Results from Japanese Industry/Academia Joint Research Project

Impact of Future Regulations on Engine Technology ERC 217 Symposium June 14-15th, 217 University of Wisconsin Madison 1 Results from Japanese Industry/Academia Joint Research Project Super-Lean Burn Concept for High Efficiency SI Engine Challenge for Innovative Combustion Technology to achieve 5% thermal efficiency A grave project as Innovative Combustion Technology was organized in the Cross-ministerial Strategic Innovation Promotion Program (SIP) by the Cabinet Office. This (presentation) gives an introduction to Research and Development on the Super Lean Burn Concept for Gasoline Engines by the Gasoline Combustion Team with 28 cluster members. Norimasa Iida Keio University

What is SIP? 2 The Cross-ministerial Strategic Innovation Promotion Program (SIP) is a national project under the Council for Science, Technology and Innovation to promote the advancement of science, technology and innovation in Japan.

SIP - Innovative Combustion Technology - Purpose of SIP Innovative Combustion Technology 55 Transition of thermal efficiency of gasoline engine 3 Thermal Efficiency (%) 5 45 4 35 3 Thermal efficiency target : 5% Mass-produced engine: max.~4% HV Innovative combustion technology 25 199 2 21 22 Year To cope with social issues such as a climate change and energy security, the enhancement of the engine thermal efficiency is required.

SIP - Innovative Combustion Technology - 4 Gasoline Combustion Team Development of Super-lean burn technologies Leader : Keio Univ. Prof. Iida Controls Team Development of innovative control systems and CAE tools Leader : Tokyo Univ. Prof. Kaneko Diesel Combustion Team Development of high speed combustion with low noise and cooling losses technologies Leader : Kyoto Univ. Prof. Ishiyama Loss Reduction Team Development of exhaust energy utilization and mechanical friction reduction technologies Leader : Waseda Univ. Prof. Daisho 1 billion ($1 million) /5 years (214-218)

Cabinet Office PD (Masanori Sugiyama) Advice to PD for planning JST Funding (Management) Agency Project Management Promoting Committee Program Council Chair: Masanori Sugiyama (PD) Members: Shigeo Furuno (Sub-PD), Ministry of Economy, Trade and Industry, Ministry of Education, Culture, Sports, Science and Technology, JST, Experts from industry and academia Chair: Masanori Sugiyama (PD) Members: Shigeo Furuno (Sub-PD), Experts from industry and academia 4 teams from approx. 8 universities Gasoline Combustion Team Keio University Norimasa Iida Diesel Combustion Team Kyoto University Takuji Ishiyama Gasoline Combustion Subcommittee Cluster of Universities Diesel Combustion/Control Subcommittee Cluster of Universities Partnership Agreement The Research Association of Automotive Internal Combustion Engines Combustion Research Committee Gasoline Combustion Subcommittee Diesel Combustion/Control Subcommittee Controls Team University of Tokyo Shigehiko Kaneko Loss Reduction Team Waseda University Yasuhiro Daisho Diesel Combustion/Control Subcommittee CAE/PM Subcommittee Cluster of Universities Exhaust Energy Utilization Subcommittee Friction Loss Reduction Subcommittee Cluster of Universities CAE/PM Subcommittee Exhaust Energy Utilization Subcommittee Friction Loss Reduction Subcommittee 5

Research and Development of Super-Lean Burn for High Efficiency Gasoline Engine Gasoline Combustion Team Graduate School of Science and Technology Keio University Project Professor Norimasa Iida Research and Development are conducted to realize the super-lean burn technology. Specifically, 1) Ignition system enabled under super-lean and high intensity flow conditions, 2) Acceleration of the flame propagation by optimizing the tumble flow, 3) Cooling loss reduction based on the analysis of a wall heat transfer mechanism, 4) R&D for the creation of a knock control concept by an approach through chemical kinetics.

Background and Position of R&D Plan 7 Thermal efficiency of hybrid vehicle(hv) engines: approx. 39% (at the beginning of SIP) Current main technologies High expansion ratio Cooled EGR (Exhaust Gas Recirculation) Low friction Goal of SIP Realization of 5% Thermal Efficiency Innovative combustion technology is indispensable. エンジン熱効率 (%) Engine Thermal Efficiency (%) 5 45 4 35 SIP SIP プロジェクト Project Innovative technology is indispensable HV 用エンジン engines 3 199 2 21 This project drives the research for the following objectives for output with super-lean burn as a core technology 22 年 Year Transition of Thermal Efficiency of Gasoline Engines 1 Creation of technologies for elements to achieve 5% thermal efficiency 2 Modeling from the analysis of innovative combustion technologies

Scenario of 5% Thermal Efficiency for Gasoline Engines 8 Scenario of Thermal Efficiency Improvement Output Compression ratio 11 Excess air ratio λ1. Fuel heat release:1 Unburned gas 3 Exhaust loss 31 Cooling loss 25 Friction loss 5 Pumping loss1 Brake work 35 Thermal efficiency 35% Mass production vehicles Objectives Increasing indicated work Knock control improvement Reducing cooling loss Low temperature combustion Low S/V ratio Thermal insulation Reducing exhaust loss High expansion ratio Knock control improvement Reducing loss in gas exchange Turbocharger efficiency improvement Reducing friction loss Research Direction Super-lean burn system Ignition system applicable to high intensity airflow field Combustion technology development driven under super-lean, high intensity turbulence and high EGR Development of knock suppression technologies Cooling loss reduction technologies Cycle variation control technologies Technologies of Elements Gasoline Combustion Team Strong ignition High intensity air flow (Tumble) Cooling loss reduction (Thermal insulation) Knock control improvement (Cooling optimization) Loss Reduction Team Supercharging Waste heat recovery Friction reduction Control Team Innovative control Submodel Ignition model for Super-lean burn Super-lean, high intensity turbulence, high EGR combustion model Knock prediction model Heat transfer model OUTPUT to Control Team Compression ratio 13~14 Excess-air ratio λ 2. EGR 2% Fuel heat release:7 Unburned gas 2 Exhaust loss 19 Cooling loss 11 Friction loss 3 Brake work 35 Thermal efficiency 5% Target In addition to driving the research to enhance a potentiality of hardware related to combustion, 5% thermal efficiency is targeted in collaboration with other research teams

Targets driven by each team (point) Indicated Thermal Efficiency (%) 15 1 5 5 45 4 35 3 Mass production level Strong ignition device Surrogate fuels Catch up Goal Setting Setting targets among teams Demonstration with single-cylinder engine DI 4.6 S/V Low temperature combustion Single cylinder (Prototype) λ= 2, EGR2% Flow rate:2-5m/s P boost :1kPa ε =13 S/B=1.5 6.1 Low temperature combustion Single cylinder (Improved) Combustion improvement Combustion chamber improvement (+1.p) Piston shape ε = 13 15 18 S/B= 1.5 1.7 Single cylinder (Specifications change) Cooling loss reduction High comp. ratio (+1.1 p) Japan s originality Gasoline Combustion Team Gasoline Combustion Team and Loss Reduction Team 7.63 6.6 5.6 11.5 Single cylinder (Verification engine) Combustion improvement Knock control improvement Fuel utilization (+2.9 p) Fuel reforming Turbocharger improvement Friction loss reduction Thermoelectric generator (+2. p) 1 st year 2 nd year 3 rd year 4 th year 5 th year 9.5 Loss Reduction Team Knock Suppression Team Cooling Loss Reduction Team Ignition Improvement Team Flame Propagation Acceleration Team Creation of technologies for elements to achieve 5% thermal efficiency Proposal of models useful for engine development (Five goals) 9

Concept of Low Temperature Combustion technology Super-Lean burn Newton s cooling equation qq θθ = AA h θθ {TT gggggg θθ TT ssssssssssssss θθ } 1 Reduction of cooling loss 1 8 Exhaust loss Unburned fuel loss Increase of Specific heat ratio Heat balance (%) 6 4 2 Cooling loss Friction loss Thermal efficiency Ordinary combustion (Stoichiometric combustion) Super-Lean burn Operating condition targets for super-lean burn; Super-Lean (λ =2.) High turbulent flow ( u = 2~5 m/s, u = 5 m/s ) High EGR (EGR rate = 2 %) Ordinary Super-Lean burn

Goal Tasks and Solution Methods 11 Goal Concept Assignments Solutions Attainment of 5% thermal efficiency Realization of super-lean burn No ignition Unburnable Extinguished Engine knock Heat loss on combustion chamber wall Creation of technologies from science by the wisdom of industry-academia Strong ignition system (Optimal ignition method) Ignition at flow rate > 2m/s High efficiency tumble port Improvement of combustion chamber shape (High intensity turbulence flow utilization) Flame propagation acceleration with turbulence intensity > 5m/s Temperature control in combustion chamber Approach based on reaction theory (Understanding of elementary reaction) Knock suppression at γ 15 Improvement of surface shape in combustion chamber Low temperature combustion (Investigation of heat exchange phenomena) Cooling loss 5% reduction

Gasoline Combustion Team 12 Objectives We investigated the thermal efficiency of a test engine designed for the super-lean burn operation as a project of the SIP Gasoline combustion team. In order to advance to the super lean burn condition, ignition energy tumble intensity were improved and those effects on the thermal efficiency were examined.

Gasoline Combustion Team 13 Yamaguchi Univ. Kyusyu Univ. Hokkaido Univ. Hiroshima Univ. Tokushima Univ. Fukui Univ. Okayama Univ. Team leader: Prof. Norimasa Iida (Keio Univ.) Doshisha Univ. Osaka Inst. of Tech. Osaka Prefecture Univ. Keio Univ. Nagoya Inst. of Tech. ONO SOKKI Keio SIP Engine Lab. Tokyo Inst. of Tech. Tokyo City Univ. Tohoku Univ. Nihon Univ. Chiba Univ. Sophia Univ. Tokyo Univ. Tokyo Univ. of Agriculture & Tech. Meiji Univ. Ibaraki Univ. AIST Leader, Research Base Group Leaders Clusters To realize innovative combustion technology to drastically increase the thermal efficiency for energy savings and the CO 2 emission reduction, while producing the world-leading researchers and building a sustainable industry-academia collaboration in the field of engine combustion technology.

Research Site Keio University SIP Engine Laboratory at Ono Sokki Technical Center 14 Coolant Temperature Regulator Control Room Supercharger Metal Engine High Pressure Fuel Supply Device Fuel Control Device Lubricant Temperature Regulator CH 2 O-LIF System PIV System Optical Engine OH-LIF System Dynamometer

Test Facility 15 Single-cylinder metal engine Engine specifications Bore(mm) 75 Stroke(mm) 112.5 Stroke Bore Ratio 1.5 Compression Ratio 13 Fuel Injection System MPI, DI Intake Valve Open(deg. BTDC) -28~7 Intake Valve Close(deg. ABDC) 88~58 Exhaust Valve Open(deg. BBDC) 34~69 Exhaust Valve Close(deg. ATDC) -1~-45 Boosted System Electric Supercharger Exhaust port Intake port Shape of intake and exhaust ports Fuel specifications SIP common high-octane gasoline LHV (MJ/kg) 42.28 RON 99.8 Stoichiometric A/F ratio 14.22

Test Facility High energy ignition system 16 Ignition coil : 6 mj / 1coil Normal use : 1 coil High energy use : 2 5 = 1 coils

Test Facility 17 Port adapter for High tumble intensity Normal intake port High tumble intake port Port adapter

Results 18 Effects of high energy ignition and tumble port adapter Improvement rate of indicated thermal efficiency[%] 2 15 1 5 2rpm, IMEP=6kPa ignition coil 1, w/o port adapter 15 Ignition timinig [degatdc] -2-4 IMEP COV [%] 1 5-6 4.1-1% combustion duration [CA] 3 2 CO [%].5 1 4. 2 1-9% combustion duration [CA] 3 2 1.8 1 1.2 1.4 1.6 1.8 2 2.2 Air Excess Ratio, λ [-] NOx [ppm] 15 1 5.8 1 1.2 1.4 1.6 1.8 2 2.2 Air Excess Ratio, λ [-]

Results 19 Effects of high energy ignition and tumble port adapter Improvement rate of indicated thermal efficiency[%] 2 15 1 5 2rpm, IMEP=6kPa ignition coil 1, w/o port adapter ignition coil 1, w/o port adapter 15 Ignition timinig [degatdc] -2-4 IMEP COV [%] 1 5-6 4.1-1% combustion duration [CA] 3 2 CO [%].5 1 4. 2 1-9% combustion duration [CA] 3 2 1.8 1 1.2 1.4 1.6 1.8 2 2.2 Air Excess Ratio, λ [-] NOx [ppm] 15 1 5.8 1 1.2 1.4 1.6 1.8 2 2.2 Air Excess Ratio, λ [-]

Results 2 Effects of high energy ignition and tumble port adapter Improvement rate of indicated thermal efficiency[%] 2 15 1 5 15 2rpm, IMEP=6kPa ignition coil 1, w/o port adapter ignition coil 1, w/o port adapter ignition coil 1, w/ port adapter Ignition timinig [degatdc] -1% combustion duration [CA] -2-4 -6 4 3 2 IMEP COV [%] CO [%] 1 5.1.5 1 4. 2 1-9% combustion duration [CA] 3 2 1.8 1 1.2 1.4 1.6 1.8 2 2.2 Air Excess Ratio, λ [-] NOx [ppm] 15 1 5.8 1 1.2 1.4 1.6 1.8 2 2.2 Air Excess Ratio, λ [-]

Potential of Super Lean Burn (Keio University) 21 Indicated Thermal Efficiency [%] 5 45 4 35 3 25 2 Evaluation results from the single cylinder engine λ=1.6~1.93 215 year λ=1.93 Highest performance class of mass production engine 45.% SIP single cylinder engine S/B = 1.5 ε = 13 Engine speed = 2rpm Boosted w/ electric Supercharger Final goal Experimental result in 216 48.5% When boosting with turbocharger in place of e-supercharger.2.4.6.8 1. 1.2 Indicated Mean Effective Pressure [MPa] 46.% achieved

Results 22 Maximum indicated thermal efficiency Air excess ratio λ [-] 2 1.5 1.5 25 Stoichiometric Lean λ~1.9 Near super-lean burn THC [ppm] IMEP COV [%] 2 15 1 1 8 6 4 2 2 rpm High energy ignition w/ port adapter Boosted w/ electric Supercharger.2.4.6.8 1 1.2 Indicated Mean Effective Pressure [MPa] IMEP COV < 4 %

Test Facility 23 Single-cylinder optical engine and PIV system Laser Camera Laser sheet thickness Interrogation size Laser interval Δt Meas. frequency Seeding Particles Vector map PIV specifications

Results Tumble flow was enhanced by the port adapter. 24 Estimated tumble ratio Tumble ratio TR [-] 3. 2.5 2. 1.5 1..5. 9 18 27 36 Crank angle [deg ATDC] w/o port adapter w/ port adapter TR = r( x, z, θ ) U( x, z, θ ) ( x, z) ω r U ( x, z) r( x, z, θ ) 2

Results 25 Mean velocity and velocity fluctuation at spark plug Mean velocity [m/s] 6 5 4 3 2 1 w/o port adapter w/ port adapter 9 18 27 36 Square of velocity TKE [m fluctuation 2 /s 2 ] [m 2 /s 2 ] 8 7 6 5 4 3 2 1 w/o port adapter w/ port adapter 9 18 27 36 Crank angle [deg ATDC] Crank angle[deg ATDC] Mean velocity and velocity fluctuation around the spark plug were increased by the port adapter.

Integrated Heat Release (Φ=1.~.5) IMEP6kPa 26 Standard ignition(single coil) λ=1.6 University Leader: Keio University Strong ignition(1 coils)+tumble flow λ=1.9 Strong ignition(1 coils)+strong Tumble flow up to 3m/s λ=2.

Combustion trajectory on Peters turbulent combustion diagram 27 In the case of λ = 2., when the spark discharge occurs at -4deg.ATDC, propagation of flame kernels may be freezing (partly extinguish?) by stretching effects. The number of kernels increases dispersedly in the chamber. At around -1deg. ATDC, Ka becomes 1 and flame propagation starts. CA1 takes at -5deg. ATDC. In the case of λ =1., flame propagation started just after the spark discharge, and the heat release occurred, and with CA=1 at -5deg. ATDC.

Heat flux measurement under motoring condition 28 Amount of Heat Flux q [MJ/m 2 ].2.15.1.5 -.5 -.1 Heat flow from gas to the wall increases by increasing tumble flow intensity Because of wall cooling effects, it can be used for knock improvement. Motoring test Ne=2rpm WOT w/ Tumble adapter w/o Tumble adapter No increase of heat loss during the expansion stroke Heat flow from the chamber wall to gas during the first half of the compression stroke Intake Compression Compression Expansion Exhaust Total (negative) (positive) Effect of tumble flow intensity on the heat flux Keio University is small during the expansion stroke 28 Tokyo city University

Heat flux measurement under firing condition 1/2 Intake Compressio n Expansion Exhaust λ=1. (φ=1.) λ=1.4 (φ=.7) In-cylinder pressure Temperature Swing @Surface Temperature Swing @4mm depth In-cylinder gas temperature (mass averaged) λ=1. (φ=1.) λ=1.4 (φ=.7) Heat Flux Crank Angle θ [deg. ATDC] 29

Heat flux measurement under firing condition 2/2 Amount of Heat Flux q [MJ/m 2 ].8.7.6.5.4.3.2.1 -.1 Firing Ne=2rpm IMEP=4kPa, MBT w/ tumble adapter T water :35.2K (8deg.C) λ=1. (φ=1.) λ=1.25 (φ=.8) λ=1.4 (φ=.7) -.2 Intake Compression (negative) Compression (positive) Expansion Exhaust Total 3

Prospects of super lean burn engine 31 Cycle-to-cycle variation of indicated thermal efficiency as a function of air excess ratio 5 % by super lean burn!? 2rpm, Fuel=.32g/s, IMEP =.7 MPa

Summary 34 The thermal efficiency was examined on the test engine designed for the superlean burn concept by the SIP Gasoline Combustion Team. A high energy ignition system and a high intensity tumble flow generated by a port adapter contributed to the lean limit expansion. The test engine demonstrated, an indicated thermal efficiency of 46%. The result of the PIV measurement showed that a high intensity air flow was generated during the intake stroke with a port adapter. It generates a high intensity of the turbulence, which is essential to enhance a stable Low- Temperature-Combustion of the super-lean mixture in a short duration after the long ignition-delay.

Thank you for your attention 33 Acknowledgment This project was supported by Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP) - Innovative Combustion Technology (Funding agency: JST). Co-Author Prof. Takeshi Yokomori, Keio University Collaborations 28 clusters of SIP Gasoline Combustion Team AICE Gasoline Combustion Committee

for more information 37 34 http://sip.st.keio.ac.jp/

Thank you for your attention 35