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This paper presents two closed-loop control methods for monitoring and improving the combustion behavior and the combustion noise on two 4-cylinder diesel engines, in which an in-cylinder pressure and an accelerometer transducer are used to monitor and control them. Combustion processes are developed to satisfy the stricter and stricter regulations on emissions and fuel consumption. These combustion processes are influenced by the factors such as engine durability, driving conditions, environmental influences and fuel properties. Combustion noise could be increased by these factors and is detrimental to interior sound quality. Therefore, it is necessary to develop robust combustion behaviors and combustion noise. For this situation, we have developed two closed-loop control methods. Firstly, a method using in-cylinder pressure data was developed for monitoring and improving the combustion noise of a 1.7L engine. A new index using the values calculated from the data was proposed.

The combustion noise of a diesel engine can be deteriorated by combustion characteristics such as the maximum rate of heat release and the start of combustion. These combustion characteristics in turn are influenced by the factors such as the engine NVH durability, driving conditions, environmental factors and fuel properties. Therefore, we need to develop the robust combustion noise that is insensitive to these factors. To achieve this aim, methods for predicting combustion characteristics has been developed by analyzing the vibration signal measured from the engine cylinder block. The closed-loop control of injection parameters through combustion characteristics prediction has been performed to produce the desired engine combustion performance. We constructed an ECU logic for the closed-loop control and verified the design in a diesel passenger car. We also evaluated the effect of combustion noise and fuel consumption by applying the closed-loop control.

Emissions regulations are becoming more severe, and they remain a principal issue for vehicle manufacturers. Many engine subsystems and control technologies have been introduced to meet the demands of these regulations. For diesel engines, combustion control is one of the most effective approaches to reducing not only engine exhaust emissions but also cylinder-by-cylinder variation. However, the high cost of the pressure sensor and the complex engine head design for the extra equipment are stressful for the manufacturers. In this paper, a cylinder-pressure-based engine control logic is introduced for a multi-cylinder high speed direct injection (HSDI) diesel engine. The time for 50% of the mass fraction to burn (MFB50) and the IMEP are valuable for identifying combustion status. These two in-cylinder quantities are measured and applied to the engine control logic.

Homogeneous Charge Compression Ignition combustion engines could have a thermal efficiency as high as that of conventional compression-ignition engines and the production of low emissions of ultra-low oxides of NOx and PM. HCCI engines can operate on most alternative fuels, especially, dimethyl ether which has been tested as possible diesel fuel for its simultaneously reduced NOx and PM emissions. However, to adjust HCCI combustion to practical engines, the main problem about the HCCI engine must be solved; control of its ignition timing and burn rate over a range of engine speeds and loads. Detailed chemical kinetic modeling has been used to predict the combustion characteristics. But it is difficult to apply detailed chemical kinetic mechanism to simulate practical engines because of its high complexity coupled with multidimensional fluid dynamic models. Thus, reduced chemical kinetic modeling is desirable.

In an HSDI Diesel engine, fuel can be injected to the combustion chamber earlier as a strategy to reduce NOx and soot emissions. However, in the case of early injection the in-cylinder pressure and temperature during injection are much lower than those of normal injection conditions. As a result, wall impingement can occur if the conventional spray angle and piston bowl shape are maintained. In this study, 3-D CFD simulation was used to modify the spray angle of the injector and the piston bowl shape so that wall impingement was minimized, and soot emissions were reduced. The wall impingement model was used to simulate the behavior of impinged droplets. In order to predict the performance and emissions of the engine, a flamelet combustion model with the kinetic chemical mechanism for NOx and soot was used. A reduction in soot emissions was achieved with the modification of the spray angle and piston bowl shape.