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  • 1
    Online Resource
    Online Resource
    A physics-based approach to the control of homogeneous charge compression ignition engines with variable valve actuation
    SAGE Publications ; 2005
    In:  International Journal of Engine Research Vol. 6, No. 4 ( 2005-08-01), p. 361-375
    Details
    In: International Journal of Engine Research, SAGE Publications, Vol. 6, No. 4 ( 2005-08-01), p. 361-375
    Abstract: Homogeneous charge compression ignition (HCCI) is a promising low-temperature combustion strategy for reducing NO x emissions and increasing efficiency in internal combustion engines. However, HCCI has no direct combustion initiator and, when achieved by reinducting or trapping residual exhaust gas with a variable valve actuation (VVA) system, becomes a dynamic process as the temperature of the residual gas couples one cycle to the next. These characteristics of residual-affected HCCI present a challenge for control engineers and a barrier to implementing HCCI in a production engine. In order to address these challenges, this paper outlines physics-based control strategies for both the VVA system and the HCCI combustion process. The results show that VVA system control can provide arbitrary valve timings on a cycle-to-cycle basis, enabling tight control of HCCI. By abstracting these valve timings further into an inducted gas composition and an effective compression ratio, model-based controllers can be developed to control simultaneously load and combustion timing in an HCCI engine.
    Type of Medium: Online Resource
    ISSN: 1468-0874 , 2041-3149
    URL: Article
    DOI: 10.1243/146808705X30512
    RVK:
    ZG 1100
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2005
    detail.hit.zdb_id: 2030603-9
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  • 2
    Online Resource
    Online Resource
    Numerical and experimental investigation of a compressor with active self-recirculation casing treatment for a wide operation range
    SAGE Publications ; 2013
    In:  Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering Vol. 227, No. 9 ( 2013-09), p. 1227-1241
    Details
    In: Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, SAGE Publications, Vol. 227, No. 9 ( 2013-09), p. 1227-1241
    Abstract: A turbocharger compressor with a wide flow range and a high efficiency is important to the application of advanced clean combustion technologies, such as homogeneous charge compression ignition and low-temperature combustion, in diesel engines. Self-recirculation casing treatment is one of the techniques that can extend the compressor surge margin without much efficiency penalty. The underlying physics of the self-recirculation casing treatment technology were investigated with computational fluid dyamics modeling and bench testing in this study. It is identified that, if the bleed slot of the self-recirculation casing treatment is located upstream of the impeller passage’s throat area, self-recirculation casing treatment improves the surge margin but the throat still limits the maximum flow capacity of the compressor. On the other hand, if the bleed slot of the self-recirculation casing treatment is located at the impeller passage’s throat area, the self-recirculation casing treatment improves the maximum flow capacity but results in a significant compressor efficiency penalty in the low-flow range. An active self-recirculation casing treatment design was proposed. The active self-recirculation casing treatment design extends the compressor flow capacity and improves the surge margin without an efficiency penalty through dual bleed slots with one upstream and the other downstream of the leading edge of the splitter blades. In the choke condition, the upstream bleed slot will be closed; near the surge condition, the downstream bleed slot will be closed. In the middle flow range, both bleed slots are closed. Both the numerical data and the bench testing results show that the maximum flow rate could be extended by about 15% and the surge margin by about 20% without an efficiency penalty. The mechanism of the performance improvement is also numerically studied.
    Type of Medium: Online Resource
    ISSN: 0954-4070 , 2041-2991
    URL: Article
    DOI: 10.1177/0954407013486741
    RVK:
    ZO 4200
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2013
    detail.hit.zdb_id: 2032754-7
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  • 3
    Online Resource
    Online Resource
    Computational analysis of end-of-injection transients and combustion recession
    SAGE Publications ; 2017
    In:  International Journal of Engine Research Vol. 18, No. 10 ( 2017-12), p. 1088-1110
    Details
    In: International Journal of Engine Research, SAGE Publications, Vol. 18, No. 10 ( 2017-12), p. 1088-1110
    Abstract: Mixing and combustion of engine combustion network Spray A after end of injection are modeled using highly resolved multidimensional numerical simulations to explore the physics underlying recent experimental observations of combustion recession. Reacting spray simulations are performed using a traditional Lagrangian–Eulerian coupled formulation for two-phase mixture transport with a Reynolds-averaged Navier–Stokes approach using the open-source computational fluid dynamics code OpenFOAM. Chemical kinetics models for n-dodecane by Cai et al. and Yao et al. are deployed to evaluate the impact of mechanism formulation and low-temperature chemistry on predictions of combustion recession behavior. Simulations with the Cai mechanism show that under standard Spray A conditions, the end-of-injection transient induces second-stage ignition in distinct regions near the nozzle that are initially spatially separated from the lifted diffusion flame, but then rapidly merge with flame. By contrast, the Yao mechanism fails to predict sufficient low-temperature chemistry in mixtures upstream of the diffusion flame during the end-of-injection transient and does not predict combustion recession for the same conditions. The effects of the shape and duration of the end-of-injection transient on the entrainment wave near the nozzle, the likelihood of combustion recession, and the spatiotemporal development of mixing and chemistry in near-nozzle mixtures are also investigated. With a more rapid ramp-down injection profile (ramp-down duration  〈  400 µs), a weaker combustion recession occurs earlier in time after the start of ramp-down. For extremely fast ramp-down (ramp-down duration = 0), the entrainment flux varies rapidly near the nozzle and over-leaning of the mixture completely suppresses combustion recession. For a slower ramp-down profile with respect to the standard Spray A condition, complete combustion recession back toward the nozzle is observed and combustion recession occurred later in time. Simulations qualitatively agreed with the past experimental and modeling observations of combustion recession with different end-of-injection transients.
    Type of Medium: Online Resource
    ISSN: 1468-0874 , 2041-3149
    URL: Article
    DOI: 10.1177/1468087417701280
    RVK:
    ZG 1100
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2017
    detail.hit.zdb_id: 2030603-9
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  • 4
    Online Resource
    Online Resource
    Thermodynamic efficiency assessment of gasoline spark ignition and compression ignition operating strategies using a new multi-mode combustion model for engine system simulations
    SAGE Publications ; 2019
    In:  International Journal of Engine Research Vol. 20, No. 3 ( 2019-03), p. 304-326
    Details
    In: International Journal of Engine Research, SAGE Publications, Vol. 20, No. 3 ( 2019-03), p. 304-326
    Abstract: Advanced combustion strategies for gasoline engines employing highly dilute and low-temperature combustion modes, such as homogeneous charge compression ignition and spark-assisted compression ignition, promise significant improvements in efficiency and emissions. This article presents a novel, reduced-order, physics-based model to capture advanced multi-mode combustion involving spark ignition, homogeneous charge compression ignition and spark-assisted compression ignition operating strategies. The purpose of such a model, which until now was unavailable, was to enhance existing capabilities of engine system simulations and facilitate large-scale parametric studies related to these advanced combustion modes. The model assumes two distinct thermodynamic zones divided by an infinitely thin flame interface, where turbulent flame propagation is captured using a new zero-dimensional formulation of the coherent flame model, and end-gas auto-ignition is simulated using a hybrid approach employing chemical kinetics and a semi-empirical burn rate model. The integrated model was calibrated using three distinct experimental data sets for spark ignition, homogeneous charge compression ignition and spark-assisted compression ignition combustion. The results demonstrated overall good trend-wise agreement with the experimental data, including the ability to replicate heat release characteristics related to flame propagation and auto-ignition during spark-assisted compression ignition combustion. The calibrated model was assessed using a large parametric study, where the predicted homogeneous charge compression ignition and spark-assisted compression ignition operating regions at naturally aspirated conditions were representative of those determined during engine testing. Practical advanced combustion strategies were assessed relative to idealized engine simulations, which showed that efficiency improvements up to 30% compared with conventional spark-ignition operation are possible. The study revealed that poor combustion efficiency and pumping work are the primary mechanisms for efficiency losses for the advanced combustion strategies evaluated.
    Type of Medium: Online Resource
    ISSN: 1468-0874 , 2041-3149
    URL: Article
    DOI: 10.1177/1468087417752195
    RVK:
    ZG 1100
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2019
    detail.hit.zdb_id: 2030603-9
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