Wolfgang Cartellieri

Worldwide diesel emission standards, current experiences and future needs

Abstract The tightening of future exhaust emission limits for diesel engines and diesel vehicles require more and more extraordinary development efforts with respect to reducing both engine-out emissions by improved combustion processes and tailpipe emissions by new exhaust gas aftertreatment systems (EGAS). Today, the main EGAS activities in engine application as well as in research and development concentrates on oxidation catalysts, particulate traps, and DENOX catalysts. This paper deals with 1. a general overview on the development directions of different EGAS and typical emission reduction examples for various diesel engine and vehicle applications; 2. the interaction between legislative emission test cycles, combustion system development and the kind of EGAS used. Based on current development work and test results, ranking considerations with regard to the application and development probability of EGAS are given.

Fuel injection and Combustion Phenomena in a High Speed DI Diesel Engine Observed by Means of Endoscopic High Speed Photography

After a short description of the Endoscopic High Speed Combustion Photography Technique used, the results obtained through observation of the following phenomena in a 0.5 litre HSDI Diesel engine are presented: the wall jet development and the role of swirl, the effect of wall temperature (cold and warm engine) on combustion development, and the effect of pilot injection on mixture formation and combustion. To document these phenomena, typical high speed films are presented supplemented by cylinder pressure, injector needle lift, rate of heat release, and light radiation (flame luminosity) intensity data recorded simultaneously by means of a digital acquisition system.

Performance of a Urea SCR System Combined with a PM and Fuel Optimized Heavy-Duty Diesel Engine Able to Achieve the Euro V Emission Limits

In order to meet the Euro V heavy-duty diesel emission standard legislation limits, a diesel engine can be optimized by internal means to give low particulate emissions and lower fuel consumption. These modifications of the engine lead inevitably to higher NOx emissions due to the NOx/PM trade off. An efficient Urea SCR after-treatment system is then able to reduce the higher NOx emission to below the Euro V 2.0g/kWh legislation limit. This paper presents tests made on a PM optimized 12 liter heavy-duty diesel engine together with a urea SCR after-treatment system. The optimized engine had engine out particulate emissions of about 0.04 g/kWh and NOx emissions of 9 g/kWh for the ESC and 8,5 g/kWh for the ETC. The fuel consumption of the optimized engine was 194 g/kWh for the ESC and 198 g/kWh for the ETC as compared to state of the art Euro III engines of typically 210 g/kWh for the ESC, giving significant fuel savings of 7.5 %. Combining the engine with a 20 liter 300-cpsi SCR catalyst, catalyst volume to cylinder ratio of 1.7, the particulate emissions dropped to 0.017 g/kWh for the ESC and 0.020 for the ETC. Particle size measurements also showed a decrease in the number of fine particles. With a urea injection corresponding to about 8-9% of the fuel flow the NOx emissions were reduced to 1.4 g/kWh for the ESC and 1.5g/kWh for the ETC with low ammonia slip. These reductions correspond to a NOx conversion of 84 % and 82% for the ESC and ETC respectively. Thus the optimized engine combined with the urea SCR after-treatment system was compliant with the Euro V emission limits. INTRODUCTION In order to comply with the Euro V regulations for heavyduty diesel engines due in 2008, both the NOx and particulate emissions must be greatly reduced for today’s state of the art diesel engines. The regulations of 2008, namely 2.0 g/kWh NOx and 0.02 g/kWh particulates for the ESC and 0.03 g/kWh for the ETC driving cycles, cannot be achieved solely by engine management or improved engines, rather some sort of aftertreatment must be used. A preferred solution to comply with the Euro V emission limits is to optimize a diesel engine by internal means to give very low particulate emissions and considerably lower fuel consumption [1]. Due to the NOx/PM trade-off for diesel engines this will lead to higher NOx emissions, from Euro III levels of 5-6 g/kWh to 8-10 g/kWh, that have to be reduced with an efficient NOx aftertreatment system below the 2.0 g/kWh limit, preferably Urea-SCR. The Urea SCR systems have been shown to be both very efficient and durable in vehicle applications [2,3,4,5,6]. The higher NOx emission of the optimized engine therefore requires the Urea SCR system to have a high NOx conversion efficiency of about 80-85%. The combination of the optimized engine and Urea SCR system eliminates the need for a particulate filter to comply with Euro V emissions leading to a lower pressure drop of the exhaust system and also less complexity of the total system. Furthermore the significant fuel savings of the optimized engine compared to a standard Euro III engine could give a payback time for the optimized engine and the SCR system depending on the urea price and the application as to make the concept commercially interesting even prior to the legislation limits. This concept could also be a serious candidate for the Euro IV legislation (NOx limit of 3.5 g/kWh and particulates the same as Euro V). The optimized engine and SCR concept has an even greater fuel saving compared to a concept of a standard Euro III engine with EGR and particulate filter. EGR increases the fuel consumption of the engine and the addition of the particulate trap increases the fuel consumption further by increasing the pressure drop giving the combination of the optimized engine and Urea SCR system an even greater fuel consumption advantage. The purpose of this work was to demonstrate a PM and fuel optimized heavy-duty diesel engine and Urea SCR concept able to comply with the Euro V legislation emission limits. The total work consisted of 3 parts: • SCR catalyst optimization and selection [7] • Engine optimization • Combination of the optimized engine with the chosen SCR system. In previous work the catalyst selection to achieve a high NOx conversion above 80% with ammonia slip less than 10 ppm and development of a novel Urea SCR injection system were discussed [7]. This present paper deals with the optimization work on the engine, performance of the optimized engine, final selection of catalyst and the performance of the combination of the PM and fuel optimized engine with the efficient Urea-SCR system. The optimization targets of the engine optimization were to achieve low soot emissions (i.e. carbon particulates less than 0.010/0.015 g/kWh in ESC/ETC test) by internal means while maintaining very low fuel consumption at engine-out NOx emissions of 8 to 10 g/kWh in the ESC test.

Status report on a preliminary survey of strategies to meet US-1991 HD diesel emission standards without exhaust gas aftertreatment

This paper presents a status report on a preliminary survey of strategies that might be employed to meet US-EPA 1991 heavy duty diesel emission standards without the use of a particulate trap. Although the survey of strategies is not yet complete, that portion dealing with the swirl supported diesel combustion process is sufficiently advanced to allow this status report to be published. It is anticipated that future related reports will provide a view of the complete survey, including quiescent combustion process. This report describes the techniques employed for the steady state approximation of the heavy duty transient test cycle and the analytical procedures used to characterize the particulate composition in terms of insolubles, and the fuel and lube oil related components.