SOUTH TYNESIDE COLLEGE FACULTY OF MARINE & MECHANCIAL ENGINEERING CLASS ONE ENGINEERING KNOWLEDGE ~,ENGINE PERFORMANCE Page Indicator diagrams 2 -, ---, -, -, ~ Engine diagnosis 10 Load diagrams 14 Engine safety margins 16 A\INDCARD.doc ENGINE PERFORMANCE Page 1 of 17 /-fIN DfYll}(lO J; E /( Cfl\o/O(L) ~ I:; t- ~, ,.t) VI , , ::. 1;) -I d ~Q .~ INDICATOR DIAGRAMS Indicator diagrams can be used to inv~sti9.ate sp~cific T~ults~~ the operation of the engine, especially in the B.l!impor!al1tc.omQ.ustioo_seql,Jence...The cards can be taken by either the tradj!ional.L!lechaJJLGpJi.Ddicato,L or using the more IJ1Q.d_e.~mle.ctrolJic. indicato!. Once the cards are taken they can be examined for specific fault~ such as 1. Late fuel injectioQ.,which is identified by lower peak pressures, higher exhaust . temperatures,and highersmokelevels 2. Early fuel ioj~ctLofJ,which is identified by higher peak pressures, and possible cylinder knocking 3. Defective fu~Jioj~ctqr, which is identified by lower peak pressures, higher exhaust temperatures and higher smoke levels 4. Worn fue.tpl.jm~,which is identified by lower peak pressures, and possibly lower exhaust temperatures 5. Defective pi~ton ring~pnd exhaust valve~, which is identified by lower compression and peak pressures, and higher exhau.sttemperatures There are five types of indicator cards, which can provide the following information: Power or in-phase cards . Cylinder power, calculated from the area within the p-V diagram . Indicates afterburning present when card shape enlarged during the expansion stroke Draw or out-of-phase cards . Measurement of the compression pressure . Measurement of the point of fuel ignition Liqht sprinq . Fouling of exhaust or scavenge gas flows Pressure derivative . Measurement of the point of fuel ignition . Measurement of the maximum rate of pressure rise following initial combustion Compression card . Measurement of the compression pressure . Timing check of the indicator cam A\lNDCARD.doc ENGINE PERFORMANCE Page 2 of 17 ~ate,fu.eLiriieclli2£l1Later fuel injection is a common problem, and will occur when any wear occurs in the fuel injection or camshaft drive system. The results of the late fuel1njection can be similar to that of the worn fuel injection pump or injector, and shows the important of collecting all the information from the engine before analysing. In this case the trace of the draw card clearly shows that the fuel is being injected later than normal. Thus this fault must be attended to first, before any possible differences in the cylinder powers or exhaust temperatures are investigated. In this example the fuel injection has been retarded by 4 degrees on a slow speed engine. Other importantiParaffreTer chang~ithat were noted were . 35°C increasein cylinderexhausttemperature . 12% decrease in cylinder power . 15 bar decrease in cylinder maximum pressure If the exhaust temperature increase had been noted, and this change was adjusted by decreasing the fuel pump rack position alone, then the imbalance between cylinder powers would be even greater than before. The ~~d§>~of this late fuel injection could be: . Incorrect fuel pump timing adjustment . . Wear in the camshaft drive system (either gears or chain drive) . Worn fuel pump plunger, but this would also inject less fuel hence the exhaust temperature would usually change very slightly . Defective fuel injection pump delivery or suction valve/spring B.~A 100 DraIN card shoINinQ late fuel iniection 120 /> // \ ./.--C-../ \ \.. / / \ ! \, / \ ( , // \, / \, / / -, , . o,;~;1 j - / ~4p / \ I . /// ( -- f , / I,\ ./ I! \ ~_..,~ i, ---- ---. so 60 30 II: I: I, ,I 0 -120 -40 0 B0 ~,JofTIlal dravv card Cdld ;I,o,N,nCJ fuel (>I-cH:lion ntu«(jed by 4 oJei.JfOeS A\INDCARD.doc ENGINE PERFORMANCE Page 3 of 17 -= ~( r_~ r-~i C.. c-! ;-J 9 (;] (;9 ~ e:- .... r-J ~J V \ e;- t-- CI.. C;; I~.D..~ r--.. (-J ,J J ~ ~ C- rJ C~ c ~ c ~ {=:{=: r:: . 10% engine / operational margin E.M./ a.M. r 5% for shaft- t generatorSIG I Engine Power [% Ax] 100 90 72.3 I I I i I I propeller curve! without sea margin I!- 100 a logarithmic scale Engine Speed [% Rxj NSDlOOSlA-ESPMlClF4 Fig. 4 Load range diagram for an engine equipped with a main engine-driven generator, whether it is a shaft generator or a PTO-driven generator A\INDCARD.doc ENGINE PERFORMANCE Page 17 of 17 e e. t r.... ( { e. ~ Co C C C7.
Posted on: Wed, 13 Nov 2013 06:48:47 +0000
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