Search Results

The European emission legislation for two-wheeler vehicles driven by engines of ≤ 50 cm₃ is continuously developing. One of the most important issues in the near future will be the finalization of the European Commission's proposals for future steps in the emissions regulations as well as the verification of the impacts of current standards on the market. To have a basis for the discussion about these topics, the Association for Emissions Control by Catalyst (AECC) with the Institute for Internal Combustion Engines and Thermodynamics of Graz University of Technology (IVT) carried out an extensive test program to show the actual emission situation of state-of-the-art mopeds including mass and number of particulate matter as well as unregulated gaseous components. One of the main goals of these tests was to measure exhaust emissions without any modifications to the engines of standard production vehicles available on the European market.

One of the most significant current discussions worldwide is the anthropogenic climate change accompanying fossil fuel consumption. Sustainable development in all fields of combustion engines is required with the principal objective to enhance efficiency. This certainly concerns the field of hand-held power tools as well. Today, two-stroke SI engines equipped with a carburetor are the most widely used propulsion technology in hand-held power tools like chain saws and grass trimmers. To date, research tended to focus on two-stroke engines with rich mixture setting. In this paper the advantages and challenges of leaner and/or lean operation are discussed. Experimental investigations regarding the influence of equivalence ratio on emissions, fuel consumption and power have been performed. Accompanying 3D-CFD simulations support the experiments in order to gain insight into these complex processes. The investigations concentrate on two different mixture formation processes, i.e.

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.

More and more stringent emission legislation is implemented in the world wide market of motorcycles leading to higher product costs. But not every market is ready for high technological levels. Therefore the main topic of interest is: “Will a small one cylinder motorbike engine need an electronic device for fuel metering or is it possible to use standard carburetors in combination with some smart but simple ideas, to fulfil EU III cold start emission regulations?” The described ideas deal with a novel secondary air supply, an improved cooling system and simple NOx reduction methods, always paying attention to the performance and driveability of the vehicle. After describing the prototype design of the engine modifications, the achievable results with their pros and cons are discussed. Online recorder measurements give interesting emission plots of HC, CO and NOx. The homologation measurement results point out the obtainable values of the limited emissions.

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.

In a variety of applications, two-stroke engines assert their usage as a propulsion unit, for examples in off-road vehicles, scooters, hand-held power tools and others. The outstanding power to weight ratio is the key advantage for two-stroke engines. Furthermore, two-stroke engines convince with high durability and low maintenance demand. However, an increasing environmental awareness, the protection of health and the shortage of fossil resources are the driving factors to further enhance the internal combustion process of two-stroke engines. The reduction of emissions and fuel consumption with a constant power level is focused on. Developments deal with the optimization of the combustion process itself or the enhancement of the exhaust gas aftertreatment. Especially in very small two-stroke engines an exhaust gas aftertreatment system is rarely applied, due to disadvantages regarding component temperatures and product costs.

Due to the small number of two wheelers in Europe and their seasonal use, their contribution to the total emissions has been underestimated for a long time. With the implementation of the new emission regulation 168/2013 [3] for type approval coming into force 2016, the two wheeler sector is facing major changes. The need to fulfil more stringent emission limits and the high demand on the durability of after treatment systems result in an engine control system that is getting more complex and therewith more expensive. Especially the low cost two wheelers with small engine capacities will be affected by increasing costs which cannot be covered by the actual competitive product price. Therefore, new vehicle concepts have to be introduced on the market. A vehicle concept of a plug in hybrid electric city scooter with range extender as well as the range extender itself have already been published in SAE Papers 2011-32-0592 [1] and 2012-32-0083 [2].

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.

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.

Small engines for non-automotive and two wheeler applications have a reduced number of sensors. For fulfilling emission regulations a cost effective way is an enhanced use of standard sensors in order to obtain more information from the existing sensors. The delivered information can then be used for an on-board diagnosis. Moreover, it is important to control the quality of the product during engine production; therefore an end-of-line cold engine test is often made. With this measure it is possible to detect faults, wrong tolerances or assembly in order not to deliver faulty engines to the customers. In this paper, an enhanced use of sensors for fault detection will be discussed. It is possible to obtain more information from the signal or to use the sensor for detecting other parameters. For extracting information signal analysis methods will be used with focus on the computational power need since the ECU performance is limited.

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.

State of the art technologies of 2 and 4 stroke engines have to fulfill severe future exhaust emission regulations, with special focus on the aspects of rising performance and low cost manufacturing, leading to an important challenge for the future. In special fields of applications (e.g. mopeds, hand held or off-road equipment) mainly engines with simple mixture preparation systems, partially without exhaust gas after treatment are used. The comparison of 2 and 4 stroke concepts equipped with different exhaust gas after treatment systems provides a decision support for applications in a broad field of small capacity engine classes.

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.

An efficient and low cost way to supercharge a four stroke engine is to use the bottom side of the piston to increase the volumetric efficiency. In comparison to naturally aspirated (NA) engines, this supercharging concept pre-compresses the intake air in the crankcase resulting in a significant increase of torque and power output. On a prototype engine fundamental research activities were carried out on a driven flow test bench to optimize the volumetric efficiency by varying the influencing parameters. Subsequently the characteristics of different mixture preparation concepts (carburetor and fuel injection system) in combination with the treated supercharging concept have been studied during the development phase on engine test bench.

In the course of the last few years a continuous increase of the injection pressure level of gasoline direct injection systems appeared. Today's systems use an injection pressure up to 200bar and the trend shows a further increase for the future. Although several benefits go along with the increased injection pressure, the disadvantages such as higher system costs and higher energy demand lead to the question of the lowest acceptable injection pressure level for low cost GDI combustion systems. Lowering injection pressure and costs could enable the technological upgrading from MPFI to GDI in smaller engine segments, which would lead to a reduction of CO2 emission. This publication covers the investigation of a low pressure GDI system (LPDI) with focus on small and low cost GDI engines. The influence of the injection pressure on the fuel consumption and emission behavior was investigated using a 1.4l series production engine.

In consideration of the fact that in extreme Enduro competitions two-stroke motorcycles are still dominating, the Institute of Internal Combustion Engines and Thermodynamics, Graz University of Technology, with a long tradition in two-stroke technology, has developed a new 300 cm3 two-stroke motorcycle engine. The 2-stroke LPDI (Low Pressure Direct Injection) technology was originally developed for the 50 cm3 Scooter and moped market in Europe. In 50 cm3 applications the LPDI technology fulfils the EURO 4 emission standard (2017) [1]. In a next step the LPDI technology was applied to a 250 cm3 Enduro engine demonstrator vehicle. Based on the results of the demonstrator, a complete new high performance 300 cm3 engine was developed. The development of this new engine will be described in this publication. Some interesting aspects of the layout with 3D-CFD methods and also 1D-CFD simulation to optimize the exhaust system by DoE methods are discussed in the paper.