مهندسی مکانیک مدرس

مهندسی مکانیک مدرس

بررسی آزمایشگاهی اثر تغییرات طول نازل مشعل بر مشخصه‌های احتراقی شعله پیش‌آمیخته چرخشی

نوع مقاله : پژوهشی اصیل

نویسندگان
گروه مهندسی هوافضا، دانشکده فناوری‌های نوین، دانشگاه شهید بهشتی، تهران، ایران
چکیده
در این مطالعه، تاثیر تغییرات طول نازل مشعل بر مشخصه‌های احتراقی شعله پیش‌آمیخته چرخشی به‌طور تجربی بررسی شده است. از سه نازل متفاوت با طول‌های ۲/۵، ۴/۵ و ۷سانتی‌متر استفاده شد و علاوه‌بر این، هفت چرخاننده با هندسه متفاوت نیز به‌منظور بررسی تاثیر هندسه چرخاننده در همراهی با تغییرات طول نازل مورد بررسی قرار گرفته‌اند. در مطالعه پایداری، مقادیر مشخصی از سرعت توده جریان انتخاب شده و میزان نسبت هم‌ارزی مخلوط سوخت و هوا تغییر داده شد تا حالات نامطلوب شعله نظیر خاموشی و اتصال شعله به نازل تعیین شود. با تعیین این حدود، محدوده پایداری شعله در گستره‌ای از هندسه‌های متفاوت چرخاننده، طول‌های مختلف نازل مشعل و سرعت‌های توده جریان متفاوت حاصل گشت. نتایج به‌دست‌آمده نشان داد که کاهش طول نازل سبب افزایش میزان مقاومت شعله در برابر خاموشی شده و عملکرد شعله را در خاموشی بهبود می‌بخشد. با افزایش نسبت شعاع چرخاننده، حد خاموشی کاهش پیدا می‌کند به‌طوری که با افزایش نسبت شعاع از ۰/۵۷ به ۰/۷۱ میزان حد خاموشی تا حدود ۱۵% کاهش می‌یابد. میزان آلاینده اکسیدهای نیتروژن به‌صورت افزایشی با نسبت هم‌ارزی افزایش پیدا کرده و شیب افزایش آن برای چرخاننده با نسبت شعاع بالاتر، بیشتر است و چرخاننده با نسبت شعاع ۰/۵۷ (کمترین نسبت شعاع میان چرخاننده‌های دیگر)، دارای کمترین میزان آلایندگی در میان سه چرخاننده دیگر است. به‌طوری که در یک نسبت هم‌ارزی مشخص، میزان آلاینده اکسیدهای نیتروژن در این چرخاننده حدود ۳۰% کمتر از سایر چرخاننده‌ها است.
کلیدواژه‌ها

موضوعات


عنوان مقاله English

Experimental Investigation of the Effects of Burner Nozzle Length Changes on Combustion Characteristics of a Swirl Premixed Flame

نویسندگان English

N. Heshmati
S.M. Mirsajedi
Aerospace Engineering Department, New Science & Technologies Faculty, Shahid Beheshti University, Tehran, Iran
چکیده English

In this study, the effects of burner nozzle length changes on combustion characteristics of a swirl premixed flame are investigated. Three nozzles with different lengths (2.5, 4.5, and 7cm) have been used. Also, in order to investigate the effect of swirler geometry on the combustion characteristics of flame along with changes in nozzle length, 7 swirlers with different geometries were examined. In the study of flame stability, certain values of the bulk velocity were selected, which in these values the equivalence ratio of the fuel-air mixture was changed to determine the unfavorable flame condition such as blow-off and flame attachment to the nozzle. By determining these limits, the flame stability map was obtained in a range of different swirlers geometries, different burner nozzle lengths, and different flow mass velocities. The results showed that by increasing the swirlers radius ratio, the blow-off limit of swirlers decreases so that by increasing the radius ratio from 0.57 to 0.71, the blow-off limit decreases about 15%, and the stability of the flame is improved. Reducing the length of the nozzle increases the flame resistance against blow-off. The amount of NOx increased with equivalence ratio and the slope of the increase in NOx increased for the swirler with a higher radius ratio and the in a certain equivalence ratio, the amount of NOx of swirler with a radius ratio of 0.57, which is the lowest radius ratio among other swirlers (about 30%).

کلیدواژه‌ها English

Low-Swirl Combustion
flame stability
Radius Ratio
Nozzle Length
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