Effects of Differential Pressure Measurement Characteristics on Low Pressure-EGR Estimation Error in Si-Engines * *Financial support was provided by the University of Michigan and Ford Alliance.

With proper control, exhaust gas recirculation (EGR) can be used for knock mitigation in SI engines, enabling fuel economy improvements through more optimal combustion phasing and lower fuel-enrichment at high loads. Due to significant pressure pulsations across the EGR valve, estimating the mass flow rates at transient and reversing flows across the valve can be challenging. Many systems utilize the pressure drop across a restriction in a flow path as an indication of mass flow. In automotive applications, the measurement of the pressure drop is accomplished by the use of a delta pressure sensor and the pressure drop mechanism could be a sharp edge orifice or other restrictions such as a valve opening. This technique works well for steady-state flow; however, if pressure fluctuations exist, especially at higher frequencies, this method of measuring mass flow can have large errors. The accuracy of EGR mass flow estimation based on a pressure differential (Δ P) measurement and the steady compressible flow orifice equation is investigated for various Δ P sensor frequencies and sampling rates on Ford 3.5L V6 GTDI and 2.3L I4 GTDI engines. This paper identifies the two major contributors of the error are the long length of the gauge lines and the close location of the downstream tap. The long length of the gauge line results in resonances at low frequency which affects the sensor performance. When the downstream tap is placed too close to the orifice, the accuracy of sensor reading is reduced. The proposed solution suggests keeping the gauge line as short as possible and the downstream tap at least two diameters away from the orifice and using a high-speed sensor. The result from engine testing shows a great improvement in the measurement accuracy by 43%. It is demonstrated that using a slow responding sensor with a low sample rate leads to erroneous mass flow calculation when significant pressure pulsations exist. A minimum of 1 kHz sample rate is needed to increase the accuracy of the EGR estimate within ±1%.

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“…As shown in Kiwan et al 9 and repeated here for completeness, for incompressible flow, this leads to…”

Section: Effect Of Inertia On Mass Flow Errormentioning

confidence: 55%

Effects of differential pressure measurement characteristics on high pressure-EGR estimation error in SI-engines

Dadam

Ali

Zhu

et al. 2021

International Journal of Engine Research

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“…The unsteady flow equation used in the developed model was derived by integrating Navier-Stokes equation with the displacement in the flow direction, x . The integration was performed under the assumption that the flow velocity was zero at upstream of the valve and the dependency of the flow rate and pressure on x was neglected, because this equation was used to calculate mass flow through an EGR valve which was less than 10 g/s shown in Kiwan et al 35 One of the reasons for the underestimation of the mass flow through the intake valve is that these assumptions does not hold true with the high flow rate. It is suggested that another unsteady flow equation for high flow rate should be derived under an appropriate assumption.…”

Section: Resultsmentioning

confidence: 99%

“…The value of m IVO was needed to calculate Dm IVOÀEVO2 . When IVO was closer to SPR than EVO2, (34) was used, and when it was closer to EVO2, (35) was used.…”

Section: Blowdown Process (Evo;eob) When the Exhaust Valvesmentioning

confidence: 99%

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Control-oriented modeling of the gas exchange process in rebreathing homogeneous charge compression ignition engines

Takeshita

Yamasaki

Muto

et al. 2021

International Journal of Engine Research

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The purpose of this study is to develop a model for the gas exchange process in a rebreathing homogeneous charge compression ignition (HCCI) engine. HCCI engines are attracting significant attention due to their low emissions and high efficiency. To design the control system of an HCCI engine, it is necessary to develop a control-oriented engine model. The developed model lowers its computational load by combining two types of models. The model consists of a discrete model for the exhaust process (the first half of the gas exchange process) and a continuous model with a variable calculation step size for the rebreathing process (the latter half of the gas exchange process). Also, the constructed model maintained its prediction accuracy, as the pressure pulsation in the exhaust port was modeled, and an unsteady flow equation was used. It was confirmed that the model developed for the gas exchange process calculated in about half time of one cycle and reproduced the results of 1D engine simulation software with a maximum error of about 10% in the in-cylinder pressure, temperature, and trapped mass.

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“…The EGR feedback control strategy uses an estimation of the EGR quantity as an input. Nevertheless, EGR estimation is highly scattered due to part to part dispersion and sensor accuracy [3,4]. To prevent excessive EGR filling that would jeopardize combustion stability, a safety margin is added to the EGR target calibration map.…”

Section: Introductionmentioning

confidence: 99%

Combustion Stability Control Based on Cylinder Pressure for High Efficiency Gasoline Engines

2022

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Minimizing fuel consumption of passenger car vehicles can be achieved thanks to hybridization of the powertrain associated with innovative engine technologies. To feed the new high compression ratio combustion systems, air system cutting-edge technologies are used to manage air and EGR (Exhaust Gas Recirculation) quantities. Increasing EGR allows us to improve engine consumption in the high efficiency area, but it comes at the cost of a loss of stability. It is then of primary importance to be able to manage the engine near the stability limit to minimize fuel consumption. So far, the stability limit is managed in open-loop thanks to conservative calibration of the EGR quantity, implying efficiency losses. This paper addresses the combustion stability feedback control using in-cylinder pressure sensors. From this information, an indicator of stability is proposed, offering a more robust behavior in transient situations than state-of-the-art indicators. This indicator is then used to feed a controller that adapts the open-loop EGR target to go towards the stability limit. Experimental results obtained on a high efficiency gasoline engine stress the relevance of the approach in minimizing fuel consumption under real driving conditions.

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Effects of Differential Pressure Measurement Characteristics on Low Pressure-EGR Estimation Error in Si-Engines * *Financial support was provided by the University of Michigan and Ford Alliance.

Cited by 15 publications

References 9 publications

Effects of differential pressure measurement characteristics on high pressure-EGR estimation error in SI-engines

Effects of differential pressure measurement characteristics on high pressure-EGR estimation error in SI-engines

Control-oriented modeling of the gas exchange process in rebreathing homogeneous charge compression ignition engines

Combustion Stability Control Based on Cylinder Pressure for High Efficiency Gasoline Engines

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