Mode switches among SI, SACI, and HCCI combustion and their influence on drive cycle fuel economy

Nüesch, Sandro P.; Hellström, Erik; Jiang, Li; Stefanopoulou, Anna G.

doi:10.1109/acc.2014.6858954

Cited by 12 publications

(17 citation statements)

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“…In the following section the delays and supervisory control of combustion mode switching are incorporated into a vehicle model. In [15] a methodology is presented, modeling the combustion mode switch dynamics in form of a finite state machine. In [9] the model was parameterized with experimental mode switch data.…”

Section: Modelmentioning

confidence: 99%

Is it Economical to Ignore the Driver? A Case Study on Multimode Combustion

Nüesch

Stefanopoulou

2015

Volume 1: Adaptive and Intelligent Systems Control; Advances in Control Design Methods; Advances in Non-Linear and Optimal Cont

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Ignoring the driver's torque command can be beneficial for fuel economy, especially if it leads to extended residence time at efficient operating conditions. We answered this question for a particular engine, which allows mode switches between spark ignition (SI) and homogeneous charge compression ignition (HCCI) combustion. When operating such a multimode combustion engine it might be required to defer a load command outside the feasible regime of one combustion mode until a mode switch is accomplished. The resulting delays in engine torque response might negatively affect vehicle performance and drivability. In this paper a longitudinal vehicle model is presented, which incorporates dynamics associated with SI/HCCI mode switching. Two exemplary supervisory control strategies were evaluated in terms of fuel economy and torque behavior. It was seen that the duration of a mode switch may be short enough to avoid substantial impairment in torque response. This in turn would lead to the opportunity of purposefully ignoring the driver command. Thereby, the residence time in the beneficial HCCI combustion regime is prolonged and fuel-expensive mode switching avoided. The result is a trade-off between torque deviation and improvements in fuel economy. Finally, based on this trade-off the supervisory control strategy relying on a short-term prediction of engine load was seen to achieve similar fuel economy with slightly improved torque response than a strategy without prediction.

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Section: Modelmentioning

confidence: 99%

Is it Economical to Ignore the Driver? A Case Study on Multimode Combustion

Nüesch

Stefanopoulou

2015

Volume 1: Adaptive and Intelligent Systems Control; Advances in Control Design Methods; Advances in Non-Linear and Optimal Cont

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“…Here, the penalization is implemented by using the finite state machine introduced in Ref. [2]. In this paper the model, depicted in Fig.…”

Section: Combustion Mode Switch Modelmentioning

confidence: 99%

“…For more details, it is referred to Ref. [2]. The fuel beneficial region is denoted R(k) ʦ {SI, HCCI}.…”

Section: Combustion Mode Switch Modelmentioning

confidence: 99%

“…The operating regime of HCCI is limited to low and medium loads due to reduced combustion stability and increasing pressure rise rates, respectively. Even though during a standard drive cycle a substantial amount of time is spent within the HCCI operating regime [2] it is not possible to fulfill all the driver demands. A solution is the combination of HCCI with SI combustion in a multimode combustion approach [3].…”

Section: Introductionmentioning

confidence: 99%

“…The combustion mode switch model, shown in Ref. [2], is extended in Sec. 5 by accounting for rich SI combustion and emissions during the mode switches.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Fuel Economy of a Multimode Combustion Engine With Three-Way Catalytic Converter

Nüesch

Stefanopoulou

Jiang

et al. 2014

Journal of Dynamic Systems, Measurement, and Control

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Highly diluted, low temperature homogeneous charge compression ignition (HCCI) com-bustion leads to ultralow levels of engine-out NOx emissions. A standard drive cycle, however, would require switches between HCCI and spark-ignited (SI) combustion modes. In this paper we quantify the efficiency benefits of such a multimode combustion engine, when emission constraints are to be met with a three-way catalytic converter (TWC). The TWC needs unoccupied oxygen storage sites in order to achieve acceptable performance. The lean exhaust gas during HCCI operation, however, fills the oxygen storage and leads to a drop in NOx conversion efficiency. If levels of tailpipe NOx become unacceptable, a mode switch to a fuel rich combustion mode is necessary in order to deplete the oxygen storage and restore TWC efficiency. The resulting lean-rich cycling leads to a penalty in fuel economy. Another form of penalty originates from the lower combustion efficiency during a combustion mode switch itself. In order to evaluate the impact on fuel economy of those penalties, a finite state model for combustion mode switches is combined with a longitudinal vehicle model and a phenomenological TWC model, focused on oxygen storage. The aftertreatment model is calibrated using combus-tion mode switch experiments from lean HCCI to rich spark-assisted HCCI (SA-HCCI) and back. Fuel and emission maps acquired in steady-state experiments are used. Differ-ent depletion strategies are compared in terms of their influence on drive cycle fuel econ-omy and NOx emissions. It is shown that even an aggressive lean-rich cycling strategy will marginally satisfy the cumulated tailpipe NOx emission standards under warmed-up conditions. More notably, the cycling leads to substantial fuel penalties that negate most of HCCI’s efficiency benefits. [DOI: 10.1115/1.4028885]

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