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Research Papers: Gas Turbines: Industrial & Cogeneration

A Highly Efficient Small-Displacement Marine Two-Stroke H2DI Engine With Low Emissions

[+] Author and Article Information
David Oh

e-mail: david.oh@usherbrooke.ca

Jean-Sébastien Plante

e-mail: jean-sebastien.plante@usherbrooke.ca
Department of Mechanical Engineering,
Université de Sherbrooke,
2500 boul. de l'Université,
Sherbrooke,
Québec J1K 2R1, Canada

Contributed by the IC Engine Division of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received November 19, 2012; final manuscript received February 14, 2013; published online June 24, 2013. Editor: David Wisler.

J. Eng. Gas Turbines Power 135(8), 082001 (Jun 24, 2013) (10 pages) Paper No: GTP-12-1441; doi: 10.1115/1.4023752 History: Received November 19, 2012; Revised February 14, 2013

A hydrogen-fueled two-stroke prototype demonstrator based on a 9.9 hp (7.4 kW) production gasoline marine outboard engine is presented, which, while matching the original engine's rated power output on hydrogen, achieves a best-point gross indicated thermal efficiency (ITE) of 42.4% at the ICOMIA mode 4 operating point, corresponding to 80% and 71.6% of the rated engine speed and torque, respectively. The brake thermal efficiency (BTE) at the rated power is 32.3%. Preliminary exhaust gas measurements suggest that the engine could also meet the most stringent CARB 5-Star marine spark-ignition emission standards limiting HC + NOx emissions to 2.5 g/kWh without any after-treatment. These are realized in a cost-effective concept around a proven two-stroke base engine and a low-pressure direct-injected gaseous hydrogen (LPDI GH2) system, which employs no additional fuel pump and is uniquely adapted from volume production components. Later fuel injection is found to improve thermal efficiency at the expense of increased NOx emissions and, at the extreme, increased cyclic variation. These observations are hypothesized and supported by phenomenological inferences of the observed trends of combustion duration, NOx concentration, and indicated mean effective pressure (IMEP) variance to be due to increasing charge stratification with the later timings. This work outlines the pathway—including investigations of several fuel delivery strategies with limited success—leading to the current status, including design, modeling with GT-POWER, delivery of lube oil, lubrication issues using hydrogen, and calibration sweeps. The experimental results comprising steady-state dynamometer performance, cylinder pressure traces, NOx emission measurements, along with heat release analyses, support the reported numbers and the key finding that late fuel injection timing and charge stratification drive the high efficiencies and the NOx trade-off; this is discussed and forms the basis for future work.

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References

Figures

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Fig. 1

(top) Black sludge collected from the cylinder head; (middle) white foamy sludge in the crankcase; (bottom) varnish and rust formation on the cylinder liner

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Fig. 2

GT-POWER model map

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Fig. 3

Purity and delivery ratios with the scatterband sketched

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Fig. 4

Comparison of the simulation and experimental cylinder pressure traces

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Fig. 5

Indicated thermal efficiency versus indicated mean effective pressure (MBT spark timings)

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Fig. 6

Effect of injection timing on the indicated thermal efficiency, constant gas mass flow, ICOMIA mode 4, and MBT ignition timing

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Fig. 7

Effect of end-of-injection timing on the burn duration at ICOMIA mode 4; MBT ignition timing

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Fig. 8

Effect of end-of-injection timing on the NOx concentration at ICOMIA mode 4; MBT ignition timing

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Fig. 9

Coefficient of variance of the IMEP versus injection timing; 3000 RPM; 0.1 g/s gas flow; MBT ignition timing

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Fig. 10

Raw instantaneous apparent heat release rate plots of 50 sequential cycles; ICOMIA mode 5

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Fig. 11

Cumulative heat release Vibe curve-fits of 50 sequential cycles and 300-cycle ensemble average; ICOMIA mode 5

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Fig. 12

Coefficient of variance of the IMEP and thermal efficiencies over each mode of the ICOMIA cycle

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Fig. 13

ICOMIA cycle NOx emissions and hydrogen consumption; efficiency-optimized calibration

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Fig. 14

Comparison of the brake thermal efficiency and specific fuel consumption at the rated power (ICOMIA mode 5); hydrogen versus gasoline engines (energy-equivalent basis); gasoline engine data from Ref. [20]

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