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The turbine, an enabling component of turbochargers, is a seat of highly complex unsteady flow as well as varying gas compositions between diesel and gasoline engines. Thus, it is necessary to take into account different physical models when simulating such turbines. Researchers have often considered the turbine working gas as air, which may not lead to an accurate prediction of actual turbine characteristics. In the present work, the effect of the working gas on the performance of turbocharger turbines as well as on the turbo lag was investigated through a set of numerical simulations for six wastegate opening degrees from 0% up to 100% and under a wide range of the flow pulse frequency ranging from 33.33 up to 166.66 Hz. Four working fluids were involved in this study which are the gasoline burnt gas, diesel burnt gas, air with like gasoline engine waves, and air with like diesel engine waves. The performance of the turbine and its responsiveness quantified as the time lag with burnt gases from both diesel and gasoline engines were compared to those with air. Results showed totally deviated unsteady performance characteristics compared to the turbine working with air. Results also confirmed that considering the working fluid as air may not lead to a fair representation of the actual turbine performance characteristics. The findings of this work put emphasis on the importance of the gas composition when modeling such turbines by engineers especially during the design process where a good turbocharger-engine match has to be met. [ABSTRACT FROM AUTHOR]

The purpose of the paper is to study the heat transfer in the exhaust manifold of a naturally aspirated diesel engine. The work has started from the exhaust manifold of the test engine D30 which was redesigned in CATIA V5, then pre-processed in Comsol Multiphysics. The results of the post-processing phase have generated temperature, velocity, pressure and Reynolds number fields which were compared with experimental data from engine dynamometric test. For a higher accuracy the temperatures of exhaust manifold surfaces were measured both with IR Camera Imager and thermocouples. [ABSTRACT FROM AUTHOR]

Modern diesel engines are struggling to enhance the power density. This is usually realized by being equipped with a turbocharger, which demands higher performances on exhaust flow and exhaust waste energy recovery (WER). In the present study, we investigated the variations of exhaust flow and exhaust energy recovery performance with different geometrical parameters of exhaust system and proposed an evaluation and optimal design method of the exhaust system for a turbocharging diesel engine with a module pulse converter (MPC) system. The macro engine performances and the micro flow fields in exhaust system are obtained from the one/three dimensional (1D-3D) coupling simulation, and the energy of exhaust gas is quantified and analyzed with a concept of air power. It can be concluded that with a view to the exhaust performance and exhaust energy utilization, the diameter of the exhaust pipe should be set equal to the outlet diameter of the manifold and there is an optimized value of the contraction rate of the exhaust manifold. Besides, a parameter of the exhaust system called power potential coefficient is proposed to qualitatively evaluate the exhaust performance and exhaust energy. [ABSTRACT FROM AUTHOR]

The flow characteristics in the exhaust manifold and close-coupled catalytic converter (CCC) system of a spark-ignition engine have a major influence on its performance and emission characteristics. In particular, understanding the exhaust flow characteristics during engine operation is crucial in terms of shortening the catalyst light-off and enhancing its conversion efficiency. In this study, to understand the pulsating nature of the exhaust flow under engine firing conditions, transient velocity measurements using laser Doppler velocimetry were performed inside an exhaust system with CCC. First, the effects of engine parameters (speed and load) on the pulsating behavior of the exhaust flow were investigated. Moreover, the effects of the exhaust manifold geometric configuration on the pulsating flow characteristics are presented. It is expected that the data obtained from this study can be used to improve exhaust system design for robust emission control in terms of catalyst light-off and durability. [ABSTRACT FROM AUTHOR]

The present experimental study deals with a pulsatile turbulent flow simulating the exhaust flow of an automotive engine. In the experiments, a four-cylinder engine is used as an exhaust-flow generator to realize flow conditions close to those in an engine environment. Particle image velocimetry (PIV) measurements visualize the flow field in an S-shaped double-bend duct at a Reynolds number of 48,000 and a Womersley number of 70.9. Stereo PIV, which is classified as a two-dimensional three-component measurement, is conducted in the duct cross sections located downstream of the bends. The stereo PIV system is synchronized with the engine operation to enable phase-locked measurements at particular phases, and the phase-averaged results show the large-scale vortical structures and the duct axial velocity distribution. Downstream of the first bend, the secondary flow consists of vortices that circulate as Dean-type vortices. Downstream of the second bend, by contrast, vortices that circulate in opposite directions to the Dean-type vortices, so-called Lyne-type vortices, form in the core of the cross section. These secondary flows persist without significant changes in their large-scale vortical structures over time. Time-resolved PIV is conducted to track the temporal evolution of the flow in the bend planes. The results show that the flow reverses locally along the inner wall of the bends during flow deceleration. Snapshot proper orthogonal decomposition (POD) is used on the time-resolved PIV data to extract the significant flow structure from the instantaneous field. We propose POD as a good post-processing tool for the instantaneous data of pulsatile cases.

In this paper a new leakage current sensor is installed on a diesel engine to detect the failure of diesel particulate filter (DPF). The software Fluent is used to determine the optimum installing position of the PM sensor downstream the DPF. Six types of installation positions were studied in this research, visualizing each velocity distribution position of the system. The optimum exhaust sensor absorption position (position II) was determined through axial and radial adjustments. Afterwards, the pressure distribution of the whole system and the particulate distribution in the sensor at location II were further analyzed. Also, the output signal of the sensor at different operation conditions were experimentally analyzed and tested on an engine test bench. Besides, the signal output of voltage downstream the damaged DPFs, agrees well with the smoke intensity values, which validates the viability of the PM concentration transient test of the PM sensor system. Influences of different exhaust temperature on sensor signal output were investigated with the aid of an electrical heating system, at constant engine operating conditions. Unfortunately, the experiment showed that the temperature had a negative effect on the signal output, which makes the sensitivity of the sensor lower. [ABSTRACT FROM AUTHOR]

This paper presents a new methodology for measurement of the instantaneous average exhaust mass flow rate in reciprocating internal combustion engines to be used to determinate real driving emissions on light duty vehicles, as part of a Portable Emission Measurement System (PEMS). Firstly a flow meter, named MIVECO flow meter, was designed based on a Pitot tube adapted to exhaust gases which are characterized by moisture and particle content, rapid changes in flow rate and chemical composition, pulsating and reverse flow at very low engine speed. Then, an off-line methodology was developed to calculate the instantaneous average flow, considering the “square root error” phenomenon. The paper includes the theoretical fundamentals, the developed flow meter specifications, the calibration tests, the description of the proposed off-line methodology and the results of the validation test carried out in a chassis dynamometer, where the validity of the mass flow meter and the methodology developed are demonstrated. [ABSTRACT FROM AUTHOR]