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

High Load (21 Bar IMEP) Dual Fuel RCCI Combustion Using Dual Direct Injection

[+] Author and Article Information
Jae Hyung Lim

Engine Research Center,
University of Wisconsin–Madison,
1500 Engineering Drive,
Madison, WI 53706
e-mail: jlim33@wisc.edu

Rolf D. Reitz

Engine Research Center,
University of Wisconsin–Madison,
1500 Engineering Drive,
Madison, WI 53706
e-mail: reitz@engr.wisc.edu

1Corresponding author.

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received February 17, 2014; final manuscript received March 18, 2014; published online May 9, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(10), 101514 (May 09, 2014) (10 pages) Paper No: GTP-14-1106; doi: 10.1115/1.4027361 History: Received February 17, 2014; Revised March 18, 2014

Dual-fuel reactivity controlled compression ignition (RCCI) combustion has shown high thermal efficiency and superior controllability with low NOx and soot emissions. However, as in other low temperature combustion (LTC) strategies, the combustion control using low exhaust gas recirculation (EGR) or a high compression ratio at high load conditions has been a challenge. The objective of this work was to examine the efficacy of using dual direct injectors for combustion phasing control of high load RCCI combustion. The present computational work demonstrates that 21 bar gross indicated mean effective pressure (IMEP) RCCI is achievable using dual direct injection. The simulations were done using the KIVA3V-Release 2 code with a discrete multicomponent fuel evaporation model, coupled with sparse analytical Jacobian solver for describing the chemistry of the two fuels (iso-octane and n-heptane). In order to identify an optimum injection strategy a nondominated sorting genetic algorithm II (NSGA II), which is a multiobjective genetic algorithm, was used. The goal of the optimization was to find injection timings and mass splits among the multiple injections that simultaneously minimize the six objectives: soot, nitrogen oxide (NOx), carbon monoxide (CO), unburned hydrocarbon (UHC), indicated specific fuel consumption (ISFC), and ringing intensity. The simulations were performed for a 2.44 liter, heavy-duty engine with a 15:1 compression ratio. The speed was 1800 rev/min and the intake valve closure (IVC) conditions were maintained at 3.42 bar, 90 °C, and 46% EGR. The resulting optimum condition has 12.6 bar/deg peak pressure rise rate, 158 bar maximum pressure, and 48.7% gross indicated thermal efficiency. The NOx, CO, and soot emissions are very low.

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Fig. 1

HCCI combustion of port-injected iso-octane with 46% EGR

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Fig. 2

Schematic representation of the injection strategy for the high load RCCI operation

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Fig. 3

Computational grid at TDC

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Fig. 4

Computational grid at TDC for the RCCI validation cases (red and green arrows indicate the injection direction of iso-octane and n-heptane, respectively)

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Fig. 5

The validation cases pressure traces and HRR

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Fig. 6

Validation case emissions

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Fig. 7

Optimum design injection strategy

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Fig. 8

Injection profiles of the optimum case

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Fig. 9

Pressure trace and heat release rate of the optimum case

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Fig. 10

In-cylinder equivalence ratio evolution

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Fig. 11

In-cylinder temperature evolution

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Fig. 12

Sources of emissions (soot, NOx, CO, and UHC)

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Fig. 13

Effect of the mass and SOI change (1st injection). The red crosses on the upper right corner indicate the overlap of the 1st and 2nd injections.

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Fig. 14

Effect of the 1st injection on the squish temperature

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Fig. 15

Inadequate combustion due to low squish temperature

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Fig. 16

Effect of the mass and SOI change (2nd injection) on the ringing intensity

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Fig. 17

Effect of the early 2nd injection

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Fig. 18

Smearing of the n-heptane vapor

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Fig. 19

Effect of the mass and SOI change (3rd injection) on the combustion control and emission

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Fig. 20

Varying n-heptane mass and SOI3 resulting in similar pressure traces




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