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Cooling Airflow System Modeling in CFD Using Assumption of Stationary Flow

2011-11-29
Today CFD is an important tool for engineers in the automotive industry who model and simulate fluid flow. For the complex field of Underhood Thermal Management, CFD has become a very important tool to engineer the cooling airflow process in the engine bay of vehicles. Presenter Peter Gullberg, Chalmers University of Technology
Technical Paper

A Catalytic NOX After-Treatment System for Heavy-Duty Trucks Using Diesel Fuel as Reducing Agent

1999-10-25
1999-01-3563
An advanced catalytic exhaust after-treatment system addresses the problem of NOX emissions from heavy-duty diesel trucks, relying on real-time catalyst modelling. The system consists of de-NOX catalysts, a device for injection of a reducing agent (diesel fuel) upstream the catalysts, and computer programmes to control the injection of the reducing agent and to model the engine and catalysts in real time. Experiments with 5 different air-assisted injectors were performed to determine the effect of injector design on the distribution of the injected diesel in the exhaust gas stream. A two-injector set-up was investigated to determine whether system efficiency could be increased without increasing the amount of catalyst or the amount of reducing agent necessary for the desired outcome. The results were verified by performing European standard transient cycle tests as well as stationary tests.
Technical Paper

Sulphur Poisoning and Regeneration of NOx Trap Catalyst for Direct Injected Gasoline Engines

1999-10-25
1999-01-3504
Sulphur poisoning and regeneration of NOx trap catalysts have been studied in synthetic exhausts and in an engine bench. Sulphur gradually poisoned the NOx storage sites in the axial direction of the NOx trap. During sulphur regenerations, hydrogen was found to be more efficient than carbon monoxide in removing the sulphur from the trap. The sulphur regeneration became more efficient the richer the environment (λ<1) and the higher the temperature (at least 600°C). H2S was found to be the main product during the sulphur regeneration. However, it was possible to reduce the H2S formation and instead produce more SO2 by running with lambda close to one or by pulsing lambda. Even if a relatively large amount of sulphur was removed from the NOx trap, these methods gave a much less efficient regeneration per sulphur atom removed than when running relatively rich constantly. Finally, a model that could explain this observation was proposed.
Technical Paper

Injection Orifice Shape: Effects on Spray Characteristics and Heat-Release Rate in a Large-Size Single-Cylinder Diesel Engine

1999-10-25
1999-01-3490
A series of experimental studies of diesel spray and combustion characteristics was carried out using circular, elliptic and step orifices. The experiment was performed on a 3-litre single-cylinder engine with optical access. In the engine tests, an elliptic-orifice nozzle with an aspect ratio of approximately 2:1, and a step-orifice nozzle were compared with circular-orifice nozzles. All orifices had sharp-edged inlets. The nozzles were tested at injection pressures extending from 300 to 1300 bar. The nozzles were evaluated in respect of initial spray tip velocity, penetration, spray cone angle, spray width, intermittency and heat-release. Substantial differences were observed in the spray characteristics: At an injection pressure of 300 bar, the spray width increased twice as fast in the minor axis plane of the elliptic orifice and step orifice than the circular orifices.
Technical Paper

ANNIE, a Tool for Integrating Ergonomics in the Design of Car Interiors

1999-09-28
1999-01-3372
In the ANNIE project - Applications of Neural Networks to Integrated Ergonomics - BE96-3433, a tool for integrating ergonomics into the design process is developed. This paper presents some features in the current ANNIE as applied to the design of car interiors. A variant of the ERGOMan mannequin with vision is controlled by a hybrid system for neuro-fuzzy simulation. It is trained by using an Elite system for registration of movements. An example of a trajectory generated by the system is shown. A fuzzy model is used for comfort evaluation. An experiment was performed to test its feasibility and it showed very promising results.
Technical Paper

Analysis of Brake Judder by use of Amplitude Functions

1999-05-17
1999-01-1779
Brake judder is a forced vibration occurring in different types of vehicles. The frequency of the vibration can be as high as 500 Hz, but usually remains below 100 Hz and often as low as 10-20 Hz. The driver experiences judder as vibrations in the steering wheel, brake pedal and floor. For high frequency brake judder, the structural vibrations are accompanied by a sound. In the present paper the vibration amplitude (in terms of angular deflection, velocity or acceleration) of the caliper has been used as a quantitative measure of the vibration level. Brake Torque Variation (BTV) is the primary excitation for the vibrations. The mechanical effects generating BTV are linked not only to manufacturing tolerances but also to tribological issues. Uneven disc wear as well as Thermo-Elastic Instabilities (TEI) can lead to judder. Especially the effect of the wheel suspension on the transfer of the vibrations to the driver has to be considered.
Technical Paper

3-D Diesel Spray Simulations Using a New Detailed Chemistry Turbulent Combustion Model

2000-06-19
2000-01-1891
Until recently, the application of the detailed chemistry approach as a predictive tool for engine modeling has been sort of a “taboo” for different reasons, mainly because of an exaggerated rigor to the chemistry/turbulence interaction modeling. In terms of this ideology, if the interaction cannot be simulated properly, the detailed chemistry approach makes no sense. The novelty of the proposed methodology is the coupling of a generalized partially stirred reactor, PaSR, model with the high efficiency numerics to treat detailed oxidation kinetics of hydrocarbon fuels. In terms of this approach, chemical processes are assumed to proceed in two successive steps: the reaction follows after the micro-mixing is completed on a sub-grid scale.
Technical Paper

Performance and Emission Analysis of a Non-Conventional Gasoline Engine

2000-06-19
2000-01-1840
A new engine design concept, characterized by a single cylinder-double piston and a cycloid crank rotor instead of the conventional crankshaft has been developed recently by Gul & Co Development AB, Sweden. The rotor (crank disc) is equipped with an oval groove in the shape of a sinusoidal cycloid according to the expression varies from 0 to 1. Inside the oval groove a ball rolls/slides in order to transfer force from the piston to the rotor. Such a rotor contains groove surfaces for the valve movement control as well. Each turn of the rotor corresponds to four strokes for both the pistons. Thus, a full 4-stroke engine cycle is developed for a single non-conventional crankshaft revolution. Having the extra freedom to select an optimal piston movement, the new design is believed to have the potential to provide low emissions, low noise levels and lower fuel consumption. Therefore, it has been subjected to an engine thermodynamics simulation, to provide an insight to engine performance.
Technical Paper

Proactive Human Factors Engineering Analysis in Space Station Design Using the Computer Manikin Jack

2000-06-06
2000-01-2166
In this case study, a human factors analysis was carried out in the preliminary design phase of the Cupola, a European Space Agency (ESA) module for manned space flights for the International Space Station (ISS). The manikin software Jack® was used early in the design process before any flight hardware production. All Cupola astronaut tasks were evaluated in a virtual environment of the Cupola. Methodological aspects concerning the analysis are described, e.g. file processing, use of coordinate systems and the use of a prior task analysis. Results show that the thorough manikin analysis supported with the hierarchical task analysis results, was an important help in the design process.
Technical Paper

The Effect of Elliptical Nozzle Holes on Combustion and Emission Formation in a Heavy Duty Diesel Engine

2000-03-06
2000-01-1251
A serie of experiments were carried out to compare the combustion and emissions characteristics of a diesel engine using non-circular (elliptical) and circular shaped fuel injector nozzle holes. Elliptic nozzle holes have the potential to increase air entrainment into the spray, which could lead to decreased emissions from diesel combustion. Previous work [6,7] has shown some interesting results in a passenger car diesel engine and also in a single cylinder engine with optical access. The idea is based on results from investigations of gas jets, where the air entrainment for elliptical jets was increased substantially compared to circular jets. The present series of experiments were carried out to further investigate these effects. The non-circular holes, which were made with an aspect ratio of close to 2:1, have a similar flow rate as the conventional circular holes. Two different angles of the elliptical major axis to the injector centerline were used.
Technical Paper

On CFD and Transient Flow in Vehicle Aerodynamics

2000-03-06
2000-01-0873
The accuracy of computational fluid dynamics, CFD, has improved considerably over the years but still, large errors are present and vehicle parameters such as drag and lift are often poorly predicted. The current work is investigating how transient CFD would cope with a very complex flow structure around a surface mounted cube. A transient Reynolds averaged Navier Stokes model, RANS model, is presented together with a large eddy simulation model, LES model. Furthermore, two “industrial like” test cases have been simulated using a transient RANS model.
Technical Paper

Use of Repeated Crash-Tests to Determine Local Longitudinal and Shear Stiffness of the Vehicle Front with Crush

1999-03-01
1999-01-0637
Crash-test-data on local longitudinal and shear stiffness of the vehicle front is needed to estimate impact severity from car deformation in offset or pole impacts, and to predict vehicle acceleration and compartment intrusion in car-to-car crashes. Repeated full frontal crash-tests were carried out with a load-cell barrier to determine the local longitudinal stiffness with increasing crush. Repeated off-set tests were run to determine shear stiffness. Two single high-speed tests (full frontal and offset) were carried out and compared to the repeated tests to determine the rate sensitivity of the front structure. Four repetitions at 33.4 km/h provided equivalent energy absorption to a single 66.7 km/h test, when rebound was considered. Power-train inertial effects were estimated from highspeed tests with and without power-train. Speed effects averaged 2% per [m/s] for crush up to power-train impact, and post-crash measurements were a reasonable estimate of front-structure stiffness.
Technical Paper

Flow Visualization Study of an HVAC Module Operated in Water

2001-05-14
2001-01-1702
Centrifugal blowers serve as the primary source of airflow and aero-acoustic noise in automotive HVAC modules. Flow field measurements inside blowers indicate very complex flow patterns. A detailed flow visualization study was conducted on an actual HVAC fan module operated in water under dynamically similar conditions as those in air with the purpose of studying the complex flow patterns in order to improve the aerodynamic performance of the fan/scroll casing and diffuser components. Fan-scroll/diffuser interaction was also studied as function of fan speed. Conventional and special (shear thickening) dye injection flow visualization techniques were used to study the complex 3-dimensional vortical and unsteady flow patterns that occur in typical HVAC fans. A major advantage of the flow visualization technique using shear-thickening dye is its usefulness in high the Reynolds number flows that are typically encountered inside HVAC modules.
Technical Paper

Misfire Detection for Prechamber SI Engines Using Ion-Sensing and Rotational Speed Measurements

2001-03-05
2001-01-0993
A misfire detection study on a prechamber equipped spark ignition gas combustion engine is presented. The study shows that the logarithm of the absolute valued ion current can be linearly weighted in order to detect misfire over a broad load range with only one threshold. Results also show that a very low complexity misfire detector can achieve good performance when a linear weighting technique is applied to the squared rotational speed samples. The detection performance based on the combination of rotational speed and ionization measurements is also presented.
Technical Paper

The Structure of Cavitation and its Effect on the Spray Pattern in a Single-Hole Diesel Nozzle

2001-05-07
2001-01-2008
The structure and evolution of cavitation in a transparent scaled-up diesel nozzle having a hole perpendicular to the nozzle axis has been investigated using high-speed motion pictures, flash photography and stroboscopic visualization. Observations revealed that, at the inception stage, cavitation bubbles are dominantly seen in the vortices at the boundary layer shear flow and outside the separation zone. Cavitation bubbles grow intensively in the shear layer and develop into cloud-like coherent structures when viewed from the side of the nozzle. Shedding of the coherent cloud cavitation was observed. When the flow was increased further the cloud like cavitation bubbles developed into a large-scale coherent structure extending downstream of the hole. Under this condition the cavitation starts as a mainly glassy sheet at the entrance of the hole. Until this stage the spray appeared to be symmetric.
Technical Paper

Diesel Combustion with Reduced Nozzle Orifice Diameter

2001-05-07
2001-01-2010
Future emission legislation will require substantial reductions of NOx and particulate matter (PM) emissions from diesel engines. The combustion and emission formation in a diesel engine is governed mainly by spray formation and mixing. Important parameters governing these are droplet size, distribution, concentration and injection velocity. Smaller orifices are believed to give smaller droplet size, even with reduced injection pressure, which leads to better fuel atomization, faster evaporation and better mixing. In this paper experiments are performed on a single cylinder heavy-duty direct injection diesel engine with three nozzles of different orifice diameters (Ø0.227 mm, Ø0.130 mm, Ø0.090 mm). Two loads (low and medium) and three speeds were investigated. The test results confirmed a substantial reduction in HC and soot emissions at lower loads for the small orifices.
Technical Paper

A Four Stroke Camless Engine, Operated in Homogeneous Charge Compression Ignition Mode with Commercial Gasoline

2001-09-24
2001-01-3610
A single cylinder, naturally aspirated, four-stroke and camless (Otto) engine was operated in homogeneous charge compression ignition (HCCI) mode with commercial gasoline. The valve timing could be adjusted during engine operation, which made it possible to optimize the HCCI engine operation for different speed and load points in the part-load regime of a 5-cylinder 2.4 liter engine. Several tests were made with differing combinations of speed and load conditions, while varying the valve timing and the inlet manifold air pressure. Starting with conventional SI combustion, the negative valve overlap was increased until HCCI combustion was obtained. Then the influences of the equivalence ratio and the exhaust valve opening were investigated. With the engine operating on HCCI combustion, unthrottled and without preheating, the exhaust valve opening, the exhaust valve closing and the intake valve closing were optimized next.
Technical Paper

Gasoline HCCI Modeling: Computer Program Combining Detailed Chemistry and Gas Exchange Processes

2001-09-24
2001-01-3614
A skeletal reaction mechanism (101 species, 479 reactions) for a range of aliphatic hydrocarbons was constructed for application to computational fluid dynamics (CFD) Gasoline Homogeneous Charge Compression Ignition (HCCI) engine modeling. The mechanism is able to predict shock tube ignition delays and premixed flame propagation velocities for the following components: hydrogen (H2), methane (CH4), acetylene (C2H2), propane (C3H8), n-heptane (C7H16) and iso-octane (C8H18). The mechanism is integrated with a simulation code combining both modeling of detailed chemistry and gas exchange processes. This simulation tool was constructed by connecting the SENKIN code of the CHEMKIN library to the AVL BOOST™ engine cycle simulation code. Using a complete engine cycle simulation code instead of a code that only considers the combustion process has a major advantage. The initial conditions at the intake valve closure (IVC) have no longer to be set.
Technical Paper

Prerequisites for Extensive Computer Manikin Analysis – An Example with Hierarchical Task Analysis, File Exchange Protocol and a Relational Database

2001-06-26
2001-01-2101
In this case study, a human factors engineering (HFE) analysis was carried out in the preliminary design phase of the Cupola. Cupola is a European Space Agency (ESA) module for manned space flights for the International Space Station (ISS) as part of a Barter Arrangement between ESA and the United States National Aeronautics and Space Administration (NASA). Manikin software was used early in the design process before the production of any flight hardware. The manikin analysis was supported by the use of hierarchical task analysis, a file exchange protocol and a relational database. This paper describes methodological aspects of the use of the supporting methods. Results show that hierarchical task analysis, a file exchange protocol and a relational database are prerequisites for successful extensive manikin analysis.
Technical Paper

Large-Eddy Simulation of the Flow Around a Ground Vehicle Body

2001-03-05
2001-01-0702
Large Eddy Simulation of the the flow around bus-like ground vehicle body is presented. Both the time-averaged and instantaneous aspects of this flow are studied. Time-averaged velocity profiles are computed and compared with the experiments [1] and show good agreement. The separation length and the base pressure coefficient are presented. The predicted pumping process in the near wake occurs with a Strouhal number St = 0.073, compared with St = 0.069 in the experiment. Unsteady results at two points are presented and compared with the experiments. The coherent structures are studied and show good agreement with the experiments.
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