Extensive experimental studies are performed using force sensors to measure actuating forces of nozzle ring devices of variable nozzle turbines. Torques from pneumatic action applied onto axles of nozzle vanes have been calculated. Test results obtained through repeated experiments are quite congruent,confirming the effectiveness of this simple method. Results have indicated that,with a fixed opening angle of guide vane,pneumatic torque increases with mass flow of air jet in the turbine; moreover,under the same mass flow rate,torque decreases with reducing opening angle,even possibly change direction down to negative. The results have also provided a modus operandi for designing nozzle-adjusting devices as well as validation data for numerical study on changes of pneumatic torque onto guide vanes under full engine operating conditions.
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