İçten yanmalı motorlarda honlama açısının güç silindiri tribolojik performansı üzerine etkilerinin incelenmesi
The investigation of effect on engine honing angle on tribological performance at internal combustion engines power cylinder
Yazar: ONUR GEZER
Danışman: DOÇ. DR. ÖZGEN AKALIN
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Makine Mühendisliği Ana Bilim Dalı
Derece: Yüksek Lisans, 2017
Konu: Makine Mühendisliği = Mechanical Engineering
Dizin: Otomotiv = Automotive ; Triboloji = Tribology

Özet:
İçten yanmalı motorlar, 1800'lü yılların ikinci yarısında icatlarından sonra, gelişen
teknik ile beraber taşıt tahrikinde kullanıma geçmiştir. İmalat teknolojisindeki
ilerlemeler ile beraber kara yolu taşıtları orta-alt ekonomik sınıfları da kapsayacak
şekilde kendisine pazar payı edinmiş ve günümüzün en çok kullanılan gereçlerinden
biri haline gelmiştir. Bu durum da artan çevre kirliliği ve petrol rezervlerinin
azalmasıyla sonuçlanmıştır.Artan çevre kirliliği sonucunda belli regülasyonlar
devreye konmuştur. Bu durum ilgili alanda çalışan bilim insanları ve mühendisleri
çeşitli araştırmalar yapmaya itmiş ve çeşitli stratejiler ile yakıt sarfiyatı ve
emisyonlar belli değerlere indirgenmiştir.
Günümüzde daha dar bir banda sıkışan emisyon değerleri ve yakıt tüketim değerleri
sebebiyle yanmaya yapılan müdahalelerin haricinde motor konstrüksiyonu ve yüzey
özelliklerine de müdahale edilmeye başlanmıştır.
Bu çalışma kapsamında silindir yüzey tekstürü üzerinde karakteristik özellik olan ve
tribolojik özellikler üzerinde önemli bir rol oynayan silindir honlama açıları
değiştirilerek, bu durumun silindir yağ film kalınlığı, sürtünme kayıpları ve yağ
sarfiyatı üzerindeki etkileri incelenmiştir.
Çalışma kapsamında Reynolds denklemine, yüzey pürüzlülüklerinin etkisinin
eklenmiş formu olan, Patir ve Cheng tarafından geliştirilen ortalama Reynolds
denkleminden faydalanılmıştır. 15o, 30o, 45o ve 60o silindir honlama açıları için
basınç farkından kaynaklanan akış faktörleri olan ϕx, ϕy değerleri ve pürüzlü yüzeyin
pürüz hacimlerinin ek yağlayıcı taşımasından kaynaklanan, kesme kaynaklı akış
faktörü olan ϕs değerleri elde edilmiştir. Daha sonra bu sonuçlar ''AVL-Excite''
programının ''Piston-Ring'' modülünde; kurulan matematiksel modelden elde edilen
akış faktörleri, temel motor büyüklükleri ve termodinamik dataları gibi karakteristik
çalışma özellikleri girilerek simüle edilmiştir.
Yukarıda bahsedilen sürecin ardından motor simülasyon değerleri incelenmiştir.
İnceleme silindir yağ film kalınlıkları, toplam segman-silindir sürtünme kuvveti,
toplam sürtünme gücü, sürtünme kaynaklı ortalama efektif basınç düşüşü,
mekanizmasına göre yağlayıcı sarfiyatı başlıklarını kapsamaktadır.

Abstract:
Internal combustion engines came into use in vehicle drive through the advanced
techniques following the inventions during the second half of the 1800s. Thanks to
the improvements in the manufacturing technology, road vehicles have gained a
market share including lower-middle economic classes, and have become the most
commonly used instruments in today's world. This fact led to increasing
environmental pollution and decreasing the oil reserves. Certain regulations were put
into practice as a consequence of the increasing pollution. This prompted the
scientists, and engineers working in the related field to do various researches, and
thus fuel consumption and emissions have been reduced to a certain amount by
means of several strategies.
Apart from the interventions to combustion due to the emission values and fuel
consumption currently restrained in a narrower band, there commenced some
interventions to the engine construction, and surface as well.
Within the scope of this study, engine honing cross-hatch angles, which have a
characteristic and vital role on the surface texture of a cylinder, were changed to
observe their impact on lubricant oil film thickness, friction loss, and lube oil
consumption.
Cylinder honing trace and honing angle exist as a natural result of the honing
machining process method. Small volumes which comprise of during honing process
function as a reservoir and transfer line for engine lubricating oil. The tribological
properties of the honed surfaces differ according to the honing angle, peak and
valley roughness values. Honing angle are generally between 40o-60o or 115o-140o
ranges for conventional engines. 40o-60o range use more widely. 115o-140o range is
preferred for helical slide honing. But sometimes we can be seen smaller honing
cross-hatch values at race car engines.
Friction force can be significantly reduced by manipulating with surface textures.
The lowest oil film thickness which provided hydrodynamic lubrication regime,
gives theoretically the lowest friction coefficient. Friction coefficient increases at
higher or lower thickness than this point. Metal to metal contact will occur if oil film
thickness will decrease. So friction coefficient increase and wear mechanisms take
the action of oil film thickness decreasing. Especially concentrated wear at top dead
centre limits the engine life. As a result, lubrication is getting worse and friction
force increase gradually in consequence of increased amount of wear.

The rings have larger wear effect than piston skirt in terms of contact frequency and
contact mechanisms. The boundary lubrication regime at top and bottom dead
centres is largely responsible for wear. On the other side, high combustion chamber
temperatures, low film thickness and high acidic concentration are other wearing
factors. At middle area of piston stroke hydrodynamic lubrication regime obtain, and
wear at there are largely dependent on the presence of abrasive substances which is
incorporated to engine lubrication oil.
Piston-ring-cylinder system has a very important role in engine life and efficiency.
The low cylinder liner roughness values decrease the engine lube oil affectivity. With
getting thin lubricant oil film thickness wear mechanism actuates and friction force
increases, because of metal to metal asperity contact. The higher surface roughness
value improves the lubrication regime but it increases the friction forces. Increasing
the surface roughness excessively cause an increase of friction force, wear and lube
oil consumption. So both the spesific fuel consumption increasing as a result of the
decrease in mechanical efficiency and increasing lube oil consumption and their
emissions such as hydrocarbons, carbonmonoxide, carbondioxide and particulate
matter.
When examinig the tribological performance of the engine cylinder liners with
considering only the surface roughness values can cause misleading results. Because,
while honing the engine cylinder, it is generally necessary to mention three different
processes and during the last process which is known as plateau honing, the valley
roughness value don't change significantly, while peak roughness value show a
considerable decrease. Thus, the risk of asperity contcat risk is reduced, reserve
volumes are created during this moment and these volumes support the performance
of lubricating oil.
Another important parameter for the engine lubrication oil film is load carrying
capacity at cylinder liner lubrication film. Because the load carrying capacity provide
the stability of oil film. The smooth surfaces, that is, the surface which haven't
significant surface roughness, is a too poor in point of load carrying capacity. The
surface texture which is created by honing traces increases the load carrying capacity
depending on the honing characteristic. Plateau honed surfaces have a significant
effect on the load carrying capacity of cylinder lubrication oil film. It is known that
the cylinder honing cross-hatch angle has a direct effect on the capacity, especially
rings and cylinder liner interfeace. Considering that the rings roughness value is so
low, the load carrying capacity is largely related with honing geometry on the
cylinder liners. In this case the load carrying capacity grows as the of valley
roughness depth to honing height ratio increases.
If the honing cross-hatch angle is reduced to smaller value, the average friction
coefficient of the cycle will decreases. On the other hand, engine honing cross-hatch
angle has a direct effect on the oil consumption and the oil consumption decreases
when the honing angle increases. In other words, as the honing angle decreases, the
friction coefficient decreases and oil consumption increases. Because honing marks
have a closer profile to the horizontal axis with decreasing cross-hatch angle and this
situation create more resistance to the fluid flow of lubricatig oil. As a result of the
increased inertia of the lubricating oil in this way, the lubrication oil film tends to
increase film thickness. It is clear from this that changing the cross-hatch angle
improves a feature while the other worsens. Hence, honing cross-hatch angle is stuck

in a definite band, take into account of tribological performance. If we rule out
helical slide honing which has been worked on recently, engine honing cross-hatch
angle of conventional engines is between 45o and 55o.
Textured surfaces are better for mechanical sealing than smooth surfaces. This also
reduces the risk of delaceration of the lubricating oil film. In this way, the risk of
metal to metal contact is reduced and friction force which causing by boundary
lubrication and amount wear decreases. In this situation, gas leakage will be reduced
to lower levels with increased sealing ability. As a result, the compression loseses
will decrease, engine effective power incresae. So spesific fuel consumption and
spesific emission levels decrease.
In internal combustion engines, the oil consumption affect directly exhaust gas
emissions and oil change duration. Therefore, oil consumption should be under
control. Particulate matter emissions are one of the major emissions for conventional
diesel engines and it have to be reduced. Particulate emissions which is produced by
fuel, have been reduced via interfere to injection, combustion and improving
combustion chamber air movements. In this case, the ratio of particulate matter
emissions which is caused by lubricating oil is increase in total engine particulate
emissions.
In internal combustion engines, valves, turbocharging unit, cylinders, piston and
rings are main source of lubricant oil consumption. Among them, piston-ringcylinder
pack is the most important factor in oil consumption
For this study, the Reynolds equation was used, which was developed by Patir and
Cheng as a version including the impact of surface roughness. The shear flow factor
of ϕs which come to mean roughness volume of the rough surface carrying additional
lubricant, the pressure flow factors of ϕx, ϕy were obtained resulting from for the 15o,
30o, 45o, and 60o engine honing cross-hatch angles. Then these results were
simulated by entering the study characteristics such as the flow factors obtained from
the established mathematical model, the main engine sizes, and the thermodynamic
data to the 'Piston-Ring' module of the 'AVL-Excite' program.
The engine simulation values were analysed following the above-mentioned process.
The analysis includes the cylinder lubricant oil film thickness, total segman-cylinder
frictional force, total frictional loss power, frictional mean effective pressure
decrease, and lubricant consumption by mechanism.