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

Investigation of Combustion Phasing Control Strategy During Reactivity Controlled Compression Ignition (RCCI) Multicylinder Engine Load Transitions

[+] Author and Article Information
Yifeng Wu

Engine Research Center,
University of Wisconsin-Madison,
Madison, WI 53706
e-mail: yifengwu.mail@gmail.com

Reed Hanson

Engine Research Center,
University of Wisconsin-Madison,
Madison, WI 53706
e-mail: rmhanson2@wisc.edu

Rolf D. Reitz

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

1Corresponding author.

Contributed by the Coal, Biomass and Alternate Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received February 13, 2014; final manuscript received February 16, 2014; published online April 21, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(9), 091511 (Apr 21, 2014) (10 pages) Paper No: GTP-14-1087; doi: 10.1115/1.4027190 History: Received February 13, 2014; Revised February 16, 2014

The dual fuel reactivity controlled compression ignition (RCCI) concept has been successfully demonstrated to be a promising, more controllable, high efficiency, and cleaner combustion mode. A multidimensional computational fluid dynamics (CFD) code coupled with detailed chemistry, KIVA-CHEMKIN, was applied to develop a strategy for phasing control during load transitions. Steady-state operating points at 1500 rev/min were calibrated from 0 to 5 bar brake mean effective pressure (BMEP). The load transitions considered in this study included a load-up and a load-down load change transient between 1 bar and 4 bar BMEP at 1500 rev/min. The experimental results showed that during the load transitions, the diesel injection timing responded in two cycles while around five cycles were needed for the diesel common-rail pressure to reach the target value. However, the intake manifold pressure lagged behind the pedal change for about 50 cycles due to the slower response of the turbocharger. The effect of these transients on RCCI engine combustion phasing was studied. The CFD model was first validated against steady-state experimental data at 1 bar and 4 bar BMEP. Then the model was used to develop strategies for phasing control by changing the direct port fuel injection (PFI) amount during load transitions. Specific engine operating cycles during the load transitions (six cycles for the load-up transition and seven cycles for the load-down transition) were selected based on the change of intake manifold pressure to represent the transition processes. Each cycle was studied separately to find the correct PFI to diesel fuel ratio for the desired CA50 (the crank angle at which 50% of total heat release occurs). The simulation results showed that CA50 was delayed by 7 to 15 deg for the load-up transition and advanced by around 5 deg during the load-down transition if the precalibrated steady-state PFI table was used. By decreasing the PFI ratio by 10% to 15% during the load-up transition and increasing the PFI ratio by around 40% during the load-down transition, the CA50 could be controlled at a reasonable value during transitions. The control strategy can be used for closed-loop control during engine transient operating conditions. Combustion and emission results during load transitions are also discussed.

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Fig. 1

Typical response speed of the main components [7]

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Fig. 2

RCCI multicylinder diesel engine setup

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Fig. 3

Computation grid at TDC for stock piston (51.4 deg sector mesh, 13,079 cells at IVC)

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Fig. 4

KIVA simulation and experimental results at 1 bar and 4 bar BMEP steady state

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Fig. 5

Combustion/emission results of KIVA simulation and experimental at 1 bar and 4 bar BMEP steady state

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Fig. 6

Experimental results for load-up and load-down transient processes

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Fig. 7

Experimental and GT-Power simulated in-cylinder pressure at 4 bar BMEP

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Fig. 8

Simulation results of CA50 at different PFI ratios for each cycle during the engine transient

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Fig. 9

Simulation results of CA50 without PFI ratio control during transitions

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Fig. 10

Adjustment needed to control the combustion phasing at each cycle

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Fig. 11

Control strategy for load-up (1 bar to 4 bar BMEP) and load-down (4 bar to 1 bar BMEP) transitions. (ΔCA50 = desired CA50-current CA50)

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Fig. 12

Simulation results of the combustion and emission characteristics at each cycle during load-up (left) and load-down (right) transitions. (before/after: before/after PFI ratio adjustment for combustion phasing control, TE: thermal efficiency, CE: combustion efficiency)




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