Development of a Micro-Engine Testing System 2012-32-0105

A test stand was developed to evaluate an 11.5 cc, two-stroke, internal combustion engine in anticipation of future combustion system modifications. Detailed engine testing and analysis often requires complex, specialized, and expensive equipment, which can be problematic for research budgets. This problem is compounded by the fact that testing “micro” engines involves low flow rates, high rotational speeds, and compact dimensions which demand high-accuracy, high-speed, and compact measurement systems. On a limited budget, the task of developing a micro-engine testing system for advanced development appears quite challenging, but with careful component selection it can be accomplished.

The anticipated engine investigation includes performance testing, fuel system calibration, and combustion analysis. To complete this testing, a custom test system was developed. First, a test stand was machined to mount the engine and a brushless, direct current (BLDC) motor, which were connected using a zero-backlash coupler. The BLDC motor was used as both a starter and a generator; it was powered to motor the engine and then switched to a programmable direct current (DC) electronic load to load the engine as a DC dynamometer once the engine was running. Instrumentation was applied to the engine and the test stand, including intake and exhaust thermocouples, a low-speed pressure transducer for exhaust pressure, an optical encoder for crankshaft position, a custom-built fuel scale, a hot-wire anemometer air mass flow system, and a cylinder pressure transducer. To acquire data from and control the test stand, a National Instruments CompacDAQ system was used in conjunction with LabVIEW virtual instruments (VIs) developed for the specific test stand hardware. Finally, an AVL IndiModul system was used to capture cylinder pressure data. By considering the objectives of the anticipated testing and carefully selecting hardware, a complete engine test stand was successfully assembled to test a micro, two-stroke engine.