The investigation of the impact of oil volume reduction on oil heat up performance and fuel consumption in diesel engine

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.