دانلود ترجمه مقاله بهینه سازی نامتقارن توربین توربوشارژ با عملکرد پالس EGR

• فهرست مطالب:

چکیده
۱ مقدمه
۲ تئوری پایه
الف معادلات حاکم
ب خواص گاز واقعی
ج عملکرد
د مدل سازی اغتشاشی
هـ استراتژی راه حل
۳ راه اندازی آزمایش
۴ راه اندازی مدل
الف مدل سازی
ب مطالعه شبکه
ج دیواره نزدیک
د شرایط مرزی
۵ نتایج
۶ نتیجه گیری

• بخشی از ترجمه:

در اين مقاله طراحي و ارزيابي عملكرد يك توربين با هندسه متغير دوورودي نامتقارن مورد بحث قرار گرفت. اين طراحي توربين براي بهبود عمليات EGR موتور و افزايش استخراج انرژي از اگزوز در موتورهاي چندسيلندر بزرگ است. طراحي با تجزيه و تحليل ميانگين خط اوليه به منظور رفع پارامترهاي عمومي هندسي توربين آغاز شده، سپس طراحي كامل توربين توسط مدلسازي سه بعدي CFD مورد ارزيابي قرار گرفت. به عنوان يك نتيجه از اين فرايند، توربين به صورت نا متقارن با دو ورودي با مقادير ۱۶۰-۲۰۰، ۱۰% نسبت نرخ EGR را داشته و پره هندسه متغير دزر توربين تك ورودي استخراج جريان EGR را داشته است.
شبيه سازي براي تعدادي از سرعت هاي توربين مختلف در ۱۰۰% و ۵۰% سرعتها، مقادير SPR 0.5 و ۱٫۵ و زاويه پره -۱۰۰ و ۰۰ و +۱۰۰ را نشان مي دهد. نتايج شبيه سازي نشان داد كه نقطه اوج بهره وري تحت SPR مي تواند رخ دهد كه با كارايي ۷۸% تا ۱۰۰% توربين بوده و نرخ EGR،۲۰% مي باشد. و بهره وري مشاهده شده در ۵۰% سرعت با اوج بازده به مقدار ۷۶% بوده است. همچنين پيكربندي پره مي تواند براي نرخ هاي EGR مختلف امكان بهينه سازي شرايط جريان در ورودي به توربين را نشان دهد كه ممكن است براي حفظ شرايط پذيرش برابر بوده و از اين رو كارايي توربين بهينه براي طيف گسترده اي از EGR خواهد بود.

• بخشی از مقاله انگلیسی:

INTRODUCTION AND PROBLEM DEFINITION Due to the increasingly stringent emission regulations and demand for high fuel economy, turbocharger is inherently one of the most promising enabling technologies towards achieving engine design for low emissions and fuel consumption. Turbochargers are not only expected to provide efficient exhausts energy recovery, but they are also used in order to support engine operation by controlling engine back-pressure for enhanced EGR rate. In large multi-cylinder engines, single-entry VGTs are normally used due to their ability to support EGR and instantaneous boost pressure response. However, the disadvantage of singleentry VGTs is that they do not enable to maximize energy extraction out of the exhausts pulses (pulse turbocharging) since there is no pulse separation within the turbine volute (as in multiple-entry turbines). Hence, aim of this research, is that of combining the advantages of exhausts pulse energy extraction and variable geometry turbocharging in one single turbine design. Pulse turbocharging (i.e. conserving pulse energy until the rotor entry) is a wellknown technique to utilise the maximum energy of the exhausts. In order to avoid exhausts pulse interference, these are isolated with multiple-entry turbines. Two types of multiple-entry turbines are currently available in the market: meridionally divided “twin-entry” turbines and circumferentially divided “double-entry” turbines (Figure 1). The twin-entry turbine is divided meridionally and each incoming flow is fed into the entire rotor circumference. In contrast, double-entry turbine feeding area is divided circumferentially and incoming flows are guided with radially In order to merge the requirements of imbalanced mass flow and the pulse turbocharging advantage, asymmetric vaneless twin-entry turbine design has been proposed by Müller et al. (2) and lately optimized by Brinkert et al. (3). Their work showed that it is possible to achieve remarkable EGR-rates in some regions of the engine map, even though the average exhausts back-pressure is lower than the charge air pressure thus limiting the operations for this design. A different approach than that provided by (2) and (3) is proposed in the current paper, with the design of an asymmetric variable geometry double-entry turbine. The reasons for the selection of this turbine configuration are explained as follows. In order to extract exhaust gases and recirculate it into the intake side, exhaust manifold pressure has to be higher than the intake manifold pressure. Therefore a VGT is necessary to increase exhaust manifold pressure corresponding with widely changeable transient operation. Besides supporting EGR control strategies by changing exhaust manifold pressure, VGT also offers the additional advantage of varying the inlet area to the turbine wheel thus maximizing exhausts flow energy extraction at different engine operating conditions. The choice of asymmetric (a) (b) Outer limb Inner limb Entry 2 Entry 1 322 double-entry geometry in place of a twin-entry one can be explained by considering that adopting symmetrically divided multiple-entry turbines in EGR engines, would lead to an imbalance of mass flow caused by EGR extraction from one side of the exhausts manifold. This flow imbalance can hardly be controlled in twin-entry turbines since the flow leaving the two entries mix together before entering the wheel. This is not the case in double-entry turbine configuration since the flows from the two entries are completely isolated and introduced into the turbine wheel separately, so that the flow controllability is believed to be more effective than in twin-entry turbine. A typical arrangement for the asymmetric variable geometry double-entry turbine is given in Figure 2. More details are provided in the next paragraph.