Effects of application of variable valve timing on the exhaust gas temperature improvement in a low-loaded diesel engine

Abstract Engine manufacturers generally use aftertreatment systems to meet the strict emission criteria on automotive diesel engines. However, those systems operate inefficiently particularly at low-loaded cases of diesel engines since exhaust gas temperatures at aftertreatment inlet remain below 250 °C. For those cases, variable valve timing (VVT) method can be applied to elevate exhaust temperatures and improve aftertreatment emission conversion efficiency. Therefore, in this study, intake valve closing (IVC) timing is advanced and retarded sufficiently from the base condition on a low-loaded diesel engine to increase aftertreatment inlet exhaust temperature above 250 °C. A specially designed computer program, Lotus Engine Simulation (LES), is utilized to model the diesel engine. Experimental data of a similar study is used for the validation of the simulation. Engine loading (taken as brake mean effective pressure (BMEP)) is kept constant at 2.5 bar by adjusting the fuel injection rate. The results show that there is a considerable exhaust temperature rise (up to 65 °C) at aftertreatment inlet with the method and it is adequate for effective aftertreatment performance (Texhaust > 250 °C). It is also seen that the increase on exhaust temperature is due to the sudden reduction on volumetric efficiency (from 94% to 65%). Therefore, there is lower air induction into the cylinders and hence lower pumping losses which result in fuel-efficiency in the system. However, air flow reduction also causes a sharp decrease on the exhaust flow rate which affects the heat capacity of exhaust gases negatively in the system.

[1]  Pingen Chen,et al.  Air-fraction modeling for simultaneous Diesel engine NOx and PM emissions control during active DPF regenerations , 2014 .

[2]  Mingfa Yao,et al.  Effects of late intake valve closing (LIVC) and rebreathing valve strategies on diesel engine performance and emissions at low loads , 2016 .

[3]  N Watson,et al.  A Combustion Correlation for Diesel Engine Simulation , 1980 .

[4]  Jesús Benajes,et al.  An investigation of partially premixed compression ignition combustion using gasoline and spark assistance , 2013 .

[5]  H. Yokota,et al.  Development of Efficient Urea-SCR Systems for EPA 2010-Compliant Medium Duty Diesel Vehicles , 2011 .

[6]  James E. Parks,et al.  Characterization of In-Cylinder Techniques for Thermal Management of Diesel Aftertreatment , 2007 .

[7]  Rolf D. Reitz,et al.  Effects of diesel injection strategy on natural gas/diesel reactivity controlled compression ignition combustion , 2015 .

[8]  Thomas A. Dollmeyer,et al.  Meeting the US Heavy-Duty EPA 2010 Standards and Providing Increased Value for the Customer , 2010 .

[9]  Javier Monsalve-Serrano,et al.  Effects of low reactivity fuel characteristics and blending ratio on low load RCCI (reactivity controlled compression ignition) performance and emissions in a heavy-duty diesel engine , 2015 .

[10]  W. J. D. Annand,et al.  Heat Transfer in the Cylinders of Reciprocating Internal Combustion Engines , 1963 .

[11]  Q. Fang,et al.  Influences of pilot injection and exhaust gas recirculation (EGR) on combustion and emissions in a HCCI-DI combustion engine , 2012 .

[12]  S. Chatterjee,et al.  Development of Emission Control Systems to Enable High NO x Conversion on Heavy Duty Diesel Engines , 2015 .

[13]  Eric Holloway,et al.  Modeling the impact of early exhaust valve opening on exhaust aftertreatment thermal management and efficiency for compression ignition engines , 2015 .

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

[15]  R Modiyani,et al.  Effect of intake valve closure modulation on effective compression ratio and gas exchange in turbocharged multi-cylinder engines utilizing EGR , 2011 .

[16]  Ian Graham Pegg,et al.  The effects of early inlet valve closing and cylinder disablement on fuel economy and emissions of a direct injection diesel engine , 2015 .

[17]  Alexander Rempel,et al.  Investigation of VVA-Based Exhaust Management Strategies by Means of a HD Single Cylinder Research Engine and Rapid Prototyping Systems , 2013 .

[18]  Bin Zhang,et al.  Multidisciplinary design optimization of the diesel particulate filter in the composite regeneration process , 2016 .

[19]  Wenming Yang,et al.  Combustion and emissions characteristics of diesel engine fueled by biodiesel at partial load conditions , 2012 .

[20]  A. Mayer,et al.  Engine Intake Throttling for Active Regeneration of Diesel Particle Filters , 2003 .

[21]  Adolfo Senatore,et al.  Particulate filter behaviour of a Diesel engine fueled with biodiesel , 2012 .

[22]  John B. Heywood,et al.  An Improved Friction Model for Spark-Ignition Engines , 2003 .

[23]  Krishna Kumar,et al.  Lost-Motion VVA Systems for Enabling Next Generation Diesel Engine Efficiency and After-Treatment Optimization , 2010 .

[24]  Wenming Yang,et al.  Effects of fatty acid methyl esters proportion on combustion and emission characteristics of a biodiesel fueled diesel engine , 2016 .

[25]  Akash Garg,et al.  Fuel-efficient exhaust thermal management using cylinder throttling via intake valve closing timing modulation , 2016 .

[26]  Sharareh Honardar,et al.  Exhaust Temperature Management for Diesel Engines Assessment of Engine Concepts and Calibration Strategies with Regard to Fuel Penalty , 2011 .

[27]  Choongsik Bae,et al.  An investigation on the effects of late intake valve closing and exhaust gas recirculation in a single-cylinder research diesel engine in the low-load condition , 2016 .

[28]  Donald W. Stanton,et al.  Diesel Engine Technologies Enabling Powertrain Optimization to Meet U.S. Greenhouse Gas Emissions , 2013 .