【作者】

Klaus Schmid

【摘要】

该论文已在芬兰赫尔辛基举行的第28届CIMAC大会上发表。论文的版权归CIMAC所有。Balancing the combustions of different cylinders in a multi-cylinder internal combustion engine is a task dealt with for more than 100 years now. The assumption that all cylinders provide the same torque to the crankshaft has always been a basic precondition for the mechanical design of an engine. However, in practice, different factors disturb this assumption, resulting in cylinder-to-cylinder combustion variations. Already at the early beginning of multi-cylinder engine development, operators could adjust the fuel supply to each cylinder individually, for example with throttle devices in the fuel line upstream of each cylinder. Such devices were made for adjusting an engine literally “manually”. Operators had to use their human senses to assess engine operation. There wasn’t any sensor or technical measurement providing precise information about the combustions of different cylinders. Over the years, technical progress produced many new means facilitating the balancing task: Manufacturing tolerances were reduced significantly. Powerful sensors provide detailed information to electronic control systems. Actuators for both, liquid and gaseous fuels provide interfaces to electronic controllers, allowing for fast and precise closed loop control of cylinder individual fuel supply. As a result, balancing combustion can now be “simply” done by adding some software functions to an electronic engine control system. Nonetheless, balancing combustion is still becoming a more and more challenging task. The main reason for this is that modern engines are extremely sensitive to the aforementioned cylinder-to-cylinder variations. Even very small variations between two cylinders may result in strong deviations of their combustion behavior. This paper presents solutions to some of the main tasks in integrating balancing functions to controller software. The big challenge with these balancing functions is to handle their complexity. Complexity emerges from several issues: The mere number of actuators and sensors to choose from, the difficulty to find out the “right” balancing for a specific engine, the interdependencies between more than one balancing function, the interdependencies between balancing and further standard control functions and last but not least the problem that a well-balanced engine might seem to be running well, even though severe engine problems might be the reasons for its imbalance and should be repaired as soon as possible. The first point is the mere number of actuators and sensors resulting in a large number of possible balancing solutions. In case of typical gas and dual fuel engines, on the actuator side we can choose from spark plug timing, port injection gas valve, main Diesel fuel injector and pilot Diesel fuel injector. These actuators have effect on sensor information about structure borne sound, exhaust temperature, in-cylinder combustion temperature and in-cylinder combustion pressure. There is no general answer on the question which actuator and which sensor to choose for balancing. And usually, balancing the direct sensor information is only a first step to improve engine performance. For example, regarding pure exhaust temperatures, balancing is very simple. However, it is not really the task to balance exhaust temperatures. It is far more important to balance “combustion”. Therefore, the most important step in designing a combustion balancer is to find out the right control variable, which might be a combination of sensor information from different sensors. The paper emphasizes on this cylinder individual combustion control. It presents how to combine combustion balancing with conventional control functions. Especially, a new approach to anti-knock governing is presented. It is integrated into the combustion balancing, which enables the engine control system to avoid knocking combustion – instead of only reacting to knocking combustion.

【会议名称】

第28届CIMAC会议

【会议地点】

芬兰 赫尔辛基

【下载次数】

3

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