Abstract

An approach to multiplex in-cylinder pressure measurement that utilizes a single-mode optical fiber with specific refractive-index composition has been proposed. The sensing fiber has been designed to show a certain amount of optical power loss with a small change in the fiber-local-bend radius. Along with pressure-transferring diaphragms the sensing fiber was embedded into the head gasket of a four-cylinder gasoline engine. The internal-pressure change in each combustion chamber was detected on the basis of bending power loss in the fiber. Combustion pressure peaks for each cylinder were clearly observed.

© 1996 Optical Society of America

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  1. Y. Hata, M. Asano, “New trends in electronic engine control—to the next stage,” SAE paper860592 (Society of Automotive Engineers, Warrendale, Pa., 1986) and references therein;G.W. Pestana, “Engine control methods using combustion pressure feedback,” SAE paper890758 (Society of Automotive Engineers, Warrendale, Pa., 1989);H. Kusakabe, T. Okauchi, M. Takigawa, “A cylinder pressure sensor for internal combustion engine,” SAE paper920701 (Society of Automotive Engineers, Warrendale, Pa., 1992).;W. Herden, M. Kusell, “A new combustion pressure sensor for advanced engine management,” SAE paper940379 (Society of Automotive Engineers, Warrendale, Pa., 1994).
  2. J. B. Heywood, Internal Combustion Engine Fundamentals (McGraw-Hill, New York, 1988), Chap. 9, pp. 450–470;A. By, B. Kempinski, J. M. Rife, “Knock in spark ignition engine,” SAE paper810147 (Society of Automotive Engineers, Warrendale, Pa., 1981);M. D. Checkel, J. D. Dale, “Computerized knock detection from engine pressure records,” SAE paper860028 (Society of Automotive Engineers, Warrendale, Pa., 1986).
  3. T. Sasayama, S. Suzuki, M. Amano, N. Kurihara, S. Sakamoto, S. Suda, “An advanced engine control system using combustion pressure sensors,” in Proceedings of IECON '85 (IEEE, New York, 1985), Vol. 1, pp. 68–72.
  4. M. Takeuchi, K. Tsukada, Y. Nonomura, Y. Omura, Y. Chujou, “A combustion pressure sensor utilizing silicon piezoresistive effect,” SAE paper930351 (Society of Automotive Engineers, Warrendale, Pa., 1993).
  5. T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical fiber sensor technology,” IEEE J. Quantum Electron. QE-14, 626–665 (1982).
  6. J. A. Bucaro, J. H. Cole, “Acousto-optics sensor development,” in Proceedings of EASCON '79, IEEE Publication 79CH1476-1, Aerospace and Electronic Systems (Institute of Electrical and Electronics, Engineers, New York, 1979), pp. 572–580;J. N. Fields, J. H. Cole, “Fiber microbend acoustic sensor,” Appl. Opt. 19, 3265–3267 (1980);J.W. Berthold, “Historical review of microbend fiber-optic sensors,”J. Lightwave Technol. 13, 1193–1199 (1995).
  7. Besides the core–cladding structure explained in Section 2, we also tried to use a kind of elliptical jacket structure to obtain a stable sensing motion. The prestrained sensing fiber is not affected by twists of the fiber or other mechanical perturbations. A rather sharp decrease in the radiation modes is also expected. A detailed study of this kind of pressure-sensing fiber is now under way and will be reported elsewhere.
  8. D. Marcuse, “Curvature loss formula for optical fibers,” J. Opt. Soc. Am. 66, 216–220 (1976).
  9. A. W. Snyder, J. D. Love, Optical Waveguide Theory (Chapman & Hall, London, 1983), Chap. 11; Chap. 12, pp. 209–279.
  10. W. A. Gambling, H. Matsumura, C. M. Ragdale, R. A. Sammut, “Measurement of radiation loss in curved singlemode fibers,”Microwave Opt. Acoust. 2, 134–140 (1978).
  11. Because the result includes both the effect of uniform bend loss and transition power loss of the fiber, the graph in Fig. 4 depends on the size of the sensing part. However, the approximately size-independent nature of the sensor response is experimentally observed, which may be explained by a smooth layout of the sensing fiber. Use of parameter R is convenient when we design the mechanical structure of the sensing part.
  12. R. A. Atkins, J. H. Gardner, W. N. Gibler, C. E. Lee, M. D. Oakland, M. O. Spears, V. P. Swenson, H. F. Taylor, J. J. McCoy, G. Beshouri, “Fiber-optic pressure sensors for internal combustion engines,”Appl. Opt. 33,1315–1320 (1994).
  13. M. T. Wlodarczyk, D. Vokovich, V. Astrakhan, M. Kluzner, O. Ulrich, “Fiber-optic pressure sensor for combustion monitoring and control,” in Chemical, Biochemical, and Environmental Fiber Sensors III, M. T. Wlodarczyk, ed., Proc. Soc. Photo-Opt. Instrum. Eng.1587, 4–10 (1991);G. Heand, M. T. Wlodarczyk, “Evaluation of a spark-plug-integrated fiber-optic combustion pressure sensor,” SAE paper940381 (Society of Automotive Engineers, Warrendale, Pa., 1994).
  14. R. Olshansky, R. D. Maurer, “Tensile strength and fatigue of optical fibers,” J. Appl. Phys. 47, 4497–4499 (1976);Y. Mitsunaga, Y. Katsuyama, H. Kobayashi, Y. Ishida, “Failure prediction for long length optical fiber based on proof testing,”J. Appl. Phys. 53, 4847–4853 (1982).

1994 (1)

1982 (1)

T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical fiber sensor technology,” IEEE J. Quantum Electron. QE-14, 626–665 (1982).

1978 (1)

W. A. Gambling, H. Matsumura, C. M. Ragdale, R. A. Sammut, “Measurement of radiation loss in curved singlemode fibers,”Microwave Opt. Acoust. 2, 134–140 (1978).

1976 (2)

D. Marcuse, “Curvature loss formula for optical fibers,” J. Opt. Soc. Am. 66, 216–220 (1976).

R. Olshansky, R. D. Maurer, “Tensile strength and fatigue of optical fibers,” J. Appl. Phys. 47, 4497–4499 (1976);Y. Mitsunaga, Y. Katsuyama, H. Kobayashi, Y. Ishida, “Failure prediction for long length optical fiber based on proof testing,”J. Appl. Phys. 53, 4847–4853 (1982).

Amano, M.

T. Sasayama, S. Suzuki, M. Amano, N. Kurihara, S. Sakamoto, S. Suda, “An advanced engine control system using combustion pressure sensors,” in Proceedings of IECON '85 (IEEE, New York, 1985), Vol. 1, pp. 68–72.

Asano, M.

Y. Hata, M. Asano, “New trends in electronic engine control—to the next stage,” SAE paper860592 (Society of Automotive Engineers, Warrendale, Pa., 1986) and references therein;G.W. Pestana, “Engine control methods using combustion pressure feedback,” SAE paper890758 (Society of Automotive Engineers, Warrendale, Pa., 1989);H. Kusakabe, T. Okauchi, M. Takigawa, “A cylinder pressure sensor for internal combustion engine,” SAE paper920701 (Society of Automotive Engineers, Warrendale, Pa., 1992).;W. Herden, M. Kusell, “A new combustion pressure sensor for advanced engine management,” SAE paper940379 (Society of Automotive Engineers, Warrendale, Pa., 1994).

Astrakhan, V.

M. T. Wlodarczyk, D. Vokovich, V. Astrakhan, M. Kluzner, O. Ulrich, “Fiber-optic pressure sensor for combustion monitoring and control,” in Chemical, Biochemical, and Environmental Fiber Sensors III, M. T. Wlodarczyk, ed., Proc. Soc. Photo-Opt. Instrum. Eng.1587, 4–10 (1991);G. Heand, M. T. Wlodarczyk, “Evaluation of a spark-plug-integrated fiber-optic combustion pressure sensor,” SAE paper940381 (Society of Automotive Engineers, Warrendale, Pa., 1994).

Atkins, R. A.

Beshouri, G.

Bucaro, J. A.

T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical fiber sensor technology,” IEEE J. Quantum Electron. QE-14, 626–665 (1982).

J. A. Bucaro, J. H. Cole, “Acousto-optics sensor development,” in Proceedings of EASCON '79, IEEE Publication 79CH1476-1, Aerospace and Electronic Systems (Institute of Electrical and Electronics, Engineers, New York, 1979), pp. 572–580;J. N. Fields, J. H. Cole, “Fiber microbend acoustic sensor,” Appl. Opt. 19, 3265–3267 (1980);J.W. Berthold, “Historical review of microbend fiber-optic sensors,”J. Lightwave Technol. 13, 1193–1199 (1995).

Chujou, Y.

M. Takeuchi, K. Tsukada, Y. Nonomura, Y. Omura, Y. Chujou, “A combustion pressure sensor utilizing silicon piezoresistive effect,” SAE paper930351 (Society of Automotive Engineers, Warrendale, Pa., 1993).

Cole, J. H.

T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical fiber sensor technology,” IEEE J. Quantum Electron. QE-14, 626–665 (1982).

J. A. Bucaro, J. H. Cole, “Acousto-optics sensor development,” in Proceedings of EASCON '79, IEEE Publication 79CH1476-1, Aerospace and Electronic Systems (Institute of Electrical and Electronics, Engineers, New York, 1979), pp. 572–580;J. N. Fields, J. H. Cole, “Fiber microbend acoustic sensor,” Appl. Opt. 19, 3265–3267 (1980);J.W. Berthold, “Historical review of microbend fiber-optic sensors,”J. Lightwave Technol. 13, 1193–1199 (1995).

Dandridge, A.

T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical fiber sensor technology,” IEEE J. Quantum Electron. QE-14, 626–665 (1982).

Gambling, W. A.

W. A. Gambling, H. Matsumura, C. M. Ragdale, R. A. Sammut, “Measurement of radiation loss in curved singlemode fibers,”Microwave Opt. Acoust. 2, 134–140 (1978).

Gardner, J. H.

Giallorenzi, T. G.

T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical fiber sensor technology,” IEEE J. Quantum Electron. QE-14, 626–665 (1982).

Gibler, W. N.

Hata, Y.

Y. Hata, M. Asano, “New trends in electronic engine control—to the next stage,” SAE paper860592 (Society of Automotive Engineers, Warrendale, Pa., 1986) and references therein;G.W. Pestana, “Engine control methods using combustion pressure feedback,” SAE paper890758 (Society of Automotive Engineers, Warrendale, Pa., 1989);H. Kusakabe, T. Okauchi, M. Takigawa, “A cylinder pressure sensor for internal combustion engine,” SAE paper920701 (Society of Automotive Engineers, Warrendale, Pa., 1992).;W. Herden, M. Kusell, “A new combustion pressure sensor for advanced engine management,” SAE paper940379 (Society of Automotive Engineers, Warrendale, Pa., 1994).

Heywood, J. B.

J. B. Heywood, Internal Combustion Engine Fundamentals (McGraw-Hill, New York, 1988), Chap. 9, pp. 450–470;A. By, B. Kempinski, J. M. Rife, “Knock in spark ignition engine,” SAE paper810147 (Society of Automotive Engineers, Warrendale, Pa., 1981);M. D. Checkel, J. D. Dale, “Computerized knock detection from engine pressure records,” SAE paper860028 (Society of Automotive Engineers, Warrendale, Pa., 1986).

Kluzner, M.

M. T. Wlodarczyk, D. Vokovich, V. Astrakhan, M. Kluzner, O. Ulrich, “Fiber-optic pressure sensor for combustion monitoring and control,” in Chemical, Biochemical, and Environmental Fiber Sensors III, M. T. Wlodarczyk, ed., Proc. Soc. Photo-Opt. Instrum. Eng.1587, 4–10 (1991);G. Heand, M. T. Wlodarczyk, “Evaluation of a spark-plug-integrated fiber-optic combustion pressure sensor,” SAE paper940381 (Society of Automotive Engineers, Warrendale, Pa., 1994).

Kurihara, N.

T. Sasayama, S. Suzuki, M. Amano, N. Kurihara, S. Sakamoto, S. Suda, “An advanced engine control system using combustion pressure sensors,” in Proceedings of IECON '85 (IEEE, New York, 1985), Vol. 1, pp. 68–72.

Lee, C. E.

Love, J. D.

A. W. Snyder, J. D. Love, Optical Waveguide Theory (Chapman & Hall, London, 1983), Chap. 11; Chap. 12, pp. 209–279.

Marcuse, D.

Matsumura, H.

W. A. Gambling, H. Matsumura, C. M. Ragdale, R. A. Sammut, “Measurement of radiation loss in curved singlemode fibers,”Microwave Opt. Acoust. 2, 134–140 (1978).

Maurer, R. D.

R. Olshansky, R. D. Maurer, “Tensile strength and fatigue of optical fibers,” J. Appl. Phys. 47, 4497–4499 (1976);Y. Mitsunaga, Y. Katsuyama, H. Kobayashi, Y. Ishida, “Failure prediction for long length optical fiber based on proof testing,”J. Appl. Phys. 53, 4847–4853 (1982).

McCoy, J. J.

Nonomura, Y.

M. Takeuchi, K. Tsukada, Y. Nonomura, Y. Omura, Y. Chujou, “A combustion pressure sensor utilizing silicon piezoresistive effect,” SAE paper930351 (Society of Automotive Engineers, Warrendale, Pa., 1993).

Oakland, M. D.

Olshansky, R.

R. Olshansky, R. D. Maurer, “Tensile strength and fatigue of optical fibers,” J. Appl. Phys. 47, 4497–4499 (1976);Y. Mitsunaga, Y. Katsuyama, H. Kobayashi, Y. Ishida, “Failure prediction for long length optical fiber based on proof testing,”J. Appl. Phys. 53, 4847–4853 (1982).

Omura, Y.

M. Takeuchi, K. Tsukada, Y. Nonomura, Y. Omura, Y. Chujou, “A combustion pressure sensor utilizing silicon piezoresistive effect,” SAE paper930351 (Society of Automotive Engineers, Warrendale, Pa., 1993).

Priest, R. G.

T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical fiber sensor technology,” IEEE J. Quantum Electron. QE-14, 626–665 (1982).

Ragdale, C. M.

W. A. Gambling, H. Matsumura, C. M. Ragdale, R. A. Sammut, “Measurement of radiation loss in curved singlemode fibers,”Microwave Opt. Acoust. 2, 134–140 (1978).

Rashleigh, S. C.

T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical fiber sensor technology,” IEEE J. Quantum Electron. QE-14, 626–665 (1982).

Sakamoto, S.

T. Sasayama, S. Suzuki, M. Amano, N. Kurihara, S. Sakamoto, S. Suda, “An advanced engine control system using combustion pressure sensors,” in Proceedings of IECON '85 (IEEE, New York, 1985), Vol. 1, pp. 68–72.

Sammut, R. A.

W. A. Gambling, H. Matsumura, C. M. Ragdale, R. A. Sammut, “Measurement of radiation loss in curved singlemode fibers,”Microwave Opt. Acoust. 2, 134–140 (1978).

Sasayama, T.

T. Sasayama, S. Suzuki, M. Amano, N. Kurihara, S. Sakamoto, S. Suda, “An advanced engine control system using combustion pressure sensors,” in Proceedings of IECON '85 (IEEE, New York, 1985), Vol. 1, pp. 68–72.

Sigel, G. H.

T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical fiber sensor technology,” IEEE J. Quantum Electron. QE-14, 626–665 (1982).

Snyder, A. W.

A. W. Snyder, J. D. Love, Optical Waveguide Theory (Chapman & Hall, London, 1983), Chap. 11; Chap. 12, pp. 209–279.

Spears, M. O.

Suda, S.

T. Sasayama, S. Suzuki, M. Amano, N. Kurihara, S. Sakamoto, S. Suda, “An advanced engine control system using combustion pressure sensors,” in Proceedings of IECON '85 (IEEE, New York, 1985), Vol. 1, pp. 68–72.

Suzuki, S.

T. Sasayama, S. Suzuki, M. Amano, N. Kurihara, S. Sakamoto, S. Suda, “An advanced engine control system using combustion pressure sensors,” in Proceedings of IECON '85 (IEEE, New York, 1985), Vol. 1, pp. 68–72.

Swenson, V. P.

Takeuchi, M.

M. Takeuchi, K. Tsukada, Y. Nonomura, Y. Omura, Y. Chujou, “A combustion pressure sensor utilizing silicon piezoresistive effect,” SAE paper930351 (Society of Automotive Engineers, Warrendale, Pa., 1993).

Taylor, H. F.

Tsukada, K.

M. Takeuchi, K. Tsukada, Y. Nonomura, Y. Omura, Y. Chujou, “A combustion pressure sensor utilizing silicon piezoresistive effect,” SAE paper930351 (Society of Automotive Engineers, Warrendale, Pa., 1993).

Ulrich, O.

M. T. Wlodarczyk, D. Vokovich, V. Astrakhan, M. Kluzner, O. Ulrich, “Fiber-optic pressure sensor for combustion monitoring and control,” in Chemical, Biochemical, and Environmental Fiber Sensors III, M. T. Wlodarczyk, ed., Proc. Soc. Photo-Opt. Instrum. Eng.1587, 4–10 (1991);G. Heand, M. T. Wlodarczyk, “Evaluation of a spark-plug-integrated fiber-optic combustion pressure sensor,” SAE paper940381 (Society of Automotive Engineers, Warrendale, Pa., 1994).

Vokovich, D.

M. T. Wlodarczyk, D. Vokovich, V. Astrakhan, M. Kluzner, O. Ulrich, “Fiber-optic pressure sensor for combustion monitoring and control,” in Chemical, Biochemical, and Environmental Fiber Sensors III, M. T. Wlodarczyk, ed., Proc. Soc. Photo-Opt. Instrum. Eng.1587, 4–10 (1991);G. Heand, M. T. Wlodarczyk, “Evaluation of a spark-plug-integrated fiber-optic combustion pressure sensor,” SAE paper940381 (Society of Automotive Engineers, Warrendale, Pa., 1994).

Wlodarczyk, M. T.

M. T. Wlodarczyk, D. Vokovich, V. Astrakhan, M. Kluzner, O. Ulrich, “Fiber-optic pressure sensor for combustion monitoring and control,” in Chemical, Biochemical, and Environmental Fiber Sensors III, M. T. Wlodarczyk, ed., Proc. Soc. Photo-Opt. Instrum. Eng.1587, 4–10 (1991);G. Heand, M. T. Wlodarczyk, “Evaluation of a spark-plug-integrated fiber-optic combustion pressure sensor,” SAE paper940381 (Society of Automotive Engineers, Warrendale, Pa., 1994).

Appl. Opt. (1)

IEEE J. Quantum Electron. (1)

T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical fiber sensor technology,” IEEE J. Quantum Electron. QE-14, 626–665 (1982).

J. Appl. Phys. (1)

R. Olshansky, R. D. Maurer, “Tensile strength and fatigue of optical fibers,” J. Appl. Phys. 47, 4497–4499 (1976);Y. Mitsunaga, Y. Katsuyama, H. Kobayashi, Y. Ishida, “Failure prediction for long length optical fiber based on proof testing,”J. Appl. Phys. 53, 4847–4853 (1982).

J. Opt. Soc. Am. (1)

Microwave Opt. Acoust. (1)

W. A. Gambling, H. Matsumura, C. M. Ragdale, R. A. Sammut, “Measurement of radiation loss in curved singlemode fibers,”Microwave Opt. Acoust. 2, 134–140 (1978).

Other (9)

Because the result includes both the effect of uniform bend loss and transition power loss of the fiber, the graph in Fig. 4 depends on the size of the sensing part. However, the approximately size-independent nature of the sensor response is experimentally observed, which may be explained by a smooth layout of the sensing fiber. Use of parameter R is convenient when we design the mechanical structure of the sensing part.

M. T. Wlodarczyk, D. Vokovich, V. Astrakhan, M. Kluzner, O. Ulrich, “Fiber-optic pressure sensor for combustion monitoring and control,” in Chemical, Biochemical, and Environmental Fiber Sensors III, M. T. Wlodarczyk, ed., Proc. Soc. Photo-Opt. Instrum. Eng.1587, 4–10 (1991);G. Heand, M. T. Wlodarczyk, “Evaluation of a spark-plug-integrated fiber-optic combustion pressure sensor,” SAE paper940381 (Society of Automotive Engineers, Warrendale, Pa., 1994).

A. W. Snyder, J. D. Love, Optical Waveguide Theory (Chapman & Hall, London, 1983), Chap. 11; Chap. 12, pp. 209–279.

J. A. Bucaro, J. H. Cole, “Acousto-optics sensor development,” in Proceedings of EASCON '79, IEEE Publication 79CH1476-1, Aerospace and Electronic Systems (Institute of Electrical and Electronics, Engineers, New York, 1979), pp. 572–580;J. N. Fields, J. H. Cole, “Fiber microbend acoustic sensor,” Appl. Opt. 19, 3265–3267 (1980);J.W. Berthold, “Historical review of microbend fiber-optic sensors,”J. Lightwave Technol. 13, 1193–1199 (1995).

Besides the core–cladding structure explained in Section 2, we also tried to use a kind of elliptical jacket structure to obtain a stable sensing motion. The prestrained sensing fiber is not affected by twists of the fiber or other mechanical perturbations. A rather sharp decrease in the radiation modes is also expected. A detailed study of this kind of pressure-sensing fiber is now under way and will be reported elsewhere.

Y. Hata, M. Asano, “New trends in electronic engine control—to the next stage,” SAE paper860592 (Society of Automotive Engineers, Warrendale, Pa., 1986) and references therein;G.W. Pestana, “Engine control methods using combustion pressure feedback,” SAE paper890758 (Society of Automotive Engineers, Warrendale, Pa., 1989);H. Kusakabe, T. Okauchi, M. Takigawa, “A cylinder pressure sensor for internal combustion engine,” SAE paper920701 (Society of Automotive Engineers, Warrendale, Pa., 1992).;W. Herden, M. Kusell, “A new combustion pressure sensor for advanced engine management,” SAE paper940379 (Society of Automotive Engineers, Warrendale, Pa., 1994).

J. B. Heywood, Internal Combustion Engine Fundamentals (McGraw-Hill, New York, 1988), Chap. 9, pp. 450–470;A. By, B. Kempinski, J. M. Rife, “Knock in spark ignition engine,” SAE paper810147 (Society of Automotive Engineers, Warrendale, Pa., 1981);M. D. Checkel, J. D. Dale, “Computerized knock detection from engine pressure records,” SAE paper860028 (Society of Automotive Engineers, Warrendale, Pa., 1986).

T. Sasayama, S. Suzuki, M. Amano, N. Kurihara, S. Sakamoto, S. Suda, “An advanced engine control system using combustion pressure sensors,” in Proceedings of IECON '85 (IEEE, New York, 1985), Vol. 1, pp. 68–72.

M. Takeuchi, K. Tsukada, Y. Nonomura, Y. Omura, Y. Chujou, “A combustion pressure sensor utilizing silicon piezoresistive effect,” SAE paper930351 (Society of Automotive Engineers, Warrendale, Pa., 1993).

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Figures (11)

Fig. 1
Fig. 1

Schematic structure of the operating principle for the fiber-optic multicylinder pressure sensor.

Fig. 2
Fig. 2

Core–cladding index profile of the pressure-sensing fiber.

Fig. 3
Fig. 3

Cross-sectional view of a sensing part.

Fig. 4
Fig. 4

Optical power change of the sensing fiber set into a sensing part.

Fig. 5
Fig. 5

Estimation of the sensor frequency response. f fixed(free) denotes the eigenfrequency of the bent fiber with fixed (or free) ends. Actual cutoff frequency f is expected to satisfy the condition f free < f < f fixed.

Fig. 6
Fig. 6

Experimental arrangement of the sensing fiber in the engine head gasket. The sensing fiber is set in the optical fiber groove.

Fig. 7
Fig. 7

Three metal pieces combined to make each sensing part.

Fig. 8
Fig. 8

Static-pressure responses of each sensing part.

Fig. 9
Fig. 9

Prototype sensor output (Ch. 1) for a four-cylinder engine. The signal in Ch. 2 is the reference sensor output for one cylinder, and the signal in Ch. 3 shows the injection trigger of the same cylinder.

Fig. 10
Fig. 10

Prototype sensor output (Ch. 1) for one cylinder and the reference sensor signal (Ch. 2) of the same cylinder.

Fig. 11
Fig. 11

Output signal change in an artificial misfiring condition (denoted by circles).

Equations (4)

Equations on this page are rendered with MathJax. Learn more.

V = a n core ( 2 π λ ) 2 Δ n ,
Δ n = n core n clad n core ,
f fixed = 1 2 π d w 2 ( 12 E ρ ) 1 / 2 ( for the beam with fixed ends), 
f free = 1 2 π d w 2 ( 3 E ρ ) 1 / 2 ( for the beam with free ends), 

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