بررسی اثر حذف صداخفه‌‌کن‌‌های اگزوز توربین گازی بر روی جریان ورودی به بویلر بازیاب یک نیروگاه سیکل ترکیبی

در این پژوهش سیستم اگزوز یک نیروگاه سیکل ترکیبی با استفاده از روش عددی برای دو وضعیت سیکل ترکیبی و گازی مورد مطالعه قرار گرفته است. فشار پایین دست (در قسمت اگزوز) نقش مهمی را در تعیین بازدهی نیروگاه ایفا می‌‌کند. مکان صداخفه‌‌کن در سیستم اگزوز نیروگاه قبل از دایورتر دمپر می‌‌باشد که باعث افزایش افت فشار 75.62 پاسکال نسبت به سیستم اگزوز برای وضعیت سیکل ترکیبی می‌‌شود. در این پژوهش، صداخفه‌‌کن به داخل استک اگزوز کنارگذر انتقال داده شد که در وضعیت سیکل ترکیبی باعث کاهش افت فشار به میزان 478.21 پاسکال و غیریکنواخت شدن سرعت جریان خروجی اگزوز (ورودی به بویلر بازیاب) و افزایش افت فشار به میزان 318.23 پاسکال در وضعیت سیکل گازی شد. به منظور یکنواخت شدن سرعت خروجی در این سیستم اگزوز دو طرح اصلاحی مطالعه شده است. در طرح اول طول کانال انبساطی افزایش داده شد که باعث کاهش افت فشار به میزان 97 درصد و یکنواخت شدن سرعت خروجی در وضعیت سیکل ترکیبی شده است. در طرح دوم از صفحه‌‌ی مشبک درون کانال انبساطی استفاده شد که باعث افزایش افت فشار برابر 219.54 پاسکال در سیستم اگزوز جدید نسبت به طرح اول در حالت سیکل ترکیبی و یکنواخت شدن سرعت خروجی اگزوز شده است. 

investigating the effect of removing gas turbine exhaust silencers on the input flow to the recovery boiler of a combined cycle power plant

this study analyzes and evaluates the effect of relocating the silencers of the exhaust system of the alstom single-pressure, combined-cycle power plant in yazd. the exhaust system design should minimize both pressure drops and ensure a uniform flow at its outlet (the inlet to the recuperator boiler). analysis of the yazd power plant exhaust system in the combined-cycle state indicates that vortices form in the divergent channel preceding the silencer, while the outlet flow remains uniform. the total pressure drop is 535.71 pa.for the gas-turbine cycle, vortices form in the divergent channel and in the by-pass exhaust stack, with a total pressure drop of 611.33 pa. relocating the silencers inside the by-pass exhaust stack reduces the pressure drop caused by their presence in the gas inlet to the recuperator boiler; however, the flow becomes highly non-uniform, and a large vortex region with circulating flow develops within the exhaust system. the inlet static pressure decreases to 467.61 pa and the total pressure drop becomes 57.5 pa. for the gas-turbine state, analogous to the combined-cycle, flow uniformity deteriorates and a vortex region with substantial circulating flow forms within the diverging channel. the total pressure drop for this condition is 929.56 pa.relocating the silencers yields no perceptible reduction in pressure drop in the combined-cycle and has no substantial effect on efficiency. however, silencer life increases, and accessibility for maintenance improves. implementing this modification in the exhaust system should be performed by experienced personnel, and, upon validation of its value, geometry refinements to achieve flow uniformity should be made; otherwise, particularly in the combined-cycle, the non-uniform flow could degrade the recuperator heat exchangers and affect recuperator performance. to achieve flow uniformity inside the exhaust, two modification schemes were proposed and evaluated.modification plan 1: the length of the divergent channel is increased, which reduces the channel divergence angle. as a result, the flow in the combined-cycle becomes uniform, and the inlet static pressure relative to the present exhaust system decreases by 518.6 pa, with a total pressure drop of 16.24 pa. this modification did not affect the gas-turbine cycle, where the flow remains non-uniform. the inlet static pressure for the exhaust in this state relative to the present system increases by 275.45 pa, and the total pressure drop for this geometry is 929.56 pa. this plan entails a high implementation cost because a new divergent channel must be constructed.modification plan 2: a perforated plate is placed in the center of the divergent channel. with this modification, the flow in the combined-cycle becomes uniform, and the vortices caused by silencer relocation diminish. the inlet static pressure relative to the present system decreases by 299.62 pa, and the total pressure drop is 235.78 pa. this modification is effective for the gas-turbine cycle, yielding a more uniform flow. the inlet static pressure relative to the present system increases by 360.33 pa, and the total pressure drop for this geometry is 988.6 pa. although this modification reduces pressure drop in the combined-cycle compared with the previous state, its advantage lies in lower implementation cost.