebrates have the greatest diversity and size range of suction feeders, bladderworts are the smallest and fastest known suction feeders. Body size has profound effects on aquatic organismal function, including suction feeding, particularly in the intermediate flow regime that tiny organisms can experience. A minority of tiny organisms suction feed, consistent with model predictions that generating effective suction flow is less energetically efficient and also requires more flow-rate specific power at small size. Although the speed of suction flows generally increases with body and gape size, some specialized tiny plant and animal predators generate suction flows greater than those of suction feeders 100 times larger. Bladderworts generate rapid flow via high-energy and high-power elastic recoil and suction feed for nutrients (relying on photosynthesis for energy). Small animals may be limited by available muscle energy and power, although mouth protrusion can offset the performance cost of not generating high suction pressure. We hypothesize that both the high energetic costs and high power requirements of generating rapid suction flow shape the biomechanics of small suction feeders, and that plants and animals have arrived at different solutions due in part to their different energy budgets.

Effect of loading rate on the pullout capacity of offshore bucket foundations in sand

A series of 1 g model tests was performed to investigate the effect of loading rate on the vertical pullout capacity of offshore bucket foundations in sand. The bucket model had a length-to-diameter ratio of 1.0. Loading rates varied from 0.004 N/s to 2.05 N/s. The pullout load increased with bucket displacement and loading rate. The loading rate of 0.004 N/s induced drained conditions with negligible suction pressure and high skin resistance. Increasing the loading rate induced high suction pressures inside the bucket. The bucket pullout capacity increased with bucket displacement and loading rate. Suction pressure increased with bucket displacement and loading rate and contributed considerably to the pullout capacity. The bucket resistance to pullout load increased with the increase in loading rate. Equations were proposed to evaluate the drained and undrained pullout capacities of the bucket.

Effects of oxyhydrogen gas induction on the performance of a small-capacity diesel engine.

Compression ignition engines are one of the world's largest consumers of fossil oil but have energy extraction efficiency limited to 35%. Addition of hydrogen alongside diesel fuel has been found to improve engine performance and efficiency; however, after a certain limit, hydrogen begins to show adverse effects, mainly because the ratio of oxygen to fuel decreases. This can be overcome by using oxyhydrogen, which is a mixture of hydrogen and oxygen gas. In this study, effects of addition of oxyhydrogen generated by electrolysis, with varying flows at the intake manifold, on a 315 cc compression ignition engine alongside diesel were analyzed. The engine was mounted on a Thepra test bed and torque measurements were taken at predetermined test points for diesel and 6 and 10 standard cubic feet per hour flowrates of oxyhydrogen. H10 showed the maximum improvement in engine performance equating to a 22.4% increase in both torque and power at 3000 r/min, and a 19.4% increase in efficiency at 2600 r/min was recorded. The large increase in engine performance as compared to previous results is because of high oxyhydrogen flowrate to displacement volume ratio. The oxyhydrogen flowrate to displacement ratio is the most important factor as it is directly impacts engine performance. The difference in engine performance because of oxyhydrogen becomes prominent at higher engine speed due to high suction pressure. No experimental flowrates of oxyhydrogen showed any adverse effect on the engine performance.

The diagnostic quality of needle brain biopsy specimens obtained with different sampling methods \u2013 Experimental study

The aim is to examine whether brain tissue samples obtained through needle biopsy are better for histopathological evaluation when obtained with defined vacuum pressure, a novel needle rotation method, and using different needle type - Laitinen or Nashold. Moreover the paper aims to answer the question: Does vacuum and mechanical injury resulting from different sampling methods damage the tissue specimen challenging the diagnosis?. Eight hundred biopsy specimens from fresh swine brains were obtained using Nashold and Laitinen brain biopsy needles through inner cannula cutting or needle rotation sampling at vacuum pressure, from 0 to 0.06 MPa. The specimen weight and tissue quality for microscopic assessment were evaluated using the Mair score. Rising aspiration pressure increased the biopsy sample weight. Needle rotation delivered larger biopsy samples than the standard method. Laitinen provided larger samples than the Nashold needle, with the same sampling method or vacuum pressure. A higher histopathological diagnostic quality of tissue was obtained with the Laitinen needle than with Nashold, with higher vacuum pressure than lower pressure and finally with needle rotation than the standard method. No tissue damage caused by higher suction pressure or method of tissue separation was documented. Brain tissue samples obtained through needle biopsy are better for histopathological evaluation when obtained with higher vacuum pressure, a novel needle rotation method and with Laitinen needle. Higher suction pressure and sampling methods did not cause tissue damage.

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.

Bradycardia Secondary to Negative Suction Pressure Applied to Chest Drain

Positive pressure generated in peritoneal cavity by gas insufflation during laparoscopic procedures can cause hemodynamic instability. There are a few case reports suggesting similar occurrences during thoracoscopic procedures as well. The mechanism behind the conditions above is explained to be due to stretch force applied to peritoneum and pleura which causes vagal stimulation. We wish to present a case where a high negative pressure applied to pleural cavity lead to treatment-resistant bradycardia. The possible mechanism behind this occurrence was traction pressure on pleura which triggered vagal activity. The bradycardia subsided on reducing or discontinuing negative suction pressure. To best of our knowledge this the first case report on bradycardia associated with high negative suction pressure applied to inter costal drain.

Sintering of Iron Ores in a Millipot in Comparison with Tablet Testing and Industrial Process

To explore the feasibility of small-scale sintering pot testing, a ‘millipot’ facility (diameter of 53 mm and height of 400 mm) was established and used to examine the sintering performance of iron ores and other non-traditional ferrous materials. The sintering performance of a millipot was examined across a range of different operational conditions (coke rate and suction pressure) and compared with an industrial sinter strand operation. Tablet tests were also performed to assist in the design of the millipot experiments and identify conditions for achieving mineral composition similar to the industrial sinter. For the millipot experiments, the materials used need to be compacted to increase the bulk density, and a higher coke rate is required to compensate the high heat loss caused by wall effects. A higher suction pressure is also necessary to maintain an oxidizing atmosphere in the sinter bed. As expected, it was not possible to eliminate the wall effect, which resulted in more primary hematite at edges of the sintered column. However, the sintered material from the center of column simulates industrial sinter reasonably well. As such, millipot provides a practical way to evaluate the sintering process and material performance at laboratory scale, helping to bridge the gap between tablet sintering and large scale pot sintering, or full scale plant trial. The results of millipot testing can be used for designing larger scale experiments or commercial sintering trials.