Vibration Reduction in Indigenous Wankel Rotary Combustion Engine with Structured Layer Damping

Rotary engines are simpler in design and operation compared to the gas turbines. Rotary engines propel many monoplanes, power hang gliders, and unmanned aerial vehicles (UAV). In an indigenization effort, a 65 hp Wankel rotary combustion engine (WRCE) was successfully developed in the country for a wheeled version of Nishant UAV. As a part of the testing and certification process, three engines were required to be tested in the test bed for a stipulated number of hours. The engine was mounted in the test bed on two cantilever bolts in horizontal and two in the vertical direction with equi-frequency anti-shock mounts. During testing without the alternator, it was observed that the vibrations are higher with 1X amplitude of 24 g. To identify the source of vibration, a detailed modal analysis was carried out. Impact test data showed the existence of dominating frequency around 138 Hz. To reduce the vibrations, the engine mount is modified suitably, and structured layer damping is introduced between the engine mount and support structure. This modification resulted in increased damping leading to vibration reduction to the acceptable level. Testing of Wankel engine with alternator up to the required speed was completed successfully using the structured layer damping method.