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Journal Article

A New Tool to Perform Global Energy Balances in DI Diesel Engines

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.
Journal Article

General Procedure for the Determination of Heat Transfer Properties in Small Automotive Turbochargers

These days many research efforts on internal combustion engines are centred on optimising turbocharger matching and performance on the engine. In the last years a number of studies have pointed out the strong effect on turbocharger behaviour of heat transfer phenomena. The main difficulty for taking into account these phenomena comes from the little information provided by turbocharger manufacturers. In this background, Original Engine Manufacturers (OEM) need general engineering tools able to provide reasonably precise results in predicting the mentioned heat transfer phenomena. Therefore, the purpose of this work is to provide a procedure, applicable to small automotive turbochargers, able to predict the heat transfer characteristics that can be used in a lumped 1D turbocharger heat transfer model. This model must be suitable to work coupled to whole-engine simulation codes (such as GT-Power or Ricardo WAVE) for being used in global engine models by the OEM.
Technical Paper

Evaluation of EGR Effect on the Global Energy Balance of a High Speed DI Diesel Engine

Regulated emissions and fuel consumption are the main constraints affecting internal combustion engine (ICE) design. Over the years, many techniques have been used with the aim of meeting these limitations. In particular, exhaust gas recirculation (EGR) has proved to be an invaluable solution to reduce NOx emissions in Diesel engines, becoming a widely used technique in production engines. However, its application has a direct effect on fuel consumption due to both the changes in the in-cylinder processes, affecting indicated efficiency, and also on the air management. An analysis, based on the engine Global Energy Balance, is presented to thoroughly assess the behavior of a HSDI Diesel engine under variable EGR conditions at different operating points. The tests have been carried out keeping constant the conditions at the IVC and the combustion centering.
Technical Paper

Development and Validation of a Submodel for Thermal Exchanges in the Hydraulic Circuits of a Global Engine Model

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.
Technical Paper

Numerical Study of the Maximum Impact on Engine Efficiency When Insulating the Engine Exhaust Manifold and Ports during Steady and Transient Conditions

In the present work, a study about the impact on engine performance, fuel consumption and turbine inlet and outlet temperatures with the addition of thermal insulation to the exhaust ports, manifold and pipes before the turbocharger of a 1.6L Diesel engine is presented. First, a 0D/1D model of the engine was developed and thoroughly validated by means of an extensive testing campaign. The validation was performed by means of steady state and transient running conditions and in two different room temperatures: 20°C and -7°C. Once the validation was complete, in order to evaluate the maximum gain by means of insulating materials, the exhaust air path before the turbine was simulated as adiabatic. Results showed that the thermal insulation proved to have a great potential in regard to T4 increase that would lead to a reduction of the warm up time of the aftertreatment systems. However, its impact on engine efficiency was limited in both steady and transient conditions.
Journal Article

Importance of Heat Transfer Phenomena in Small Turbochargers for Passenger Car Applications

Nowadays turbocharging the internal combustion engine has become a key point in both the reduction of pollutant emissions and the improvement of engine performance. The matching between turbocharger and engine is difficult; some of the reasons are the highly unsteady flow and the variety of diabatic and off-design conditions the turbocharger works with. In present paper the importance of the heat transfer phenomena inside small automotive turbochargers will be analyzed. These phenomena will be studied from the point of view of internal heat transfer between turbine and compressor and with a one-dimensional approach. A series of tests in a gas stand, with steady and pulsating hot flow in the turbine side, will be modeled to show the good agreement in turbocharger enthalpies prediction. The goodness of the model will be also shown predicting turbine and compressor outlet temperatures.
Journal Article

A Combination of Swirl Ratio and Injection Strategy to Increase Engine Efficiency

Growing awareness about CO2 emissions and their environmental implications are leading to an increase in the importance of thermal efficiency as criteria to design internal combustion engines (ICE). Heat transfer to the combustion chamber walls contributes to a decrease in the indicated efficiency. A strategy explored in this study to mitigate this efficiency loss is to promote low swirl conditions in the combustion chamber by using low swirl ratios. A decrease in swirl ratio leads to a reduction in heat transfer, but unfortunately, it can also lead to worsening of combustion development and a decrease in the gross indicated efficiency. Moreover, pumping work plays also an important role due to the effect of reduced intake restriction to generate the swirl motion. Current research evaluates the effect of a dedicated injection strategy to enhance combustion process when low swirl is used.