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

An Experimental Study on Smoke Reduction Effect of Post Injection in Combination With Pilot Injection for a Diesel Engine

[+] Author and Article Information
Long Liu

e-mail: liulong210@gmail.com

Takuji Ishiyama

Graduate School of Energy Science,
Kyoto University,
Sakyo-ku,
Kyoto 606-8501, Japan

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 December 4, 2012; final manuscript received November 2, 2013; published online December 10, 2013. Assoc. Editor: Zoran S. Filipi.

J. Eng. Gas Turbines Power 136(4), 041502 (Dec 10, 2013) (8 pages) Paper No: GTP-12-1468; doi: 10.1115/1.4025929 History: Received December 04, 2012; Revised November 02, 2013

With the universal utilization of the common-rail injection system in automotive diesel engines, the multistage injection strategies have become typical approaches to satisfy the increasingly stringent emission regulations, and especially the post injection has received considerable attention as an effective way for reducing the smoke emissions. Normally the post injection is applied in combination with the pilot injection to restrain the NOx emissions, smoke emissions, and combustion noise simultaneously, and the pilot injection condition affects the combustion process of the main injection and might affect the smoke reduction effect of the post injection. Thus this study aims at obtaining the post injection strategy to reduce smoke emissions in a diesel engine, where post injection is employed in combination with pilot injection. The experiments were performed using a single-cylinder diesel engine under various conditions of pilot and post injection with a constant load at an IMEP of 1.01 MPa, fixed speed of 1500 rpm, and NOx emissions concentration of 150 ± 5 ppm that was maintained by adjusting the EGR ratio. The injection pressure was set at 90 MPa at first, and then it was varied to 125 MPa to evaluate the effects of post injection on the smoke reduction in the case of higher injection pressure. The experimental results show that small post injection quantity with a short interval from the end of main injection causes less smoke emissions. And larger pilot injection quantity and later pilot injection timing lead to higher smoke emissions. And then, to explore and interpret the smoke emissions tendencies with varying pilot and post injection conditions, the experimental results of three-stage injection conditions were compared to those of two reference cases, which only included the pilot and main injection, and the interaction between main spray flames and post sprays was applied for analysis. Based on the comparative analysis, the larger smoke reduction effect of post injection was observed with the larger pilot injection quantity, while it is not greatly influenced by pilot injection timing. In addition, the smoke emissions can be reduced considerably by increasing the injection pressure, however the smoke reduction effect of post injection was attenuated. And all of these tendencies were able to be interpreted by considering the intensity variation of the interaction between main spray flames and post sprays.

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References

Figures

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Fig. 1

Experimental setup

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Fig. 2

Effects of post injection conditions on emissions and performance (qpilot = 4 mm3, θpilot = −19 deg ATDC)

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Fig. 3

Effects of post injection timing on heat release rate and in-cylinder pressure (θpilot = −19 deg ATDC, qpilot = 4 mm3, qpost = 2 mm3)

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Fig. 4

Effects of pilot injection quantity and post injection timing on smoke emission and performance (θpilot = −19 deg ATDC, qpost = 2 mm3)

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Fig. 5

Effects of pilot injection quantity on heat release rate and in-cylinder pressure (θpilot = −19 deg ATDC, θpost = 12 deg ATDC, qpost = 2 mm3)

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Fig. 6

Effects of pilot injection quantity and timing on smoke emission and performance (qpost = 2 mm3)

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Fig. 7

Effects of pilot injection timing on heat release rate and in-cylinder pressure (qpilot = 4 mm3, θpost = 12 deg ATDC, qpost = 2 mm3)

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Fig. 9

Smoke emission against post injection timing for qpilot = 2, 4, 6 mm3 (θpilot = −19 deg ATDC, qpost = 2 mm3)

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Fig. 10

Smoke emission against post injection quantity for qpilot = 2, 4, 6 mm3 (θpilot = −19 deg ATDC, θpost = 12 deg ATDC)

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Fig. 11

Smoke emission against pilot-injection timing (qpilot = 6 mm3, θpost = 12 deg ATDC, qpost = 2 mm3)

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Fig. 12

Smoke emission against pilot-injection timing (qpilot = 4 mm3, θpost = 12 deg ATDC, qpost = 3 mm3)

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Fig. 13

Effects of pilot injection timing on heat release rate and in-cylinder pressure (qpilot = 6 mm3, θpost = 12 deg ATDC, qpost = 2 mm3)

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Fig. 14

Effects of pilot injection quantity on heat release rate and in-cylinder pressure (qpilot = 4 mm3, θpost = 12 deg ATDC, qpost = 3 mm3)

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Fig. 15

Effects of injection pressure on smoke emission and performance (qpilot = 2 mm3, θpilot = −19 deg ATDC, qpost = 2 mm3)

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Fig. 16

Effects of injection pressure on smoke emission and performance (qpilot = 6 mm3, θpilot = −19 deg ATDC, qpost = 2 mm3)

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Fig. 17

Effects of injection pressure on heat-release rate, and in-cylinder pressure (θpilot = −19 deg ATDC, θpost = 12 deg ATDC, qpost = 2 mm3)

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Fig. 18

Effect of injection pressure on smoke emission against post injection timing for qpilot = 2, 6 mm3 (θpilot = −19 deg ATDC, qpost = 2 mm3)

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