Modelling NOx Reduction by Selective Catalytic Reduction (SCR) appropriate for Light-Duty Vehicles under Steady State and Transient Conditions

Funder

Engineering and Physical Sciences Research Council
EP/F036175/1 Research Grant

Total value of project

£323,882

Project team

Professor S Benjamin, Dr C A Roberts

Partners

Jaguar Land Rover Ltd, United Kingdom; EMCON Technologies Germany (Augsburg) GmbH, Germany; Johnson Matthey, United Kingdom

Duration of project

01/09/2008 - 28/02/2012

Project overview

Diesel engines offer the prospect of reducing emissions of carbon dioxide as they are inherently more thermodynamically efficient than petrol engines. However diesels produce higher emissions of nitrogen oxides (NOx) the reduction of which is more challenging. Selective Catalytic Reduction (SCR) is an efficient technology for NOx reduction however its  application to light-duty vehicles and passenger cars is challenging due to their operational characteristics.

This project was focused on development and validation of a mathematical model of an SCR system to facilitate the design of these light duty systems, and thus save development time and costs whilst also providing systems with reduced emissions and better fuel economy.

The project combined experimental work with modelling. The experiments involved measurements made in a modular SCR test exhaust on a Diesel engine rig. By varying inlet NOx concentration, flow velocity, and urea injector location, a set of comprehensive data was obtained for validation of the model. While most of the data published up to date was collected from laboratory reactor studies using synthetic exhausts at low space velocities, the  experimental data set obtained during this project provided a unique insight into the mechanisms of urea droplet distribution and evaporation in application-relevant conditions.

A new approach for the urea spray modelling has been developed along with the porous medium approach to predict NOx conversion to compare with measurements. The model can predict urea droplet evaporation and conversion into ammonia and HCNO, and can be directly applied by the industrial partners. 

Project objectives

The main aim of the project was the development and validation of an engineering design tool for modelling selective catalytic reduction (SCR) on a diesel after-treatment system under steady state and transient conditions.

• Impact statement

  This project brought together several partners in a bid to improve NOx emission reduction by creating new modelling tools for Selective Catalyst Reduction (SCR). Such models allow design engineers to vary operating parameters and system design features prior to prototype testing, and thus to save development time and costs whilst also providing systems with reduced emissions and better fuel economy. The societal benefits will be a reduction toxic pollution and greenhouse gases.

  The project has resulted in the award of 3 PhDs, seven peer-reviewed publications, 14 confidential reports and lead (directly or indirectly) to a number of other collaborative projects with Jaguar Land Rover, Johnson Matthey, Horiba UK, as well as our group's participation in the Low Carbon Vehicle Technology Project (LCVTP).

• Outputs

  Tamaldin N. , Roberts C. A., Benjamin S. F. (2010) Experimental study of SCR in a light-duty diesel exhaust to provide data for validation of a CFD model using the porous medium approach. SAE World Congress paper No 2010-01-1177, April 13-15 2010, Detroit USA. (also in Diesel Exhaust Emission Control, 2010, SP-2287 Published: 2010-04-13).

  Sturgess M. P, Benjamin S. F. and Roberts C. A. (2010) Spatial conversion profiles within an SCR in a test exhaust system with injection of ammonia gas modelled in CFD using the porous medium approach. 10FFL-0030. SAE 2010 Powertrains Fuels and Lubricants Meeting, San Diego, Ca, paper No SAE 2010-01-2089.

  S. F. Benjamin, M. Gall, M. P. Sturgess & C. A. Roberts (2011) Experiments on a light duty SCR test exhaust system using ammonia gas to provide data for validation of a CFD model. IMechE Conference Internal Combustion Engines: Performance, Fuel Economy and Emissions: 29-30 November 2011, London UK, Paper C1328/009, pp219- 234. ISBN 978-0-85709-205-2 (print), ISBN 978-0-85709-506-0 (online).

  S. F. Benjamin and C. A. Roberts (2012) Significance of droplet size when injecting aqueous urea into a Selective Catalytic Reduction after-treatment system in a light-duty Diesel exhaust. IMechE Conference C1342 Fuel Systems for IC Engines 14-15 March 2012 , Woodhead Publishing ISBN 978-0-85709-210-6 pp 43-60.

  S. F. Benjamin, M. Gall and C. A. Roberts (2012) Modelling of NOx conversion in a 1D Diesel engine exhaust SCR catalyst system under transient conditions using ammonia gas as the reductant. Paper, SAE 2012 Powertrains, Fuels & Lubricants Meeting, 18-20 Sept 2012, Malmo, Sweden.

  S. F. Benjamin, M. Gall and C. A. Roberts (2012) Tuning the standard SCR reaction kinetics to model NO conversion in a Diesel engine exhaust SCR catalyst system under steady state conditions in 1D and 3D geometries using ammonia gas as the reductant. Paper, SAE 2012 Powertrains, Fuels & Lubricants Meeting, 18-20 Sept 2012, Malmo, Sweden.

  S. F. Benjamin, M. Gall and C. A. Roberts (2014) Conversion of nitric oxide in an engine exhaust  by selective catalytic reduction with a urea spray under steady-state and transient engine-load conditions. Proc IMech Eng Part D J Automobile Engineering Vol. 228(7) 758-770.

  N Tamaldin (2010) Experimental Investigation of Emission from a Light Duty Diesel Engine Utilizing Urea Spray SCR system. PhD thesis, Coventry University.

  M P Sturgess (2012) Selective Catalytic Reduction for ‘Light-Duty’ Diesel Engines using Ammonia Gas. PhD thesis, Coventry University.

  M Gall (2015) Study of SCR using Cu-Zeolite catalysts on a light-duty diesel engine under steady state and transient conditions. PhD thesis, Coventry University.

  Fourteen confidential reports.