Tek Silindirli Benzinli Bir Motorda Buji Elektrot Aralığı ile Isı Emisyon Davranışı Arasındaki Korelasyon

Yıl 2025, Cilt: 14 Sayı: 2, 110 - 122, 30.06.2025

Ali Can Yılmaz , Ozlem Erdem

https://doi.org/10.18245/ijaet.1671992

Öz

Bu çalışmada, beş farklı buji toprak elektrodu açıklığının (0.5 mm, 0.75 mm, 1.0 mm, 1.25 mm ve 1.5 mm) tek silindirli bir benzinli motorun performansı ve egzoz emisyonları üzerindeki etkileri deneysel olarak incelenmiştir. Temel performans parametreleri olan fren ortalama efektif basıncı (BMEP), özgül yakıt tüketimi (BSFC) ve egzoz gazı sıcaklığı (EGT) ile birlikte karbon monoksit (CO), yanmamış hidrokarbonlar (HC) ve azot oksitler (NOx) gibi egzoz emisyonları değerlendirilmiştir. Motor, buji açıklığının etkisini izole etmek amacıyla sabit devirde, sabit gaz kelebeği konumunda ve stokiyometrik karışım oranıyla çalıştırılmıştır. Sonuçlar, buji açıklığının yanma kalitesi ve motor çıkış gücü üzerinde önemli bir etkisi olduğunu göstermiştir. Yaklaşık 1.0 mm civarındaki orta büyüklükteki bir açıklık, en yüksek BMEP ve termal verimlilik (en düşük BSFC) değerlerini sağlamış; bu durum daha hızlı yanma ve daha tam yakıt yanması ile ilişkilendirilmiştir. Daha dar veya daha geniş açıklıklar ise performansın bozulmasına neden olmuştur: 0.5 mm’lik dar açıklık, daha zayıf bir kıvılcım oluşturarak daha yavaş yanmaya yol açarken, 1.5 mm gibi çok geniş bir açıklık kısmi ateşleme başarısızlıklarına sebep olmuştur. Bu nedenle, CO ve HC emisyonları U şeklinde bir eğilim göstermiş, yaklaşık 1.0 mm açıklıkta en düşük seviyeye inerken, çok küçük ve çok büyük açıklıklarda tamamlanmamış yanma nedeniyle artış göstermiştir. Buna karşılık, NOx emisyonları en düşük seviyede en küçük ve en büyük açıklıklarda gözlemlenmiş, orta açıklıkta ise yanma verimliliği ve zirve sıcaklık eğilimlerini ters yönde takip ederek en yüksek seviyeye ulaşmıştır. Sonuç olarak, daha büyük bir buji açıklığının başlangıç alev çekirdeğini ve yanma kararlılığını belli bir noktaya kadar iyileştirdiği, ancak bu sınır aşıldığında ateşlemenin düzensiz hale geldiği sonucuna varılmıştır. Yaklaşık 0.9–1.0 mm aralığındaki optimal buji açıklığı, daha eksiksiz bir yanma (düşük CO/HC) ve yüksek termal verimlilik/BMEP arasında en iyi dengeyi sağlamış; ancak daha yüksek yanma sıcaklıkları nedeniyle NOx emisyonlarında artış gözlemlenmiştir.

Anahtar Kelimeler

buji tırnak aralığı , yanma verimi , motor emisyonları , özgül yakıt tüketimi

Correlation between spark plug electrode gap and engine performance-emission characteristics in a single-cylinder petrol engine

Öz

In this study, we conducted an experimental investigation into how five different sparks plug ground electrode gap settings (0.5 mm, 0.75 mm, 1.0 mm, 1.25 mm, and 1.5 mm) affect the performance and exhaust emissions of a single-cylinder petrol engine. The experiments were conducted on a single-cylinder, four-stroke spark-ignition engine operated at constant speed and throttle, with a stoichiometric air–fuel mixture, and instrumented for in-cylinder pressure and full exhaust emission analysis. Key performance metrics including brake mean effective pressure (BMEP), brake specific fuel consumption (BSFC), and exhaust gas temperature (EGT) were assessed, along with exhaust emissions of carbon monoxide (CO), unburned hydrocarbons (HC), and nitrogen oxides (NOx). The engine was operated at a constant speed and throttled with stoichiometric mixture to isolate the influence of spark gap. Among the tested configurations, the 1.0 mm spark gap delivered the best performance, achieving a peak brake mean effective pressure (BMEP) of 7.2 bar and the lowest BSFC of ~300 g/kWh. Emissions of CO and HC followed a U-shaped trend, minimizing at the 1.0 mm gap (CO: 0.48%, HC: 300 ppm), while NOx peaked at this same setting (~2000 ppm) due to elevated flame temperatures. Wider gaps (1.5 mm) induced partial misfires, resulting in increased CO and HC emissions and a 17% drop in BMEP. The results confirm that spark gap size strongly influences combustion quality, and the optimal range of 0.9–1.0 mm offers a practical trade-off between efficiency and emissions. Smaller or larger gaps caused deteriorated performance: a narrow 0.5 mm gap produced weaker ignition leading to slower combustion, while an overly wide 1.5 mm gap caused partial misfires. Consequently, CO and HC emissions followed a U-shaped trend, minimizing at the ~1.0 mm gap and rising at the extreme small and large gaps because of incomplete combustion at those conditions. In contrast, NOx emissions were the lowest at the smallest and largest gaps and peaked at the mid-gap, inversely tracking the combustion efficiency and peak temperature trends. It was concluded that a larger spark gap improves the initial flame kernel and combustion stability up to a point, beyond which ignition becomes erratic. The optimal spark plug gap ~0.9–1.0 mm achieved the best trade-off between complete combustion (low CO/HC) and high thermal efficiency/BMEP, at the cost of increased NOx because of higher combustion temperatures.

Anahtar Kelimeler

Spark plug gap , combustion efficiency , engine emissions , brake specific fuel consumption

Kaynakça

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