Or the implication may be that Burke is not able to convert as great percentage of its turbines' power to the actual propeller. Perhaps converting little less than half of it. While IEP may be able to convert almost all of the power created into physical power turning the propeller.
055 DDG Large Destroyer Thread
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Jura The idiot
General
I now looked back at two or three pages, and the thing is people threw in numbers in MW without LOL! even giving
bhp or shp after their number
(in the years of the USN battleships with electric drive, there was an additional difference in the way how "shp" is available to shafts/propellers:
a ship with geared turbines would need more "shp" to perform in the same way as a ship with electric drive turbines EDIT don't want to write a wall of text)
I mean it's really amateurish not to be distinguishing this type of stuff, LOL saying just like 'they installed whatever MW' common
bhp or shp after their number
(in the years of the USN battleships with electric drive, there was an additional difference in the way how "shp" is available to shafts/propellers:
a ship with geared turbines would need more "shp" to perform in the same way as a ship with electric drive turbines EDIT don't want to write a wall of text)
I mean it's really amateurish not to be distinguishing this type of stuff, LOL saying just like 'they installed whatever MW' common
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Exactly.
IEPS is actually more efficient than direct drive.
In direct drive, the drive train is gas turbine (brake power) -> reduction gear (shaft power) -> drive shaft -> propeller.
In IEPS, it is gas turbine (brake power)-> electrical generator -> electrical motor (shaft power) -> drive shaft -> propeller.
The reduction gear brings in 2-5% loss in case of diesel engine which has much lower RPM than gas turbine. More stages in the gear box will be needed to reduce the RPM in gas turbine setup, more stages means more loss. 5% is the rough number for diesel setup, it may be 10% loss in case of gas turbine. The RPM must be bring down to drive the propeller.
Electrical generator and motor combo can attain as high as more than 95% efficiency (<=5% loss). Electrical motor can run at very low RPM without loosing torque, an character that neither GT nor Diesel -setup can ever match. A daily life example is that electrical cars with same power rating always out-perform cars of internal combustion engine in acceleration (high torque).
So from the primary mover to the propeller, IEPS is more efficient than direct drive. In turn, Diesel setup is more efficient than gas turbine.
Besides that efficiency, lower RPM means higher efficiency (propeller -> forward motion).
Let's take these in the calculation (not accurate, just an idea):
Arleigh Burke has 4 X 19.75 MW (brake), it becomes 4 X 17.75 MW (shaft) = 71.1 MW (shaft).
Type 45 has 2 X 21.5 MW (brake), it becomes 2 X 20.425 MW (shaft) = 40.85 MW (shaft). Brake 54.4% to Shaft 57.45% of Arleigh burke.
Now to your question of Type-45 seemingly underpowered than Arleigh Burke, the draft of Arleigh is 9 meters will Type-45 is only 7.3 meters, this means Arleigh need much more power to reach the same speed because there is more water for it to push away than Type-45. This is only about maintaining the top speed.
In case of acceleration (may be even more important than top speed), due to the advantage of electrical drive, a lower rated electrical motor can out perform a higher rated GT set because Arleigh's propeller runs at a much higher RPM which is much lower in efficiency in converting its rotating power to forward power. It is similar to a high powered car trying to start from stand-still on a muddy ground when the wheels just spin wildly without moving anywhere, while a low powered car turning the wheel slowly without slipping.
Arleigh would not need that much power if it uses IEPS to maintain its current performance. In a way, one can say Arleigh is over powered. I think 055 was called "over powered" in this thread for the same reason.
I think the matter is a little bit complicated than yes-no.
Type 45's IEPS promised some kind of graceful shut down capability, but it does not work in the situation when the power grid collapsed. That indicates that either there is no backup energy storage system onboard, or it is inadequate for that situation. When the GT under perform in the hot weather, the output electricity reduces, but the load does not, it is like short circuiting at home when people put up excessive power drain that burns wires or cause the circuit breaker to kick in, abruptly turning off lamp and computer etc.
The whole system of Type 45 will work very well in northern Atlantic, both the GT and the electric grid. RN's decision body should be (partially) blamed for ignoring the extreme working condition that Type 45 is supposed to work. I remember reading that RN was warned by the builder for that.
In the end, it is the over all design and integration failure, all three parties (RN, GT and Electrical system) are partially responsible, but mostly RN because the other two meet their specifications (albeit flawed ones by RN).
From what I understand that the issue is with the intercooler recuperator in the GT, which fails in hot conditions. That leads to the lack of graceful shut down.
I think the primary fault lies with the GTs, and possibly the RN for not designing the ship with additional diesels to begin with in the case of GT shutdown. But it isn't related to the IEPS configuration of the ship itself, rather issues with the powerplants that supply the IEPS, if that makes sense.
Yes, the GT was unable to operate in a hot weather. The intercooler is not up to the task.
However, the lack of graceful shut down is separate issue totally in the hand of electrical system. It was supposed to (as in Ma Weiming's design architecture) sustain the situation when GT output decreases by power storage system (flywheel, battery etc. like UPS), during that short period, electrical consumers are shut down gracefully, start from non-essential ones (air conditioning, accommodation lightings etc.). Before the storage system dries up, the total load should have been brought to the point that whatever left from the GT is enough to sustain the remaining critical load. At any time, the drop of output should not lead to a short-circuiting situation that can physically damage the equipment. It seems that has failed on Type 45 that lead to repair.
Of course, one can also argue that the collapse of output of GT was so drastic and rapid that exceeded the storage system's designed capacity. It is a matter of laying the blame, or who is to do more for the whole. Both sides would be right and wrong at the same time.
So at the end, the true responsible party is the architect of the whole system, not really the subsystems. And by saying this, I think Type 45's IEPS is flawed. And I mean that the powerplant is an integral part of IEPS (regardless the meaning of the abbreviation), something whose performance envelope determines the whole system. For example, the one basic driving consideration in Ma Weiming's design was about the characters of Chinese GT and Diesel engines (lack of), and the outcome was his choice of DC grid to remove the trouble of gearing up and down to match the RPM/Frequency.
One more thing, Type 45 IEPS use AC scheme which critically depends on the stable RPM of the primary mover. If GT drops speed, the gearbox need to change to maintain the frequency. If the drop is too sudden, there can be out of sync spike of current that cause physically damage. The IEPS is tasked to prevent that. But that is a challenging task for AC grid, while piece of cake for DC grid. Once again, this IEPS is weak by nature (not faulty by design). Another reason that Ma choose DC scheme.
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asif iqbal
Lieutenant General
Too many opened ended discussions on SDF recently
Is Type 055 back yet ?
Is Type 055 back yet ?
I don't inherently disagree with what you wrote, however I'd like to refer back to the original point of contention that spurred this discussion, which were two posts that suggested an IEPS configuration was "less efficient" than a conventional arrangement of gas turbines to shafts via reduction gears and the idea that IEPS would somehow be unable to achieve that top speed.
https://www.sinodefenceforum.com/type-055-ddg-large-destroyer-thread.t6480/page-606#post-521822
The reason why Type 45 is brought in, IMO, is to demonstrate that when IEPS configuration is working, that it is able to propel the Type 45 to its intended speeds and at a satisfactory level of efficiency.
Issues with the Type 45's IEPS and in particular the powerplants driving the IEPS do of course exist, however that is largely immaterial to the original area of disagreement, which was whether IEPS could allow a ship to reach its intended top speeds and/or do so efficiently.
My point was that it would be impossible to achieve the same top speed if you halved the amount of GTs, as someone suggested, so you can fit the magic number of VLS. Even with IEPS the efficiency gain is not going to be the 50% required. Gearboxes, even high speed ones, are not that inefficient. The other point was that IEPS is not physically smaller than a traditional configuration (there are some reports of the opposite concerning the Zumwalt class). So you won't be able to fit everyones favorite number of VLS just by going over to IEPS and keeping everything else the same.
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