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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Effects of H2 Addition to Compressed Natural Gas Blends on Cycle-to-Cycle and Cylinder-to-Cylinder Combustion Variation in a Spark-Ignition Engine

[+] Author and Article Information
Mirko Baratta

IC Engines Advanced Laboratory (ICEAL),
Politecnico di Torino,
C.so Duca degli Abruzzi, 24,
Torino 10129, Italy
e-mail: mirko.baratta@polito.it

Stefano d'Ambrosio

IC Engines Advanced Laboratory (ICEAL),
Politecnico di Torino,
C.so Duca degli Abruzzi, 24,
Torino 10129, Italy
e-mail: stefano.dambrosio@polito.it

Daniela Misul

IC Engines Advanced Laboratory (ICEAL),
Politecnico di Torino,
C.so Duca degli Abruzzi, 24,
Torino 10129, Italy
e-mail: daniela.misul@polito.it

Ezio Spessa

IC Engines Advanced Laboratory (ICEAL),
Politecnico di Torino,
C.so Duca degli Abruzzi, 24,
Torino 10129, Italy
e-mail: ezio.spessa@polito.it

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received March 28, 2013; final manuscript received November 29, 2013; published online January 2, 2014. Assoc. Editor: Paolo Chiesa.

J. Eng. Gas Turbines Power 136(5), 051502 (Jan 02, 2014) (12 pages) Paper No: GTP-13-1090; doi: 10.1115/1.4026163 History: Received March 28, 2013; Revised November 29, 2013

An experimental investigation and a burning-rate analysis have been performed on a production 1.4 liter compressed natural gas (CNG) engine fueled with methane-hydrogen blends. The engine features a pent-roof combustion chamber, four valves per cylinder, and a centrally located spark plug. The experimental tests have been carried out in order to quantify the cycle-to-cycle and the cylinder-to-cylinder combustion variation. Therefore, the engine has been equipped with four dedicated piezoelectric pressure transducers placed on each cylinder and located by the spark plug. At each test point, in-cylinder pressure, fuel consumption, induced air mass flow rate, pressure, and temperature at different locations on the engine intake and exhaust systems as well as “engine-out” pollutant emissions have been measured. The signals related to engine operation have been acquired by means of a National Instruments PXI-DAQ system and software developed in house. The acquired data have then been processed through a combustion diagnostic tool resulting from the integration of an original multizone thermodynamic model with a computer-aided design (CAD) procedure for the evaluation of the burned-gas front geometry. The diagnostic tool allows the burning velocities to be computed. The tests have been performed over a wide range of engine speeds, loads, and relative air-fuel ratios (up to the lean operation limit (LOL)). For stoichiometric operation, the addition of hydrogen to CNG has produced a brake-specific fuel combustion (bsfc) reduction ranging between 2% and 7% and a brake-specific total unburned hydrocarbons (bsTHCs) decrease up to 40%. These benefits have appeared to be even higher for lean mixtures. Hydrogen has shown to significantly enhance the combustion process, thus leading to a sensibly lower cycle-to-cycle variability. Hydrogen addition has generally resulted in extended operation up to relative air-to-fuel ratio (RAFR) = 1.8. Still, the LOL consistently varies depending on the considered cylinder.

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Figures

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Fig. 1

Average combustion and performance parameters for a load sweep at the indicated operating conditions

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Fig. 2

Average combustion and performance parameters for an N sweep at the indicated operating conditions

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Fig. 3

“Raw” engine emission data for a load sweep at the indicated operating conditions

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Fig. 4

Raw engine emission data for an N sweep at the indicated operating conditions

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Fig. 5

Average combustion and performance parameters for an RAFR sweep at the indicated operating conditions

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Fig. 6

Combustion efficiency for an RAFR sweep at the indicated operating conditions

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Fig. 7

Raw engine emission data for an RAFR sweep at the indicated operating conditions

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Fig. 8

Cylinder-to-cylinder pressure-related quantities for an RAFR-sweep at the indicated operating conditions

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Fig. 9

Cylinder-to-cylinder combustion-related quantities for an RAFR-sweep at the indicated operating conditions

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