Why does the secondary oil pressure increase as the turbine speed rises?
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I would like to ask the experts: Why does the secondary oil pressure increase when the turbine speed rises?
To increase the rotational speed, it is necessary to open the control steam valve wider; the secondary oil pressure corresponding to the opening degree of this valve ranges from 0.15 to 0.45 MPa, while the percentage range is from 0% to 100%.
1. The set value for the opening degree of the turbine control valve, as output by the governor, increases; in other words, the 4-20mA current signal sent to the electro-hydraulic converter increases； 2. The electro-hydraulic converter receives the current signal (4-20mA, which indicates the valve opening degree) provided by the governor, and controls the secondary oil pressure through throttling ； 3. The servo mechanism (hydraulic cylinder + throttle valve + feedback linkage) receives secondary hydraulic pressure to drive and adjust the opening degree of the turbine control valve ； 4. When the throttle valve of the turbine is opened wider, more steam enters the turbine, and its output power increases ； The correspondence is as above. There is no direct relationship between the turbine speed and the secondary oil pressure.
The speed controller sends a signal to the electro-hydraulic converter, which generates a proportional secondary oil pressure that acts on the throttle valve; this in turn causes the hydraulic actuator to move, resulting in the speed control valve opening wider
Increase the secondary oil pressure to open the throttle valve wider. . . . . . . . .
The secondary oil pressure corresponds to the opening degree of the control valve; as the speed of the turbine increases, the secondary oil pressure also has to rise in order to increase the opening degree of the control valve.
The reply on the 3rd floor was already very accurate. Put simply, the secondary oil pressure is what drives the opening of the main steam valve.
As the turbine speed increases, the secondary oil pressure should decrease, right? It is only when the secondary oil pressure drops that the regulation can be shut off.
There’s no need to go into too much detail regarding the principle: the opening degree of the main steam valve is the result of a balance between the secondary oil pressure and the force exerted by the spring in the main steam valve. If one wants to increase the opening degree of the valve, it is necessary to increase the compression of the spring; likewise, the pressure supplied by the secondary oil to the cylinder must also be increased. Otherwise, how can one compress the spring in the main steam valve in order to increase its opening degree?