Development of an Unequal Speed Co-axial Split-Rotor Thresher for Riceit

Abstract

During high moisture paddy threshing, the separation losses are generally large. However,while attempting to increase cropping intensity, it is often necessary to handle the moist paddy for threshing. Furthermore, in absence of adequate sunshine hours in wet season, crop can’t be dried to a desired moisture level before threshing. Keeping these requirements in mind, a co-axial split-rotor thresher was designed for threshing high moisture paddy. This paper describes design and testing of a stationary thresher with an unequal speed co-axial split-rotor for rice in Thailand. First rotor serves mainly the threshing operation, whereas, rotating at relatively higher speed, the second rotor does mainly the separation of rice grains from husk. Faster rotation of second rotor increases separation performance by increasing centrifugal force. Optimum speed for threshing rotor was considered to be 25 m/s (600 rpm with 0.8 m diameter threshing rotor) and a speed for separation rotor was evaluated. For better grain separation, speed of 30.2 m/s (720 rpm with 0.8 m separation rotor) was found optimum. With the material feeding rate of 0.6-1.8 kg/s, the developed co-axial split-rotor thresher reduced the separation losses to 0.7-1.3% at the separation rotor speed range of 27.4-33.5 m/s. By increasing this speed above 33.5 m/s (800 rpm) the grain damage was increased.