Planning Low Fuel Consumption DC Diesel Generator

1.4 lph is very close to the target.

The easiest modifications would be to the intake system or the exhaust system.

Maybe you could find a low restriction air cleaner for the intake.

Or, if you are easily meeting the target sound level, you might consider using a low restriction muffler in place of the standard muffler.

Maybe you could run a test with the air filter removed, to see if that helps lower fuel consumption.

Other modifications will be more difficult.

Also, more efficient alternators, or engines may be available, I don't know.

Good luck, keep us updated.

Thanks Lyn

in my long calculations, the alternator efficiency about 86%, and it is good enough for excitation alternator. the branded is china stamford

in my idea : i will try to ask to alternator manufacturer could they rise the efficiency, and i hope they can.

1> maybe from email quality grade, at stator and rotor wire

2> from bearing quality grade,

3> and maybe i will ask multi wire email wiring than single big wire at the coil wiring.

4> and etc

about air filter, i will try it to use 30KW diesel engine air filter, from kubota engine too, because i have a friend there. i think the air filter will have more much air flow area.

about the muffler, maybe i will redesign it, because the prototype it is still use standard muffler from the engine, and about sound level target, i think i will use double muffler but at low restriction type,

about the engine, the two cylinders diesel engine in my country the kubota branded was more easy to find it, ( worth price and worth quality i think ), for the other branded the candidate was at yanmar 2TNV70 and mitsubishi L2E, it is difficult to find in my country.

but, thanks for Your advice Lyn

regards

If you have the govenor/injector pump reset to run at the alternators spec speed of 1500rpm then you will find your improvement in fuel consumption and nvh.

You may be over fueling due to the fact the motor was factory set to be efficient at 3000rpm. See you service agent for the correct setting procedure.

Diesels run the most economic round the max. couple RPM. You might check that out. Kubota should have the fuel consumption at different loads and RPM.

Is the governor a standard one or a fixed RPM/couple one? As said before the injection pump - can do wonders if you adjust or change the regulator. You need a Kubota for generator. Not for e.g. a small sailboat drive, or car.

Both have a different governor.

Interesting blog.

I have a question, how can a 3 phase alternator have 4 poles? You wrote:-

alternator : custom spec 3 phase brush less alternator, 4 pole, 1500 Rpm, 8KVA,

Maybe I need to learn something new here, please explain....

Hello Andy,

A 1500 rpm alternator makes 25 mechanical turns a second.

If it only had one magnet on its rotor, a stationary coil on the frame would see first one north pole next to it, then one south pole half a revolution later.

If a passing north pole gives a positive voltage in the stator coil, then a passing south pole gives a negative voltage - it's that famous alternation!

But one + and one - repeated 25 times a second is only 25 cycles a second (Hz).

To get 50 Hz, there have to be magnets on the rotor in a "cross" (cruciform) formation. Then in one turn, the stator coil sees N-S-N-S poles - that is why it is called 4 pole rotor. Try a diagram, the § represents stator coil and • the shaft axis, rotate the rotor around • (ignore the ... - CR4 keeps deleting spaces!)

...N

S • S

...N

...§

The trick is to give the rotor a cross - shaped section and put a magnet or electromagnet winding in each limb. The CR4 entry will not let me put a | and an N on lines under the top S, and similar above bottom S, but I hope you get the idea. The magnets join e.g. S-N-S-N between adjacent limbs of the rotor (at first sight, it seems they cancel each other crosswise).

.....S

N-S•S-N

.....S

To get three phases, stator coils are put (and wired) in pairs 180 degrees apart, on opposite sides of the rotor. You make it with 3 pairs, spaced 120 degrees apart, one phase per pair.

A question for you, how do you get to give your latitude and longitude with an accuracy of 4 inches? Is the reference point the dog's basket?

Google earth........

GA

hello 67model

thanks for the explanation,

previously i would like to continue Your answer for Andy Germany

Andy Germany, please open en.wikipedia.org/wiki/alternator

and i think we are all clear about N=120 f /P,

N = is a rotational speed in Rpm,

f = is frequency,

P = is number of pole.

and between pole number and phase number there isn't any direct relationship, phase number goes to the way of wiring at the stator slot.

and pole number goes to the output frequency of alternator at given shaft speed from source.

You can make 1phase alternator with 2pole rotor, shaft speed 3000 Rpm and it will have frequency output 50Hz, if You have 4pole it will have 100Hz at same shaft speed,

You can make 3phase alternator with 2pole rotor, shaft speed at 3000Rpm and it will have frequency output 50Hz, if You have 4pole it will have 100Hz at same speed

You can make 3phase alternator with 4pole and to get 50Hz frequency You must turn the alternator shaft at 1500Rpm and if You turn at 3000Rpm it will have the frequency output at 100Hz. and 200Hz at 6000Rpm and go-on. ** sorry if i am wrong **

and 67model about Your explanations,

1500Rpm alternator it will okay to drive by 1800Rpm,

at my prototype, no load speed is 2100Rpm, ( sorry i am wrong, it is not 2200Rpm )

and at full load 3.12Kw (DC LOAD) the engine will goes to 1900Rpm.

it is for continuous duty, ok if follow Your calculation, maybe i am wrong at alternator efficiency calculation,

but the main thing is, can i reduce the fuel consumption again ?

what i must to do....? any part or any system or any modification again to do to reach more low fuel consumption.

at 3phase brushless alternator to get frequency 50 Hz, the alternator drive by engine speed 1500Rpm and for 60Hz electrical system the engine set at 1800Rpm.

and for no load speed, the initial speed setting usually + 5 % to 8% higher from rated speed and it is clear from tolerance frequency range 45 HZ to 55 Hz for 50 Hz system, and 54Hz to 66Hz for 60Hz system.

so 1900Rpm at full load it will have the frequency output 63 Hz it still save for alternator, and still at speed range initial setting at 60Hz system.

for 60Hz system the diesel engine speed usually sett at 1890Rpm,

so 1890Rpm to 1900Rpm i think it is closed enough.

and this dc diesel generator always use at 80% at rated power so the average engine speed not far from 1900 Rpm.

drop voltage at filter choke was 0.6VDC at 60Amp load.

i use 100,000 µF ( one hundred thousand micro farad ) capacitor filter.

yes 1.4 liters maybe it is not surprise, that's away i need advice what must i do to reduce full consumption again

i use 4pole alternator, because my engine speed work at 1900Rpm to 2100Rpm

closed to 1500Rpm alternator rather than to 2pole 3000Rpm alternator

my target was 1.2 liters each hours at 3,120Watt Dc Load, is this still reasonable...?

regards

Thanks, got it.

The problem was I was thinking of the stator at first, not the rotor. If the OP had said "rotor" poles, I would not have posted......misunderstanding of terminology only....

Saut Syafrudin,

If the generator is designed for 1500 rpm, to get same voltage it must have 26% more turns than if it ran at 1900 rpm.

There is a fixed space for stator copper, so wire cross section must be ~80% of that for 1900 rpm (and the wire length is 126%).

So you have a factor of 1.26/0.8 = 1.58 increase of resistance, which will increase generator loss dramatically at same load current. I expect, at this low voltage, resistive losses are a big part of generator loss. Less loss will be less temperature rise and lower hot resistance - reducing losses more.

I suggest you measure stator winding resistance cold and hot to check its temperature rise and get oscilloscope trace of winding current to calculate I²R loss. 3 phase rectifiers only conduct for 1/3 of cycle in each diode. Oscilloscope trace will also check effectiveness of filter inductor.

FETs in place of diodes can only remove part of ~4% of total loss - you require 20% improvement. Driving 6 x 4 = 24 FETs at the right time will be expensive!

I suggest you consult generator maker on how to best connect windings to have 3 phase output with just 3 terminal output and 6 diodes instead of 24.

67model

Another factor for 1500 rpm generator run at 1900 rpm.

Cooling fan of generator is designed adequate at 1500 rpm - but its power consumption increases on cube law of rotation speed.

So it uses twice the power at 1900 rpm.

Power and fuel is being wasted to over-cool the generator.

Dear 67model and all

thanks for your reply,

sorry, if i am not wrong, when we need same voltage at highest speed, so we can reduce the turns of coil.

or we can use more low turns and more diameters of wire to get same voltage but more amps.

because my prototype already almost fixed (but it still need optimizing final results),

so i will do next steep from the last configuration, although it not close for new system or new modifications.

1. i have ever try to use 3000 Rpm synchronous generator and drive at 1900Rpm to 2100Rpm, the final result 1.6 liters/hours, same KVA same rated voltage, and all same conditions, except generator
2. and if i use this 300Rpm generator, the generator was 2 pole rotor, the output ripple was more big than if i use 4 pole generator
   
3. because the smallest power of 3 phase 4 pole 1500Rpm generator was 8Kva/6.5Kw, so i use them. at custom spec, and i got 1.4 liters/hours
4. yes, the generator speed at no load was record 2100Rpm, and at full load was 1900Rpm, 3120Watts, 52VDC and 60Ampere

spec of synchronous generator i use now :

1. 4pole 1500Rpm to 1800Rpm,
2. 8Kva / 6.5Kw,
3. rated voltage 55 VAC X 6 Coils independent output, and reconnect-able end lead wire, totally there is 12 end lead wire,

if i am not wrong we must use the power of the diesel engine at range 75% t0 85%, to reach most efficient specific fuel consumption. so the engine speed 1900Rpm is the ideal speed.

because the DC load only 3120Watts, and the Diesel engine must two cylinders and water cooled, so the last configuration in my prototype was the most ideal form. but i still need to rise up the efficiency any more.

and two of my friend / colleague done same thing at they research, they got the best results at 1.6liters/hours .

different 0.2liters / hours, was different fuel consumption at 1,752 Liters / years.

and it is about 2,100 US $ each years.

if i could be reduce 0.2 liters / hours again from 1.4liters / hours , so i will have lowest 4,100 US $ annual cost at fuel only. if compare from my friend research/ my friend prototype.

yes 67model, about fan losses at higher Rpm i agree with You, but it is the consequence.

frankly, 1.4liters / hours was the best results in my country at this present, at the last estimated mass product price of the prototype.

and because my customer still ask me : Can i reduce the fuel consumption again ?,

i said i am try, and i need time.

my prototype dc diesel generator

1. 3.12 KW
2. 52 V DC
3. 60 Ampere
4. 1.4 liters / hours
5. no load speed 2100Rpm
6. full load speed 1900Rpm
7. ever tested at 24 hours at full load, no change at all output parameter
8. no change at engine temperature (oil, water, muffler, and engine body)

and at this forum i need help, and need answer, can i reduce fuel consumption again ?

what i must do ?

best regards

saut

sorry for my bad english language

What must you do? You must improve the low generator efficiency which is wasting power and fuel.

I suggested generator design for 1500 rpm, rather than 1900 rpm was increasing winding resistance a lot.

Also, standard r.m.s. winding voltage for 3 phase bridge is 0.74 x mean DC output required + diode voltage drop e.g. [52 x 0.74] + 2 = 40.5 V.

As for design for wrong speed, design for 55 VAC r.m.s. winding nearly doubles winding resistance and losses.

I also think that bringing 3 wires out of generator instead of 12 and using 6 diodes instead of 6 bridges may get less manufacture time/complication as well as lower component cost.

67model

what's the application? there are references both to a DC load and 50 / 60 Hz. If you want to generate DC, you should be able to use switched FETs instead of diodes and make it more efficient. You will have to do something clever to achieve that but if you have a brushless alternator something like that is happening already and perhaps you are rectifying a switched output and regulating that instead of using switching techniques directly.

application for telecommunication equipment

output voltage from the brushless alternator already 42VAC

i use direct rectifier, use full bridge diode.