Study on the reliability of paddle-wheel tumble flow meters for high-speed engines

Paddle-wheels embedded in either L-shaped or T-shaped dummy cylinders are commonly used to measure the in-cylinder tumble motion intensity supplied by a specific engine head design at the steady-state discharge-flow bench. A few years ago, the authors designed a new in-cylinder flow meter that enables the measurement of tumble intensity without the need for L- or T-junctions. The in-cylinder flow meter demonstrated the capability: to capture different intensities of tumble motion resulting from different engine head design; to provide data well correlated with the CFD simulation of experiments. The aim of this paper is to assess the reliability of the data obtained by this new paddle-wheel device, considering that the lack of the piston crown simulacrum could strongly affect the onset and intensity of tumble flow measured at the steady-state flow-bench. To this aim, in-cylinder motion of two high-speed engine heads, as measured by the new paddle-wheel device, are compared with data from the literature, which was collected using traditional L- or T-junction tumble meters. In addition, the results of CFD predictions for the angular momentum acting on three different T-shaped tumble meters applied on one of the two engine heads subject of the tests are studied to explain the differences in trends and values of tumble intensity data obtained by using either the new or the traditional paddle-wheel devices. Within the several limitations affecting such category of tumble meters, the results demonstrate the reliability of the new device.