Dizel motorun soğuk ilk çalışma durumunda motor yağ miktarının, yağ ısınma performansına ve yakıt tüketimi üzerine olan etkisinin incelenmesi
The investigation of the impact of oil volume reduction on oil heat up performance and fuel consumption in diesel engine
Yazar: ŞÜKRÜ CAN ÇERKEZOĞLU
Danışman: YRD. DOÇ. DR. OSMAN AKIN KUTLAR
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Makine Mühendisliği Ana Bilim Dalı / Otomotiv Bilim Dalı
Derece: Yüksek Lisans, 2015
Konu: Makine Mühendisliği = Mechanical Engineering
Dizin: Dizel motorlar = Diesel engines ; Egzoz emisyonları = Exhaust emissions ; Elastohidrodinamik yağlama = Elastohydrodynamic lubrication ; Hidrodinamik yağlama = Hydrodynamic lubrication ; Motor yağları = Engine oils ; Otto motorlar = Otto motors ; Taşıt motorları = Vehicle engines ; İçten yanmalı motorlar = Internal combustion engines

Özet:
Günümüz dünyasında 2000'li yıllarla daha ciddileşen küresel ısınmanın etkileri ve karbon salınımı azaltmak için alından regülasyonlar otomotiv dünyasında yakıt tüketimi ve emisyonlar üzerine daha fazla Ar-Ge yatırımları yapılmasına sebebiyet vermiştir. 2017 yılı ve 2020 yıllarıyla beraber geçilecek Euro 6 emisyon regülasyonu ile CO2 salınım miktarı binek taşıtlar için %27, hafif ticari taşıtlar için %18 azaltılmaktadır. Şu anda bir çok otomotiv firması Euro 6 CO2 hedeflerini sağlayamaktadırlar ve yeni Ar-Ge çalışmalarına günümüz itibari ile başlamışlardır.
Yakıt ekonomisini iyileştirme çalışmaları motor verimini artırmaya yönelik çalışmalardır, 2000'li yıllarla birlikte dizel ve benzinli motorlarda kullanılmaya başlanan turboşarj ve direk injeksiyon yöntemleri yakıt yanmasını iyileştirerek motor verimin artıran çalışmalara bir örnek verilebilinir. Bu örnek dışında, motor pompala kayıplarının azaltılması, pistonlarda ve silindir gömleklerinde kullanılan özel kaplamalar ile motordaki sürtünmelerin azaltılması diğer örnekler olabilir. Diğer bir örnek ise, soğuk ilk çalışma durumundaki motorun ısınma performansının iyileştiren motor soğutma sistemi stratejileri yakıt tüketimini iyileştirilmesi için yapılan diğer yöntemlerdir. 
Bu tezin odak noktası, motorun soğuk ilk çalışma durumunda motor yağının ısınma performansının iyileştirilerek, yağın motor için ideal olan 90-95°C civarına en hızlı şekilde ulaştırılması olmuştur. Motorun belirli bir çalışma ve belirli sınır koşullarında (hava sıcaklığı, motor sıcaklığı, kullanım çevrimi vs.) üretilen ısı sabit olduğu kabul edilebilinir ve yakıtın yanması ile ortaya çıkan enerjinin bir kısmı motorda hareket enerjisine çevrilirken, diğer büyük bir kısmı motor parçalarının, motor soğutma suyunun ve motor yağının ısınmasına, kalan kısmı da kayıp ısı olarak çevreye verilir. 
Motor yağının ısıl kütlesi yüksek olduğundan dolayı motor yağı zor ısınır ve soğur, motor yağının ısıl kütlesini azaltmanın yolu yağ kütlesini azaltmaktır.  Motor yağının kütlesi azaltılırsa motor yağı daha hızlı ısınır. Motor yağının hızlı ısınması motordan ilk çalışma durumda ne sağlayacaktır? Bu soruya şu şekilde cevap verebiliriz; motor yağının viskozitesi sıcaklık ile ters orantılıdır, motor daha düşük viskotile yağ ile çalışırsa motordaki sürtünmeler azalacağı için motor verimi artar ve daha az yakıt ile aynı motor gücüne ulaşılır. Sonuç olarak, motor yağının soğuk ilk çalışma durumda hızlı bir şekilde ısınması yakıt ekonomisinde iyileştirme getirecektir. 
Bu tezde, motor yağı kütlesini (hacminin) azaltılmasının motorun soğuk ilk çalışma durumunda yağ ısınma performansına, motordaki sürtünme kayıplarına ve yakıt tüketimine olan etkisi incelenmiştir. İnceleme yapılırlen literatürde bulunan kaynaklardan yararlanılmıştır. İlk olarak 1D Flowmaster analizi yardımıyla dizel bir motorda olana etkisi hesaplanmıştır. Daha sonra araç emisyon dynosunda yağ hacmi kademeli olarak azaltılarak tüketilen yakıt miktarı hesaplanmıştır, en son olarak motor dynosunda yine bir dizel motorda yağ hacminin minimum ve maksimum olduğu durumlarda motor yağının ısınma performansına, FMEP ve yakıt tüketimine etkisinin ne derece olduğu test edilmiştir. 
Sonuç olarak bakıldığından, yağ hacminin azaltılması ile motordaki yakıt tüketiminin NEDC boyunca %0.75, sabit 2000 motor devri ve %33 motor yükü durumunda ise %0.51 iyileştirilmesinin mümkün olduğu sonucuna ulaşılmıştır. Ayrıca test sonunda, motor yağının yakıt tüketime etkisi için 1D CFD analizi , motor ve araç dyno testlerinden oluşan bir methodda oluşturulmuştur

Abstract:
Starting from the beginning of 2000's, the effects of Global Warming  and updated CO2 emission regulations forces the car manufacturer to invest much more money on R&D for the fuel economy.Euro 6 CO2 emission target is reduced by 27% for the passenger cars and 28% for the commercial vehicles in 2017 and 2020 step by step. In the current situation, the most of the car manufacturers cannot meet new CO2 targets and they have already kicked off the studies on improving the fuel economy.
In last 15 to 20 years, many developments are already accomplished to improve the engine efficieny, then reducing the fuel consumption. One of the technolody developments for that, widely usage of turbocharger in both gasoline and diesel engines, direct injection instead of port fuel injection in gasoline engines and direct injection in diesel engines can be given as an example for the most known technologies on top of improving the engine efficiency by enchanced the combustion efficiency. As an other examples, the special coating techonolgy on the pistons and cylinder liners can be given for improving the engine efficiency and fuel economy by reducing the overal engine friction. The last example would be that the improving the engine cold start-up performace by engine cooling system strategies, which leads to reduce engine heat-up time to reach engine optimum working temperature.
The focus of this thesis is to improve the engine oil heat up performance at the engine cold start up condition, then to accomplish to make the engine oil reach 90-95°C, that is the optiumum working temperature of the oil and the engine, as soon as possible. The main reason to focus on the cold start up condition is the oil viscosity change on the lower temperature from 0°C to 50°C is significant and % change is higher than the viscosity change at the higher oil temperatures. That means any oil heat up improvement at the engine cold start, the viscosity reduction is higher which allows to reduced the friction, then to reduce the fuel consumption at the engine warm up period. 
At the same working set point and the boundary condition of the engine(ambient temperature, air temperature, the driving cycle etc.), the energy generated by the fuel combusiton is constant. The some ratio of the energy released after the combustion is used for the motion energy in the engine, some of that is used to heat up the engine components, engine oil and coolant, and the less of them is rejected to the ambient as loss energy. 
The thermal capacity of the engine is higher then the water and to heat up and cool the oil is difficult than doing the same for the water. If the oil mass is reduced, the thermal capacity of the oil is also reduced, then the oil can reach up to 90-95 °C much faster. The real benefit of the faster oil warm up is to reduce oil viscosity at the cold start up transition period, which leads to reduce the friction and reduce the fuel consumption. 
In this thesis, the impact of the reducing the oil volume in the engine on the oil heat up time, overal friction losses in the engine and the fuel consumpiton are investigated. Many technical papers are written on the topic of improving the engine cold start up performance and some of them mention about reducing the oil volume to reduce oil heat up time. While developing the investigation work flow, the experiences in the literature are also referenced. Initially, the oil heat up performance are calculated in 1D flowmaster analysis with the different level of oil volumes in order to have the initial targets for the oil volume reduction. In 1D flowmaster modal, the oil volume for 1.5L 100 PS diesel engine are reduced from 6.95L by 0.5L steps down to 3.95L then the oil temperature increase on the different oil volumes at NEDC are calculated. With the specific oil temperature heat up rate, we can calculate the viscosity change by Vogel equation, which allows to calculate the friction reduction and impact on the fuel consumption. At the end, it is found that the fuel consumption reduction is higher by 1.0% at the second urban city cycle of NEDC and 0.50% fuel economy can be achieved at overal NEDC by reducing oil volume as 3.0L. 
Then, the vehicle dyno emission test are conducted to observe the fuel consumption with the different level of oil volume in the engine. In vehicle emission dyno test, Ford Cmax vehicle with 1.5L 100PS  diesel engine is used. 3.8L oil as max, 2.8L oil as mid and 1.8L oil as min are investigated. The oil temperature in the oil sump, in the main oil gallery are measured and the heat up difference are observed. At the end, the oil temperature at min oil volume is 4°C to 5°C higher than the max oil volume test run. The impact of that much hotter oil used at the engine cold start up on the fuel consumption is measured by 1.6%.
In order to understand the oil volume reduction impact on oil heat up performance, FMEP and the fuel consumption, the engine dyno test is done with the different level of oil volume at two different cycles; first is 2000 rpm engine speed and %33 engine load, the second one is NEDC converted to engine dyno by collecting data from the vehicle over NEDC test. In dyno testing, 2.2L 120PS diesel engine is investigated at two different oil volume; 6.7L oil as max oil volume and 4.2L oil as min oil volume. In order to investigate FMEP change on the constant engine rpm and the load, the engine is run at 2000 rpm and %33 load. As a result, c.a 10% FMEP reduction is observed at the min oil volume condition in compare to max oil volume. When looking to the oil heat up rate, the oil at min oil volume is 2°C to 3°C higher than the oil at the max oil volume. The impact on the fuel consumption is around 0.50% at 2000 rpm and %33 load test condition. 
At the second phase of engine dyno testing, NEDC test is run at the max and min oil volume condition. As same as flowmaster analysis, engine speed and load data is collected from the vehicle and used in the dyno test. Different from constant engine speed and load test, the oil temperature difference increases during the acceleration period and reduced on the decelaration period and the oil temperature difference is around 0.8°C to 1.5 °C. On the overal NEDC test, 0.75% fuel economy is reached at the end of the test however the main reduction on the fuel economy is observed at the high way period, which is different from what observed in constant engine speed and load test. 
At the end of all studies, it is found that %1.6 fuel economny is possible in the diesel engine tested in vehicle emission dyno test. In the engine dyno testing, 075% fuel economy is reached at the minimum oil level at NEDC run and 0.50% fuel economy is reached at 2000 rpm and %33 engine load test run. These results supports that the oil volume in the engine is critical for the fuel consumption at the engine cold start up period and the main reason is the oil heat up rate is higher at the lower oil volumes, which yields the engine to be run with the lower viscosity of oil, to reduce the friction at the warm up period and require less fuel to run the vehicle. Regarding the test methodology, constant engine speed and load test is appropriate to observe FMEP change and potential reduction on the fuel consumption however running NEDC on the dyno cell is not the best for observing fuel economy benefits.