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Project Objectives

    The initial objective is to build a working engine dynamometer test bed that will measure an engines output torque and rpm while keeping safety a top priority. The water brake dyno must be able to measure a maximum of 120 hp, and perform a sweep of engine rpm from 3,000-16,000 rpm. This must be performed with an accuracy of +/- 0.5 hp with a repeatability of +/- 0.1 hp at a sustained load of 50% duty cycle for one minute. The goal is to achieve the same results to that of a previous professional dyno test that the team has, as shown on the top right.

Final Design

    The final design of the water brake engine dynamometer is a custom build steel frame on casters with a mounted sub-frame for the engine and a custom manufactured aluminum water brake. Some key components include: a water brake, pump, radiator, reservoir, engine mounting, and frame. Five subframes make up the overall structure of the system. The subframes are connected at specific locations with 1/4” thick L-brackets. The engine subframe specifically is connected with U-bolts to allow for easy removal. The frame is strong and relatively lightweight for this mobile application and will provide a long lasting study platform for testing many years into the future.  

     Since the water brake must absorb all of the power that is put out by the engine that is being tested, it is the most critical component of the dynamometer system. Designing the water brake was thus an iterative process which took several weeks to complete. To significantly speed up the design process of the water brake unit, the design was based on a currently existing water brake: the XS-111 which is manufactured and sold by Stuska Dynamometer. A water brake was manufactured with functional requirements to absorb and dissipate 90 kW of power continuously, and be able to rotate at a minimum of 6000 rpm. The final design of the water brake assembly is shown above along with an exploded view of the water brake itself. 

    This dynamometer is operated manually by opening or closing the inlet valve to the absorber system, thereby restricting the flow of water to the rotor blades and causing less load on the engine. At a given set throttle position, the engine output speed will vary between idle and redline depending on how open the inlet flow valve to the dynamometer is. With the valve in a completely open state, the engine will stall as it has more load on it than the engine can produce. Measurements of engine power require shaft speed as well as torque produced by the absorber system. To measure shaft speed, a Hall Effect sensor is implemented on the output shaft of the engine. For torque, a load cell is mounted on rod ends at a specific distance away from the axis of rotation.

    The data acquisition electrical circuit includes a myRIO (National Instruments) data acquisition system which was donated to the project by National Instruments. Connected to the data acquisition system, are four waterproof thermistors, a load cell and amplifier combination, and a Hall-effect shaft speed sensor. The fan power circuit includes a 12V, 360W power supply to power all four 80W radiator fans as well as the data acquisition circuit. The pump is powered directly off of mains power voltage as it includes it own motor controller. The engine power circuit includes a Yamaha FZ6R battery to start the engine as well as provide power for the engine harness. All frame components will be grounded to reduce stray EMI, and an extension cord is run from where testing is done to the nearest building. For increased safety there is also an emergency stop button located on the operators side.

 Exploded view of the water brake design