Hardening mechanism of gasoline deposits
-Viscoelastic behavior of deposits under thermal cycling conditions-

Yoshinori Nakayama･Takumi Suzawa (SOKEN)･Tomoharu Kataoka (Toyota Moter Corporation)

It has been demonstrated that gasoline deposits, which were previously believed to harden only at temperatures above 110°C, gradually harden even at 100°C when subjected to repeated heating. Furthermore, the viscoelastic behavior of these deposits indicates that they exhibit thermoplastic properties. Additionally, the mechanism by which these deposits harden through repeated heating has been examined.

Study on Modeling of Combustion Chamber Deposits in High-Efficiency Gasoline Spark-Ignition Engines (First report)
-Accelerated Formation of Combustion Chamber Deposits Using a Spark-ignition Engine-

Kazuma Motohashi･Takumi Nakajima･Kento Okusa･Satoshi Sakaida･Kotaro Tanaka･Mitsuru Konno (Ibaraki University)･Koichi Kinoshita･Yohko Abe (AIST)･Satoshi Kodama･Shinsuke Mori (Institute of Science Tokyo)

With the introduction of high-efficiency combustion technologies, unexpected formation of combustion chamber deposits (CCDs) has led to issues such as abnormal combustion due to increased compression ratio and deterioration in emissions. To develop a predictive model for CCD formation, accelerated deposit formation experiments were conducted using a spark ignition engine. Through these experiments, the formation process of combustion chamber deposits was elucidated.

Study on modeling of combustion chamber deposits in high-efficiency gasoline spark-ignition engines （Second report）
-Elucidation of the formation mechanism of combustion chamber deposits using an autoclave-

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

To improve thermal efficiency and reduce CO₂ emissions in passenger vehicles, a range of advanced combustion and fuel technologies are being investigated. However, the formation of combustion chamber deposits (CCDs) remains a critical challenge, as it can lead to engine knocking and other negative engine performance. This study aims to clarify the mechanisms underlying CCDs formation, establish effective suppression methods, and construct a predictive model. To this end, experimental analysis was conducted using both simulated deposits and samples obtained from actual engines, allowing for the identification of key contributing factors to deposit formation.