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I.C. ENGINES

I.C. ENGINES. Practical No: 5 (22 Apr, 2014). Indicated Power P i. Indicated Power P i Date Definition of P i Is the actual power developed by the engine Burning of fuel ( Chemical Energy ) in the cylinder produces Mechanical Energy Objective

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I.C. ENGINES

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  1. I.C. ENGINES Practical No: 5 (22 Apr, 2014)

  2. Indicated Power Pi • Indicated Power Pi • Date • Definition of Pi • Is the actual power developed by the engine • Burning of fuel ( Chemical Energy) in the cylinder produces Mechanical Energy • Objective • To measure the energy available at flywheel

  3. Indicated Power Pi • Apparatus • Engine • Indicator • Planimeter

  4. Indicated Power Pi • Procedure • Warm up engine • Attach indicator with the engine • Put load • Indicator will generate indicator diagram • Diagram is recording of the pressure and rate of pressure changes in the cylinder at all points during the cycle • It will give record of combustion process and pressure rise, which will show any fault in the timing of the ignition or valves

  5. Indicated Power Pi • Diagram

  6. Indicated Power Pi • Results • By using planimeter the area of pv diagram can be calculated • The gauge points on the instrument are adjusted to the length of the diagram • Now boundary of the diagram is traced around by the pointer on the instrument • Reading on its scale is noted

  7. Indicated Power Pi • Results

  8. Indicated Power PiBy calculation • Symbols • p = Mean effective pressure (m.e.p) kN/m2 • L = Length of the piston stroke, m • A = Cross sectional area of the piston • S = Number of working strokes per second

  9. Indicated Power PiBy calculation • S for engine working on the two stock cycle • S for engine working on the four stock cycle

  10. Indicated Power PiBy calculation • Total force on piston = m.e.p. x cross sectional area • Work done by the piston in one stock = force on piston ( N) x length of stock (m) • W.D = m.e.p. x Area x stock ( kJ) • W.D. = p x A x L (kJ) • Work done by piston per sec • = p x A x L x S ( kJ) • Indicated power (Pi ) = p x L x A x S

  11. Indicated Power PiBy calculation • Indicated power (Pi ) = p x L x A x S • b.m.e.p. = 𝜂 x i.m.e.p

  12. Example • A four cylinder , four stock engine with 100 mm bore and 100 mm stock develops its maximum power at 3600 rev/min. At this speed the i.m.e.p. is 760 kN/m and mechanical efficiency is 85 %. • Find indicated power and b.e.m.p

  13. Example • Data • p = 760 kN/m2 • L = 0.10 m

  14. Example • Formula • Indicated power (Pi ) = p x L x A x S • Sol • Pi = (760 x o.1 x 3.1416 x 0.1 x 0.1x 120)/4 • = 71.63 kN/m2 • b.m.e.p. = 760 x 0.85 kN/m2 • = 646 kN/m2

  15. Example • A sixcylinder , four stock engine with 60 mm bore and 85 mm stock develops a break power at 24 kW at 2200 rev/min. Calculate b.e.m.p at this speed • Let 𝜂 p denoted by b.m.e.p.

  16. Example • Data • Pb = 24 kW • L = 0.085 m

  17. Example • Formula • Pb= 𝜂 p x L x A x S • Sol • 24 = (𝜂 p x 0.085 x 3.1416 x 0.062 x 110)/4 • 𝜂 p = 907 kN/m2

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