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Transfer path analysis is a powerful tool to support the vehicle NVH development. On the one hand it is a fast method to gain an overview of the complex interplay in the vehicle noise generation process. On the other hand it can be used to identify critical noise paths and vehicle components responsible for specific noise phenomena. FEV has developed several tools, which are adapted to the considered noise phenomena: Powertrain induced interior noise and vibration is analyzed by VINS (Vehicle Interior Noise Simulation), which allows the deduction of improvement measures fast enough for application in the accelerated vehicle development process. Further on vehicle/powertrain combinations not realized in hardware can be evaluated by virtual installation of the powertrain in the vehicle, which is especially interesting in the context of engine downsizing from four to three or six to four cylinders.

In order to investigate the soot formation process in a diesel spray flame, simultaneous imaging of soot precursor and soot particles in a transient spray flame achieved in a rapid compression machine was conducted by laser-induced fluorescence (LIF) and by laser-induced incandescence (LII) techniques. The 3rd harmonic (355nm) and the fundamental (1064nm) laser pulses from an Nd:YAG laser, between which a delay of 44ns was imposed by 13.3m of optical path difference, were used to excite LIF from soot precursor and LII from soot particles in the spray flame. The LIF and the LII were separately imaged by two image-intensified CCD cameras with identical detection wavelength of 400nm and bandwidth of 80nm. The LIF from soot precursor was mainly located in the central region of the spray flame between 40 and 55mm (270 to 370 times nozzle orifice diameter d0) from the nozzle orifice. The LII from soot particles was observed to surround the soot precursor LIF region and to extend downstream.

The two-dimensional distribution of a soot cloud in an unsteady spray flame in a rapid compression machine(RCM) was visualized using the laser sheet scattering technique. A 40 mm x 50 mm cross section on the flame axis was illuminated by a thin laser sheet from a single pulsed Nd:YAG laser(wavelength 532 nm). Scattered light from soot particles was taken by a CCD camera via a high speed gated image intensifier. The temporal variation of the scattered light images were presented with the injection pressure as a parameter. The results showed that scattered light was intense near the periphery of the flame tip and that the scattered light becomes weaker significantly and disappears fast after the end of injection as injection pressure is increased. This technique was also applied to the visualization of the two-dimensional distribution of liquid droplets in the non-evaporating spray to correlate it with the soot concentration distribution.

A sheet of laser light from a frequency-doubled Nd-YAG laser (λ = 532 nm) approximately 150 μm thick is shone through the cylinder of a single cylinder internal combustion engine. The light scattered by the fuel spray is collected through a quartz window in the cylinder and is imaged on a 100 × 100 diode array camera. The signal from the diode array is then sent to a microcomputer for background subtraction and image enhancement. The laser pulse is synchronized with the crank shaft of the engine so that a picture of the spray distribution within the engine at different times during injection and the penetration and development of the spray may be observed. The extent of the spray at different positions within the chamber is determined by varying the position and angle of the laser sheet with respect to the piston and the injector.

Two dimensional visualization of a pulsating, hollow-cone spray was performed in a motored, ported, high swirl, cup-in-head I.C. engine, using exciplex-forming dopants in the fuel, which produced spectrally separated fluorescence from the liquid and vapor phases. Illumination was by a laser sheet approximately 200 µm thick from a frequency tripled Nd:YAG laser, and image acquisition was by a 100 × 100 pixel diode array camera interfaced to a personal computer. Liquid and vapor phase fuel distributions are reported for engine speeds of 800 rpm and 1600 rpm, over a crankangle range spanning the injection event and subsequent evaporation and mixing. The beginning of injection was at 33° BTDC at 800 rpm and 47° BTDC at 1600 rpm. At 800 rpm, the spray angle is narrower than the 60° poppet angle, as expected from previous observations in a near-quiescent spray chamber.

A sheet of laser light from a frequency tripled Nd-YAG laser approximately 200μm thick is shone through the combustion chamber of a single cylinder, direct injection internal combustion engine. The injected decane contains exciplex—forming dopants which produce spectrally separated fluorescence from the liquid and vapor phases. The fluorescence signal is collected through a quartz window in the cylinder head and is imaged onto a diode array camera. The camera is interfaced to a microcomputer for data acquisition and processing. The laser and camera are synchronized with the crankshaft of the engine so that 2—D images of the liquid and vapor phase fuel distributions can be obtained at different times during the engine cycle. Results are presented at 600, 1200 and 1800 rpm, and from the beginning to just after the end of injection. The liquid fuel traverses the cylinder in a straight line in the form of a narrow cone, but does not reach the far wall in the plane of the laser sheet.

This paper documents a joint development process between General Motors and Dow Automotive to improve primary body structure frequencies on the GM family of midsize vans by utilizing cavity-filling structural foam. Optimum foam locations, foam quantity, and foam density within the body structure were determined by employing both math-based modeling and vehicle hardware testing techniques. Finite element analysis (FEA) simulations of the Body-In-White (BIW) and “trimmed body” were used to predict the global body structure modes and associated resonant frequencies with and without structural foam. The objective of the FEA activity was to quantify frequency improvements to the primary body structure modes of matchboxing, bending, and torsion when using structural foam. Comprehensive hardware testing on the vehicle was also executed to validate the frequency improvements observed in the FEA results.

In October 1999, General Motors contracted Dana Corporation to manufacture an all-aluminum spaceframe for the 2006 Chevrolet Corvette Z06. Corvette introduced its first ever all-aluminum frame (see Figure 1) to the world at the 2005 North American International Auto Show (NAIAS) in Detroit, Michigan. The creation of this spaceframe resulted in a significant mass reduction and was a key enabler for the program to achieve the vehicle level performance results required for a Z06 in an ever-growing market. Dana Corporation leveraged ALCOA's (Aluminum Company of America) proven design capabilities while incorporating new MIG welding, laser welding, Self-Pierce Riveting (SPR), and full spaceframe machining to join General Motors (GM) Metal Fabrication Division's (MFD) hydroformed rails to produce the Corvette Z06's yearly requirement of 7000 units. This paper describes the technologies utilized throughout the assembly line and their effect on the end product.

The distribution of spray droplet sizes plays a pivotal role in internal combustion engines, directly affecting fuel-air mixing, evaporation, and combustion. To gain a precise understanding of droplet size distribution in a two-dimensional space, non-intrusive optical diagnostics emerge as a highly effective method. In the current investigation, two-dimensional (2D) diesel spray droplet sizes mapping using a simultaneous combination of planar laser-induced fluorescence (PLIF) and Mie-scattering techniques is introduced. The assessment of droplet diameter relies on the interplay between fluorescent and scattered light intensities which correspond the light based on volumetric droplets and surface area of the droplets. This calculation is made possible through the LIF/Mie technique. However, traditional LIF/Mie methods are plagued by inaccuracies arising from multiple light scattering.

The optimization of the vaporization and mixture formation process is of great importance for the development of modern gasoline direct injection (GDI) engines, because it influences the subsequent processes of the ignition, combustion and pollutant formation significantly. In consequence, the subject of this work was the development of a measurement technique based on the laser induced exciplex fluorescence (LIF), which allows the two dimensional visualization and quantification of the in-cylinder air/fuel ratio. A tracer concept consisting of benzene and triethylamine dissolved in a non-fluorescent base fuel has been used. The calibration of the equivalence ratio proportional LIF-signal was performed directly inside the engine, at a well known mixture composition, immediately before the direct injection measurements were started.

The spatial distribution of internal exhaust gas recirculation (EGR) is evaluated in an optically accessible direct injection spark ignition engine using near infrared laser absorption to visualize the distribution of the H2O molecule. The obtained overall internal exhaust gas recirculation compares well to gas-exchange cycle calculations and the spatial distributions are consistent with those measured with inverse LIF. The experimental procedures described in this report are designed to be simple and rapidly implemented without the need to resort to unusual optical components. The necessary spectral data of the selected absorption line is obtained from the HITEMP database and is validated with prior experiments carried out in a reference cell. Laser speckle in the images is effectively reduced using a ballistic diffuser.

In-cylinder flows in a motored four-valve SI engine were examined by simultaneous three-component LDV measurement. The purpose of this study was to develop better physical understanding of in-cylinder flows and quantitative methods which correlate in-cylinder flows to engine performance. This study is believed to be the first simultaneous three-component LDV measurement of the air flow over a planar section of a four-valve piston-cylinder assembly. Special attention is paid to the tumble formation process, three-dimensional turbulent kinetic energy, and measurement of the tumble ratio. The influence of the induction system and the piston geometry are believed to have a significant effect on the in-cylinder flow characteristics. Using LDV measurement, the flows in two different piston top geometries were examined. One axial plane was selected to observe the effect of piston top geometries on the flow field in the combustion chamber.

The Urea Selective Catalytic Reduction (SCR) technology is one of the major mature exhaust aftertreatment technologies which are demonstrated to be able to lower tail pipe NOx emission by 90%. The system consists of a urea injection at upstream pipe and a downstream SCR converter. A well mixed flow (exhaust gas and NH3) in front of SCR substrate, which is usually constrained by tight design packaging, is very critical to ensure the desired performance. Current paper addresses the geometrical effects on flow mixing by using three dimensional Computational Fluid Dynamics (CFD) tool. The mixing enhancement is achieved by adding flow mixer. The shapes and locations of flow mixers, as well as the number of blades inside mixer are investigated to show the effect on fluid mixing in downstream along the flow direction. Results show great improvement of flow mixing by adding a delta wing mixer.

Three-dimensional behaviors of direct injection (D.I.) gasoline sprays were investigated using 2-D and 3-D particle image velocimetry (PIV) techniques. The fuel was injected with a swirl type injector for D.I. gasoline engines into a constant volume chamber in which ambient pressure was varied from 0.1 to 0.4 MPa at room temperature. The spray was illuminated by a laser light sheet generated by a double-pulsed Nd:YAG laser (wave length: 532 nm) and the succeeding two tomograms of the spray were taken by a high-resolution CCD camera. The 2-D and 3-D velocity distributions of the droplet cloud in the spray were calculated from these tomograms by using the PIV technique. The effects of the swirl groove flows in the injector and the ambient pressure on the structural behavior of the droplet cloud in the spray were also examined.

A compound-laser welding method has been developed for the rapid three-dimensional welding of motorcycle aluminum-alloy structural parts. The term “compound-laser welding” means a high-speed welding method in which a number of lasers with different characteristics are arranged on the same axis. This paper reports the results of welding by a compound laser consisting of a YAG laser and a CO2 laser. It was found that compound-laser welding with two or more types of gases mixed as shielding gas gives a better welding performance than single-laser welding due to the advantages of the different lasers used in compound-laser welding.

In recent years, engine manufacturers have been continuously involved in the research of proper technical solutions to meet more and more stringent CO2 emission targets, defined by international regulations. Many strategies have been already developed, or are currently under study, to attain the above objective. A tendency is however emerging towards more innovative combustion concepts, able to efficiently burn lean or highly diluted mixtures. To this aim, the enhancement of turbulence intensity inside the combustion chamber has a significant importance, contributing to improve the burning rate, to increase the thermal efficiency, and to reduce the cyclic variability. It is well-known that turbulence production is mainly achieved during the intake stroke. Moreover, it is strictly affected by the intake port geometry and orientation.

In scooter/motorbike engines coherent and stable tumble motion generation is still considered an effective mean in order to both reduce engine emissions and promote higher levels of combustion efficiency. The scientific research also assessed that squish motion is an effective mean for speeding up the combustion in a combustion process already fast. In a previous technical paper the authors demonstrated that for an engine having a high C/D ratio the squish motion is not only not necessary but also detrimental for the stability of the tumble motion itself, because there is a strong interaction between these two motions with the consequent formation of secondary vortices, which in turn penalizes the tumble breakdown and the turbulent kinetic energy production.

In this paper three-dimensional Large Eddy Simulations (i.e., LES) by using a PLIC-VOF method have been adopted to investigate the atomization process of round liquid jets issuing from automotive multi-hole injector-like nozzles. LES method is used to compute directly the effect of the large flow structure, being the smallest one modelled. A mesh having a cell size of 4 μm was used in order to derive a statistics of the detached liquid structures, i.e. droplets and ligaments. The latter have been identified by using an algorithm coded by authors. Cavitation modeling has not been included in the present computations. Two different mean injection nozzle flow velocities of 50 m/s and 270 m/s, corresponding to two mean nozzle flow Reynolds numbers of 1600 and 8700, respectively, have been considered in the calculations as representative of laminar and turbulent nozzle flow conditions.

Steady induction port flow has been simulated in a complex configuration, which is modelled on a four-valve engine with a pent-roof chamber. The numerical solution has been obtained using a finite volume method coupled with the standard k - ε turbulence model. It is shown that the 3D flow field is characterised by large vortices with horizontal axes induced by the inlet jets, and by flow interaction between inlet jets from both valves. Special attention has been paid to flow distributions in the valve curtain areas. Velocity and turbulence energy profiles have been obtained in these areas and compared with previous hot-wire measurements and 2D calculations using Reynolds stress models as well as the k - ε model. The findings in this study are expected to enhance our understanding of complex engine induction port flows and to provide better boundary conditions for in-cylinder flow calculations

The quality of mixture formation in gasoline direct injection (GDI) engines has a significant influence on combustion, emissions and mileage. A new measurement technique was set up at an optically accessible high pressure / high temperature spray chamber to investigate the spatial mass distribution of vapor and liquid phase in order to optimize the stratified engine operation mode. Therefore a laser light sheet is traversed through the spray, the exciplex fluorescence is detected and the tomography results are quantified by the global information of the injected mass, which allows detailed spray investigations with λ-charts. For spray homogeneity analysis a new method based on histogram calculation is presented allowing grid independent comparison of different injector types.