【作者】

Ioana Georgescu

【摘要】

该论文已在赫尔辛基举行的第28届CIMAC大会上发表，论文的版权归CIMAC所有。The importance of natural gas as a primary fuel in internal combustion engines is steadily increasing. While in the energy sector it has been considered a viable option for decades, its use in the maritime sector has been limited. Despite the recent improvements to the infrastructure available for natural gas, the reason for this is still mainly due to fuel related concerns (storage, bunkering). However, poor transient performance can disqualify gas engines for certain applications even in areas where the infrastructure is sufficiently developed. Particularly in applications with expected severe transient loading, the increasing importance placed on system integration requires studies of dynamic behaviour to be carried out by potential users of the system. The air-excess ratio in the cylinder influences efficiency and emissions through its effects on the combustion process. Furthermore, its range is severely constrained by misfire and knock. These two factors make engines running primarily on natural gas particularly sensitive to transient operations. This paper investigates the transient behaviour of engines using natural gas as primary fuel. In order to achieve this, two existing diesel engine models have been adapted to simulate the operating principle of such engines. The first model focuses on the cylinder processes and has a crank angle time scale. It is used to gain insight into the combustion process of gas and dual-fuel engines. The second model simulates the entire system and has a revolution time scale. It includes three different versions of controlling the air-excess ratio in the cylinder: waste gate, blow-off valve and variable valve timing. The simulation results show the trade-off between cost and efficiency on the one side and transient response on the other. By increasing the extent to which the air-excess control system is used, bigger load steps can be taken without the occurrence of knock or misfire. This would, however, also imply a bigger waste gate/blow-off valve and more losses, as these would be opened over a larger range. Variable valve timing could theoretically be used to eliminate this choice entirely, so it is expected that manufacturers will work on the development of this technology. The difference in performance observed between a waste gate and a blow-off valve was negligible. Much more important proved to be the sizing of the valves mentioned above and the parameters of the control system. The models developed give an initial indication to potential users whether a gas or dual-fuel engine can comply with the transient requirements for a certain application. Furthermore, the results can be used to identify changes that would increase the transient capabilities of the engine up to the desired level. This could give potential users the required confidence and might help engines running primarily on natural gas to enter previously un-accessible markets.

【会议名称】

第28届CIMAC会议

【会议地点】

芬兰 赫尔辛基

【下载次数】

2

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