Step Load Vs Cylinder size/Charge pressure Vs Efficiency - Relation

[NickParker]

How the maximum achievable step load by the diesel engine generator is dependent on the engine/cylinder size and charge pressure?
If high efficiency is required, the the maximum step load to be reduced- Why?

 

[TugboatEng]

Big engines with big turbos operating at high charge pressures require time to spool up the turbocharger. Engines generally have fuel rate limits based on manifold pressure nowadays.

Caterpillar has a new 3516 coming to market that is rated at 3MW and is capable of taking a 100% step. That engine is quite small for the power output. It uses lots of smaller turbochargers, 4 of them.

 

[altered image]

Step load is a mis-fire by definition.
Slow down step load and efficiency goes up.

FLYWHEEL

 

[Lou Scannon]

Big engines with big turbos operating at high charge pressures require time to spool up the turbocharger. Engines generally have fuel rate limits based on manifold pressure nowadays.

Caterpillar has a new 3516 coming to market that is rated at 3MW and is capable of taking a 100% step. That engine is quite small for the power output. It uses lots of smaller turbochargers, 4 of them.

For that power density, I assume the 100% step load capability is when fully warmed up, not from a cold start, NFPA 52 style.

 

[TugboatEng]

It does meet NFPA 110. I'm not very familiar with NFPA, I only know of it.

I do know that these engines will take any load provided they are at rated speed. They don't need to be at full operating temperature.

On the subject of flywheels, that's not always a benefit in this case. A heavy mass will decelerate less during the block load but the engine has less ability to accelerate the flywheel than the generator has to load it so the heavy flywheel delays the recovery of normal operating speed.

 

[Lou Scannon]

My bad, NFPA 110
That's very interesting. Do you have a link where this is claimed or demonstrated? (the step load capability, not flywheel effect)

 

[altered image]

It does meet NFPA 110. I'm not very familiar with NFPA, I only know of it.

I do know that these engines will take any load provided they are at rated speed. They don't need to be at full operating temperature.

On the subject of flywheels, that's not always a benefit in this case. A heavy mass will decelerate less during the block load but the engine has less ability to accelerate the flywheel than the generator has to load it so the heavy flywheel delays the recovery of normal operating speed.

Yes of course, but question was asked about efficiency as to fast vs. slow slew to load.

 

[Lou Scannon]

The OP's question was not phrased very clearly. I think Tug and I both read it the same way: the first sentence was talking about power density, so we interpreted the final question to be talking about efficiency meaning efficient use of the displacement, i.e. power density also. In that context, Tug's answer was spot on.