Flownex Modeling for Combined Cycle Power Plant - Part 2

Flownex Modeling for Combined Cycle Power Plant - 2 Hello everyone, this is Mohsen from the Ozen Engineering team. This is the second part of the video about using Flownex software for modeling power plants.

In the first part, I used the model available from the Flownex team for the combined cycle power plant, which is a combination of a gas turbine and a steam turbine together, and so we have more efficiency and better overall power generation for the power plant.

In part 1, I already showed you how to use this model or how to run it and what are the main parts and main systems of the power plant cycle.

In this part, I just want to show you how to change the mass flow rate of the fuel that is used in the cycle, and also how we can consider different weather conditions, ambient conditions for the power plant, and evaluate the effect of these two on the production of the power cycle.

In the next part of this video, I want to show you how to change the fuel mass flow rate for the power plant. Basically, we want to see its effect on the efficiency and on the total output power. This is the model that I have; I just initialize it again. Let's run it for steady-state condition.

And again, we see a non-zero value for the energy source; we don't want to have any magnitude for the energy source. I'm running the designer, and I will show you then how to change this mass flow rate for this fuel, which is natural gas here.

Now, this is the designer running; okay, almost zero, so there is no need for the input of the energy source. Now, let's work on the mass flow rate of the natural gas. We go here to the configuration, and we can define some actions that are based on time.

For example, we can say that from when it starts, what is changing, what parameters. Here we have some set of values for the pressure and the Q value for the boiler. If you come here, you can see that from time 0.2 seconds, for example, we can see that, and this one is for the pressure, okay?

And this one is for the quality. So, this one is the one that I want to see, that fuel mass source. It is said that after half a second, start to change this fuel inlet, this is the boundary condition, this source for the mass.

Initially, it is set at 4, and we use this value for the steady-state condition. We want to change it in a way that, okay, that now we can see it is a function of time. It is a constant which is 4, and after that, it is like a linear change in the magnitude in terms of time for the mass flow rate.

I don't want to go beyond 5 kilograms per second. I want more than 5 kilograms per second. So, this is the action that I have. So when I go back to the model and when I start this transient simulation, you will see that this value starts changing after half a second.

We didn't have this before when I ran the transient simulation. Let's see. Okay, time is 0. 4. Now we should see changes in the magnitude of the mass value rate. The output power is capped at 5 kg per second. The air intake is also changing. The magnitude of the air coming in.

You see the change in the output power for the gas turbine. And also the steam turbine. Let's see how much we will see. So, the magnitude is that right now for the total value of the power; it is 83.8 megawatts, and the overall efficiency for this cycle for this condition is 30.6%.

Let's see, now it is 6 seconds; we see that, so again, you see that the power for the gas station is almost constant. Okay, 44.3 something, 44.3, but the magnitude for the steam turbine is changing.

Let's see, 18 megawatts; you can see that in the boiler system, which is heat recovery for steam generation. We see a little bit of change in the temperatures. It used to be 700 something, 600 something degrees Celsius, and this is 410 something.

Now you can see that we have a higher temperature because of the higher inputs for the fuel. And after combustion, the input gives more power to the turbine. The turbine production for sure will increase.

Let's see what time it is; 18 seconds, we're getting close to the end for this transient simulation.

Yeah, you see that constant output power almost for the gas turbine, but the steam turbine, the output for the steam turbine, this power is increasing, about 19.67 somethings, okay, and if we check that, yeah, 19.7, so we are seeing that increase in the efficiency and the total power due to the increase in the mass flow rate, and this is the boundary condition.

And that for this one with the action, we change the magnitude of this mass source from 4 up to 5 kilograms per second for this boundary condition. So, as you can see, we have zero input for the zero magnitude for the heat source for the drum for the boiler, which is good.

So, increasing in the efficiency and total output power when we have more fuel gas. Let's see that if we increase it more from 5 kg to 6 kg, what happens? So, I'll go and change the action here and see what happens.

Okay, we go back to the initial condition, 4 kg per second for the mass flow rate of the fuel. Go to configuration, action setup, this is for the mass flow rate. I will change this maximum to 6; you can see that.

I change it to 6, so it means that the mass flow rate starts at 4 kg per second, and after half a second, it will start increasing up to 6 kg per second.

Okay, so I adjusted that action, go for the steady-state condition, again check the boiler drum negative energy source, go for the designer, run the designer to change the pressure here.

Here you can see the pressure of the drum, and you can see that it is changing gradually, and then we can go back to the energy source here and see that it is working.

So, let's see, yeah, I found the solution, so the solution converged, and if now you can check it, okay, you can see that almost zero, which is good for the energy source. Now, we can go and run the transient analysis.

Okay, 0.4, 0.5 seconds, and you can see that the mass flow rate of the gas starts increasing. 5, 5.2, 5.4, and 6. So, it does not go above, and you can check the exhaust temperature. It is much more than before.

As you can see, also here for the temperatures in the gas line and the exhaust line to the ambient, now it is 500 somethings. Okay, the output power is 58.1 for the gas turbine, and for the steam, it is 18. 1. And it is 8 seconds; the output power for the steam turbine is increasing, going up.

Let's wait until 20 seconds that it will finish the transient analysis. Now we are above 19, 19.5 for the power compared to 17 somethings that we had before. Maybe we go beyond 20, 20 megawatts from the same turbine.

But the power generation for the gas turbine is constant because we don't see any changes here anymore for the intake air and for the natural gas input. Thank you for watching. Okay, we are almost at the end. Let's see what the time is.

This is still increasing, 19.4 seconds, 19.6 seconds, 19.8 seconds, and 20 seconds. We are done. 21.9 MW for the power generation of the steam turbine.

The total output power is 97.6, but the overall efficiency dropped from 30.6 to now 30. 1. Now let's check the weather conditions and see that how these different weather conditions could affect the performance of the power generation cycle.

Okay, I haven't talked so far about this one, okay, that it is for air psychrometry. If you double-click, you can see that the inputs, okay, are site elevation, atmospheric temperature, and relative humidity.

This icon is for the raining day; it means that because of the specific relative humidity that you can see, we expect to see kind of weather for raining days. Let's double-click on that. It does the calculation from the psychrometry charts that we have.

You can see that here from these inputs, we can have some information about atmospheric data like ambient pressure, density, relative humidity, and dew point temperatures. And also results on the air composition based on the mass fraction or mole fraction.

So, I decrease the relative humidity and increase a little bit of elevation and also the temperature. So, we have new information from the atmospheric data. Let's see what is the effect of these changes on the performance of the power plant.

And this is the script, okay, that you can see that it takes the information from the psychrometry chart and does the calculation based on the information that we have for the parameters here as results, and you can see that what are the inputs, what are the outputs here.

So, go back to the model; these are the new information for the weather conditions, a little bit higher elevation, and also lower relative humidity. See what is the effect of this on the performance of the power plant.

First, run the steady-state condition, then run the designer to have zero energy source for the boiler by changing the pressure of the boiler drum. Almost zero, which is good. Now, for this new information from the weather condition, let's run the transient analysis.

So, the gas flow rate is kept at 6 kilograms per second. You can see that. Now, you can see the changing in the way that the power outlet from the gas turbine changed, the power output for the graph for the gas turbine; it is different from before. I will back when the solution is done.

About 10 seconds passed, we need to have it run until 20 seconds. The solution is done.

Okay, the power generation for the steam is 17.3; it used to be 17.5 in the previous weather conditions, and the power generation of the gas turbine now is 24. 2. It is a little bit better; it used to be 23. So, the total power generation used to be 63 in the reigning.

Let's do more changes to the weather condition and see what is the effect for that. So, let's change this to the elevation from the original amount to 1000. So, it is like really going up above the sea level. This one change it to 18, and lower relative humidity.

So, it is like an almost dry condition, depending on the weather, weather, and location, and other atmospheric conditions. We also need to change the configuration and change the limit minimum maximum to 2000 up to 30,000 for the boiler to get an answer or convey solution for the boiler.

Let's run the first new weather condition; let's go for weather, for the steady-state condition. I already ran it; run the designer. Okay, so let's see, almost zero, which is good that we have, and now let's run the transient. Go for the transient running.

Same mass flow rate for the gas, natural gas. I will back when the solution is done. The solution is done, 20 seconds. As you can see, the steam generation produces 18.9 MW, which is larger than before.

For example, 4 kg per second, the efficiency increases from 28.8 to 28.9 to 31.9%, and the same for the output power. And this is also the same scenario we are seeing that when we check it for 5 kg per second and 6 kg per second.

For 5 kg, the efficiency for this weather condition is 30.6%, increases to 30.9%, and then jumps to 31.9%, which is good.

And for the total power from 83.8 jumps to 84.6 and goes up to 87. 4. So, also, we see the summary of the effect of changing the mass flow rates for different weather conditions.

In this video, I showed you how to use the available model for the power plant for the combined cycle of the power plant from Flownex. Have to work with that and have to change the mass flow rate and see the effects on the performance of the power plant.

And also have to change the weather conditions and see the effects on the efficiency and the total power plant. Hopefully, you enjoyed this video. Thank you for watching. Please contact us at https://ozeninc.com/contact for more information.