This paper reports a study on the effect of helical, spiral, and helical-spiral combination manifold configuration on air motion and turbulence inside the cylinder of a Direct Injection (DI) diesel engine motored at 3000 rpm. Three-dimensional model of the manifolds and the cylinder is created and meshed using the pre-processor GAMBIT. The flow characteristics of these engine manifolds are examined under transient conditions using Computational Fluid Dynamics (CFD) code STAR-CD. The predicted CFD results of mean swirl velocity of the engine at different locations inside the combustion chamber at the end of compression stroke are compared with experimental results available in the literature. We also compared the volumetric efficiency of the modeled helical manifold. The results obtained showed reasonably good agreement with the measured data given in the literature. Further, this paper discusses the predicted flow structure, swirl velocity and variation of turbulent energy inside the cylinder with different manifold. Comparisons of volumetric efficiency with different manifold configuration at 3000 rpm speed are also presented. The turbulence is modeled using RNG k-ε model. It is observed that helical-spiral manifold gives the maximum swirl ratio inside the cylinder than helical manifold. But volumetric efficiency observed is less for helical-spiral manifold engine. Swirl inside the engine is important for diesel engine. Hence, for better performance a helical-spiral inlet manifold configuration is recommended.
Background:Atherosclerotic carotid artery disease poses a grave threat to cerebral circulation, leading to a stroke with its devastating sequelae, if left untreated. Carotid endarterectomy has a proven track record with compelling evidence in stroke prevention.Objectives:a) To confirm that carotid endarterectomy (CEA) is safe and effective in preventing stroke at both short and long term. b) to demonstrate long term patency of internal carotid artery when arteriotomy repair is performed using autologous saphenous vein patch.Materials and Methods:During ten years, from September 1997 to February 2008, thirty nine patients who underwent consecutive carotid endarterectomy at our institute, form the basis of this report. Their age ranged from thirty to seventy eight years, with a mean age of 56. There were four women in this cohort. Thirty seven patients were symptomatic with >70% stenosis and two were asymptomatic with >80% stenosis, incidentally detected. Imaging included Duplex scan and MRA for carotid territory and brain, and non-invasive cardiac assessment. Co-morbidities included smoking, hypertension, diabetes, and coronary artery disease. Carotid Endarterectomy was performed under general anaesthesia, using carotid shunt and vein patch arteriotomy repair.Results:All the patients made satisfactory recovery, without major adverse cerebral events in this series. Morbidities included Transient Ischemic Attack (TIA) in two, needing only medications in one, and carotid stenting in the other. Minor morbidities included neck hematoma in two and transient hypoglossal paresis in three patients. Yearly follow-up included duplex scan assessment for all the patients. Two patients died of contralateral stroke, two of myocardial events and two were lost to follow up. Thirty three patients are well and free of the disease during the follow up of three to 120 months.Conclusion:Carotid endarterectomy provided near total freedom from adverse cerebral events and its catastrophic sequelae, leading to excellent outcome, both short as well as long term.
Cerebral venous sinus thrombosis (CVST) is quite an unusual diagnosis in pregnancy and puerperium. It can present with a wide range of symptoms and signs, and a high index of suspicion is required to diagnose this disorder. The diagnosis is challenging and could if left undiagnosed, result in life-threatening complications. Yet its management is simple with excellent prognosis, with an early diagnosis and timely intervention. We report a case of CVST in a young pregnant patient who presented with features of raised intracranial tension and loss of consciousness, after several weeks of hyperemesis gravidarum. She was treated with intravenous fluid resuscitation, low molecular weight heparin, steroids, and anti-cerebral edema measures. She subsequently made excellent recovery and is under follow-up.
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