Hekzan ve N-Heptan Yakıt Karışımları ile Çalışan Homojen Dolgulu Sıkıştırma İle Ateşlemeli (HCCI) Bir Motorda Hava Fazlalık Katsayısının Yanma ve Motor Performansı Üzerindeki Etkileri

Öz

Homojen dolgulu sıkıştırma ile ateşlemeli motorlar düşük sıcaklık yanma eğilimine ve yüksek termik verime sahip motorlardır. Yanma üzerinde doğrudan kontrolün olmadığı bu motorların çalışma aralığı vuruntu ve tutuşamama problemleri nedeniyle sınırlandırılmaktadır. Bu noktada silindire alınan karışım kompozisyonu ve farklı çalışma parametreleri ile özellikle yüksek yüklerde vuruntu probleminin ortadan kaldırılması amaçlanmaktadır.

 

HCCI yanması motor çalışma parametrelerinden oldukça etkilenmektedir. Bu çalışmada tek silindirli dört zamanlı, buji ile ateşlemeli bir motor homojen dolgulu sıkıştırma ile ateşlemeli motora dönüştürülmüştür. Deney motoru hekzan ve n-heptan yakıt karışımları ile 1400 d/d’da, 1.9 ile 2.74 hava fazlalık katsayısı (HFK) değerleri arasında, tam yükte HCCI yanma modunda çalıştırılmıştır. Hekzan yakıtının silindir basıncı, ısı dağılımı, silindir içi sıcaklık, yanma süresi, yanma başlangıcı, çevrimsel farklılıklar, vuruntu yoğunluğu, indike ortalama efektif basınç (imep), termik verim ve emisyonlar (HC ve CO) üzerindeki etkileri deneysel olarak incelenmiştir. Sabit emme havası giriş sıcaklığında yapılan deneylerde hava fazlalığı arttıkça silindir basıncının

genişletilebileceği görülmüştür.

Anahtar Kelimeler

• Hava Fazlalık Katsayısı; Hekzan; Homojen Dolgulu Sıkıştırma İle Ateşlemeli Yanma; Motor Performansı

Effects of Air Excess Ratio on Combustion and Engine Performance in a Homogeneous Charge Compression Ignition Engine fuelled with Hexane and N-Heptane Fuel Mixtures

Abstract

Homogeneous charge compression ignition engines are engines with low temperature combustion tendency and high thermal efficiency. The operating range of these engines, where there is no direct control over combustion, is limited because of knock and misfire problems. At this point, it is aimed to eliminate the knocking problem especially at high loads with the mixture composition taken into the cylinder and different operating parameters.

 

HCCI combustion is highly affected by engine operating parameters. In this study, a single-cylinder four-stroke spark-ignition engine was converted to a homogeneous charge compression ignition engine. The test engine was operated with hexane and n-heptane fuel mixtures at 1400 rpm and between 1.9 and 2.74 air excess ratio in full load HCCI combustion mode. The effects of hexane fuel on cylinder pressure, heat release rate, in-cylinder temperature, combustion duration, start of combustion, cyclic variations, knock density, indicated mean effective pressure (imep), thermal efficiency and emissions (HC and CO) were investigated experimentally. In the experiments carried out at constant intake air inlet temperature, it was observed that the cylinder pressure and heat release rate decreased with increasing air excess ratio. As a result, HCCI combustion was found to be highly affected by air excess ratio and fuel composition. It has also been found that the range of operation can be extended in the knock boundary zone in HCCI combustion.

Keywords

• Air Fuel Ratio; Hexane; Homogeneous Charge Compression Ignition; Engine Performance

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