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Amid the increasing demand for higher efficiency in combustion driven handheld tools, the recent developments in electric machine technology together with the already existing benefits of small combustion engines for these applications favor the investigation of potential advantages in hybrid powertrain tools. This concept-design study aims to use a fully parametric, system-level simulation model with exchangeable blocks, created with a power-loss approach in Matlab and Simulink, in order to examine the potential of different hybrid configurations for different tool load cycles. After the model introduction, the results of numerous simulations for 36 to 100 cc engine displacement will be presented and compared in terms of overall system efficiency and overall powertrain size. The different optimum hybrid configurations can show a reduction up to 30 % in system’s brake specific fuel consumption compared to the baseline combustion engine driven model.

The Institute for Internal Combustion Engines and Thermodynamics, Graz University of Technology, has presented several applications of its 2-stroke LPDI (low pressure direct injection) technology in the previous years ([1], [2], [3]). In order to improve the competitiveness of the 2-stroke LPDI technology, an air cooled 50cm3 scooter application has been developed. All previous applications have been liquid cooled. This air cooled application demonstrates the EURO 4 (2017) ability of the technology and shows that the 2S-LPDI technology can also be applied to low cost air-cooled engines. Hence, the complete scooter and moped fleet can be equipped with this technology in order to fulfil both the emission standards and the COP (conformity of production) requirements of Euro 4 emission stage. The paper presents the Euro 4 Scooter results and describes the efficient conversion process of the existing carburetor engine to the LPDI version.

For the development of high-performance 2-stroke engines with internal mixture preparation it is essential to know about the interaction between charge motion and injection spray. With no prototypes available conceptual investigations can only render such information by using 3D CFD simulation. In this way an optimization of mixture preparation and charge motion can be achieved by varying the transfer and boost ports. To allow for the influence of these modifications on the mass balance (volumetric and trapping efficiency), the entire system of the loop-scavenged two-stroke engine has to be investigated. The state of the art calculation domain for 2-stroke 3D CFD simulation is bounded at the inlet of the crankcase (reed valve) and sometimes also at the outlet of the cylinders. The reasons lie in the so far not sufficiently reproducible components (e.g. reed valve) as well as in the reduction of calculation time.

Based on the fundamental analysis of the two-stroke process (SETC 2005-32-0098) and the development of a stratified scavenged small capacity two-stroke engine (SETC 2006-32-0065), a further approach to achieve low emissions in this engine category is the main subject of this publication. The principles of the system are described by design activities, results of the 3D-CFD simulation and the visualization of the spray in the cylinder. The benefit of this system on exhaust emissions is demonstrated by engine test bench as well as chassis dynamometer results. The achievable reduction of exhaust emissions, especially with an applied oxidation catalytic converter, is remarkable and the potential to fulfill future emission limits has already been demonstrated.

Affordable, efficient and durable catalytic converters for the two and three wheeler industry in developing countries like India are required to reduce vehicle emissions and to maintain them at a low level and therefore to participate in a cleaner and healthier environment. A new generation of metallic substrates with structured foils for catalytic converters has been proven capable of improving conversion behavior even with smaller catalyst size. Specially developed foil structures which transform a laminar exhaust gas flow into a turbulent one, which significantly improve exhaust gas mixing behavior in the catalyst. This publication will deal with the analysis of different metallic substrate foil structures for the catalyst conversion performance for the leading “state of the art” four stroke 150 cm3 motorcycle technology developed for the Asian market.

As the number of different engine and vehicle concepts for powered-two wheelers is very high and will even rise with hybridization, the simulation of emissions and fuel consumption is indispensable for further development towards more environmentally friendly mobility. In this work, an adaptive artificial neural network based predictive model for emission and fuel consumption simulation of motorcycles operated in real world conditions is presented. The model is developed in Matlab and Simulink and is integrated into a longitudinal vehicle dynamic simulation whereby it is possible to simulate various and not yet measured test cycles. Subsequently, it is possible to predict real drive emissions RDE and on-road fuel consumption by a minimum of previous measurement effort.

This publication covers investigations on different 3D CFD models for the description of the spray wall and droplet-fluid interaction and the influence of these models on the mixture formation calculation results. Basic experimental investigations in a spray chamber and a flow tunnel as well as the corresponding 3D CFD simulation were conducted in order to clarify the prediction quality of the physical phenomena of spray-wall and spray-fluid interaction by the simulation. Influencing parameters such as the piston top temperature, piston bowl geometry, soot deposits on the piston top as well as flow velocity are investigated. This paper provides a direct link between the underlying simulation models of the mixture formation and actual real world combustion system development processes - underlining the importance of a close interaction of the model calibration and the development process.

In industrial processes and other power generation processes, large amounts of waste heat are often lost to the environment. The conversion of this thermal energy into mechanical work promises a significant improvement in energy-utilization, the efficiency of the overall system and, consequently, cost-effectiveness. Therefore, the use of a Rankine-Cycle is a well-established technical process. A recent research project has investigated a novel expansion machine to be integrated into such an RC-process. Primarily, the present work deals with the fluid dynamic simulation of this expander, which is based on the principle of a rotary piston engine. The aim is to develop, analyze and optimize the process and the corresponding components. Hence, a CFD-model had to be built up, which should correspond as closely as possible to the physical engine.

The demand for high efficiency powertrains in automotive engineering is further increasing, with hybrid powertrains being a feasible option to cope with new legislations. So far hybridization has only played a minor role for L-category vehicles. Focusing on an exemplary high-power L-category on-road vehicle, this research aims to show a new development approach, which combines longitudinal dynamic simulation (LDS) with “Design of Experiments” (DoE) in course of hybrid electric powertrain development. Furthermore, addressing the technological aspect, this paper points out how such a vehicle can benefit from 48V-hybridization of its already existing internal combustion powertrain. A fully parametric LDS model is built in Matlab/Simulink, with exchangeable powertrain components and an adaptable hybrid operation strategy. Beforehand, characterizing decisions as to focus on 48V and on parallel hybrid architecture are made.

Legislative regulations and international agreements like the Paris Agreement have been prepared to enforce the effort to reduce the emission of greenhouse gases (GHGs). Greater environmental awareness among customers and introduction of strict environmental regulations have challenged designers to consider the environmental impact of products together with traditional design objectives in the early stages of product design. An important environmental impact factor is the carbon footprint of a product because carbon dioxide (CO2) emissions are a main cause of the global climate change. An early assessment of the product carbon footprint is beneficial because at this stage, design changes are still possible with little effort and at low cost. Actually, there is no detailed methodology for a CO2 impact estimation in the early design phases available and very few researches have been conducted for the special segment of small powertrains.

An efficient and economic method to increase the performance of four stroke engines can be accomplished by utilizing the crankcase supercharging method. The lubrication of the movable parts in the crankcase by mixing the intake air with lubricant leads to a high oil consumption and disadvantages in the emission characteristics. This paper describes parts of a research project with the goal to develop a supercharged four–stroke engine with a closed loop lubrication system for the crank train and the cylinder head. The thermodynamic layout and the development of an oil separating system have been carried out with the help of simulation tools and development work on a flow test bench.

Modern small capacity motor scooters make high demands on a trendy vehicle design in combination with a customer friendly handling and multifarious storage space. In addition, increasing engine performance characteristics and high requirements on the vehicle weight call for the development of new vehicle frame concepts. Considering lightweight construction and strength durability, the new concepts are also due to fulfill the boundaries of a low cost production. The driving behavior of a scooter is directly influenced by the interaction of the suspension components, the mounting system of the drive unit and the stiffness of the frame. The present publication treats an assessment of different frame types in the 50cc scooter class by tests and simulation with the target to formulate key data regarding the solidness and stiffness characteristics. Based on these data collection a complete new frame concept has been designed and revised by calculation.

Based on the fundamental analysis of the two-stroke process and the first results of the 3D-CFD simulation (Paper No: SETC 2005-32-0098), the development of a small capacity two-stroke engine is the subject of this publication. The developed 50 cm3 two-stroke engine is applied with a low pressure fuel injection system and allows, due to the special positioning of the fuel injector, two different scavenge modes. The first mode is a standard homogenous scavenge mode and the second one is for a stratified scavenged engine operation. Both modes can be achieved only by the adjustment of the injection timing without any restrictions concerning possible phasing. The system only deals with one fuel injector; special constraints concerning the transition between stratified and homogenous operation are not required. Any possible mixture can be applied between stratification and homogenous mode.

Usually the power output of 50 cm₃ two wheelers is higher than necessary to reach the maximum permitted vehicle speed, making engine power restriction necessary. This publication deals with different power restriction strategies for four-stroke engines and their effect on exhaust emissions. Alternative power limitation strategies like EGR and leaning were investigated and compared with the common method of spark advance reduction to show the optimization potential for this certain engine operation conditions. From these tests, a substantial set of data showing the pros and cons in terms of emissions, combustion stability and fuel economy could be derived for each speed limiting technique.

In the early phase of an engine development process, the main characteristics of an engine setup, such as lengths, diameter and volumes, are usually defined by means of 1D CFD simulation technologies. Only single flow situations are modeled in 3D due to the high expenditure of time and money. This paper presents a new efficient development methodology using 1D, 3D as well as coupled 1D/3D simulation techniques - the described simulation strategy leads to a more realistic and more comparable reproduction of the flow situation, especially in the critical areas of the simulation domain, while avoiding the restrictions and disadvantages of 1D and 3D simulation. By the use of test bench results of a comparable prototype engine, the quality of the simulation strategy has been successfully verified.

In recent years, E-mobility relevance has increased in the automotive sector, yet pure electric vehicles struggle to establish themselves in the still internal combustion engine (ICE) dominated sector of L-category and powersport applications. Battery electric hybrid L-category vehicles, as considered in this paper, combine both ICE and electric powertrains. Nowadays, numerous ICE L-category vehicles use rubber V-belt continuous variable transmissions (CVT) due to their reliability and user-friendliness, which often outweighs the drawback of relatively low efficiency. This paper not only aims to show, with the help of longitudinal dynamic simulation (LDS), how a state-of-the-art L-category ICE powertrain with special focus on the CVT can benefit from hybridization in terms of overall efficiency, but furthermore points out where the efficiency increase actually comes from and how this new knowledge can be implemented intelligently into a hybrid strategy.

Meeting future legislative targets for SI engines by means of low cost technologies is a big challenge for engineers. Despite the use of simple and cost efficient components these engines have to fulfill customer requirements in terms of power and fuel economy, representing the most important selling arguments. Without the possibility of integrating modern technologies like fuel injection systems for mixture preparation instead of simple carburetors, it is very complex to find viable solutions that enable the achievement of these targets. A main key to improve emission behavior, fuel economy and performance on carbureted engines is to get an insight in the mixture preparation process, especially under transient conditions.

The enhancement of efficiency will play a more and more important role in the development of future (small) internal combustion engines. In recent years, the Atkinson cycle, realized over the crank drive, has attracted increasing attention. Several OEMs have been doing investigations on this efficiency-increasing principle with in the whole range from small engines up to automotive ones. In previous publications, the authors stated that an indicated efficiency of up to 48% could be reached with an Atkinson cycle-based engine. However, these studies are based on 1D-CFD simulation. To verify the promising simulation results, a prototype engine, based on the Atkinson principle, was designed and experimentally tested. The aim of the present study is to evaluate and validate the (indicated) engine efficiency gained by experimental tests compared to the predicted simulation results. In order to investigate part load behavior, several valve timing strategies were also developed and tested.

Small combustion engines can be found in various applications in daily use (e.g. as propulsion of boats, scooters, motorbikes, power-tools, mobile power units, etc.) and have predominated these markets for a long time. Today some upcoming competitive technologies in the field of electrification can be observed and have already shown great technical advances. Therefore, small combustion engines have to keep their present advantages while concurrently minimizing their disadvantages in order to remain the predominant technology in the future. Whereas large combustion engines are most efficient thermal engines, small engines still suffer from significantly lower efficiencies caused by a disadvantageous surface to volume ratio. Thus, the enhancement of efficiency will play a key role in the development of future small combustion engines. One promising possibility to improve efficiency is the use of a longer expansion than compression stroke.

The automotive industry has made great efforts in reducing fuel consumption. The efficiency of modern spark ignition (SI) engines has been increased by improving the combustion process and reducing engine losses such as friction, gas exchange and wall heat losses. Nevertheless, further efficiency improvement is indispensable for the reduction of CO2 emissions and the smart usage of available energy. In the previous years the Atkinson Cycle, realized over the crank train and/or valve train, is attracting considerable interest of several OEMs due to the high theoretical efficiency potential. In this publication a crank train-based Atkinson cycle engine is investigated. The researched engine, a 4-stroke 2 cylinder V-engine, basically consists of a special crank train linkage system and a novel Mono-Shaft valve train concept.