Search Results

This paper describes the development and characterization of a selective catalytic reduction (SCR) catalyst system for a typical EUIV heavy-duty diesel (HDD) engine. The performance of the SCR catalyst and the impact of catalyst volume are described. The effect of using an ammonia slip catalyst behind the SCR catalyst is investigated, before examples of the use of computer modelling to refine the optimum volume and urea injection strategy are given. Finally, the durability of the SCR catalyst is described. Taken as a whole, the results demonstrate how a combination of practical experiments and computer modelling can be used to refine the system and provide a cost-effective exhaust aftertreatment (EA) solution.

This paper describes the development and characterization of a Selective Catalytic Reduction (SCR) catalyst system for EUIV (HDD) engines. The performance of the SCR catalyst and the impact of catalyst volume are described. The effect of using an ammonia slip catalyst behind the SCR catalyst is investigated. The durability of the SCR catalyst is described. Finally, examples of the use of computer modelling to refine the optimum volume and urea injection strategy are given. The results demonstrate how a combination of practical experiments and computer modelling can be used to refine the system and provide a cost-effective exhaust aftertreatment solution.

The influence of physical parameters of the catalyst's substrate such as thermal mass, hydraulic diameter and geometric surface area on catalyst's efficiency is well known as published in numerous works. This paper will show interactions of these parameters and will provide a guideline on how to design the optimum system for a specific application, taking into account system's back pressure and system costs. Based on engine test bench results that show the influence of the physical parameters, the results for the optimized design regarding emission tests and maximum conversion rate at higher loads will be demonstrated.

This paper compares and discusses the impact of conventional and improved start strategies on the design of the exhaust aftertreatment system. It is recognised that hardware measures on the exhaust side will not be sufficient if Volvo's 5 and 6 cylinder engines are to fulfil SULEV emission levels, assuming passive three way systems only. A new start strategy, providing an excessive heat profile combined with low engine out hydrocarbon emissions, was therefore developed. Temperature profiles, raw emissions and mass flow obtained with the Lean Start Calibration will be shown for the 5 and 6 cylinder engines, both naturally aspirated as turbo. The remaining part of the paper presents a brief history of the exhaust aftertreatment design modifications for Volvo's 5 cylinder N/A engine fulfilling LEV, ULEV I, ULEV II and PZEV emission levels respectively. The impact of the new start strategy on the cold start performance will be shown.

The catalytic converter on a European diesel car must operate under extremely variable conditions, ranging from very low temperature during city-driving to high temperature during Autobahn-driving. Therefore, the development of new catalyst technology for European applications requires simultaneous achievement of properties that have long been considered incompatible. In this paper, it is shown how extremely good low temperature activity for CO and hydrocarbons (and VOF), negligible storage of sulfates, and very good thermal durability were obtained simultaneously with an appreciable reduction of NOx. Through the systematic analysis of basic catalytic phenomena, under conditions of relevance to the real-world application, it was possible to control the interaction between support, stabilizers and promoters with the precious metal package in an efficient way. The large-scale manufacturing aspects formed an important part of the development program.

The new SULEV legislation for passenger cars with gasoline powered engines, which will be introduced with the California LEV II program in the year 2003, requires a further development of the exhaust aftertreatment system. Three fundamentally different system approaches, each with very high efficiency in reducing cold start hydrocarbons, will be discussed in this paper. Vehicle test results will be presented to illustrate the potential of the respective systems towards the SULEV requirements. Durability aspects are also considered since an increased durability of 120 000 and even 150 000 miles is imposed by the legislation.