Optimal Use of Boosting Configurations and Valve Strategies for High Load HCCI - A Modeling Study

Mamalis, Sotirios; Babajimopoulos, Aristotelis; Güralp, Orgun; Najt, Paul

doi:10.4271/2012-01-1101

Cited by 23 publications

(17 citation statements)

References 24 publications

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“…Intake manifold boosting is required to increase operating load, as is illustrated in Figure 3. The sharp increase in manifold pressure, up to 190 kPaa at 600 and 650 kPa IMEP net , is consistent with results obtained is previous studies [12,13,14]. This illustrates one of the major challenges with implementation of HCCI combustion on a production-intent platform: it is not trivial to achieve these levels of boost pressure at relatively low engine flow rate and low exhaust temperature, especially with turbo-machinery that must also perform well at high engine load conditions.…”

Section: Figure 3 Manifold Pressure As a Function Of Engine Loadsupporting

confidence: 91%

“…The first is using a hybrid mode of combustion in which a portion of the fuel energy is consumed by a propagating flame front initiated by a spark, with the remainder of the fuel energy being consumed by a volumetric HCCI-like combustion event, known both as spark-assisted HCCI (SA-HCCI) and spark-assisted compression ignition (SACI) [7,8,9,10,11]. The second is to implement a boosted air handling system so that the required dilution for HCCI can be maintained as the engine load is increased [12,13,14,15,16,17]. This study focuses on the latter strategy of load range expansion, specifically with the use of DI fueling and a NVO valve train strategy used to control combustion phasing and noise.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of Engine Control Authority on HCCI Combustion as the High Load Limit is Approached

Szybist

Edwards

Foster

et al. 2013

SAE Int. J. Engines

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In this study the authority of the available engine controls are characterized as the high load limit of homogeneous charge compression ignition (HCCI) combustion is approached. A boosted single-cylinder research engine is used and is equipped with direct injection (DI) fueling, a laboratory air handling system, and a hydraulic valve actuation (HVA) valve train to enable negative valve overlap (NVO) breathing. Results presented include engine loads from 350 to 650 kPa IMEP net and manifold pressure from 98 to 190 kPaa. It is found that in order to increase engine load to 650 kPa IMEP net , it is necessary to increase manifold pressure and external EGR while reducing the NVO duration. While both are effective at controlling combustion phasing, NVO duration is found to be a "coarse" control while fuel injection timing is a "fine" control. NO X emissions are low throughout the study, with emissions below 0.1 g/kW-h at all boosted HCCI conditions, while good combustion efficiency is maintained (>96.5%). Net indicated thermal efficiency increases with load up to 600 kPa IMEP net , where a peak efficiency of 41% is achieved. Parametric investigations reveal that increasing exhaust gas recirculation (EGR) at a constant intake manifold pressure (MAP) and increasing MAP at a constant external EGR rate both retard combustion phasing. It is also found that combustion phasing becomes increasingly sensitive to NVO duration as engine load increases. Finally, comparisons are made between commonly used noise metrics. It is found that compared to the AVL combustion noise meter, ringing intensity (RI) significantly underestimates combustion noise under boosted HCCI conditions. CITATION: Szybist, J., Edwards, K., Foster, M., Confer, K. et al., "Characterization of Engine Control Authority on HCCI Combustion as the High Load Limit is Approached," SAE Int. J. Engines 6(1):2013,

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Section: Figure 3 Manifold Pressure As a Function Of Engine Loadsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Characterization of Engine Control Authority on HCCI Combustion as the High Load Limit is Approached

Szybist

Edwards

Foster

et al. 2013

SAE Int. J. Engines

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“…HCCI requires higher unburned gas temperatures than conventional spark-ignited (SI) operation [5], since combustion is initiated through chemical kinetics rather than through spark discharge. To achieve the required temperature for auto-ignition, HCCI engines typically employ an increased compression ratio, along with a means for controlling the sensible internal energy of the charge at intake valve closing (IVC), either through the retention of hot residual combustion products, or through the external heating of the incoming charge (intake air heaters [6], bypassing the intercooler [7]), or through a combination of these methods.…”

Section: Introductionmentioning

confidence: 99%

The effects of thermal and compositional stratification on the ignition and duration of homogeneous charge compression ignition combustion

Kodavasal

Lavoie

Assanis

et al. 2015

Combustion and Flame

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The effects of thermal and compositional stratification on the ignition and duration of homogeneous charge compression ignition combustion In this work, the effects of thermal and compositional stratification on the ignition and burn duration of homogeneous charge compression ignition (HCCI) combustion are studied with full-cycle 3D computational fluid dynamics (CFD) simulations with gasoline chemical kinetics performed during the closed portion of the cycle, from intake valve closing (IVC). The stratification was varied through the use of negative valve overlap (NVO) and positive valve overlap (PVO) breathing strategies. To remove charge energy and phasing effects from the simulation results, the fuel mass and ignition timing were held constant, while mean composition effects were isolated from those of local stratification by maintaining the same mean oxygen concentration, fuel-oxygen equivalence ratio and charge heat capacity. Fuel was premixed with the intake to avoid potential stratification effects arising from direct injection. With NVO, the incomplete mixing of the fresh charge with the large mass fraction of product gases retained within the cylinder from the previous combustion cycle leads to a 23% increase in the preignition thermal stratification, and an order of magnitude increase in the levels of stratifications in fuel to oxygen equivalence ratio and oxygen mole fraction relative to the PVO strategy, which employs a premixed mixture of fresh and product gases. Under the conditions studied, the use of NVO resulted in a 30% increase in the 10-90% burn duration (CA10-90) compared to the PVO condition. Two additional analyses were performed to decouple the effects of thermal and compositional stratification. The first examined the reaction space (based on the ignition delay distribution within the charge prior to ignition) for both breathing strategies to quantify the inherent reactivity stratification. The second examined the more stratified NVO case with a quasidimensional multi-zone model. These analyses revealed that under the conditions studied, HCCI reactivity and combustion duration are governed primarily by thermal stratification and are largely insensitive to compositional stratification at the time of ignition.

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“…Mamalis et al 1,8 have presented detailed literature reviews in previous publications regarding VVA and boosting for HCCI engines. Some key findings will be summarized here for completeness.…”

Section: Vva and Boostingmentioning

confidence: 98%

The interaction between compression ratio, boosting and variable valve actuation for high load homogeneous charge compression ignition: A modeling study

Mamalis

Babajimopoulos

Güralp

et al. 2014

International Journal of Engine Research

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This study discusses a novel approach toward homogeneous charge compression ignition operation in the 5 -10 bar net indicated mean effective pressure range. This approach is based on the combination of boosting and variable valve actuation to maximize engine efficiency. Compression ratio plays a key role and determines low-temperature combustion feasibility in modern gasoline compression ignition concepts. In order to explore the interactions between compression ratio, boosting system and variable valve actuation, multi-cylinder engine models were utilized which employed the University of Michigan combustion model. Valve strategies featured switching from low-lift negative valve overlap to high-lift positive valve overlap, and the switching point was found to be dependent on compression ratio. A recent study by the authors suggested that heating the charge from external compression is more efficient than heating by residual gas retention strategies. Use of non-cooled intake air allows for valve events and combustion phasing that promote turbocharger performance and alleviate the backpressure problems often associated with low temperature combustion engines. Elevated intake pressure and reduced pumping work allow for improvements in efficiency with minimal NOx formation and acceptable ringing. It was found that further efficiency benefits can be realized by increasing compression ratio. Identification of trade-offs between engine hardware and combustion mode appears to be critical for homogeneous charge compression ignition operation in the 5 -10 bar net indicated mean effective pressure range. By focusing on this operating range, the present modeling study attempts to shed some light on practical applications of light-duty gasoline compression ignition concepts.

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Optimal Use of Boosting Configurations and Valve Strategies for High Load HCCI - A Modeling Study

Cited by 23 publications

References 24 publications

Characterization of Engine Control Authority on HCCI Combustion as the High Load Limit is Approached

Characterization of Engine Control Authority on HCCI Combustion as the High Load Limit is Approached

The effects of thermal and compositional stratification on the ignition and duration of homogeneous charge compression ignition combustion

The interaction between compression ratio, boosting and variable valve actuation for high load homogeneous charge compression ignition: A modeling study

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