Technical Unburned Gas Temperature Measurement in an SI Engine Using Fiber-Optic Laser Interferometry Nobuyuki Kawahara, Eiji Tomita, Kenji Ohnishi, Kazuhiro Goto INTRODUCTION
METHOD OF UNBURNED GAS TEMPERATURE MEASUREMENT Figure 1. Heterodyne interferometrywith fiber-optic sensor M HM AOM PF PBS SML λ/4 λ/2 PT Optical fiber for preserving polarization λ/2 He-Ne laser PBS HM : Mirror PF AOM M : Half mirror PT : Acoustic optic modulator Reference : Polarizing filter signal : Polarizing beam splitter : Micro-lens : 1/4 wave retarder : 1/2 wave retarder : Photo-transister Fiber-optic sensor SML λ/4 M PBS PF PT Test signal Sampling gas
2 P t R Gt L T t t 2 P t 0 R Gt L t Ψ t T t0 R 0 Ψ t t Lt R R Gt P t T t /2 Mirror =13mm SML Sapphire Window Measurement region Optic fiber Figure 2. Photographs of developed fiber-optic sensor
TEMPERATURE MEASUREMENT OF UNBURNED END-GAS IN A TEST ENGINE
Temperature, K 800 600 400 200 φ=1.0, CH4-air mixture Heterodyne Polytropic and adiabatic Flame arrival Spark timing a b c 0 210 240 270 300 330 360 (TDC) Crank angle, deg. Figure 3. Temperature change of unburned gas in a compression-expansion engine Fiber-optic sensor a (346 deg.) b (352 deg.) c (360 deg.) d (366 deg.) Figure 4. Flame propagation in a compression-expansion engine d Spark electrode
TEMPERATURE MEASUREMENT OF UNBURNED GAS IN A PRODUCTION ENGINE Bore x stroke: 70 x 58 mm Compression ratio : 9.5 Single cylinder Air cleaner Laminar flow meter Laminar flow meter Gaseous fuel Vibration isolator He-Ne laser AOM Dynamometer λ/2 PBS HM PBS M Reference signal Static mixer Surge tank PF PT Regulator SML λ/4 PF PT Intake M Test signa Spark plug Figure 5. Experimental set-up Thermocouple IN Ex In. valve Ex. valve Fiber optic sensor Filter Pump Exhaust Fiber optic sensor Spark plug Fuel tank Thermocouple Fiber optic sensor Fiber-optic sensor Spark plug Figure 6. Photographs of spark-ignition engine with fiber-optic sensor
Pressure, MPa Temperature, K 5 4 3 2 1 0 700 500 φ: 0.7 C4H10-Air mixture Volumetric Efficiency : 0.80 Spark timing : 30deg.BTDC 403K 373K Room temp. 300 330 340 350 360 Crank angle, deg. Figure. Unburned temperature history (n-butane)
Temperature, K Pressure, MPa 0.8 0.6 0.4 0.2 0 900 700 500 Table1. Gladstone-Dale constant Temperature, K Pressure, MPa Engine speed: 2000rpm Air-fuel ratio : 12.0 Spark timing 403K 373K Room temp. n-octane GD=10.387 Estimated temp. Propane GD=7.406 n-butane GD=7.477 300 300 330 360 390 420 Crank angle, deg. (TDC) 0 1100 900 Figure 8. Effect of Gladstone-Dale constant on temperature of gasoline-air mixture 0.8 0.6 0.4 0.2 Engine speed Spark timing IMEP [MPa] : 2000,3000rpm : 30deg.BTDC : 0.19 Spark timing 3000rpm 2000rpm n-octane GD=10.387 700 500 Heterodyne Estimated temp. 3000rpm 2000rpm 300 300 330 360 390 420 Crank angle, deg. (TDC) Figure 9. Effect of engine speed on temperature of gasoline-air mixture
Pressure, MPa Temperature, K 3 2 1 0 300 330 360 390 1200 Heterodyne Estimated temp. 900 600 Spark timing: 1560rpm Air-fuelratio : 21.0 Spark timing: 60deg.BTDC Flame arrival timing 300 300 320 340 360 (Spark timing) Crank angle, deg. (TDC) Figure 10. Unburned temperature history under knocking condition
CONCLUSIONS