Hava Fazlalık Katsayısı ve Oktan Sayısı Değişiminin HCCI Yanma Karakteristiklerine ve Motor Performansına Etkileri

Homojen dolgulu sıkıştırma ile ateşlemeli (HCCI) motorlar yüksek termik verimleri ve düşük egzoz emisyonları nedeniyle mevcut içten yanmalı motorlara alternatif bir yanma modelidir. Bu çalışmada, port tipi enjeksiyonlu, tek silindirli bir HCCI motorda hava fazlalık katsayısının ve oktan sayısının HCCI yanması üzerine etkileri deneysel olarak incelenmiştir. Deneyler tam yük şartlarında, 60 oC emme havası giriş sıcaklığında ve 800 min-1 motor hızında yapılmıştır. Ayrıca deneyler farklı hava fazlalık katsayılarında yapılmıştır. Oktan sayısının artırılması ile maksimum silindir içi basıncın oluşum noktası daha geç krank açılarında gerçekleşmiştir. Oktan sayısının artırılması yanma süresinin uzamasına neden olmuştur. Hava/ yakıt oranının artması basınç artış oranını azaltmıştır. Hava/yakıt oranının azaltılması silindir içerisine sürülen enerji miktarını artırmıştır. Böylece en yüksek silindir içi basınçlar bu şartlar altında elde edilmiştir. En yüksek indike termik verim RON60 yakıtı kullanımında, hava yakıt oranının 2,14 olduğu şartlarda % 40,6 olarak tespit edilmiştir. Hava yakıt oranının azaltılması yanmanın erken gerçekleşmesini sağlamıştır. Bu nedenle net iş azalmıştır. Böylece indike termik verim de azalmıştır.

Anahtar Kelimeler:

Hava yakıt oranı, HCCI, yanma, RON20, RON60, egzoz emisyonları

The Effects of Air Fuel Ratio and Octane Number on HCCI Combustion and Engine Performance Characteristics

Homogeneous compression ignition (HCCI) engines are an alternative combustion model to existing internal combustion engines due to their high thermal efficiency and low exhaust emissions. In this study, the effects of air fuel ratio and octane number on combustion and engine performance characteristics were investigated with port type injection single cylinder HCCI engine. Experiments were carried out at full load conditions, intake temperature of 60 oC and 800 rpm engine speed. Also, experiments were carried out with different air excess coefficients. The maximum in-cylinder pressure occured at a later crank angle by increasing the number of octane. Increasing the octane number has caused the increase of the combustion duration. The increase of air fuel ratio decreases the pressure rise rate. Decreases of air fuel ratio has increased the amount of injected energy to the cylinder. So that, the highest in-cylinder pressures are obtained under these conditions. The highest indictical thermal efficiency 40.6 %, provided that the air fuel ratio was 2.14 with using RON60 fuel. Decreases of air fuel ratio caused the combustion advance. For this reason net work decreased. Thereby, indicated thermal efficiency decreased.

Keywords:

Air fuel ratio, HCCI, combustion, RON20, RON60, exhaust emissions,

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