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In order to meet the new stringent emission limits for small handheld power tools technologies like methods to improve the scavenging process and after treatment devices are deployed. Additionally, professional machines such as chain saws add particular requirements to avoid mechanical failures. By precise control of the carburetion it is possible to yield the necessary reduction of the emission level yet to maintain the performance of the engine. Thus, the development of an Electronically Controlled Carburetion System to reduce the exhaust emissions of small IC engines for handheld power tools was initiated at the WHZ, Germany. Key requirements of such a system are: low cost, high reliability, low electrical power consumption, high accuracy in metering the fuel demand of the engine. First results are promising. A correlation between exhaust gas temperature and the fuel demand of the engine was confirmed for both, wide open throttle and part load operation.

An overview of the design of the kickback machine can be extracted from ISO 9518 [1]. Details and specific information were spelled out in a bill of material defined during the development process leading to ISO 9518, but today these materials are no longer available. The presented paper describes the newly designed kickback machine, which fulfills the requirements given by ISO 9518 by using an electronic measurement method to determine the released kinetic energies necessary to calculate the “computed kickback angle” CKA, which enhances the accuracy of the test. Moreover, the measurement principle allows a direct computation of the velocity at which the wooden test sample hits the moving saw chain to provoke the kickback of the saw. Thus, the necessary number of sensors on the testing machine is reduced, by eliminating the velocity-timing-device.

Two-stroke engines are widely used in handheld power tools due to the demand in high power-weight-ratio and reliability. Particularly, two-stroke engines remain to be the ultimate power source for handheld chain saws and continuous efforts resulted in an improved engine design with increased power output and reduced weight. Besides these continuing efforts engine manufactures must make their products compatible to exhaust emission standards, which have been implemented in most of the important markets worldwide [1], [2]. One particular area of interest is the scavenging process of naturally aspirated two-stroke engines, which affects power and emission output, both. Advanced scavenging methods offer the possibility to design two-stroke engines which achieve the lowest present emission levels i.e. hydrocarbons plus nitrogen-oxides: 50 g/kWh without compromising the power output at given engine parameters such as displacement or rated speed.

This paper presents a racing bike with electrical drive train, which shall be used as a prototype of a future electro racing class and as well as a test bed for future driving performance and sound tests. All major components of the drive train including motor, battery, battery controller and wiring are described in detail. Safety issues related to the selection of the voltage level are discussed. The mechanical integration of the electrical drive train into a given racing bike is presented. Moreover, power and torque characteristics of the motor and the total weight of the motorcycle are put into relation to performance requirements of the racing class in question. The electric drive train has a modular design and can be simplified compared to internal combustion engines, because of the favorable torque characteristic of electric motors a gearbox is not necessary. Sound issues of both, the conventional racing bike and the electrically powered one are discussed.

A detailed knowledge of the scavenging process becomes necessary during the development process, when the performance and in particular the emission output of two-stroke engines needs to be qualified and evaluated. This paper presents an experimental approach to describe the composition of the flow at the exhaust port by means of flow visualization and to quantify the relative changes of the scavenging losses imposed by design changes. The experimental set-up has been described in previous SAE papers and has been expanded by a transparent exhaust port, which gives optical access to the flow through the exhaust port. The gases in the cylinder are represented by differently colored water-based fluids. Typically, the burnt gas is clear and the fresh charge is colored to visualize its progress during the scavenging cycle and its distribution inside the cylinder.

A method is presented which allows the investigation of the flow inside the cylinder and the transfer channels of small two-stroke cylinders under the condition of an expanded time scale by using the similarity laws. A test rig has been designed to incorporate the application of visualization techniques as well as quantitative measurement systems like LDV or PIV. The results obtained by this method are needed to understand the complex nature of the three-dimensional flow inside the cylinder and can be used to verify CFD calculations. Moreover, modifications can be applied to the model in an easy and fast manner, which enables the designer to examine various versions during the early stage of the development process.

Experimental methods are needed to understand unsteady three-dimensional flows. They also become an important tool where geometrical details or the complexity of the applied model would require an over-proportional numerical effort to investigate a scavenging flow. The experimental method presented in this paper applies visualization techniques to analyze the scavenging flow of small two-stroke cylinders. The principle at work is based on similarity laws, which transfer the dimensions of an actual engine into an enlarged model. The modular set-up allows fast modifications of the port geometry and detailed visualization of the flow coming out of individual transfer ports of multiple port cylinders by using different dyes. Results are presented as movies, which give a very graphic impression of the unsteady three-dimensional flow inside the cylinder.