Simone Serra

Gaseous Emissions from Light-Duty Vehicles: Moving from NEDC to the New WLTP Test Procedure.

The Worldwide Harmonized Light Duty Test Procedure (WLTP), recently issued as GTR15 by UNECE-WP29, is designed to check the pollutant emission compliance of Light Duty Vehicles (LDVs) around the world and to establish the reference vehicle fuel consumption and CO2 performance. In the course of the development of WLTP, the Joint Research Center (JRC) of the European Commission has tested gaseous emissions of twenty-one Euro 4-6 gasoline and diesel vehicles, on both the current European type approval test procedure (NEDC) and the progressive versions of the WLTP. The results, which should be regarded just as an initial and qualitative indication of the trends, demonstrated minimal average differences between CO2 emissions over the NEDC and WLTP. On the other hand, CO2 emissions measured at JRC on the NEDC were on average 9% higher than the respective type approval values, therefore suggesting that for the tested vehicles, CO2 emissions over WLTP were almost 10% higher than the respective NEDC type approval values. That difference is likely to increase with application of the full WLTP test procedure. Measured THC emissions from most vehicles stayed below the legal emission limits and in general were lower under the WLTP compared to NEDC. Moving from NEDC to WLTP did not have much impact on NOx from gasoline vehicles and CO from diesel vehicles. On the contrary, NOx from diesel vehicles and CO from low-powered gasoline vehicles were significantly higher over the more dynamic WLTP and in several cases exceeded the emission limits. Results from this study can be considered indicative of emission patterns of modern technology vehicles and useful to both policy makers and vehicle manufacturers in developing future emission policy/technology strategies.

Gasoline partially premixed combustion: high efficiency, low NOx and low soot by using an advanced combustion strategy and a compression ignition engine

A light-duty engine Volvo D5 was run with gasoline to demonstrate that high-octane number fuels, in compression ignition engines, are able to achieve high effi ciency, low NOx and soot simultaneously. An advanced three stage injection strategy was developed. A load sweep was performed between 6 and 17 bar IMEP and 2000 rpm. Gross indicated effi ciency stays fairly constant at 47% with very low NOx and soot. In the second section of the paper, diesel was compared with gasoline, while in the fi nal part the commercial 140°UA nozzle was compared with the narrower one, 120°, used in the above-mentioned experiments.

Development of the Worldwide Harmonized Test Procedure for Light-Duty Vehicles: Pathway for Implementation in European Union Legislation

To assess vehicle performance on criteria compounds, carbon dioxide emissions, and fuel energy consumption, laboratory tests are generally carried out. During these tests, a vehicle is driven on a chassis dynamometer (which simulates the resistances the vehicle encounters during its motion) to follow a predefined test cycle. In addition, all conditions for running a test must strictly adhere to a predefined test procedure. The procedure is necessary to ensure that all tests are carried out in a comparable way, following the requirements set by the relevant legislation. Test results are used to assess vehicle compliance with emissions limits or to evaluate the fuel consumption that will be communicated to customers. Every region in the world follows its own approach in carrying out these types of tests. The variations in approaches have resulted in a series of drawbacks for vehicle manufacturers and regulating authorities, leading to a plethora of different conditions and results. As a step toward the harmonization of the test procedures, the United Nations Economic Commission for Europe launched a project in 2009 for the development of a worldwide harmonized light-duty test procedure (WLTP), including a new test cycle. The objective of the study reported here was to provide a brief description of WLTP and outline the plausible pathway for its introduction in European legislation.

Injection system assessment to optimize performance and emissions of a non - road heavy duty diesel engine : experiments and CFD modelling

The advancing emissions requirements and the customer demand for increased performance and fuel efficiency are forcing the diesel engine technology to keep improving. In particular, the large diesel engines are undergoing to a significant restriction in emission standards. Reaching the new limits requires innovative solutions, improved calibration and controls of the engine combustion technology, as well as the optimization of the injection system that has experienced the most fundamental development over the last decade. The objective of the paper is to present preliminary results of an investigation for the development of an efficient combustion system for marine diesel engines. The effect of different engine parameters on performance and engine out emissions were evaluated. Specifically, different nozzle geometries, injection pressure, injection timings were taken into account. The investigation was carried out both experimentally and numerically. Three different nozzles geometries for three different values of the start of injection were tested. The in-cylinder pressure, rate of heat release, NOx and soot were evaluated for a high load engine condition. The experimental activity was carried out on a large displacement single cylinder direct injection diesel engine equipped with a high-pressure common rail injection system able to manage multiple injections. The engine test bench was equipped with an external air supercharger able to set high air boost levels. The system controls the intake air temperature by means of a heater exchanger. The numerical investigation was carried out using the commercial CFD STAR-CD code in a three-dimensional domain including the cylinder head and piston bowl. Combustion behaviour was simulated using the 3 Zones Extended Coherent Flame Model (ECFM3Z).