Calculation of specific fuel oil consumption (SFOC)

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Deborah Lamb
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Calculation of specific fuel oil consumption (SFOC) General Figure describes the standardized calculation order for conversion of SFOC from Reference condition (ISO) to Site/FAT

1 Calculation of specific fuel oil consumption (SFOC) General Figure describes the standardized calculation order for conversion of SFOC from Reference condition (ISO) to Site/FAT condition, and from Site/FAT condition to Reference condition (ISO). Following description is focussed on how to calculate a conversion from site/fat condition to reference condition ISO. 1 (5)

B 11 01 0 MAN Diesel & Turbo Fuel consumption (kg/h): Leak oil Fuel oil consumption is measured by a measuring tank.

2 B MAN Diesel & Turbo Fuel consumption (kg/h): Leak oil Fuel oil consumption is measured by a measuring tank. Recommended is that a recently calibrated electronic weight is measuring the fuel consumption. Measuring time should minimum have duration of 10 minutes. Values are stated in kg/h. The leakage oil (kg/h) is measured over minimum 10 min and subtracted from measured fuel consumption. Please find below diagram for different engine types running on MGO. The mentioned values are measured under controlled condition on a test bed using new fuel injection pump / fuel injection valve, and taking into consideration that temperature, viscosity, clearance, oil condition, oil quality etc can differ and thereby affect the leak oil amount. Tolerance of the values is +/-25%. Figure 1: Leak oil on full load for MGO operation (for guidance only) 2 (5)

3 1) Safety tolerance 5% 2) Correction for ambient (β-calculation) Safety tolerance 5% is subtracted from fuel consumption In accordance to ISO-Standard ISO :2002 Reciprocating internal combustion engines Performance, Part 1: Declarations of power, fuel and lubricating oil consumptions, and test methods Additional requirements for engines for general use MAN Diesel & Turbo specifies the method for recalculation of fuel consumption dependent on ambient conditions for 1-stage turbocharged engines as follows: The formula is valid within the following limits: + Ambient air temperature 5 C 55 C + Charge air temperature before cylinder 25 C 75 C + Ambient air pressure bar bar β t bar Fuel consumption factor Engine type specific reference charge air temperature before cylinder, see»reference conditions«in»fuel oil consumption for emissions standard«. Legend Reference Site/FAT Specific fuel consumption [g/kwh] b r b x Ambient air temperature [ C] t r t x Charge air temperature before cylinder [ C] t bar t bax Ambient air pressure [bar] p r p x Example Reference values: br = 200 g/kwh, tr = 25 C, tbar = 40 C, pr = 1.0 bar At site: t x = 45 C, t bax = 50 C, p x = 0.9 bar 3 (5)

B 11 01 0 MAN Diesel & Turbo ß = 1+ 0.0006 (45 25) + 0.0004 (50 40) + 0.07 (1.0 0.9) = 1.023 b x = ß x b r = 1.023 x 200 = 204.

4 B MAN Diesel & Turbo ß = (45 25) (50 40) ( ) = b x = ß x b r = x 200 = g/kwh 3) Correction for lower calorific value (LCV) 4) Correction for engine mounted pumps Engine type L16/24/S, L21/31/S, L27/38/S Engine type L23/30H/S/DF/S-DF, L28/32H/S/DF/S-DF, V28/32S/S-DF 5) Correction for exhaust gas back pressure Whenever LCV value rise 427 kj/kg the SFOC will be reduced with 1% Increased negative intake pressure before compressor leads to increased fuel oil consumption, calculated as increased air temperature before turbocharger: U = (-20 [mbar] p Air before compressor [mbar] ) x 0.25 [K/mbar] with U 0 Increased exhaust gas back pressure after turbine leads to increased fuel oil consumption, calculated as increased air temperature before turbocharger: O = (p Exhaust after turbine [mbar] 30 [mbar] ) x 0.25 [K/mbar] with O 0 4 (5)

5 6) Correction for MGO (+2 g/kwh) Charge air blow-off for exhaust gas temperature control (ex. plants with catalyst) leads to increased fuel oil consumption: For every increase of the exhaust gas temperature by 1 C, due to activation of charge air blow-off device, an addition of 0.05 g/kwh to be considered. When engine is running MGO the fuel consumption can be increased by up to +2 g/kwh due to lower energy content and longer injection duration. SFOC can in some case also be reduced by inverted fuel values of MGO. 5 (5)

MAN Diesel & Turbo. Main Engine Room Data. Project name BrasNave 25 Project type Project number 3 Date 2010 Yard

MAN Diesel & Turbo. Main Engine Room Data. Project name BrasNave 25 Project type Project number 3 Date 2010 Yard MAN Diesel & Turbo Main Engine Room Data Main Engine Compliance 6S80MC6.1-TI IMO-NOx Tier I Project name BrasNave 25 Project type Project number 3 Date 2010 Yard Country Brasil Made by BrasNave Department