Propeller laws (Engine speed based diagram).

6.1. What do you know about propeller laws? As per drawing below:

6.2. How to calculate theoretical propeller law?

6.2.1. Theoretical propeller law – the engine mean indicated pressure dependence of the engine speed:

6.2.2. Theoretical propeller law – the engine effective power dependence of the engine speed:

Where: P_ME^MCR (bar) – Mean Effective pressure at MCR (Maximum continues rating);

P_MEC^MCR (bar) – Mechanical loss pressure at MCR (≈ 1 bar for two stroke B& W engines);

n^MCR (rpm) – Engine speed at MCR (Maximum continues rating);

N_EFF^MCR (EKW) – Engine effective power at MCR (Maximum continues rating);

β = 1.1¸ 1.3 – mechanical loss pressure exponent.

7. Specific Cylinder Oil Consumption – SCOC.

7.1. How to calculate SCOC?

– Specific Cylinder Oil Consumption (gr/BHP· h or gr/EKW· h);

SCOC base line g_CO = 1 gr/BHP· h = 1.36 gr/EKW· h (as per diagram below)

Where: G_CO (kg/hr) – hourly cylinder oil consumption;

N_EFF (EKW) – Engine effective power;

7.2. How to calculate hourly cylinder oil consumption?

– hourly cylinder oil consumption (kg/hr);

Where: D_PL (mm) – cylinder oil lubricator plunger diameter;

S_PL (mm) – cylinder oil lubricator plunger stroke;

m (–) – lubricator stroke factor;

n (rpm) – engine speed;

i (–) – engine cylinder liner number of cylinder oil points;

– cylinder oil specific gravity SG at cylinder oil lubricator temperature T (kg/ltr);

ρ ₁₅ (kg/ltr) – cylinder oil specific gravity SG at 15 ^OC;

k (kg/ltr· ^OC) – cylinder oil heat expansion factor (≈ 0.0006);

T (^OC) – cylinder oil temperature at lubricator.

8. Specific Fuel Oil Consumption – SFOC.

8.1. How to calculate SFOC?

– Specific Fuel Oil Consumption (gr/BHP· h or gr/EKW· h);

Where: G_FO (kg/hr) – hourly fuel oil consumption;

N_EFF (EKW) – Engine effective power.