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Technical Paper

0D/3D Simulations of Combustion in Gasoline Engines Operated with Multiple Spark Plug Technology

2015-04-14
2015-01-1243
A simulation method is presented for the analysis of combustion in spark ignition (SI) engines operated at elevated exhaust gas recirculation (EGR) level and employing multiple spark plug technology. The modeling is based on a zero-dimensional (0D) stochastic reactor model for SI engines (SI-SRM). The model is built on a probability density function (PDF) approach for turbulent reactive flows that enables for detailed chemistry consideration. Calculations were carried out for one, two, and three spark plugs. Capability of the SI-SRM to simulate engines with multiple spark plug (multiple ignitions) systems has been verified by comparison to the results from a three-dimensional (3D) computational fluid dynamics (CFD) model. Numerical simulations were carried for part load operating points with 12.5%, 20%, and 25% of EGR. At high load, the engine was operated at knock limit with 0%, and 20% of EGR and different inlet valve closure timing.
Technical Paper

Physical Modeling of Automotive Turbocharger Compressor: Analytical Approach and Validation

2011-09-13
2011-01-2214
Global warming is a climate phenomenon with world-wide ecological, economic and social impact which calls for strong measures in reducing automotive fuel consumption and thus CO2 emissions. In this regard, turbocharging and the associated designing of the air path of the engine are key technologies in elaborating more efficient and downsized engines. Engine performance simulation or development, parameterization and testing of model-based air path control strategies require adequate performance maps characterizing the working behavior of turbochargers. The working behavior is typically identified on test rig which is expensive in terms of costs and time required. Hence, the objective of the research project “virtual Exhaust Gas Turbocharger” (vEGTC) is an alternative approach which considers a physical modeled vEGTC to allow a founded prediction of efficiency, pressure rise as well as pressure losses of an arbitrary turbocharger with known geometry.
Technical Paper

Gasoline HCCI/CAI on a Four-Cylinder Test Bench and Vehicle Engine - Results and Conclusions for the Next Investigation Steps

2010-05-05
2010-01-1488
Internal combustion engines with lean homogeneous charge and auto-ignition combustion of gasoline fuels have the capability to significantly reduce fuel consumption and realize ultra-low engine-out NOx emissions. Group research of Volkswagen AG has therefore defined the Gasoline Compression Ignition combustion (GCI®) concept. A detailed investigation of this novel combustion process has been carried out on test bench engines and test vehicles by group research of Volkswagen AG and IAV GmbH Gifhorn. Experimental results confirm the theoretically expected potential for improved efficiency and emissions behavior. Volkswagen AG and IAV GmbH will utilize a highly flexible externally supercharged variable valve train (VVT) engine for future investigations to extend the understanding of gas exchange and EGR strategy as well as the boost demands of gasoline auto-ignition combustion processes.
Technical Paper

In-cylinder Flow Field Measurement with Doppler Global Velocimetry in Combination with Droplet Distribution Visualization by Mie Scattering

2009-04-20
2009-01-0652
Flow fields and fuel distribution play a critical role in developing the combustion process inside the cylinders of piston engines. This has prompted the development of measurement and diagnostic capabilities including laser techniques like Doppler Global Velocimetry (DGV). The paper provides an overview of the basics of DGV and the type of results that can be obtained. It also includes a short comparison to Particle Image Velocimetry (PIV) which is a popular alternative method. Furthermore, it is shown that DGV can be used simultaneously in combination with droplet distribution visualization inside cylinders based on Mie scattering.
Technical Paper

Advanced Turbocharger Model for 1D ICE Simulation - Part I

2013-04-08
2013-01-0581
Standard compressor and turbine maps obtained from steady-state test bench measurements are not sufficient for assessing transient turbocharger behavior. This also makes them inappropriate for gauging combustion-engine response and fuel consumption. Nor do they allow for the widely differing operating conditions which, apart from aerodynamics, have a major influence on heat transfer and turbocharger efficiency. This paper looks at a more complex approach of modeling the turbocharger as well developing appropriate measurement methods (“advanced turbocharger model”). This includes non-destructive measurements under various heat transfer conditions to define the turbocharger's adiabatic behavior needed to describe charge-air pressure increase in the compressor and engine exhaust gas backpressure from the turbine for transient engine operation.
Technical Paper

Investigations on the Potential of a Variable Miller Cycle for SI Knock Control

2013-04-08
2013-01-1122
A promising combustion technology for DISI downsizing engines is the Miller cycle. It is based on an early intake valve closing for the separation of effective and geometric compression ratio. Therefore IAV has prepared a turbocharged DISI test engine with a high geometric compression ratio. This engine is equipped with the Schaeffler “UniAir” variable valve train in order to investigate a variable Miller cycle valve timing in the turbocharged map area. The goal is to investigate whether and how a rapidly variable Miller cycle can influence the knocking behavior. Therefore its potential for a SI knock control can be evaluated. The investigated parameters in a steady-state engine dyno mode were the intake valve closing timing, the intake camshaft phasing and the ignition timing. A variable intake valve closing Miller cycle strategy, a variable intake camshaft phasing Miller cycle strategy and a state-of-the- art ignition timing strategy have been investigated.
Technical Paper

Cold Start Simulation and Test on DISI Engines Utilizing a Multi-Zone Vaporization Approach

2012-04-16
2012-01-0402
Recent years have witnessed a dramatic increase in global ethanol production, while cellulosic feedstock or the algae-based production approach make more sustainable ethanol production foreseeable in many countries. The ethanol produced will increasingly penetrate the markets not only as blending component, but also as main fuel component, boosting demand for flex-fuel vehicles. One of the main challenges for flex-fuel vehicles is the cold start due to the poor vapor pressure of ethanol. This is detrimental to starting capability in DISI engines in particular, with increased cylinder wall wetting causing higher oil dilution. The most efficient solution for DISI engines is a smart injection strategy, enabling fuel vaporization during injection in the compression stroke. But this requires optimum injection parameters such as injection timing, split ratio and rail pressure.
Technical Paper

A Simulation-Based Comparison of Different Power Split Configurations with Respect to the System Efficiency

2012-04-16
2012-01-0438
In power-split configuration, the input power is split into two parts, one of which is transmitted from the internal combustion engine through one or more planetary gear(s) to the wheels. The other part is generated as electricity and passes through an electrical variator to assist the driving torque. The latter has the characteristic of poor efficiency. In this simulation study, a comparison among the input power-split, compound power-split, and two mode power-split are discussed. Output power-split is not mentioned in this paper due to its limited applicability in specific vehicles. The idea of selection of the electrical machines is explained: the speed and torque of electrical machines was taken into consideration for the required transmission ratios spread.
Technical Paper

Model-Based Assessment of Hybrid Powertrain Solutions

2011-09-11
2011-24-0070
This paper shows the main results of a research activity carried out in order to investigate the impact of different hybridization concepts on vehicle fuel economy during standard homologation cycles (NEDC, FTP75, US Highway, Artemis). Comparative analysis between a standard passenger vehicle and three different hybrid solutions based on the same vehicle platform is presented. The following parallel hybrid powertrain solutions were investigated: Hybrid Electric Vehicle (HEV) solution (three different levels of hybridization are investigated with respect to different Electric Motor Generator size and battery storage/power capacity), High Speed Flywheel (HSF) system described as a fully integrated mechanical (kinetic) hybrid solution based on the quite innovative approach, and hydraulic hybrid system (HHV). In order to perform a fare analysis between different hybrid systems, analysis is also carried out for equal system storage capacities.
Technical Paper

Comparison and Evaluation of a New Innovative Drive Concept for the Air Conditioning Compressor of Electric Vehicles

2015-01-14
2015-26-0045
The development of energy efficient air conditioning systems for electric vehicles is an ever increasing challenge, because the cooling as well as the heating of the passenger compartment reduces the cruising range dramatically. Electric cars are usually equipped with a scroll compressor and a separate electric motor with appropriate power electronics. However, this solution is critical in terms of the installation space, the weight and also the costs. Therefore, an innovative and energy efficient drivetrain structure for electric vehicles was developed, which integrates the motor of the A/C-compressor directly into the drivetrain. Thus it is possible to switch off the compressor motor and to use the main motor for the drive of the compressor at certain driving situations. As a result, the operating point of the main motor can be shifted to a better efficiency.
Technical Paper

Modeling and Identification of a Gasoline Common Rail Injection System

2014-04-01
2014-01-0196
The precision of direct fuel injection systems of combustion engines is crucial for the further reduction of emissions and fuel consumption. It is influenced by the dynamic behavior of the fuel system, in particular the injection valves and the common rail pressure. As model based control strategies for the fuel system could substantially improve the dynamic behavior, an accurate model of the common rail injection system for gasoline engines - consisting of the main components high-pressure pump, common rail and injection valves - that could be used for control design is highly desirable. Approaches for developing such a model are presented in this paper. For each key component, two models are derived, which differ in temporal resolution and number of degrees of freedom. Experimental data is used to validate and compare the models. The data was generated on a test bench specifically designed and built for this purpose.
Technical Paper

Model Based Exhaust Aftertreatment System Integration for the Development and Calibration of Ultra-Low Emission Concepts

2014-04-01
2014-01-1554
The development and calibration of exhaust aftertreatment (EAT) systems for the most diverse applications of diesel powertrain concepts requires EAT models, capable of performing concept analysis as well as control and OBD system development and calibration. On the concept side, the choice of an application-specific EAT layout from a wide technology selection is driven by a number of requirements and constraints. These include statutory requirements regarding emissions of criteria pollutants and greenhouse gases (GHG), technical constraints such as engine-out emissions and packaging, as well as economic parameters such as fuel consumption, and EAT system and system development costs. Fast and efficient execution of the analysis and multi-criteria system optimization can be done by integrating the detailed EAT models into a total system simulation.
Technical Paper

Investigations on Ventilation Strategies for SI Cylinder Deactivation Based on a Variable Valve Train

2016-10-17
2016-01-2346
Advanced SI engines for passenger cars often use the cylinder deactivation technology for dethrottling and thus achieving a reduction of fuel consumption. The gas exchange valves of the deactivated cylinders are closed permanently by a zero lift of the cams. The solutions for cylinder deactivation can vary in the kind of gas composition included in the deactivated cylinders: charge air, exhaust gas or vacuum. All these strategies have in common the frequent loss of captured charge mass from cycle to cycle. Their two-stroke compression-expansion cycle additionally intensifies this phenomenon. Thus, a significant decrease of the minimum cylinder pressure can cause an undesired entry of lubricant into the combustion chamber. The idea was to ventilate the generally deactivated cylinders frequently to compensate the loss of captured cylinder charge mass. The task was to keep the minimum cylinder pressure above a certain limit to prevent the piston rings from a failure.
Technical Paper

Achieving the Max - Potential from a Variable Compression Ratio and Early Intake Valve Closure Strategy by Combination with a Long Stroke Engine Layout

2017-09-04
2017-24-0155
The combination of geometrically variable compression (VCR) and early intake valve closure (EIVC) proved to offer high potential for increasing efficiency of gasoline engines. While early intake valve closure reduces pumping losses, it is detrimental to combustion quality and residual gas tolerance due to a loss of temperature and turbulence. Large geometric compression ratio at part load compensates for the negative temperature effect of EIVC with further improving efficiency. By optimizing the stroke/bore ratio, the reduction in valve cross section at part load can result in greater charge motion and therefore in turbulence. Turbocharging means the basis to enable an increase in stroke/bore ratio, called β in the following, because the drawbacks at full load resulting from smaller valves can be only compensated by additional boosting pressure level.
Technical Paper

Low-Cost Powertrain Platform for HEV and EV

2017-01-10
2017-26-0088
Currently known hybrid systems are technically complex, cost-intensive and referring to this for many end-customers not available. Under this boundaries IAV has developed a cost-optimal concept of an efficient and modular powertrain platform for electric and hybrid vehicles. The system is based on one unity gear-set for up to three speeds, which enables seamless shifting with only one friction based clutch. With this platform powertrains can be realized by using a maximum number of carry over parts (COP) for electric vehicles as well as for hybrids. The derivable hybrid powertrains of the platform system are designed for 48V electric motors (EM) which enables the maximum cost potential in combination with the realized gear set and transmission technology. The real simple powertrain platform concept is furthermore scalable for different vehicle segments optionally with or without a hybrid option.
Technical Paper

Homogeneous Diesel Combustion with External Mixture Formation by a Cool Flame Vaporizer

2006-10-16
2006-01-3323
The homogeneous Diesel combustion is a way to effect a soot and nitrogen oxide (NOx) free Diesel engine operation. Using direct injection of Diesel fuel, the mixture typically ignites before it is fully homogenized. In this study a homogeneous mixture is prepared outside of the combustion chamber by a Cool Flame Vaporizer. At first the specification of the vaporizer is given in this paper. To determine the composition of the vaporizer gas an analysis using gas chromatography/mass spectroscopy (GC/MS) was made. The results give an idea of the effects on engine combustion. Followed by, the vaporizer was adapted to a single-cylinder Diesel engine. To adapt the engine's configuration regarding compression ratio and inlet temperature range a zero dimensional engine process simulation software was utilized. The engine was run in different operating modes.
Technical Paper

Calibration of Torque Structure and Charge Control System for SI Engines Based on Physical Simulation Models

2006-04-03
2006-01-0854
A physics-based simulation program developed by IAV is used to calibrate the torque structure and cylinder charge calculation in the electronic control unit of SI engines. The model calculates both the charge cycle and combustion phase based on flow mechanics and a fractal combustion model. Once the air mass in the charge cycle has been computed, a fractal combustion model is used for the ongoing calculation of cylinder pressure and temperature. The progression of cylinder pressure over the high and low-pressure phases also provides information on engine torque. Following the engine-specific calibration of the model using elemental geometric information and reduced test bench measurements, the physical engine properties can be simulated over the operating cycle. The calibrated model allows simulations to be carried out at all operating points and the results to be treated as virtual test bench measurements.
Technical Paper

Boost and EGR System for the Highly Premixed Diesel Combustion

2006-04-03
2006-01-0204
Advanced Diesel combustion strategies with the focus on the reduction of NOx and PM emission as well as fuel consumption need an increase of the EGR rate and therefore improved boost concepts. The suppression of the nitrogen oxide build up requires changes in the charge condition (charge temperature, EGR rate), which have to be realized by the gas exchange system. The gas exchange system of IAV's ADCS test engine was dimensioned with the help of the engine process simulation software THEMOS®. This paper shows simulation and test bench results of the potential to increase the EGR rate and the charge density at stationary and transient operation. The increase of both EGR rate and boost pressure, as well as the need for a better control of transient operation leads to greater requirements for the engine control system. The potential of the engine and its control system for an application to a demo vehicle will be assessed.
Technical Paper

Effects of Charge Motion Characteristics on Engine Variables such as Emission Behavior and Efficiency

2007-04-16
2007-01-0640
Mixture formation in the combustion chamber is of paramount significance for diesel combustion processes. Particularly in inhomogeneous combustion processes with internal mixture formation, the course of combustion and composition of combustion products are heavily influenced by charge motion and material transport during the compression phase and during combustion itself. Charge motion is normally quantified in steady-state flow testing. This model-based test takes place under idealized conditions. This means that with a permanently open valve and constant pressure differential over the inlet port, a steady-state flow of air is established in the simulated cylinder. The influence of piston movement is neglected. The test delivers integral characteristic flow figures, such as swirl number, flow number and tumble number.
Technical Paper

Air System Control for Advanced Diesel Engines

2007-04-16
2007-01-0970
In order to satisfy environmental regulations while maintaining strong performance and excellent fuel economy, advanced diesel engines are employing sophisticated air breathing systems. These include high pressure and low pressure EGR (Hybrid EGR), intake and exhaust throttling, and variable turbine geometry systems. In order to optimize the performance of these sub-systems, system level controls are necessary. This paper presents the design, benefits and test results of a model-based air system controller applied to an automotive diesel engine.
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