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Numerical methodology for evaluation the combustion and emissions characteristics of WLTP in the European light duty dual-fuel vehicle diesel engines

The aim of reducing primary harmful emissions (HC, CO, PM and NOx) from internal combustion engines (ICE) bring more and more stringent emission regulations. In July 2017 the Worldwide Harmonized Light Vehicles Test Procedure (WLTP) has been adopted as the new test procedure in the European type-approval (TA) system and replaces the New European Driving Cycle (NEDC). The WLTP includes several test cycles applicable to vehicle categories of different rated power (W) to curb mass ratio (kg). Test cycles contains vehicle speed vs time profiles and directly on the engine test bench cannot be used. In order to back calculate engine rpm and torque based on the velocity of the vehicle used longitudinal vehicle dynamics method. Longitudinal dynamics approach is a low time consumption method that makes use of as limited information as possible referring mainly to already available data sources and using empirical models while allows to, provide simulation with required accuracy. A commercial direct injection diesel engine AJM 1.9 TID is used in this study, made by Volkswagen, which is a four stroke, four-cylinder, water-cooled, turbocharged diesel engine. Engine was adopted to work under dual fuel mode (diesel fuel and LPG). In this operation mode LPG in gaseous form inducted directly into the inlet manifold to form homogeneous mixtures with intake air. Next, this fuel mixture ignited by the directly injected pilot quantity of diesel fuel in the cylinder at the end of the compression stroke. Dual fuel mode is a proven solution that allows slightly reduce harmful compounds in exhaust gases. Moreover, dual fuel adaptation is inexpensive and requires minimum installation of additional components. The current work presents simple longitudinal dynamics approach in combination with WLTP gear-shifting rules and grid clustering method for assessing the introduction of Worldwide Harmonized test protocol in the European light duty dual fuel diesel vehicle (Golf IV). Combustion and emission characteristics of various diesel to LPG substitution ratios (LPG-10%, LPG-20%, LPG-30%) in the most representative operation points of WLTP for selected diesel engine are evaluated in this paper.
Topic: Fuel injection systems and mixture formation
Author: Denys Stepanenko
Co-authors: Zbigniew Kneba Jacek Rudnicki