Valve Closure Research Articles

Investigation of partially expanded surge tank with self-adaptive auxiliary system controlling water hammer in pipelines

Intensive water hammer can cause pipe collapse in long-distance water transfer pipeline systems. Pressure control facilities like surge tank have been widely applied to help control the extensive pressure fluctuations. In our previous work, a kind of spring self-adaptive auxiliary control (SAC) system was proposed and demonstrated to have a significant improvement on pressure control capacity of a normal surge tank. In this study, an additional solution, a partially expanded structural treatment, was introduced to a conventional SAC surge tank to further improve its functional ability. The 1D numerical model was established in our in-house codes on FORTRAN. The dominant geometrical parameters were identified and quantitatively studied with various cases. According to the effects of the geometrical parameters, a designing protocol for searching the optimal solutions of partially expanded SAC surge tank was concluded. With the obtained optimal solutions, the proposed partially expanded SAC surge tank can perform a much better pressure control performance dealing with valve closure induced water hammer, compared with a conventional SAC surge tank as well as a normal surge tank.

Evaluation of the variable valve timing strategy in a direct-injection hydrogen engine with the Miller cycle under lean conditions

The favorable physicochemical characteristics of hydrogen make it an excellent alternative fuel for IC engines. Compared with hydrogen port injection, hydrogen direct injection provides multiple degrees of freedom for injection strategies and mixture formation, which can effectively suppress abnormal combustion and enhance engine performance. Variable valve timing (VVT) and the Miller cycle, as advanced and effective means of improving engine performance, are less investigated based on a direct-injection (DI) hydrogen engine. Hence, to optimize the performance of a DI hydrogen engine, strategies of the Miller cycle and VVT are introduced. In this work, a 1.5 L direct-injection engine with a VVT system was employed to evaluate the effects of the Miller cycle, intake valve closing (IVC) timing, and exhaust valve opening (EVO) timing on the airflow exchange process, in-cylinder charge characteristics, heat release process, dynamics and emission characteristics. The engine speed was stabilized at 1400 rpm and the strategies of lean combustion and late injection were used. The main results are as follows. As the IVC timing is delayed, the ratio of pumping mean effective pressure to indicated mean effective pressure (PMEP/IMEP) first decreases and then slightly increases, and the engine tends to achieve a high level of brake thermal efficiency (BTE) when PMEP/IMEP is lower. The optimization of intake and exhaust VVT can shorten combustion duration and reduce cyclic variation by increasing volumetric efficiency and improving mixture distribution at ignition timing. Furthermore, the engine reaches 42.22% BTE and a high level of brake mean effective pressure by the cooperative control of IVC and EVO timing. NOx emissions can be controlled below 100 ppm by employing the synergistic effect of the Miller cycle and VVT. It is worth mentioning that exhaust VVT as a way to compensate for the performance of the DI hydrogen engine with the Miller cycle should not be ignored.

Negativity of the electromechanical window: relation to frequent premature ventricular complexes.

The electromechanical window (EMW) was investigated as a new predictor of arrhythmia in the presence of long QT. However, the use of EMW to predict idiopathic frequent ventricular premature complexes (PVCs) in those with normal QT intervals has not been clarified. This single-center study included consecutive patients who presented to the Cardiology Clinic with palpitations and were found to have idiopathic PVC on 24-hour Holter monitoring. Those with a PVC/24-hour frequency of < 1% were defined as group 1, 1-10% as group 2, and > 10% as group 3. The EMW was defined as the time difference (in ms) between the aortic valve closure and the end of the QT interval, measured from an ECG on the concurrent echocardiogram. A total of 148 patients were included in the study, 64% (n = 94) of which were female. The patients' mean age was 50.11 ± 14.7. The groups were similar in terms of the patients' age, BMI, and comorbidities. There was a statistically significant difference between the three groups in terms of the EMW measurements (group 1: 3.78 ± 19.6, group 2: -7 ± 30.9, group 3: -34.83 ± 55.2 ms: p < 0.001). In the multivariate regression analysis, the EMW (OR 0.971, p = 0.007) and every 10-ms decrease in the EMW (OR 1.254, p = 0.011) were thus determined to be independent predictors of PVC > 10%. An EMW value of ≤ -15 ms was associated with the frequency of 24-h PVC > 10%, with a sensitivity of 70% and a specificity of 70% (AUC 0.716, 95% CI: 0.636-0.787 p < 0.001). The results showed that a negative increase in the EMW may be associated with frequent idiopathic PVCs.

A Case of Rheumatic Heart Disease Complicated by Acute Infective Endocarditis and Valve Leaflet Perforation

Rheumatic Heart Disease (RHD), abbreviated as rheumatic heart disease, is a heart disease caused by repeated attacks or further deterioration of Acute Rheumatic Fever (ARF), which is mostly caused by valve damage (Zhang P &amp; Wang P., 2021). The production of ARF is the result of a series of autoimmune reactions by group A streptococci that invade the pharynx of a susceptible host. Clinically, rheumatic heart disease mostly involves valves, which can cause patients to have a variety of manifestations such as incomplete valve closure or stenosis, structural remodeling of the heart, etc. If patients do not seek medical attention in time to delay the best time for treatment, they often develop acute heart failure, malignant arrhythmias and other acute complications of the cardiovascular system in the later stages of the disease. Clinically, rheumatic heart disease complicated by infective endocarditis is not common, and valve leaflet perforation due to severe infection is even rarer! A case of acute infective endocarditis complicated by atypical rheumatic heart disease and simultaneous valve leaflet perforation in our hospital is reviewed and reported below.

An Enhanced 3D Model of Intravascular Lymphatic Valves to Assess Leaflet Apposition and Transvalvular Differences in Wall Distensibility

Lymphatic valves operate in a fluid-dynamically viscous environment that has little in common with that of cardiac valves, and accordingly have a different, axially lengthened, shape. A previously developed 3D fluid/structure interaction model of a lymphatic valve was extended to allow the simulation of stages of valve closure after the leaflets come together. This required that the numerical leaflet be prevented from passing into space occupied by the similar other leaflet. The resulting large deflections of the leaflet and lesser deflections of the rest of the valve were mapped as functions of the transvalvular pressure. In a second new development, the model was reconstructed to allow the vessel wall to have different material properties on either side of where the valve leaflet inserts into the wall. As part of this, a new pre-processing scheme was devised which allows easier construction of models with modified valve dimensions, and techniques for successfully interfacing the CAD software to the FE software are described. A two-fold change in wall properties either side of the leaflet made relatively little difference to valve operation apart from affecting the degree of sinus distension during valve closure. However, the numerically permitted strains were modest (<14%), and did not allow examination of the large-scale highly nonlinear elastic properties exhibited by real lymphatic vessels. A small series of murine popliteal, mesenteric, and inguinal-axillary lymphatic vessel segments containing a valve were experimentally investigated ex vivo. The pressure-diameter curves measured just upstream and just downstream of the valve were parameterised by computing the difference in tubular distensibility at three values of transmural pressure. In the popliteal and mesenteric segments, it was found that the distensibility was usually greater just downstream, i.e., in the sinus region, than upstream, at low and intermediate transmural pressure. However, there was wide variation in the extent of difference, and possible reasons for this are discussed.

Dual-output PID transient control of an electric-assisted air charge system

Turbo-compressor assembly (also called turbocharger) is added to diesel engines to increase their power density and improve performance. However, during power step-up operations, the added turbocharger system could lead to a significant delay of engine response (also called turbo-lag) which negatively impact drivability. In this paper, an external electric compressor (eBoost) is added to a turbocharged, large displacement diesel engine to significantly reduce turbo-lag, along with a bypass valve. Now, the air charge system has two control targets (boost (intake manifold) pressure and rate of exhaust-gas recirculation (EGR)) but with four control actuators including EGR valve, variable geometry turbo (VGT) vane position, eBoost speed and bypass valve, making it challenge for developing the associated control scheme. In this paper, a dual-output PID (proportional-integral-derivative) controller is proposed for controlling the boost pressure using the VGT and eBoost to reduce turbo-lag, and a transition logic is also devised to detect transient operating conditions to activate the eBoost, along with the closing and opening of the bypass valve, with maximum benefit. The EGR rate PID control remains unchanged. The addition of the eBoost is shown to improve transient response time by up to 55% and reduce transient NOx emissions by up to 42% during transitional operations without negatively impacting steady-state engine performance or emissions. Note that transient performance can be further improved for production implementation when a single engine control module is used by eliminating communication delay among multiple control systems.

Cardiac cycle timing intervals in university varsity athletes

Cardiac cycle timing events in varsity athletes serve an important function for baseline assessment but are not reported in the literature. The purpose of this study was to characterize the cardiac cycle timing intervals and contractility parameters in university-level varsity athletes. 152 males and 93 females were assessed using a non-invasive seismocardiography cardiac sensor attached to the sternum for 1-minute. Shorter isovolumic relaxation time (IVRT), systolic time, mitral valve open to E-wave (MVO to E) time, rapid ejection period (REP), atrial systole to mitral valve closure (AS to MVC) time, and diastolic performance index (IVRT/systolic time) were found in females, while heart rate was lower in males. Varying differences in timing intervals were found between sports. Systolic times were longer in male and female basketball players, while diastole was shortest in male football players, who also had higher heart rates than the other male sport athletes. These results add reference cardiac cycle timing data to the literature and imply that male and female athletes show different cardiac characteristics. Team differences suggest that different training for different sports can result in unique cardiac function changes, however, these appear to be related to the sex of the participants. The addition of these cardiac cycle timing intervals adds a valuable comparative tool to better understand cardiac physiology in the varsity athletic population.

Shellfish as Biosensors in Online Monitoring of Aquatic Ecosystems: A Review of Russian Studies

The use of biological objects in monitoring the state of the environment and the changes caused by the impact of environmental pollution on marine and fresh waters is a promising tool due to a lower cost in comparison to traditional monitoring and the ability to receive immediate information about the ecosystem status. In this review, we summarize the biological information about shellfish biomonitors and the results of studies focused on the development and use of the bioindicator species in early warning systems in Russia. Since the mid-1980s, Russian specialists have developed online biomonitoring systems; as in the rest of world, there are two main approaches that are currently applied to study the physiological status of potential biosensor shellfish species and to monitor freshwater and marine systems: valvometry (registration of gaping activity in bivalve mollusks) and photoplethysmography (registration of cardiac activity in mollusks and crustaceans). Valve movement responses to stressors such as abnormal conditions and pollutants include the closure of shell valves for a long period, decrease in the average distance between valves, rapid shell opening, and higher closing frequency. Cardiac activity reactions of shellfish to stress factors include rapid increases in heart rate and stress index, higher variability in heart rate than under normal conditions, and longer periods required for heart rate recovery after stress. The most common bioindicators used to monitor environmental disturbances in marine ecosystems are blue mussels, Iceland scallops, and red king crabs in cold-water habitats and Black Sea mussels in warmer waters as well as freshwater mussels and crayfish in fresh waters.

Remote Impact Frequency Control of Air Hammers with Power Closure of Elastic Valve

Remote Impact Frequency Control of Air Hammers with Power Closure of Elastic Valve

Sound sensitivity of the giant scallop (Placopecten magelanicus) is life stage, intensity, and frequency dependent.

There is increasing concern that anthropogenic sounds have a significant impact on marine animals, but there remains insufficient data on sound sensitivities for most invertebrates, despite their ecological and economic importance. We quantified auditory thresholds (in particle acceleration levels) and bandwidth of the giant scallop (Placopecten magellanicus) and subsequently sought to discern sensitivity among two different life stages: juveniles (1 yr olds) and subadults (3 yr olds). We also leveraged a novel valvometry technique to quantify the amplitude of scallop valve gape reductions when exposed to different sound amplitudes and frequencies. Behavioral responses were obtained for lower frequencies below 500 Hz, with best sensitivity at 100 Hz. There were significant differences between the auditory thresholds of juveniles and subadults, with juveniles being more sensitive, suggesting ontogenetic differences in hearing sensitivity. Scallops showed intensity and frequency dependent responses to sounds, with higher valve closures to lower frequencies and higher sound levels. To our knowledge, these are the first data highlighting life stage, intensity, and frequency responses to sound in a marine benthic invertebrate. These results demonstrate clear sound sensitivity and underscore that the potential impacts of anthropogenic sound in valuable ecological resources, such as scallops, may be dependent on sound characteristics.

Reconstruction of the Left Atrioventricular Valve with Pericardial Patch Closure of the Ostium Primum Atrial Septal Defect in a Patient with Partial Atrioventricular Septal Defect under Mild Hypothermic Extracorporeal Circulation and Cardioplegic Arrest (UKC’s Modification): A Video Presentation

A 26-year-old male patient diagnosed with partial type of atrioventricular septal defect in sinus rhythm, cleft left atrioventricular valve with mild pulmonary arterial hypertension, and severe left atrioventricular valvular regurgitation successfully underwent reconstruction of the left atrioventricular valve and pericardial patch closure of the atrial septal defect using UKC’s modification. The technical details of the surgical procedure have been elaborated in detail.

Comparison of water and cryogenic fluid hammer experiments for rocket engine feed line systems

Fluid hammer occurs when a flow in a pipeline is rapidly stopped due to valve closure or shutting down a pump. The resulting pressure wave can reach very high amplitudes, depending on the fluid properties and the flow velocity. In spacecrafts and launchers, where the reduction of weight is always an important design goal, it is not possible to build the structure arbitrarily robust. Understanding the transient behaviour of the fluids is necessary to predict mechanical loads on the structure and align the design to them. Since a lot of launchers use reactive, cryogenic propellants, it is a common approach to use inert substitute fluids for on ground testing like water (H2O) or liquid nitrogen (LN2). LN2 comes with the advantage of being cryogenic like real propellants, but ground testing is consequently more complex than with H2O. For this purpose, several fluid hammer experiments with both fluids were performed and compared to each other to provide a foundation for deciding which substitute fluid would be useful.Graphical abstract

Numerical Analysis of Two-Stage Turbine System for Multicylinder Engine under Pulse Flow Conditions with High Pressure-Ratio Turbine Rotor

Internal combustion engine (ICE) exhaust gases provide a high amount of energy which is partially lost to the environment. Such energy can be recovered with a turbocharger turbine or other after-treatment device. As the engine exhaust flow varies not only with the engine load but also with the opening and closing of the exhaust valves, a proper matching between the engine and the turbine should be established to maximize the recovery of waste energy. That is why a twin-scroll or dual turbocharging system is implemented, especially in multi-cylinder engines. Such systems require a very complex pipeline to eliminate the interference of the exhaust pulses between the adjacent cylinder ignitions. In this study, the two-stage, multi-channel turbine system was investigated for two different rotor geometries: the old, high-performance rotor A and the smaller but more modern rotor B, which was scaled to match rotor A. Both geometries were compared at three different turbine speeds and variable turbine geometry (VTG) vane positions. It was found that the two-stage turbine system with rotor B geometry provided an 8% higher total efficiency than rotor A due to the lower flow losses within the rotor passage.

Remote Impact Frequency Control of Air Hammers with Power Closure of Elastic Valve

Remote Impact Frequency Control of Air Hammers with Power Closure of Elastic Valve

Quantification of Flow Rates and Flow Volumes in Valve Regurgitation Using 3-D High Frame-Rate Ultrasound

Valve regurgitation is a cardiac condition caused by the incomplete closure of a cardiac valve. Untreated, this condition may result in cardiac failure. Regular monitoring of this condition is essential in guiding the decision process for surgical intervention. Current guidelines recommend a multiparametric assessment of valve regurgitation using echocardiography, which is both time consuming and heavily dependent on the experience of the examiner. Several methods have been proposed to provide quantitative markers to facilitate the assessment of valve regurgitation, most notably the Proximal Isovelocity Surface Area (PISA) method and methods based on the quantification of the total Regurgitant Volume (RVol) from the power of backscattered blood signal. In this work, we propose a framework based on trans-thoracic 3-D high frame-rate acquisitions for the simultaneous estimation of the jet cross-sectional area and jet velocity directly at the jet core, which are then combined to estimate the instantaneous flow rate and RVol patients with aortic or mitral insufficiency. We compare two methods for the segmentation of the jet cross-sectional area from the power Doppler signal. Validation on simulated data indicates good segmentation accuracy for the best method (β = 0.97, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> = 0.91). Validation on recordings from a flow phantom shows good agreement (β = 1.2, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> = 0.88) with an external flow rate meter. Clinical feasibility of the method is also shown in a patient with mitral regurgitation.

The importance of post marketing quality control

BACKGROUND A previously published study reported on the nonlinear behaviour for airway pressure and tidal volume of the adjustable pressure-limiting (APL) valve of the Aisys CS2 anaesthesia machine (GE Healthcare, Madison, Wisconsin, USA) during manual bag ventilation. In co-operation with the manufacturer, an adapted APL valve was developed. OBJECTIVE To test and characterise the performance of an adapted APL valve and assess its clinical usability. DESIGN Two-stage study, consisting of an in-vitro testing of an adapted APL valve in a baby and adolescent lung model, followed by a clinical experience survey of anaesthesia personnel after the official implementation of the new APL valve into clinical routine. SETTING Anaesthesia Department at the University Children's Hospital Zurich. MAIN OUTCOME MEASURES Airway pressures and inspiratory tidal volumes during opening and closure of the APL valve at different settings. Likert scale assessment of performance expectance, effort expectance, behavioural intention and safety of the APL valve during clinical use. RESULTS In contrast to the original APL valve of the GE Aisys CS2, the adapted APL valve showed a nearly linear increase in airway pressures as well as in the tidal volumes measured. Most importantly, the measured pressures never exceeded the set pressures. Based on the experimental findings, all original APL valves of the GE Aisys CS2 were replaced by the adapted APL valve. Two months later, an anonymised and standardised questionnaire was handed out to all employees working with the adapted APL valve. Analysis of the questionnaire indicated that the adapted APL valve is easier and more precise to handle in the daily routine than the original one. CONCLUSION The newly adapted APL valve for the GE Aisys CS2 has considerably improved its linearity at lower pressures and supports our institution's bag mask ventilation practices.

An Innovative Miniaturized Cell Imaging System Based on Integrated Coaxial Dual Optical Path Structure and Microfluidic Fixed Frequency Sample Loading Strategy

On-site rapid detection of cells is especially of concern for many fields, image-based detection results can directly reflect the multi-dimensional information such as cell contour and aggregation state. This article proposes an innovative miniaturized cell imaging system based on integrated coaxial dual optical path structure and microfluidic fixed frequency sample loading strategy, which performs synchronous imaging of bright field mode and fluorescence field mode on cells. The bright field optical path and fluorescence field optical path are integrated into the coaxial dual optical path structure based on the dichroic mirror with splitting and steering functions. The movement of the shutter’s curtain is controlled by a micro-motor, so that the plane mirrors fixed on the curtain with different light angle can be switched to the optical axis, and the fast switching of the bright field optical path and the fluorescence field optical path can be implemented. A drawer-type filter module can be pulled out of the coaxial dual optical path structure, the emission filter and the dichroic mirror in this module can be replaced according to the fluorescence emission peak of the sample to be tested, thereby expanding the detectable cell types of this system. In addition, based on the force analysis and calculation of the fluid, a fixed frequency was obtained to drive the sample loading. The accumulated kinetic energy of the fluid during this period can be offset by the closing of the pinch valve, and the flow rate of the sample in the imaging field can be rapidly reduced to close to zero to avoid the tailing effect in the image. It is experimentally confirmed that the detection accuracy of this system, the registration matching accuracy of cells and fluorescent dots, the cell survival rate, and the detection sensitivity of cell viability. This system balances the tradeoff between portability, flux and accuracy, offers more functionality in terms of technology and application for on-site cell detection.

Numerical modeling of transient non Newtonian thinning fluid flow

This study concerns a numerical simulation of transient non-Newtonian fluid flow in a hydraulic pipe resulting from sudden valve closure, commonly known as waterhammer or hydraulic shock. The fluid behaves as a law power model. The basic equations are solved numerically by the characteristic method to obtain average pressure and velocity across a right sections of pipe and, a flow velocity profile by a Runge–Kutta scheme of fourth-order. The results of the present model agree suitably with those found in the literature [1]. This study highlights the remarkable effects of the properties of this fluids on the pressure oscillations generated by hydraulic waterhammer compared to fluids of Newtonian behavior.

Predictive Value of Electromechanical Window for Risk of Fatal Ventricular Arrhythmia.

As an indicator of electro-mechanical coupling, electromechanical window (EMW) can be used to predict fatal ventricular arrhythmias. We investigated the additive effect of EMW on the prediction of fatal ventricular arrhythmias in high-risk patients. We included patients who had implantable cardioverter-defibrillator (ICD) implanted for primary or secondary prevention. The event group was defined as those who received an appropriate ICD therapy. We acquired echocardiograms at ICD implantation and follow-up. The EMW was calculated as the difference between the interval from QRS onset to aortic valve closure and QT interval from the electrocardiogram embedded in the continuous wave doppler image. We evaluated the predictive value of EMW for predicting fatal ventricular arrhythmia. Of 245 patients (67.2 ± 12.8 years, 63.7% men), the event group was 20.0%. EMW at baseline (EMW-Baseline) and follow-up (EMW-FU) was significantly different between event and control groups. After adjustment, both EMW-Baseline (odds ratio [OR]adjust 1.02 [1.01-1.03], P = 0.004) and EMW-FU (ORadjust 1.06 [1.04-1.07], P < 0.001) remained as significant predictors for fatal arrhythmic events. Adding EMW-Baseline significantly improved the discriminating ability of the multivariable model including clinical variables (area under the curve [AUC] 0.77 [0.70-0.84] vs. AUC 0.72 [0.64-0.80], P = 0.004), while a univariable model using EMW-FU alone showed the best performance among models (AUC 0.87 [0.81-0.94], P = 0.060 against model with clinical variables; P = 0.030 against model with clinical variables and EMW-Baseline). The EMW could effectively predict severe ventricular arrhythmia in ICD implanted patients. This finding supports the importance of incorporating the electro-mechanical coupling index into the clinical practice for predicting future fatal arrhythmia events.

Study on the sealing test method of hydraulic solenoid valve in nuclear power station

In order to improve the reliability of tripping solenoid valve and switching solenoid valve of steam turbine valve in nuclear power plant and reduce abnormal valve closing. According to the working principle of valves in nuclear power plant, this paper designs a kind of electromagnetic valve sealing test system, including test base, measurement and control system and hydraulic system. The detection system is an offline system. By simulating the real load condition of the steam turbine system, the tightness of the tripping solenoid valve and the switching solenoid valve is tested to improve the reliability of the solenoid valve. The actual application results show that the system operates stably and reliably, is simple to operate, has high detection efficiency and accuracy, and has good use effect.