Keishi Takada

Experimental study on unregulated emission characteristics of turbocharged di diesel engine with common rail fuel injection system

In this study, we selected four unregulated emissions species, formaldehyde, benzene, 1,3-butadiene and benzo[a]pyrene to research the emission characteristics of these unregulated components experimentally. The engine used was a water-cooled, 8-liter, 6-cylinder, 4-stroke-cycle, turbocharged Dl diesel engine with a common rail fuel injection system manufactured for the use of medium-duty trucks, and the fuel used was JIS second-class light gas oil, which is commercially available as diesel fuel. The results of experiments indicate as follows: formaldehyde tends to be emitted under the low load condition, while 1,3-butadiene is emitted at the low engine speed. This is believed to be because 1,3-butadiene decomposes in a short time, and the exhaust gas stays much longer in a cylinder under the low speed condition than under the high engine speed one. Benzene is emitted under the low load condition, as it is easily oxidized in high temperature. Benzo[a]pyrene exists in the gas phase, because its boiling point is about 750K (at 128kPa). Once gaseous benzo[a]pyrene condenses, it is trapped by a filter with soot or sulfate. If it stays in the high temperature area, large part of it is oxidized. Consequently, benzo[a]pyrene is not emitted in great quantity under the high load condition.

Development of an improved urea-selective catalytic reduction—diesel particulate filter system for heavy-duty commercial vehicles

Abstract Many heavy-duty commercial vehicles are now equipped with urea-selective catalytic reduction (SCR) systems, which can reduce NO x emissions sufficiently to meet the requirements of legislation such as Japans New Long-term Diesel Emissions Regulations. However, in order to meet even stricter exhaust emissions regulations (and fuel consumption standards) due to be imposed in many parts of the world in the near future, urea-SCR systems with greater catalytic efficiency combined with diesel particulate filters (DPFs) will be needed. Therefore, in the study presented here the scope for enhancing the efficiency of a urea-SCR system was explored by optimizing the urea dosing system and injection strategies, and the gas flow in the exhaust pipe. However, since improving the catalysis parameters could have the greatest overall effect on conversion efficiency, work focused on modifying the catalyst materials to increase their adsorption capacity for the NH3 reducing agent, and thus increase the collision frequency between NO x and NH3 absorbed on the surface of the catalyst. In addition, the oxidation parameters of the oxidation catalyst were optimized, which enhanced the NO x conversion efficiency of the system, not only in a steady cycle but also in a transient cycle. Following these adjustments, a DPF-plus-SCR system with the new catalytic material delivered 90 per cent conversions of NO x and particulate matter to N2 and CO2 respectively, in the JE05 test cycle. In addition, a new concept, a miniaturized ‘urea-SCR with DPF function system’ was proposed and tested, which delivered 90 per cent NO x conversion rates and 90 per cent reductions in particulate matter emissions in the JE05 test cycle.

A BASIC STUDY ON A UREA-SELECTIVE CATALYTIC REDUCTION SYSTEM FOR A MEDIUM-DUTY DIESEL ENGINE

Abstract NOx conversion performance of a urea-selective catalytic reduction (SCR) system comprising V2O5/TiO2 catalyst under steady state operating conditions of an 8-litre, common-rail turbo direct injection (TDI) diesel engine was investigated. It was shown that the urea-SCR system achieves 70–90 per cent NOx conversion under medium and high load conditions at 1440 r/min and that NOx conversion is low under low load conditions because of the low catalyst temperatures and the NO/NO2 ratio being higher than unity. It was also shown that NOx conversion exceeds 90 per cent when the catalyst temperature is higher than 530 K. To investigate the details of the chemistry and thermofluid dynamics within the urea-SCR system, a computational fluid dynamics (CFD) code that incorporates detailed surface chemistry was developed based on the modified subroutines of CHEMKIN-II. The spatial variations of chemical species including NO and NH3 in a thin catalyst channel was calculated using the model. The calculated result of NO conversion showed relatively good agreement with experimental results.