HOMOJEN DOLGULU SIKIŞTIRMA İLE ATEŞLEMELİ BİR BENZİN MOTORU İÇİN KAM TASARIMI VE İMALATI

Bu çalışmada, homojen dolgulu sıkıştırma ile ateşlemeli (HCCI) bir benzin motoru için kam tasarımı ve imalatı yapılmıştır. 38 mm temel daire çapı ve 124° supap açık kalma süresi için, HCCI yanma karakteristiğine uygun 3,5, 5,5 ve 7,5 mm düşük supap kalkma miktarına sahip kamlar tasarlanmıştır. Dairesel yay eğrisi kullanılarak kam profillerinin genel geometrik modelleri elde edilmiş ve elde edilen kam profili modelleri fourier serisi ile ekstrapole edilerek daire yay eğrisine karşılık gelen eşitlikler türetilmiştir. Tasarlanan kam profilleri için iticinin hız, ivme ve sıçrama etkileri araştırılmıştır. Elde edilen sonuçlar 5. dereceden klasik spline yöntemi ile elde edilen kamlar ile mukayese edilmiştir. Klasik spline fonksiyonları ile elde edilen kam profillerinde supap kalkma miktarı arttıkça kamın iticiye tek noktadan temas özelliğinin kaybolduğu, iticilerin ivme ve sıçrama değerlerinin çok fazla arttığı görülmüştür. Geometrik modeli elde edilen kam profillerinin fourier serileri ile ekstrapole edilmesiyle, yüksek supap kalkma miktarlarında bile kamın iticiye tek noktadan temas etme özelliğinin kaybolmadığı, düşük hız ve ivme ile çalışması sonucu sürtünme ve atalet kuvvetlerinin azaldığı görülmüştür.

CAM DESIGN AND MANUFACTURING FOR A HOMOGENEOUS CHARGE COMPRESSION IGNITION GASOLINE ENGINE

In this study, cams were designed and manufactured for a homogenous charge compression ignition (HCCI) gasoline engine. Low lift cams were designed accordance with HCCI combustion characteristics for 38 mm base circular diameter, 124° dwell angle, 3.5, 5.5 and 7.5 mm valve lifts. Generic geometric models of cam profiles were obtained using circular arc curves. Obtained models were fitted with fourier series and circular arc curve was derived from the corresponding equations. Speed, acceleration and jerk effects of the follower were investigated for designed cam profiles. Obtained results were compared with cams obtained by 5th degree classical spline method. It has been shown that feature a single point of contact of cam into the follower has been lost and acceleration and jerk values of the follower increased so much as long as valve lift increase in the cam profiles obtained by classical spline functions. It has been shown that feature a single point of contact of cam into the follower has not been lost by fitting fourier series of obtained geometric model of cam profile even high valve lifts. Friction and inertia forces decreased due to the low speed and acceleration operation.

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