Effects of varying the compression ratio on the performance of a biodiesel fuelled diesel engine

Abstract

Improved thermal efficiency, reductions in fuel consumption and pollutant emissions from biodiesel fuelled diesel engines are important issues in engine research. To achieve these, rapid and better air-fuel mixing is the most important requirement. The mixing quality of biodiesel with air can be generally improved by selecting the best engine design parameters. Experiments were performed using a single cylinder Direct Injection (DI) diesel engine at different compression ratios. The effects of varying the compression ratio on the combustion, performance and exhaust emissions using a blend of 20% Pongamia Oil Methyl Ester (POME20) by volume in diesel were evaluated. The test results showed that improvement in terms of brake thermal efficiency and specific fuel consumption for engine having higher compression ratio, particularly with compression ratio of 18.5. Substantial improvements in reduction of emission levels were observed for higher compression ratio in terms of carbon monoxide, hydrocarbon and smoke. However improved air motion inside the cylinder and high pressure injection increases the oxides of nitrogen (NOx). The change of compression ratio from 17.5 to 18.5 resulted in reduction in delay period and improvement in heat release rate.

Keywords

• Biodiesel
• diesel engine
• compression ratio
• combustion
• performance

Biyodizel Yakıtlı Bir Dizel Motorda Değişen Sıkıştırma Oranlarının Performansa Etkisi

Abstract

Biyodizel yakıtlı dizel motorlarda termal verimin arttırılması, yakıt tüketimi ve kirletici emisyonların azaltılması önemli motor araştırma konularındandır. Bunu gerçekleştirmek için hızlı ve daha iyi bir hava-yakıt karışımı en önemli gerekliliktir. Hava biyodizel karışım kalitesi genellikle en iyi motor tasarım parametreleri seçilerek geliştirilebilir. Deneyler, farklı sıkıştırma oranlarında tek silindirli direkt enjeksiyonlu (DE) bir dizel motorda gerçekleştirilmiştir. Hacimce %20 pongamia yağı metil esteri (POME20) dizel yakıtı ile değişen sıkıştırma oranlarının yanma, performans ve eksoz emisyonlarına olan etkisi incelenmiştir. Deney sonuçları özellikle 18.5 sıkıştırma oranı gibi yüksek sıkıştırma oranlarında motor frenleme termal verimi ve özgül yakıt tüketiminde iyileşme gösterdi. Yüksek sıkıştırma oranlarında karbon monoksit, hidrokarbon ve is emisyon seviyelerinin azaltılması bakımından önemli bir gelişme gözlemlendi. Ancak silindir içerisindeki iyileştirilmiş hava hareketi ve yüksek enjeksiyon basıncı azot oksitleri arttırmıştır. Sıkıştırma oranının 17.5 ten 18.5 değiştirilmesi yanmadaki gecikme periyodunun azalmasına ve iyileşmesine neden olmuştur.

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