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Research Papers: Internal Combustion Engines

The Fuel Mix Limits and Efficiency of a Stoichiometric, Ammonia, and Gasoline Dual Fueled Spark Ignition Engine

[+] Author and Article Information
Shawn M. Grannell

Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109-2133sgrannel@umich.edu

Dennis N. Assanis, Stanislav V. Bohac, Donald E. Gillespie

Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109-2133

J. Eng. Gas Turbines Power 130(4), 042802 (Apr 28, 2008) (8 pages) doi:10.1115/1.2898837 History: Received February 07, 2007; Revised February 09, 2008; Published April 28, 2008

An overall stoichiometric mixture of air, gaseous ammonia, and gasoline was metered into a single cylinder, variable compression ratio, supercharged cooperative fuel research (CFR) engine at varying ratios of gasoline to ammonia. The engine was operated such that the combustion was knock-free with minimal roughness for all loads ranging from idle up to a maximum load in the supercharge regime. For a given load, speed, and compression ratio, there was a range of ratios of gasoline to ammonia for which knock-free, smooth firing was obtained. This range was investigated at its rough limit and also at its maximum brake torque (MBT) knock limit. If too much ammonia was used, then the engine fired with an excessive roughness. If too much gasoline was used, then knock-free combustion could not be obtained while the maximum brake torque spark timing was maintained. Stoichiometric operation on gasoline alone is also presented, for comparison. It was found that a significant fraction of the gasoline used in spark ignition engines could be replaced with ammonia. Operation on about 100% gasoline was required at idle. However, a fuel mix comprising 70% ammonia∕30% gasoline on an energy basis could be used at normally aspirated, wide open throttle. Even greater ammonia to gasoline ratios were permitted for supercharged operation. The use of ammonia with gasoline allowed knock-free operation with MBT spark timing at higher compression ratios and higher loads than could be obtained with the use of gasoline alone.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Fuel mix sweep, 8:1, 1600rpm, and IMEPn∼550kPa

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Figure 2

Fuel mix sweep, 12:1, 1600rpm, and IMEPn∼260kPa

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Figure 3

Fuel mix sweep, 9:1, 1000rpm, WOT, and IMEPn∼700kPa

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Figure 4

Apparent mass fraction burned curves for the first five individual cycles showing the effect of ammonia at 9:1, 1000rpm, and WOT

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Figure 5

Cylinder pressure curves for the first five individual cycles showing the effect of ammonia at 9:1, 1000rpm, and WOT. The rough limit fuel mix was 82% NH3∕18% gasoline.

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Figure 6

Fuel mix at the rough limit, grouped by compression ratio

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Figure 7

The instantaneous volume ratio from BC, as a function of crank angle

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Figure 8

Fuel mix at the rough limit, grouped by speed

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Figure 9

Fuel mix at the MBT knock limit (solid shapes), all speeds. The hollow triangles are the 8:1 and 10:1 rough limit points from Fig. 6.

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Figure 10

Net indicated thermal efficiency for operation on ammonia with gasoline at the rough limit, all speeds

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Figure 11

Net indicated thermal efficiency for operation on ammonia with gasoline at the MBT knock limit, all speeds

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Figure 12

Net indicated thermal efficiency for gasoline, all speeds

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