SPREY KONİ AÇISININ DİREKT ENJEKSİYONLU MOTORDA KEROSEN İÇİN YANMA VE PERFORMANS KARAKTERİSTİKLERİNE ETKİLERİ

Year 2019, Volume: 39 Issue: 2, 209 - 228, 31.10.2019

Ahmet Yontar

Abstract

Bu çalışma, sprey koni açılarının silindir içi yanma özellikleri üzerindeki etkilerinin kerosen kullanımı için sayısal ve deneysel yöntemlerle belirlenmesi üzerine odaklanmıştır. Bu amaçla, 3-B silindir içi yanma HAD (Hesaplamalı Akışkanlar Dinamiği) analizleri, tam yük konumunda motor karakteristiklerinin belirlenmesinde kullanılmıştır. Ayrıca motor testleri, farklı püskürtme konisi açılarına sahip enjektörler kullanılarak yapıldı. Ölçülen performans parametreleri ve sayısal sonuçlar karşılaştırıldı. Kapalı çevrim HAD analizlerinde sırasıyla; motor hızı 1300 d/dak, hava fazlalık katsayısı 1,7 ve sıkıştırma oranı 17:1 olarak sabit tutuldu. 3-B silindir içi HAD analizleri Star-CD/es-ice yazılımında kerosen kullanımı için gerçekleştirildi. HAD modeli; RNG denklemleri, k-ε türbülans modeli ve ECFM-3Z/Compression yanma modeli kullanılarak oluşturulmuştur. Kapalı çevrim çözüm aralığı; üst ölü nokta sıfır kabul edilecek şekilde, üst ölü noktadan 40 KMA önce ile üst ölü noktadan 80 KMA sonra aralığında tanımlandı. Sprey koni açıları (SKA) 5º-25º aralığında değiştirildi ve 5º’lik adımlarla bu aralıkta analizler gerçekleştirildi. Sonuçlar 20º SKA’da 5º SKA’ya göre silindir içi basıncın %15,8 yüksek olduğunu göstermektedir. İndike ortalama efektif basıncın 20º SKA’da; sırasıyla 5º SKA’ya ve 25º SKA’ya göre %4,06 ve %3,41 yüksek olduğu gözlendi. Sprey koni açısı 5º’den 20º’ya artarken silindir içi sıcaklık 1620 K’den 1720 K’e yükseldi. İndike güç 20º SKA’da; 5º SKA’ya ve 25º SKA’ya göre sırasıyla, %7,98 ve %6,72 yüksek olduğu tespit edildi. Testlerde özgül yakıt sarfiyatı 20º SKA’da 5º SKA’ya ve 25º SKA’ya göre %8,51 ve %7,33 daha düşüktür. Genel olarak 20º SKA'daki CO2 oluşumu, 5º SKA'dan %24,3 daha yüksektir. 25º SKA için NOx oluşumu 5º SKA'dan %51,2 ve 25º SKA'dan %19,2 daha düşüktür. 20º SKA'da kurum oluşumu genel olarak 5º SKA'dan %24,8 daha düşüktür. Çalışmanın sonucunda kerosen kullanımında belirtilen çalışma koşulları için optimum püskürtme konisi açısı 20º SKA olarak belirlenmiştir.

Keywords

Sprey koni açısı, kerosen, damlacık hızı, direkt enjeksiyonlu motor, is.

EFFECTS OF SPRAY CONE ANGLE ON COMBUSTION AND PERFORMANCE CHARACTERISTICS OF DIRECT INJECTION ENGINE FOR KEROSENE

Abstract

This study focuses on the determination of the effects of spray cone angles on in-cylinder combustion characteristics for kerosene via numerical and experimental methods. For this aim, the 3-D in-cylinder combustion CFD (Computational Fluid Dynamics) analyses were employed in the determination of engine characteristics at full load position. Also, the engine tests were performed using injectors with different spray cone angles. Measured performance parameters and numerical results were compared. The closed cycle CFD analyses; the engine speed, excess air coefficient and compression ratio were kept constant at 1300 rpm, 1.7 and 17:1, respectively. The 3-D in-cylinder CFD analyses were performed in Star-CD/es-ice software for kerosene. The CFD model was built by using RNG equations, k-ε turbulence model, and ECFM-3Z/Compression combustion model. The closed cycle was defined in the range of 40 CAD before top dead center to 80 CAD after top dead center. Spray cone angle (SCA) was changed in the range of 5º-25º and analyzed in 5º steps at the intervals. The results show that the in-cylinder pressure at 20º SCA is 15.8% higher than 5º SCA. The indicated mean effective pressure at 20º SCA was observed as 4.06% and 3.41% higher than 5º SCA and 25º SCA, respectively. The temperature in-cylinder increased to 5º-20º SCA while the highest temperature rises from 1620 to 1720 K in-cylinder. The indicated power at 20º SCA was detected as 7.98% and 6.72% higher than 5º SCA and 25º SCA, respectively. The brake specific fuel consumption at tests for 20º SCA is 8.51% and 7.23% lower than 5º SCA and 25º SCA. The CO2 formation at 20º SCA is overall 24.3% higher than 5º SCA. The NOx formation for 25º SCA is higher 51.2% than 5º SCA and 19.2% lower than 25º SCA. The soot formation at 20º SCA is overall 24.8% lower than 5º SCA. As a result of the study, the optimum spray cone angle for the operating conditions specified in the kerosene usage was determined to be 20º SCA.

Keywords

Spray cone angle, kerosene, droplet velocity, direct injection engine, soot

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