Internal Combustion Engines

Particle Number Emissions of Nonroad Diesel Engines of Various Ages

[+] Author and Article Information
Seppo Niemi

 University of Vaasa, P.O. Box 700, FIN-65101, Vaasa, FinlandSeppo.niemi@turkuamk.fi Turku University of Applied Sciences, Turku, FinlandSeppo.niemi@turkuamk.fi

Krister Ekman, Pekka Nousiainen

 University of Vaasa, P.O. Box 700, FIN-65101, Vaasa, Finland Turku University of Applied Sciences, Turku, Finland

J. Eng. Gas Turbines Power 134(9), 092807 (Jul 23, 2012) (11 pages) doi:10.1115/1.4006977 History: Received May 18, 2012; Revised June 01, 2012; Published July 23, 2012; Online July 23, 2012

Over the last two decades, gaseous and particle mass emissions of new diesel engines have been reduced effectively and progressively in response to the emissions legislation and due to the applied new technologies. There is, however, increasing concern about whether the engine modifications, while improving combustion and reducing emissions, have increased the number emissions of ultrafine and nanoparticles. So far, emissions regulations have solely been based on particulate matter (PM) mass measurements, not on particle number. Nanoparticles, however, form a major part of the PM emissions, but they do not considerably contribute to the PM mass and cannot be seen as a problem, if only PM mass is determined. Therefore, there is increasing interest in expanding the scope of the regulations to also include particle number emissions, e.g., Euro VI for on-road engines. The PM number limit will also be enforced for nonroad engines slightly later. Thus, more information is required about the particle number emissions themselves, but also about the effects of the engine technology on them. Wall-flow diesel particulate filters reduce the particle number very effectively within the entire particle size range. Nevertheless, in order to keep the filter as small as possible and to lessen the need for regeneration, the engine-out PM number should also be minimized. If the diesel particulate filters (DPFs) could be left out or replaced by a simpler filter, there would be greater freedom of space utilization or cost savings in many nonroad applications. This might be realized in installations where the engine is tuned at high raw NOx and a selective catalytic reduction (SCR) system is adopted for NOx reduction. However, it is not self-evident that new engine technologies would reduce the PM number emissions sufficiently. In this study, particle number emissions were analyzed in several nonroad diesel engines, representing different engine generations and exploiting different emissions reduction technologies: four- or two-valve heads, exhaust gas recirculation, different injection pressures and strategies, etc. All engines were turbocharged, intercooled, direct-injection nonroad diesel engines. Most engines used common-rail fuel injection technology. Comparisons were, however, also performed with engines utilizing either a distributor-type or an in-line fuel injection pump to see the long-term development of the particle number emissions. In this paper, the PM number emissions of nine nonroad diesel engines are presented and compared. Gaseous exhaust emissions and fuel consumption figures are also provided.

Copyright © 2012 by American Society of Mechanical Engineers
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Figure 1

Brake mean effective pressures and relative air-fuel ratios of the engines at full loads at rated (Mode 1) and intermediate speeds (Mode 5)

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Figure 2

Brake-specific fuel consumption values of various engines at different modes of the ISO 8178 C1 cycle. Mode 4 omitted due to its elevated BSFC (low load). For clarity, D given as a dash line.

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Figure 3

Eight-mode cycle-weighed NMHC + NOx emissions of various engines

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Figure 4

Exhaust smoke of the studied engines at different load points of the eight-mode ISO 8178 C1 test cycle

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Figure 5

Brake-specific particle number (BSPM) emissions at full load at rated speed

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Figure 6

BSPM emissions at half load at rated speed

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Figure 7

Particle number emissions at 10% load at rated speed

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Figure 8

Particle size distributions at full load at intermediate speed

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Figure 9

BSPM emissions at half load at intermediate speed

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Figure 10

Relative injection pressures of the studied engines at different loads; value 1 given for the highest injection pressure of the studied engines

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Figure 11

Ultrafine and total measured particle numbers versus relative injection pressure at Mode 3

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Figure 12

Effect of relative injection pressure on the sum of ultrafine and total particle numbers at Mode 5

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Figure 13

Share of ultrafine particles of the total measured PM number at two loads

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Figure 14

Brake-specific HC emissions of the studied test engines at Modes 1, 3, 4, 5, and 7

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Figure 15

The ratio of brake-specific HC and CO emissions of most of the studied engines at Modes 1, 3–5, and 7

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Figure 16

PM–NOx trade-off at Mode 3; the D engine omitted




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