Open the air inlet cam of the expansion machine to lengthen the opening time of the air inlet valve and increase the air inlet, that is, increase the expansion. However, in the start-up and adjustment stage of the oxygen generator, when the liquid oxygen level continues to rise and the refrigerating capacity is rich, when the refrigerating capacity needs to be reduced, the adjustment method of enlarging the intake cam of the expansion machine is also adopted.
Why does increasing the expansion capacity reduce the refrigerating capacity instead? This is because the refrigerating capacity of the expansion machine not only depends on the expansion capacity, but also is related to the unit refrigerating capacity of the expansion air. And the unit refrigerating capacity is related to the pressure and temperature before and after expansion. When the pressure in front of the machine decreases, the unit refrigerating capacity decreases. When the air inlet valve of the expansion machine is enlarged, the pressure of high pressure air will be reduced, the unit refrigerating capacity of the expansion machine will be reduced, and at the same time, the refrigerating capacity of throttling effect will also be reduced. Therefore, the total refrigerating capacity will be reduced instead. Therefore, the refrigerating capacity of the expansion machine cannot only depend on the opening degree of the intake cam. It also depends on the air pressure in front of the expander.
When the oxygen generator is started, the air throttle (section-1) has not been opened yet, while the pressure of piston air compressor is basically certain. Therefore, if the high pressure of the cam is stable under a certain opening degree, the compressed air has all passed through the expander. At this time, opening a large Cam can not increase the refrigerating capacity, instead, it will reduce the high pressure and reduce the refrigerating capacity. Therefore, when opening the large Cam, the high pressure should be kept at the highest allowable pressure, so as to produce the maximum refrigerating capacity.
During the step-down operation and reduction of refrigerating capacity, if the high pressure of normal operation is lower, the power consumption of the device will be reduced, so the refrigerating capacity of the expansion machine should be exerted as much as possible. When the cam is enlarged and the air intake of the expansion machine is increased, the efficiency of the expansion machine can be improved and more cold energy can be produced. Therefore, the opening degree of the cam is generally in the position of maximum air intake, and a small amount of cooling adjustment depends on changing the opening degree of the joint-1 valve to change the pressure of high pressure air.
