At which rate, water will inject into turbine in liquid fuel gas turbine on pre selected and BASE LOAD? in Kg/sec and also plz let me know what is the back-end logic/scheme on which turbine controller send a command to water injection pump for start?

 

instrumentationautomation,

GE have been mucking with water injection schemes and logic the past few years, so this is a general statement that you will have to investigate by examining the sequencing (Mark V) or application code (Mark VI or Mark VIe) running in the Speedtronic panel of the turbine(s) in question.

Water injection is usually started when the fuel flow-rate reaches a certain level, called the "enabling" fuel flow-rate. And, the rate at which water is injected is determined by the fuel flow-rate. There are other posts on control.com which describe the typical water injection flow-rate reference equation.

Water injection is usually based on fuel flow-rate, because emissions are also a function of fuel flow-rate (when operating in diffusion flame mode). So, as fuel flow-rate increases and flame temperature increases so will the emissions. And the point at which water injection is enabled (started) is chosen to make sure that flame is stable and emissions meet requirement/guarantee.

When you write to forums like this it's most helpful if you provide some information about the turbine and control system at your site--while all GE Frame 9E heavy duty gas turbines compress air and burn fuel and produce power, they can have very different auxiliaries, fuels, and combustion systems (conventional or DLN)--and different Speedtronic turbine control systems, which may or may make a difference but could and therefore is important. Some turbines use a water injection pump that runs at a constant speed with a variable control valve to control flow, and others use a variable speed pump motor to control flow. You see your turbine(s) every day, we don't. This site doesn't use avatars, where people can tell us about their site and their equipment once and it's available to anyone, anytime to refer to--so the more information you can tell us the better and more concise our response(s) will be.

In general the name of the logic signal that starts/enables water injection is L4WN. Often the name of the logic signal that starts/stops the water injection pump is L4WN1X. Usually, there is a target on the HMI for the operator to enable water injection, and this can be done at any time during a turbine start. Once enabled by the HMI target, when the fuel flow-rate reaches the enabling setpoint the system will start injecting water at a rate proportional to fuel flow-rate.

Hope this helps!