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Najt, Paul M.
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Downsized-Boosted Gasoline Engine with Exhaust Compound and Dilute Advanced Combustion

General Motors LLC-Jeremie Dernotte, Paul M. Najt, Russell P. Durrett
  • Technical Paper
  • 2020-01-0795
To be published on 2020-04-14 by SAE International in United States
This article presents experimental results obtained with a disruptive engine platform, designed to maximize the engine efficiency through a synergetic implementation of downsizing, high compression-ratio, and importantly exhaust-heat energy recovery in conjunction with advanced lean/dilute low-temperature type combustion. The engine architecture is a supercharged high-power output, 1.1-liter engine with two-firing cylinders and a high compression ratio of 13.5: 1. The integrated exhaust heat recovery system is an additional, larger displacement, non-fueled cylinder into which the exhaust gas from the two firing cylinders is alternately transferred to be further expanded.The main goal of this work is to implement in this engine, advanced lean/dilute low-temperature combustion for low-NOx and high efficiency operation, and to address the transition between the different operating modes. Those include well-mixed charge compression-ignition at low-load, and a mixed-mode combustion at higher loads, before transitioning to boosted homogenous and stochiometric spark-ignited combustion. Here, the mixed-mode combustion strategy is composed of a deflagration of a stratified mixture created by a late direct injection, then triggering a controlled autoignition of the surrounding gas, improving the robustness…
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The Effects of Intake Charge Preheating in a Gasoline-Fueled HCCI Engine

General Motors Research-James A. Eng, Paul M. Najt
University of Wisconsin-Madison Engine Research Center-Randy E. Herold, Rinaldo Augusta, David E. Foster, Jaal B. Ghandhi
Published 2005-10-24 by SAE International in United States
Experiments were performed on a homogeneously fueled compression ignition gasoline-type engine with a high degree of intake charge preheating. It was observed that fuels that contained lower end and/or non-branched hydrocarbons (gasoline and an 87 octane primary reference fuel (PRF) blend) exhibited sensitivity to thermal conditions in the surge tanks upstream of the intake valves. The window of intake charge temperatures, measured near the intake valve, that provided acceptable combustion was shifted to lower values when the upstream surge tank gas temperatures were elevated. The same behavior, however, was not observed while using isooctane as a fuel. Gas chromatograph mass spectrometer analysis of the intake charge revealed that oxygenated species were present with PRF 87, and the abundance of the oxygenated species appeared to increase with increasing surge tank gas temperatures. No significant oxygenated species were detected when running with isooctane. The presence of the oxygenated species for PRF 87 fueling indicated that reactions were occurring in the intake surge tanks which resulted in needing lower intake charge temperatures to achieve autoignition.
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Homogeneous Charge Compression Ignition (HCCI) Engines

Thomas N. Asmus, Dennis N. Assanis, John E. Dec, James A. Eng, Paul M. Najt
DaimlerChrysler Corp.-Fuquan Zhao
  • Progress In Technology (PT)
  • PT-94
Published 2003-03-03 by SAE International in United States
The homogeneous charge, compression-ignition (HCCI) combustion process has the potential to significantly reduce NOx and particulate emissions, while achieving high thermal efficiency and the capability of operating with a wide variety of fuels. This makes the HCCI engine an attractive technology that can ostensibly provide diesel-like fuel efficiency and very low emissions, which may allow emissions compliance to occur without relying on lean aftertreatment systems.
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Direct Injection Gasoline Engines

Paul M. Najt, Richard Steeper
  • Special Publication (SP)
  • SP-1640
Published 2001-09-24 by SAE International in United States

Twelve papers from the 2001 SAE International Fall Fuels & Lubricants Meeting.

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An Experimental and Computational Evaluation of Two Dual-Intake-Valve Combustion Chambers

Engine Research Dept., General Motors Research Laboratories-Paul M. Najt, Tang-Wei Kuo
Published 1990-10-01 by SAE International in United States
Multi-dimensional computations were made of spark-ignited premixed-charge combustion in two engines having pent-roof-shaped combustion chambers and two intake valves per cylinder, one with a central spark plug and the other with dual lateral spark plugs. The basic specifications for the two engines were the same except for differences in the number of spark plugs and exhaust valves. The effects of swirl and equivalence ratio on combustion, wall heat transfer, and nitric oxide emission characteristics were examined using a global combustion model that accounts for laminar-kinetics and turbulent-mixing effects. The initial conditions on both mean-flow and turbulence parameters at intake valve closing (IVC) were estimated in order to simulate engine operation either with both intake valves active or with one valve deactivated. The predictions were compared with experimentally derived pressure-time, heat loss, and nitric oxide emission data.The model, consistent with experimental data, indicates that the dual lateral ignition engine responds more favorably to valve deactivation as charge dilution is increased, and shows flame convection to be the source of the dual lateral ignition engine's superior dilute…
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Compression-Ignited Homogeneous Charge Combustion

University of Wisconsin-Madison Department of Mechanical Engineering-David E. Foster
University of Wisconsin-Madison, Department of Mechanical Engineering, Present Affiliation: G. M. Engineering Staff, G. M. Tech. Center, Warren, Ml-Paul M. Najt
Published 1983-02-01 by SAE International in United States
Experimentally obtained energy release results, a semi-empirical ignition model, and an empirical energy release equation developed during this research were used to evaluate the combustion of compression-ignited homogeneous mixtures of fuel, air, and exhaust products in a CFR engine. A systematic study was carried out to evaluate the response of compression-ignited homogeneous charge (CIHC) combustion to changes in operating parameters with emphasis being placed on the phenomena involved rather than the detailed chemical kinetics. This systematic study revealed that the response of the combustion process to changes in operating parameters can be explained in terms of known chemical kinetics, and that through the proper use of temperature and species concentrations the oxidation kinetics of hydrocarbon fuels can be sufficiently controlled to allow an engine to be operated in a compression-ignited homogeneous charge combustion mode.
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