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The present paper aims at developing a novel methodology to create a one-dimensional simulation model for an automotive turbocharged gasoline engine. The gas-path modeling of the engine, which includes a variable nozzle turbine (VNT) and variable valve timing (VVT) strategies, is described in detail. The model calibration procedure is mainly distinguished by isolating the different engine parts, decoupling the turbocharger, using PI controls to find fitting parameters and checking and validating mean and crank-angle resolved variables. To handle model limitations, it requires experimental data and a previous combustion analysis of some steady operating points. The methodology is completed with the determination of fitting correlations to estimate heat losses and pressure drops in engine systems. It also includes the training of an Artificial Neural Network (ANN) to predict the combustion process and the integration into the model and final validation.

In a context of increasing emission regulations, turbocharged gasoline engines are increasingly present in the automotive industry. In particular, the twin-entry and double-entry radial inflow turbines are widespread used technologies to avoid interferences between exhaust process of consecutive firing order cylinders. In this study, a passenger car twin-entry type turbine has been tested under highly pulsating flow conditions by means of a specifically built gas stand, trying to perform pulses with similar features as the ones that can be found in a real reciprocating engine. For this purpose, the turbine has been instrumented with multiple pressure, temperature and mass flow sensors, using a uniquely designed rotating valve for generating the pulses. The test bench setup is flexible enough to perform pulses in both inlet branches separately as well as to use hot or ambient conditions with minimal changes in the installation.

The growing concerns about emissions in internal combustion engines, makes necessary a good prediction of the after-treatment inlet temperature in fast one-dimensional engine simulation codes. Different simple models have been developed during the last years which improve the prediction of the turbocharger heat transfer phenomena. Although these models produce good results when computing the turbine outlet temperature, those models focus on the axial heat transfer paths and lack the capability of producing detailed results about the internal thermal behavior of the turbocharger. In this work, a new version of heat transfer model for automotive turbochargers is presented. This model discretizes the turbocharger in both the radial and axial directions, and computes the heat transfer and temperature at different parts of the machine. Aiming for a low computational cost, it was designed to be compatible with fast one-dimensional engine simulations as a replacement of previous models [1].

Upcoming emissions regulations will force to optimize aftertreatment system to reduce emissions looking for lack of fuel penalty. Despite advances in purely aftertreatment aspects, the performance of the diverse aftertreatment devices is very dependent on the operating temperature. This makes them rely on the engine design and calibration because of the imposed turbine outlet temperature. The need to reach target conversion efficiency and to complete regeneration processes requires controlling additional parameters during the engine setup. For that reason, exploring the potential of different solutions to increase inlet aftertreatment temperature is becoming a critical topic. Nevertheless, such studies cannot be tackled without considering concerns on the engine fuel consumption. In this paper, the influence of several design parameters is studied by modelling approach under steady state operating conditions in a Diesel engine.

The abatement of nitrogen oxides emissions is a topic of major concern for automotive manufacturers. In addition to aftertreatment solutions such as LNT or SCR devices, the use of exhaust gas recirculation (EGR) is necessary in most of the applications to meet emissions regulations. Due to the high specific humidity of the exhaust gases, a high condensate flow may be generated if EGR gases are significantly cooled down. In the case of long-route EGR (LR-EGR) usage, this condensate flow would reach the compressor wheel. This paper explores the variables governing the condensation process and the potential effects of the liquid droplets and streams on the compressor wheel durability combining experimental and theoretical approach. For this purpose, visualization of both the condensate flow and the compressor wheel are performed. Tests are conducted in a flow test rig in which LR-EGR water content is reproduced by water injection on the hot air mass flow.

This paper presents an experimental analysis on the effect of thermal insulation of engine internal walls on the performance and emissions of a heavy-duty diesel engine. Some parts of the engine, like pistons, cylinder head and exhaust manifold were thermally insulated from gas contact side in order to reduce heat losses through the walls. Each component has been analyzed, independently, and in combination with others. The results have been compared with that of the original engine configuration. The analysis focuses on NOx and, smoke emissions along with brake specific fuel consumption. In order to take advantage of the engine insulation, an optimization of the air management and injection settings was finally performed, which provided the best combination for each engine configuration.

Wall-flow diesel particulate filters have become the most effective system for particulate matter abatement in Diesel engines being required for current and future emission standards fulfillment. Despite the high filtration efficiency that wall-flow DPFs exhibit their use involves a noticeable impact in fuel consumption because of the increase of the exhaust back-pressure. Additionally, the fuel economy penalty increases as the DPF becomes soot/ash loaded. This constraint demands the approach and development of new solutions to reduce the DPF pressure drop. This paper focuses on the improvement of the ratio between the pressure drop and the loading by means of pre-DPF water injection. A proper management of the water injection events is able to completely remove the dependence between these magnitudes. The test campaign and the discussion of the experimental results address how the DPF pressure drop reduction leads to benefits in engine fuel consumption.

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.

Calibration of internal combustion engines at different altitudes, above or below sea level, is important to improve engine performance and to reduce fuel consumption and emissions in these conditions. In this work, a flow test rig that reproduces altitude pressure variation is presented. The system stands out by its altitude range, compactness, portability and easy control. It is based on the use of turbomachinery to provide the target pressure to the engine intake and exhaust lines. The core of the system is composed of a variable geometry turbine (VGT) with a waste-gate (WG) and a mechanical compressor. Given a set of turbomachinery systems, the operation pressure and the air mass flow are controlled by the speed of the mechanical compressor and the VGT and WG position. A simple modification in the installation setup makes possible to change the operating mode from vacuum to overpressure. So that simulating altitude increase or decrease with the same flow test rig components.

Nowadays turbocharging the internal combustion engine has become an essential tool in the automotive industry to meet downsizing technique requirements. In that context turbocharger unsteadiness is huge since both turbine and compressor work under high pulsating flow conditions, being turbocharger behavior prediction more difficult but still key for matching and predicting ICE performance. The well understanding and modeling of the occurring physical phenomena during turbocharger unsteady and off-design operation seems crucial. In this paper three small radial turbines used in turbochargers from passenger car applications have been tested under high temperature and pulsating flow conditions on the turbine side. A gas stand and a rotary valve installed on the turbine inlet have been used to reproduce pulses with desired characteristics. A beam-forming technique for pressure wave's decomposition has been used to analyze turbine performance in detail.

Pre-turbo aftertreatment systems benefit from an increase of the temperature across the monolith reducing the time up to DOC light-off and reaching better conditions for passive regeneration in the DPF. The engine performance is also improved by reducing the specific fuel consumption. The pumping work diminishes because of the lower aftertreatment pressure drop due to the higher gas density. Additionally, the aftertreatment pressure drop is not multiplied by the turbine expansion ratio to set the engine back-pressure, which becomes lower. It also makes the DPF pressure drop less dependent on the soot mass loading. In this context, the traditional ratio between engine displacement and DOC & DPF volume in post-turbo aftertreatment placement needs to be reviewed in pre-turbo applications as a way to optimize savings in fuel consumption and aftertreatment manufacturing cost.

This work presents a study to characterize and quantify the mechanical losses in small automotive turbocharging systems. An experimental methodology to obtain the losses in the power transmission between the turbine and the compressor is presented. The experimental methodology is used during a measurement campaign of three different automotive turbochargers for petrol and diesel engines with displacements ranging from 1.2 l to 2.0 l and the results are presented. With this experimental data, a fast computational model is fitted and used to predict the behaviour of mechanical losses during stationary and pulsating flow conditions, showing good agreement with the experimental results. During pulsating flow conditions, the delay between compressor and turbine makes the mechanical efficiency fluctuate. These fluctuations are shown to be critical in order to predict the turbocharger behaviour.

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.

Problems in the turbocharger lubrication system can cause serious deterioration in their overall performance and even their complete destruction. The paper describes several tests with different critical lubrication conditions, in order to determine the thresholds at which the operation may be appropriate. In an IC engine, these problems can be produced mainly by several factors: the decreasing in the supply pressure of the oil, a delay in the lubrication oil pressure and an intermittent lubrication interruption. A turbocharger test bench and an IC engine test bench has been used to test the turbocharger, in order to reproduce the conditions and cycles similar to the operation of the turbocharger in an IC engine (pressures, temperatures, mass flows, accelerations, etc..). Thermodynamic variables and mechanic variables measured in the tests help to identify some of the operating limits of lubrication in critical conditions.

The pressure drop across the aftertreatment systems directly affects the fuel economy as a function of the flow characteristics and also the soot loading in the case of the Diesel particulate filter. However, the relative position of this system with respect to the turbine has an additional effect which is dependent on the influence of the turbine expansion ratio. When the DPF is placed upstream of the turbine, its pressure drop is not affected by the multiplicative effect of the turbine expansion ratio to set the exhaust manifold pressure. This work concentrates on the analysis of the influence that the aftertreatment pressure drop has on the engine performance depending on the DPF soot loading and the location of the aftertreatment with respect to the turbine. The interaction with the turbocharger and the EGR operation is also analyzed taking as reference a two stage turbocharger heavy duty Diesel engine.

The use of particulate filters (DPF) has become in recent years the state of the art technology for the reduction of soot aerosol emissions for light, medium and heavy duty Diesel vehicles. However, the effect of the system location on engine performance is a key aspect that should be studied. In the present work a numerical study has been carried out with the objective to analyze the effect on the engine performance of an innovative DPF placement upstream of the turbine. This study has been performed by means of the gas dynamic simulation of a two-stage turbocharged heavy duty Diesel engine, which has been previously modeled from experimental data obtained under steady state conditions. The original DPF has been divided into two monoliths for the case of the pre-turbo DPF configuration. Three cylinders discharge in each of these monoliths and after the filtration the flow is driven towards the high-pressure turbine and the EGR system.

Characterization of radial turbine performance is usually represented by turbine characteristics maps. These maps illustrate the relationship between the most representative variables which describe the system behavior. Many times, due to design constrains available in these test beds, it is not possible to get measurements of the different variables at different turbine rotational speeds over a wide range of expansion ratios. Sometimes this represents a problem when an appropriate engine simulation must be carried out due to the lack of reliable information to run the simulation in operation points where there are no available turbine data. Although an extrapolation could be done using mathematical methods, there are no physics behind which assures an acceptable confidence in the new generated information. The present paper develops a physics based method for the extrapolation of the radial turbine maps to zones where there is no experimental information.

The paper analyses a procedure, based on thermodynamics concepts, to calculate the isentropic outlet temperature taking into account the changes in specific heat during the thermodynamic process; the results obtained were compared whit those given by the traditional methods. Besides, using data from tests, performed in a specific turbochargers test bench, the differences in isentropic efficiency have been evaluated and compared too. Moreover, another factor related with the influence of the gas specific heat on turbocharger performance is the effect that the humidity contents on gas has on the efficiency calculations. Normally, ambient conditions are taken into account just to obtain the corrected values of the main variables in compressor calculations, however the humidity ratio is not included and its effect is neglected. This study presents also a theoretical- experimental analysis about the effect of taking into account this factor.

The influence of turbine inlet gas temperature on turbocharger performance is a topic discussed recently by many authors. Some studies present results on adiabatic operation by insulating the turbocharger from ambient conditions and report significant differences in compressor isentropic efficiency. Other authors perform non-adiabatic tests and report a significant influence on compressor isentropic efficiency only at the lowest turbocharger speed. In present work two different levels of gas temperature at the inlet of a Variable Geometry Turbine (VGT) have been tested at two different vane positions and two different corrected turbine speeds. Temperatures have been measured in the outer cases of turbine and compressor in order to determine the radiated power and their relative importance with respect to different power definitions obtained from turbocharger operative variables. The obtained results show the influence on both compressor and turbine isentropic efficiency.

Modern DI Diesel engines are widely used in automotive applications. Improvements in performance and emissions have been produced in the last ten years on these engines, so that they are now very competitive in comparison with petrol engines. However, cold startability is one of the main challenges of Diesel engines, since great differences with petrol engines still can be noticed. Today, in small engines glow plugs are universally used as an aid system for cold start. In large engines, where the cold start is less critical, intake air heating technology is employed. In this paper the application of this technology to small engines is evaluated in terms of its viability for cold starting and HC/CO emissions and combustion noise reduction during the warm-up phase of the engine.