International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 13 Issue: 06 | Jun 2026 www.irjet.net p-ISSN: 2395-0072
A Review on Diesel–Gaseous Fuel Dual-Fuel Generator Sets: Performance, Retrofitting, Emissions and Operational Challenges
Raj Vaidya
1
, Ankush Kumar Bhagat
2
, Jaykumar Davra3
1Student, Mechanical Engineering, BVM Engineering College, Gujarat
2Student,MechanicalEngineering,BVMEngineeringCollege,Gujarat
3Assistant Engineer (Production), ONGC Ankleshwar Asset, Gujarat
Abstract – Diesel Generator sets are deployed in most of industries for power generationbut due to rising fuel costs and stricter emission norms the focus is now shifting to dual fuel technologies. This paper consists review of 30 research papers focusing on dual fuel technology for diesel powered gensets using fuels like Natural Gas (CNG/LNG), Biogas, Liquified Petroleum Gas (LPG), syngas and producer gas in combination of diesel pilot fuel. The review is organized around five principal themes: retrofitting methodologies, emission analysis, performance, economic feasibility and operational challenges The surveyed literature consistently demonstrates that gaseous fuel substitutionof 50–95% is achievable without major engine modifications, with brake thermal efficiency improvements of up to 42% and significant reductions in smoke opacity (up to 95%), CO₂ (20–30%), andNOx (50–87%) under optimized conditions. Studies also highlighted role of exhaust gas recirculation (EGR), pilot fuel optimization, injection timing and air management techniques in improving overall generator performance. However recurring challenges include CO emission, Unburned hydrocarbon (UHC) emissions at low load conditions and methane slip in NG systems. The review identifies technically feasible andeconomical approach for cleaner and suitable power generation applications.
Key Words: Dual fuel Generator, Diesel Generator sets, LPG, Producer Gas, Natural Gas, Brake Thermal efficiency, Emissions, Retrofitting, Power Generation
1. INTRODUCTION
DieselGeneratorSetsarewidelyusedforpowergeneration, standby, and emergency conditions in industrial facilities, hospitals, telecommunication infrastructure, construction areasandalsousedinoilfieldsandremotelocationswhere gridaccessisunstable.DieselGeneratorsarebackbonefor powerbackupanddistributedpowergenerationbecauseof theirrobustness,reliability,easeofoperationsandabilityto performundervaryingloadconditions.Howeverrisingfuel prices,environmentalconcerns,Greenhousegasemissions and stricter norms calls for adoption of cleaner and economically feasible alternatives to diesel power generationsystems.
DualFuelTechnologyhasemergedasmostpracticalsolution whichprovidesfuelflexibilitywithoutomittinghighthermal efficiency and reliability provided by diesel fuel. Dual fuel
technologyusesgaseousfuelslikeCompressedNaturalGas (CNG),LiquifiedPetroleumGas(LPG),LiquefiedNaturalGas (LNG),Producergas,SyngasorBiogasasprimaryfuelsand diesel as pilot fuel The gaseous fuel is inducted into the intake air charge and ignited by a small quantity of pilot diesel, preserving the fundamental compression-ignition mechanismwhilesubstantiallyreducingdieseldependency. Thistechnologyprovidesarrangementtopartiallyreplace dieselwithoutextensivemodificationstothebaseengineso it is a valuable option for both new installations and retrofittingofgeneratorsets.
The research has reported diesel substitution up to 95% with brake thermal efficiency has been improved up to 43%under optimized operating conditions and significant reductioninNOx,CO₂andparticulatematter butthereare challenges like methane slip in natural gas which leads to incomplete combustion and less power, increase in hydrocarbonandcarbonmonoxide emissions atpartload conditions, ignitiondelaywhichrequiresadvancedinjection technologiestobeimplemented.
The growing availability of natural gas infrastructure, increasing interest in biomass derived fuels and need for cleanerfuelshaveacceleratedresearchondualfuelsystems. Therefore, this review paper presents comprehensive assessment of dual fuel generator systems working on diesel-gaseous fuels. This literature review contains 31 researchpapers from2006-2025whichevaluatescurrent stateoftechnologyandcategorizedintofivemaincategories namelyretrofittingandconversionmethods,performance characteristics, emission behaviors, economical feasibility andoperationalchallenges.Themainobjectiveofthisreview paper is to identify research gaps by evaluating current trendsinfieldofdualfuelgeneratortechnologiestoprovide baseforfutureresearchanddevelopment.
2. REVIEW METHODOLOGY
Thisreviewwasconductedthroughsystematicresearchof articles available on academic databases Google Scholar, ResearchGate,Scopus,andScienceDirect.Searchtermsused includedcombinationsofkeywordssuchasdualfuelengine, dieselgeneratordualfuel,naturalgasdieselgenerator,LPG diesel engine, producer gasgenset, biogas diesel dual fuel, retrofitting diesel genset, and dual fuel emissions. This
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 13 Issue: 06 | Jun 2026 www.irjet.net p-ISSN: 2395-0072
research was limited to English language papers and ones whichare translated toEnglish byauthors or publications covering experimental studies, simulation-based analysis, feasibilityassessments,andtechnicalreviewsrelatedtodualfuelgeneratorsetoperation.
Fromtheinitialpool ofarticlesreviewedarticlesbasedon stationery generator sets operations, dual fuel emissions usinggaseousfuels,challengeswithusinggaseous fuelsin dual fuel systems and dual fuel economic analysis were chosen.Papersfocusedonautomotiveapplicationswhichcan serve as strong base for emission and conversion analysis werealsochosen.Basedonthisprocess30papersspanning from2006-2025wereconsideredfordetailedreview.
The selected papers were systematically organized into a literaturematrixcapturingkeyattributesincludingauthor, yearofpublication,enginespecifications,fuelcombination, keyfindings,andidentifiedlimitations.Thismatrixservedas thestructuralfoundationforthethematicanalysispresented inSections3through7ofthispaper.
3. RETROFITTING
Retrofittingalreadyexistingdieselgeneratorsetsseemslike cost effective pathway for decreasing diesel dependency without major modifications. This requires a system to introducegaseousfuelinintakeairstreamofenginewhile retaining diesel injection as pilot fuel thereby preserving compressionignitionmethodwithoutmajormodificationsto structureofdieselengine.
Thereviewedliteratureshowsthatdual-fuelconversionof existingdieselgeneratorsetsistechnicallyfeasibleacross differentenginesizesandscales.Atthesmall-enginelevel, Tiwari [4] achieved50–70%dieselsubstitutionusingCNG withoutmajorenginemodifications,whileIsmailetal.[7] developed an ECU-based CNG–diesel conversion kit that avoidedenginedisassembly.Atthelarge-scalelevel,Kabeyi and Olanrewaju [17] demonstrated that converting a 120 MWdieselpowerplanttodual-fueloperationistechnically andeconomicallymoreviablethanfullreplacement.Across all studies, reliable gaseous fuel supply and proper gas infrastructureemergedaskeyrequirementsforsuccessful retrofitting.
4. COMBUSTION AND THERMAL PERFORMANCE
ThecombustioncharacteristicsandThermalperformanceof dual fuel operation depend on type of gaseous fuel used, proportionofdieselpilotfuel,enginespeed,loadconditions and air fuel ratio management. Understanding of these parametersarecriticaltooptimizethedualfuelsystem. Thereviewedstudiesrevealthatnaturalgas-dieseldual-fuel operation consistently achieves the highest brake thermal efficiency improvements, with papers [13] and [21] reportingBTEvaluesofupto42%and43.1%respectively
under optimized high-load conditions. Producer gas-diesel systems,whileachievingsignificantdieselsubstitutionofup to52.7% [6],showanotabledeclineinelectricalefficiency due to the low calorific value of producer gas displacing intakeaircharge.Paper[9] identifiedanoptimumpilotdiesel quantityof6–11mgpercyclewithanairexcessratioof1.3–1.45ascriticalformaximizingfueleconomyinheavy-duty naturalgas-dieselengines.Aconsistentobservationacross the literature is that dual-fuel performance improves significantlyathighloads,whilepart-loadoperationremains a persistent challenge due to poor combustion of lean gaseousfuel-airmixtures.
TABLE 1- COMBUSTION AND THERMAL PERFORMANCE
Fuel Combination BTE / Substitution Challenge / Note
Natural Gas + Diesel [Refs 5,9,13,15,16,18,19,23,26,29 ]
CNG + Diesel [Refs 4,7,12,14,17,18,25]
BTE38.6–43.1% (optimized high-load); pilotdiesel6–11mg/cycle; airratio1.3–1.45; RCCI+LIVC cutsmethane slip≤80%.
BTEupto 38.6%(with supercharger) ;50–70% diesel substitution withoutmajor engine modification; stableat30–45%CNG share.
LPG + Diesel [Refs 3,8,11]
Producer Gas + Diesel [Refs 6,10]
Part-load poor; methaneslip ↑withNG fraction; NOx–BTE trade-off unresolved.
CNG>45% causes ignition delay&HC rise; compression ratioiskey control parameter.
BTEimproved to31%;BSFC ↓6–8%; efficiency ↑1.25%over diesel; moderate dieselsavings. Higher combustion temperature raisesNOx; EGR requiredfor NOxcontrol.
Maxdiesel substitution 52.7%; electrical efficiency ↑6.13–12.56% with increasinggas flowrate.
Electrical efficiency dropsfrom ~19%to ~9.5%due tolow calorific value; gasifier required.
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 13 Issue: 06 | Jun 2026 www.irjet.net p-ISSN: 2395-0072
Syngas + Diesel [Refs 22,27]
Biogas / Biodiesel [Refs 21,30]
ITE~39.3%; diesel substitution ~40%;NOx ↓75%with EGR optimization. Very sensitiveto syngas composition ;gasification &gas cleaning plant required.
Power↑16–22%;SFC ↓32–35%; liquidfuel savings29–31%;off-grid feasibility shown. Lowcalorific valuelimits substitution; emission datavery limitedin reviewed studies.
5. EMISSION CHARACTERISTICS
Emissionreductionisoneoftheprimarymotivesofadapting to dual fuel generator systems. The reviewed literature indicatesthatgaseousfuelsubstitutionsignificantlyreduces smoke opacity, particulate matter and carbon dioxide emissions. However, carbon monoxide and hydrocarbons tendtoincreaseparticularlyunderpartloadconditionsdue to unburnt gaseous charge. Compression ratio and pilot diesel quantity were identified as critical parameters influencingtheemission-efficiencytradeoff,particularlyin CNG-dieselsystems [26].
As evident from Table 3, natural gas substitution consistently achieves the most significant reductions in smokeandCO₂emissions,withMuhssenandBereczky [28] reportingsmokeopacityreductionsofapproximately95% and Kabeyi and Olanrewaju [17] documenting NOx reductionsof50–87%atthelargeplantscale.Syngas-diesel operationdemonstratedthestrongestNOxreductionamong alternativegaseousfuels,withArslanetal. [25] reportinga 75%reductionalongsidea 35%decrease inCOemissions through EGR optimization. LPG-diesel systems showed mixed NOx behavior Aydin et al. [8] reported a 4–6% increaseinNOxattributedtohigherin-cylindercombustion temperatures, while smoke and CO emissions were simultaneouslyreduced.TheincreaseinCOandunburned hydrocarbons at low loads remains a recurring challenge across all gaseous fuel types, consistently linked to poor flame propagation in lean premixed gaseous fuel-air mixtures.
6. ECONOMICAL FEASIBILITY
Theeconomicviabilityofdual-fuelconversionisadecisive factor in determining the practical adoption of this technologyacrossdifferentapplicationscales.Thereviewed literatureevaluateseconomicfeasibilityprimarilythrough parameterssuchasdieselfuelcostsavings,paybackperiod,
return on investment, and specific fuel consumption reduction.
Atthesmall-to-mediumscale,Lunaetal. [26] demonstrated a maximum fuel cost saving of 53% at 70 kW output on a turbocharged4-cylinderdieselgenset,withcostreductions observed across all tested power levels. Aydin et al. [8] reported a 6–8% reduction in brake specific fuel consumptiononasingle-cylinderdieselgeneratoroperating on LPG-diesel dual fuel, directly translating to lower operating costs. At the large industrial scale, Kabeyi and Olanrewaju [17] conductedatechno-economicassessment of converting a 120 MW diesel power plant to dual-fuel operationandestimatedapaybackperiodofapproximately 4months,establishingconversionasfarmoreeconomically attractivethanfullplantreplacement.Ismailetal. [7] further validatedeconomicviabilityatthevehicleandgensetlevel, reporting a return on investment period of 1.1–5.3 years dependingonannualmileageandfuelconsumptionpatterns.
Natural gas and CNG-based systems generally offer the greatesteconomicadvantagesduetotheirrelativelylowfuel cost and high diesel substitution potential. In addition, retrofitting existing diesel generators often requires significantly lower capital investment compared with purchasing new power generation equipment. Additional costsassociatedwithfuelstorage,gassupplyinfrastructure, safetysystems,controlunits,andmaintenancerequirements must also be considered. Therefore, a comprehensive economicevaluationisnecessarytodeterminethepractical feasibility of dual-fuel generator implementation under specificoperatingconditions.
7. OPERATIONAL CHALLENGES AND RESEARCH GAPS
Dualfuelgeneratortechnologyofferssignificantbenefitsin termsoffuelsavingandemissionreduction.However,there are several operational challenges that are limiting its implementation. The reviewed research indicates that performanceofdual-fuelgeneratordependsoncombustion stability, fuel substitution ratio, engine load and control strategy so operational challenges occurs whenever gas substitution is increased beyond optimized limits and it hinderstheperformanceofgeneratorset.
Methanesliptheescapeofunburnednaturalgasthroughthe exhaust emerges as the most critical and widely reported challenge in natural gas-diesel dual-fuel systems. Shouvik Dev, Hongsheng-Guo , Roya missaghian & Simon Lafrance [19] demonstrated that improved intake airflow management can reduce methane slip by approximately 28%,whileZarrinkolahandHosseini [22] showedthrough CFDsimulationthattransitioningfromconventionaldualfuel combustion to early injection RCCI mode can achieve reductions of up to 42.5%. However, these improvements consistently come at the cost of increased NOx emissions,
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
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highlightingafundamentalemissiontrade-offthatremains unresolved in the current literature. Part-load operation representsanotheruniversalchallenge A.P.Carlucci,A.de Risi,D.Laforgia&F.Naccarato [2] andDimitriouetal. [14] bothreportedthatleanpremixedgaseousfuel-airmixtures atlowloadsresultinpoorflamepropagation,increasedCO and unburned hydrocarbons, and reduced thermal efficiency, with conventional remedies such as intake boosting and split injection proving largely ineffective. Pedrozoetal. [15] furtheridentifiednaturalgascomposition variationasasignificantpracticalchallenge,aschangesin methane number alter combustion characteristics and engineperformanceinwaysthataredifficulttocontrol in field conditions. Across the reviewed literature, three overarchingresearchgapsemerge:theabsenceoflong-term durabilityandreliabilitystudiesonconvertedgeneratorsets underrealoperatingconditions,thelimitedinvestigationof transient load behavior in dual-fuel mode, and the insufficient translation of laboratory findings to commerciallyvalidatedgeneratorsetapplications.
8. CONCLUSION
Dual-fuelgeneratortechnologyhasemergedasapromising solutionforreducingdieselconsumptionandimprovingthe environmentalperformanceofstationarypowergeneration systems. The reviewed studies indicate that gaseous fuels such as natural gas, CNG, LPG, producer gas, syngas, and biogascansuccessfullyreplaceasignificantportionofdiesel fuelwhilemaintainingsatisfactorygeneratorperformance. In addition to fuel savings, dual-fuel operation has been showntoreducesmokeemissions,particulatematter,and carbon dioxide emissions under optimized operating conditions. However, challenges such as increased carbon monoxideandhydrocarbonemissions,methaneslip,ignition delay,andcombustion instabilityatlowloads continue to limitwidespreadadoption.Theliteraturealsohighlightsthe importanceofproperretrofitting,combustioncontrol,and fuel management strategies for achieving reliable and efficientoperation.Overall,dual-fuelgeneratorsrepresenta technicallyfeasibleandeconomicallyattractivealternative to conventional diesel generators, with considerable potentialforsupportingcleanerandmoresustainablepower generationinthefuture.
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ANNEXURE A
1 J.Patterson,A.Clarke,R.Chen 2006 Lister-Petter4-cylinderDIDiesel Genset(2.29L) Methane-Diesel,PropaneDiesel,Butane-Diesel
PropaneshowedthebestemissionperformancewithsignificantreductionsinNOxandsmoke.Methane achievedthehighestgassubstitutionlevels(upto95%athalfload),whilebutaneproducedthehighestNOx andsmokeemissions.Dual-fueloperationreducedsmokeemissionssubstantiallycomparedtoconventional dieseloperation.
2 A.P.Carlucci,A.deRisi,D.Laforgia&F. Naccarato 2008 Single-CylinderCommonRailDI DieselEngine(CR17.1:1) NaturalGas(CNG)+Diesel PilotFuel
Dual-fueloperationsignificantlyreducedparticulatematter(PM)emissionscomparedtodiesel-only operation.Combustionandemissionswerestronglyinfluencedbypilotdieselquantityandinjection pressure.Properpilotinjectionimprovedcombustionstabilityandflamepropagation.
3 A.Kumaraswamy&B.DurgaPrasad 2012SingleCylinder,4-StrokeCIEngine (5HP,1500rpm) Diesel+LPG+EGR Dual-fueloperationwithLPGimprovedBrakeThermalEfficiency(BTE)upto31%andsignificantlyreduced smokeemissions.EGReffectivelyreducedNOxemissions.LPGsubstitutionreduceddieselconsumption whilemaintainingcomparableengineperformance.
4 AbhayTiwari 2015 CompressionIgnitionDiesel EngineConvertedtoDual-Fuel Engine CNG(NaturalGas)+Diesel
Dieselenginescanbesuccessfullyconvertedintodual-fuelenginesusingCNG.Naturalgascanreplace 50–70%ofdieselfuelwhilereducingCO₂,CO,HC,andNOxemissions.Dual-fuelenginesretaindiesel-like efficiencyandcanoperateon100%dieselifgasisunavailable.
StudyinvestigatedonlyNOxandsmokeemissions.CO,HC,brakethermalefficiencyandlong-termengine durabilitywerenotanalysed.Testswerelimitedtofixed-speedgensetoperation(1500rpm).
COandTHCemissionsincreasedunderlow-loadconditionsduetopoorflamepropagationofleanCNG-air mixtures.NOxformationremainedsensitivetopilotfuelinjectionparameters.
EGRincreasedCOemissions,fuelconsumption,andpotentialenginewear.HCemissionsremainedhigher thandieseloperation.Studylimitedtoasmallstationaryengineandfixedoperatingconditions.
Primarilyareview/conceptualstudy;noexperimentalvalidation,performancetesting,ordetailedemission measurementswereconducted.
5 WeifengLi,ZhongchangLiu&ZhongshuWang2016 8.6L,6-CylinderTurbocharged Diesel-NGDualFuelEngine NaturalGas+Diesel
6 MonoromRith,JoseBienvenidoM.Biona, H.W.Gitano-Briggs,PisethSok,JeremiasA. Gonzaga,NechohArbon,ArchieB.Maglaya
2016CompressionIgnition(CI)DieselGensetDiesel+ProducerGas
Threecombustionmodes(h,m,n)wereidentified.Advancingdieselinjectiontiming,increasingEGR,and intakethrottlingimprovedbrakethermalefficiency(BTE)andreducedHCemissions.Then-combustion modeprovidedthehighestefficiencyandlowestHCemissions.
Producergassuccessfullyoperatedadieselgensetindual-fuelmode.Maximumdieselreplacementof52.7% wasachievedusingJatrophapresscake-derivedproducergas.Dieselconsumptionwassignificantlyreduced comparedtodiesel-onlyoperation.Thetechnologydemonstratedthefeasibilityofutilizingbiomass-derived fuelsfordecentralizedelectricitygeneration.Biomasstypehadlittleeffectonefficiencyandenergy consumption.
7 MuammarMukhsinIsmail,FathulHakim Zulkifli,MasFawzi&ShahrulAzmirOsman 2016 Common-RailDieselEngine (ToyotaHiluxConversion) CNG+Diesel SuccessfullydevelopedaCNG-dieseldual-fuelconversionkitwithoutmajorenginemodification.Diesel quantitywasreducedusingECU-basedfuelpressureemulation.EconomicanalysisshowedROIbetween 1.1–5.3yearsdependingonannualmileageandfuelconsumption.
8 Aydin,M.,Irgin,A.,&Çelik,M.B. 2018 Single-cylinderdieselgenerator (2.4kVA) Diesel+LPG BSFC↓6–8%,Efficiency↑1.25%,Smoke↓80%,CO↓30%,HC↓20%
9 Luksho,V.A.&Kozlov,Andrey&Terenchenko, A.s&Grinev,Vadim 201811LHeavy-DutyDualFuelEngine Diesel+NaturalGas Fueleconomyimproved20–30%,optimumpilotfuel6–11mg/cycle,optimumairratio1.3–1.45
10 Sutheerasak,Pirompugd&Sanitjai 2018JohnDeere3029DF150,3-Cylinder DIDieselEngineGenerator(2.9L) SuperchargedProducerGas +Diesel
Maximumdieselsavingof40%achievedat1200rpmand125lpmproducergasflowrate.Electrical efficiencyincreasedby6.13–12.56%,electricalpowerincreased,andspecificenergyconsumption decreasedwithincreasingproducergasflowrate.
Combustionbecamehighlysensitiveandunstableundern-modeoperationifcombustionboundarieswere notcarefullycontrolled.Studyfocusedmainlyonlow-loadconditions.
Electric-thermalefficiencydroppedsignificantlyfrom19%(dieselmode)toapproximately9.5%(dual-fuel mode).Specificfuelconsumptionandspecificenergyconsumptionincreasedsubstantiallybecauseofthelow calorificvalueofproducergas.COandCO₂emissionswerehigherthandiesel-onlyoperation.Producergas displacedintakeair,resultinginincompletecombustion.Mixedbiomassfeedstockcausedunstablegasifier operationduetovaryingparticlesizes.Resultswerelimitedtoasmall-scalegeneratorsystem.
Focusedmainlyonconversionmethodologyandfinancialanalysis.Detailedengineperformance,combustion, efficiency,andemissionmeasurementswerenotexperimentallyevaluated.
NOxincreasesathighinjectionpressureandadvancedtiming
COemissions,HCemissions,andsmokeopacityincreasedsignificantlyduetoincompletecombustionand reducedoxygenavailability.Studyconductedonlyunderfull-loadconditionsandfixeddieselinjection timing.
11 AlbertoBoretti 2019 CompressionIgnitionDirect Injection(CI-DI)DieselEngines Diesel,CNG-Diesel,LNGDiesel,LPG-Diesel Dual-fuelenginesreducePM,NOxandCO₂emissionswhilemaintainingdiesel-likeefficiency.Naturalgasbaseddual-fueloperationoffersbetterenvironmentalperformancethanconventionaldieselengines. Methaneslipcanreduceenvironmentalbenefits.Dual-fuelsystemsrequireadvancedfuelinjection technologyandoptimizationformaximumefficiency.
12 ArkadiuszJamrozik,WojciechTutak&Karol Grab-Rogaliński 2019 Andoria1CA90Single-Cylinder StationaryCIEngine(573cc) CNG+Diesel
13 ShouvikDev,HongshengGuo&BrianLiko 2020 Caterpillar3401Single-Cylinder Heavy-DutyCIEngine(2.44L) NaturalGas+Diesel
14 PavlosDimitriou,TakuTsujimura,Hirokazu Kojima,KenjiAoyagi,NaokiKurimoto& YoshiakiNishijima 2020Single-CylinderandMulti-Cylinder CIEngines NaturalGas(CNG)+Diesel
CNGshareupto45%improvedcombustionintensity,increasedpeakcylinderpressureandheatrelease rate.Moststableoperationoccurredat30–45%CNGshare.CO₂emissionsreducedby~26%andCO emissionswerenearlyeliminated.
IncreasingNGfractionimprovedBTEupto~42%,reducedsootandCO₂-equivalentemissions,andenabled significantdieselsubstitutionathighloads.Optimizeddieselinjectiontimingimprovedcombustion efficiency.
Advanceddieselinjectionsignificantlyimprovedcombustionefficiency,reducedTHCemissions,increased thermalefficiency,andreducedNOxatlowloads.HotEGRsimultaneouslyreducedNOx,CO,andTHC emissionswhileimprovingbrakethermalefficiency.Splitinjectionandintakeboostingwereineffectiveat low-loadoperation.
NOemissionsincreasedwithincreasingCNGshare.AtCNGsharesabove45%,ignitiondelaybecame excessiveandHCemissionsincreasedduetoincompletecombustion.
HigherNGfractionincreasedmethaneemissions,injectortiptemperature,NOxemissions,andrequired carefuloptimizationofdieselinjectiontimingtoavoidpressure-riselimitations.
Studymainlyfocusedonlow-loadconditions.Intakeboostingincreasedunburnedemissionsandreduced efficiency.SplitinjectioncausedexcessiveNOxformationandincreasedmethaneslip.
Volume: 13 Issue: 06 | Jun 2026 www.irjet.net p-ISSN: 2395-0072
15 ViníciusBPedrozo,XinyanWang,WeiGuan &HuaZhao 2021Single-CylinderHeavy-DutyDualFuelCIEngine NaturalGas+Diesel
16 EnricoMattarelli,CarloAlbertoRinaldini, TommasoSavioli,andFrancescoScrignoli 2021 Four-Cylinder,Four-Stroke, TurbochargedCRDIDual-Fuel Engine(2.8L,Gen-setApplication)
NaturalGas+Diesel
17 MosesJ.B.Kabeyi&OludolapoA.Olanrewaju2022 DieselPowerPlant(KipevuIII, 120MW)
HeavyFuelOil+Natural Gas(DualFuel)
18 Yuvenda,D.,Sudarmanta,B.,Jamaludin,J., Muraza,O.,Putra,R.P.,Lapisa,R.,...& Primandari,S.R.P. 2022 SingleCylinderDIDieselEngine (411cc,CR18:1) CNG+DieselwithElectric Supercharger
19 ShouvikDev,Hongsheng-GuQRoya missaghian,SimonLafrance&honshengguo 2022Single-CylinderFour-StrokeHeavyDutyDual-FuelCIEngine NaturalGas+Diesel
Naturalgascompositionsignificantlyaffectedcombustionbehaviour,methaneslip,NOxemissions,and thermalefficiency.Fuel-qualityvariationwasidentifiedasamajorchallengebecausechangesinmethane numberalteredcombustioncharacteristicsandengineperformance.Lowermethanenumberreduced methaneslipbutincreasedNOxemissions,highlightinganemissionstrade-off.RCCIcombinedwithLIVC achievedupto80%lowermethaneslipandNOxemissionswhileimprovingefficiencycomparedwith conventionaldual-fueloperation.
Dual-fueloperationimprovedgeneratorperformance,increasingbrakethermalefficiencyfrom35.8%to 39%whilereducingNOx(32%),CO₂(31%),andsootemissions(>50%)comparedwithdieseloperation. However,COandHCemissionsincreasedsignificantly,andcombustionqualitydeterioratedatlowloadsdue toincompletecombustionofultra-leannaturalgasmixtures,creatingoperationalchallengesforstablelowloadoperation.
Conversiontodual-fueloperationreducesfuelcost,specificfuelconsumption,totalemissions,andimproves thermalefficiency.Paybackperiodestimatedatabout4months,makingconversiontechnicallyand economicallyfeasible.
Optimizingair-fuelratio(λ)improvedthermalefficiency,cylinderpressure,HRR,combustionstabilityand reducedCO,HCandPMemissions.Maximumthermalefficiencyreached38.6%athighloadwithλ=1.69.
Methaneslipduetoincompletecombustionisakeychallengeindual-fuelengines.Improvedintakeairflow enhancedfuel-airmixing,reducingmethaneslipby~28%andCOby25%.However,thisincreasedNOxand slightlyreducedthermalefficiency,highlightingthetrade-offbetweenemissioncontrolandperformance.
20 MostafaSoliman,MohamedElkelawy,Ahmed G.Olabi,andMohamedM.Elsheikh 202230kW4-CylDITurbochargedDieselGeneratorSimulatedBiogas(CH4+CO2/N2)+Diesel
Dual-fueloperationimprovedfuelutilizationandreducedsmokeemissionscomparedwithdieseloperation. Engineperformanceandemissionswerestronglyinfluencedbyoperatingconditionsandgassubstitution ratio.Thestudyidentifiedatrade-offbetweenimprovingefficiencyandcontrollingemissions,highlighting theneedforcombustionoptimizationforstabledual-fueloperation.
Single-cylinderlaboratorystudy;noeconomicordurabilityanalysis;limitedgascompositionstested;no transient-loadevaluation;applicabilitytocommercialgensetsrequiresfurthervalidation.
Thestudyfocusedmainlyonhigh-loadoperatingconditions,withlimitedevaluationattransientconditions. Low-loaddual-fueloperationremainedchallengingduetoincompletecombustion.Long-termdurability, economicfeasibility,andcatalystperformanceforcontrollingincreasedCOandHCemissionswerenot investigated.
Naturalgasinfrastructureinvestmentrequired.Methaneleakagemayreduceenvironmentalbenefits.Longtermdependenceongasmaydelaytransitiontozero-carbonenergysystems.
Excessiveairsupplycausedleanmixtureformation,reducedcombustionquality,lowercylinderpressure andlowerthermalefficiency.Additionalsuperchargersystemincreasescomplexityandcost.
Conductedonasingle-cylinderresearchengineunderlaboratoryconditions;increasedNOxemissionsand slightefficiencylosswereobserved;fuelsubstitutionratioeffectswerenotinvestigated;noeconomic, durability,orlong-termoperationalanalysiswasperformed;applicabilitytocommercialgensetsandoilfield powersystemsrequiresfurthervalidation.
Thestudywasconductedonasingle-cylinderresearchengineandunderlimitedoperatingconditions.Longtermdurability,economicfeasibility,transient-loadbehavior,andgenerator-specificperformancewerenot evaluated
21 HyunwookPark,EuijoonShim,JunsunLee, SeungmookOh,ChangupKim,YonggyuLee, KernyongKang 2023 Heavy-duty11.1LMulti-cylinder Engine NaturalGas+Diesel
22 Zarrinkolah&Hosseini 2023 Single-Cylinder,Four-Stroke, NaturallyAspiratedNatural Gas–DieselDual-FuelCompression Ignition(CI)Engine(CFD-based enginemodel)
NaturalGas+Diesel
23 NeerajKumar,BharatBhushanArora,and SagarMaji 2023 Single-Cylinder,Four-Stroke, VariableCompressionRatio(VCR) Dual-FuelEngine Diesel+CNG
24 ZiyangDai,WeikangDu,JieLi,YinmiLuo,Zhi Jia,andBinyangWu 2023
Single-Cylinder,Four-Stroke, CompressionIgnitionNaturalGas Dual-FuelEngine NaturalGas+Diesel
25 Arslanetal.AysegulArslan,ShouvikDev, DavidStevenson,JamesButler,Hongsheng Guo,MadjidBirouk
2024 30kW,4-cylinderturbocharged generator Diesel+Syngas
26 FranciscoE.TavaresdeLuna,EmersonF. Jaguaribe,AdrianoS.Rumão&JorgeR. Henríquez 2024 Perkins1104C-44TAG2 Turbocharged4-CylDiesel GeneratorSet Diesel+NaturalGas
27 ShouvikDev 2024 6-cylinder(Inlineconfiguration)4 strokecompressionignition retrofittedfordualfueloperation NaturalGas+Diesel
28 XiaoZhang,JianqunGao,DaweiFan,Qizheng Yang,FangjunHan,andHongliangYu 2024 MANB&W6S50ME-C-GI,SixCylinder,Two-Stroke,Low-Speed MarineNaturalGas–DieselDualFuelEngine NaturalGas+Diesel
RCCImodeachievedhighestefficiency(41.4%)atlowloads;E-Pilotachieved43.1%BTEatmediumloads; CDFachieved42.8%BTEathighloads.AuthorsrecommendE-Pilotforlow-to-midloadsandCDFforhigh loadsforoptimalefficiencyandemissionreduction.
Methaneslipisakeychallengeindual-fuelenginesduetoincompletenaturalgasoxidation.Switchingfrom CDFtoEIRCCIcombustionreducedmethaneslipby33%,andoptimizeddieselspraygeometryachievedup to42.5%reduction.Injectiontiming,sprayangle,andcombustion-modeselectionwereidentifiedascritical parametersforbalancingefficiencyandemissions.
increasingCNGsubstitution(upto~80%)reducedCO₂,NOx,andsmokeemissions,demonstratingthe potentialofgaseous-fueloperation.However,COandHCemissionsincreasedduetoincompletecombustion. Compressionratiosignificantlyaffectedcombustionqualityandemissionperformance,highlightingthe challengeofbalancinghighfuelsubstitutionwithstableandefficientoperation.
Increasingintakepressureimprovedcombustionactivityandthermalefficiency,whileEGRhelpedsuppress knockandcontrolemissions.Optimizedintakeconditionswithsuitablepilotinjectiontimingachievedhigh thermalefficiency(~50%)withreducedTHC,CO,andNOxemissions.Thestudyhighlightedthechallengeof balancingcombustionefficiency,knocksuppression,andemissioncontrolunderhigh-loaddual-fuel operation.
Dieselsubstitution40%,ITE≈39.3%,NOx↓75%,CO↓35%,PMreduced,HCincreasedathighEGR
Dual-fuelkitinstalledwithminimalenginemodification;fuelcostsreducedacrossallpowerlevelstested; maximumcostsavingof53%at70kW;sootandCO2reducedathighloads;NOxreducedatlow-medium loads;COincreased
Thedual-fuelconfigurationsuccessfullyreplacedupto34%ofdieselconsumptionduringhighwayoperation (Devetal.,2024).Comparedtoadiesel-onlybaseline,theconversionyieldedlowerCO₂andengine-outblack carbonemissions,fulfillingtheoperatingcostreductionandpartialdecarbonizationgoalstypicalofCNG retrofits
Advancingpilotdieselinjectiontimingimprovedenginepower,thermalefficiency,andnatural-gasflame propagation,demonstratingbettercombustionperformance.However,earlierinjectionalsoincreasedNO andmethaneemissions,highlightingthechallengeofbalancingefficiencyimprovementwithemission controlindual-fueloperation.Injectiontimingsignificantlyaffectedignitiondelayandrapidcombustion stages.
RCCIoperationlimitedtolowloadsduetohighpressureriserate(MPRR).E-Pilotalsounsuitableforvery highloads.Multiplecombustionmodesandadvancedcontrolsystemsarerequired.
ThestudywasprimarilyCFD/simulationbasedandrequiresexperimentalvalidation.Itwasnotconducted onacommercialgeneratorsetanddidnotevaluateelectricalperformance.Analysiswasperformedunder limitedoperatingconditionsanddidnotassesstransientloads.Economicfeasibility,long-termdurability, injectorwear,andmaintenanceimpactswerenotinvestigated.Onlynaturalgas–dieseloperationwas considered;associatedgasandvariablefield-gascompositionswerenotevaluated.
Thestudyfocusedmainlyonemissionsandprovidedlimitedcombustionandperformanceanalysis. Experimentswereconductedonasingle-cylinderlaboratoryengine,withnoevaluationofdurability, transientoperation,economicfeasibility,orfuel-compositionvariation.
Thestudywasconductedunderhigh-loadoperatingconditionsonly,limitingapplicabilityacrossthefull operatingrange.Long-termdurability,transientoperation,economicfeasibility,andgenerator-level performancewerenotevaluated.Theeffectofvaryingnaturalgascompositionwasalsonotinvestigated.
HighEGRincreasesHCandPM,optimizationrequired
Singleenginemodeltested;nolong-termdurabilityanalysis;resultsspecifictoBrazilianfuelpricing; transientloadbehaviournotevaluated
Theprimarydrawbackidentifiedwas"methaneslip"—unburnedmethaneescapingthroughtheexhaust after-treatmentsystem.Thisslipsignificantlyincreasedtotalhydrocarbonemissionsandnegatedsomeof thegreenhousegasadvantages,whiletail-pipeNOxemissionsalsosawanincreasecomparedtopurediesel operation
Thestudyfocusedmainlyonpilotdieselinjectiontimingwhilekeepingotheroperatingparametersconstant. Resultswereobtainedundercontrolledmarineoperatingconditionsandmaynotdirectlyrepresent generatorapplications.Long-termdurability,transientoperation,economicfeasibility,andfuel-composition variationwerenotevaluated.
29 HassanSadahMuhssen&ÁkosBereczky 2025 IVECOAIFO8031,24kWdiesel enginecoupledwithgenerator Diesel+NaturalGas Dieselconsumptionreduced,NOxreduced,CO₂reduced,smokereducedby~95% COandTHCemissionsincreased,BTEreduced
30 Dhairiyasamy&Gabiriel 2025 5kVASingleCylinder4-Stroke DieselGenerator Biogas+Biodiesel(B8, B20,B50,B80,B100)
PowerOutput↑16.06–21.77%,SFC↓31.53–34.97%,LiquidFuelSavings28.74–31.08%,Dual-fueloperation feasibleforoff-gridapplications
Noemissionanalysis,nodurabilitytesting,limitedbiogassupply,noeconomicanalysis,small-scalesetup only