I.C. ENGINES
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I.C. ENGINES Practical No: 3 (22 Apr, 2014) Report Writing • Title • Date • Object • Reason for carrying out the experiment and whether it s to prove some theory • Apparatus • Specification of engine Report Writing • Apparatus • Specification of engine and equipment • Clear description if the apparatus used • Illustrated by simple diagrams and photos Report Writing • Procedure • An account of things done before and during the experiment • Results • Record of all data • Reading taken before and during the experiment • Results should be in tabulated form Report Writing • Results • Formula used foe the calculations and one specimen of each type of calculation should shown • Graphs drawn to show the results must be clearly marked with • Title • Date • Scales Report Writing • Conclusions • An account of any incident or event during the experiment • Suggestions why the experiment and theoretical results do not agree • Do not always blame the equipment Report Writing • • • • • • Hints Always write in past tense Make no personal references Examples Weights were placed on the carrier Reading were observed at two minutes intervals • Engine speed was increased • Temperature was constant Brake Power Test • Apparatus • Hydraulic or electrical dynamometers are used for the testing • Dynamometer • Dynamometer can measure the output torque when driven by engine • Also measure input torque when used as electric motor to drive or rotate engine Brake Power Test • Dynamometer • The motoring test if carried out when engine is cold gives a measure of the load which would be put on the starter motor when the engine is in the vehicle • Further tests can be carried out at various engines temperatures including extreme starting conditions and with different grades of lubricant oil Brake Power Test • Dynamometer • Motoring the engine at normal working temperature enable the friction and pumping losses to be determine • For pumping losses engine can be relieved of its effective compression by removing the spark plugs or injector the remaining losses are frictional Calculation for Power and Torque • πππππ’π = πΉππππ (π) π₯ π·ππ π‘ππππ ( π) ( π‘ππππ’π πππ) • π = πΉ (π) πΏ (π) • π΅ππππ πππ€ππ ππ = π × π΄ππππ ππ πππππππ • = π × 2 × π × πππ£/sec = 2 π πΉπΏ ( πππ£/sec) Pb = 2 π FL ( rev/sec) • • • ππ = πππ£ ) πππ 2ππΉπΏ ( 60 Calculation for Power and Torque • ππ = • If 2ππΉπΏ 2 ππΏ 60 • Then • ππ = πΉkc πππ£ ( ) πππ 60 = Constant say kc Example • A four cylinder , four stock engine has a piston area of 0.008 m2 and stock of 0.025 m and it is tested against a dynamometer with torque arm of 0.4475 m, • P ( brake power) is given by Fk c1 Rev min 60 • Torque in Nm by Fk c2 • and b.m.e.p (break mean effective pressure) in kN/m2 by F k c3 • Where F = break load in N and k c1 , k c2 and k c3 are constants dependent upon the dimensions. • Find the values of k c1 , k c2 and k c3 Example • • • • Data Formula Sol To find k c1 • ππ = • ππ = πΉ πππ£ ( ) πππ πΎπ 2ππΉπΏ πππ£ ( ) πππ 60 Example • Sol • ππ = • ππ = • ππ = • ππ = πππ£ ) πππ 2ππΉ(0.4475 π) ( 60 πππ£ ) πππ 3πΉ ( 60 πππ£ ) πππ πΉ( 20 πΉ πππ£ ( ) πππ πΎπ • k c1 = 20 Example • • • • • • • • Sol πππππ’π = F x 0.4775 ( Nm) k c2 = 0.4775 For k c3 Work done = Force x Displacement( Nm) = m.e.p x Area x Stock ( Nm) = pAL Work done / sec = p x A x L x S ( no of stocks) Example • • • • • • Sol i.m.e.p = work done / sec Indicated Power (Pt) = p x L x Ax S b.m.e.p = π Pt πππ£ π×p×L×A ×πππ ×4 60×2 π×p ×0.125(π)×0.008( π2 ) 60×2 πππ£ × ×4 πππ Example • Sol • π×p πππ£ × πππ 30000 • Now Brake Power = • π×p = F x 30000 • k c3 = 1500 20 F πππ£ × πππ 20 = 1500 πΉ = π×p πππ£ × πππ 30000
