A Successful Approach to Reduce Emissions Using a Group Holes Nozzle. Yoshiaki NISHIJIMA Makoto MASHIDA Satoru SASAKI Kenji OSHIMA

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1 A Successful Approach to Reduce Emissions Using a Group Holes Nozzle Yoshiaki NISHIJIMA Makoto MASHIDA Satoru SASAKI Kenji OSHIMA The Common Rail System, (CRS), has revolutionized diesel engines. DENSO has been working on CRS technologies since they were first developed. This report describes the technology to simultaneously reduce NOx and PM through an innovative Group Holes Nozzle concept. We can obtain a more homogeneous, lean air-fuel mixture through Group Holes Nozzles, and by the addition of a cooled EGR, achieve pre-mixed combustion. This has underscored the potential in clearing future emission standards. Key words : Diesel engine, Fuel injection, Nozzle, Spray, Common Rail System, Pre-mixed combustion PM (g/km) Diesel technologies st step Pre-mixed combustion - Common rail technologies - EGR cooler, Intercooler (Reducing compression ratio) nd step Catalyzed DPF.4... nd step Future regulation EURO4 BASE st step... NOx (g/km) Fig. Scenario for emission regulation

2 Air flow meter Substrate (cordierite) Exhaust gas temperature sensor Differential pressure sensor EGR cooler EGR valve Intercooler Thrott le body (DC motor) Manifold pressure sensor Common rail system Injector High-pressure pump Rail Engine control unit Pre-mixed combustion Air management Aftertreatment UHEGO sensor Fig. Engine management system Technologies More homogeneous spray Equivalence ratio 5 4 Conventional combustion Pre-mixed combustion Pre-mixed combustion area Soot Gasoline Concerns Lower local Equivalence ratio Lower local Combustion temperature Higher injection pressure Higher response injector Smaller nozzle holes - Group holes nozzle Injector technologies Low temperature combustion EGR cooler, Intercooler NOx 4 6 Combustion temperature (K) Reducing compression ratio Fig. Region of NOx and PM

3 SMD (µm) Hole configuration Hole dia. x Number Hole layout Hydraulic flow (cm / min) Single hole Two-hole-group Three-hole-group φ.7 φ.9 x φ.78 x 8 Parallel Single hole Two-hole-group Three-hole-group # # # # # # # # # φ.7 φ.9 x φ.78 x More group holes = better atomization (smaller dia.) Injector Group holes nozzle (Multiple small holes) Conventional nozzle (Single large hole) Measurement condition Fuel pressure: 8MPa Ambient temperature: 9K.5ms after injection start Group holes Measuring point # Nozzle # # Fig. 4 Group holes nozzle concept Fig. 5 Nozzle specifications and SMD Injector Nd: YAG laser Mirror Band-pass filter Stereoscope Intensified CCD camera Ambient pressure 5MPa Ambient temperature 87K Injection pressure 8MPa Photographic time.7ms after injection start Fig. 6 Experimental apparatus

4 Conventional single hole nozzle ( φ.9 x ) Group holes nozzle ( φ.9 x ) Fig. 7 Spray observation Equivalence ratio High Low Liquid phase Gas phase Liquid phase Gas phase Larger gas phase area Injection pressure: 8MPa Injection quantity: mm /st Ambient: 87K, 5.MPa After injection start:.7ms Single hole ( φ.9 x ) Higher droplet density in spray center with group holes Higher latent heat due to droplet vaporization.6ms after inj. stant Single hole φ.7 row group φ.9 x row group φ.78 x Lower atmospheric temperature in spray center Measurement Droplet vaporization delay row group ( φ.9 x ) Mixture temperature (K) 7 9 Stronger liquid phase penetration Residual droplet vaporization Stronger gas phase penetration Simulation Ambient temperature: 87K Pi = 8MPa, Q=mm /st High Equivalence ratiolow Fig. 8 Spray simulation Fig. 9 Spray measurement and spray simulation

5 Needle iift (mm) ROHR (J/deg) Mean gas temperature (K) NOx (g/kwh) PM (g/kwh) FC (g/kwh) Noise (dba) Combustion analysis Pre-mixed combustion - 4 Crank angle (deg. ATDC) Pre-mixed combustion NE: 4r/min T: 5%load (9Nm) Pc: 4MPa Nozzle: Group holes Injection start (deg. C A ATDC) Combustion visualization Spray LIP ATDC ATDC ATDC5 ATDC ATDC Needle life ROHR Crank angle (deg. ATDC) ATDC ATDC ATDC5 ATDC ATDC Needle life ROHR Crank angle (deg. ATDC) Fig. Combustion observation NE: 4r/min T: 5%load (9Nm) Pc: 94MPa Nozzle: Conventional NE: 4r/min T: 5%load (9Nm) Pc: 4MPa Nozzle: Group holes Pre-mixed combustion: ATDC deg. injection start Fig. Engine test result

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