hello:
i want to understand the block diagram of the regulator type 65. Some unit (F9E MKV) had LVDT and the other not. The questions is: The is the effect of LVDT on regulator type 65 (I know this regulator for control flow).

And if I isolate to LVDT what happens?

Thanks for all

 

The LVDT feedback was added because the designers felt it would be necessary for stability.

Empirical data over a couple of decades revealed LVDT feedback wasn't necessary for stability. (Note that most GE-design Frame 5 and Frame 6B heavy duty gas turbines do not use LVDT feedback from the liquid fuel control element, particularly if that control element is a bypass valve.)

Cost-reduction efforts led to the elimination of from the LFBV (Liquid Fuel Bypass Valve) and the LVDT feedback from the regulator. This resulted in the need for a slightly different Moog servo-valve used in the systems with LVDT feedback versus those without LVDT feedback and a slightly different regulator gain as well, if I recall correctly.

The regulator used for liquid fuel flow is primarily a flow-rate regulator. If the Speedtronic uses a LFBV and regulator with LVDT feedback, you can't eliminate the flow divider feedback. You could try eliminating the LVDT feedback (by changing the regulator type) but then you would likely need to change the servo-valve as well as the regulator gain.

Many sites which had LFBVs with LVDT feedback and then purchased new units which came without LVDTs have actually paid to have GE add LVDT feedback (for indication purposes only).

And, no; I don't have any part numbers or any further information about the servo-valves and regulator gains used on the two different types of systems. That type of information should come from the packager of the unit.

If you want to understand the block diagram of the Type 65 regulator, you will see that the high-selected value of Liquid Fuel Flow Divider Feedback is compared to the liquid fuel flow-rate reference. If there is no difference, then the output of the summing junction is zero, which means the LFBV position doesn't need to be changed.

If there is an error between the feedback and the reference, then the LFBV position needs to be changed by the amount of the difference and that amount is compared to the LVDT feedback. So, the LVDT feedback is really used for the "delta" (differential) when a change in fuel flow-rate must occur, and when no change is required then the LVDT adds some stability by keeping the valve position stable.

One has to remember that when the first Frame 7 was designed that the expected liquid fuel flow-rate was more than three times the flow-rate of the Frame 5, which was the largest GE-design heavy duty gas turbine at the time. The designers were understandably concerned about liquid fuel flow stability!