Journal of Mechanical Science and Technology 30 (9) (2016) 4373~4382 www.springerlink.com/content/1738-494x(Print)/1976-3824(Online) DOI 10.1007/s12206-016-0851-9 Design of combustion bowl geometry to meet final Tier 4 of 11 L non-road heavy-duty diesel engine with multi-dimensional combustion simulation † Sangyul Lee, Jongyoon Lee * , Seungkwon Hwang, Taejoong Wang and Youngbok Lee Combustion Design Part, Doosan Infracore, Inchoen 401-702, Korea (Manuscript Received December 31, 2015; Revised March 3, 2016; Accepted April 27, 2016) ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract To comply with the new non-road emission standards, final Tier 4, two big strategies have been applied to the 11 L heavy-duty diesel engine. The first strategy is to apply Exhaust gas recirculation and selectivity catalytic reduction system to meet the NOx limitation. The other one is to apply low swirl ratio (for higher volumetric efficiency) and multi-hole nozzle, a high pressure direct injection, and an op- timized combustion system in order to reduce PM emission. Both strategies put a focus on the optimization of combustion system. In this study, a ULPC bowl concept applied in the previous works has been successfully verified in 11 L heavy-duty diesel engine with well- validated 3D combustion simulation, and the ULPC bowl shape has been geometrically optimized. A rough 0D calculation is used to calculate the fuel split ratio of the various ULPC bowl shapes. In the rated-power operating condition of the final Tier 4 engine which is deduced by 1D cyclic simulation, the optimal fuel split ratio of the injected fuel has been verified. Also, additional geometric optimiza- tion has been achieved without changing the optimal fuel split ratio. From these results, soot has been reduced by about 30% with ULPC optimum bowl shape against the Tier 3 re-entrant bowl shape. Keywords: Combustion bowl shape; Diesel engine; Non-road heavy duty diesel engine; PM; Soot; ULPC; Tier 4 ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 1. Introduction The emission standards for non-road heavy-duty diesel en- gine are gradually getting stringent as concerns about envi- ronmental issues are growing more across the globe. There- fore, engine manufacturers must meet stringent emission stan- dards and satisfy market’s buying factors such as fuel econ- omy, specific power, and cost, at the same time. To have a competitive advantage, development strategies and plans of engine manufacturers are mainly focused on fuel economy, specific power and cost. The efficiency of diesel engines de- pends largely on combustion process. This process occurs in a combustion chamber in a very short period of time, and the mixing of fuel and air in-cylinder is significantly important to improve engine efficiency and emissions reduction. Thus, many researches have been conducted about combustion pa- rameters, and the bowl shape optimization is one of the com- bustion parameters which can increase engine efficiency and reduce emissions. Originally the base engine was a non-road Tier 2 emission standards compliant engine. In order to meet non-road Tier 3 emission standards, the base engine was equipped with cooled-EGR (Exhaust gas recirculation) system. Final Tier 4, the latest non-road engine emission standards, however, is getting more stringent. The emission standards for the non- road engines are listed in Table 1 [1]. As shown in Table 1, 90% reduction of PM (Particulate matters) and NOx emis- sions are required for the base engine to meet Tier 4 final emission standards. A cooled-EGR system and a SCR (Selec- tive catalytic reduction) system are applied to reduce NOx emissions. A DPF (Diesel particulate filter) system is a possi- ble solution for PM reduction, and many engine manufactur- ers are actually using it these days. However, a DPF system has a bad effect on the usability of engine due to its regenera- tion process. A DPF system is expensive and requires large space for packaging. Fuel blending technology is also a possi- ble solution to reduce PM emissions [2], but it is not used globally yet. Another possible solution for PM reduction is to achieve optimization of combustion parameters. Many re- searches on optimization of piston bowl shape in combustion parameters have been conducted. Yoo et al. and Lee et al. showed that ULPC (Ultra-low PM combustion) type bowl shape design can largely reduce PM without a DPF [3, 4]. Elimination of a DPF system is very profitable because it is more expensive than an engine piston. The purpose of ULPC bowl shape design is to enhance air utilization. The main op- erating condition of heavy-duty engine is high load at rated * Corresponding author. Tel.: +82 32 211 8927, Fax.: +82 32 211 8520 E-mail address: jongyoon2.lee@doosan.com † Recommended by Associate Editor Jeong Park © KSME & Springer 2016