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Corona ignition is a promising technology that has been demonstrated to be capable of improving the reliability of lean combustion. However, arcing is unavoidable during corona discharge. The high current surge during arcing can cause excessive damage to the corona ignition system. In this work, a control framework is proposed to help reduce and prevent arcing from happening in a corona ignition system. Experimental results are demonstrated to show the effectiveness of the proposed methodology.

Reduction of nitrogen oxides (NOx) in lean burn and diesel fueled Compression Ignition (CI) engines is one of the major challenges faced by automotive manufacturers. Lean NOx Trap (LNT) and urea-based Selective Catalytic Reduction (SCR) exhaust after-treatment systems are well established technologies to reduce NOx emissions. However, each of these technologies has associated advantages and disadvantages for use over a wide range of engine operating conditions. In order to meet future ultra-low NOx emission norms, the use of both alternative fuels and advanced after-treatment technology may be required. The use of an alcohol fuel such as n-butanol or ethanol in a CI engine can reduce the engine-out NOx and soot emissions. In CI engines using LNTs for NOx reduction, the fuel such as diesel is utilized as a reductant for LNT regeneration.

Lean burn or EGR diluted combustion with enhanced charge motion is effective in improving the efficiency of spark ignition engines. However, the ignition process under these conditions is getting more challenging due to higher ignition energy required by the lean or diluted mixture, as well as the interactions of the gas flow on the flame kernel. Enhanced spark discharge energy is essential to initiate the combustion under these conditions. Moreover, the discharge process should be more carefully controlled to improve the effectiveness of the spark. In this study, spark ignition systems with boosted discharge energy are used to ignite diluted air-fuel mixture under forced flow conditions. The impacts of the discharge current level, the discharge duration and the discharge current profile on the ignition are investigated in detail using optical diagnosis.

For internal combustion engine systems, lean and diluted combustion is an important technology applied for fuel efficiency improvement. Because of the thermodynamic boundary conditions and the presence of in-cylinder flow, the development of a well-sustained flame kernel for lean combustion is a challenging task. Reliable spark discharge with the addition of enhanced delivered energy is thus needed at certain time durations to achieve successful combustion initiation of the lean air-fuel mixture. For a conventional transistor coil ignition system, only limited amount of energy is stored in the ignition coil. Therefore, both the energy of the spark discharge and the duration of the spark discharge are bounded. To break through the energy limit of the conventional transistor coil ignition system, in this work, an adaptive spark ignition system is introduced. The system has the ability to reconstruct the conductive ion channels whenever it is interrupted during the spark discharge.

Performance of the ignition system becomes more important than ever, because of the extensively used EGR in modern spark-ignition engines. Future lean burn SI and SACI combustion modes demand even stronger ignition capability for robust ignition control. For spark-based ignition systems, extensive research has been carried out to investigate the discharge characteristics of the ignition process, including discharge current amplitude, discharge duration, spark energy, and plasma stretching. The correlation between the spark stretch and the discharge energy, as well as the impact of discharge current level on this correlation, are important with respect to both ignition performance, and ignition system design. In this paper, a constant volume combustion chamber is applied to study the impact of plasma stretch on the spark energy release process with cross-flow speed from 0 m/s up to 70 m/s.

Lean burn is regarded as one of the most effective ways to improve fuel efficiency for spark ignition engines. However, the excessive air dilution deteriorates combustion stability, limiting the degree of engine operational dilution. The intensified flow field is therefore introduced into the cylinder to mitigate the decline of the burning velocity caused by the leaned-out fuel-air mixture. In a moderate flow field, flame kernels are formed near the hot spark plasma during discharge and stick to the spark gap even after the end of discharge; the flame front then propagates outward and evolves into self-sustained flame. Flame attaching to the spark gap is a common phenomenon in the early combustion stage and has been reported to be beneficial for flame inception in the literature.

Compression ignition engines used in heavy-duty applications are typically powered by diesel fuel. The high energy density and feedstock abundance provide a continuing source for the immense energy demand. However, the heavy-duty transportation sector is challenged with lowering greenhouse gas and combustion by-product emissions, including carbon dioxide, nitrogen oxides, and particulate matter. The continuing development of engine management and combustion strategies has proven the ability to meet current regulations, particularly with higher fuel injection pressure. Nonetheless, a transition from diesel to a renewable alternative fuel source will play a significant role in reducing greenhouse gases while maintaining the convenience and energy density inherent in liquid fuels. Dimethyl ether is a versatile fuel that possesses combustion properties suitable for compression ignition engines and physical properties helpful for clean combustion.

In order to improve the fuel economy for future high-efficiency spark ignition engines, the applications of advanced combustion strategies are considered to be beneficial with an overall lean and/or exhaust gas recirculation diluted cylinder charge. Stronger and more reliable ignition sources become more favorable under extreme lean/EGR conditions. Existing research indicates that the frequency of plasma restrikes increases with increased flow velocity and decreased discharge current level, and a higher discharge current can reduce the gap resistance and maintain the stretched plasma for a longer duration under flow conditions. An in-house developed current boost control system provides flexible control of the discharge current level and discharge duration. The current boost ignition system is based on a multi-coil system with a discharge current level of 180mA.