تشخیص ناپایداری شعله در مشعل پیش آمیخته شعله سطحی با استفاده از تحلیل فرکانسی

نوع مقاله: مقاله پژوهشی

نویسندگان

1 تربیت مدرس فارغ التحصیل رشته مهندسی مکانیک

2 تربیت مدرس مهندسی مکانیک

چکیده

در این پژوهش، با استفاده از حسگر نوری و سیستم داده ­برداری، به بررسی پایداری مشعل شعله ­سطحی پرداخته می­ شود. نوسانات شدت نور توسط حسگر نوری اندازه­ گیری و سپس، با استفاده از تبدیل فوریه سریع، از فضای زمانی به فضای فرکانسی انتقال داده شد و از منحنی پاسخ فرکانسی، فرکانس طبیعی نوسانات استخراج شد. برای اینکه بتوانیم رفتار دینامیک را برای شعله پیش ­آمیخته نشان دهیم، شعله­ های پیش ­آمیخته به دو ناحیه شعله های سلولی و شعله­ های مسطح تقسیم­ بندی می­ شوند. این تقسیم ­بندی وابسته ­­به نرخ جریان و نسبت هم­ ارزی است. در شعله­ های مسطح، با افزایش نرخ جریان، به­دلیل افزایش سرعت گازهای داغ سوخته ­شده، فرکانس نوسانات نیز افزایش می­ یابد. در شعله­ه ای سلولی، با افزایش نرخ جریان، فرکانس نوسانات کاهش پیدا می ­کند. در نرخ­ های جریان یکسان، کاهش شدید فرکانس نوسانات نشان­ دهنده ظهور شعله ­های سلولی است. بنابراین، امکان تشخیص گذر شعله از حالت مسطح به سلولی فراهم می­ شود.زمانی­ که در یک نرخ جریان ثابت، با افزایش نسبت هم­ ارزی، شاهد افزایش فرکانس نوسانات نباشیم، انتقال از شعله سلولی به شعله مسطح اتفاق می­ افتد. شروع انتقال از شعله سلولی به شعله مسطح در نرخ­ های جریان 1/1، 1/2، 1/3، 1/4، 1/5 و 1/6 مترمکعب بر ساعت به ­ترتیب در نسبت­ های هم­ ارزی 0/6، 0/62، 0/62، 0/64، 0/66 و 0/67 اتفاق می ­افتد. محل شروع انتقال منطبق بر شروع ناحیه برخاستگی براساس پردازش تصویر است. این پژوهش، دارای جنبه­ های تازه­ای از بررسی پایداری شعله می­ باشد بدون آنکه سبب اختلال در شکل شعله شود و به رژیم شعله آسیب وارد کند.
 

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Diagnostics of flame instability in a premixed surface flame burner using frequency analysis

نویسنده [English]

  • Mohammad Zabetian Targhi 2
2 Department of Mechanical Engineering, Tarbiat Modares University, Tehran, Iran
چکیده [English]

This study investigates the stability of a surface flame burner using a photodiode and data acquisition system. The light intensity fluctuations were measured by the photodiode and, using fast Fourier transform, they were transferred from the temporal to the frequency space. To illustrate the dynamic behavior of premixed flames, flames are divided into two regions of cellular flames and surface flames. This classification is dependent on the flow rate and the equivalence ratio. In surface flames, as the flow rate increases, the oscillation frequency also increases because the hot burned gas velocity increases. In cellular flames, as the flow rate increases, oscillation frequency decreases. At identical flow rates, the sharp decrease in the oscillation frequency indicates the appearance of cellular flames so we can find the transition from the surface flame to the cellular flame. At a constant flow rate, with an increase in the equivalence ratio, there is no increase in the oscillation frequency, the transition from the cellular flame to the surface flame occurs. The initiation of the transition from the cellular flame to the surface flame occurs at flow rates of 1.1, 1.2, 1.3, 1.4, 1.5, 1.6 m3 / h and at equivalence ratios of 0.6 , 0.62, 0.62, 0.64, 0.66, and 0.67, respectively. The location of the transition corresponds to the start of the liftoff zone based on image processing. This research is innovative because it is possible to evaluate flame stability using a non-intrusive method without disturbing the flame shape and damaging the flame regime.

کلیدواژه‌ها [English]

  • Intrinsic Instability
  • Cellular Flame
  • planar Flame
  • Typical-oscillation frequency
  • Frequency analysis
 

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