Ortak hatlı bir dizel motorda farklı devirlerde çevrimden çevrime yanma değişimleri üzerine deneysel bir çalışma

Öz

Bu çalışmanın amacı, dört silindirli ortak hatlı bir otomotiv dizel motorunda 1600, 1800, 2000 d/dk ’lık devirlerde çevrimsel yanma değişimlerini deneysel olarak incelemektedir. Çalışma, bir modern dizel motorda devir sayısının çevrimsel farklılıklara bağlı etkisini ele almaktadır. Maksimum yanma basıncı (SBmaks), maksimum basınç artış oranı (BAOmaks), ve ortalama indike basınç (OİB) parametrelerini kapsayan 1000 çevrimsel yanma verisi deneysel çalışmada analiz edilmiştir. Her bir motor hızında, silindir basıncındaki çevrimsel değişimlerin minimum olduğu, ancak SBmaks, BAOmaks ve OİB detaylı olarak karşılaştırıldıklarında incelenen çevrimlerde önemli farklılıklar ortaya çıkmıştır. Daha yüksek silindir sıcaklıkları ve hava hareketleri yanmayı iyileştirmiştir. Böylece, artan motor devriyle birlikte sadece OİB ve SBmaks’ın çevrimsel değişim katsayıları (ÇDK) azalırken, aynı zamanda ortalama SBmaks ve BAOmaks artmıştır. Diğer taraftan, artan devirle birlikte emme havasının sürtünme etkisi, iyileşen yanmanın pozitif etkilerini azaltmış ve sonuç olarak ortalama OİB azalmıştır. SBmaks ve OİB’nin ÇDK’ları tüm devirlerde %1’in altında kalmıştır, böylece oldukça geniş çevrim sayılarında bile stabil ve düzenli yanma sürdürülmüştür. Her bir çevrimde, yakıt sistemi ön enjeksiyon fazının, ilk yanma basınç pikinin oluşumunda etkili olduğu gözlenmiştir. Bu çalışmadan, ortak hatlı dizel motorun farklı devirlerde küçük çevrimsel farklılıklar meydana getirdiği sonucuna varılmıştır.

Anahtar Kelimeler

• Çevrimsel değişimler
• Yanma parametreleri
• Ortak hatlı dizel motor

An experimental study on cycle-to-cycle combustion variations at different speeds in a common-rail diesel engine

Abstract

The objective of this study is to experimentally investigate cyclic combustion variabilities in a four-cylinder automotive common-rail diesel engine at different engine speeds, including 1600, 1800, and 2000 rpm. The investigation evaluates the relative effects of speeds on the cyclic discrepancies in a modern diesel engine. 1000 cyclic combustion data including peak combustion pressure (Pmax), peak pressure rise rate (PRRmax) and indicated mean effective pressure (IMEP) were analyzed in the experimental study. It was found that the cyclic fluctuations in combustion pressure in each engine speed were minor, but detailed comparison of Pmax, PRRmax, and IMEP revealed noteworthy differences in the studied cycles. Higher cylinder temperatures and air movement improved combustion. Therefore, not only coefficient of variations COVs of IMEP and Pmax decreased, but also mean Pmax and PRRmax increased with increasing engine speed. On the other hand, the friction effect of the intake air reduced the positive effects of improved combustion with increasing engine speed and as a result mean IMEP decreased. COVs of IMEP and Pmax remained below 1% at all speeds, thus stable and regular combustion was maintained even in a numerous range of the cycle numbers. Pre-injection phase of fuel injection system was recognized to be effective in formation of the first peak of the combustion pressure in individual cycles. It was concluded from this study that the common-rail diesel engine generated minor cyclic discrepancies under different engine speeds.

Keywords

• Cyclic variations
• Combustion parameters
• Common-Rail diesel engine

Kaynakça

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