A simple approach for comparing performance of gasoline general-purpose engines at maximum power

Yıl 2019, Sayı: 15, 269 - 279, 31.03.2019

Emre Arabacı

https://doi.org/10.31590/ejosat.513253

Cited By: 1

Öz

The single or double cylinder, low power output engines used in machines
such as garden hoe machines, chainsaws, generators, lawnmowers, mini tractors
are called general-purpose engines. Each engine manufacturer has engines with
its own unique structural designs. The power of these engines generally varies
depending on the swept volume. However, when the engine catalogs are examined,
the characteristics such as stroke ratio, maximum power speed, and compression
ratio are different. In this study, we present a simple thermodynamic model in
which the gasoline general-purpose engines, whose swept volume, compression
ratio and stroke ratio are different, can be compared by taking into account
their performance at maximum power, friction, irreversibility, exhaust and heat
losses. For the numerical study, by comparing the physical properties of 10
general purpose engines of 5 different manufacturers, their performance was
compared by performing thermodynamic modeling in the conditions where they
produced maximum power. The power values in the catalogs of the engines and the
power values calculated according to the thermodynamic model were very close to
each other and this thermodynamic model was used. According to the
thermodynamic model, maximum cycle temperatures, specific fuel consumption and
power density of the motors were compared. In addition, the heat balance of
each engines is created. Regardless of the brand, model and stroke volume and
effective power, engine parameters are examined according to stroke ratio and
specific fuel consumption. As a result of the study, the maximum cycle
temperature, power density and mechanical efficiency decrease with the increase
in the specific fuel consumption and the stroke ratio. However, the increase in
the stroke ratio increases the specific fuel consumption. According to the
obtained results, it is seen that the characteristics such as course rate and
compression ratio as well as simple properties such as stroke volume and engine
power are important and effective parameters for comparison. As a result of
this study, it can be seen that the thermodynamic model presented can be used
to compare gasoline general purpose engines with different physical properties.

Anahtar Kelimeler

General purpose engine, engine performance, Otto cycle, gasoline engines

Benzinli genel amaçlı motorların maksimum güçteki performanslarının karşılaştırılması için basit bir yaklaşım

Öz

Bahçe çapa makineleri, zincirli testereleri, jeneratörler, çim biçme
makineleri, mini traktörler gibi makinelerde kullanılan tek veya çift
silindirli, düşük güç çıkışlı motorlar genel amaçlı motorlar olarak
adlandırılmaktadır. Her motor üreticisinin kendine özgü yapısal tasarımlara
sahip motorları bulunmaktadır. Bu motorların güçleri genel olarak kurs hacmine
bağlı olarak değişmektedir. Ancak motor katalogları incelendiğinde kurs oranı,
maksimum güçteki hızı ve sıkıştırma oranı gibi karakteristik özellikleri
birbirinden farklıdır. Bu çalışmada kurs hacmi, sıkıştırma oranı ve kurs oranı
birbirinden farklı olan benzinli genel amaçlı motorların maksimum güçteki
performansları, sürtünme, tersinmezlik, egzoz ve ısı kayıpları da dikkate
alınarak karşılaştırılabildiği basit bir termodinamik model sunulmuştur. Sayısal
çalışma için 5 farklı üreticiye ait 10
adet genel amaçlı motorun fiziksel özellikleri referans alınarak maksimum güç
ürettikleri şartlarda termodinamik modellemeleri yapılarak performansları
karşılaştırılmıştır. Motorlara ait kataloglardaki güç değerleri ile
termodinamik modele göre hesaplanan güç değerleri birbirine oldukça yakın
çıkmıştır ve bu termodinamik modelin kullanılabilir olduğunu göstermektedir.
Oluşturulan termodinamik modele göre motorların maksimum çevrim sıcaklıkları,
özgül yakıt tüketimleri ve güç yoğulukları karşılaştırılmıştır. Ayrıca her
motora ait ısı balansı oluşturulmuştur. Marka, model ve kurs hacmi ve efektif
gücünden bağımsız olarak motor parametreleri kurs oranı ve özgül yakıt
tüketimine bağlı olarak
incelenmiştir. Yapılan inceleme neticesinde özgül yakıt tüketimi ve kurs
oranının artmasıyla birlikte maksimum çevrim sıcaklığı, güç yoğunluğu ve
mekanik verimde azalma meydana gelmektedir. Bununla birlikte kurs oranının
artması özgül yakıt tüketimini de artırmaktadır. Elde edilen sonuçlara göre
motorların karşılaştırılması için yalnızca kurs hacmi ve motor gücü gibi basit
özelliklerin yanında kurs oranı, sıkıştırma oranı gibi özelliklerin de
karşılaştırma için önemli ve etkili parametreler olduğu görülmüştür. Bu çalışma
neticesinde, sunulan termodinamik modelin farklı fiziksel özelliklere sahip
benzinli genel amaçlı motorların karşılaştırılabilmesi için kullanılabileceği
görülmüştür. 

Anahtar Kelimeler

Genel amaçlı motor, motor performansı, Otto çevrimi

Kaynakça

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