317
1 INTRODUCTION
Main propulsion of ships as well as marine power
station in the vast majority are the piston internal
combustion diesel engine turbocharged. There is a
direct relationship between reliability of engines for
main propulsion and power station, and marine
navigationsafetyandoperatingcosts.
The operating costs of ma
rine diesel engines are
very high, primarily because of the relatively high
pricesoffuelsandlubricatingoils.Hence,thecostof
exploiting them are even over 70% of the operating
costsoftheentireengineroomandhasasignificant
influenceonthecostsofoperationofthevessel.The
increaseinthesecostsma
yaffectthecurrenttechnical
condition of the shipʹs engine. The decline in its
efficiencywillcauseanincreaseinfuelconsumption.
Marine engines very complex technical objects,
having many important functional systems, which
include,inter alia,injection system, characterizedby
high unreliability. In this system, there ma
y be
different types of defects (damage) that affect the
engine parameters, including specific fuel
consumption,aswellasfailuresendanger thesafety
oftheship.
From the statistical data (Piaseczny. 1992)
concerning the most common damage to the ships
followsthat,they are relatedto low‐speed engines‐
38.0% damage, medium speed engines‐15.7% and
otherdamagetotheconcernofothermachineryand
marine equipment. Looking specifically on their
failure it has been shown that the most unreliable
enginefuelsystem(injectionsystem).Statisticsshow
thatisnearly50%ofalldamagetomarineenginesare
the fault of thi
s system. In the injection system the
most common damage occur in relation to the
injectors‐41%andinjectionpumps‐38%andthefuel
pipes‐12%(Fig.1.).
The Increase of Operational Safety of Ships by
Improving Diagnostic Methods for Marine Diesel
Engine
K.Witkowski
GdyniaMaritimeUniversity,Gdynia,Poland
ABSTRACT:Thisarticleshowstheimportanceofthediagnosticimprovementmethodsofmarineenginesto
boosttheeconomyandsafetyofoperationofmarinecargoships.
Theneedtoimplementeffectivediagnosticmethodsisjustifiedbypresentingstatisticaldataofmarinediesel
enginesfailureandthecostoftheiroperation.
Basedontheownresearchhasbeenproven,forthechosenexample,tha
tindicatordiagramsandanalysisof
indicated parameters have limited utility in the diagnosis of damages of marine engine, although this is a
methodcommonly used inoperational practice.To achieve greaterdiagnostic effectiveness, when, ba
sedon
indicatordiagrams,arecalculatedandthenthecharacteristicsofheatreleaseisanalyzed‐netofheatrelease
characteristicsandtheintensityoftheheatrelease,itwasdemonstrated.Thisprocedureisparticularlyeffective
inthediagnosisofdamageofinjectionsystemcomponentsmarinedieselengine.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 11
Number 2
June 2017
DOI:10.12716/1001.11.02.15
318
Figure1. Statistics damage of the injection system
componentsofmarineengines
Regard to the damage caused by, the most
injectorsare:
1 wearconeoftheneedle‐73%
2 wearholeandinthelossofpatencynozzleholes
injector‐12%
3 loss of pressure spring stiffness(pressure drop
injectoropening)‐4%
4 theothercauses‐11%
and damage to the injection pumps
are associated
mostoftenwith:
1 leakdeliveryvalves‐42%
2 leakinpairofprecise‐24%
3 blurringofpistonininjectionpumps‐18%
4 theothercauses‐16%.
The development of diagnostic methods is the
basisfortheabilitytodetectdefectsatanearlystage
of their
formation, thus improving the operational
safetybypreventingfailures.
2 POSSIBILITIESOFDIAGNOSISSYSTEMS
INJECTION
The improvement of the methods of diagnosis of
marine diesel engines is a very important task to
monitorengineoperation, faultdetectionatan early
stage of combustion engines are applied in the vast
majority their
formation, which contributes to
improvethe economics andsafety ofthe ship.Ships
reciprocatinginternalofthemainpropulsionofcargo
vessels(over80%),aswellasdrivemarinegenerators
set. When one talks about the need to equip with
modern marine power systems and diagnostic
equipment, it refers primarily
to the diagnosis of
marineengines.
Onshipswithconventionalequipment,ie.without
specializeddiagnosticequipment,thecurrent engine
conditionmonitoringisbasedonthemeasuredvalues
of the parameters controlled. Diagnostic evaluation
mainly includes processes: injection, combustion,
coolingandlubricationoftheengine.
Many marine power plant are equipped with
portablediagnostictestforperiodicdiagnostictesting
of engines. The measurements of the maximum
cylinder pressure, compression pressure, medium
pressureandindicatedpowerarecarriedout.
Onsomeships,withhighpowerplantsstationary
monitoring and diagnostics systems are installed,
operating on‐line. Some stationary systems are
equippedwithsystems
tomeasurethepressureinthe
fuelinjectionsystems.
Evaluationof technicalcondition andstate ofthe
motor load is thus carried out in an indirect way,
based on the known relationship between the
parametersoftheworkingprocesses,andstatesofthe
structureandtheloadtestpiece.
Thereliability
ofthediagnosis,itsuniqueness,the
ability to determine the location of faults and their
causes with this study depends largely on the
knowledgeandexperienceengineerofficer,andhasa
very subjective nature. It should be noted that the
conventional set of parameters controlled ships
currently available are not
sufficient for making a
reliable diagnosis, especially in relation to fault
location.
Practical implementation of diagnostic functions
formachinecrew(engineerofficers)isnotconducive
tothefrequentrotationof crewsbetweenships. The
efficiency of the diagnostic process is particularly
unsatisfactory on modern building ships, with a
complexstructureand
ahighlyautomateddesign,on
whichalsoappliesadditionalprincipleoflimitingthe
numberofmembersofthecrewinengine‐room.
Alargeamountofcurrentdutiesperformedbythe
engineer officers on the one hand, and the lack of
appropriatediagnosticmeasures,ontheother,donot
facilitate
the implementation of diagnostic tasks.
Marineenginesaretechnicalobjectswitha highlevel
ofcomplexity(severaltensofthousandsofelements).
Each of these elements can characterize in
technical terms even several parameters of the
structure. Controlling the technical condition in this
situationisverydifficult.Asaresult,the
functionsof
themachinecrewvesselsareoftenlimitedtoremoval
duringthevoyageofthemarinefailure,to maintain
theenergeticautonomyofthevessel.Thesesituations
are often the result of not detected in time damage.
Thenumberoffailurescouldbysignificantlyreduced
byadequatelydevicesand
diagnosticmethods.
Functional system of marine engine, which has
basicinfluenceonthequalityoftheworkprocess,the
economicsofoperationoftheengineanditsreliability
istheinjectionsystem.
During running the marine engine, operational
supervisiontheenginefuelsupplysystemisreduced
to operating current control operating
parameters of
as well as for periodic cleaning of fuel filters and
centrifuges as well as tightness control the entire
system. The main parameters on the basis of which
engineeroverseestheworkoftheenginefuelsupply
system are: pressure and temperature (viscosity) of
fuel.
Regardingtotheinjection
systemconditionofthe
injectorsischeckedperiodically.
To evaluate the operation of the injection system
aremainlyusedthefollowingparameters:
1 operational(routinelymeasured):
theexhaustgastemperature,T
g,
2 readwithindicatordiagrams:
maximumcombustionpressure,p
max,
meanindicatedpressure,p
i,
the angle where p
max occurs, referred to TDC,
αp
max.
Inthediagnosisofdefects intheinjectionsystem
would be useful to measure the pressure in the
system.Themainparametersdeterminedonthebasis
ofthismeasurementare:
319
themaximuminjectionpressurefuelinjectors,p
max
inj.,
injectoropeningpressure,p
openinjr.,
theangleofinjectionperiod.
The parameters read on the basis of recorded
pressure in injection system are indeed important
diagnostic, but their measurement isdifficult due to
thelimitedsensorsinstallationpossibilities.
Injection system, for security reasons, must be
leakproof. Injection piping commonly placed in
special cases (
ʺbuffer zonesʺ), which in the case of
damage to the fuel pipe do not allow uncontrolled
effluentoffueltotheengineroom.
Therefore, it is advisable to search for such an
effective method of diagnosing damages of the
injectionsystem,whichdoesnotrequireinterference
intheinjection
system.Thisisaconditioncorrespond
tomethods basedon theanalysis ofthe information
containedintheindicatordiagrams.Thiswillbethe
indirect method to evaluation of the technical
condition of injection equipment, which will cancel
costlyandunreliablemeasuringsystemsthepressure
intheinjectionsystems.
In order
to obtain an effective method for the
identification of major damages components in the
injection system in‐depth analysis of indicator
diagramsisneeded.Thisreferstothedesignationon
the basis of the indicator diagram heat release
characteristics,obtainedbasedonthemeasurementof
cylinder pressure the electronic indicator.
Cylinder
pressure transducers are mounted on the indicator
valves.
3 THEFUELSUPPLYSYSTEMSMODERN
MARINEENGINES
Modern marine propulsion engines and generator
sets are supplied mainly with heavy fuels (Heavy
FuelOil,ResidualFuels),andtheviscositycanbeata
temperature of 100 ° C 1,414 cSt for
Marine Light
Fuel Oil and 1055 cSt for Marine Fuel Oil. Lower
viscosity fuels are used to for supplying the four‐
stroke medium speed engines, while the higher
viscosity fuel‐for supplying the low speed two‐
strokeengines.
Heavy fuel oil are contaminated with, inter alia,
sulfur, water, compounds
contained in seawater,
bituminous materials (resins, hard asphalt) and
solids. Such fuels require specific preparatory
activitiespriortoinjectionintotheengine.
Theproblemswithusingheavyresidualfuelscan
becategorized as: storageandhandling, combustion
quality, contaminants‐resulting in corrosion and
damage to engine components. Fuel supply to the
combustion chamber of a piston engine performs
injection system, which feeds the fuel at a certain
time,properlyatomized,inanamountcorresponding
totheinstantaneouspowerrequirement.
In contemporary marine engines still dominated
bytraditionalinjectionsystems,areconstructedwith
thefollowingelements:
injectionpumpdrivenbythe
camshaft,
highpressurefuelpipes,
fuelinjectors.
Injection pumps are displacement pumps, piston
type, and typically each cylinder has a separate
injectionpumporaseparateoperating unitconsisting
of a cylinder, piston, non‐return valve and drive
mechanism piston. Variable maximum pressure in
injectionpipescanobtaina
valuefrom40to100MPa.
Energeticandeconomicindicators(parameters)of
theengine,andthereliabilityofitsoperationlargely
dependsontheoperationoftheinjectionsystem.On
the one side an important factor will be
constructional, technological and manufacture
perfection of system components, especially the
injectionpumps
andinjectors,ontheotherhand, the
proper conduct static regulation and proper
exploitation.
It is believed that the most important quality
parameters of the regulation of the conventional
injectionsystemarethebeginning,end,andduration
of fuel delivery by the pump and the injector
expressed in degrees of crankshaft
rotation. From
these parameters, under the constant engine load,
combustion process depends on. To combustion
process evaluate it uses dynamic parameters and
economicindicatorscycle.
In practice, sought the optimal injection advance
angle, to achieve high diesel engine efficiency, for a
givenload.
On ships during sea voyages it takes
place
attemptstodiagnosedamageto theinjectionsystem
byanalyzingthechangesinmarineengineoperating
parameters, including, in particular indicated
parameters. There are analyzed, among others,
changesofthemaximumcylinderpressure.
Thesignificantimpactonthevalueofthemaximal
cylinderpressureisthebeginningoftheinjection,
and
more precisely‐associated with injection, ignite the
fuel‐air mixture. Too the early injection (ignition)
causes an increase in the maximum pressure, while
thetoolate‐maximumpressuredrop.Inmostlarge
marine engines change injection timing fuel of 1
changesmaximalpressurefrom0.1to0.4MPa.
The
maximum pressure (pmax) is a parameter, on
whichallcomponentsoftheworkingprocesshavean
influenceon,andinparticular:
injectiontimingandthefuelself‐ignition(injection
timingandfuelignitionangleexpressedrelativeto
theupperdeadcenterofthepistoninthecylinder
‐TDC),
the
sizeoftheinjectedfueldelivery,
fuelqualityandthequalityoftheresultantfuel‐air
mixture,
pressureandtemperaturechargeair.
the pressure and temperature at the end of the
compressionstroke.
Thisindicatesthattheanalysisofthevalueofthis
parameter does not always lead
to the detection of
faults in the injection system. In many ships engine
room, where it is possible to indicate individual
enginecylinders,attemptsaremadetodiagnosefuel
injectionsystemsbydirectlycomparingtheindicator
diagrams.Properdiagnosticinferenceonthebasisof
theaboveprocedureisdifficultand
uncertain.Thisis
confirmedbythetestresults.
320
Figure 2 shows graphs indicator measured on a
nine‐cylindermarineengineSULZER9RTA90usedto
drivethemaincargoship.Althoughyoucanseethe
differenceinthecourseofexpansionpressureinthe
cylinder 2, but it is very difficult to say what is the
cause. That is
why nowadays should be used a
deepened analysis of the indicator diagrams, which
related to calculation on the basis of the graphs of
heat release characteristics. This requires the
developmentofanappropriatemodelforcalculation
and software used electronic indicators, but it can
bringtangiblebenefits.
Figure2.IndicatordiagramengineSULZER9RTA90:c1c9
‐individualcylinderpressure(source:ownresearch)
4 HEATRELEASEMODELFORTHEENGINE
WITHDIRECTINJECTION
Developmentofmodelingheatreleasepistonengines
occurredattheendofthesixtiesandtheseventiesof
the last century, which was largely associated with
thedevelopmentofcomputercapabilitiescalculations
andsimulationresearchandtheemergenceofdiesel
engine
newresearchopportunities.
Inthediagnosisofpistonenginesareofparticular
interest in single‐zone models based on indicator
diagramsasasourceofinformation(Heywood.1988,
Kriger et al. 1966, Schweitzer 1926, Wajand. 1966).
Indicator diagrams are commonly used in research
anddiagnosticscombustionpistonenginesconducted
bothin
thelaboratoryandsupplies.Thisalsoapplies
to tests carried out in the country (Ambrozik et al.
1983, Ambrozik et al. 2005, Lyn. 1960, Michalecki.
1973, Polanowski. 2007, Polanowski et al. 2011,
Wajand.1966).
Kriegerand Bormanmodel (Kriger etal. 1966) is
commonly used for diesel engines with direct
injection.
Thestartingpointforeachmodelofheatreleaseis
theprincipleofconservationofenergyintheformof
thefirstlawofthermodynamics,whichisforanopen
systemcanbewrittenasfollows:
i
h
i
đmđQđWdUđQ
chsp
(1)
orintheformofheatreleasedynamicsequationsin
thetimedomain:
ii
ch
sp
hdm
d
d
d
đQ
d
đW
d
dU
d
đQ
(2)
weređQ
sp = the heat transported (by combustion of
fuel),dU=changeininternalenergyofthemassinthe
system,đW=theworkproducedbythesystem,đQ
ch
= the cooling heat loss,đmi = flows in and out of
crevice regions; piston ring blow‐by and direct
injection of fuel into the cylinder, h
i = the enthalpy
fluxacrossthesystemboundaryand=time.
Due to difficulties in calculating the cooling heat
and charge loss as a result of gas blow‐by, for
diagnostic purposes it is appropriate to use the net
heat release characteristics, which is an sum of the
internal
energyandthework.
Itisassumedthatthecoolingheatloss,willbethe
sameforeachcylinder,andwillhaslittleeffectonthe
characterofthecourseofheatreleasecharacteristics.
TheformulaforQ
nnetheatevolutionisobtained
bytransformationofequation(1)totheform:
đWdU
i
h
i
đm
ch
đQ
sp
đQ
n
đQ
(3)
Assumingthatthegasisidealandneglectingthe
exhaustandcreviceloss,equation(1)takestheform
(Rychteretal.1990):
VdppdVđQ
1
1
1
(4)
were=const–isentropicexponent,V=volumeof
thecylinder,p=pressureofthecylinder.
TheinstantaneousvolumeVofgasinthecylinder
canbeexpressedasthesum:
V=Vs–Vsx+Vc+Vz+Vpx (5)
wereV
s=displacementvolumecylinder,Vsx=cylinder
volumecorrespondingtothedistancetraveledbythe
piston from a BDC, V
c = clearance volume, Vz =
change the volume of the cylinder due to wear and
impact assembly, V
px = the apparent change in the
volumeofthecylinderduetogasblow‐by(function
roadofthepiston).
IfitwereacceptedV
z=0andVpx=0,thecurrent
volumeofgasinthecylinderisgivenby:
V=Vs–Vsx+Vc (6)
After dividing the equation (6) by the stroke
volumeV
swegetvolumeindimensionlessform:
v=1–vsx+vc (7)
Dividingequation(4)bythedisplacementvolume
cylindertheintensityoftheheatreleaseq,writtenin
theform:
d
dv
p
d
dp
v
dV
đQ
q
s
n
1
1
(8)
321
5 ANEXAMPLEOFPRACTICALUSEOFTHE
HEATRELEASECHARACTERISTICSINTHE
DIAGNOSIS
On the basis of preliminary verification indicator
diagrams shown in Figure 2, it may by noticed that
further analysis is necessary, first of all, the graph
obtainedforthecylinder2.
In deepened analysis of the
characteristics of the
designated heat release‐net of heat release
characteristicsQandtheintensityoftheheatrelease
q. These characteristics are shown in Figure 3 and
4.Theirwaveforms indicatea faulty operation of the
injection system the second cylinder. Especially a
characteristic is the change q ‐instantaneous clear
increaseintheangleofabout210degreesrotationof
the crankshaft and a significant increase in the
maximumvalueofQforthecylinderontheangleof
about 210 degrees rotation of the crankshaft, what
probable cause is post‐injection of fuel caused by
faulty regulation of the overflow
valve on the
dischargesideoftheinjectionpump.
Figure3.CharacteristicsofheatreleaseQdeterminedonthe
basisofindicatordiagramsshowninFigure2:c1c9‐Qfor
eachcylinder(Source:ownresearch)
Figure4. Thecharacteristicsofintensityoftheheatreleaseq
determinedonthebasisoftheindicatordiagramsshownin
Figure2:c1c9‐qforeachcylinder(Source:ownresearch)
6 CONCLUSIONS
Operatingexperienceshowsthattheinterpretationof
diagnostic indicator diagrams in the diagnosis of
damage to the elements of injection system is often
insufficient.
Theresearchresultsconfirmthat,withheatrelease
characteristicscalculatedonthebasisoftheindicator
diagrams, can be more easily and with greater
certainty
to recognize the damage occurring in the
injectionsystemsofmarineengines.
Thecharacteristicsofheatreleasenetcanbeused
in the diagnosis of injection systems of marine
engines to detect such damages as loss of tightness
precision pairs, the loss of patency nozzle holes
injector, pressure drop injector
opening and many
others.
The improvement of diagnostic methods of
injection systems can contribute to improving the
reliabilitygrowthof marineengines, maintenanceof
their economic exploitation, and also has an impact
onthesafeoperationofships.
REFERENCES
AmbrozikA.,SobocińskiR.1983.Analizaprocesuspalania
tłokowego silnika spalinowego na podstawie wykresu
indykatorowego. Prace Instytutu Transportu
PolitechnikiWarszawskiej.nr21.
Ambrozik A.,Łagowski P. 2005. Wybrane metody
sporządzania charakterystyk wydzielania ciepła w
silnikachspalinowych.JurnalofKONES.Vol.12,No1‐
2.
Heywood J.B. 1988.
Internal combustion engine
fundamentals.McGraw‐HillCompany.
Lyn W.T. 1960. Calculations of the Effect of Rate of Heat
ReleaseontheShapeofCylinder‐PressureDiagramand
CycleEfficiency.Proc.ImechE.No1.
Kriger R.B., Borman G. L. 1966. The Computation of
Apparent Heat Release for Internal Combustion
Engines.Proc.Diesel
GassPower,ASME.
MichaleckiM.1973.Badanieprocesuwydzielaniaciepław
dwusuwowym wysokoprężnym silniku na podstawie
wykresu indykatorowego. Zeszyty Naukowe
PolitechnikiGdańskiej,MechanikaV.
Piaseczny L. 1992. Ocena niezawodności okrętowych
silników spalinowych w aspekcie tworzenia ich
systemów diagnostycznych i obsługowych. Materiały
Konferencji Naukowo
‐Technicznej, ITEO AMW,
Gdynia.
Polanowski S., 2007. Studium metod analizy wykresów
indykatorowych w aspekcie diagnostyki silników
okrętowych. Zeszyty Naukowe AMW, Nr 169 A,
Gdynia.
Polanowski S, Pawletko R. 2011. Acquisition of diagnostic
information from the indicator diagrams of marine
engines using the electronic indicators. Journal of
KONESPowertrainand
Transport,Vol.18.
Rychter T., Teodorczyk A. 1990. Modelowanie
matematyczne roboczego cyklu silnika. PWN,
Warszawa.
Schweitzer P.1926. The Tangent Method of Analysis of
IndicatorCardsofInternalCombustionEngines.Bulletin
nr35.PennsylvaniaStateUniversity,September.
Wajand J. 1966. Możliwości wykorzystania wykresów
indykatorowych do określenia przebiegu wydzielania
ciepła
w cylindrze silnika spalinowego. Silniki
spalinowe,nr2.
