Development and experimental validation of a real-time capable field programmable gate array–based gas exchange model for negative valve overlap

Abstract

Homogeneous charge compression ignition has the potential to significantly reduce NO x emissions, while maintaining a high fuel efficiency. Homogeneous charge compression ignition is characterized by compression-induced autoignition of a lean homogeneous air–fuel mixture. Combustion timing is highly dependent on the in-cylinder state including pressure, temperature and trapped mass. To control homogeneous charge compression ignition combustion, it is necessary to have an accurate representation of the gas exchange process. Currently, microprocessor-based engine control units require that the gas exchange process is linearized around a desired operating point to simplify the model for real-time implementation. This reduces the models’ ability to handle disturbances and limits the flexibility of the model. However, using a field programmable gate array, a detailed simulation of the physical gas exchange process can be implemented in real time. This paper outlines the process of converting physical governing equations to an offline zero-dimensional gas exchange model. The process used to convert this model to a field programmable gate array capable model is described. This model is experimentally validated using a single cylinder research engine with electromagnetic valves to record real-time field programmable gate array gas exchange results and comparing to the offline zero-dimensional physical model. The field programmable gate array model is able to accurately calculate the cylinder temperature and cylinder mass at 0.1 °CA intervals during the gas exchange process for a range of negative valve overlaps, boost conditions and engine speeds making the model useful for future real-time control applications.

Homogeneous charge compression ignition combustion stability improvement using a rapid ignition system

“…The pressure signals are simultaneously input to the FPGA board contained in the prototyping ECU. Details of the MicroAutoBox II (MABX) prototyping ECU are provided in Gordon et al 24…”

“…The heat transfer d Q w / d φ of the cylinder charge to the walls is calculated using the Hohenberg equation. 32 This real-time gas exchange model is described in detail in Gordon et al 24…”

“…Using the rapid calculation rate of the FPGA allows for the calculation of the entire gas exchange process including heat release using the existing model. 24 The gas exchange process is calculated on the FPGA every 0.1 °CA which provides the heat release rate in 3.5250 μs. 24 Therefore, the engine can be operated up to 4728 r/min before the resolution of the heat release rate cannot be maintained within 0.1 °CA.…”

“…24 The gas exchange process is calculated on the FPGA every 0.1 °CA which provides the heat release rate in 3.5250 μs. 24 Therefore, the engine can be operated up to 4728 r/min before the resolution of the heat release rate cannot be maintained within 0.1 °CA. As HCCI is a low-mid speed combustion method that is generally limited to around 3000 r/min, the proposed control strategy can be applied to the entire HCCI operating range.…”

“…Therefore, when additional controllers are implemented, it is important to determine the additional amount of resources utilized. When compared to the existing gas exchange model running on the FPGA, 24 the proposed controller consumes under 1% of the available flip-flops and look-up tables on the Xilinx FPGA used.…”