Numerical investigation on the effects of valve timing on in-cylinder flow, combustion and emission performance of a diesel ignition natural gas engine through computational fluid dynamics

Abstract In the present study, a diesel engine was modified to a diesel pilot ignited natural gas engine and the influences of intake valve closing timing on in-cylinder flow, combustion and emission performance of engine were investigated by three-dimensional computational fluid dynamics simulation. Based on the geometric model and basic parameters of this engine, the simulation model was built under three operating conditions and then validated by experimental data. On this basis, the validated model was applied to investigate the effects of the intake valve closing timing strategy. The simulation results indicated that, the volumetric efficiency decreases with the retarding of intake valve closing timing in three cases while it increases as the intake valve closing timing is advanced by 10°CA at 1200 rpm. The in-cylinder turbulence kinetic energy decreases with the retarding of intake valve closing timing. The peak in-cylinder pressure decreases when the intake valve closing timing is either advanced or retarded at 50% load. Nevertheless, the maximum peak in-cylinder pressure occurs at advancing 10°CA intake valve closing timing at 1200 rpm and 100% load, which rises by 4.5 bar compared with that at the original intake valve closing timing. Additionally, the maximum heat release rate appears at advancing 10°CA intake valve closing timing at 100% load, which is 26 J/deg higher than that at the original intake valve closing timing. Simultaneously, the shortest combustion duration occurs at advancing 10°CA intake valve closing timing at 1200 rpm and 100% load. For the emissions, the NOx emissions decrease with the retarding of intake valve closing timing but the variation becomes unobvious with the advancing of the intake valve closing timing. Besides, the intake valve closing timing strategy has little effect on HC and CO emissions.

[1]  Samad Jafarmadar,et al.  Multidimensional modeling of the effect of Exhaust Gas Recirculation (EGR) on exergy terms in an HCCI engine fueled with a mixture of natural gas and diesel , 2015 .

[3]  J. E,et al.  Effects of low-level water addition on spray, combustion and emission characteristics of a medium speed diesel engine fueled with biodiesel fuel , 2019, Fuel.

[4]  Banglin Deng,et al.  The effect of air/fuel ratio on the CO and NOx emissions for a twin-spark motorcycle gasoline engine under wide range of operating conditions , 2019, Energy.

[5]  Rolf D. Reitz,et al.  Review of high efficiency and clean reactivity controlled compression ignition (RCCI) combustion in internal combustion engines , 2015 .

[6]  Ming Jia,et al.  The effect of injection timing and intake valve close timing on performance and emissions of diesel PCCI engine with a full engine cycle CFD simulation , 2011 .

[7]  Dan Zhao,et al.  RANS investigation of the effect of pulsed fuel injection on scramjet HyShot II engine , 2019, Aerospace Science and Technology.

[8]  Christopher J. Rutland,et al.  A new droplet collision algorithm , 2000 .

[9]  M. Birouk,et al.  Effect of swirl ratio on NG/diesel dual-fuel combustion at low to high engine load conditions , 2018, Applied Energy.

[10]  Miroslaw L. Wyszynski,et al.  A modelling study into the effects of variable valve timing on the gas exchange process and performance of a 4-valve DI homogeneous charge compression ignition (HCCI) engine , 2009 .

[11]  Jingping Liu,et al.  Experimental and computational study on the effects of injection timing on thermodynamics, combustion and emission characteristics of a natural gas (NG)-diesel dual fuel engine at low speed and low load , 2018 .

[12]  Yuze Sun,et al.  Experimental characterizing combustion emissions and thermodynamic properties of a thermoacoustic swirl combustor , 2019, Applied Energy.

[13]  Rolf D. Reitz,et al.  Modeling Diesel Engine NOx and Soot Reduction with Optimized Two-Stage Combustion , 2006 .

[14]  L. Pillier,et al.  NO prediction in natural gas flames using GDF-Kin®3.0 mechanism NCN and HCN contribution to prompt-NO formation , 2006 .

[15]  R. Reitz,et al.  Turbulence Modeling of Internal Combustion Engines Using RNG κ-ε Models , 1995 .

[16]  William J. Pitz,et al.  An Approach for Formulating Surrogates for Gasoline with Application toward a Reduced Surrogate Mechanism for CFD Engine Modeling , 2011 .

[17]  Rolf D. Reitz,et al.  Modeling Diesel Engine Spray Vaporization and Combustion , 1992 .

[18]  Hewu Wang,et al.  Effects of pilot fuel quantity on the emissions characteristics of a CNG/diesel dual fuel engine with optimized pilot injection timing , 2013 .

[19]  John B. Heywood,et al.  Internal combustion engine fundamentals , 1988 .

[20]  Wei Chen,et al.  Numerical investigation of direct injection stratified charge combustion in a natural gas-diesel rotary engine , 2019, Applied Energy.

[21]  J. Hunicz,et al.  Investigation of the thermal effects of fuel injection into retained residuals in HCCI engine , 2018, Applied Energy.

[22]  Zhanghua Wu,et al.  Performance analysis of a novel SOFC-HCCI engine hybrid system coupled with metal hydride reactor for H2 addition by waste heat recovery , 2019, Energy Conversion and Management.

[23]  Carlo Beatrice,et al.  Effects on performances, emissions and particle size distributions of a dual fuel (methane-diesel) light-duty engine varying the compression ratio , 2017 .

[24]  C. Bae,et al.  Intake air strategy for low HC and CO emissions in dual-fuel (CNG-diesel) premixed charge compression ignition engine , 2018, Applied Energy.

[25]  Jingping Liu,et al.  Effects of injector spray angle on combustion and emissions characteristics of a natural gas (NG)-diesel dual fuel engine based on CFD coupled with reduced chemical kinetic model , 2019, Applied Energy.

[26]  Maciej Mikulski,et al.  Understanding the role of low reactivity fuel stratification in a dual fuel RCCI engine – A simulation study , 2017 .

[27]  S. C. Hill,et al.  Modeling of nitrogen oxides formation and destruction in combustion systems , 2000 .

[28]  E. Gutmark,et al.  A review of cavity-based trapped vortex, ultra-compact, high-g, inter-turbine combustors , 2018 .

[29]  Jingping Liu,et al.  Experimental investigation on the effects of compression ratio on in-cylinder combustion process and performance improvement of liquefied methane engine , 2017 .

[30]  Mingfa Yao,et al.  Experimental investigation of the effects of diesel fuel properties on combustion and emissions on a multi-cylinder heavy-duty diesel engine , 2018, Energy Conversion and Management.

[31]  Tianyou Wang,et al.  Potential of reactivity controlled compression ignition (RCCI) combustion coupled with variable valve timing (VVT) strategy for meeting Euro 6 emission regulations and high fuel efficiency in a heavy-duty diesel engine , 2018, Energy Conversion and Management.

[32]  Ujjwal K. Saha,et al.  Effect of engine parameters and type of gaseous fuel on the performance of dual-fuel gas diesel engines—A critical review , 2009 .

[33]  Luigi Teodosio,et al.  Impact of intake valve strategies on fuel consumption and knock tendency of a spark ignition engine , 2018 .

[34]  Yi Wang,et al.  Effect of asynchronous valve timing on combustion characteristic and performance of a high speed SI marine engine with five valves , 2016 .

[35]  M. Birouk,et al.  Investigation of natural gas energy fraction and injection timing on the performance and emissions of a dual-fuel engine with pre-combustion chamber under low engine load , 2017 .

[36]  A. A. Amsden,et al.  KIVA-II: A Computer Program for Chemically Reactive Flows with Sprays , 1989 .

[37]  M. Shahbakhti,et al.  Optimization of performance and operational cost for a dual mode diesel-natural gas RCCI and diesel combustion engine , 2018, Applied Energy.

[38]  R. Reitz,et al.  A reduced chemical kinetic model for IC engine combustion simulations with primary reference fuels , 2008 .

[39]  Jingping Liu,et al.  Influences of excess air coefficient on combustion and emission performance of diesel pilot ignition natural gas engine by coupling computational fluid dynamics with reduced chemical kinetic model , 2019, Energy Conversion and Management.

[40]  Jose J. Lopez,et al.  Evaluation of the Thermal NO formation mechanism under low-temperature diesel combustion conditions , 2012 .

[41]  Mahdi Shahbakhti,et al.  Modeling and controller design architecture for cycle-by-cycle combustion control of homogeneous charge compression ignition (HCCI) engines – A comprehensive review , 2017 .

[42]  F. Dryer,et al.  A comprehensive kinetic mechanism for CO, CH2O, and CH3OH combustion , 2007 .

[43]  T. Korakianitis,et al.  Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions , 2011 .

[44]  R. Lot,et al.  Valve timing optimisation of a spark ignition engine with skip cycle strategy , 2018, Energy Conversion and Management.

[45]  John Abraham,et al.  Modeling the outcome of drop–drop collisions in Diesel sprays , 2002 .

[46]  Yingjie Chen,et al.  Experimental and numerical study of multiple injection effects on combustion and emission characteristics of natural gas–diesel dual-fuel engine , 2019, Energy Conversion and Management.