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Technical Paper

Torso Improvements in Child Dummies Used for Certification Tests in Europe

Child dummies used in certification dynamic tests have not been improved since their marketing and their approval as European regulation dummies. Their main shortcoming lies in a too high and therefore unrealistic stiffness of the torso front part. The paper addresses a study carried out in the aim of solving this problem. It includes two parts: in a first section, the changes brought to the dummy torso and intended to improve its biofidelity and to reduce stiffness drastically are described. In order to reach such an objective, the lower part of the upper torso was remodelled; the pelvis profile was redefined and the geometrical and mechanical characteristics of the foam used for the abdominal insert were changed. The results obtained using two transducers installed in the abdominal section are then presented. The measurement principle of the first transducer consists in a pressure measurement, and the principle of the second one in a load measurement.
Technical Paper

Integration and Validation of Sheet Metal Forming Simulation Computer Programs Into the Design Process

In order to improve the design of drawn parts and to reduce the number of trial and error tests, Renault has undertaken the development and the validation of various finite element procedures and codes. This paper describes the function of each software and its level of integration into the design process. One of them is already an operational tool used be planners whilst the others are still in the validation phase. Selected examples show typical applications of the computer programs on automotive parts.
Technical Paper

Fatigue Analysis of Conrod Bearing

For many years, bearing suppliers have been using the specific pressure to evaluate the fatigue risk of conrod bearings. However, modern engines have made the bearing more sensitive to various phenomena such as the thermal expansion or the elasticity of the conrod housing. These effects modify the stresses in the bearing layers and consequently fatigue risk. In this paper, we propose a new way to determine the bearing fatigue resistance. To achieve that, we analyze the elastic and plastic behavior of the bearing along the engine life. We detail and provide the analytical relationships which determine stresses in the overlay and in the substrate of the bearing in order to analyze their fatigue resistance. Various physical loads are taken into account such as the thermal load, the hydrodynamic pressure field, the fitting load, the free spread load. A good knowledge of the relationships between those physical phenomena helps to understand the mechanical behavior of the bearing.
Technical Paper

The Potential of Highly Premixed Combustion for Pollutant Control in an Automotive Two-Stroke HSDI Diesel Engine

An innovative alternative to overcome the load limits of the early injection highly premixed combustion concept consists of taking advantage of the intrinsic characteristics of two-stroke engines, since they can attain the full load torque of a four-stroke engine as the addition of two medium load cycles, where the implementation of this combustion concept could be promising. In this frame, the main objective of this investigation focuses on evaluating the potential of the early injection HPC concept using a conventional diesel fuel combined with a two-stroke poppet valves engine architecture for pollutant control, while keeping a competitive engine efficiency. On a first stage, the HPC concept was implemented at low engine load, where the concept is expected to provide the best results, by advancing the start of injection towards the compression stroke and it was confirmed how it is possible to reduce NOX and soot emissions, but increasing HC and CO emissions.
Technical Paper

Compressor Efficiency Extrapolation for 0D-1D Engine Simulations

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.
Technical Paper

Experimental Study of Automotive Turbocharger Turbine Performance Maps Extrapolation

Engine downsizing is potentially one of the most effective strategies being explored to improve fuel economy. A main problem of downsizing using a turbocharger is the small range of stable functioning of the turbocharger centrifugal compressor at high boost pressures, and hence the measurement of the performance maps of both compressor and turbine. Automotive manufacturers use mainly numerical simulations for internal combustion engines simulations, hence the need of an accurate extrapolation model to get a complete turbine performance map. These complete maps are then used for internal combustion engines calibration. Automotive manufacturers use commercial softwares to extrapolate the turbine narrow performance maps, both mass flow characteristics and the efficiency curve.
Technical Paper

System Optimization for a 2-Stroke Diesel Engine with a Turbo Super Configuration Supporting Fuel Economy Improvement of Next Generation Engines

The objective of this paper is to present the results of the GT Power calibration with engine test results of the air loop system technology down selection described in the SAE Paper No. 2012-01-0831. Two specific boosting systems were identified as the preferred path forward: (1) Super-turbo with two speed Roots type supercharger, (2) Super-turbo with centrifugal mechanical compressor and CVT transmission both downstream a Fixed Geometry Turbine. The initial performance validation of the boosting hardware in the gas stand and the calibration of the GT Power model developed is described. The calibration leverages data coming from the tests on a 2 cylinder 2-stroke 0.73L diesel engine. The initial flow bench results suggested the need for a revision of the turbo matching due to the big gap in performance between predicted maps and real data. This activity was performed using Honeywell turbocharger solutions spacing from fixed geometry waste gate to variable nozzle turbo (VNT).
Technical Paper

Modeling of Pressure-Swirl Atomizers for GDI Engines

A new simulation approach to the modeling of the whole fuel injection process within a common-rail fuel injection system for direct-injection gasoline engines, including the pressure-swirl atomizer and the conical hollow-cone spray formed at the nozzle exit, is presented. The flow development in the common-rail fuel injection system is simulated using an 1-D model which accounts for the wave dynamics within the system and predicts the actual injection pressure and injection rate throughout the nozzle. The details of the flow inside its various flow passages and the discharge hole of the pressure-swirl atomizer are investigated using a two-phase CFD model which calculates the location of the liquid-gas interface using the VOF method and estimates the transient formation of the liquid film developing on the walls of the discharge hole due to the centrifugal forces acting on the swirling fluid.
Technical Paper

Experimental Investigation on the Characteristics and on the Reproducibility of the Flow issuing from a High-Pressure Direct-Injection Nozzle

This paper presents an investigation on the experimental determination of some characteristics of the flow issuing from a swirl injector dedicated to direct-injection spark-ignited engines. The reproducibility, from one injection to another, of the temporal evolution of the liquid flow characteristics during the opening of the injector was investigated. This was achieved by using a high-speed film camera set at 8,000 images/s. The resulting visualizations allowed us to measure the evolution of the penetration length and velocity as well as of the liquid cone angle. It was found that the spray produced is a low momentum spray whose penetration length and velocity are small. The good reproducibility of the temporal evolution of the liquid flow characteristics has been obtained, except for the liquid cone angle during the opening stage. A fast-shutter video camera was also used to make images of the early development of the issuing liquid flow.
Technical Paper

Analysis of the Dynamics of a Hydraulic Control Circuit of an Automatic Gearbox

The description of the supply pressure hydraulic circuit and the couplings between its components are presented. A comparison between simulations and experiments is carried out. Using some linear facilities, it is possible to conclude that the low frequency modes mainly correspond to the wave effects of hydraulic lines which connect valves to each other. In order to maintain a pressure in the supply circuit, an electronic pressure control is necessary. The design of a control law needs to build different linear models for different levels of pressure since the system is very non linear. Three transfer functions are found for three pressure levels. These transfer functions are very similar to the ones used by the automatic control department and obtained by experiments. Using these transfer functions it is possible to design the control law.
Technical Paper

Influence of the Micro- and Macro-Structural Parameters on the Dynamic Behavior of Structures Made of Polymers Reinforced with Short Glass Fibers

In order to design vehicles with diminished gCO2/km emissions level, car manufacturers aim at reducing the weight of their vehicles. One of the solutions advocated by the automotive industry consists in the replacement of metallic parts by lighter systems made of polymer reinforced composites. Unfortunately, the numerical simulations set to evaluate the vibratory and acoustic performances of systems made of this kind of materials are often not sufficiently effective and robust so that convincing test/simulation correlations are rarely met. Indeed, for polymer-based materials, numerous parameters affect the vibroacoustic behavior. On the one hand, it is well known that the viscoelastic properties (Storage -Young- and dissipative moduli) of polymers depend on the temperature, loading frequency and sometimes the humidity content.
Journal Article

Establishing New Correlations Between In-Cylinder Charge Motion and Combustion Process in Gasoline Engines Through a Numerical DOE

This paper presents an innovative methodology and the corresponding results of a study whose goal is to identify the main links between in-cylinder charge motion and the development of combustion without taking into consideration how to create this charge motion (shape of the intake ducts, valve timing, etc …). During this study a specific methodology was developed and used. It is based on the calculation of a “3D numerical test bench” matrix planned following the Design Of Experiments method. Many aerodynamic configurations obtained by combining the three main aerodynamic motions with several different intensities (tumble, cross-tumble or swirl) at the intake valve closing were calculated.
Technical Paper

Calculation process with Lattice Boltzmann and Finite Element methods to choose the best exterior design for wind noise

Authors : Guillaume BAUDET, Cécile DUTRION, Rémi LORENZI, Félix GENDRE, Shanshan GENG Renault Automotive wind noise is a complex phenomenon. Noise in the cabin depends of: - The exterior loading due to the flow around the vehicle - The transfer loss of seals and panels - The acoustic transfer function of the cabin Each part of this cascading must optimized to have a good final performance. So the exterior design is a key parameter because it influence the loading (pressure field) on the vehicle panels and seals. For some years, we know that the exterior loading is split in two parts: - Hydrodynamic (or turbulent) loading with high wave number pressure field - Acoustic loading with low wave number pressure field In this paper, we present a calculation process which enables to predict the acoustic source created by the lateral window at high speed which has a major contribution to the interior noise.