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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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Combustion-Timing Control of Low-Temperature Gasoline Combustion (LTGC) Engines by Using Double Direct-Injections to Control Kinetic Rates

General Motors LLC-Jeremie Dernotte
Sandia National Laboratories-Gerald Gentz, Chunsheng Ji, Dario Lopez Pintor, John Dec
Published 2019-04-02 by SAE International in United States
Low-temperature gasoline combustion (LTGC) engines can provide high efficiencies and extremely low NOx and particulate emissions, but controlling the combustion timing remains a challenge. This paper explores the potential of Partial Fuel Stratification (PFS) to provide fast control of CA50 in an LTGC engine. Two different compression ratios are used (CR=16:1 and 14:1) that provide high efficiencies and are compatible with mixed-mode SI-LTGC engines. The fuel used is a research grade E10 gasoline (RON 92, MON 85) representative of a regular-grade market gasoline found in the United States. The fuel was supplied with a gasoline-type direct injector (GDI) mounted centrally in the cylinder. To create the PFS, the GDI injector was pulsed twice each engine cycle. First, an injection early in the intake stroke delivered the majority of the fuel (70 - 80%), establishing the minimum equivalence ratio in the charge. Then, a second injection supplied the remainder of the fuel (20 - 30%) at a variable timing during the compression stroke, from 200° to 330°CA (0°CA = TDC-intake, 360°CA = TDC-compression) to provide controlled…
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Refining Measurement Uncertainties in HCCI/LTGC Engine Experiments

Lawrence Livermore National Laboratory-Guillaume Petitpas, Russell Whitesides
Sandia National Laboratories-Jeremie Dernotte, John Dec
Published 2018-04-03 by SAE International in United States
This study presents estimates for measurement uncertainties for a Homogenous Charge Compression Ignition (HCCI)/Low-Temperature Gasoline Combustion (LTGC) engine testing facility. A previously presented framework for quantifying those uncertainties developed uncertainty estimates based on the transducers manufacturers’ published tolerances. The present work utilizes the framework with improved uncertainty estimates in order to more accurately represent the actual uncertainties of the data acquired in the HCCI/LTGC laboratory, which ultimately results in a reduction in the uncertainty from 30 to less than 1 kPa during the intake and exhaust strokes. Details of laboratory calibration techniques and commissioning runs are used to constrain the sensitivities of the transducers relative to manufacturer supplied values. The uncertainty framework is also extended to consider additional sources of uncertainty, including non-ideal engine volume history due to kinematic effects on the effective connecting rod length. Finally, the uncertainty propagation chain is analyzed to determine primary uncertainty sources, and mitigations are discussed.
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Spark Assist for CA50 Control and Improved Robustness in a Premixed LTGC Engine – Effects of Equivalence Ratio and Intake Boost

General Motors LLC-Jeremie Dernotte
Sandia National Laboratories-Gerald Gentz, John Dec
Published 2018-04-03 by SAE International in United States
Low-temperature gasoline combustion (LTGC) engines can deliver high efficiencies, with ultra-low emissions of nitrogen oxides (NOx) and particulate matter (PM). However, controlling the combustion timing and maintaining robust operation remains a challenge for LTGC engines. One promising technique to overcoming these challenges is spark assist (SA). In this work, well-controlled, fully premixed experiments are performed in a single-cylinder LTGC research engine at 1200 rpm using a cylinder head modified to accommodate a spark plug. Compression ratios (CR) of 16:1 and 14:1 were used during the experiments. Two different fuels were also tested, with properties representative of premium- and regular-grade market gasolines. SA was found to work well for both CRs and fuels. The equivalence ratio (ϕ) limits and the effect of intake-pressure boost on the ability of SA to compensate for a reduced Tin were studied. For the conditions studied, ϕ=0.42 was found to be most effective for SA. At lower equivalence ratios the flame propagation was too weak, whereas ϕ=0.45 was closer to the CI knock/stability limit, which resulted in a smaller range of CA50…
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Increasing the Load Range, Load-to-Boost Ratio, and Efficiency of Low-Temperature Gasoline Combustion (LTGC) Engines

SAE International Journal of Engines

Sandia National Laboratories-John E. Dec, Jeremie Dernotte, Chunsheng Ji
  • Journal Article
  • 2017-01-0731
Published 2017-03-28 by SAE International in United States
Low-temperature gasoline combustion (LTGC) has the potential to provide gasoline-fueled engines with efficiencies at or above those of diesel engines and extremely low NOx and particulate emissions. Three key performance goals for LTGC are to obtain high loads, reduce the boost levels required for these loads, and achieve high thermal efficiencies (TEs). This paper reports the results of an experimental investigation into the use of partial fuel stratification, produced using early direct fuel injection (Early-DI PFS), and an increased compression ratio (CR) to achieve significant improvements in these performance characteristics. The experiments were conducted in a 0.98-liter single-cylinder research engine. Increasing the CR from 14:1 to 16:1 produced a nominal increase in the TE of about one TE percentage unit for both premixed and Early-DI PFS operation. Compared to fully premixed fueling, Early-DI PFS allowed significant CA50 advancement, resulting in higher TEs for both CRs, with peak gross-indicated TEs of 48.4% and 49.8% for CRs of 14:1 and 16:1, respectively. Early-DI PFS was also found to be very effective for increasing the high-load limit over…
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Efficiency Improvement of Boosted Low-Temperature Gasoline Combustion Engines (LTGC) Using a Double Direct-Injection Strategy

Sandia National Laboratories-Jeremie Dernotte, John Dec, Chunsheng Ji
Published 2017-03-28 by SAE International in United States
For lean or dilute, boosted gasoline compression-ignition engines operating in a low-temperature combustion mode, creating a partially stratified fuel charge mixture prior to auto-ignition can be beneficial for reducing the heat-release rate (HRR) and the corresponding maximum rate of pressure rise. As a result, partial fuel stratification (PFS) can be used to increase load and/or efficiency without knock (i.e. without excessive ringing). In this work, a double direct-injection (D-DI) strategy is investigated for which the majority of the fuel is injected early in the intake stroke to create a relatively well-mixed background mixture, and the remaining fuel is injected in the latter part of the compression stroke to produce greater fuel stratification prior auto-ignition. Experiments were performed in a 1-liter single-cylinder engine modified for low-temperature gasoline combustion (LTGC) research. The main objective of this study is to quantify the effects on the HRR and efficiency gains possible by applying this D-DI fueling technique to a near-perfectly homogeneous mixture and to a moderately stratified mixture (all the fuel injected early in the intake stroke). For the…
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Boosted Premixed-LTGC / HCCI Combustion of EHN-doped Gasoline for Engine Speeds Up to 2400 rpm

SAE International Journal of Engines

Chevron Energy Technology Company-William Cannella
Sandia National Laboratories-Chunsheng Ji, John Dec, Jeremie Dernotte
  • Journal Article
  • 2016-01-2295
Published 2016-10-17 by SAE International in United States
Previous work has shown that conventional diesel ignition improvers, 2-ethylhexyl nitrate (EHN) and di-tert-butyl peroxide (DTBP), can be used to enhance the autoignition of a regular-grade E10 gasoline in a well premixed low-temperature gasoline combustion (LTGC) engine, hereafter termed an HCCI engine, at naturally aspirated and moderately boosted conditions (up to 180 kPa absolute) with a constant engine speed of 1200 rpm and a 14:1 compression ratio. In the current work the effect of EHN on boosted HCCI combustion is further investigated with a higher compression ratio (16:1) piston and over a range of engine speeds (up to 2400 rpm). The results show that the higher compression ratio and engine speeds can make the combustion of a regular-grade E10 gasoline somewhat less stable. The addition of EHN improves the combustion stability by allowing combustion phasing to be more advanced for the same ringing intensity. The high-load limits of both the straight (unadditized) and additized fuels are determined, and the additized fuel is found to achieve a higher maximum load at all engine speeds and intake…
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Effects of Gasoline Reactivity and Ethanol Content on Boosted, Premixed and Partially Stratified Low-Temperature Gasoline Combustion (LTGC)

SAE International Journal of Engines

Sandia National Laboratories-John E. Dec, Jeremie Dernotte, Chunsheng Ji
Univ of Melbourne-Yi Yang
  • Journal Article
  • 2015-01-0813
Published 2015-04-14 by SAE International in United States
Low-temperature gasoline combustion (LTGC), based on the compression ignition of a premixed or partially premixed dilute charge, can provide thermal efficiencies (TE) and maximum loads comparable to those of turbo-charged diesel engines, and ultra-low NOx and particulate emissions. Intake boosting is key to achieving high loads with dilute combustion, and it also enhances the fuel's autoignition reactivity, reducing the required intake heating or hot residuals. These effects have the advantages of increasing TE and charge density, allowing greater timing retard with good stability, and making the fuel ϕ- sensitive so that partial fuel stratification (PFS) can be applied for higher loads and further TE improvements. However, at high boost the autoignition reactivity enhancement can become excessive, and substantial amounts of EGR are required to prevent overly advanced combustion. Accordingly, an experimental investigation has been conducted to determine how the tradeoff between the effects of intake boost varies with fuel-type and its impact on load range and TE. Five fuels are investigated: a conventional AKI=87 petroleum-based gasoline (E0), and blends of 10 and 20% ethanol with…
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Energy Distribution Analysis in Boosted HCCI-like / LTGC Engines - Understanding the Trade-Offs to Maximize the Thermal Efficiency

SAE International Journal of Engines

Sandia National Laboratories-Jeremie Dernotte, John E. Dec, Chunsheng Ji
  • Journal Article
  • 2015-01-0824
Published 2015-04-14 by SAE International in United States
A detailed understanding of the various factors affecting the trends in gross-indicated thermal efficiency with changes in key operating parameters has been carried out, applied to a one-liter displacement single-cylinder boosted Low-Temperature Gasoline Combustion (LTGC) engine. This work systematically investigates how the supplied fuel energy splits into the following four energy pathways: gross-indicated thermal efficiency, combustion inefficiency, heat transfer and exhaust losses, and how this split changes with operating conditions. Additional analysis is performed to determine the influence of variations in the ratio of specific heat capacities (γ) and the effective expansion ratio, related to the combustion-phasing retard (CA50), on the energy split. Heat transfer and exhaust losses are computed using multiple standard cycle analysis techniques. The various methods are evaluated in order to validate the trends.This work focuses on explaining the trends in thermal efficiency and the various energy-loss terms for independent sweeps of fueling rate, intake temperature and engine speed. Trends in thermal efficiency can be well-explained by considering variations in combustion efficiency, CA50 retard, γ and heat transfer. By identifying the energy…
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Investigation of the Sources of Combustion Noise in HCCI Engines

SAE International Journal of Engines

Sandia National Labs.-Jeremie Dernotte, John E. Dec, Chunsheng Ji
  • Journal Article
  • 2014-01-1272
Published 2014-04-01 by SAE International in United States
This article presents an investigation of the sources combustion-generated noise and its measurement in HCCI engines. Two cylinder-pressure derived parameters, the Combustion Noise Level (CNL) and the Ringing Intensity (RI), that are commonly used to establish limits of acceptable operation are compared along with spectral analyses of the pressure traces. This study focuses on explaining the differences between these two parameters and on investigating the sensitivity of the CNL to the ringing/knock phenomenon, to which the human ear is quite sensitive. Then, the effects of independently varying engine operating conditions such as fueling rate, boost pressure, and speed on both the CNL and RI are studied.Results show that the CNL is not significantly affected by the high-frequency components related to the ringing/knock phenomenon. In contrast, CNL is found to be sensitive to increasing energy in the 0.4 to 2.0 kHz frequency range generated by the combustion-induced uniform pressure rise. Parametric investigations emphasize the fact that the RI and the CNL are designed to provide two distinctly different but complementary measurements. RI is designed to correlate…
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