Abstract
This article presents test results achieved under World Harmonized Transient Driving Cycle (WHTC) run on heavy-duty diesel engine compliant with Euro VI standard. The emission cycle was performed both for cold and hot engine start up conditions. Modal analysis of emission compounds was carried out with the focus on nitro-gen oxides (NOx) emission. The scope of the work was to assess the influence of cold start effect on selective catalytic reduction (SCR) system operation efficiency. Due to the fact that the urea injection strategy in SCR system can by activated only after certain exhaust gas temperature threshold is achieved, the NOx emission on WHTC cold start cycle is significantly greater than for the hot start one. Result analysis included also determination of time period needed for achieving the readiness of SCR system to work efficiently. The occurrence of ammonia slip emissions downstream SCR was also monitored.
Highlights
Current legislative emission limits of passenger and heavy duty vehicles further tighten requirements of emitted nitro-gen oxides (NOx)
Improving the vehicle fuel economy that basically means decreasing of CO2 emission, is a real technical challenge when it comes to simultaneous reduction of NOx emissions to meet tight legislative limits
A major challenge in the development was the control of cold start NOx emissions, making thermal management strategies a key component of the project
Summary
Current legislative emission limits of passenger and heavy duty vehicles further tighten requirements of emitted NOx. On the other hand the World Harmonized Heavy Duty Certification Procedure minimalizes the meaning of cold start emission. This procedure incorporates world harmonized steady-state test cycle (WHSC) and transient cold and hot test cycles (WHTC). The heavy duty engines after-treatment systems (ATS) do not focus on cold start emissions as much as of light vehicles. This, as all catalyst-based cleaning up devices, starts to work effectively only when proper level of exhaust temperature is achieved. This technology meets legislation limits of Euro VI ensuring low NOx emission for rare cold start engine operation. The investigation of engine out and tailpipe NOx concertation traces clearly outlines engine operation periods practically without NOx aftertreatment
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