Yilmaz Emir

Carbon dioxide (CO2) is the primary contributor to greenhouse gas emissions. Ammonia (NH3) has emerged as a promising alternative fuel due to its high energy density, ease of transportation, and carbon-free molecular structure. However, its practical application is challenged by slow combustion characteristics and high ignition temperatures. This study investigates the combustion behaviour of ethanol-ammonia mixtures using a high-compression-ratio engine (17.7:1) equipped with a sub-chamber. The engine operated at a constant speed of 1000 rpm. Ammonia energy ratios of 40%, 50%, and 60% were tested across ignition timings of 0°, 2°, 4°, 6°, and 8° crank angle (CA) before top dead center (BTDC). Results indicate that advancing the ignition timing increases in-cylinder pressure and heat release rate while reducing combustion duration. Lower ammonia energy ratios yielded higher thermal efficiency. Conversely, higher ammonia content and advanced ignition timings led to increased NOx emissions.

ディーゼル機関のモデルベースト燃焼制御器では，冷却損失を考慮した圧縮ポリトロープ指数の予測にこれまで実験式を用いてきた．著者らは，実験数を軽減するため，新たに物理モデルを開発し，制御器に実装した．実機にて過渡運転性能を評価したところ，実験値と比較して，モデルの予測誤差は0．３１％と評価された．

ディーゼル機関の過渡運転性能向上には，モデルベースト制御によるサイクル毎の燃料噴射量と時期の予測が有効である．本研究では，燃焼室の局所壁温度履歴および局所壁面熱流束履歴を測定し，著者らが構築したオンボード用筒内壁温度推定モデルおよび壁面熱伝達モデルの予測精度を評価したので報告する．

ディーゼル機関の過渡性能向上にはオンボード・モデルベースト制御による着火時期の予測が重要である．著者らは，筒内ガス温度をサイクルごとに予測するため，低計算負荷の圧縮ポリトロープ指数予測モデルを開発した．過渡運転条件に適用し，１Ｄ数値計算と比較した結果，構築したモデルの有用性が認められたので報告する．

<p> The present study conducted the derivation of the empirical equation in terms of the heat transfer phenomena at the intake manifold of internal combustion engines and the implementation of its equation to 1-D engine simulation. The derived equation allows to calculate the Nusselt number at the intake system, which causes to predict the mass flow rate of intake air into the cylinder accurately, ultimately improving the fuel consumption by controlling the auto-ignition timing. The empirical equation was developed based on the Colburn equation, taking into consideration of the effects of the thermal boundary layer development and the intermittent air flow induced by the opening and closing of intake valves. Compared with the experimental data, the average errors of the Colburn equation and the empirical equation were estimated to be 91.1% and 2.7%, which gives to improve the prediction accuracy of the Nusselt number by deriving the empirical equation. The equation was then implemented in 1-D engine simulation and compared to the results of the Colburn equation, revealing the maximum and average intake air temperature differences of 11.4 K and 2.7 K, respectively.</p>

本論文は，実機エンジンの吸気管にて温度測定を行い，吸気システムでの伝熱現象を検討した．その際，流れの非定常性および温度境界層の発達を考慮し，Nu数をRe数，Gz数，St数で表した実験式を導出した．また，熱力学モデルに基づきシリンダに吸入される空気温度を推定したところ，5.6%の誤差で推定可能であることがわかった．