I.C. ENGINES

Practical No: 7(5 May, 2014)

Fuel Consumption

• Objective• To calculate thermal efficiency of the

engine • Apparatus• Engine test bench• Accurate measuring tank• Flow meter• Stop watch (min time should be not less

than two minutes)

Fuel Consumption

• Procedure• Use test tank with hook gauges• Or calibrated glass measuring

cylinder• Measuring glass shaped so that fuel

falls fast at the points of calibration where time finished and finishes

• An other method is to use flow meter

Fuel Consumption

• Procedure• The scale are not linear since the

quantity of fuel flowing in unit time

Fuel Consumption

• Calculation• To convert milliliter (ml) or liters ( l) to

mass ( kg)• 1000 ml = 1 litre• Since 1 litre of water has a mass of 1 kg• 1 litre of fuel has a mass of 1 x relative

density of fuel (kg)• X litre of fuel has a mass of :• X x relative density of fuel ( kg)

Fuel Consumption

• Calculation• The quantity of fuel consumed is

measured in litre per brake power ( kW) per hour , or kg per brake power ( kW) per hour

Fuel Consumption

• Calculation

Example• A Morse test on an engine gave the following results:• Pb All cylinder working 100 kW• Pb No 1 cylinder cut out 69 kW• Pb No 1 cylinder cut out 71 kW • Pb No 1 cylinder cut out 68.5 kW• Pb No 1 cylinder cut out 71.5 kW• Find Pi , Pf and Mechanical efficiency

Example

• Formula• Pi = (A x 4) - (B1 +B2+B3+ B4)• Sol• Pi = (100 x4) – ( 69+ 71 + 68.5 + 71.5)• = 400 – 280• Pi = 120 kW• Pf = Pi - Pb

• = 120 – 100• Pf = 20 kW

Example

• Sol

• Mech Eff = 83 %