Abstract
Abstract. Our approach of a closed-loop combustion control is built on an intensively evaluated robust cylinder pressure sensor with integrated smart electronics and an openly programmed engine control unit. The presented pressure sensor consists of a steel membrane and a highly strain-sensitive thin film with laser-welded electrical contacts. All components are optimized for reliable operation at high temperatures. The sensor setup safely converts the in-cylinder pressure of a combustion engine at temperatures of up to 200 ∘C into the desired electrical values. Furthermore, the embedded smart electronics provides a fast analogue to digital conversion and subsequently computes significant combustion parameters in real time, based on implemented thermodynamic equations, namely the 50 % mass fraction burned, the indicated mean effective pressure, the maximum pressure and a digital value, which represents the intensity of knocking. Only these aggregated parameters – not the running pressure values – are sent to the engine control unit. The data communication between the smart sensor and the engine control unit is based on the controller area network bus system, which is widely spread in the automotive industry and allows a robust data transfer minimizing electrical interferences. The established closed-loop combustion control is able to control the ignition angle in accordance with the 50 % mass fraction burned at a certain crankshaft angle. With this loop, the combustion engine is controlled and run efficiently even if the ignition angle is intentionally incorrectly adjusted. The controlled and automatic correction of simulated ageing effects is demonstrated as well as the self-adjustment of an efficient operation when different fuels are used. In addition, our approach saves the computing capacity of the engine control unit by outsourcing the data processing to the sensor system.
Highlights
Global emission limits for atmospheric pollutants are becoming increasingly strict due to the necessary change towards more climate and nature protection
The embedded smart electronics provides a fast analogue to digital conversion and subsequently computes significant combustion parameters in real time, based on implemented thermodynamic equations, namely the 50 % mass fraction burned, the indicated mean effective pressure, the maximum pressure and a digital value, which represents the intensity of knocking
The data communication between the smart sensor and the engine control unit is based on the controller area network bus system, which is widely spread in the automotive industry and allows a robust data transfer minimizing electrical interferences
Summary
Global emission limits for atmospheric pollutants are becoming increasingly strict due to the necessary change towards more climate and nature protection. The work presented is based on the most advantageous pressure sensor concept, which is extended by a sensor-related electronics which calculates some aggregated and meaningful combustion parameters from each pressure signal and forwards only these values to the engine control unit. The ignition timing is used to balance the MFB50 at a crankshaft angle of 8◦ Such a closed-loop combustion control results in increased engine performance as well as fuel savings and the associated reduction in carbon dioxide. Thermal shocks can affect the sensor signal during each combustion cycle to such an extent that a large measurement error occurs To minimize this source of error, a flame or heat shield can be placed in front of the sensing element, resulting in a more complex sensor design and higher production costs (Borgers et al, 2013). The pressure signal is processed on-site and condensed to meaningful combustion parameters that are forwarded to the engine control unit
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