Effects of azeotropic phenomena in ethanol-blended gasoline on liquid film evaporation characteristics during cold start

Siryu Sato･Kenji Tamura･Tomoki Nagata (Waseda University)･Kenji Uchida･Junki Hori･Shinya Iida (Mazda)･Jin Kusaka (Waseda University)

Liquid film evaporation characteristics of ethanol-blended fuels were investigated using a constant-volume chamber and 3D-CFD. Ethanol was found to promote the evaporation of high-boiling-point components through azeotropy, a phenomenon further confirmed in simulations incorporating an azeotropic correction model. The numerical results led to the conclusion that evaporation characteristics are governed by two competing factors related to temperature drop: the enhancement of evaporation rates due to azeotropy and the increase in latent heat of vaporization.

A Fundamental Study on the Impact of Light (Ethanol) and Heavy Components on Gasoline Deposits under Heating–Cooling Cycles

Tomoharu Kataoka (Toyota Motor)･Yoshinori Nakayama (SOKEN)

In recent years, the implementation of ethanol and synthetic gasoline has been accelerated as part of global efforts to reduce CO₂ emissions. Furthermore, previous studies have reported that cyclic heating–cooling treatments accelerate the hardening of gasoline deposits. In this study, the effects of light components, such as ethanol, and heavy components associated with synthetic fuels on deposit formation under heating–cooling cycles are investigated.

Study on Modeling of Combustion Chamber Deposits in High-Efficiency Gasoline Spark-Ignition Engines (Third report)
-Sensitivity Evaluation of Carbon-Neutral Fuel Components on Deposit Formation Using a Visualized Constant-Volume Vessel-

Kazuma Motohashi･Kotaro Tanaka･Satoshi Sakaida (Ibaraki University)･Koichi Kinoshita･Yohko Abe (AIST)･Shinsuke Mori･Satoshi Kodama (Institute of Science Tokyo)

To reduce carbon dioxide emissions, the use of carbon-neutral (CN) fuels has been extensively considered; however, deposit formation remains a significant concern. This study aims to develop a predictive model for combustion chamber deposit formation. In this report, a visualization constant-volume vessel simulating a combustion chamber was employed to clarify the effects of CN fuel components on deposit formation.

Study on Modeling of Combustion Chamber Deposits in High-efficiency Gasoline Spark-Ignition Engines (Fourth Report)
-Evaluation of Deposit Formation under Carbon-Neutral Fuel Conditions Using an Autoclave-

Koichi Kinoshita･Yohko Abe (AIST)･Kotaro Tanaka･Satoshi Sakaida (Ibaraki University)･Shinsuke Mori･Satoshi Kodama (Institute of Science Tokyo)

In recent years, carbon-neutral fuels, such as synthetic fuels, have been considered as alternatives to fossil fuels; however, deposit formation associated with their use remains a concern. This study aims to clarify the formation mechanisms of combustion chamber deposits, establish suppression methods, and develop predictive models. In this report, deposit formation experiments were conducted using an autoclave under conditions simulating carbon-neutral fuels, and the formation behavior and characteristics of the resulting deposits were evaluated.

Study on Modeling of Combustion Chamber Deposits in High-efficiency Gasoline Spark-Ignition Engines (Fifth Report)
-Development of a Predictive Model for Deposit Growth Rates in Carbon-Neutral Fuels Integrating Engine Data and Laboratory Simulations-

Shinsuke Mori･Satoshi Kodama (Institute of Science Tokyo)･Koichi Kinoshita･Yohko Abe (AIST)･Kotaro Tanaka･Satoshi Sakaida (Ibaraki University)

In recent years, improving the efficiency of internal combustion engines and utilizing carbon-neutral fuels have become increasingly important. Meanwhile, deposits formed and accumulated in combustion chambers are a concern because they can induce abnormal combustion phenomena. Therefore, this study aimed to develop a predictive model for combustion chamber deposit growth rates in carbon-neutral fuels. In this report, simulated deposit formation experiments were utilized to investigate the effects of fuel composition on deposit growth characteristics. Furthermore, model development incorporating data obtained from actual engine tests was also examined.

Development of ammonia/hydrogen SI engine
-Initial Performance and Effects of Ignition Energy in Ammonia/Hydrogen PFI Engine-

Ryo Murakami (Daihatsu Motor)

This presentation is a follow-up report to the 2026 JSAE Annual Congress Spring. A co-firing engine supplying ammonia and hydrogen with PFI was developed, and the engine performance and the hydrogen addition ratio required for stable combustion were verified using the actual engine. In addition, the effects of the spark plug gap and ignition energy on combustion at the starting operating point were evaluated, and the results are reported in this presentation.

Research on the Effect of Hydrogen Mixing on Knocking in Spark-Ignition Natural Gas Engines

Wataru Nishio･Taketoshi Shimizu (Waseda University)･Kei Yoshimura･Satoshi Tokuhara (Suzuki Motor)･Jin Kusaka (Waseda University)

The effects of hydrogen addition on knocking characteristics in a spark-ignition engine fueled with HCNG were investigated through experiments and numerical analysis. The results showed that hydrogen enrichment increases knocking intensity, while its effect on knock onset timing is limited. To investigate the underlying mechanism, reaction pathway analysis was conducted. The analysis indicates that enhanced oxidation reactions during autoignition via the HO₂/H₂O₂ reaction system are primarily responsible for the increased knocking intensity.