A climate and altitude conditioning test bench was developed at the Institute of Energy Efficient Mobility (IEEM) of Karlsruhe University of Applied Sciences to evaluate the overall sustainability of using innovative biofuels in handheld power tools such as chainsaws, trimmers and blowers under any typical operating condition worldwide. The 6 m3 hermetically sealed and thermally insulated test chamber is large enough to fit the entire power tool. A two-stage refrigeration system with intake air drying and electric heating allows for realistic temperature conditions to be set in the test chamber, ranging from arctic cold to tropical heat (-28 to 45 °C). Altitudes of up to 3500 m above sea level can be simulated using a throttle valve at the inlet of the chamber and a pressure-controlled rotary screw compressor positioned downstream the test chamber outlet. The air-cooled engines to be tested are fully exposed to the ambient conditions inside the test chamber, are able to aspirate the conditioned combustion air freely and release both exhaust gas and waste heat into the chamber environment. In order to control the power tool’s operation when the chamber is closed, an adaptive remote control system was specially developed. It enables automatic engine start-up by cable pull (e.g. for cold start testing), engaging the choke valve as well as operating the throttle lever automatically.
This paper discusses the development process, the design, the operating limits of the climate and altitude simulation test bench as well as first tests on the reproducibility of the automatic start procedure, particularly important for future cold start investigations.