Development of Valve Train Configurations Optimized for Cold Start and Their Effect on Diesel Soot Emission

Maniatis, Panagiotis; Erforth, Daniel; Wagner, Uwe; Koch, Thomas

doi:10.4271/2019-24-0161

Cited by 3 publications

(3 citation statements)

References 14 publications

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“…By assumption, all of these models are completely defined by x bdc , u, and air path states. Since an early IVC causes a drop in T bdc as shown in equation (23), the effect of a reduced compression ratio is captured in x bdc . A distinction has to be made for two different types of Miller cycles mentioned in literature.…”

Section: Miller Cyclementioning

confidence: 99%

“…Most of the strategies mentioned increase the engineout enthalpy at the expense of increased fuel consumption. 3,6,7,[17][18][19][20][21][22][23] Alternatively, various cylinder deactivation strategies can also be used to increase exhaust enthalpy. 7,8,[24][25][26][27][28] In comparison to the valve timing strategies mentioned, cylinder deactivation results in a higher engine-out temperature, but it also lowers engine mass flow and is therefore better suited for stay-warm operation.…”

Section: Introductionmentioning

confidence: 99%

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A method to quantify the advantages of a variable valve train for CI engines

Moretto,

Hänggi,

Omanovic

et al. 2023

International Journal of Engine Research

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Today’s CI engines are subject to strict regulations of pollutant emissions and ambitious fuel consumption targets. Therefore, the interaction between the engine and the exhaust aftertreatment system (ATS) has become increasingly important. Numerous studies have shown that a variable valve train (VVT) improves the interaction between engine and ATS. However, most of these studies either quantify the advantage on a specific engine or only present complex CFD models, such that the results are not easily transferable to different engines. Thus, engine manufacturers cannot directly use these results to assess the advantage of various VVT strategies for their engines. In this paper, we propose a cycle-discrete cylinder model based on first principles which allows to simulate various VVT strategies. In contrast to present methods based on CFD, the proposed cylinder model can be realized with the equations presented. Furthermore, the model is identified with measurement data of an engine without a VVT. A separate engine, which is retrofitted with a fully VVT, is used to validate the proposed modeling approach. Using the identified model in combination with a mean-value model of the air path, we are able to simulate the effects of early intake valve closing, early exhaust valve opening, and cylinder deactivation for a complete CI engine that has no VVT installed. The model is then used to highlight the advantage of a VVT for two scenarios at part-load operation. At cold start, where the temperature of the ATS must be increased quickly, variable valve timing achieves higher enthalpy flows to the ATS while also lowering engine-out NOx emissions when compared to a standard engine strategy. If the ATS is at the operating temperature, cylinder deactivation achieves significantly higher enthalpy flows which prevents the ATS from cooling down. In addition, cylinder deactivation also lowers fuel consumption and engine-out NOx emissions.

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Section: Miller Cyclementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A method to quantify the advantages of a variable valve train for CI engines

Moretto,

Hänggi,

Omanovic

et al. 2023

International Journal of Engine Research

View full text Add to dashboard Cite

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“…11–13 Exhaust valve modulation to reintroduce residual gas was shown to improve cold start emissions, which along with delayed injections assisted with increase in engine-out exhaust temperatures. 14,15…”

Section: Introductionmentioning

confidence: 99%

Exhaust valve profile modulation for improved diesel engine curb idle aftertreatment thermal management

Joshi

Gosala

Shaver

et al. 2021

International Journal of Engine Research

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Rapid warm-up of a diesel engine aftertreatment system (ATS) is a challenge at low loads. Modulating exhaust manifold pressure (EMP) to increase engine pumping work, fuel consumption, and as a result, engine-outlet temperature, is a commonly used technique for ATS thermal management at low loads. This paper introduces exhaust valve profile modulation as a technique to increase engine-outlet temperature for ATS thermal management, without requiring modulation of exhaust manifold pressure. Experimental steady state results at 800 RPM/1.3 bar BMEP (curb idle) demonstrate that early exhaust valve opening with negative valve overlap (EEVO+NVO) can achieve engine-outlet temperature in excess of 255°C with 5.7% lower fuel consumption, 12% lower engine out NOx and 20% lower engine-out soot than the conventional thermal management strategy. Late exhaust valve opening with internal EGR via reinduction (LEVO+Reinduction) resulted in engine-outlet temperature in excess of 280°C, while meeting emission constraints at no fuel consumption penalty. This work also demonstrates that LEVO in conjunction with modulation of exhaust manifold pressure results in engine-outlet temperature in excess of 340°C while satisfying desired emission constraints. Aggressive use of LEVO can result in engine-outlet temperatures of 460°C, capable of active regeneration of DPF at curb idle, without the significant increase in engine-out soot emissions seen in previously studied strategies.

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