What is the nature of the load variation in a reciprocating compressor unloader?

The number of open air valves varies~~~

There are four air valves at our entrance; what’s the difference between 100% and 0?

At 0 load, it doesn’t know how to operate; at 50 load, the two air valves on the axis side move, and at 100 load, the outer air valves continue to move – at this point all four air valves are in operation~~~

50% of the axial air valves operate, and 100% of all air valves operate to perform work!

With different amounts of air inhaled, less gas is compressed per compression cycle of the compressor, resulting in less work done

First, let’s talk about the principle of the unloader, and then address the loading issue. During normal operation of the reciprocating machine, the intake valve opens when the cylinder draws in air, while the exhaust valve closes ； When the cylinder compresses and expels exhaust, the inlet valve closes, and as the pressure in the cylinder increases, the outlet valve opens. Unloading means that, when the cylinder is compressed, a unloader is used to force the inlet valve to open; as a result, the medium drawn in through the inlet valve is pushed back out through it again, which means no work is done in this process. 0%, 50%, and 100% represent stepped unloading; currently, stepless unloading is also commonly used, allowing adjustment from 10% to 100%. We can discuss stepless unloading if there’s a chance. It is said that there are different levels of operation; currently, double-acting cylinders are generally used for power generation. In the case of a cylinder with 4 valves, there are 2 valves at each end of the cylinder, for a total of 4 valves. When none of the unloaders are in use, all 4 valves function normally, representing 100% load. When the two unloaders at one end of the cylinder operate to force the inlet valves open, while the valves at the other end continue to function normally, the load is 50%. When all 4 unloaders operate simultaneously, the load is 0%.

I forgot to mention a common misconception among those who are new to this topic: the percentages of 100%, 50%, and 0% refer to the load on the compressor’s working medium, that is, the load required for the compressor to perform its function. They do not apply to the unloader, as the unloader is used for relieving pressure during operation; it does not function at 100% load and operates at full capacity at 0% load.

Can it be understood in this way: assuming there are four air valves at the inlet, at 50% load two of these valves open and close normally, while the other two open and close under the action of the unloader?

The two air valves open and close normally, while the two air valves remain open under the action of the unloader. In the normal switching mode, the cylinder on the side where the switch is in the closed position does work, while the cylinder on the side where the switch is in the open position does not do work. Under normal conditions, the piston performs work both when it pushes and when it pulls; at 50%, it only performs work either when pushing or when pulling, but not when moving in the opposite direction.

Oh oh! Based on what is the load of the unloader adjusted during normal production? Is it the exhaust temperature? If the exhaust temperature is fine, should the load be increased as much as possible?