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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.

0D-1D codes allow researchers to obtain a prediction of the behavior of internal combustion engines with little computational effort. One of the submodels of such codes is devoted to the centrifugal compressor. This model is often based on the compressor performance maps, therefore requiring the extrapolation of the maps so that all possible operating conditions are covered. Particularly, a suitable extrapolation of isentropic efficiency map is sought. This work first examines different available methods for compressor efficiency extrapolation into off-design conditions. No method is found to provide satisfactory results at all extrapolated regions: low and high compressor speeds and low compression ratio at measured speeds. Hence, a new method is proposed and its accuracy is assessed with the aid of compressor off-design measurements.

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.

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.

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.

Surge occurrence in automotive engine turbochargers is known to be dependent on the installation conditions. It is proven that the flow pattern produced by the inlet ducting at the compressor inducer modifies surge margin. But also the engine intake line acoustics, both compressor upstream and downstream, affects turbocharger surge. In the paper the effect of different parameters in the intake line geometry on compressor surge is investigated. Modifications in the air filter volume, compressor inlet geometry and compressor outlet length have been considered. Surge limit obtained on a steady gas-stand is compared to those measured on the engine test bench using two different methodologies. Testing results show significant differences in term of surge line shift and the corresponding engine low end torque. A 1D model of the engine has been built using a non-steady compressor model able to predict surge occurrence.

Although in combustion diagnosis models the uncertainty in the trapped mass is not critical, different authors have reported non negligible effects on the rate of heat release. Usually, an emptying-and-filling model is used to estimate the residual mass, whence the trapped mass is obtained. Generally, the instantaneous pressure at the intake and exhaust ports are not measured for combustion diagnosis applications and hence, it is difficult to estimate accurate values of the residual mass. The objective of this work is to propose a simple physical model to estimate the residual mass in a DI Diesel engine for a combustion diagnosis model. The proposed model specially focuses on the exhaust port conditions, because they appear to be the most important factor affecting the residual mass estimation.

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.

Measurement systems are becoming more complex and test beds are usually automated; high measurement accuracy is also required. However it is common that measurement failures are only detected in the post-processing, resulting in important time and economic loss. Due to the huge amount of sensor signals, the online validation of the data is very time-consuming and infeasible without computer aid. In this study a failure detection framework is used for data plausibility analysis. This failure detection methodology is able to deal with generic models relating different measure channels. The general approach incorporates model and sensor inaccuracies in the evaluation procedure. Additionally, a useful set of physical equations applicable for failure detection in engine test bends is presented. These equations are combined with data-driven models allowing satisfactory detection rates while maintaining a low rate of false alarms.

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.

The scavenging and injection processes on a 50 cc. crankcase-scavenged compressed air-assisted direct fuel injection 2-stroke engine are analyzed by means of multidimensional CFD modeling. A moving mesh including the intake ports, cylinder and exhaust port has been built, solving the interface at ports. The information at boundaries is obtained from a one-dimensional wave action model. A detailed analysis of the scavenging process is presented. A motored engine with suitable optical access has been used to measure in-cylinder velocities by Laser Doppler Velocimetry LDV. Due to the small engine size some technical problems had to be solved to carry out the measurements. The comparison between the modeled and measured velocities shows good agreement. Finally, the validated multidimensional modeling has been used for the optimization of the injection process in terms of fuel short-circuit to the exhaust and also of mixture quality.

In the paper is described how to characterise the combustion process of a high speed turbocharged direct injection diesel engine (HSDI) during a transient process, which consists on a full load acceleration at constant engine speed, known as load transient. The combustion characterisation is based on the cycle to cycle combustion analysis and the Rate of Heat Release calculation (RoHR). The information presented in the paper includes, the transient recorded data at three different engine speeds joint with information about transducers characteristics and measurement frequencies. The post-processing of the obtained information and its synchronization is described in detail; a protocol of the process is finally obtained. The RoHR of every transient cycle is calculated and shown as final objective of the work.

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.

A theoretical-experimental study is presented in the paper, whose objective is to propose a method that allows determining the average efficiency of the radial turbines, usually employed in the internal combustion engines, under real operating conditions. Due to the unsteady behaviour of the exhaust gasses flow, the efficiency information obtained from steady flow tests cannot be considered when the turbine is connected to an internal combustion engine. The efficiency differences between steady and unsteady flow patterns, can be obtained by testing the turbine, connected to the engine, under real pulsating flow conditions. For the correct turbine workflow characterisation, a wave action model has been used, together with information obtained from engine tests. The engine test cell includes a specific measuring device for this purpose. The results obtained have been compared with those provided by the turbine manufacturer.

The purpose of this paper is to present the results of a study on the exhaust junctions geometry. Twelve three-branch junctions of different geometry have been tested on a single cylinder engine. The parameters studied have been exhaust junction outlet-to-inlet diameter ratio, length, angle between inlet branches and the existence of a reed separating inlet branches. An analysis of the pressure waves amplitude (incident, reflected and transmitted) obtained from instantaneous pressure measurements in some locations around the junction has been carried out. The analysis of results shows that junction length has a low influence on its behavior. The ratio between inlet and outlet branches diameters increases both reflection and directionality (avoiding pressure wave transmission to the adjacent branch). The existence of a reed separating the inlet flows may increase directionality with moderate pressure losses if the throat area is not reduced.