《轮机仿真及控制技术》课程教学课件（讲稿）01 Marine engineering thermodynamics

LECTUREONE-1Marine engineering thermodynamicsLEARNINGOBJECTIVESTo understand reciprocating engine principles and processes aswell as marine engine terminology and geometryTo define marine engine performance indices and assess marineengine performance and efficiencyToexplain specificfueland airconsumption-To define the various methods of supercharging and explain theeffect of superchargingtomarineengineperformanceTo derive the operating envelopes of naturally aspirated andturbocharged engines and limitations thereofTo define and perform air-standard cycle analysis:To understand Diesel and Otto cycles as well as Seiliger cycle:To calculate net heat and work on the Seiliger cycle.To calculate efficiency of the Seiliger cycle21

1 LECTURE ONE – 1 Marine engineering thermodynamics 1 LEARNING OBJECTIVES • To understand reciprocating engine principles and processes as well as marine engine terminology and geometry • To define marine engine performance indices and assess marine engine performance and efficiency • To explain specific fuel and air consumption • To define the various methods of supercharging and explain the effect of supercharging to marine engine performance • To derive the operating envelopes of naturally aspirated and turbocharged engines and limitations thereof • To define and perform air-standard cycle analysis • To understand Diesel and Otto cycles as well as Seiliger cycle • To calculate net heat and work on the Seiliger cycle • To calculate efficiency of the Seiliger cycle 2

Performanceof MarineEnginesNik.XirosLargeMarineEngines-Background:Diesel,2-stroke→Highefficiency(>50%): Large-bore, Turbocharged → High power output (up to 100MW)·Slow-speed,Long-stroke, Reversible→Direct-driveSimplicity→Lowmaintenance,Robustness··ElectroniccontrolLowemissions&fuelconsumption.Consumeheavyfuelormarinedieseloil.Intermit shaft generator, exhaust gas boilerDRAWBACKS·Verylarge size&weight:Supportingauxiliarymachineryrequirements·Complicated startingprocedure2

2 Performance of Marine Engines Nik. Xiros 3 Large Marine Engines – Background • Diesel, 2-stroke
High efficiency (>50%) • Large-bore, Turbocharged
High power output (up to 100MW) • Slow-speed, Long-stroke, Reversible
Direct-drive • Simplicity
Low maintenance, Robustness • Electronic control
Low emissions & fuel consumption • Consume heavy fuel or marine diesel oil • Intermit shaft generator, exhaust gas boiler DRAWBACKS • Very large size & weight • Supporting auxiliary machinery requirements • Complicated starting procedure 4

Large Marine Engines-BackgroundLarge Marine Engines-Background

3 Large Marine Engines – Background 5 Large Marine Engines – Background 6

Large Marine Engines-BackgroundMAWK98MCWorking principle of a 2-stroke dieselexhaustvale

4 Large Marine Engines – Background 7 Working principle of a 2-stroke diesel 8

2-stroke diesel scavenging conceptsIndicatordiagrams7=8VsVsVrocVTDCA)4-strokecycleB)2-strokecycle105

5 2-stroke diesel scavenging concepts 9 Indicator diagrams 10

IndicatedworkandIMEPIndicated work (per cylinder) is defined on the basis oftheIndicatordiagramshownearlierW,= Φ p.dvcycleIndicated Mean Effective Pressure (Mean IndicatedPressure)W,=ppdvWcycleIMEP=Pmi=1VsVs11EffectiveworkandBMEPEffective work is the work delivered at the outputflangeof the engine per cycle and per cylinder2元k1W.:IM-dalangZcBrake Mean Effective Pressure (or just Mean EffectivePressure)W.BMEP=PmeVs126

6 Indicated work and IMEP Indicated work (per cylinder) is defined on the basis of the Indicator diagram shown earlier i cycle W p dV = ⋅ ∫ Indicated Mean Effective Pressure (Mean Indicated Pressure) i cycle i mi S S W p dV W IMEP p V V = ⋅ = = =
∫ 11 Effective work and BMEP Effective work is the work delivered at the output flange of the engine per cycle and per cylinder 2 0 1 k e flange C W M d Z π = ⋅ ⋅ α ∫ Brake Mean Effective Pressure (or just Mean Effective Pressure) e me S W BMEP p V = = 12

EngineefficiencyindicesOcombCombustionefficiencyNcombQfQimHeat input efficiencyng=Qcomb$p.dvW,cycleThermodynamicefficiencyNd =QnT -dscombustionW.BMEPMechanical efficiencynm=W,IMEP13OverallEngineEfficiencyWne2nmt'Icomb0f147

7 Engine efficiency indices Combustion efficiency , comb comb f f L f Q Q m h Q η = = ⋅ Heat input efficiency in q comb Q Q η = Thermodynamic efficiency i cycle td in combustion p dV W Q T dS η ⋅ = = ⋅ ∫ ∫ Mechanical efficiency e m i W BMEP W IMEP η = = 13 Overall Engine Efficiency e e m td q comb f W Q η η η η η = = 14

IndicatedPower&BrakePowerofengineIndicatedPowerpercylinder&overallWN=pav.=P=Pav.NZPiteyl =kkkBrakePowerofengineP=W.NZe= Pav.NZkk15Engine TorqueDefinition of Brake Torque developed by engineZc-V.NZC=MP=M-2元Ng=PmeV,Pm-k2元kRelationshipto instantaneous enginetorque2元k1Zc_.W.MB=IMe'daflan2元k2元k168

8 Indicated Power & Brake Power of engine Indicated Power per cylinder & overall , i E E E C i cyl mi s i mi s W N N N Z P p V P p V k k k ⋅ = = ⋅ ⇒ = ⋅ Brake Power of engine e E C E C B me s W N Z N Z P p V k k ⋅ ⋅ = = ⋅ 15 Engine Torque Definition of Brake Torque developed by engine 2 2 E C C s B B E me s B me N Z Z V P M N p V M p k k π π ⋅ = ⋅ = ⋅ ⇒ = ⋅ Relationship to instantaneous engine torque 2 0 1 2 2 k C B e flange Z M W M d k k π α π π = ⋅ = ⋅ ⋅ ∫ 16

SpecificFuel Oil Consumption of enginemSFOC =1CN6ZmmfESFOCW.W.Z.N上17Airconsumption&A/FofenginemcA.minStoichiometric A/F6mf(actual combustion A/F)AirexcessratioamairMorTotal air excess ratiomcA.minA/F="= Au-GAir-to-fuel ratio (A/F)m,189

9 Specific Fuel Oil Consumption of engine f B f C E f e C E e m SFOC P m Z N m SFOC W Z N W = = = 17 Air consumption & A/F of engine Stoichiometric A/F CA,min f m m σ = Air excess ratio (actual combustion A/F) λ σ = Total air excess ratio ,min air tot CA m m λ = Air-to-fuel ratio (A/F) A/F air tot f m m = = ⋅ λ σ 18

Specificairconsumptionofengine(Specific air consumption) = A/F. SFOC1Engine Supercharging-Concepts:Mechanically-driven supercharging(or, simply,supercharging）Turbosupercharging(orturbocharging)Electrically-driven supercharging2010

10 Specific air consumption of engine (Specific air consumption A/F ) = ⋅ SFOC 19 Engine Supercharging – Concepts • Mechanically-driven supercharging (or, simply, supercharging) • Turbosupercharging (or turbocharging) • Electrically-driven supercharging 20