Performance of a Compression-Ignition Engine Using Direct-Injection of Liquid Ammonia/DME Mixture Song-Charng Kong Matthias Veltman, Christopher Gross Department of Mechanical Engineering Iowa State University Acknowledgements: Iowa Energy Center; Norm Olson, Kevin Nordmeyer 1 Department of Mechanical Engineering, Iowa State University Background • Motivation • Ammonia (NH3) combustion does not generate CO2 • Hydrogen carrier, renewable, etc. • Challenges • Ammonia is very difficult to ignite • Octane number ~ 130 • Autoignition T ~ 651 ºC (gasoline: 440 ºC; diesel: 225 ºC) • Ammonia flame temperature is lower than diesel flame T • Ammonia emissions can be harmful • Potential high NOx emissions due to fuel-bound nitrogen • Gas phase at atmospheric pressure; Erosive to some materials • Low energy content (~40% of that of diesel fuel per unit mass) 2 Department of Mechanical Engineering, Iowa State University Thermodynamics/Chemistry • Stoichiometric chemical reaction NH30.75 ( O 2 3.76 N 2 ) 1.5 H 2 O 3.32 N 2 Energy Content Latent Energy Boiling (MJ/kg- Fuel Molecule (Air/Fuel) Heat Content Point (°C) s stoichiometric (kJ/kg) (MJ/kg-fuel) mixture) Methanol CH3OH 64.7 6.435 1203 20 2.6900 Ethanol C2H5OH 78.4 8.953 850 26.9 2.7027 Gasoline C7H17 --- 15.291 310 44 2.5781 Diesel C14.4H24.9 --- 14.3217 230 42.38 2.7660 Ammonia NH3 –33.5 6.0456 1371 18.6103 2.6414 3 Department of Mechanical Engineering, Iowa State University Approach #1 • Introduce ammonia to the intake manifold • Create premixed ammonia/air mixture in the cylinder • Inject diesel fuel to initiate combustion • Without modifying the existing injection system Diesel ignition Induce NH3 combustion Burn out premixed NH3 4 Department of Mechanical Engineering, Iowa State University Engine Setup • John Deere (4 cylinder, 4.5 liter) • Operated at various load and speed conditions • Vapor ammonia introduced into the intake duct – after turbo, before manifold Fuel line Fuel line Liquid NH3 tank Induction point 5 Department of Mechanical Engineering, Iowa State University Test Results – Constant NH3 Flow Rate • Engine torque increases suddenly once ammonia is inducted 1400rpm Engine Torque 500 50 Energy replacement (%) NH3 Energy by by NH3 400 1800rpm Engine Torque 500 Energy replacement 40 (%) NH3 Energy by 300 0 by NH3 400 Diesel+ NH3 20 200 300 0 Engine TorqueEngine (ft-lb) -50 -20 100 Diesel baseline Diesel+ NH3 200 Engine TorqueEngine (ft-lb) -40 0 100 Diesel baseline 0 20 40 60 80 100 120 -60 Engine Load (%) 0 -80 0 20 40 60 80 100 120 Engine Load (%) 6 Department of Mechanical Engineering, Iowa State University Test Results – Constant Torque • Fixed at specific diesel fueling, adjusted NH3 flow rate to maintain constant torque • Can achieve 5% diesel / 95% NH3 energy ratio 45 40 35 30 fromContribution 25 NHfrom NH3 20 3 15 Power (kW) Power Power (kW) Power Diesel Only 10 5 diesel NH3 + Diesel 0 0 20 40 60 80 100 Power Contribution from Diesel Fuel (%) 7 Department of Mechanical Engineering, Iowa State University NH3 Exhaust Concentrations • Concentrations vary depending on NH3 fueling rate • Further study is required to reduce NH emissions. 3 Ammonia combustion efficiency 3500 Constant Engine Torque 100 3000 90 2500 80 2000 70 High NH3 60 1500 fueling 50 1000 40 NH3(ppmV) Low NH 500 3 30 fueling Mass Conversion (%) Efficiency 20 0 0 20 40 60 80 100 0 20 40 60 80 100 Diesel Load (%) Power Contribution from Diesel Fuel (%) 8 Department of Mechanical Engineering, Iowa State University Approach #2 Fuel injector • Use direct liquid fuel injection • Confine combustion mixture near the center • To reduce exhaust ammonia emissions • Ignition source – dimethyl ether (CH3-O-CH3) • Mixture of DME and NH3 • Fuel mixing and storage at high pressure • New fuel injection system – without fuel return • Injection pump, injector, electronic control 9 Department of Mechanical Engineering, Iowa State University Engine Setup • Yanmar diesel engine (L70V, 320 c.c.) • Rated power at 6.26 hp at 3480 rpm • Develop new fuel injection and engine control systems • Bosch GDI type injector (up to 200 bar injection pressure) Department of Mechanical Engineering, Iowa State University Setup • Mixing and storage of ammonia/DME at high pressure • Exhaust emissions measurements • Horiba MEXA-7100DEGR (CO2, CO, O2, HC) • Horiba 1170NX (NOx, NH3) Emissions analyzers • AVL Smoke Meter (PM) Fuel mixing system Department of Mechanical Engineering, Iowa State University Operating Conditions Operating map using original diesel injection system 12 Department of Mechanical Engineering, Iowa State University Test Results • Baseline operation using 100% DME • Explore operating range before using NH3/DME mixture • For each operating point, various start-of-injection timings were tested • Provide flexibility for future optimization SOI= –30 ~ 20 BTDC SOI= –35 ~ 20 BTDC SOI= –30 ~ 0 ATDC SOI= –30 ~ 20 BTDC SOI= –25 ~ 5 BTDC 13 Department of Mechanical Engineering, Iowa State University 100% DME • Mode 7 (2548 rpm) emissions 100% DME 100% DME 0.01 500 2000 0.008 400 Soot - Smoke number 1500 NOx (ppm) 0.006 300 CO 1000 Soot (FSN) 0.004 200 CO & HC (ppm) NOx 500 0.002 100 HC 0 0 0 -30 -25 -20 -15 -10 -5 0 -30 -25 -20 -15 -10 -5 0 SOI (ATDC) SOI (ATDC) 14 Department of Mechanical Engineering, Iowa State University Effects of Ammonia Combustion (Mode 7) • 100%DME vs. 20%NH3/80%DME • Soot remains at low level • NOx increases due to fuel-bound nitrogen Mode 7 (2548 rpm) Mode 7 (2548 rpm) 800 0.01 700 0.008 600 100%DME 500 0.006 20%NH3/80%DME 400 NOx (ppm) NOx Soot (FSN) 0.004 300 200 20%NH3/80%DME 0.002 100%DME 100 0 0 -30 -25 -20 -15 -10 -5 0 -30 -25 -20 -15 -10 -5 0 SOI (ATDC) SOI (ATDC) 15 Department of Mechanical Engineering, Iowa State University Effects of Ammonia Combustion (Mode 7) • 100%DME vs. 20%NH3/80%DME • Lower combustion temperature of ammonia causes more CO and HC emissions • Implication to fuel efficiency Mode 7 (2548 rpm) Mode 7 (2548 rpm) 600 4000 3500 500 3000 20%NH3/80%DME 400 20%NH3/80%DME 2500 2000 300 CO (ppm) HC (ppm) 1500 200 1000 100%DME 100%DME 100 500 0 0 -30 -25 -20 -15 -10 -5 0 -30 -25 -20 -15 -10 -5 0 SOI (ATDC) SOI (ATDC) 16 Department of Mechanical Engineering, Iowa State University Effects of Ammonia Combustion (Mode 21) • Comparable combustion and fuel efficiency at this lower speed Mode 21 (2200 rpm) Model 21 (2200 rpm) 0.02 2500 2500 100%DME 20%NH3 20%NH3/80%DME 2000 2000 0.015 CO 1500 1500 0.01 Soot (FSN) Model 21 (2200 rpm) 1000 1000 600 CO & HC (ppm) DME-HC 20%NH3 0.005 500 500 HC 500 100%DME 400 20%NH3/80%DME 0 0 0 -35 -30 -25 -20 -15 -10 -5 0 5 -35 -30 -25 -20 -15 -10 -5 0 5 SOI (ATDC) 300 SOI (ATDC) NOx (ppm) 200 100 100%DME 0 17 -35 -30 -25 -20 -15 -10 -5 0 5 SOI (ATDC) Department of Mechanical Engineering, Iowa State University Effects of Ammonia Combustion • Exhaust ammonia emissions much lower than Approach#1 • Direct injection strategy benefits exhaust ammonia emissions NH3 Emissions (20%NH3/80%DME) 400 350 Mode 20 300 (2200 rpm, medium) 250 NH3 (ppm) 200 Mode 7 (2548 rpm, low) 150 100 50 Mode 21 (2200 rpm, low) 0 -40 -35 -30 -25 -20 -15 -10 -5 0 SOI (ATDC) 18 Department of Mechanical Engineering, Iowa State University Alternate Injection Strategy • To extend the operating range • Proposed strategies • Double fuel injections x % (100–x) % • Offer flexibilities in fuel delivery • Used in industry for emissions and noise pilot main reduction • New fuel injector • Original: single hole • Alternate: eight holes – help with air utilization 19 Department of Mechanical Engineering, Iowa State University Double Injection, 100% DME • Current system modified for using double injections • Engine operations possible using double injections • Comparable fuel efficiency and emissions • Results based on Mode 7 (2548 rpm) • Pilot SOI= –45 ~ –35 ATDC Double Injections (Mode 7) • Pilot quantity=30% of total fuel 0.01 600 • Main SOI= –10 ATDC 550 0.008 Soot - Smoke number 500 NOx (ppm) 0.006 • Exploring other conditions 450 • Varying the three injection variables Soot (FSN) 0.004 400 • Other operating points 0.002 NOx 350 0 300 -50 -45 -40 -35 -30 Pilot SOI (ATDC) 20 Department of Mechanical Engineering, Iowa State University Multi-Hole Injector • Change from single hole to 8 holes • Higher exhaust NOx – may imply higher combustion temperature to sustain higher load operation • Exploring combination of using 8-hole injector in combination with double injections Mode 7 (2548 rpm) Mode 7 (2548 rpm) 0.025 600 0.02 500 400 0.015 300 Soot (FSN) 0.01 (ppm) NOx 8 holes Single hole 200 0.005 100 Single hole 8 holes 0 0 -30 -25 -20 -15 -10 -5 0 -30 -25 -20 -15 -10 -5 0 21 SOI (ATDC) SOI (ATDC) Department of Mechanical Engineering, Iowa State University Summary • Demonstrated ammonia combustion in diesel engines • Port induction of ammonia coupled with direct-injection diesel fuel • Exhaust ammonia level at “thousands of ppm” under the conditions studied • Direct injection of ammonia/DME • Exhaust ammonia level at “hundreds of ppm” under the conditions studied • Exploring optimal injection strategies for ammonia combustion • Perspectives – effects of engine size • Challenges for small engine: more heat loss, higher engine speed required, lower fuel injection pressure • Large engine will favor ammonia combustion 22 Department of Mechanical Engineering, Iowa State University .