Search Results

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.

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.

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.

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.