The following information is required to perform the calculations:
- Engine model
- Engine developed power (MCR or CSR)
- Engine speed
- Brake specific fuel consumption (bsfc)
- Initial day tank fuel temperature
- Storage tank fuel temperature (Make-up)
- Ambient air temperature
- Day tank length, width, and height
- Typical full day tank fuel height (assume 95% of tank capacity)
- Engine fuel transfer pump flow rate (see TMI)
- Fuel heat rejection from the engine (see TMI)
- Incremental time element
Day Tank Thermal Capacity Calculation
Example:
- Application: Single main engine
- Engine Model: 3612
- Rated Power: 4640 bhp (CSR)
- Rated Speed: 900 rpm
- bsfc: 0.326 lb/bhp-hr
- Initial Day Tank Fuel
Temperature = 85ยฐF - Storage Tank Temperature = 85ยฐF
- Ambient Air Temperature = 95ยฐF
- Day Tank Dimensions:
o Length (L) = 12 ft.
o Width (W) = 8 ft.
o Height (H) = 8.42 ft. - Fuel Height (@ 95% of total Capacity) (H) = 8 ft.
- Engine Fuel Oil Transfer Pump Flow Rate: qxfer = 19.0 gpm
- Heat rejection from engine to fuel oil: Q = 1252 Btu/min
- Incremental time element: t = 60 min.
Assume that the day tank will be replenished from the fuel storage tanks when the day tank level falls to approximately 50-55% of normal operating capacity.
Some of the data above must be converted to other units prior to beginning calculations. The following formulas can be used:
- Engine Driven Transfer Pump Mass Flow Rate = Mxfer (lb/min)
Assume: #2 DO with an API gravity of 35 (7.1 lb/gal)
Mxfer = qxfer x 7.1 lb/gal = 19.0 gpm x 7.1 lb/gal = 134.9 lb/min - Engine burn rate under full load conditions:
3. Engine fuel return rate under full load conditions:
