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The increasingly restrictive legislation on pollutant emissions is involving new homologation procedures driven to be representative of real driving emissions. This context demands an update of the modelling tools leading to an accurate assessment of the engine and aftertreatment systems performance at the same time as these complex systems are understood as a single element. In addition, virtual engine models must retain the accuracy while reducing the computational effort to get closer to real-time computation. It makes them useful for pre-design and calibration but also potentially applicable to on-board diagnostics purposes. This paper responds to these requirements presenting a lumped modelling approach for the simulation of aftertreatment systems.

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.

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.

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.

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.

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.

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.

An acoustic one-dimensional compressor model has been developed. This model is based on compressor map information and it is able to predict how the pressure waves are transmitted and reflected by the compressor. This is later on necessary to predict radiated noise at the intake orifice. The fluid-dynamic behavior of the compressor has been reproduced by simplifying the real geometry in zero-dimensional and one-dimensional elements with acoustic purposes. These elements are responsible for attenuating or reflecting the pressure pulses generated by the engine. In order to compensate the effect of these elements in the mean flow variables, the model uses a corrected compressor map. Despite of the fact that the compressor model was developed originally as a part of the OpenWAM™ software, it can be exported to other commercial wave action models. An example is provided of exporting the described model to GT-Power™.

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.