Technology and Operations
This forum is for discussing technological & operational matters pertaining to U-boats.
Re: U-boat diesel fuel consumption
Posted by:
Theo Horsten
()
Date: August 24, 2006 09:39AM
Hi Jukka,
165g/hp/hr is the normal figure for a 4-stroke marine diesel, against 150-160g/hp/hr for a 2-stroke supercharged diesel.
But, as I said, it's a theoretical figure. An old book that I have, gives 160g/hp/hr for a 6 cilinder 2-stroke ship's diesel of 3600 hp at 90 rev/min against 170g/hp/hr for a 6 cilnder 4-stroke truck diesel of 113 hp at 2000 rev/min.
A device to measure fuel consumption of U-boat engines may have been possible, I doubt if it ever was used. Why should they? You don't need that accuracy for every day use. What's the use of knowing that the engine is using 168 instead of the specified 165g/hp/hr? What's the diffence in consumption in 24 hours if your running at half speed or less? Maybe 40 liters? It's more important to know how much you have left in your fueltanks and measuring that on any ship with some accuracy is difficult enough already.
Of all the 40+ diesels I've ever sailed with, only one had a flow meter between the day tank and the fuel pump, but like I said before: it didn't measure the surplus fuel that came back from the pump and the injectors to the day tank so the figure it gave, was always too high. This was on a new tug for Aramco with a big caterpillar engine. They were just starting experimenting then with electronic measuring of engine performance and writing the results to a computer.
Nowadays they measure everything very accurate, bot not in the U-boat days.
I'm not familiar with the injection of gasoline in aircraft engines, so I have no idea what kind of fuel pumps they had in the days of the Juncker and if they had a return flow that had to be taken into account. I have no idea of the pressure with which gasoline is injected. A diesel fuel pump gives a pressure of 420 to 560 atm. or about 6200 to 8200 psi. MAN made its own fuel pumps, working on the same principle as the familiar Bosch fuel pumps.
I'm not an engineer, I'm strictly deckside, but in shipdelivery - taking somebody elses ship under its own power and with your own crew for a fixed price and at your own risk from A to B - fuelconsumption was the all important factor. That's where the money was made... or lost. Hence my interest in fuel consumption.
Best regards,
Theo
165g/hp/hr is the normal figure for a 4-stroke marine diesel, against 150-160g/hp/hr for a 2-stroke supercharged diesel.
But, as I said, it's a theoretical figure. An old book that I have, gives 160g/hp/hr for a 6 cilinder 2-stroke ship's diesel of 3600 hp at 90 rev/min against 170g/hp/hr for a 6 cilnder 4-stroke truck diesel of 113 hp at 2000 rev/min.
A device to measure fuel consumption of U-boat engines may have been possible, I doubt if it ever was used. Why should they? You don't need that accuracy for every day use. What's the use of knowing that the engine is using 168 instead of the specified 165g/hp/hr? What's the diffence in consumption in 24 hours if your running at half speed or less? Maybe 40 liters? It's more important to know how much you have left in your fueltanks and measuring that on any ship with some accuracy is difficult enough already.
Of all the 40+ diesels I've ever sailed with, only one had a flow meter between the day tank and the fuel pump, but like I said before: it didn't measure the surplus fuel that came back from the pump and the injectors to the day tank so the figure it gave, was always too high. This was on a new tug for Aramco with a big caterpillar engine. They were just starting experimenting then with electronic measuring of engine performance and writing the results to a computer.
Nowadays they measure everything very accurate, bot not in the U-boat days.
I'm not familiar with the injection of gasoline in aircraft engines, so I have no idea what kind of fuel pumps they had in the days of the Juncker and if they had a return flow that had to be taken into account. I have no idea of the pressure with which gasoline is injected. A diesel fuel pump gives a pressure of 420 to 560 atm. or about 6200 to 8200 psi. MAN made its own fuel pumps, working on the same principle as the familiar Bosch fuel pumps.
I'm not an engineer, I'm strictly deckside, but in shipdelivery - taking somebody elses ship under its own power and with your own crew for a fixed price and at your own risk from A to B - fuelconsumption was the all important factor. That's where the money was made... or lost. Hence my interest in fuel consumption.
Best regards,
Theo
