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Technical Paper

3-Dimentional Numerical Transient Simulation and Research on Flow Distribution Unevenness in Intake Manifold for a Turbocharged Diesel Engine

The design of engine intake system affects the intake uniformity of each cylinder of the engine, which in turn has an important impact on the engine performance, the uniform distribution of EGR exhaust gas and the combustion process of each cylinder. In this paper, the constant-pressure supercharged diesel engine intake pipe is used as the research model to study the intake air flow unevenness of the intake pipe of the supercharged diesel engine. The pressure boundary condition at the outlet of each intake manifold is set as the dynamic pressure change condition. The three-dimensional numerical simulation of the transient flow process in the intake manifold of diesel engine is simulated and analyzed by using numerical method, and the change of the Intake air flow field in the intake manifold under different working conditions during the intake overlapping period is discussed.
Technical Paper

34 Experimental Analysis of Piston Slap from Small Two-Stroke Gasoline Engine

This project is an experimental investigation and optimization of piston slap noise in small two-stroke gasoline engine. Piston slap is one of the most significant mechanical noise sources in an internal combustion engine. It is a dynamic impact phenomenon between the piston and the cylinder block caused by changes in the lateral forces acting on the piston. The change in cylinder block vibration level caused by the piston impact is considered as a measure of piston slap during this experiment. The intensity of piston slap is measured in terms of vibration level in ‘g’ units, by means of accelerometers mounted on the cylinder block with Top Dead Center (TDC) and Bottom Dead Center (BDC) marker. For the design of low noise engines, all the major parameters, which contribute to piston slap, are listed and the critical four are examined through additional experiments.
Technical Paper

35 Engine Performance of the Small Compression Ignition Engine with DME Low Pressure Injection

In the research of DME compression ignition engine, there are a lot of reports on the high fuel pressure systems which are used in the common-rail fuel injector and others for the DME mixture formation promotion. However, the initial development-cost of these fuel supply systems will be increased for small compression ignition engines. On the other hand, it has been understood that excellent thermal efficiency of DME compression ignition engine was obtained at the appropriate fuel injection timing by using the electronic controlled injector with low pressure injection. In this paper, the stabilization of combustion on DME compression ignition engine with low pressure injection was investigated for the influence of the fuel pressure and the combustion assistance with homogeneous charge.
Technical Paper

36 Development of a High Performance Small Gas Engine for a Gas Engine Heat Pump

GHP which, is the heat pump system for an air conditioning, is directly driven the compressor by a small gas engine. The NOx was reduced 70% less than a conventional gas engine with improvement of thermal efficiency. The combustion chamber shape using strong squish flow is improved in order that the pattern of a heat release is changed to be suitable. Because the relation between NOx and the thermal efficiency is the trade off relation, the air fuel ratio and the ignition timing must be precisely controlled. Detecting the change of the Pi variation calculated from the engine speed variation can control the air fuel ratio.
Technical Paper

3D Aeroacoustics Simulation of a Complete Bus Exhaust System

Health related problems in over populated areas are a major concern and as such, there are specific legislations for noise generated by transport vehicles. In diesel powered commercial vehicles, the source for noise are mainly related to rolling, transmission, aerodynamics and engine. Considering internal combustion engine, three factors can be highlighted as major noise source: combustion, mechanical and tailpipe. The tailpipe noise is considered as the noise radiated from the open terminations of intake and exhaust systems, caused by both pressure pulses propagating to the open ends of the duct systems, and by vortex shedding as the burst leaves the tailpipe (flow generated noise). In order to reduce noise generated by vehicles, it is important to investigate the gas interactions and what can be improved in exhaust line design during the product development phase.
Technical Paper

3D CFD Analyses of Intake Duct Geometry Impact on Tumble Motion and Turbulence Production in SI Engines

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.
Technical Paper

3D CFD Analysis of the Influence of Some Geometrical Engine Parameters on Small PFI Engine Performances - The Effects on Tumble Motion and Mean Turbulent Intensity Distribution

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.
Technical Paper

3D CFD Modeling of a Biodiesel-Fueled Diesel Engine Based on a Detailed Chemical Mechanism

A detailed reaction mechanism for the combustion of biodiesel fuels has recently been developed by Westbrook and co-workers. This detailed mechanism involves 5037 species and 19990 reactions, which prohibits its direct use in computational fluid dynamic (CFD) applications. In the present work, various mechanism reduction methods included in the Reaction Workbench software were used to derive a semi-detailed biodiesel combustion mechanism, while maintaining the accuracy of the master mechanism for a desired set of engine conditions. The reduced combustion mechanism for a five-component biodiesel fuel was employed in the FORTÉ CFD simulation package to take advantage of advanced chemistry solver methodologies and advanced spray models. Simulations were performed for a Volvo D12C heavy diesel engine fueled by RME fuel using a 72° sector mesh. Predictions were validated against measured in-cylinder parameters and exhaust emission concentrations.
Technical Paper

3D CFD Upfront Optimization of the In-Cylinder Flow of the 3.5L V6 EcoBoost Engine

This paper presents part of the analytical work performed for the development and optimization of the 3.5L EcoBoost combustion system from Ford Motor Company. The 3.5L EcoBoost combustion system is a direct injected twin turbocharged combustion system employing side-mounted multi-hole injectors. Upfront 3D CFD, employing a Ford proprietary KIVA-based code, was extensively used in the combustion system development and optimization phases. This paper presents the effect of intake port design with various levels of tumble motion on the combustion system characteristics. A high tumble intake port design enforces a well-organized stable motion that results in higher turbulence intensity in the cylinder that in turn leads to faster burn rates, a more stable combustion and less fuel enrichment requirement at full load.
Technical Paper

3D Modeling Applied to the Development of a DI Diesel Engine: Effect of Piston Bowl Shape

Multidimensional computations are carried out to aid in the development of a direct injection Diesel engine. Intake, compression, injection and combustion processes are calculated for a turbo-charged direct injection Diesel engine with a single intake valve. The effects of engine speed and engine load, as well as the influence of exhaust gas recirculation are compared to experimental measurements. The influence of piston bowl shape is investigated. Three dimensional calculations are performed using a mesh built from the complete CAD definition of the engine, intake port, cylinder and piston bowl. The injection characteristics are found to be of primary importance in the control of the combustion process. At a given injection set, piston bowl shape can be optimized for fluid dynamic and combustion.
Technical Paper

3D Modelling and Photographic Investigation of Combustion in Hydra DI Diesel Engine

High speed photographs of spray and combustion, obtained from a Hydra direct injection research diesel engine are compared with the predictions made by KIVA-3 computer code. The preprocessor has been modified to generate a grid for an offset bowl and the postprocessor has been extensively reprogrammed to obtain contour maps. The model has been tuned to low load at 2000rpm. Then the predictive capability of the model has been verified at other operating conditions. Predicted results show very good agreement with the experimental data.
Technical Paper

3D Modelling of Combustion and Pollutants in a 4-Valve SI Engine; Effect of Fuel and Residuals Distribution and Spark Location

The SI engine combustion model LI-CFM introduced by Boudier et, al. (1992) [8] is extended to deal with actual engines. New models are proposed to simulate ignition with convection at the spark and flame-wall interaction. The scalar properties of the unburnt gases within the combustion zone are computed. This allows for the computation of flame propagation in temperature, fuel and residual gas stratified charges. A model for NO and CO formation is introduced. It is based on a conditional burnt/unburnt averaging of the reaction rates. Pollutants are created at the flamelet level and evolve in the burnt, gases using a mixed equilibrium/kinetic scheme. All these physical models are implemented in a multi-block version of the Kiva 2 code, KMB. This code is used to simulate a 4-valve engine including intake ports. Initial and boundary conditions are obtained from a ID acoustic code.
Technical Paper

3D Numerical Simulation of Fuel injection and Combustion Phenomena in DI Diesel Engines

Recently the analysis of air-fuel mixing and combustion has become important under the stringent emissions regulations of diesel engines. In the case of gasoline engines, the KIVA computer program has been developed and used for the analysis of combustion. In this paper, the calculations of combustion phenomena in DI diesel engines are performed by modifying the KIVA program so as to be applicable to multi-hole nozzles and arbitrary patterns of injection rate. The thermophysical and ther-mochemical properties of gasoline are altered to those diesel fuel. In order to investigate the ability of this modified program, the calculations are compared with the experiments on single cylinder engines concerning the pressure, flame temperature and mass change of chemical species in cylinders. Furthermore, the calculation for the heavy duty DI diesel engine is performed with this diesel combustion program.
Technical Paper

3D Simulations And Experimental Validation of High EGR - PHCCI Combustion

The present work addresses the possibility to correctly simulate Partial Homogeneous Charge Compression Ignition (PHCCI) combustion, obtained by the application of EGR up to 60% without using detailed kinetic models. In particular, the laminar and turbulent time characteristic model has been analyzed and improved. The study illustrates the prediction capabilities that can be achieved with such an approach. The paper reports the results obtained from the simulation of a single cylinder research engine and a four-cylinder diesel engine to verify the validity of the proposed method independently of engine geometry and configuration. All numerical results are compared with experimental pressure traces and rates of heat release, as well as with NOx and soot emissions over a wide range of operating conditions. With the modified characteristic time model, realistic simulations of engine combustion up to EGR values of about 60% have been obtained for both engines.
Technical Paper

3D Simulations by a Detailed Chemistry Combustion Model and Comparison With Experiments of a Light-Duty, Common-Rail D.I. Diesel Engine

The present paper reports the results of the numerical simulations carried out by means of a modified version of the KIVA-3V code and of the comparison with experimental results obtained by using different optical techniques in a single-cylinder optically accessible diesel engine. The engine is equipped with a commercial four valves cylinder head and a second-generation, Common-Rail injection system. A detailed kinetic model consisting of 283 reactions involving 69 species is applied to simulate the combustion process and the soot and NOx formation. The fuel surrogate model consisting of two constituent components, n-heptane and toluene, approximating the physical and ignition properties of the diesel oil, is considered. The Partially Stirred Reactor (PaSR) assumption is adopted to maintain the computational cost within acceptable limits.
Technical Paper

3D Simulationson Premixed Laminar Flame Propagation of iso-Octane/Air Mixture at Elevated Pressure and Temperature

This paper aims to validate chemical kinetic mechanisms of surrogate gasoline three components fuel by calculating one-dimensional laminar burning velocity of iso-octane/air mixture. Next, the application of level-set method on premixed combustion without consideration the effect of turbulence eddies on flame front is also studied in three-dimensional computational fluid dynamic (3D-CFD) simulation. In the 3D CFD simulation, there is an option to calculate laminar burning velocity by using empirical correlations, however it is applicable only for particular initial pressure and temperature in spark ignition engine cases. One-dimensional burning velocities from lean to rich of iso-octane/air mixture are calculated by using CHEMKIN-PRO with detailed chemistry and transport phenomena as a function of different equivalence ratios, different unburnt temperature and pressure ranges.
Technical Paper

3D Spray Measurement System for High Density Fields Using Laser Holography

To develop injection nozzles and to improve the numerical simulation technology of fuel spray, a measuring technology to analyze the process of disintegration into droplets accurately is required. Performances required by a spray droplets measuring device are: “ability to measure in the combustion condition inside the engine cylinder”, “ability to measure the diameter of spray droplets in high-density fields”, “ability to measure the structure of spray droplets in 3D”, and an improved measuring accuracy of non-spherical droplets. These elements are required in order to analyze the spray droplets structure of gasoline direct injection engines. As a promising method to satisfy these requirements, the laser holography method has been already suggested. However, it has some drawbacks, such as a difficulty in measuring spray droplets in high-density fields and over a long analysis period.
Technical Paper

3D analysis of vapor and liquid phase of GDI injectors using laser induced exciplex fluorescence tomography in a high pressure/high temperature spray chamber

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.
Technical Paper

3D-1D Analyses of the Turbulent Flow Field, Burning Speed and Knock Occurrence in a Turbocharged SI Engine

CFD techniques are more and more utilized in the development of new solutions for performance improvement of internal combustion engines. Three dimensional models, in general, are able to provide detailed and sound information on engine phenomena, but often they are time consuming and hard to be implemented. On the other hand, one-dimensional models can reproduce the entire engine cycle with acceptable computational times; however they need semi-empirical correlations in order to model the flow field details and the burning speed within each cylinder. In this paper, an example of hierarchical structure of 3-D and 1-D models has been proposed. The main performances of a small turbocharged spark-ignition engine have been calculated. Variable-speed and full load operating points have been analyzed. The 3-D model provided the details of the in-cylinder flow field and turbulent indices.
Technical Paper

3D-CFD Methodologies for a Fast and Reliable Design of Ultra-Lean SI Engines

The continuous pursuit of higher combustion efficiencies, as well as the possible usage of synthetic fuels with different properties than fossil-ones, require reliable and low-cost numerical approaches to support and speed-up engines industrial design. In this context, SI engines operated with homogeneous ultra-lean mixtures both characterized by a classical ignition configuration or equipped with an active prechamber represent the most promising solutions. In this work, for the classical ignition arrangement, a 3DCFD strategy to model the impact of the ignition system type on the CCV is developed using the RANS approach for turbulence modelling. The spark-discharge is modelled through a set of Lagrangian particles, whose velocity is modified with a zero-divergence perturbation at each discharge event, then evolved according to the Simplified Langevin Model (SLM) to simulate stochastic interactions with the surrounding gas flow.