This chart is suited to diesel driven pumps used for irrigation and enables the operator to quickly find pump operating costs in $/ML given operating head (metres), assumed pump efficiency and diesel cost in $/Litre.

Interestingly, the flow rate pumped is not required for establishing $/ML.

This chart is based upon a new 75kW engine at 25 deg C with a Brake Specific Fuel Consumption (BSFC) of 215 gms/kWh (equivalent to 0.25 Litres/kWh**) but no attempt has been made to equate this performance to any particular engine.

Because of the widely varying performance of diesel (and other ICE) engines used in irrigation, due to such variables as naturally aspirated, turbo charged, twin turbo charged, varying cooling systems, etc, the actual BSFC of a new engine in the field may vary from 215 gms/kWh. In this case, all derived data in this chart should be re-rated accordingly.

**CALCULATING ENGINE FUEL CONSUMPTION**

Because BSFC varies with engine and fuel types and configurations, the formula to calculate fuel consumption needs to incorporate the BSFC.

Lets start with the kWh/ML for electric motors:

kWh/ML = 2.724 x m(TDH)/OPE (refer to www.talle.biz/data)

(where OPE is overall pump/motor/drive efficiency)

Select a diesel engine with, say, 215g/kWh BSFC

Diesel has a specific gravity (SG) of 0.86.

Therefore, the volume of 215g of diesel = 0.215/0.86 = 0.25 litre

Therefore, 1 kWh work requires 1/4 litre of diesel (@ 215g/kWh)

Now our formula for Litres/ML can be written as:

Litres/ML =__2.724 x m (TDH)__ (but only where BSFC = 215g/kWh)

4 x OPE

=__0.681 x m (TDH)__ (but only where BSFC = 215g/kWh)

OPE

This can also be expressed as:

**Litres/ML** = __2.724 x (BSFC g/kWh) x m(TDH)__

(SG) x OPE

Interestingly, the flow rate pumped is not required for establishing $/ML.

This chart is based upon a new 75kW engine at 25 deg C with a Brake Specific Fuel Consumption (BSFC) of 215 gms/kWh (equivalent to 0.25 Litres/kWh**) but no attempt has been made to equate this performance to any particular engine.

Because of the widely varying performance of diesel (and other ICE) engines used in irrigation, due to such variables as naturally aspirated, turbo charged, twin turbo charged, varying cooling systems, etc, the actual BSFC of a new engine in the field may vary from 215 gms/kWh. In this case, all derived data in this chart should be re-rated accordingly.

Because BSFC varies with engine and fuel types and configurations, the formula to calculate fuel consumption needs to incorporate the BSFC.

Lets start with the kWh/ML for electric motors:

kWh/ML = 2.724 x m(TDH)/OPE (refer to www.talle.biz/data)

(where OPE is overall pump/motor/drive efficiency)

Select a diesel engine with, say, 215g/kWh BSFC

Diesel has a specific gravity (SG) of 0.86.

Therefore, the volume of 215g of diesel = 0.215/0.86 = 0.25 litre

Therefore, 1 kWh work requires 1/4 litre of diesel (@ 215g/kWh)

Now our formula for Litres/ML can be written as:

Litres/ML =

=

OPE

This can also be expressed as:

=

Derating x pump Eff%

Based on BSFC of

215gm/kWh

(0.25Litres/kWh)

*NOTE:

0.681 is derived from

2.724 (constant in kWh/ML formula) multiplied by 0.25 Litres/kWh (BSFC)

Ie, 2.724 x 0.25 = 0.681

**NOTE:

Based upon

Specific Gravity

of diesel = 0.86

Ie, 0.215kg/kWh / 0.86

= 0.25 Litre/kWh

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June 16th 2020

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Skype: robwelke

DERATING FACTORS FOR DIESEL ENGINES

Generally, diesel engines used for irrigation require numerous de-rating factors according to their individual application.

DERATING factors used in

for biofuel, add 7% (0.93)

for engine accessories, check with manufacturer

for gear drive, add 5% (0.95)

for belt drive, add 10% (0.90)

for each 25kW below 75kW, add 5% (0.95/25kW)

for altitude, add 1% per 200m above sea level (0.99/200m)

for temperature, add 5% for each 10 deg C above 25 deg C (0.95)

for humidity, add 3% for every 10% humidity over 65%

DERATING factors used in

for engine accessories, add up to 8% (0.92)

for gear drive, add 5% (0.95)

for belt drive, add 10% (0.90)

for elevation, add 3% per 1000ft above sea level

for temperature, add 1% for each 10 deg F above 60 deg F

Derating factors are accumulative.

Therefore, add all derating factors applying to each site.

Eg, operating at 45 degC (10% derate) plus belt drive (10% derate),

= [1-(0.1 + 0.1)] = 0.80

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No responsibility will be accepted for any application of this chart.

This formula can then be applied to a range of fuels, including:

# diesel engine (SG = 0.86 @ 16

# gasoline engine (SG = 0.75 @ 16

# LPG engine (SG = 0.55 @ 16

# CNG engine (SG = 0.32 @ 16

#

Appropriate BSFC and Specific Gravities need to be factored into the formula.

Adopting the following conversions:

3.785 litres = 1 gallon US

1 metre = 3.2808 ft

BSFC [g/(kW·h)] = BSFC [lb/(hp·h)] × 608.277

BSFC [lb/(hp·h)] = BSFC [g/(kW·h)] × 0.001644

1 Megalitre = 0.8107 ac-ft

SG x OPE