Thermal Propulsion Systems Roadmap - APCUK

Thermal Propulsion Systems RoadmapUpdated by the Advanced Propulsion Centre in collaboration with and on behalf of the Automotive Council

Executive summary: Thermal propulsion systems The 2013 roadmap focused on thermal efficiency, systemefficiency and enabling technologies that support continuedengine innovations. The 2017 roadmap builds upon the 2013 approach and recognisesthat light duty and heavy duty base engines may take differentapproaches. The 2017 roadmap has introduced stretched targets for futurelight and heavy duty systems, focussing on wider emissionsspectrum in order to maintain market relevance andcompetitiveness. The roadmap reflects that thermal propulsion systems are part ofa wider powertrain system, and its performance and compliancewith regulation is dependent on the integration of pre and postcombustion sub-systems. Similar to the 2013 roadmap, alternative operational cyclesthrough alternative engine designs and control systems arehighlighted in the roadmap. There is a stronger recognition of the integration of transmissionsand energy recovery devices to further enhance hybrid systemperformance.

Update process: The 2017 Thermal Propulsion Systems Roadmap was updated via astructured consensus-building process involving 52 expertsThermal Propulsion Systems Steering Committee and WorkshopAttendees A public workshop was held atthe University of Bath on the31st January 2017Vehicle ManufacturerSupplierTechnology DeveloperEngineering Service ProviderResearch The process was co-ordinatedby the Advanced PropulsionCentre on behalf ofAutomotive Council The Advanced PropulsionCentre Thermal Efficiency andSystem Efficiency Spokes,supported by an expertSteering Group, helped toshape the roadmap before andafter the workshop.52OtherPre-Event EmailPre-event CommonAssumptions Briefing1 day workshop with 45 attendeesCollective BriefingProcessBreakout SessionsPost-Event EmailPost-Event Debrief

Technical targets: Mass market adoption of increasingly hybridised vehicles driveschallenging cost and performance targets for future thermal propulsion systemsDrivers of change Incremental innovations in thermal propulsion systems hasprovided steady improvements over a long period, but biggerchanges are required. Ambitious targets, that are unobtainable with existing enginetechnology, have been set to drive significant innovation. Thesetargets must be achieved without compromising customerdemands of exceptional cost effectiveness, range requirements,power density and recyclability. Reducing air quality and CO2 emissions challenges the currentapplication of all TPS powertrains using conventional fuels. Futuresustainable fuels and the associated engine technology areactively being developed, potentially near carbon neutraloperation. Air quality and efficiency will remain key drivers. Life cycle measures and materials security will challenge allpropulsion technologies, supporting the acceptability of TPS withsuitable performance against these metrics For light duty vehicles, TPS will feature in all hybrid vehicles beforethe potential advent of fuel cell hybrids. Hybridisation implies achange in the nature of TPS and offers higher efficiencies. For heavy duty the TPS remains core to future propulsion due tothe absence of alternatives. Further improvements to efficiencyand emissions are needed, including new fuel types and energyrecovery.Light Duty201720252035Engine System BrakeThermal Efficiency(%)1,2424853Tailpipe NOx &Particulates (Mass &Number)In line withlegislatedlimitsHeavy Duty201720252035Engine System BrakeThermal Efficiency(%) 1475560Tailpipe NOx &Particulates (Mass &In line withlegislatedlimitsNumber)Zero in emissionscontrolled zones3Zero in emissionscontrolled zones31) Peak efficiency values shown. Increasingly important to achieve high efficiency across awider operating range, in keeping with testing cycles based on real world performance2) Values reflect mid point between diesel and gasoline efficiency (current difference 5%)3) Below measureable limits or below ambient (background) levels

Technology categories: To meet tough targets parallel development is needed in thermal efficiency of base enginesand efficiency of the wider systemEngine architecture and fuellingdetermine thermal efficiency.Improvement approachesmostly differ between thermalpropulsion sysems thatexperience light vs heavy dutycycles. Note that some heavyvehicle platforms mayexperience light(er) duty cyclesand vice versaAir, heat, exhaust gas management, parasiticloss reduction and engine control are crucialto efficiency and emissionsDrivetrain systems enable thermal propulsion systemsto operate in a reduced speed / load envelope, allowingsignificant efficiency and emissions improvementsDesign, material and manufacturing choicesaffect total environmental impact5

Thermal efficiency: Existing light duty thermal propulsion systems need to improve, but will reach a point where theytransition into hybrid focussed power units for mass market applicationsThese technologies can be applied to hybrid focusedthermal propulsion systemsAdvanced coatings and materialscan help reduce heat loss toimprove thermal efficiencyRobust, reliable variablecompression ratio, valvetiming and controlstrategies to deactivatecylinders (e.g. skip fire)enable base engines toreduce consumption costeffectivelyDifferent combustion strategiessupport efficient operation withoutstep change in engine architecturePost 2025 targets necessitate deeper hybridisation(HEV and PHEV) for light duty vehicles. Creates a stepchange in architecture to potentially simpler powerunits which are matched to the depth ofhybridisation. Power density and cost are mainfeatures, with emissions minimised through fewengine speeds and system optimisation.Novel cycles, cam-free valve actuation, crankless,rotary, turbine, turbine ICE, 2 stroke, fuel cell (PEMand SOFC) are all candidates.6

Thermal efficiency: Heavy duty thermal propulsion systems require continuous improvement to evolve towardsvery high efficiencyContinuing optimisation of current TPS designs, withcareful focus on specific duty cycle of applicationsEfficient, low NOx combustion processesapplied as heavy duty CO2 targets applied.In the short term, longer range HDVs may employ exhaust waste heatrecovery systems such as Organic Rankine Cycles, turbo-compounding orthermo-electric generators. In the longer term, the next generation of wasteheat recovery systems could potentially progress to efficiently harvestinglower grades of heat, storing waste heat effectively in a heat battery orharvesting waste heat from multiple sources.Arrows signify the above technology willbe developed as part of the technologydevelopment in the bar belowHybridisation plays a minor role, other than for brakingenergy recovery, so very high thermal efficiencyengines needed. Designs evolve to e.g. Joule/Braytoncycle; cryogenic engines such as split cycle; closed cyclecombustion. TPS designs will be suited to precise dutiesand drive cycles. Fuel cells (PEM and SOFC) may berelevant, especially where zero emissions are required.7

Thermal efficiency: Both light and heavy duty engines will need to adapt to a wider range of fuels to later alsoinforming the development of fuelsContinuing close collaboration with fossil fuel refiners to optimiseexisting fuels and optimised engines that can run on alternativefuels such as biofuels and natural gas (CNG, LNG). There is alsothe potential for dual fuel engines to lower emissions(diesel/gasoline and hydrogen, diesel and natural gas)Ultra-low emission combustion processes developed alongsideadvanced low carbon fuels e.g. bio and synthetic componentssuch as ethanol/methanol, refined fossil fuels using renewablehydrogenMore precise fuel delivery through higher pressure and variable injection, gasoline pre-mix.Water injection where relevant.Note: Fuel injection systems will still continue to be developed beyond 2030. However thetechnology will be developed in conjunction with heavy duty orientated, high efficiencypower units or light duty hybrid focussed power unit (see thermal efficiency)8

System efficiency: A wide range of improvements in engine systems and control will support developments inexisting engines and the emergence of more novel designsFriction and weight reduction continue to be assistedby advanced design and manufacturing techniques(also refer to Lightweight Structures Roadmap).Note: Focus on lightweighting and better lubricationwill still continue to be developed beyond 2030.However new materials and lubrication will bedeveloped in conjunction with heavy dutyorientated, high efficiency power units or light dutyhybrid focussed power unit (see thermal efficiency)Retrofit aftertreatment is a very near termpriority for e.g. taxis and buses. The emphasisshifts towards systems that can provide widespectrum performance even as waste heatdeclines (especially HD). Longer term very noveltechs such as on board reforming and CO2 capturecould play a role, mainly for HD. LDaftertreatment shifts beyond 2025 to managingemissions across narrower engine operating rangeIncreased engine complexity in the near term runs risk of increasingparasitic loads. Electrification of ancillaries such as water pump, air boost,turbo-generator can be used to mitigate these demands for LD and HD.Simplified designs later on (especially LD) should reduce this needBoost systems provide wide range ofeffective operation throughcombining devices. These devicescontinue to improve through materialand bearing developments (highertemp, lower friction). Higher voltages(48v ) then enable widespreadapplication of e-boosting tocomplement multi device approachSmarter powertrain management is already improving fuel consumption. Predictivecontrol based on V2X, complex model based control and known road/trafficconditions will soon supplement this. Aggressive geo-fencing to ensure zero emissionzone compliance in cities could manage engines to off or ultra clean mode. Beyondthis fully automated control possible, especially in conjunction with CAV9

System efficiency: Transmissions and hybridisation are vital enablers for propulsion system efficiency; codevelopment will allow them to be operated closer to peak efficiencyTransmissions enable optimum engine operation through smart manual andautomatic transmissions replacing manuals (multi speed and variable speedespecially in LD). Longer term the role of LD transmissions will be changed byhybridisation. For HD co-developed autos will support engine evolutionHybrid systems continue to provide greater energy recoverynear term through addition of electrical and mechanicalstorage and propulsion assistance. At deeper hybridisationlevels engine and hybrid systems co-develop for optimumengine operation, enabling low emissions and high efficiency.10

Design and manufacturing: Design approaches, materials choices and manufacturing technologies must all evolve tosupport other technology developments and driversLighter weight metals dominate, withfocus on low process energy and wastemanufacturing processes.Greater enforcement of recycling regulations encourages designwith end of life in view. As life cycle considerations take hold, awider set of environmental impacts will influence material choices(e.g. water use, wastage, electricity consumption etc.)11

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