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The generalization of exhaust aftertreatment systems along with the growing awareness about climate change is leading to an increasing importance of the efficiency over other criteria during the design of reciprocating engines. Using experimental and theoretical tools to perform detailed global energy balance (GEB) of the engine is a key issue for assessing the potential of different strategies to reduce consumption. With the objective of improving the analysis of GEB, this paper describes a tool that allows calculating the detailed internal repartition of the fuel energy in DI Diesel engines. Starting from the instantaneous in-cylinder pressure, the tool is able to describe the different energy paths thanks to specific submodels for all the relevant subsystems.

To face the current challenges of the automotive industry, there is a need for computational models capable to simulate the engine behavior under low-temperature and low-pressure conditions. Internal combustion engines are complex and have interconnected systems where many processes take place and influence each other. Thus, a global approach to engine simulation is suitable to study the entire engine performance. The circuits that distribute the hydraulic fluids -liquid fuels, coolants and lubricants- are critical subsystems of the engine. This work presents a 0D model which was developed and set up to make possible the simulation of hydraulic circuits in a global engine model. The model is capable of simulating flow and pressure distributions as well as heat transfer processes in a circuit.

The combination of more strict regulation for pollutant and CO2 emissions and the new testing cycles, covering a wider range of transient conditions, makes very interesting the development of predictive tools for engine design and pre-calibration. This paper describes a new integrated Virtual Engine Model (VEMOD) that has been developed as a standalone tool to simulate new standard testing cycles. The VEMOD is based on a wave-action model that carries out the thermo-and fluid dynamics calculation of the gas in each part of the engine. In the model, the engine is represented by means of 1D ducts, while the volumes, such as cylinders and reservoirs, are considered as 0D elements. Different sub-models are included in the VEMOD to take into account all the relevant phenomena. Thus, the combustion process is calculated by the Apparent Combustion Time (ACT) 1D model, responsible for the prediction of the rate of heat release and NOx formation.

In the present work, an automotive Diesel engine has been experimentally tested under a New European Driving Cycle (NEDC) with the aim of getting experimental plots of time dependent partitioning of energy injected during the warm-up process. An additional objective of this work is to assess the energy recovery capacity installed in the engine, i.e., to assess how much of the energy that leaves the engine with the exhaust gasses and the coolant is being employed. With this target, mean values of some parameters (intake and exhaust pressures and temperatures, coolant flow and coolant inlet and outlet temperatures, engine speed and torque) together with instantaneous variables (crankshaft angle, in-cylinder gas pressure, intake and exhaust mass flows) were continuously recorded during the warm-up of the engine. As a result of the work, the dynamics of the thermal balance of the Diesel engine under transient road conditions during the warm-up period was obtained.

In recent years, the spread use of after-treatment systems together with the growing awareness about the climate change is leading to an increase in the importance of the efficiency over other criteria during the design of internal combustion engines. In this sense, it has been demonstrated that performing an energy balance is a suitable methodology to assess the potential of different injection or air management strategies, to reduce consumption as well as determining the more relevant energy terms that could be improved. In this work, an experimental energy balance with the corresponding comprehensive analysis is presented. The main objective is the identification of how the energy is split, considering internal and external balances. For this purpose, some parametric studies varying the coolant temperature, the intake air temperature and the start of the injection timing have been performed. The results quantify the effect of each parametrical study on engine efficiency.