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Technical Paper

3D-CFD Modeling of Conventional and Alternative Diesel Combustion and Pollutant Formation - A Validation Study

An improved version of the ECFM-3Z combustion model coupled with advanced models for NO and soot formation has been implemented in the CFD code FIRE and validated with respect to its applicability to conventional and alternative Diesel combustion. For this purpose the set of models was applied to the calculation of combustion and pollutant formation in a high-speed DI Diesel engine for selected operating points adopting a large number of DoE based combustion system parameter variations. Assessment of the models' performance was enabled via comparison of the calculation results with the corresponding experimental data. Good agreement of calculated and measured in-cylinder pressure traces as well as pollutant formation trends could be observed for both the conventional and alternative Diesel combustion modes for the investigated parameter variations.
Technical Paper

3D-CFD Modelling of Gas Exchange and Combustion Inside the Expander of a Recuperated Split-Cycle Engine

The demand of game-changing technologies to improve efficiency and abate emissions of heavy-duty trucks and off-road vehicles promoted the development of novel engine concepts. The Recuperated Split-Cycle (R-SC) engine allows to recover the exhaust gases energy into the air intake by separating the compression and combustion stages into two different but connected cylinders: the compressor and expander, respectively. The result is a potential increase of the engine thermal efficiency. Accordingly, the 3D-computational fluid dynamics (CFD) modelling of the gas exchange process and the combustion evolution inside the expander becomes essential to control and optimize the R-SC engine concept. This work aims to address the most challenging numerical aspects encountered in a 3D numerical simulation of an R-SC engine.
Technical Paper

3D-CFD Simulation of DI-Diesel Combustion Applying a Progress Variable Approach Accounting for Detailed Chemistry

A chemical sub-model for realistic CFD simulations of Diesel engines is developed and demonstrated by application to some test cases. The model uses a newly developed progress variable approach to incorporate a realistic treatment of chemical reactions into the description of the reactive flow. The progress variable model is based on defining variables that represent the onset and temporal development of chemical reactions before and during self ignition, as well as the stage of the actual combustion. Fundamental aspects of the model, especially its physical motivation and finding a proper progress variable, are discussed, as well as issues of practical implementation. Sample calculations of Diesel-typical combustion scenarios are presented which are based on the progress-variable model, showing the capability of the model to realistically describe the ignition-and combustion phase.
Journal Article

3D-CFD Virtual Engine Test Bench of a 1.6 Liter Turbo-Charged GDI-Race-Engine with Focus on Fuel Injection

In the last years motorsport is facing a technical revolution concerning the engine technology in every category, from touring car championships up to the F1. The strategy of the car manufacturers to bring motorsport engine technology closer to mass production one (e.g. turbo-charging, downsizing and direct injection) allows both to reduce development costs and to create a better image and technology transfer by linking motorsport activities to the daily business. Under these requirements the so-called Global Race Engine (GRE) concept has been introduced, giving the possibility to use one unique engine platform concept as basis for different engine specifications and racing categories. In order to optimize the performance of this kind of engines, especially due to the highly complex mixture formation mechanisms related to the direct injection, it is nowadays mandatory to resort to reliable 3D-CFD simulations.
Technical Paper

3D-Simulation of DI-Diesel Combustion Applying a Progress Variable Approach Accounting for Complex Chemistry

A progress variable approach for the 3D-CFD simulation of DI-Diesel combustion is introduced. Considering the Diesel-typical combustion phases of auto-ignition, premixed and diffusion combustion, for each phase, a limited number of characteristic progress variables is defined. By spatial-temporal balancing of these progress variables, the combustion process is described. Embarking on this concept, it is possible to simulate the reaction processes with detailed chemistry schemes. The combustion model is coupled with a mesh-independent Eulerian-spray model in combination with orifice resolving meshes. The comparison between experiment and simulation for various Diesel engines shows good agreement for pressure traces, heat releases and flame structures.
Technical Paper

3DCFD-Modeling of a Hydrogen Combustion-Process with Regard to Simulation Stability and Emissions

In the context of the energy transition, CO2-neutral solutions are of enormous importance for all sectors, but especially for the mobility sector. Hydrogen as an energy carrier has therefore been the focus of research and development for some time. However, the development of hydrogen combustion engines is in many respects still in the conception phase. Automotive system providers and engineering companies in the field of software development and simulation are showing great interest in the topic. In a joint project with the industrial partners Robert Bosch GmbH and AVL Germany, combustion in a H2-DI-engine for use in light-duty vehicles was methodically investigated using the CFD tool AVL FIRE®. The collaboration between Robert Bosch GmbH and the Institute for Mobile Systems (IMS) at Otto von Guericke University Magdeburg has produced a model study in which model approaches for the combustion of hydrogen can be analyzed.
Technical Paper

4-Stroke Multi-Cylinder Gasoline Engine with Controlled Auto-Ignition (CAI) Combustion: a comparison between Naturally Aspirated and Turbocharged Operation

Controlled Auto-Ignition (CAI) also known as Homogeneous Charge Compression Ignition (HCCI) is increasingly seen as a very effective way of lowering both fuel consumption and emissions. Hence, it is regarded as one of the best ways to meet stringent future emissions legislation. It has however, still many problems to overcome, such as limited operating range. This combustion concept was achieved in a production type, 4-cylinder gasoline engine, in two separated tests: naturally aspirated and turbocharged. Very few modifications to the original engine were needed. These consisted basically of a new set of camshafts for the naturally aspirated test and new camshafts plus turbocharger for the test with forced induction. After previous experiments with naturally aspirated CAI operation, it was decided to investigate the capability of turbocharging for extended CAI load and speed range.
Technical Paper

42V Integrated Starter/Alternator Systems

The increasing power demand in vehicles has resulted in a need for a higher onboard generation capacity. With the increasing generation requirement, the torque levels of the generator are found to closely converge with that of the starter motor. Hence, integrating the two machines and using a single machine for the two purposes would be technically viable and economically advantageous. This results in a more compact design solution as well. The Integrated Starter/Alternator (ISA) will be integrated directly to the crankshaft of the Internal Combustion Engine (ICE) and deliver 5 kW average and 12-15 kW peak power at 42V.
Technical Paper

48V Boost Recuperation Systems - Golden Gate into the Future

The transformation of the automotive industry will be shaped mainly by the markets North America, Europe and China, which account for more than two thirds of the yearly global car production. All three markets have challenging fuel consumption, CO2 and emission regulations in place and under discussion, which are forcing the automotive industry to make their power train technology more efficient. But not only governmental regulations are driving the change, increasing urbanization intensifies local environmental pollution from vehicles and strains the acceptance of today’s car centric mobility. Electrification is the highly touted magic solution, but is it fast and comprehensive enough to solve above mentioned problems? Is society - car owners, automotive industry and governments - willing to pay the high cost for electrified car technology and infrastructure within a short timeframe of 10 to 15 years?
Technical Paper

4th Generation Diesel Piezo Injector (Realizing Enhanced High Response Injector)

Diesel common rail injectors are required to utilize a higher injection pressure and to achieve higher injection accuracy in order to meet increasingly severe emissions, less fuel consumption, and higher engine performance demand. In addition to those requirements, in conjunction with optimized nozzle geometry, a more rectangular injection rate and stable multiple injections with shorter intervals are required for further emissions and engine performance improvement by optimizing the combustion efficiency.
Technical Paper

54 The Combustion Phenomena Under Corona Discharge Application

In this study, the effect of corona discharge on the combustion phenomenon has been made clear. A homogeneous propane-air mixture was used and six equivalence ratios were tested. For generating the positive and negative corona discharge, a non-uniform electric field was applied to the combustion chamber by the needle to plane gap. One or five needle-shaped electrodes were used to change the corona discharge state. When the positive corona discharge was applied, the luminescence from corona with five electrodes was weak as compared with that of one needle-shaped electrode. When the negative corona discharge was applied, the luminescence from corona and combustion were not affected by the number of electrode. When the positive corona discharge was applied by low voltage, the combustion was improved in the case of one needle-shaped electrode, but the index of combustion with one needle-shaped electrode was almost equal to that of five electrodes when the high voltage was applied.
Technical Paper

60 TCT - Total Combustion Technology

TCT - Total Combustion Technology is technology designed to enable small SI four-stroke and two-stroke engines to meet current and proposed emission standards that pertain to small engines. This paper outlines the technology, the testing equipment, and the results from tests comparing TCT to original carburetors on two different engines. The comparison shows clearly that emissions can be reduced substantially by TCT. The MLC (Mechanical Lambda Control) feature of TCT allows the emission profile of the engine to be matched to the application in each case.
Technical Paper

65 New Indicated Mean Effective Pressure Measuring Method and Its Applications

IMEP can be generally calculated by numerical integration on the PV diagram. However, this method requires a great number of sampled data per cycle, in order to ensure high accuracy in calculation. The present method is a to use only the primary and secondary components of engine speed from the pressure diagram based on the Fourier series. Owing to this method, calculation errors have become smaller than conventional method even though the number of samples is reduced, and calculation time is also reduced by the conventional method. Using present method, a Fourier series type combustion analyzing system has been developed. Real-time IMEP measurement is allowed in this system owing to the characteristic features described above, and the validity of calculated results is confirmed by comparing the results with the IMEP values obtained by batch processing through the numerical integration.
Technical Paper

67 Analysis of Mixture Conditions in a Small Two Stroke Engine Using a Gas Sampling Valve

The quality of mixture formation and the combustion process is of significant importance for reducing the hydrocarbon emissions of small two stroke engines. The scope of this work was to investigate the mixture conditions after the exhaust closes and after the end of combustion depending on various engine operating points. For this experimental investigation a Gas Sampling Valve (GSV) was combined with a flame ionisation detector (FID) and a CO2-analyser. Using this technique, it was possible to measure the hydrocarbon concentration after end of combustion. Furthermore the local residual gas concentration after exhaust closes was determined. To allow for a comparison of the experimental results with calculations with CFD codes, in cylinder pressure measurement and exhaust gas measurements are done additionally.
Technical Paper

7 Experimental Research Concerning the Effect of the Scavenging Passage Length on the Combustion State and Exhaust Gas Composition of a Small Two-stroke Engine

This paper presents the results of experiments conducted with a two-stroke engine that was the world's first such engine to comply with the emissions regulations applied to small off-road engines by the U.S. state of California in 2000. This engine is fitted with a scavenging passage that runs around the crankcase before the scavenging port. The aim of this research was to investigate how changes in the quantity of heat transferred to the fresh air as a result of varying the length of the scavenging passage would affect the state of combustion and exhaust gas composition. An ion probe was fitted to the end zone of the combustion chamber in order to detect the state of combustion. A voltage of 60 V was applied to the ion probe and measurements were made of the voltage drop that occurred due to the presence of high concentrations of ions (H3O+, C3H3+, CHO+, etc.) at the flame front.
Technical Paper

77 Basic Investigation of Particulate Matters (O-PM)) and Polycyclic Aromatic Hydrocarbons Emitted by Two-stroke Motorcycles

Characteristics of mass emission of unburned Oil-Particulate Matter and polycyclic aromatic hydrocarbons from two-stroke scooter were investigated. The tests were carried out under with and without oxidation catalyst and various air-fuel ratio ranging from 12 to 16 at 50:1 of fuel-oil mixing ratio for easy sampling. Unburned Oil-Particulate Matter and 4- to 7-rings polycyclic aromatic hydrocarbons were trapped on filter. These compounds were analyzed by high performance liquid chromatography with fluorescence detector. Mass emission of polycyclic aromatic hydrocarbons and unburned Oil-Particulate Matter tends to decrease as air-fuel ratio which increased up to stoichiometric ratio. The highest conversion ratio of unburned Oil-Particulate Matter on the oxidation catalyst was 64%. Conversion ratio of polycyclic aromatic hydrocarbons increased as rings are smaller.
Technical Paper

78 Development of a combustion analyzer to load onto a motorcycle

In many cases of the development of motorcycle engines, the combustion analysis has been of the engine in laboratory, not of the one onto actual motorcycles. It is mainly because the combustion analyzer in the market is too large to load onto a motorcycle. Pressure sensor, crank angle detector, arithmetic unit and data record device are necessary to analyze the combustion. The arithmetic unit is to process detected signals and generally needs the largest space among them. Needless to say, more reliable results of the combustion analysis could not be obtained under such limited experimental conditions. Therefore, we developed a compact combustion analyzer, which is possible to be loaded onto a motorcycle. The width of the arithmetic unit is 91mm, the depth 98mm and the thickness 20mm. The core chip has the calculation ability of 78MIPS at a clock speed 60MHz, and it has AD converter, DA converter and high-speed counter.
Technical Paper

8 A Study of the Influence of Fuel Temperature on Emission Characteristics and Engine Performance of Compression Ignition Engine

In this study, the heated fuels were provided to the diesel engine in order to activate the fuel before the injection. Two test fuels: the normal diesel fuel and cetane, which have different boiling points were used. For both normal diesel fuel and cetane, crank angles at ignition and maximum pressure are delayed and the maximum combustion pressure is decreased as the fuel temperature rises. In cases of large and middle mass flow rate of fuel injection, the brake thermal efficiency and brake mean effective pressure are decreased when the fuel temperature is higher than 570 [K]. However, in the case of small mass flow rate of fuel injection, the brake thermal efficiency is almost independent of fuel temperature. HC and CO concentrations in the exhaust gas emission show constant values regardless of fuel temperature. However, NOx concentration is gradually decreased as the fuel temperature rises.
Journal Article

A 0D Phenomenological Approach to Model Diesel HCCI Combustion with Multi-Injection Strategies Using Probability Density Functions and Detailed Tabulated Chemistry

More and more stringent restrictions concerning the pollutant emissions of ICE (Internal Combustion Engines) constitute a major challenge for the automotive industry. New combustion strategies such as LTC (Low Temperature Combustion), PCCI (Premixed Controlled Compression Ignition) or HCCI (Homogeneous Charge Compression Ignition) are promising solutions to achieve the imposed emission standards. They permit low NOx and soot emissions via a lean and highly diluted combustion regime, thus assuring low combustion temperatures. In next generation of ICE, new technologies allow the implementation of complex injection strategies in order to optimize the combustion process. This requires the creation of numerical tools adapted to these new challenges. This paper presents a 0D Diesel HCCI combustion model based on a physical 3D CFD (Computational Fluid Dynamics) approach.
Technical Paper

A 0D Phenomenological Model Using Detailed Tabulated Chemistry Methods to Predict Diesel Combustion Heat Release and Pollutant Emissions

In the last two decades, piston engine specifications have deeply evolved. Indeed, new challenges nowadays concern the reduction of pollutant emissions (EURO regulations) and CO2 emissions. To satisfy these new requirements, powertrains have become very complex systems including a large number of high technology components (high pressure injectors, turbocharger, Exhaust Gas Recirculation (EGR) loop, after-treatment devices...). In this context, the engine control plays a major role in the development and the optimization of powertrains. Few years ago, engine control strategies were mainly defined by experiments on engine test benches. This approach is not adapted to the complexity of future engines: on the one hand, tests are too expensive and on the other hand, they do not give much information to understand interactions between components. Today, a promising alternative to tests may be the use of 0D/1D simulation tools.