Development Of Combustion System Of WP10 Diesel Engine With 2-Valve Per Cylinder Meeting Demand Of Chinese III & IV Standard

With the increasingly stringent exhaust emission standards of the diesel engine as well as the development of the diesel engine technology, it is very imperative for China to design a diesel engine that can meet Chinese Phase III and IV standard. This study aims to develop this type diesel engine using advanced combustion and exhaust gas after-treatment technologies on the basis of existing diesel engine with 2-valve per cylinder. More and more extraordinary development efforts have been required by improved combustion processes and tailpipe emissions by new exhaust gas after-treatment systems.This investigation was conducted on a current production turbocharged, inter-cooled, Model WD615 diesel engine manufactured by Weichai Power Co. Ltd., which fulfill Phase II emissions standard. This study is concentrated on two basic problems. The first part deals with the diesel engine to meet Phase III, which equipped with the second generation of the Bosch common rail system (Model EDC-7) with some optimized engine parameters. The second part deals with the optimized engine using a selective catalytic reduction (SCR) system to meet Phase IV. On the new development engine basis, the further developed diesel engine retrofitted by SCR system controlled by the Bosch DeNOx2 can meet Phase IV emission requirements in China.The basic approach to the research, according to the mentioned objectives (two parts), can be noted as follows:1. The advantages and disadvantages of different electronic control systems have been discussed and the Bosch common rail system was retrofitted onto the Model WP10 diesel engine. The characteristics investigation related with combustion process of the electronically controlled injector have been performed on the high pressure common rail test bench.2. The essential parameters of the combustion system, including piston rings, combustion chamber shape, injection system and turbocharger have been optimized for the base engine WD615. The aim was to achieve low lubricant oil consumption and low particulate matter (PM) emissions through improving intake flow characteristics. Finally, the optimized design parameters are determined. 3. On the basis of the optimized parameters, the effects of different injection pressure, ignition timing and multiple injections have been investigated to evaluate thermodynamic performance by heat release analysis. The test results provide a theoretical basis to support the lower exhaust emissions and improved engine performance.4. The control strategies for high pressure common rail have been carefully considered to optimize fuel injection pressure, injection timing, pilot injection and post injection. To fulfill Phase III emission standard, the test engine was completely developed and calibrated. The results obtained for regulated emissions are illustrated below with Phase III emissions limits in brackets. NOx=4.80(5.0)g/kW.h, PM=0.08(0.10)g/kW.h, CO=0.45(2.1)g/kW.h, HC=0.30(0.66)g/kW.h and smoke opacity with ELR(European Load Response Test)=0.46(0.8)m-1, which are below the Phase III limits.5. The effects of the SCR system on NOx reduction was carried out on Model WP10 diesel engine. To optimize the SCR system, steady conditions of temperature, injection amount of Urea and calibration for steady and transient operating conditions have been investigated. The detailed result data from the test engine operating with (European Steady State Cycle) ESC and ETC (European Transient Cycle) test cycle are shown as follows, respectively. For ESC cycle: NOx=2.91(3.5)g/kW.h, PM=0.014(0.02)g/kW.h, CO=0.38(1.5)g/kW.h, HC=0.054(0.46)g/kW.h and smoke opacity with ELR=0.042(0.5)m-1. For ETC cycle: NOx=2.83(3.5)g/kW.h, PM=0.017(0.03)g/kW.h, CO=0.094(4.0)g/kW.h, HC=0.129(0.55)g/kW.h. The test results measured in regulated emission meet Phase IV emission standard.