14. starptautiskā konference 2012 - Latvijas Jūras akadēmija

Proceedings of 14th International conference „Maritime Transport and Infrastructure - 2012”nQ ∑ = z∙V 2 ∙ ∑ N i ,where N i – number of revolutions of the crankshaft at i starting timeBased on the Clapeyron equation, the pressure drop Δp i in starting air receiver at i startingtime calculated as follows:i=1Δp i = p oi – p i =V rec , ( 5 )Q iwhere p oi , p i – the pressure in starting air receiver at i starting time beginning and the endQ i – the consumption of the air at i time starting, V rec – the volume of the starting airreceiver.Example of calculation1210t i – sQ i – m 3p oi – MPap c = 9,5 MPa8p c = 8,5 MPat iQ i64p oi201 2 3 4 5 6 7 8 9 10 11 12 iFig.1. Diagrams of the engine starting duration, air consumption and starting air pressure at i-time startingBy way of example let's look at an L60MC six cylinder engine, produced by the MAN B&Wcompany, with a nominal power of 9880 kW at the rotation speed of 114 RPM (ω = 12,0 s -1 ). Cylinderdiameter of 600 mm, stroke - 1944 mm, crank length to connecting rod length ratio - 0,5. Thesimplified moment of inertia of the crankshaft with piston group, a flywheel, the propeller drive shaftand propeller is 125860 kg∙m 2 . Resistance moment of the propeller rotation M prop = 5800 ∙ 2 (N∙m).The exhaust commences at the angle of 120 degree of crankshaft rotation φ 3 = 120 o inrelation to TDC. The exhaust valve closes at the angle of 240 degree of crankshaft rotation φ 3 = 240 oin relation to TDC. Compressed air pressure at the first starting time is p g = 3 MPa. The polytropicindex is taken as n 1 = 1,35 and mechanical efficiency during engine starting η = 0,866