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One-Dimensional Modeling of a Thermochemical Recuperation Scheme for Improving Spark-Ignition Range Extender Engine Efficiency

Univ of Minnesota-Twin Cities-William F. Northrop, Darrick Zarling
  • Technical Paper
  • 2019-24-0066
Published 2019-09-09 by SAE International in United States
Range extender (REx) engines have promise for providing low-cost energy for future battery electric vehicles. Due to their restricted operation range, REx engines provide an opportunity to implement system-level schemes that are less attractive for engines designed for highly transient operation. This paper explores a thermochemical recuperation (TCR) scheme for a 2-cylinder BMW spark-ignition REx engine using a 1-D model implemented in GT-Power™. The TCR reactor employs a unique catalytic heat exchange configuration that enables efficient transfer of exhaust sensible and chemical enthalpy to steam reform the incoming fuel. The engine model without the TCR reactor was validated using experimental emissions and performance data from a BMW engine operating on a test stand. A custom integrated heat exchanger and catalyst model was created and integrated with the validated engine. A parametric modeling sweep was conducted with iso-octane as fuel over a range of reformed fuel fraction. With the TCR reactor operating at a molar steam to carbon ratio of 1.0, engine efficiency was increased by 2.9% over the baseline REx engine within the most efficient…
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Fuel Reforming and Catalyst Deactivation Investigated in Real Exhaust Environment

Raphael Gukelberger
Bartley Consulting LLC-Gordon Bartley
Published 2019-04-02 by SAE International in United States
Increased in-cylinder hydrogen levels have been shown to improve burn durations, combustion stability, HC emissions and knock resistance which can directly translate into enhanced engine efficiency. External fuel reformation can also be used to increase the hydrogen yield. During the High-Efficiency, Dilute Gasoline Engine (HEDGE) consortium at Southwest Research Institute (SwRI), the potential of increased hydrogen production in a dedicated-exhaust gas recirculation (D-EGR) engine was evaluated exploiting the water gas shift (WGS) and steam reformation (SR) reactions. It was found that neither approach could produce sustained hydrogen enrichment in a real exhaust environment, even while utilizing a lean-rich switching regeneration strategy. Platinum group metal (PGM) and Ni WGS catalysts were tested with a focus on hydrogen production and catalyst durability. Although 4% additional hydrogen was initially produced in the EGR stream, leading to improvements in the coefficient of variation (CoV) and brake specific fuel consumption (BSFC), catalyst activity decreased within a few hours regardless of the regeneration strategy employed. With an SR catalyst, a small amount of hydrogen was produced in the EGR stream via…
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High Load Expansion of Catalytic EGR-Loop Reforming under Stoichiometric Conditions for Increased Efficiency in Spark Ignition Engines

SAE International Journal of Advances and Current Practices in Mobility

Oak Ridge National Laboratory-James P. Szybist, Josh Pihl, Shean Huff, Brian Kaul
  • Journal Article
  • 2019-01-0244
Published 2019-04-02 by SAE International in United States
The use of fuel reformate from catalytic processes is known to have beneficial effects on the spark-ignited (SI) combustion process through enhanced dilution tolerance and decreased combustion duration, but in many cases reformate generation can incur a significant fuel penalty. In a previous investigation, the researchers showed that, by controlling the boundary conditions of the reforming catalyst, it was possible to minimize the thermodynamic expense of the reforming process, and in some cases, realize thermochemical recuperation (TCR), a form of waste heat recovery where exhaust heat is converted to usable chemical energy. The previous work, however, focused on a relatively light-load engine operating condition of 2000 rpm, 4 bar brake mean effective pressure (BMEP). The present investigation demonstrates that this operating strategy is applicable to higher engine loads, including boosted operation up to 10 bar BMEP. By controlling the reforming catalyst boundary conditions, it is possible to achieve fuel reforming without experiencing high temperature exotherms that could be damaging to the catalyst. Additionally, the thermodynamic air handling consequences of operating a highly dilute strategy at…
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Fuel and Engine Effects on Rich-Combustion Products as an Enabler of In-Cylinder Reforming

Aramco Research Center-Alexander K. Voice, Vincent Costanzo
Published 2019-04-02 by SAE International in United States
Onboard reforming has been proposed as a strategy for improving spark-ignited (SI) engine efficiency through knock reduction, dilution limit extension, improved thermodynamic gas properties, and thermochemical exhaust enthalpy recuperation. One approach to onboard fuel reforming is to combust fuel in the engine cylinder under rich conditions, producing a hydrogen-rich reformate gas--which can subsequently be recirculated into the engine. Hydrogen is the preferred product in this process due to its high flame speed and knock resistance, compared with other reformate constituents.In this work, the effects of engine operation, fuel composition and water injection were evaluated for their effect on reformate gas composition produced under rich combustion conditions. Engine parameters, including intake pressure, intake temperature, combustion phasing, and valve timing all had no significant impact on hydrogen yield at a given equivalence ratio. Fuel effects on hydrogen yield were more significant--with methanol producing 75% more hydrogen than toluene at the same equivalence ratio. The greater hydrogen yield was due to greater hydrogen content of the fuel, although the benefit was shown to be partially offset by lower…
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Advances in Partial Oxidation of Palm Oil Based Biodiesel Reforming to Hydrogen Production for Diesel Engine Applications

KMUTNB-Kampanart Theinnoi, Boonlue Sawatmongkhon, Warirat Temwutthikun, Thawatchai Wongchang
Published 2019-03-25 by SAE International in United States
The aims of this research is investigate the hydrogen production via biodiesel fuel partial oxidation reforming. Hydrogen production can enhance combustion in cylinder and improved aftertreatment activities. A reforming reaction is when a chemical reacts with oxygen available in exhaust gas and diesel fuel injection. The 2%Pt-1%Rh-CeO2-ZrO2/γ-Al2O3 was selected as the active catalyst in this research. This study investigates the effect of gas space velocity (SV) (e.g., 10k h-1 and 16k h-1) and fuel addition flow rate (10-30 ml/h) on hydrogen production efficiency. As can be seen that the hydrogen from reforming reaction was promoted under the real engine operating conditions. Hydrogen is produced via partial oxidation of hydrocarbons reforming. The effects of space velocity SV (h−1) and hydrocarbon addition, which enhanced energy input for the reforming process, are the main effect on hydrogen production over the reforming catalyst. The maximum hydrogen yield are achieved 11%. In the future, hydrogen production via partial oxidation fuel reforming could be developed for production of hydrogen on-board the vehicle.
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Fuel Cell/Fuel Cell Hybrid System

  • Magazine Article
  • TBMG-33933
Published 2019-03-01 by Tech Briefs Media Group in United States

Fuel cells can deliver clean, reliable, and uninterrupted power nearly 100 percent of the time. Fuel cells offer the advantage of efficiency by converting chemical energy directly to electricity. They have no moving parts, thereby eliminating failures associated with pumps, blowers, heat exchangers, and other systems. All fuel cells, particularly high-temperature fuel cells, require spent fuel/waste heat recovery subsystems, and low-temperature fuel cells require fuel reforming subsystems that lower the efficiency of the entire system.

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Onboard Natural Gas Reforming for Heavy Duty Vehicles

SAE International Journal of Commercial Vehicles

ExxonMobil Annuitant, USA-Walter Weissman
ExxonMobil Research and Engineering Company, USA-Brian Weiss, Tilman W. Beutel, Bryan R. Chapman, Jonathan D. Saathoff, Shamel Merchant, Gerardo J. Majano
  • Journal Article
  • 02-12-01-0004
Published 2019-01-07 by SAE International in United States
Powertrain simulations and catalyst studies showed the efficiency credits and feasibility of onboard reforming as a way to recover waste heat from heavy duty vehicles (HDVs) fueled by natural gas (NG). Onboard reforming involves 1) injecting NG into the exhaust gas recycle (EGR) loop of the HDV, 2) reforming NG on a catalyst in the EGR loop to hydrogen and carbon monoxide, and 3) combusting the reformed fuel in the engine. The reformed fuel has increased heating value (4-10% higher LHV) and flame speed over NG, allowing stable flames in spark ignition (SI) engines at EGR levels up to 25-30%. A sulfur-tolerant reforming catalyst was shown to reform a significant amount of NG (15-30% conversion) using amounts of precious metal near the current practice for HDV emissions control (10 g rhodium). Engine simulations showed that the high EGR levels enabled by onboard reforming are used most effectively to control engine load instead of waste-gating or throttling. This leads to 3% efficiency gain due to reduced pumping losses and enables the engine to run while the…
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High-Power-Density Solid Oxide Fuel Cell

  • Magazine Article
  • TBMG-33394
Published 2018-12-01 by Tech Briefs Media Group in United States

NASA's Glenn Research Center has developed a novel solid oxide fuel cell (SOFC) with five times the specific power density of currently available SOFCs. This highly efficient SOFC can operate on a wide range of both hydrogen and hydrocarbon-based fuels including methane, diesel, or jet fuel without reformers.

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Effects of Low Temperature Reforming (LTR) Products of Low Octane Number Fuels on HCCI Combustion

Tianjin University-Chao Geng, Hai Feng Liu, Xinghui Fang, Zhi Yang, Yanqing Cui, Yu Wang, Lei Feng, Mingfa Yao
Published 2018-09-10 by SAE International in United States
In order to achieve high-efficiency and clean combustion in HCCI engines, combustion must be controlled reasonably. A great variety of species with various reactivities can be produced through low temperature oxidation of fuels, which offers possible solutions to the problem of controlling in-cylinder mixture reactivity to accommodate changes in the operating conditions. In this work, in-cylinder combustion characteristics with low temperature reforming (LTR) were investigated in an optical engine fueled with low octane number fuel. LTR was achieved through low temperature oxidation of fuels in a reformer (flow reactor), and then LTR products (oxidation products) were fed into the engine to alter the charge reactivity. Primary Reference Fuels (blended fuel of n-heptane and iso-octane, PRFs) are often used to investigate the effects of octane number on combustion characteristics in engines. Then PRF0 (n-heptane) and PRF50 (mixture of 50% n-heptane and 50% iso-octane by volume) were chosen as representative low octane number fuels. LTR products were quantitatively detected using online gas chromatograph (GC). High-speed imaging was conducted to illustrate the flame development. A single-zone model was…
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Reformed Fuel Substitution for Transient Peak Soot Reduction

University of Wisconsin Madison-Flavio Dal Forno Chuahy, Jamen Olk, Sage Kokjohn
Published 2018-04-03 by SAE International in United States
Advancements in catalytic reforming have demonstrated the ability to generate syngas (a mixture of CO and hydrogen) from a single hydrocarbon stream. This syngas mixture can then be used to replace diesel fuel and enable dual-fuel combustion strategies. The role of port-fuel injected syngas, comprised of equal parts hydrogen and carbon monoxide by volume was investigated experimentally for soot reduction benefits under a transient load change at constant speed. The syngas used for the experiments was presumed to be formed via a partial oxidation on-board fuel reforming process and delivered through gaseous injectors using a custom gas rail supplied with bottle gas, mounted in the swirl runner of the intake manifold. Time-based ramping of the direct-injected fuel with constant syngas fuel mass delivery from 2 to 8 bar brake mean effective pressure was performed on a multi-cylinder, turbocharged, light-duty engine to determine the effects of syngas on transient soot emissions. A Cambustion fNOx400 high-speed emissions analyzer and an AVL 439 opacimeter were used to quantify emissions under the load change to provide sub-cycle and cycle resolved…
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