Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Help combined cycle real case question

Help combined cycle real case question

Help combined cycle real case question

In the start up of a combined power plant we have 3 hrsg working each at 100 mw and we are on a position control mode with bypass open . The turbine control valve is set at 98 MW load and the bypass pressure set point is 70 bar . my question is if we change the pressure of set point to 80 bar ( for example), the bypass will closes a little to achieve the new pressure , also the control valve will repond to this new change , but how about flow rates ? I know it will decrease in the path of bypass but will it increase in the path of turbine ? Does the increase of pressure will affects the flow rate from the boilers drums taking in consideration that the load of the gas turbines are constant ?

RE: Help combined cycle real case question

I didn't work Combine Cycle...But I have a question.

If the steam turbine is in "position control", would that mean the CVs are set XX% open in a high valve gate with any other governing. So why would you expect the CVs to respond to the BPVs and change in pressure

RE: Help combined cycle real case question

The CV will respond as we gave it the set point at 98 MW so when bypass closes , the flow rate decreases to the bypass and increases in the way to CV so it responds to any change to maintain the constant load that we give to it which is 98 MW

RE: Help combined cycle real case question

the flow rate decreases to the bypass and increases
Why? What is the reasoning behind this inference?

RE: Help combined cycle real case question

IF, the bypass valves (BPV) are controlling pressure and the pressure set point is increased, the BPV will throttle to raise pressure

IF, the control valves (CV) are at a set position, the increase in pressure will result in increased flow to the turbine and the generator output to increase whild CVs stay constant.

IF, the CVs are in power control, then either the sensed increase in flow to the turbine as a stage pressure or the increase in generator current will throttle the CVs to maintain the power set point.

depending on whether the control loops are propertional or intergal will determne if a small change in flow occures.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


White Paper - Effects of AIA Quick Guide to UL 489 or UL 1077
The function of a circuit breaker is to provide overload (thermal) and short-circuit (magnetic) protection to a circuit and its downstream components. A circuit breaker functions like an airbag in a car, protecting circuit components and people by tripping the circuit to interrupt the current flow if it detects a fault condition in the control system. Download Now
White Paper - Guide to Integrate Large-Format Additive
As with any new technology, getting into large-format 3D printing begins with investigation. The first question may be a simple one: what does “large-format” mean? For 3D printers, “large” is a relative term. Many extrusion-based (FFF) 3D printers are referred to as desktop machines, because they fit on table space. Some of these have very respectable build volumes – but when it comes to “large-format,” the machines will need their own dedicated floor space. Large-format 3D printers have significant build volumes and are most often found in professional settings, like manufacturing facilities and R&D centers. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close