Investigation of Stroke/Bore Ratio Effects in Spark Ignition Engines via Exergy Analysis

Year 2024, Volume: 65 Issue: 714, 121 - 145, 29.04.2024

İsmet Sezer

https://doi.org/10.46399/muhendismakina.1257235

Abstract

This study investigates theoretically the effects of stroke/bore (s/b) ratio with availability (exergy) analysis in LPG (100% Propane) fuelled spark ignition (SI) engines. For this purpose, a two–zone quasi–dimensional cycle model of SI engines has been used. The combustion process is simulated as turbulent flame entrainment model, the intake and exhaust processes is simulated by using the simple empirical equations in the cycle model. The principles of the second law of thermodynamics were applied to the cycle model in order to perform the exergy analysis. In the exergy analysis, the exergetic terms such as the exergies transferred by heat, work and exhaust, irreversibilities, fuel chemical exergy, thermomechanical exergy and total exergy were calculated for the selected s/b ratios. In addition, the first and second law efficiencies and indicted specific fuel consumption were also calculated. Thus, the effects of s/b ratio on the exergetic terms, the first and second law efficiencies and indicated specific fuel consumption were determined for LPG fuelled SI engines. The results of the study showed that the increase of the s/b ratio reduces the values of the heat losses, irreversibility and indicated specific fuel consumption, increases the cycle work, exergy losses by exhaust gasses with the first and second law efficiencies in SI engines. The increasing of stroke/bore ratio from 0.7 to 1.3 in LPG fuelled SI engines decreases the heat losses by 10.67%, irreversibilities by 1.89% and indicated specific fuel consumption by 3.91%, while it increases exergy transfer with work by 4.12%, exergy losses with exhaust gasses by 2%, the first law efficiency by 4.07% and the second law efficiency by 4.08%, respectively.

Keywords

Spark ignition engine, LPG, stroke/bore ratio, exergy analysis, irreversibilities, efficiency

LPG YAKITLI BUJİ ATEŞLEMELİ MOTORLARDA STROK/ÇAP ORANI ETKİLERİNİN EKSERJİ ANALİZİYLE İNCELENMESİ

Abstract

Sunulan çalışmada LPG (%100 Propan) yakıtlı buji ateşlemeli motorlarda strok/çap (s/ç) oranının etkileri kullanılabilirlik (ekserji) analiziyle teorik olarak incelenmiştir. Bu amaçla iki bölgeli yanma modeline sahip sanki boyutlu bir buji ateşlemeli çevrim modeli kullanılmıştır. Çevrim modelinde yanma işlemi türbülanslı alev yayılması yaklaşımıyla, emme ve egzoz işlemleri ise basit ampirik bağıntılar kullanılarak modellenmiştir. Ekserji analizini gerçekleştirmek için kullanılan çevrim modeline termodinamiğin ikinci kanunuyla ilgili yaklaşımlar uygulanmıştır. Ekserji analizinde ısı, iş ve egzozla transfer edilen ekserjiler, tersinmezlikler, yakıt kimyasal ekserjisi, termomekanik ekserji ve toplam ekserji gibi ekserjitik terimler seçilen strok/çap oranları için hesaplanmıştır. Ayrıca, 1. ve 2. Kanun verimleri ile indike özgül yakıt tüketimi de hesaplanmıştır. Böylece, buji ateşlemeli LPG yakıtlı motorlarda s/ç oranının ekserjitik terimler, 1. ve 2. Kanun verimleri ve indike özgül yakıt tüketimi üzerindeki etkileri belirlenmiştir. Çalışma sonuçları, LPG yakıtlı buji ateşlemeli motorlarda s/ç oranının artırılmasının ısı kayıpları ve tersinmezlik değerlerini ve indike özgül yakıt tüketimini azalttığını, çevrim işi, egzoz gazlarıyla kaybedilen ekserji, 1. Kanun verimini ve 2. Kanun verimini artırdığını göstermiştir. LPG yakıtlı buji ateşlemeli motorlarda strok/çap oranının 0,7 değerinden 1,3 değerine çıkarılması ısı kayıplarını %10,67, tersinmezlikleri %1,89 ve indike özgül yakıt tüketimini %3,91oranlarında azaltırken işle transfer edilen ekserjiyi %4,12, egzozla kaybedilen ekserjiyi %2, 1. Kanun verimini %4,07 ve 2. Kanun verimini %4,08 oranlarında artırmıştır.

Keywords

Buji ateşlemeli motor, LPG yakıtı, strok/çap oranı, ekserji analizi, tersinmezlikler, verim

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