Grate Shake Testing 20100621


A run was conducted to test potential mechanical grate shake mechanisms for the V4 GEK and Power Pallet. A crank and linkage based shaker and a vibratory shaker were tested. The V4 GEK uses a horizontal grate shaking mechanism. Tests with a rotary grate shaking mechanism over summer 2009 with an automated V3 rotary grate showed clear increases in pressure ratio after shaking, a mechanism that could achieve via horizontal grate motion this was desired.

Automated rotary grate shaking mechanism for V3 GEK


Both the vibratory and crank-based horizontal grate shaking mechanisms tests were shown to be effective: Pressure ratio spikes were clearly seen for crank-based (10-60 mins) and vibratory (70-160 mins) methods. The crank-based method seemed to be less effective per unit time (30 sec every 5 mins) showing a consistent drop in pressure ratio over the Phase 1 test. The vibratory method appeared to be more effective per unit time, rapidly reaching an equilibrium pressure ratio of ~0.4 during the Phase 1 test. Phase 2 of the test was intended to measure duty cycle to achieve a pressure ratio setpoint (initially 0.3, then 0.4). The code used did not provide appropriate data to determine required grate shake duty cycle, but did show this method can maintain a consistent pressure ratio. Revised code could provide information that would be useful in the long term evaluation of grate shaking mechanisms and fuel interactions affecting reduction bell packing.



Hopper refilled w/out shutdown

Hopper was refilled w/ genset running. T_tred temps were seen to drop rapidly while filling, but no other issues were seen.

Pressure Ratio

A pressure ratio of 0.4 appeared to be around the upper limit for this run on walnut shells. During Phase 2, grate shake duty cycle was in the 50-100% range to maintain a pressure ratio of 0.4



Vibration shake -

     small eccentric - rpm was ~1300 RPM with ~1/8" stroke (char in place) (two wire fan motor)

     large eccentric

Prototype vibratory shaker

Crank based shake - 1/2" stroke at 50 rpm (Wondermotor)

Prototype crank-based shaker that was tested


Test methods

Phase 1

Test of crank-based and vibration-based (small eccentric) grate shake at 30 s periods every 5 minutes.

Phase 2

Test of crank-based and vibration-based grate shake, shake when P_ratio below 0.4 (initially 0.3)

(this condition was checked at 100 Hz. The grate on variable was set to true if the condition was true any time over the 1 second sample period. The intent of Phase 2 was to check the duty cycle of each method, but the above made this test not helpful. This test could be made useful by smoothing of inputs/response to generator longing active/inactive grate periods and thus better grate shake duty cycle measurement)


Power Monitoring

Power monitoring circuits were not brought back fully, one legs amperage was measured. Consumption was generally placed on that leg, genset voltage was kept around 110V.



Pressure Ratio



Grate mechanism on when graph when black