TurbogeneratorSteamTurbineVariationinDevelopedPower ...Marine propulsion systems nowadays are usually based on diesel engines [1]. Because of their wide usage, a lot of ... Modelling

Research ArticleTurbogenerator Steam Turbine Variation in Developed PowerAnalysis of Exergy Efficiency and Exergy Destruction Change

Vedran Mrzljak Tomislav Sencic and Bozica Zarkovic

Faculty of Engineering University of Rijeka Vukovarska 58 51000 Rijeka Croatia

Correspondence should be addressed to Vedran Mrzljak vedranmrzljakritehhr

Received 2 December 2017 Revised 17 April 2018 Accepted 18 April 2018 Published 2 July 2018

Academic Editor Azah Mohamed

Copyright copy 2018 Vedran Mrzljak et al (is is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

Developed power variation of turbogenerator (TG) steam turbine which operates at the conventional LNG carrier allows insightinto the change in turbine exergy efficiency and exergy destruction during the increase in turbine power Measurements ofrequired operating parameters were performed in eight different TG steam turbine operating points during exploitation Turbineexergy efficiency increases from turbine power of 500 kW up to 2700 kW and maximum exergy efficiency was obtained at 7013of maximum turbine developed power (at 2700 kW) in each operating point From turbine developed power of 2700 kW until themaximum power of 3850 kW exergy efficiency decreases Obtained change in TG turbine exergy efficiency is caused by an unevenintensity of increase in turbine developed power and steam mass flow through the turbine TG steam turbine exergy destructionchange is directly proportional to turbine load and to steam mass flow through the turbinemdashhigher steam mass flow results ina higher turbine load which leads to the higher exergy destruction and vice versa(e higher share of turbine developed power andthe lower share of turbine exergy destruction in the TG turbine exergy power inlet lead to higher turbine exergy efficiencies Ateach observed operating point turbine exergy efficiency in exploitation is lower when compared to the maximum obtained one for839 to 1203

1 Introduction

Marine propulsion systems nowadays are usually based ondiesel engines [1] Because of their wide usage a lot ofsimulation and optimization numerical models were de-veloped [2 3] in order to investigate their operating pa-rameters Today researchers are intensively involved in theinvestigation of alternative fuels for diesel engines [4] with thegoal of reducing their emissions [5]

Unlike the rest of the world fleet the dominant type ofpropulsion for LNG carriers of any kind is steam propulsiondue to the specificity of their operation and the transportedcargo [6] (e structure of marine steam propulsion systemdoes not differ greatly in comparison with land-based steampower systems [7] but some of its components and theprinciple of operation can significantly vary

Steam propulsion system on the LNG carrier alwaysconsists of two steam generators [8] due to safety and reliable

operation (ose steam generators have burners which canoperate with two fuels simultaneouslymdashwith evaporatednatural gas from cargo tanks and with heavy fuel oil so itsoperation dynamics differ greatly when compared to in-dustrial scale furnaces [9] Each steam generator has an airheater where the air is heated with a steam because flue gassesfrom marine steam generators do not have high enoughtemperature for additional heating purposes

(e propulsion propeller drive is ensured with the mainpropulsion turbine [10] Steam propulsion systems on theLNG carriers have at least two turbogenerator sets (turbo-generator sets consist of a low-power steam turbine whichdrives an electric generator) and both turbogeneratorsoperate in parallel [11] Turbogenerator sets are designed tocover all ship requirements for electrical power and itsparallel operation ensures that ship electrical network hasalways at disposal enough electrical power because safenavigation always has a priority One such TG steam turbine

HindawiModelling and Simulation in EngineeringVolume 2018 Article ID 2945325 12 pageshttpsdoiorg10115520182945325

is analyzed in this paper from the aspect of exergy efficiencyand exergy power losses (exergy destruction) during theincrease in turbine developed power Along with the mainpropulsion turbine and two turbogenerator steam turbinesthe majority of steam propulsion systems on LNG carriershave also one low-power steam turbine for the main feed-water pump drive as can be found in several land-basedsteam power systems [12 13] Low-power steam turbinefor the main feedwater pump drive is backpressure steamturbinemdashsteam after expansion in this turbine is used insome other marine steam system components After ex-pansion in the main propulsion turbine and turbogenera-tors steam was led to the main marine condenser onliquefaction Main marine condenser operation differs greatlyin comparison with main condensers from land-based steampower systems [14] because cooling water (sea) is brought toa main marine steam condenser with pumps at low systemloads after which follows a sea accumulation system (scoop) athigh steam system loads

Condensate and feedwater return channel from the mainmarine condenser to steam generators has several deviceswhich provide water heating (e first of such devices afterthe main condenser is evaporator (freshwater generator)[15] the marine steam system component which is notrequired in land-based steam power systems After evapo-rator is located sealing steam condenser [16] and usually twocondensate and feedwater heaters (low-pressure condensateheater [17] before deaerator and high-pressure feedwaterheater [18] after deaerator) In comparison with land-basedsteam power systems marine steam system has always muchlower number of condensate and feedwater heaters becauseof limited ship space On water return channel is alsomounted hot well for collecting all the condensate from thesystem Condensate and feedwater heating system in land-based steam power systems as well as in marine steampropulsion systems is the most appropriate for variousimprovements [19] and optimizations [20] in order to re-duce fuel consumption and thus emissions from steamgenerators [21] New investigations for improving heattransfer as reported in [22] or [23] can surely be applied inmarine steam propulsion systems at several heat exchangersnot only at condensate and feedwater heaters

(e analyzed LNG carrier has two identical turbogen-erator sets that operate in parallel Each TG steam turbinehas identical operating parameters (inlet and outlet steamtemperatures pressures andmass flows) and for the analysisin this paper is selected one of them Steam turbine for eachelectric generator drive comprises nine Rateau stages Steamturbines with Rateau stages and their analysis can be foundin [24] Many details of the classic and special designs ofmarine steam turbines and their auxiliary systems arepresented in [25] and [26]

(e main goal of this analysis was to obtain the optimaloperating area of the TG steam turbine in which will beachieved maximum exergy efficiencies and minimum exergydestructions for every turbine operating point As a knownparameter is taken a TG turbine developed power which was

varied from 500 kW up to maximum turbine developedpower of 3850 kW in steps of 100 kW For each TG turbinedeveloped power turbine exergy efficiency and exergy de-struction were calculated Obtained areas of turbine maxi-mum exergy efficiency and minimum exergy destructionwere compared with the real LNG carrier exploitation(according to measured operating parameters) (e mainconclusion of TG steam turbine exergy analysis is that inexploitation turbine should be more loaded to obtain higherexergy efficiency in each operating point but it would not beadvisable that turbine operates at maximum load (at3850 kW) TG turbine exergy destruction change does notfollow the exergy efficiency trends so from the viewpoint ofturbine exergy destruction it would not be advisable thatturbine operates in the same operating areas as for maxi-mum exergy efficiency(e distribution of TG steam turbineexergy power inlet shows that the higher share of turbinedeveloped power and the lower share of turbine exergydestruction in exergy power inlet lead to higher turbineexergy efficiencies

Main characteristics of the LNG carrier in which steampropulsion system is mounted analyzed turbogeneratorsteam turbine are presented in Table 1

2 TG Steam Turbine Exergy Analysis

21 Equations for the Exergy Analysis Exergy analysis isbased on the second law of thermodynamics [27] (e mainexergy balance equation for a standard volume in steadystate is [28 29]

_Xheat minusP 1113944 _mOUT middot εOUT minus 1113944 _mIN middot εIN + _EexD (1)

where the net exergy transfer by heat ( _Xheat) at the tem-perature T is equal to [30]

_Xheat 1113944 1minusT0

T1113874 1113875 middot _Q (2)

Specific exergy was defined according to [8 31] by thefollowing equation

ε hminus h0( 1113857minusT0 middot sminus s0( 1113857 (3)

(e total exergy of a flow for every fluid stream can becalculated according to [11]

_Eex _m middot ε _m middot hminus h0( 1113857minusT0 middot sminus s0( 11138571113858 1113859 (4)

Table 1 Main characteristics of the LNG carrierDeadweight tonnage 84812 DWTOverall length 288mMaximum breadth 44mDesign draft 93mSteam generators 2timesMitsubishi MB-4E-KS

Propulsion turbine Mitsubishi MS40-2(maximum power 29420 kW)

Turbogenerators 2times Shinko RGA 92-2(maximum power 3850 kW each)

2 Modelling and Simulation in Engineering

Exergy efficiency is also called second law efficiency oreffectiveness [32] It is defined as

ηex exergy outputexergy input

(5)

22 Turbogenerator Turbine Exergy Efficiency and ExergyDestruction Low-power steam turbine for electrical gen-erator drive is condensing type and consists of nine Rateaustages [33] Schematic view of steam turbine which is di-rectly connected to an electric generator is presented inFigure 1 Steam mass flow steam specific enthalpy andsteam specific entropy at the TG steam turbine inlet andoutlet are also presented in Figure 1

TG turbine power calculation at different loads wasnecessary for the TG turbine analysis (e turbine developedpower in relation to steam mass flow through the turbinewas approximated by the third degree polynomial by usingproducer data [33]

PTG minus4354 middot 10minus10 middot _m3TG + 67683 middot 10minus6 middot _m

2TG

+ 0251318 middot _mTG minus 256863(6)

where PTG was obtained in kWwhen _mTG in kgh was placedin (6) Steam mass flow through the TG turbine ( _mTG) wasmeasured at each observed turbine operating point

Steam mass flow at the TG turbine inlet is the same assteam mass flow at the TG turbine outlet because duringmeasurements was not detected any steam leakage(emassbalance for the TG steam turbine inlet and outlet is

_mTG1 _mTG2 _mTG (7)

According to Figures 1 and 2 h1 is steam specific en-thalpy at the turbine inlet and h2 is steam specific enthalpy atthe turbine outlet after real (polytropic) expansion Com-plete exergy analysis of TG steam turbine is based on the real(polytropic) turbine expansion Ideal (isentropic) expansionis presented in Figure 2 just to compare ideal steam ex-pansion process on the turbine with the real one Steamspecific enthalpy at the turbine inlet (h1) and steam specificentropy at the turbine inlet (s1) were calculated from the

measured pressure and temperature Steam specific enthalpyat the turbine outlet (h2) was calculated from the turbinepower PTG in kW and measured steam mass flow _mTG inkgs according to [27] by using the following equation

h2 h1 minusPTG_mTG

(8)

(e steam specific entropy at the turbine outlet (s2) wascalculated from steam specific enthalpy at the turbine outlet(h2) and measured pressure at the turbine outlet (p2) asshown in Figure 2

Steam specific enthalpy at the turbine inlet and bothsteam specific entropies (at the turbine inlet and outlet) werecalculated by using NIST REFPROP 80 software [34]

TG steam turbine exergy power inlet is calculatedaccording to [7] by using the following equation

_ETGexIN _mTG middot ε1 _mTG middot ε2 + PTG + _ETGexD

_ETGexOUT + _ETGexD(9)

while TG steam turbine cumulative exergy power outlet iscalculated as

_ETGexOUT _mTG middot ε2 + PTG (10)

Cumulative TG steam turbine exergy power outletconsists of two parts steam exergy power outlet and turbinedeveloped power

TG steam turbine exergy destruction (exergy power loss)was calculated according to [35 36] by using the followingequation

_ETGexD _mTG middot ε1 minus _mTG middot ε2 minusPTG _mTG middot ε1 minus ε2( 1113857

minusPTG _ETGexIN minus _ETGexOUT

(11)Steam specific exergies at the TG turbine inlet and outlet

were calculated according to (3) by using calculated steamspecific enthalpies and steam specific entropies at the turbineinlet and outlet

(e ambient state in the LNG carrier engine roomduring measurements was

Steam turbine

Electric generator

(mTG h1 s1)

(mTG h2 s2)

Figure 1 TG steam turbine along with main operating parametersconnected to an electric generator

Saturation line

1

2

2s

p1

p2

t1

Real (polytropic) expansion

Isentropic expansion

h

s

Figure 2 Steam turbine real (polytropic) and ideal (isentropic)expansion

Modelling and Simulation in Engineering 3

(i) pressure p0 01MPa 1 bar(ii) temperature T0 25degC 29815K

(e exergy efficiency of a TG steam turbine was cal-culated according to [35 37] by using the followingequation

ηTGex PTG

_mTG middot ε1 minus ε2( 1113857

PTG_mTG middot h1 minus h2 minusT0 middot s1 minus s2( 11138571113858 1113859

(12)

23 Developed Power Variation Principle of a TG SteamTurbine TG steam turbine developed power can be cal-culated according to Figure 2 by the following equation

PTG _mTG middot h1 minus h2( 1113857 (13)

(ree different methods can be used for the TG turbinepower variation (e main assumption valid at any TGsteam turbine operating point is always the same steam inletpressure and temperature and the same steam outlet pres-sure TG turbine power variation methods are as follows

(1) Change in steam mass flow through the TG steamturbine

(2) Change in the value of steam specific enthalpy at theturbine outlet (h2)

(3) Combination of methods 1 and 2

To present the change in TG steam turbine exergy ef-ficiency and exergy destruction in this paper is selected thecombined method (method 3) for each operating point

Turbine developed power was varied from 500 kW upto a maximum of 3850 kW in steps of 100 kW Power changerequires a change in steammass flow through the turbine sothe adequate steam mass flow for any turbine power wascalculated by using the reversed equation (6) At each op-erating point steam pressure and temperature at the turbineinlet and steam pressure at the turbine outlet remainidentical to the measured data Steam specific enthalpy at theturbine outlet (h2) was calculated for each turbine power andmass flow by using (8) Steam specific entropy at the turbineoutlet (s2) was calculated for each turbine power and massflow by using steam specific enthalpy at the turbine outlet(h2) and steam pressure at the turbine outlet (p2) Change insteam specific enthalpy at the turbine outlet (h2) and changein steam specific entropy at the turbine outlet (s2) along with

the change in steam mass flow and turbine developed powercause the change in TG steam turbine exergy efficiency andexergy destruction (11) and (12)

3 Measurement Results and MeasuringEquipment of the Analyzed TGSteam Turbine

Measurement results of required operating parameters forTG turbine are presented in Table 2 Operating points inTable 2 presented LNG carrier steam system load (1 is thelowest system load and 8 is the highest system load) TGsteam turbine developed power does not depend on steampropulsion system load and it depends only on the inclusionor exclusion of ship electrical consumers Inclusion of thenew electrical consumer or more of them will increase theTG steam turbine developed power and vice versa

All the measurement results were obtained from theexisting measuring equipment mounted on the TG turbineinlet and outlet List of all used measuring equipment ispresented in Table 3

4 Exergy Efficiency and Exergy DestructionChange duringDevelopedPowerVariation ofa TG Turbine

Change in TG steam turbine exergy efficiency and exergydestruction during the turbine developed power variationwas presented in three operating points fromTable 2mdashoperating points 3 5 and 8 Obtained conclusionsfrom these three TG steam turbine operating points are alsovalid in all the other turbine operating points

41 TG Turbine Developed Power VariationmdashOperatingPoint 3 TG steam turbine exergy efficiency change in op-erating point 3 (Table 2) during the developed power

Table 2 Measurement results for TG steam turbine in various operation regimes

Operatingpoint

Steam pressure at the TGturbine inlet (MPa)

Steam temperature at the TGturbine inlet (degC)

Steam pressure at the TGturbine outlet (MPa)

Steammass flow through TGturbine (kgh)

1 621 4910 000541 4648832 622 4910 000489 4556163 597 4905 000425 4000584 607 4910 000392 3838785 607 5025 000397 3778916 601 5045 000420 4070847 589 5015 000554 4689038 580 4930 000557 442843

Table 3 Measuring equipment for the TG steam turbineSteam temperature(TG inlet)

Greisinger GTF 601-Pt100mdashimmersionprobe [38]

Steam pressure(TG inlet)

Yamatake JTG980Amdashpressuretransmitter [39]

Steam pressure(TG outlet)

Yamatake JTD910Amdashdifferentialpressure transmitter [40]

Steam mass flow(TG inlet)



variation is shown in Figure 3 Increase in turbine developedpower firstly causes an increase in exergy efficiency until themaximum value after which follows a decrease in turbineexergy efficiency Maximum turbine exergy efficiency isobtained at power of 2700 kW (7013 of maximum turbinepower) and amounts 6818 In this operating point at thehighest turbine load of 3850 kW exergy efficiency amounts6610

Turbine exergy efficiency in each operating point as wellas in operating point 3 is calculated by using (12) An in-crease in turbine developed power causes an increase insteam mass flow through the turbine which is calculated byusing the reversed equation (6) where the turbine power isknown and steam mass flow is an unknown variable Anincrease in turbine developed power and mass flow causesa change in steam specific enthalpy at the turbine outlet (h2)and also a change in steam specific entropy at the turbineoutlet (s2)

(e most important variables which ratio defines TGturbine exergy efficiency change are turbine power and thecorresponding steam mass flow In the turbine power rangefrom 500 kW until the 2700 kW turbine exergy efficiencyincreases because the intensity of increase in turbine de-veloped power is higher in comparison with an increase insteam mass flow through the turbine In the turbine powerrange from 2700 kW until the highest turbine load of3850 kW the intensity of increase in turbine power is lowerin comparison with an increase in steam mass flow throughthe turbine so as a result in that operating area turbineexergy efficiency decreases

TG steam turbine load depends on ship electrical con-sumers and their current needs for the electrical power Inoperating point 3 TG steam turbine exergy efficiency duringLNG carrier exploitation amounts only 5687 which is themuch lower exergy efficiency than the maximum one ob-tained for this operating point To obtain higher turbineexergy efficiency in the exploitation the TG steam turbineshould be more loaded but not more than 2700 kW

TG steam turbine exergy destruction is calculated byusing (11) for each observed operating point Turbine exergy

destruction is the most influenced by steam mass flowthrough the turbine Even a small increase in steam massflow significantly increases the result of an (11) An increasein turbine developed power has much lower influence on theturbine exergy destruction change in comparison with theincrease in steam mass flow Continuous increase in steammass flow during the TG turbine developed power increasefrom 500 kW to 3850 kW causes a continuous increase inturbine exergy destruction as presented in Figure 4 (isconclusion is valid not only in operating point 3 but also inall the other TG turbine operating points

During LNG carrier exploitation in operating point 3TG steam turbine exergy destruction amounts 62882 kWwhile at TG turbine maximum exergy efficiency in thisoperating point (at turbine developed power of 2700 kW)turbine exergy destruction amounts 125982 kW At maxi-mum turbine power of 3850 kW exergy destruction is thehighest and amounts 197462 kW

TG steam turbine developed power variation showedthat exergy destruction is not proportional to the turbineexergy efficiency but is directly proportional to turbineloadmdashhigher turbine load results in the higher exergy de-struction and vice versa

Analyzed TG steam turbine exergy power inlet can bepresented as a sum of a turbine developed power steamexergy power at the turbine outlet and turbine exergy de-struction (9) It is interesting to present and compare suchdistribution of the exergy power inlet at two steam turbineoperating phases for TG steam turbine operating point 3first is a phase of exploitation and the second is a phase atwhich turbine obtained maximum exergy efficiencyFigure 3

For TG steam turbine operating point 3 steam exergypower at the turbine outlet takes a very low share in theexergy power inlet (only 4 during exploitation and 3 ata phase of maximum exergy efficiency) (e most notabledifferences between the phases of exploitation and maxi-mum exergy efficiency can be seen in shares of turbinedeveloped power and exergy destruction in the exergy powerinlet During exploitation the share of turbine developed

Turbine developed power (kW)

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500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000

Maximum exergy efficiency

Exploitation exergy efficiency

Figure 3 Steam turbine exergy efficiency change during the developed power variationmdashoperating point 3


power in the exergy power inlet is 12 lower while the shareof exergy destruction in the exergy power inlet is 11 higherin comparison with a phase of maximum exergy efficiencyFigure 5

Clearly it can be concluded that the higher share ofturbine developed power and the lower share of turbineexergy destruction in the exergy power inlet lead to higherturbine exergy efficiencies (e influence of steam exergypower at the turbine outlet on the turbine exergy efficiency isnegligible

42 TG Turbine Developed Power VariationmdashOperatingPoint 5 Change in exergy efficiency of TG turbine in op-erating point 5 (Table 2) during the developed powervariation is shown in Figure 6 As in previous operatingpoint an increase in turbine developed power causes anincrease in exergy efficiency until the maximum value afterwhich follows a decrease in turbine exergy efficiency

In operating point 5 maximum turbine exergy efficiencyis also obtained at developed power of 2700 kW andamounts 6678 For this operating point at the highest

turbine load of 3850 kW exergy efficiency amounts 6473while during LNG carrier exploitation turbine exergy effi-ciency amounts only 5479

(e reasons for such TG turbine exergy efficiency changein operating point 5 are identical as in operating point 3described earlier To obtain higher turbine exergy efficiencyin the exploitation the TG steam turbine should be moreloaded also in observed operating point 5 but the turbineload must not exceed the value of 2700 kW

Continuous increase in steammass flow during the TGturbine power increase from 500 kW to 3850 kW causesa continuous increase in turbine exergy destruction aspresented in Figure 7 also at a TG turbine operatingpoint 5 As before steam mass flow is a dominant factorwhich defines the change in TG steam turbine exergydestruction

TG steam turbine exergy destruction during LNG carrierexploitation in operating point 5 amounts 63221 kW Atmaximum exergy efficiency (2700 kW) in this operatingpoint the turbine exergy destruction amounts 134309 kWwhile at maximum turbine power of 3850 kW exergy de-struction is the highest and amounts 209761 kW


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1000

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1400

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500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000

Exergy destruction at maximum exergy efficiency

Exploitation exergy destruction

Figure 4 Steam turbine exergy destruction change during the developed power variationmdashoperating point 3

4

42

54

Steam exergy power outlet Turbine developed power Exergy destruction

(a)

66

3

31


(b)

Figure 5 Distribution of steam turbine exergy power inlet for operating point 3 in exploitation (a) and at the maximum exergy efficiency (b)


As in TG turbine operating point 3 exergy destructionin operating point 5 is directly proportional to turbineloadmdashhigher load results in the higher exergy destructionand vice versa

At turbine operating point 5 steam exergy power at theturbine outlet takes a share in the exergy power inlet lowerthan in operating point 3 analyzed before (only 3 duringexploitation and 2 at a phase of maximum exergy effi-ciency) Again the most notable differences between thephases of exploitation and maximum exergy efficiency areobtained in the shares of turbine developed power andexergy destruction in the exergy power inlet Figure 8During exploitation at TG steam turbine operating point 5the share of turbine developed power in the exergy powerinlet is 13 lower while the share of exergy destruction inthe exergy power inlet is 12 higher in comparison witha phase of maximum exergy efficiency

As for turbine operating point 3 at turbine operatingpoint 5 is also valid a conclusion that the higher share ofturbine developed power and the lower share of turbine

exergy destruction in the exergy power inlet lead to higherturbine exergy efficiencies

43 TG Turbine Developed Power VariationmdashOperatingPoint 8 (e same trends and conclusions obtained fromTG steam turbine operating points 3 and 5 during turbinedeveloped power variation are also valid for operatingpoint 8 (Table 2) In operating point 8 maximum turbineexergy efficiency amounts 7006 and as before is obtainedat turbine developed power of 2700 kW At the highestturbine load (3850 kW) in operating point 8 exergy effi-ciency amounts 6794 while during LNG carrier exploi-tation TG turbine exergy efficiency amounts only 6046Figure 9 TG steam turbine exergy efficiency during LNGcarrier exploitation is 96 lower than the maximum oneobtained in operating point 8

TG turbine operating point 8 also confirmed conclu-sion that exergy destruction is proportional to turbineloadmdashhigher load results in the higher exergy destruction


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and vice versa Figure 10 In operating point 8 TG steamturbine exergy destruction during LNG carrier exploitationamounts 62186 kW at maximum exergy efficiency turbineexergy destruction amounts 115388 kW while at maximumturbine power of 3850 kW exergy destruction is the highestand amounts 181685 kW

Steam exergy power at the turbine outlet in operatingpoint 8 has sensibly higher share in the exergy power inletwhen compared with operating points 3 and 5 and itamounts 6 in both exploitation and at maximum turbineexergy efficiency phase Figure 11 TG steam turbine op-erating point 8 does not deviate when compared withoperating points 3 and 5mdashthe most notable differencesbetween the phases of exploitation and maximum exergyefficiency can be seen in shares of turbine developed powerand exergy destruction in the exergy power inlet In a phaseof maximum exergy efficiency the share of turbine de-veloped power in the exergy power inlet is 9 higher whilethe share of exergy destruction in the exergy power inlet is

9 lower in comparison with the exploitation phaseFigure 11

(e same conclusion follows from all three analyzedturbine operating points (operating points 3 5 and 8)mdashthehigher share of turbine developed power and the lower shareof turbine exergy destruction in the exergy power inlet leadto higher turbine exergy efficiencies and vice versa (isconclusion is also valid for all the other TG steam turbineoperating points presented in Table 2

5 Comparison of Steam Turbine ExergyEfficiency and Exergy Destruction for AllObserved Operating Points(Exploitation versus Maximum ExergyEfficiency Phase)

In this section is presented a comparison of TG steamturbine exergy efficiencies and exergy destructions at two

3

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(b)



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operating phasesmdashduring the exploitation and during thephase of maximum exergy efficiency obtained by turbinedeveloped power variation (e comparison is presented forall TG steam turbine analyzed operating points from Table 2

For all observed TG steam turbine operating points isvalid a conclusion that maximum turbine exergy efficiencywill be obtained at turbine developed power of 2700 kW Inoperating point 7 turbine exergy efficiency in exploitation isthe closest to themaximum possible one and the difference is839 (exploitation exergy efficiency in operating point 7amounts 6092 while the maximum exergy efficiency forthis turbine operating point is 6971) For turbine oper-ating points 4 and 5 exploitation exergy efficiencies are thefarthest from the maximum obtained onesmdashdifference is1199 for operating point 5 and 1203 for operatingpoint 4 Figure 12

(e highest turbine exergy efficiencies for exploitationare obtained in operating points 1 and 7 (6095 for op-erating point 1 and 6092 for operating point 7) while thehighest turbine exergy efficiencies obtained by turbine de-veloped power variation are 6967 for operating point 1and 7006 for operating point 8

When compared exergy destructions of TG steam tur-bine in all observed operating points from Table 2 it can beseen that turbine exergy destruction is much lower at theexploitation phase in comparison with the phase of maxi-mum exergy efficiency Figure 13

(e lowest difference in the analyzed turbine exergydestruction between exploitation and maximum exergy ef-ficiency phase can be seen in operating point 1 and amounts52591 kW (at operating point 1 turbine exergy destruction inexploitation amounts 64970 kW while for the same oper-ating point at a phase of maximum exergy efficiency turbineexergy destruction amounts 117561 kW) (e highest dif-ference in the analyzed turbine exergy destruction betweenexploitation and maximum exergy efficiency phase is ob-tained in operating point 5 and amounts 71088 kW Fig-ure 13 (e average difference in turbine exergy destructionbetween exploitation and maximum exergy efficiency phasefor all eight observed operating points amounts 60455 kW

(e value of turbine exergy destruction is not the onlyvariable which defines turbine exergy efficiency valueAccording to (12) turbine exergy efficiency is depended onthe ratio of turbine developed power and turbine exergy


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destruction (turbine exergy destruction is the most influ-enced with a steam mass flow through the turbine) Whenturbine developed power increases with a higher intensity incomparison with increase in turbine exergy destruction(increase in turbine exergy destruction is proportional toincrease in steam mass flow)mdashturbine exergy efficiency willincrease (erefore an increase in turbine exergy de-struction does not have to reduce turbine exergy efficiencysimultaneously moreover for the analyzed TG steam tur-bine increase in turbine developed power up to 2700 kWwill be resulted in a simultaneous increase in turbine exergydestruction and exergy efficiency

6 Conclusions

Numerical analysis of TG steam turbine exergy efficiencyand exergy destruction (exergy power losses) change duringthe variation in turbine developed power was presented inthis paper TG steam turbine operates in the conventionalLNG carrier steam propulsion system Measurements were

performed in eight different TG steam turbine operatingpoints and detailed analysis is presented for three randomlyselected operating points but major conclusions are valid forthe entire TG turbine operating range

Analyzed TG steam turbine exergy efficiency increasesfrom 500 kW to 2700 kW of developed power and maxi-mum exergy efficiency was obtained at 7013 of maximumturbine power (at 2700 kW) in each observed operatingpoint From 2700 kW until the maximum of 3850 kW TGturbine exergy efficiency decreases Increase and decrease inTG turbine exergy efficiency are caused by an uneven in-tensity of increase in turbine developed power and steammass flow (e recommendation is that in exploitation theTG steam turbine should be more loaded to achieve higherexergy efficiency but the turbine load must not exceed thevalue of 2700 kW

TG steam turbine exergy destruction is proportional toturbine load while turbine load is proportional to steammass flow through the turbinemdashhigher steam mass flowresults in a higher load which leads to the higher exergy

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1 2 3 4 5 6 7 8

Exploitation

Analyzed operating point (Table 2)

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()


Figure 12 Comparison of exergy efficiencies for all analyzed operating pointsmdashexploitation versus maximum exergy efficiency phase

400500600700800900

10001100120013001400

1 2 3 4 5 6 7 8

ExploitationMaximum exergy efficiency


Exer

gy d

estr

uctio

n (k

W)

Figure 13 Comparison of exergy destructions for all analyzed operating pointsmdashexploitation versus maximum exergy efficiency phase


destruction and vice versa (e lowest TG turbine exergydestruction is obtained at the lowest observed turbine loadwhile the highest exergy destruction is obtained at thehighest turbine load in each operating point (e mainreason for continuous increase in turbine exergy destructionduring the developed turbine power increase is found incontinuous increases in steam mass flow through the tur-bine Even a small increase in steam mass flow significantlyincreases the turbine exergy destruction

It was also investigated the distribution of turbine exergypower inlet for three randomly selected operating points(e major conclusion from the turbine exergy power inletdistribution analysis is that the higher share of turbinedeveloped power and the lower share of turbine exergydestruction in the exergy power inlet lead to higher turbineexergy efficiencies and vice versa (e influence of steamexergy power at the turbine outlet on the turbine exergyefficiency change is negligible

At each observed operating point turbine exergy effi-ciency in LNG carrier exploitation is lower from 839 to1203 when compared to the maximum obtained one bythis analysis For all of the observed TG steam turbineoperating points exergy destruction in exploitation is lowerbetween 52591 kW and 71088 kW in comparison withmaximum exergy efficiency phase

(is analysis can be helpful to ship crew not only on theanalyzed LNG carrier but also on other similar LNG carrierswith similar turbogenerator units to optimize their opera-tion and achieve the highest possible exergy efficiencies ineach TG steam turbine operating point

NomenclatureGreek symbolsε Specific exergy (kJkg)η Efficiency (ndash)AbbreviationsLNG Liquefied natural gasTG TurbogeneratorSubscripts0 Ambient stateD Destructionex ExergyIN InletOUT Outlet_E Stream flow power (kJs)

h Specific enthalpy (kJkg)_m Mass flow rate (kgs or kgh)p Pressure (MPa)P Power (kJs)_Q Heat transfer (kJs)

s Specific entropy (kJkgmiddotK)_Xheat Heat exergy transfer (kJs)T Temperature (degC or K)

Conflicts of Interest

(e authors declare that there are no conflicts of interestregarding the publication of this article

Acknowledgments

(e authors would like to extend their appreciations to themain ship-owner office for conceding measuring equipmentand for all help during the exploitation measurements (iswork was supported by the University of Rijeka (Contractno 13091105)

References

[1] I A Fernandez M R Gomez J R Gomez and A A B InsualdquoReview of propulsion systems on LNG carriersrdquo Renewableand Sustainable Energy Reviews vol 67 pp 1395ndash1411 2017

[2] A J Murphy A J Norman K Pazouki and D G Troddenldquo(ermodynamic simulation for the investigation of marineDiesel enginesrdquo Ocean Engineering vol 102 pp 117ndash1282015

[3] V Mrzljak V Medica and O Bukovac ldquoSimulation of a two-stroke slow speed diesel engine using a quasi-dimensionalmodelrdquo Transactions of Famena vol 40 no 2 pp 35ndash442016

[4] D Singh K A Subramanian and M O Garg ldquoCompre-hensive review of combustion performance and emissionscharacteristics of a compression ignition engine fueled withhydroprocessed renewable dieselrdquo Renewable and SustainableEnergy Reviews vol 81 pp 2947ndash2954 2018

[5] M N Nabi A Zare F M Hossain Z D Ristovski andR J Brown ldquoReductions in diesel emissions including PMand PN emissions with diesel-biodiesel blendsrdquo Journal ofCleaner Production vol 166 pp 860ndash868 2017

[6] O Schinas and M Butler ldquoFeasibility and commercial con-siderations of LNG-fueled shipsrdquoOcean Engineering vol 122pp 84ndash96 2016

[7] G R Ahmadi and D Toghraie ldquoEnergy and exergy analysis ofMontazeri steam power plant in Iranrdquo Renewable and Sus-tainable Energy Reviews vol 56 pp 454ndash463 2016

[8] V Mrzljak I Poljak and V Medica-Viola ldquoDual fuel con-sumption and efficiency of marine steam generators for thepropulsion of LNG carrierrdquo Applied 6ermal Engineeringvol 119 pp 331ndash346 2017

[9] E Keshavarz D Toghraie and M Haratian ldquoModeling in-dustrial scale reaction furnace using computational fluiddynamics a case study in Ilam gas treating plantrdquo Applied6ermal Engineering vol 123 pp 277ndash289 2017

[10] D A Taylor Introduction to Marine Engineering ElsevierButterworth-Heinemann Oxford UK 1998

[11] V Mrzljak I Poljak and T Mrakovcic ldquoEnergy and exergyanalysis of the turbo-generators and steam turbine for themain feed water pump drive on LNG carrierrdquo Energy Con-version and Management vol 140 pp 307ndash323 2017

[12] S Adibhatla and S C Kaushik ldquoEnergy and exergy analysis ofa super critical thermal power plant at various load conditionsunder constant and pure sliding pressure operationrdquo Applied6ermal Engineering vol 73 no 1 pp 51ndash65 2014

[13] S Adibhatla and S C Kaushik ldquoExergy and thermoeconomicanalyses of 500 MWe sub critical thermal power plant withsolar aided feed water heatingrdquo Applied 6ermal Engineeringvol 123 pp 340ndash352 2017

[14] V Medica-Viola B Pavkovic and V Mrzljak ldquoNumericalmodel for on-condition monitoring of condenser in coal-firedpower plantsrdquo International Journal of Heat and MassTransfer vol 117 pp 912ndash923 2018

[15] M Baawain B S Choudri M Ahmed and A PurnamaRecent Progress in Desalination Environmental and Marine


Outfall Systems Springer International Publishing BaselSwitzerland 2015

[16] V Mrzljak I Poljak and V Medica-Viola ldquoEnergy andexergy efficiency analysis of sealing steam condenser inpropulsion system of LNG carrier our seardquo InternationalJournal of Maritime Science and Technology vol 64 no 1pp 20ndash25 2017

[17] V Mrzljak I Poljak and V Medica-Viola ldquoEfficiency andlosses analysis of low-pressure feed water heater in steampropulsion system during ship maneuvering periodrdquo Scien-tific Journal of Maritime Research vol 30 pp 133ndash140 2016

[18] V Mrzljak I Poljak and V Medica-Viola ldquo(ermody-namical analysis of high-pressure fed water heater in steampropulsion system during exploitation shipbuilding theoryand practice of naval architecturerdquo Marine Engineering andOcean Engineering vol 68 no 2 pp 45ndash61 2017

[19] M Samadifar and D Toghraie ldquoNumerical simulation of heattransfer enhancement in a plate-fin heat exchanger usinga new type of vortex generatorsrdquo Applied 6ermal Engi-neering vol 133 pp 671ndash681 2018

[20] M H Esfe H Hajmohammad D Toghraie H RostamianO Mahian and S Wongwises ldquoMulti-objective optimizationof nanofluid flow in double tube heat exchangers for appli-cations in energy systemsrdquo Energy vol 137 pp 160ndash171 2017

[21] G R Ahmadi and D Toghraie ldquoParallel feed water heatingrepowering of a 200 MW steam power plantrdquo Journal ofPower Technologies vol 95 pp 288ndash301 2015

[22] H Kavusi and D Toghraie ldquoA comprehensive study of theperformance of a heat pipe by using of various nanofluidsrdquoAdvanced Powder Technology vol 28 no 11 pp 3074ndash30842017

[23] A Moraveji and D Toghraie ldquoComputational fluid dynamicssimulation of heat transfer and fluid flow characteristics ina vortex tube by considering the various parametersrdquo In-ternational Journal of Heat and Mass Transfer vol 113pp 432ndash443 2017

[24] H P Bloch and M P Singh Steam Turbines-Design Appli-cations and Re-Rating (e McGraw- Hill Companies IncNew York NY USA 2nd edition 2009

[25] F Baldi F Ahlgren F Melino C Gabrielii andK Andersson ldquoOptimal load allocation of complex shippower plantsrdquo Energy Conversion and Management vol 124pp 344ndash356 2016

[26] F Haglind ldquoVariable geometry gas turbines for improving thepart-load performance of marine combined cycles-combinedcycle performancerdquo Applied 6ermal Engineering vol 31no 4 pp 467ndash476 2011

[27] M Kanoglu Y A Ccedilengel and I Dincer ldquoEfficiency evalu-ation of energy systemsrdquo in Springer Briefs in EnergySpringer Berlin Germany 2012

[28] F K Zisopoulos S N Moejes F J Rossier-MirandaA J Van der Goot and RM Boom ldquoExergetic comparison offood waste valorization in industrial bread productionrdquoEnergy vol 82 pp 640ndash649 2015

[29] N Nazari P Heidarnejad and S Porkhial ldquoMulti-objectiveoptimization of a combined steam-organic Rankine cyclebased on exergy and exergo-economic analysis for waste heatrecovery applicationrdquo Energy Conversion and Managementvol 127 pp 366ndash379 2016

[30] G Ahmadi D Toghraie A Azimian and O Ali AkbarildquoEvaluation of synchronous execution of full repowering andsolar assisting in a 200 MW steam power plant a case studyrdquoApplied 6ermal Engineering vol 112 pp 111ndash123 2017

[31] G Ahmadi D Toghraie and O Ali Akbari ldquoSolar parallelfeed water heating repowering of a steam power plant a casestudy in Iranrdquo Renewable and Sustainable Energy Reviewsvol 77 pp 474ndash485 2017

[32] J Szargut Exergy Method-Technical and Ecological Applica-tions WIT Press Ashurst UK 2005

[33] Shinko Ind Ltd Final Drawing for Generator Turbine ShinkoInd Ltd Hiroshima Japan 2006

[34] E W Lemmon M L Huber and M O McLinden NISTReference Fluid 6ermodynamic and Transport Properties-REFPROP Version 80 Userrsquos Guide NIST Boulder COUSA 2007

[35] H H Erdem A V Akkaya B Cetin et al ldquoComparativeenergetic and exergetic performance analyses for coal-firedthermal power plants in Turkeyrdquo International Journal of6ermal Sciences vol 48 no 11 pp 2179ndash2186 2009

[36] S C Kaushik V Siva Reddy and S K Tyagi ldquoEnergy andexergy analyses of thermal power plants a reviewrdquo Renewableand Sustainable Energy Reviews vol 15 no 4 pp 1857ndash18722011

[37] F Hafdhi T Khir A Ben Yahyia and A Ben BrahimldquoEnergetic and exergetic analysis of a steam turbine powerplant in an existing phosphoric acid factoryrdquo Energy Con-version and Management vol 106 pp 1230ndash1241 2015

[38] httpswwwgreisingerde[39] httpwwwindustriascontrolprocom[40] httpwwwkrtproductcom


International Journal of

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Submit your manuscripts atwwwhindawicom

is analyzed in this paper from the aspect of exergy efficiencyand exergy power losses (exergy destruction) during theincrease in turbine developed power Along with the mainpropulsion turbine and two turbogenerator steam turbinesthe majority of steam propulsion systems on LNG carriershave also one low-power steam turbine for the main feed-water pump drive as can be found in several land-basedsteam power systems [12 13] Low-power steam turbinefor the main feedwater pump drive is backpressure steamturbinemdashsteam after expansion in this turbine is used insome other marine steam system components After ex-pansion in the main propulsion turbine and turbogenera-tors steam was led to the main marine condenser onliquefaction Main marine condenser operation differs greatlyin comparison with main condensers from land-based steampower systems [14] because cooling water (sea) is brought toa main marine steam condenser with pumps at low systemloads after which follows a sea accumulation system (scoop) athigh steam system loads

Condensate and feedwater return channel from the mainmarine condenser to steam generators has several deviceswhich provide water heating (e first of such devices afterthe main condenser is evaporator (freshwater generator)[15] the marine steam system component which is notrequired in land-based steam power systems After evapo-rator is located sealing steam condenser [16] and usually twocondensate and feedwater heaters (low-pressure condensateheater [17] before deaerator and high-pressure feedwaterheater [18] after deaerator) In comparison with land-basedsteam power systems marine steam system has always muchlower number of condensate and feedwater heaters becauseof limited ship space On water return channel is alsomounted hot well for collecting all the condensate from thesystem Condensate and feedwater heating system in land-based steam power systems as well as in marine steampropulsion systems is the most appropriate for variousimprovements [19] and optimizations [20] in order to re-duce fuel consumption and thus emissions from steamgenerators [21] New investigations for improving heattransfer as reported in [22] or [23] can surely be applied inmarine steam propulsion systems at several heat exchangersnot only at condensate and feedwater heaters

(e analyzed LNG carrier has two identical turbogen-erator sets that operate in parallel Each TG steam turbinehas identical operating parameters (inlet and outlet steamtemperatures pressures andmass flows) and for the analysisin this paper is selected one of them Steam turbine for eachelectric generator drive comprises nine Rateau stages Steamturbines with Rateau stages and their analysis can be foundin [24] Many details of the classic and special designs ofmarine steam turbines and their auxiliary systems arepresented in [25] and [26]

(e main goal of this analysis was to obtain the optimaloperating area of the TG steam turbine in which will beachieved maximum exergy efficiencies and minimum exergydestructions for every turbine operating point As a knownparameter is taken a TG turbine developed power which was

varied from 500 kW up to maximum turbine developedpower of 3850 kW in steps of 100 kW For each TG turbinedeveloped power turbine exergy efficiency and exergy de-struction were calculated Obtained areas of turbine maxi-mum exergy efficiency and minimum exergy destructionwere compared with the real LNG carrier exploitation(according to measured operating parameters) (e mainconclusion of TG steam turbine exergy analysis is that inexploitation turbine should be more loaded to obtain higherexergy efficiency in each operating point but it would not beadvisable that turbine operates at maximum load (at3850 kW) TG turbine exergy destruction change does notfollow the exergy efficiency trends so from the viewpoint ofturbine exergy destruction it would not be advisable thatturbine operates in the same operating areas as for maxi-mum exergy efficiency(e distribution of TG steam turbineexergy power inlet shows that the higher share of turbinedeveloped power and the lower share of turbine exergydestruction in exergy power inlet lead to higher turbineexergy efficiencies

Main characteristics of the LNG carrier in which steampropulsion system is mounted analyzed turbogeneratorsteam turbine are presented in Table 1

2 TG Steam Turbine Exergy Analysis

21 Equations for the Exergy Analysis Exergy analysis isbased on the second law of thermodynamics [27] (e mainexergy balance equation for a standard volume in steadystate is [28 29]

_Xheat minusP 1113944 _mOUT middot εOUT minus 1113944 _mIN middot εIN + _EexD (1)

where the net exergy transfer by heat ( _Xheat) at the tem-perature T is equal to [30]

_Xheat 1113944 1minusT0

T1113874 1113875 middot _Q (2)

Specific exergy was defined according to [8 31] by thefollowing equation

ε hminus h0( 1113857minusT0 middot sminus s0( 1113857 (3)

(e total exergy of a flow for every fluid stream can becalculated according to [11]

_Eex _m middot ε _m middot hminus h0( 1113857minusT0 middot sminus s0( 11138571113858 1113859 (4)

Table 1 Main characteristics of the LNG carrierDeadweight tonnage 84812 DWTOverall length 288mMaximum breadth 44mDesign draft 93mSteam generators 2timesMitsubishi MB-4E-KS

Propulsion turbine Mitsubishi MS40-2(maximum power 29420 kW)

Turbogenerators 2times Shinko RGA 92-2(maximum power 3850 kW each)




(5)




2TG

+ 0251318 middot _mTG minus 256863(6)






h2 h1 minusPTG_mTG

(8)















Steam turbine

Electric generator

(mTG h1 s1)

(mTG h2 s2)


Saturation line

1

2

2s

p1

p2

t1



h

s





ηTGex PTG



(12)

















Operatingpoint





1 621 4910 000541 4648832 622 4910 000489 4556163 597 4905 000425 4000584 607 4910 000392 3838785 607 5025 000397 3778916 601 5045 000420 4070847 589 5015 000554 4689038 580 4930 000557 442843





















Exer

gy ef

ficie

ncy

()

49

51

53

55

57

59

61

63

65

67

69

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000














Exer

gy d

estr

uctio

n (k

W)

400

600

800

1000

1200

1400

1600

1800

2000

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000




4

42

54


(a)

66

3

31


(b)










Exer

gy ef

ficie

ncy

()

48

50

52

54

56

58

60

62

64

66

68

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000





Exer

gy d

estr

uctio

n (k

W)

500

700

900

1100

1300

1500

1700

1900

2100

2300

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000











3

44

53


53

(a)

66

2

32


(b)



Exer

gy ef

ficie

ncy

()

49

51

53

55

57

59

61

63

65

67

69

71

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000












Exer

gy d

estr

uctio

n (k

W)

400

600

800

1000

1200

1400

1600

1800

2000

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000




6

37

57


(a)

66

6

28


(b)




6 Conclusions





54

56

58

60

62

64

66

68

70

72

1 2 3 4 5 6 7 8

Exploitation


Exer

gy ef

ficie

ncy

()



400500600700800900

10001100120013001400

1 2 3 4 5 6 7 8



Exer

gy d

estr

uctio

n (k

W)












Acknowledgments


References












































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia




(5)




2TG

+ 0251318 middot _mTG minus 256863(6)






h2 h1 minusPTG_mTG

(8)















Steam turbine

Electric generator

(mTG h1 s1)

(mTG h2 s2)


Saturation line

1

2

2s

p1

p2

t1



h

s





ηTGex PTG



(12)

















Operatingpoint





1 621 4910 000541 4648832 622 4910 000489 4556163 597 4905 000425 4000584 607 4910 000392 3838785 607 5025 000397 3778916 601 5045 000420 4070847 589 5015 000554 4689038 580 4930 000557 442843





















Exer

gy ef

ficie

ncy

()

49

51

53

55

57

59

61

63

65

67

69

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000














Exer

gy d

estr

uctio

n (k

W)

400

600

800

1000

1200

1400

1600

1800

2000

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000




4

42

54


(a)

66

3

31


(b)










Exer

gy ef

ficie

ncy

()

48

50

52

54

56

58

60

62

64

66

68

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000





Exer

gy d

estr

uctio

n (k

W)

500

700

900

1100

1300

1500

1700

1900

2100

2300

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000











3

44

53


53

(a)

66

2

32


(b)



Exer

gy ef

ficie

ncy

()

49

51

53

55

57

59

61

63

65

67

69

71

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000












Exer

gy d

estr

uctio

n (k

W)

400

600

800

1000

1200

1400

1600

1800

2000

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000




6

37

57


(a)

66

6

28


(b)




6 Conclusions





54

56

58

60

62

64

66

68

70

72

1 2 3 4 5 6 7 8

Exploitation


Exer

gy ef

ficie

ncy

()



400500600700800900

10001100120013001400

1 2 3 4 5 6 7 8



Exer

gy d

estr

uctio

n (k

W)












Acknowledgments


References












































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia




ηTGex PTG



(12)

















Operatingpoint





1 621 4910 000541 4648832 622 4910 000489 4556163 597 4905 000425 4000584 607 4910 000392 3838785 607 5025 000397 3778916 601 5045 000420 4070847 589 5015 000554 4689038 580 4930 000557 442843





















Exer

gy ef

ficie

ncy

()

49

51

53

55

57

59

61

63

65

67

69

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000














Exer

gy d

estr

uctio

n (k

W)

400

600

800

1000

1200

1400

1600

1800

2000

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000




4

42

54


(a)

66

3

31


(b)










Exer

gy ef

ficie

ncy

()

48

50

52

54

56

58

60

62

64

66

68

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000





Exer

gy d

estr

uctio

n (k

W)

500

700

900

1100

1300

1500

1700

1900

2100

2300

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000











3

44

53


53

(a)

66

2

32


(b)



Exer

gy ef

ficie

ncy

()

49

51

53

55

57

59

61

63

65

67

69

71

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000












Exer

gy d

estr

uctio

n (k

W)

400

600

800

1000

1200

1400

1600

1800

2000

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000




6

37

57


(a)

66

6

28


(b)




6 Conclusions





54

56

58

60

62

64

66

68

70

72

1 2 3 4 5 6 7 8

Exploitation


Exer

gy ef

ficie

ncy

()



400500600700800900

10001100120013001400

1 2 3 4 5 6 7 8



Exer

gy d

estr

uctio

n (k

W)












Acknowledgments


References












































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia













Exer

gy ef

ficie

ncy

()

49

51

53

55

57

59

61

63

65

67

69

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000














Exer

gy d

estr

uctio

n (k

W)

400

600

800

1000

1200

1400

1600

1800

2000

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000




4

42

54


(a)

66

3

31


(b)










Exer

gy ef

ficie

ncy

()

48

50

52

54

56

58

60

62

64

66

68

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000





Exer

gy d

estr

uctio

n (k

W)

500

700

900

1100

1300

1500

1700

1900

2100

2300

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000











3

44

53


53

(a)

66

2

32


(b)



Exer

gy ef

ficie

ncy

()

49

51

53

55

57

59

61

63

65

67

69

71

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000












Exer

gy d

estr

uctio

n (k

W)

400

600

800

1000

1200

1400

1600

1800

2000

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000




6

37

57


(a)

66

6

28


(b)




6 Conclusions





54

56

58

60

62

64

66

68

70

72

1 2 3 4 5 6 7 8

Exploitation


Exer

gy ef

ficie

ncy

()



400500600700800900

10001100120013001400

1 2 3 4 5 6 7 8



Exer

gy d

estr

uctio

n (k

W)












Acknowledgments


References












































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia











Exer

gy d

estr

uctio

n (k

W)

400

600

800

1000

1200

1400

1600

1800

2000

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000




4

42

54


(a)

66

3

31


(b)










Exer

gy ef

ficie

ncy

()

48

50

52

54

56

58

60

62

64

66

68

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000





Exer

gy d

estr

uctio

n (k

W)

500

700

900

1100

1300

1500

1700

1900

2100

2300

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000











3

44

53


53

(a)

66

2

32


(b)



Exer

gy ef

ficie

ncy

()

49

51

53

55

57

59

61

63

65

67

69

71

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000












Exer

gy d

estr

uctio

n (k

W)

400

600

800

1000

1200

1400

1600

1800

2000

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000




6

37

57


(a)

66

6

28


(b)




6 Conclusions





54

56

58

60

62

64

66

68

70

72

1 2 3 4 5 6 7 8

Exploitation


Exer

gy ef

ficie

ncy

()



400500600700800900

10001100120013001400

1 2 3 4 5 6 7 8



Exer

gy d

estr

uctio

n (k

W)












Acknowledgments


References












































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia









Exer

gy ef

ficie

ncy

()

48

50

52

54

56

58

60

62

64

66

68

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000





Exer

gy d

estr

uctio

n (k

W)

500

700

900

1100

1300

1500

1700

1900

2100

2300

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000











3

44

53


53

(a)

66

2

32


(b)



Exer

gy ef

ficie

ncy

()

49

51

53

55

57

59

61

63

65

67

69

71

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000












Exer

gy d

estr

uctio

n (k

W)

400

600

800

1000

1200

1400

1600

1800

2000

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000




6

37

57


(a)

66

6

28


(b)




6 Conclusions





54

56

58

60

62

64

66

68

70

72

1 2 3 4 5 6 7 8

Exploitation


Exer

gy ef

ficie

ncy

()



400500600700800900

10001100120013001400

1 2 3 4 5 6 7 8



Exer

gy d

estr

uctio

n (k

W)












Acknowledgments


References












































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia








3

44

53


53

(a)

66

2

32


(b)



Exer

gy ef

ficie

ncy

()

49

51

53

55

57

59

61

63

65

67

69

71

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000












Exer

gy d

estr

uctio

n (k

W)

400

600

800

1000

1200

1400

1600

1800

2000

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000




6

37

57


(a)

66

6

28


(b)




6 Conclusions





54

56

58

60

62

64

66

68

70

72

1 2 3 4 5 6 7 8

Exploitation


Exer

gy ef

ficie

ncy

()



400500600700800900

10001100120013001400

1 2 3 4 5 6 7 8



Exer

gy d

estr

uctio

n (k

W)












Acknowledgments


References












































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia









Exer

gy d

estr

uctio

n (k

W)

400

600

800

1000

1200

1400

1600

1800

2000

500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000




6

37

57


(a)

66

6

28


(b)




6 Conclusions





54

56

58

60

62

64

66

68

70

72

1 2 3 4 5 6 7 8

Exploitation


Exer

gy ef

ficie

ncy

()



400500600700800900

10001100120013001400

1 2 3 4 5 6 7 8



Exer

gy d

estr

uctio

n (k

W)












Acknowledgments


References












































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



6 Conclusions





54

56

58

60

62

64

66

68

70

72

1 2 3 4 5 6 7 8

Exploitation


Exer

gy ef

ficie

ncy

()



400500600700800900

10001100120013001400

1 2 3 4 5 6 7 8



Exer

gy d

estr

uctio

n (k

W)












Acknowledgments


References












































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia











Acknowledgments


References












































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia





























RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia




RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia


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