Large Valve Research Articles

Left Atrial Myxoma Revealed by a Stroke in a Young Female Patient

Introduction: Cardiac myxoma is a primary benign tumor most often located in the left atrium and it is a rare source of cerebral stroke of young subjects.
 Case Presentation: We report the case of a young women with cardiac myxoma revelated by hemiplegia.
 The patient suddenly presented vertigo followed by a fall, a heaviness of her left body, and dysarthria.
 Brain CT tomography and magnetic resonance imaging revealed cerebral ischemia in the right Sylvian territory. Transthoracic echocardiography revealed a round cardiac mass, mobile, heterogeneous, multilobed, appended to the interatrial septum and the atrial side of the large mitral valve by wide implantation, measuring 38 x 25mm in the parasternal short axis (PSAX) and apical 4 chamber views evocative of left atrium myxoma. After the surgical resection, which was postponed for a month, the removed tumor was sent for histopathological examination. The morphological examination revealed a myxoid tumor proliferation compatible with cardiac myxoma expressing calretinin by these tumor cells in the immunohistochemical study.
 Conclusion: Left atrium myxoma is a benign cardiac tumor and a rare cause of ischemic stroke. Transthoracic echocardiography facilitates the diagnosis of this tumor which will then be confirmed by histological analysis.

Downsizing, Use of Dummy and Venturi Valves Enhance Gas Lift Performance

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 213975, “Gas Lift Performance Enhancement Strategies by Downsizing and Using Dummy and Venturi Valves: A Paradigm Shift in Gas Lift Systems Management Philosophy,” by Wael F. Akeil, Ahmed M. El-Bohoty, and El-Sayed I. Abd El-Mawla, Gulf of Suez Petroleum Company, et al. The paper has not been peer reviewed. _ A mature offshore Egyptian field has entered a depletion phase. Most of its gas lift design bases were initiated during production startup and feature standardized sets of large gas lift valve port sizes with narrow spacing. Inconsistent well flow during reservoir depletion adds complications to the system. Therefore, a screenout model was created to select candidate wells for downsizing and for changing out with dummy and Venturi valves. After screening, 70 wells were selected for application of the new strategy. The complete paper discusses the effectiveness of smaller port sizes and the use of dummy and Venturi valves in enhancing gas lift performance and maximizing recovery. Field Background The field is divided into four main geographical quadrants, each with its own facilities. Total production currently is approximately 60,000 BOPD with an average water cut of 85%. Exploration and development of the field saw the drilling of more than 460 wells; half of these currently are experiencing reservoir pressure decline, drained reserves, or operational problems. Most wells are gas lifted, and the remainder either use electric submersible pump (ESP) installation or flow naturally. The facility consists of 73 offshore satellite platforms containing the wells—both oil producers and water injectors—connected to nine offshore complex platforms. As a part of continuous improvement trials, the operator reviewed the process of gas lift system management to introduce necessary improvements and recommend changes for long-term plans. The proposed amended management system was the result of monitoring, troubleshooting, and optimization activities outlined in the complete paper. Amended Gas Lift Management System Using Dummy Valves in Gas Lift System. Conceptual Phase. A dummy valve is a special gas lift valve shaped like solid metallic bar with upper and lower packings. They are installed to replace unloading valves that are no longer needed. Installing dummy valves instead of the unloading valves can reduce problems such as valve interference and deepens the point of gas injection. Redesign Procedure Based on the New Production Profile. This practice can be applied in two main cases: First, if reservoir pressure has declined and the well is producing with a lower rate but the surface injection pressure is still high enough to reach deeper valves; and, second, if the well is planned to be recompleted from one formation to another that has a higher reservoir pressure but with lower formation feed as the result of lower productivity. The main steps for redesign are provided in the complete paper.

Short- and Medium-Term Outcomes Comparison of Native- and Valve-in-Valve TAVI Procedures.

In high-risk patients with degenerated aortic bioprostheses, valve-in-valve (ViV) transcatheter aortic valve implantation (TAVI) has emerged as a less invasive alternative to surgical valve replacement. To compare outcomes of ViV and native valve (NV) TAVI procedures. 34 aortic ViV-TAVI performed between 2012 and 2022 using self-expanding valves, were included in this retrospective analysis. Propensity score matching (1:2 ratio, 19 criteria) was used to select a comparison NV-TAVI group from a database of 1206 TAVI procedures. Clinical and echocardiographic endpoints, short- and long-term all-cause mortality (ACM) and cardiovascular mortality (CVM) data were obtained. Subgroup analyses were completed according to the true internal diameter, dividing patients into a small ( 19 mm) valve group (SVG) and a large ( 19 mm) valve group (LVG). Clinical outcomes of ViV- and NV-TAVI were comparable, including device success [88.2% vs. 91.1%, p = 0.727], major adverse cardiovascular and cerebrovascular events [5.8% vs. 5.8%, p = 1.000], hemodialysis need [5.8% vs. 2.9%, p = 0.599], pacemaker need [2.9% vs. 11.7%, p = 0.265], major vascular complications [2.9% vs. 1.4%, p = 1.000], life-threatening or major bleeding [2.9% vs. 1.4%, p = 1.000] and in-hospital mortality [8.8% vs. 5.9%, p = 0.556]. There was a significant difference in the immediate post-intervention mean residual aortic valve gradient (MAVG) [14.6 8.5 mm Hg vs. 6.4 4.5 mm Hg, p 0.0001], which persisted at 1 year [p = 0.0002]. There were no differences in 12- or 30-month ACM [11.8% vs. 8.8%, p = 0.588; 23.5% vs. 27.9%, p = 0.948], and CVM [11.8% vs. 7.3%, p = 0.441; 23.5% vs. 16.2%, p = 0.239]. Lastly, there was no difference in CVM at 1 year and 30 months [11.1% vs. 12.5%, p = 0.889; 22.2% vs. 25.0%, p = 0.742]. Analyzing a limited group (n = 34) of ViV-TAVI procedures out of 1206 TAVIs done at a single institution, ViV-TAVI appeared to be an acceptable approach in patients not deemed appropriate candidates for redo valve replacement surgery. Clinical outcomes of ViV-TAVI were comparable to TAVI for native valve stenosis.

A study on the condition assessment of large diameter water valves using non-destructive technologies

A study on the condition assessment of large diameter water valves using non-destructive technologies

Internal Carotid Artery Occlusion as a Rare Presentation of Infectious Endocarditis: A Case Report.

Internal carotid artery occlusion as a result of a septic embolism is a rare, commonly fatal, complication of mitral valve infectious endocarditis. Prompt recognition of this condition by the emergency physician may improve the chance of functional neurological survival. A 50-year-old male presented minimally responsive with a right gaze deviation, left hemiparesis, and a score of 26 on the National Institutes of Health Stroke Scale. A point-of-care echocardiogram showed a large mitral valve vegetation, and computed tomography angiography demonstrated an internal carotid artery occlusion. The emergency physician should consider this potentially life-threatening condition and know the fundamental management recommendations once identified.

3D bioprinting for vascular grafts and microvasculature

Cardiovascular disease is the world’s leading cause of death, and there is a substantial clinical need for transplantable blood vessels. Through tissue vascular engineering technology, large blood vessel grafts with significant clinical effects have been synthesized. However, synthesizing vascular valves, small vessels up to 6 mm in diameter, and capillary networks up to 500 μm in diameter remains challenging due to the lack of precise manufacturing techniques. In particular, constructing a microvascular network in thick tissue is the technical bottleneck of organ transplantation. Three-dimensional (3D) bioprinting is a computer-assisted layer-by-layer deposition method that can deposit cells and biomaterials at a predetermined location, according to an accurate digital 3D model, to build a delicate and complex bionic structure. This review discusses the progress and limitations of 3D bioprinting in preparing large vessels and valves, small-diameter vessels, and microvascular networks. This paper focuses on improved printing technology and innovative bio-ink materials. The future application of 3D bioprinting is prospected in generating artificial blood vessel grafts and vascularized organs with full biological function.  

Transcatheter transseptal treatment of patients with severe mitral regurgitation using an atrial fixation mitral valve replacement technology

BackgroundMitral regurgitation (MR) is the most common valvular heart disease worldwide with a 5-year mortality rate of 50 % with medical therapy alone. Several transcatheter mitral valve replacement (TMVR) devices are being investigated in clinical trials. Early evidence has demonstrated clinical benefits with a reduction in heart failure symptoms, low rates of residual MR, and reverse remodeling of the left ventricle (LV) over time. However, high anatomical screen failure rates limit its applicability. The primary reasons for the anatomical screen failure are risk of LV outflow tract obstruction, large mitral valve annulus size, and the presence of mitral annular calcification. Our clinical experiences using an atrial only fixation TMVR technology delivered via a transfemoral-transseptal approach is described. MethodsThree consecutive patients with severe functional MR underwent TMVR implantation using an atrial only fixation technology and a low-profile transseptal delivery system. ResultsTechnical success was achieved in 100 % of the patients with a clinically significant reduction in MR. Longer-term follow-up (up to 6-months) has demonstrated a sustained reduction in MR and significant improvement in quality of life for all patients. ConclusionsLonger-term outcomes in our patients showed persistent reduction in MR, sustained implant performance, and notable improvements in NYHA Class and quality of life. There were no major adverse events. Follow-up CT data showed no evidence of device-related thrombosis, with stable valve position and integrity. The atrial fixation TMVR technology may have benefits in preserving the dynamics of the native mitral valve annulus thereby reducing the overall risk of LVOT obstruction. Short AbstractWe present a single-center experience of three consecutive patients with severe functional MR treated with the AltaValve using a low-profile transseptal delivery system. A clinically significant reduction in mitral regurgitation was achieved in all patients, and longer-term follow-up has demonstrated sustained clinical benefits.

Anévrysme rénal infectieux retardé, 3 mois après chirurgie cardiaque pour une endocardite infectieuse à Streptococcus pyogenes ; cas et revue de la littérature

Infective endocarditis (IE) due to Streptococcus pyogenes (SP) (Group A Streptococcus) is uncommon and infectious renal artery aneurysm (IRAA) is an exceptional complication of IE, with few cases reported in the literature.We describe a case of SP native mitral valve IE in a 58-year-old man, presenting with large valve vegetations, abscess and severe regurgitation. Initial CT-angiography showed bilateral kidney and splenic infarcts.He underwent successful emergent bioprosthetic valve replacement. Antibiotic regimen consisted in linezolid and rifampicin for 8 weeks. Three months later, CT-angiography for feet gangrene revealed a 16mm aneurysm of the left intraparenchymal renal artery, which was occluded by coil-embolization.This case shows that an infectious aneurysm may develop several months after antibiotic treatment and emergent valve replacement for IE.

Prominent Eustachian Valve Complicated by Thrombus

The Eustachian valve is an embryological remnant of the valve of the inferior vena cava. It may be prominent in some individuals, but the echocardiographic appearance of a divided right atrium (RA) as a result of a large Eustachian valve is rare. Sometimes it presents a problem of differential diagnosis with other embryonic remnants of the right atrium, such as the Chiari network. It may be complicated by thrombosis or infective endocarditis. Cardiac imaging plays an important role in diagnosis. The aim of this review is to discuss a rare form of Eustachian valve complicated by thrombosis.

Flow Field Characteristics and Structure Improvement of Double-stage Safety Valve

The paper proposes a new double-stage large flow protection relief valve based on the double-stage linkage structure, to solve the problem that when it is impacted by the top plate, the traditional hydraulic support protective relief valve has smaller overflow and lower sensitivity, which causes the column circuit to be damaged. The flow field characteristics of double-stage protective relief valve are numerically simulated by the computational fluid dynamics method and semi-implicit connection pressure equation calculation model. Then the dynamic characteristics of the flow field distribution of the double-stage protective relief valve are obtained. According to the law of fluid flow, the structure of main valve core is optimized for the negative pressure, cavitation and vortex area. The flow field characteristics of the optimized double-stage protection valve are simulated and analyzed. In the end, the flow field characteristics of optimized double-stage protective relief valve are compared with the original. The results show that the negative pressure value of double-stage protective relief valve is reduced by 15%, and the outlet velocity of double-stage protective relief valve is reduced by 21% compared to the unoptimized when the main core is fully opened. The research results provide reference for the evolution design of high-flow, impact-resistant hydraulic support safety valve structure.

Life Story of a Mycotic Pulmonary Artery Aneurysm

A 29-year-old woman with a history of IV heroin use presented to the emergency department with hemoptysis. Prior to admission, she had a large tricuspid valve vegetation with embolism to the left lower lobe (Figure 1A). At that time, she had an embolic event to the right lower lobe pulmonary artery (Figure 1B) and underwent tricuspid valvuloplasty. Intraoperative microbiology confirmed Candida albicans.

Effects of the Volume Fraction of the Secondary Phase after Solution Annealing on Electrochemical Properties of Super Duplex Stainless Steel UNS S32750

Super duplex stainless steel (SDSS) is used for manufacturing large valves and pipes in offshore plants because of its excellent strength and corrosion resistance. Large valves and pipes are manufactured by forging after casting, and the outside and inside microstructures are different owing to the difference in the cooling rate caused by the thermal conductivity. This microstructural variation causes cracks during solution annealing, which breaks the materials. To study the corrosion resistance of the SDSS forged material, the influence of the microstructure according to the difference between the inside and outside cooling rates of the cast SDSS was evaluated. To analyze the effects of the secondary phase fraction before solution annealing on the solution and corrosion resistance, the corrosion resistance with and without solution annealing was measured using the potentiodynamic polarization test and critical temperature test after the precipitation of the secondary phase. In the potentiodynamic polarization test, the secondary phase decreased the activation polarization and increased the corrosion rate. The critical pitting temperature exhibited the effect of the secondary phase.

Abstract 165: Large Extracellular Vesicles-derived MicroRNA-150-5p Is Upregulated In Patients With Aortic Valve Stenosis And Regulates Valvular Endothelial Cell Function

Aortic valve stenosis (AVS) is the most common type of valvular disease. Recent evidence indicates that extracellular vesicles (EVs) might play an important role in cardiovascular disease, particularly AVS. However, the contribution of EV-encapsulated microRNAs (miRNAs) in valvular endothelial cells (VECs) and AVS has been poorly investigated. Herein, we identified the differentially expressed miRNAs in large EV-derived aortic valve tissue from patients with AVS and explored the novel role of miR-150-5p in endothelial to mesenchymal transition (EndMT). Our miRNA sequencing revealed several EV-miRNAs (miRNA-150-5p, miR-486-5p, and miR-486-3p) were significantly dysregulated in large EVs from aortic valve tissue in patients with AVS. In silico analysis indicated that miRNA-150-5p is mainly enriched in Wnt, TGF-β, and PI3k/AKT signaling pathways, known to be altered in the pathogenesis of AVS. To elucidate the role of miR-150-5p in AVS, we validated the upregulation of miR-150-5p in AVS patients by RT-qPCR. Importantly, the overexpression of miR-150-5p in VECs treated with TNF-α reduced EndMT, which was quantized by significant expression of EndMT markers (vWF, ACTA1, VIM, and SLUG). To investigate the role of miRNA-150-5p in VEC function, cell migration and tube formation were performed. The data revealed that miR-150-5p regulates VEC function via increased tube formation and reduced cell migration. To further investigate VEC function under the laminar flow, which regulates EC function, we exposed VEC under the flow and found that the expression of miR-150-5p is increased suggesting a protective role in VECs. To study the role of miR-150-5p in intercellular communication, we overexpressed miR-150-5p in donor VECs and incubated them with recipient VECs prior to the labeling of EVs with PKH67. Fluorescent microscopy showed an increased expression of miR-150-5p in recipient VECs. Further, we induced EndMT in VECs after co-incubation with EVs (miR-150-5p overexpression vs. control). Our qPCR-analysis revealed that EV-miR-150-5p rescued the expression of EndMT markers. Our data showed that large EV-associated miR-150-5p was significantly upregulated in AVS and may play a crucial role in cellular crosstalk via regulating function of VEC via EndMT.

PO-02-081 PERCUTANEOUS REMOVAL OF LARGE VEGETATION FACILITATES SAFE TRANSCUTANEOUS LEAD EXTRACTION: A SINGLE CENTER EXPERIENCE

Infective endocarditis (IE) is the most common indication for transvenous lead extraction (TLE), and it is associated with significant morbidity and mortality. Complete removal of the device in addition to antibiotics is required, however large vegetations (>2-3cm) on either the lead or the tricuspid valve confer a high risk of vegetation embolization with standard lead extraction. Vegetation size larger than 2cm appear to have higher incidence of intraprocedural clinically significant pulmonary embolism. An open surgical approach is usually recommended in this situation to mitigate the risk of embolization, however, surgical extraction is associated with increased morbidity/mortality and in some patients the risk is prohibitive. Percutaneous approach to remove large vegetations from tricuspid valve has been reported to be safe in several recent case reports The purpose of our study is to describe our single-center experience of the management of patients with a large vegetation involving the leads and/or the tricuspid valve. The use of percutaneous tricuspid valve/lead vegetation removal permitted or facilitated successful TLE avoiding cardiothoracic surgery We reviewed the perioperative course of 5 consecutive patients with large tricuspid valve and/or lead vegetation referred for device/lead extraction due to endocarditis. Patients with large vegetations considered at increased risk of embolization with transcutaneous extraction were referred for percutaneous vegectomy prior to TLE. Vegectomy procedure is done at our institution using the percutaneous catheter-based system FlowTriever aspiration catheter with FLEX technology (Inari Medical, Irvine, CA USA) with the guidance of intracardiac echocardiogram through femoral vein access (Figure 1). Over a 15-month period, 5 patients presented with large vegetations that precluded TLE due to embolization risk. Four patients (80%) were male, with an average age of 60 years, and the average vegetation size was 2.7 cm (2.4-3.2 cm). All patients underwent vegectomy followed by lead extraction as a staged procedure without complication. All patients survived the index hospitalization (see Table 1 for details) Percutaneous removal of large tricuspid valve/lead vegetations prior to lead extraction is a safe and effective way to manage patient with endocarditis and large vegetations thereby avoiding the morbidity and mortality associated with open heart surgeryTabled 1Table 1Patient #Age (years)Device Type# of LeadsOrganismVegetation Size (cm)Vegetation LocationComplications166CRT-D3MSSA2.5RV LeadNone263DC PPM2No growth2.4RA/RV LeadNone368CRT-D (HIS Lead)3Streptococcus2.5RA LeadNone456ICD (Dual Coil)1Corynebacterium3.0RV Lead/TVNone548DC PPM2MRSA3.2RA LeadNoneCRT-D: Cardiac resynchronization therapy – defibrillator; MSSA: Methicillin sensitive staph aureus; RV: right ventricular; DC PPM: Dual chamber permanent pacemaker; RA: right atrial; ICD: implantable cardioverter defibrillator; MRSA: Methicillin resistant staph aureus; TV: Tricuspid valve Open table in a new tab

Penicillin-resistant gonorrheal endocarditis presenting with large annular abscess and aortic valve destruction

Disseminated gonorrheal infections with cardiac involvement are rare, with fewer than 100 cases reported. The increasing prevalence of gonococcal infections and increasing antibiotic resistance represent a concerning challenge to public health. Here we report a case of antibiotic-resistant gonococcal endocarditis presenting with cardiogenic shock and discuss principles of diagnosis and treatment.

Comparison of 1-year Follow-up Echocardiographic Outcomes of Sapien 3 Versus Evolut R Bioprosthetic Transcatheter Aortic Valves: A Single-center Retrospective Iranian Cohort Study.

The current study aimed to compare 1-year echocardiographic outcomes of the new generations of self-expanding (Evolut R) versus balloon-expandable (Sapien 3) bioprosthetic transcatheter aortic valves. In this study, gradients and flow velocities obtained from transthoracic Doppler-echocardiography were retrospectively collected from patients who underwent 2 new generations of transcatheter aortic valve implantation interventions with Sapien 3 and Evolut R valves. Patients underwent echocardiography before the procedure and at discharge, 6 months, and 1-year follow-up. Of the 66 patients, 28 received Sapien 3 and 38 received Evolut R valves. Evolut R valve presented a lower mean gradient at all follow-up time points compared with Sapien 3 valves (14.4 mm Hg, 14.9 mm Hg, 15.5 mm Hg compared with 10.1 mm Hg, 11.6 mm Hg, 11.8 mm Hg, respectively; all P -values <0.001). Small valve sizes of Evolut R, including 23 and 26, had higher echocardiographic mean gradient or peak gradient at the time of discharge compared with larger valves, including sizes 29 and 34 (11.1 mm Hg and 11.2 mm Hg vs. 10.2 mm Hg, 9.1 mm Hg) and 1-year follow-up (11.0 mm Hg, 11.0 mm Hg vs. 9.9 mm Hg, 8.4 mm Hg; all P -values = 0.001). Although Sapien 3 valves demonstrated a higher peak gradient in smaller sizes at discharge (18.44 mm Hg in size 23 vs. 17.9 mm Hg, 16.5 mm Hg in size 26 and 29, respectively; P = 0.001), the peak gradients did not show a statistically significant difference in the 1-year follow-up. The current study detected significantly lower mean and peak gradients in Evolut R compared with Sapien 3 at all follow-up time points. Furthermore, smaller valve sizes were associated with significantly higher gradients at all follow-ups, regardless of the valve type.

Hot spot imaging in cardiovascular diseases: an information statement from SNMMI, ASNC, and EANM

This information statement from the Society of Nuclear Medicine and Molecular Imaging, American Society of Nuclear Cardiology, and European Association of Nuclear Medicine describes the performance, interpretation, and reporting of hot spot imaging in nuclear cardiology. The field of nuclear cardiology has historically focused on cold spot imaging for the interpretation of myocardial ischemia and infarction. Hot spot imaging has been an important part of nuclear medicine, particularly for oncology or infection indications, and the use of hot spot imaging in nuclear cardiology continues to expand. This document focuses on image acquisition and processing, methods of quantification, indications, protocols, and reporting of hot spot imaging. Indications discussed include myocardial viability, myocardial inflammation, device or valve infection, large vessel vasculitis, valve calcification and vulnerable plaques, and cardiac amyloidosis. This document contextualizes the foundations of image quantification and highlights reporting in each indication for the cardiac nuclear imager.

Are large ileocecal valve lesions amenable with advanced endoscopic management to avoid bowel resection?

Mucosal lesions located at the ileocecal valve may be challenging for endoscopic intervention because of angulated anatomy and a thinner wall with narrower lumen when compared to other locations of the bowel. This study aimed to evaluate the management and outcomes of ileocecal valve lesions treated endoscopically. Patients with mucosal neoplasms involving the ileocecal valve managed with advanced endoscopy at a quaternary care hospital between 2011 and 2021 were included from a prospectively collected database. Patient demographics, lesion characteristics, complications, and outcomes are reported. From 1005 lesions, 80 patients (8%) underwent resection for neoplasms involving ileocecal valve by ESD (n = 38), hybrid ESD (n = 38), EMR (n = 2), and CELS (n = 2). The median age of the study group was 63(37-84) years, and 50% of patients were female. The median lesion size was 34mm (5-75). The mean procedure time was 66 ± 44min(range:18-200). The dissection was completed as piecemeal in 41(51%) patients and 35(44%) had en-bloc dissection. Seven(8%) endoscopic interventions required conversion to laparoscopic surgery due to inability to lift the mucosa(n = 4) and perforation(n = 3). No immediate bleeding occurred in the study group. Five patients had late rectal bleeding and two were admitted with post-polypectomy pain within 30days of intervention. Pathology revealed 4(5%) adenocarcinomas, 33(41.2%) tubular adenomas, 30(37.8%) tubulovillous adenomas, and 5(6.2%) sessile serrated adenomas. Sixty-seven (84.5%) patients completed at least one follow-up colonoscopy and were followed for a median of 11(0-64) months. Six (8.9%) patients had recurrence and were managed with subsequent endoscopic removal. Advanced endoscopy can be safely and effectively performed for the management of ileocecal valve polyps with low complication and acceptable recurrence rates. Advanced endoscopy promises an alternative approach to oncologic ileocecal resection while attaining organ preservation. Our study demonstrates the impact of advanced endoscopy for the treatment of mucosal neoplasms involving ileocecal valve.

Investigation of the Fluid Flow in a Large Ball Valve Designed for Natural Gas Pipelines

Natural gas pipeline networks used for long-distance transportation are expanding quickly, and the construction of special valves with large diameters has especially increased since 2022. The design and manufacturing of the flow control equipment is carried out on a case-by-case basis, in accordance with the parameters required by the beneficiary. In this paper, results obtained by fluid flow simulation with SolidWorks2023 software for a 500 mm diameter trunnion ball valve lead to important information regarding how the fluid flow develops in the intermediary and fully closed positions. The large inner space of the ball allows the development of high-amplitude vortices; thus, the simulation demonstrates that the shut-on/off operation of large-diameter ball valves is mandatory to avoid fast destruction following partial opening. This paper also demonstrates why the metal–metal (MM) sealing with a double-piston effect (DPE) design for seats produces low leakage rates, including for the shut-off position; the pressure field reveals that few gas particles succeed in crossing the upstream sealing zone, and even fewer cross the downstream sealing zone. Additionally, the interpretation of the results explains and highlights the importance of using seats with a DPE design to achieve fire safety, which is required for natural gas pipeline applications.

Multi-objective optimization of two-stroke compression release braking performance of a heavy-duty engine based on non-dominated sorting genetic algorithm II (NSGA II)

Traditional heavy-duty vehicle service brakes use the friction method to realize vehicle deceleration, which means that longer-term use of the service brake will lead to overheating. It will make the braking capacity significantly reduced, at the same time, the service brake system also will wear much faster. Engine brake has been developed continuously in recent decades since it has the advantages of small install space and weight, no attenuation of braking power, rapid response, and endurance braking. However, the complex structure and large valve load of the valve train are the main obstacles to the widespread use of two-stroke compression release braking. Two-stroke compression release braking power is the effective indicator of the braking capacity and the maximum cylinder pressure (Pmax) can reflect the load of the valve train, therefore, the braking power and Pmax need to be optimized at the same time. In this paper, the multi-objective non-dominated sorting genetic algorithm II (NSGA II) was introduced to optimize the two-stroke compression release braking performance and it was compared with the orthogonal design method. The results indicated that the braking power and Pmax of optimal solution 1 by NSGA II achieved −395.64 kW and 59.37 bar, which were 1.17% and 2.78% improved than that of orthogonal analysis, respectively. In addition, the calculation process shows that NSGA II provides a more comprehensive and reliable method to optimize the valve parameters of the two-stroke compression release brake.