4lk fuel consumption

[crossley]

Have been playing about with a calibrated fuel measuring flask for a while now, it's really just a little two pint tank with a glass tube on one side marked in 1/16 pint divisions. Results so far are between 1 9/16 to 1 5/8 pints per hour, over timed 1 hour runs, with fully charged batteries, at normal cruising speeds. This bears out the average of a litre an hour, for most narrowboats, this being a little less, at around 0.9 litres per hour. This is for a 65 foot trad, driving  24x19 prop through 2:1 reduction. Draft 30" alternator load minimal, 5-6 amps, lighting load. Probably not far short of what a modern engine can achieve. The above figures were measured over time, not distance travelled, at a sensible cruising speed. 

[Sea Dog]

That's really quite impressive. My modern Beta 43 typically returns around 1.25 to 1.5 litres per hour going by litres required to refill the tank divided by engine hours since last fill. Usually there's a bit of river in there, a fair amount of idling in locks, almost always recharging the batteries after an overnight discharge and very occasionally a bit of static charging, though I avoid that if at all possible. Some goes through the Eberspacher too though. Certainly there doesn't seem to be a huge price to pay in fuel for running a 'more interesting' engine.

[Dalslandia]

the key is the propeller, it is not the Engine that drive the boat forward it is the propeller, or horse.

increase the size of the propeller and efficiency goes up with 0.6% per 1% increase in propeller size, so if we go from a 18" diameter to a 24" it will be 20% more efficient.

slow speeds also increase milage,  as Power needed goes up with 3th Power with speed, doing 2.9 miles per hour instead of 3.33 average reduce fuel use with 50%

[dmr]

27 minutes ago, Sea Dog said:

That's really quite impressive. My modern Beta 43 typically returns around 1.25 to 1.5 litres per hour going by litres required to refill the tank divided by engine hours since last fill. Usually there's a bit of river in there, a fair amount of idling in locks, almost always recharging the batteries after an overnight discharge and very occasionally a bit of static charging, though I avoid that if at all possible. Some goes through the Eberspacher too though. Certainly there doesn't seem to be a huge price to pay in fuel for running a 'more interesting' engine.

In fact those old slow revving engines actually return better fuel consumption, but as said above, the bigger prop that they usually run will be part of this.

Despite modern advances in engineering 2 or 3 slow moving pistons are likely to produce less friction than 4 fast ones.

..............Dave

[crossley]

This was an attempt at actually measuring fuel consumed whilst moving, against a stopwatch. Once you add in other variables, like river currents, waiting at lock landings, battery charging etc, the results would be different again, more in line with your results. Remember I'm only measuring over one hour under optimum conditions, I.e  engine  fully warmed up, very little parasitic loads etc. 

[cuthound]

When I was working over the years I must have witnessed hundress of standby generator sets being commissioned, from 10kVA up to 3MVA. Each had their fuel consumption measured at 0%, 25%, 50%, 75% and 100% load for 1 hour.

Irrespective of engine speed,  cylinder configuration and generator rating,  the fuel consupmtion was always around 0.285 litres per kW load per hour, + 5%.

[smileypete]

1 hour ago, cuthound said:

When I was working over the years I must have witnessed hundress of standby generator sets being commissioned, from 10kVA up to 3MVA. Each had their fuel consumption measured at 0%, 25%, 50%, 75% and 100% load for 1 hour.

Irrespective of engine speed,  cylinder configuration and generator rating,  the fuel consupmtion was always around 0.285 litres per kW load per hour, + 5%.

Considering diesel is about 10kWh/l, that works out 35% efficiency for the engine and genset which seems about right.

Edited November 12, 2017 by smileypete