Assessment of heat exchanger performance of an EGR cooler and effect to the engine performance

Environmental pollution puts humanity in a risky situation. Especially, humanity is dealing with diseases caused by the air pollutant released by machines using fossil fuels.WHO and other organizations such as EPA are trying to increase the awareness of the situation by publishing the statements about the situation and possible risks of the situation by giving numbers. Moreover, by corporating the government, organizations also put some rules and restrictions to decrease the air pollution in worldwide. As it mentioned the primary pollutant to air is machines that consume fossil fuels such as fossil fuel plants, ships using fossil fuel, trains, airplanes and cars making the making facilities to enhance business and social lives. Today, there is no option to get rid of these machines and industry. Therefore, in worldwide, there are regulations applied all the industries working to decrease the emissions consumed by fuel. In Turkey, as similar as other countries and continents, governments needs to follow the regulations for all industries. Considering the automotive industry, there needs to be applied EU emission standards for all vehicles. EU emission standards restrict releasing the pollutant gasses of an engine under the certain limit. These gasses are, NOx causing the ozone layer in danger by decreasing the thickness, CO2 primary pollutant causing the risk of Global warming and climate change. By helping of increasing technology and other methods applied to other industries that releasing pollutant to regulate the exhaust emission, automotive industry used techniques to minimize emission regulation. One of these methods for decreasing released NOx limit is catalyst technology in order to reduce the emission of CO2, NOx and soot after the combustion process by making the pollutant performed chemical reactions inside of catalysts. Another method is that being used in the automotive industry called as exhaust gas recirculation. Exhaust gas recirculation systems are working by recirculating the exhaust gasses from the exhaust manifold of an engine to air induction system to make the NOx gasses released from vehicle reduced. Exhaust gasses are known as inert gasses to the combustion process occurred. Therefore, recirculating the exhaust gasses to the intake systems makes the fresh air concentration in cylinders lesser in order to decrease the temperature in the combustion chamber. As mentioned in the previous paragraph, considering the decreasing temperature in cylinders, exhaust gasses as a hot gas couldn't play the role very well. In order to achieve the NOx emission produced in combustion chamber, there should be heat exchange process applied to exhaust gasses in order to decrease the temperature. With a view to handle this process, into the exhaust gas recirculation line by locating a heat exchanger to cool down the exhaust gasses heat. In the engine side, applying the EGR methods is changing respect to conditions NOx quantity released. Therefore, recirculating not only recirculating exhaust mass quantity changed but also the amount of heat needed to be exchanged. This complexity puts to exhaust gas recirculation systems needed to assess calibration problem and heat exchanger design problem in order to achieve heat transfer process to be covered in all engine conditions. There should be design process in a view to cover both situations. First of all, the decision about choosing the right EGR cooler for an engine specifically is made by designer engineers and calibration engineer. This process is one of the most sensitive steps has to be performed in the best way. Lack of knowledge about the how heat exchange process conducted in EGR coolers is putting the heat transfer performance of EGR cooler back to packaging and piece cost issues. Afterward, due to the heat transfer performance issues seen in the dynamometer test, EGR cooler designs process starts from beginning in order to satisfy heat transfer performance behavior in the dynamometer. In this study, the heat transfer performance prediction methodology is mentioned by putting EGR cooler design process before the dynamometer testing. The assessment was performed by using a heat exchanger currently using in an engine. As the first step of the study, in order to assess the EGR cooler performance, the mathematical model is generated by applying the all the geometrical information in the gas phase and coolant phase including fins information in order to enhance the heat transfer of the cooler in an accurate approximation. These output data calculated by using the EGR cooler performance model were validated with the data extracted in dynamometer test results. As a second step, to be able to understand the heat transfer behavior effect on the engine side, engine performance model represented to actual engine was generated by using the engine specific information. These informations are turbocharger characteristic curves, combustion process parameters, pipes lengths, and diameters surrounding the engine and calibration information regarding EGR and intake value positions respect to engine operating condition. Engine performance model was validated with the data extracted in same dynamometer test as used as in the EGR cooler performance test. At the final step, by changing the parameters considered for assessing the EGR cooler performance, EGR cooler performance was evaluated with different EGR cooler operating conditions. As referenced data calculated by using EGR cooler performance prediction model, engine performance model was conditions in order to give the same outputs from an engine. As a conclusion of the study, by helping of EGR cooler performance model and engine performance model, not only EGR cooler performance assessment predicted and also by applying changed effects seen in EGR cooler side can be interpreted in the engine performance model.