Suzuki Takashi

Recently, ammonia (NH3), which has a higher energy density than hydrogen, has gained attention for zero-carbon emission goals in the transportation sector. However, in a conventional internal combustion engine (ICE), NH3 combustion mechanism is still under investigation. In this paper, to further expand the knowledge on the adoption of NH3 in ICEs, authors conducted NH3/gasoline co-combustion experiments in a modified, 17.7:1 compression ratio, naturally aspirated spark-assisted CI engine with sub-chamber. The sub-chamber was chosen in order to enhance the combustion speed of NH3. In addition, the sub-chamber was equipped with glow and spark plugs to overcome the high auto-ignition temperature of NH3. Engine performance and NOX emissions were studied under three different intake air temperatures. During the experiments, NH3 content was increased gradually where the engine was run under lean conditions. Although higher NH3 content was achieved compared to our previous work, increasing the intake air temperature resulted in decreased charging efficiency. In addition, corrosion was found on the piston ring after 120 h of operation, negatively affecting the engine performance. Furthermore, NH3/gasoline co-combustion duration was shortened drastically with the influence of the sub-chamber, where the longest combustion duration under the present conditions was found to be 17°CA.

In the conventional map control, the number of calibration becomes large to make the map for transient driving conditions, which leads to extend the development period and increase the development cost. To overcome these shortcomings, the development of the model-based control is required. The previous model-based feedforward (FF) controller for diesel engines used several empirical equations based on experiments to predict the polytropic index for the compression stroke considering heat losses. To reduce the number of experiments, the authors developed the physical model for predicting the polytropic index (referred to as the present model) and implemented on the above FF controller. Under the transient driving conditions, it was found that the FF controller with the present model could predict the polytropic index with an average error of 0.31% and the indicated mean effective pressure (IMEP) with the maximum difference of 6.4 kPa, which shows that the present model can be used in place of the empirical equation.

For improvement of thermal efficiency of diesel engines, it is effective to control the fuel injection timing and quantity by using the model-based control (MBC) on ECU (on-board) with cycle-by-cycle calculation. The authors previouslydeveloped an on-board in-cylinder wall temperature prediction model and wall heat transfer prediction model those area part of models for MBC. The present study measured the time evolution of local wall temperature and heat flux in thecombustion chamber to evaluate the models. As a result of the wall temperature prediction model, it was made clear thatthe maximum error was 1.3% at the liner. About the wall heat transfer prediction model, it was shown that the maximumerror of heat flux was 5.8% at liner except for the inner head, and the average error of heat flux was -5.8% at the innerhead except for the cavity side wall.

A new equation, which was dependent on physical principles, was developed for the study of heat transfer in CI engines which needs turbulence of gas flows to calculate heat flux. Proposed approach was implemented into a 1-D engine simulation, which was used to determine heat flux between in-cylinder gas and wall. Results from the suggested equation were compared to the previous conventional equations; Morel and Hohenberg, and to the engine experiments. The proposed equation showed better accuracy when compared with the conventional equations due to detailed representation of in-cylinder gas flow by dividing the combustion chamber into 6 different regions.

The diesel engines are superior in terms of power efficiency and fuel economy compared to gasoline engines. In order to optimize the performance of direct injection diesel engine, the effect of various intake pressure (boost pressure) from supercharging direct injection diesel engine was studied at various engine rotation. A single cylinder direct injection diesel engine was used in this experiment. The bore diameter of the engine used was set to 85 mm, the stroke length was set to 96.9 mm, and the compression ratio was set to 16.3. The variation of engine rotation started from 800 rpm to 2 000 rpm with 400 rpm increment. The variation of boost pressure is bounded from 0 kPa boost pressure (naturally aspirated) to the maximum of 60 kPa boost pressure with 20 kPa boost pressure increment. The performance of the engine is evaluated in terms of in-cylinder pressure and heat release rate as the most important performance characteristics of the diesel engine. The in-cylinder pressure and heat release rate of direct injection diesel engine are increased with the elevation of boost pressure at various engine rotation. The raise of engine rotation resulted in the decrease of maximum in-cylinder pressure and heat release rate.

本稿ではMAP作成の手間を自動化し, かつ環境変化に対するロバスト性を有する制御系設計法として, フィードバック誤差学習を用いたモデルベースト制御を提案する. また, 制御器の学習機構として小脳演算モデルコントローラを用いることで計算負荷を低減することができる. そして, 本手法の有効性を実機試験にて検証する.

Overall efficiency of internal combustion engines are heavily depended on intake air temperature which is directly related to the heat transfer inside an intake system. Previously, authors developed an equation by using port model setup to calculate Nusselt number with introduction of Graetz and Strouhal numbers. This study modified the port model equation to improve its accuracy in a real engine experimental setup. Predicted intake air temperature was compared to the measured data with a maximum error of 5.6%. Additionally, 100 K of temperature difference was found between the boost pressure values of 944hPa and 678hPa from 1-D engine simulation results.