Search Results

Boosting technologies have been key enablers for automotive engines development through downsizing and downspeeding. In this situation, numerous multistage boosting systems have appeared in the last decade. The complexity arising from multistage architectures requires an efficient matching methodology to obtain the best overall powertrain performance. The paper presents a model aimed to choose the best 2-stage boosting system architecture able to meet required criteria on boosting pressure, EGR ratios for both short and long route loops while respecting the engine thermo-mechanical limits such as in-cylinder pressure, compressor outlet temperature and exhaust manifold temperature. The model includes filling-and-emptying 0D elements together with mean value. The engine model is set in a way that, for given requirements and boosting system layout, calculates in seconds if the requirements will be achieved and the position of variable geometry, waste-gate, EGR and by-pass valves.

In this paper the performance of a new EGR cooler with double efficiency capabilities is presented. This device allows for temperature modulation between the actual cooled and non-cooled EGR temperature. The cooler has a double circuit in its interior controlled by a valve. The outer dimensions of the cooler remain the same as current fixed geometry coolers. The prototype has been characterized on test flow and thermal efficiency rigs and also tested on the engine test bed. Tests show that for steady partial load conditions little benefits may be achieved in CO and HC emissions with a small increase of NOx emissions. More promising results have been obtained during engine warm-up tests in which significant reductions of HC and CO are attained with low increases of NOx emissions. This shows a potential to reduce CO and HC emissions which are mostly generated during the first stages in the emission certification test in Europe.

Exhaust Gas Recirculation (EGR) is employed widely in compression-ignited engines and currently under consideration for being implemented into spark-ignited engines. EGR cylinder-to-cylinder dispersion is one of the features of such engines that developers are challenged to abate, because low EGR rates increase NOx emissions and excessive EGR rates can produce a significant amount of particulate matter. Taking into account the complex geometries of some automotive manifolds, the treatment of this topic through 3D computational fluid-dynamics (CFD) simulations seems mandatory to study the transport phenomena in a proper way. The main objective of this work is the analysis of the influence of the numerical setup main parameters (mesh, time-step size, turbulence modeling) in a CFD URANS simulation of an automotive engine intake manifold in the EGR distribution.

Despite the development in NOx aftertreatment for Diesel engines, EGR is a cost-effective solution to fulfill current and future emission regulations. There is a wide bibliography discussing the global effects of EGR on combustion and emissions. However, little has been published concerning the effects of the unsuitable EGR and air distribution among cylinders. Since current HSDI engines operate with EGR rates as high as 50% the effect of the unequal EGR distribution becomes important. In addition, cylinder-to-cylinder charge dispersion becomes a critical aspect on the control of low temperature combustion systems. In concordance with the aspects outlined before, the aim of this paper is to study the effects of the EGR cylinder to cylinder distribution on the engine performance and emissions. To cope with this objective, experiments have been conducted in a HSDI engine with two different EGR systems.

Spark ignition (SI) engines are increasing their popularity worldwide since compression ignition (CI) engines have been struggling to comply with new pollutant emission regulations. At the moment, downsizing is the main focus of research on SI engines, decreasing their displacement and using a turbocharging system to compensate this loss in engine size. Exhaust gas recirculation is becoming a popular strategy to address two main issues that arise in heavily downsized turbocharged engines at full load operation: knocking at low engines speeds and fuel enrichment at high engine speeds to protect the turbine. In this research work, a fuel consumption optimization for different operating conditions was performed to operate with a cooled EGR loop, with gasoline and E85. Thus, the benefits of exhaust gas recirculation are proven for a SI gasoline turbocharged direct injection engine.

On actual gasoline turbocharged engines it is common to use a compressor by-pass valve in order to solve the compressor surge problem when the throttle pedal position is released and closes rapidly. The paper deals with a methodology based on experiments to measure the discharge coefficient of an integrated compressor by-pass valve, to understand the possible difference between the steady flow test bench and turbocharger test bench discharge coefficient measurements. To determine if there is some compressor outlet flow field influence due to compressor blades rotation that could modify the discharge coefficient measurement, compared to the steady flow test bench measurements, a fully instrumented turbocharger was used to measure the difference between steady flow test bench and turbocharger test bench discharge coefficients results. Effects of different boundary conditions on turbocharger test bench tests and how they affect the discharge coefficient measurement are also presented.

This paper reports on the global analysis of the EGR circuit in a HSDI diesel engine and its influence on engine transient operation. To achieve this, the employed methodology was a combination of experimental tests and theoretical calculations. The experimental work was performed in a fully instrumented engine test bench equipped with an electronically controlled brake able to simulate the European driving cycle (ECE test cycle). Beside this, the theoretical calculations consisted of simulating the accelerations performed in the ECE test cycle by means of a 1-D gas dynamic code that has been adjusted according to the experimental results. This code takes into account the transport of different species through the engine ducts and has been updated related to the transient feature in order to accept different drag force configurations, road gradients and vehicle specifications.

Degradation of anti-pollutant devices must be taken into account in design so durability of the function is guaranteed over the vehicle lifetime. As for NOx reduction of diesel engines, Exhaust Gas Recirculation (EGR) systems are a well-known and robust solution. However, exposure of the EGR cooler inside this system to the exhaust gas conditions leads to a degradation of its function, affecting to the EGR rate and therefore to potential for NOx reduction. So, sizing and technology of these heat exchangers must be selected to avoid malfunction during vehicle operation. Current scenario in Europe with new homologation cycles and focus on NOx emissions of diesel vehicles under real driving conditions is challenging for the design of EGR systems. This leads to the increase of the areas of the engine map using EGR. Moreover new homologation includes also the use of low ambient temperature.

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.

The purpose of this paper is to describe a methodology based on experimental and theoretical studies for the modeling of typical exhaust systems used in two-stroke small engines. The steady and dynamic behaviors of these systems have been measured in a flow test rig and in an impulse test rig, respectively. Information obtained from these experiments is used in two ways: to find a suitable geometric model to be used in a finite-difference scheme code, and to provide a mean pressure and a frequency domain reflecting boundary, in the frame of a hybrid method. A complete 50cc engine was modeled and comparisons between predicted and measured instantaneous pressure at the exhaust port show a fair agreement, the results of the hybrid approach being more accurate.

The present paper shows the use of a 1-D wave action model in the design process of a sequential parallel turbocharged engine. Even though little information was available at the beginning of the design process, a wave action model was used because of its capability of predicting the behaviour of the new engine. Main issues that were studied by means of simulations are: system architecture, turbochargers matching, prediction of the altitude effect on the turbocharging system, optimization of the transition between different modes, and control system design. The paper also summarises the limitations of the model, mainly concerning combustion process modelling, which were later identified once experimental information was available.