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Research on Combustion Improvement Techniques by Intake Valve Offset and Squish Effect

Article of Honda R&D Technical Review Vol.25 No.2

Summary

Reported in this paper are the technologies for improvement of combustion efficiency by applying two simple methods to a single cylinder, 110 cm3 displacement, four-stroke, two-valve gasoline engine.
In the first attempt, we tried to improve combustion efficiency by increasing tumble of the air-fuel mixture flow. To increase tumble, we devised an offset intake valve design in which a part of the intake valve was located outside of the cylinder bore. With this offset intake valve configuration, a part of the inlet port perimeter was blocked causing disturbance of air-fuel mixture flow along the cylinder wall that resulted in a strong turbulence. The increased turbulence permitted lean burn at an air-fuel ratio leaner by two points, reducing Indicated Specific Fuel Consumption by 4.8% from that of the base engine. With the intake valve shifted outwards against the cylinder bore, the spacing next to the exhaust valve increased, allowing the intake valve diameter to be enlarged to compensate for the deterioration of the maximum power.
In the second attempt, we tried to improve combustion efficiency by increasing the reversed squish flow of the air-fuel mixture. As the means to increase reversed squish flow, we employed a slant-parallel squish configuration. With the application of this squish arrangement, the margin against knocking generation was enhanced and the compression ratio was increased to 9.5 from the original 9.0 while reducing the Indicated Specific Fuel Consumption by 2.6%. The offset intake valve design coupled with the high compression ratio produced by the slant-parallel squish design lowered the Indicated Specific Fuel Consumption by 6.0% compared to the base engine.

Reference

(1) Nakayama, Y., Suzuki, M., Iwata, Y., Yamano, J.: Development of a 1.3L 2-Plug Engine for the 2002 Model ‘Fit’, Honda R&D Technical Review, Vol. 13, No. 2, p. 43-52
(2) Toulson, E., Huisjen, A., Chen, X., Squibb, C., Zhu, G., Schock, H., Attard, W.: Visualization of Propane and Natural Gas Spark Ignition and Turbulent Jet Ignition Combustion, SAE Technical Paper 2012-32-0002 / JSAE Paper 20129002 (2012)
(3) Mochizuki, K., Kashima, T., Kakinuma, A.: Improvement of Combustion in an SI Engine with Tumble Generator Valve, Journal of Society of Automotive Engineers of Japan, Vol. 50, No. 9, p.38-43 (1996)
(4) Iijima, S., Kubota, R., Kikuchi, K.: Development of Technologies for Improving Fuel Economy of Small Motorcycle Engines, SAE Technical Paper 2009-32-0083 / JSAE Paper 20097083 (2009)
(5) Falfari, S., Brusiani, F., Bianchi, G. M.: Assessment of the Influence of Intake Duct Geometrical Parameters on the Tumble Motion Generation in a Small Gasoline Engine, SAE Technical Paper 2012-32-0095 / JSAE Paper 20129095 (2012)
(6) Iwai, K., Narahara, K., Fujimoto, M., Tabata, M.: Effect of the Intake Valve Lift on Tumble Flow and Combustion Characteristics in an S.I. Engine, JSAE Transaction, Vol. 36, No. 1, January, p. 33-38 (2005)
(7) Tabata, M., Fujimoto, M., Iwai, K.: Knocking Improvement by Tumble Flow and Reverse Squish Flow, Matsuda Technical Reviews, No.21, p.192-198 (2003)
(8) Miyamoto, K., Hoshiba, Y., Hosono, K., Hirao, S.: Enhancement of Combustion by Means of Squish Pistons, Mitsubishi Motors Technical Reviews, No. 18, p.32-41 (2006)
(9) Ueda, T., Okumura, T., Sugiura, S., Kojima, S.: Effects of Squish Area Shape on Knocking, 1998 JSAE Annual Congress Proceedings, No. 982 (9832369),p.99-102
(10) Wotton, C. R. N.: Steady State Flow Bench Port Performance Measurement and Analysis, Ricardo Report DP93/0704 (1993)
(11) Furuhama, S., et al.: Enjinnojiten, Asakura Publishing Co., Ltd., ISBN 4-254-23073-7, p.123-125 (1994) (in Japanese)

Author (organization or company)

Takamori SHIRASUNA(Motorcycle R&D Center)、Hideki SAITO(Motorcycle R&D Center)、Tomokazu NOMURA(Motorcycle R&D Center)

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