Essay Example on Thermal management on the internal combustion Engine








Thermal management on the internal combustion engine ICE is a major focus in conventional and hybrid vehicles For proper operation of the ICEs it is crucial to have effective cooling systems and lubrication oil Typically the heat dissipation capacity of the cooling system is dimensioned for the maximum power operating conditions 24 Because engines operate most of the time under partial load conditions the cooling system is oversized and not optimally designed In partial load conditions and with a conventional cooling system the average engine temperature is well under the fully warmed up values while the oil temperature is excessively low 25 This traditionally over design approach also yields the fact that engine thermal management systems do not have major changes over the past years

Only until recently the motivation and regulation towards increased fuel economy and reduced emissions have re ignited the interests towards better thermal management For instance smaller engines with turbo or superchargers require more efficient cooling systems as the engine blocks are more powerful but more compact 5 In this regard different types of innovations have been proposed in the literature to improve engine thermal management Recent research studies proposed improvements to the engine cooling system One trend is the use of active thermal management components such as electric water pumps which allow better control of engine temperature and reduce overall vehicle fuel consumption through lower parasitic losses of the coolant pump and minimized coolant temperature fluctuations According to Banjac et al 9 advanced thermal topologies of the cooling system were expected to reduce fuel consumption up to 3

They also concluded that with a higher coolant temperature 110 ºC a fuel consumption reduction of 2 5 could be achieved compared to the baseline set point of 90 ºC This would also reduce the warm up period of the engine An advanced thermal management system TMS for a diesel engine was proposed in Fig 5 26 The system included electrically controlled pumps fans and valves in order to enhance the engine performance The main components of an engine cooling circuit for a diesel engine 16 and an advanced engine cooling system are presented in 26 An advanced control of TMS achieved better ability to control the engine temperature and reduced the parasitic losses of the cooling system 27 6 which are often caused by high rotational speed of mechanical components that are coupled with the engine In addition the performance of a variable position electromagnetic thermostat was analyzed by Mohamed 24 in order to provide more flexible control of the engine temperature and coolant mass flow rate The experimental results of the study showed that the approach could reduce the engine warm up time by approximately 28 5 The coolant flow and exhaust emissions were also reduced The fuel consumption in the NEDC cycle was reduced by 9 7 with cold start and 5 2 with hot start 24 Engine warm up time has become an important factor for ICE vehicles 16 It has some impact on passenger thermal comfort in cold conditions but it really can have a great effect on the official fuel economy and emissions that are defined by the standard test cycles such as NEDC and UDDS 28 It was found that in the NEDC oil pre heating could produce a fuel consumption reduction close to 3 16 A numerical method for assessing the benefits of smart engine thermal management was developed by Caresana et al 25 Two ideal cooling engine systems based on engine warm up were developed

The results indicated that greater benefits were found in urban driving cycles where engine loads are light In these conditions an improved thermal management system was found to offer the greatest gains 25 In addition separated cooling structures for the engine head and block was proposed in 29 The research results indicated thermal efficiency increased about 3 due to the decreased auxiliary power friction and heat transfer loss An optimized strategy could also shorten the warm up time by effectively using the electric devices 29 The engine radiator fan may consume an important amount energy in conventional vehicles A mathematical model for a radiator fan array was developed based on laboratory tests with different fan and speed configurations by Wang et al 30 They used mixed integer nonlinear programming to optimize the fan array configuration and operation reaching up to 67 energy savings in fan energy consumption Another factor impacting on the performance of engine thermal systems is the under hood air flow Air flow dissipates heat off the radiator as well as numerous hood components In today's vehicles the engine compartment is fully packed which makes it challenging to implement new thermal system designs for effective air flow The radiator air flow is often compromised for the desire of lower hood designs 31 Thus engine cooling systems can be complicated to design and different simulation methods are typically used For instance three different software were used for the design of engine cooling systems by using a multi physics methodology in order to get a fast design of cooling systems 32 In addition the engine cooling performance has to be effective when there is no air flow for example after rapid engine shut down when there is a risk for coolant boiling

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