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Technical Paper

Pressure Drop and Soot Regeneration Characteristics through Hexagonal and Square Cell Diesel Particulate Filters

Although diesel engines have higher output torque, lower fuel consumption, and lower HC pollutant emissions, larger amounts of NOx and PM are emitted, compared with equivalent gasoline engines. The diesel particulate filters (DPF) have proved one of the most promising aftertreatment technologies due to the more stringent particulate matters (PM) regulations. In this study, the computational fluid dynamics (CFD) model of DPF was built by utilizing AVL-Fire software code. The main objective of this paper was to investigate the pressure drop and soot regeneration characteristics of hexagonal and conventional square cell DPFs with various inlet mass flow rates, inlet temperatures, cell densities, soot loads and ash loads. Different cell geometry shapes of DPF were evaluated under various ash distribution types.
Technical Paper

Fuel Saving Potential of Different Turbo-Compounding Systems Under Steady and Driving Cycles

The performance of three different electric turbo-compounding systems under both steady and driving cycle condition is investigated in this paper. Three configurations studied in this paper are serial turbo-compounding, parallel turbo-compounding and electric assisted turbo-compounding. The electric power, global gain of the whole system (engine and power turbine) under steady operating condition is firstly studied. Then investigation under three different driving cycles is conducted. Items including fuel consumption, engine operating point distribution and transient response performance are analyzed among which the second item is done based on statistic method combined with the results obtained under steady operating conditions. Study under steady condition indicates that electric assisted turbo-compounding system is the best choice compared with the other two systems. The performance of serial turbo-compounding is load oriented while parallel configuration is speed oriented.
Technical Paper

The Application and Optimization of EGR-LNT Synergetic Control System on Lean-burn Gasoline Engine

Ensuring lower emissions and better economy (fuel economy and after-treatment economy) simultaneously is the pursuit of future engines. An EGR-LNT synergetic control system was applied to a modified lean-burn CA3GA2 gasoline engine. Results showed that the synergetic control system can achieve a better NOx reduction than sole EGR and sole LNT within a proper range of upstream EGR rate and without the penalty in fuel consumption. It also has the potential to save costly noble metals in LNT, but excessive or deficient upstream EGR would make the synergetic control system inefficiency. In order to guarantee the objectivity of the effect of EGR-LNT synergetic control system on NOx reduction, another modified lean-burn CA4GA5 gasoline engine was additionally tested.
Technical Paper

Research in the Effects of Intake Manifold Length and Chamber Shape on Performance for an Atkinson Cycle Engine

In order to improve the fuel consumption and expand the range of low fuel consumption area of a 1.5L Atkinson cycle PFI engine, the effect of the intake manifold length and chamber shape on the engine performance is investigated by setting up a GT-power (1-D) and an AVL-Fire (3-D) computational model which are calibrated with experimental data. After this the new engine was transformed to the test bench to do the calibration experiment. The results demonstrate that the intake manifold case_1 (the length is 300mm, side intake form) matched with a new designed chamber improves combustion in cylinder with a range 1.6∼7.4g/(kW•h) reduced in fuel consumption of speed that has been studied; the case_3 (the length is 100mm, intermediate intake form) matched with the new designed chamber with a range 3.86∼7g/(kW•h) reduced in fuel consumption of speed that has been studied. Both case_1 and case_3 expand the range of low fuel consumption area significantly.
Technical Paper

A Numerical Study on Combustion and Emission Characteristics of Marine Engine through Miller Cycle Coupled with EGR and Water Emulsified Fuel

The combustion in low-speed two-stroke marine diesel engines can be characterized as large spatial and temporal scales combustion. One of the most effective measures to reduce NOx emissions is to reduce the local maximum combustion temperature. In the current study, multi-dimensional numerical simulations have been conducted to explore the potential of Miller cycle, high compression ratio coupled with EGR (Exhaust Gas Recirculation) and WEF (water emulsified fuel) to improve the trade-off relationship of NOx-ISFC (indicated specific fuel consumption) in a low-speed two-stroke marine engine. The results show that the EGR ratio could be reduced combined with WEF to meet the Tier III emission regulation. The penalty on fuel consumption with EGR and WEF could be offset by Miller cycle and high geometric compression ratio.
Technical Paper

Pressure Drop and Soot Accumulation Characteristics through Diesel Particulate Filters Considering Various Soot and Ash Distribution Types

Although diesel engines offer higher thermal efficiency and lower fuel consumption, larger amounts of Particulate Matters (PM) are emitted in comparison with gasoline engines. The Diesel Particulate Filters (DPF) have proved one of the most promising technologies due to the “particle number” emissions regulations. In this study, the Computational Fluid Dynamics (CFD) multi-channel model of DPF was built properly by utilizing AVL-Fire software code to evaluate the pressure drop and soot accumulation characteristics of DPF. The main objective of this paper was to investigate the effects of soot (capacity and deposit forms) and ash (capacity and distribution factors) interaction on DPF pressure drop and soot accumulation, as well as the effects of DPF boundary conditions (inlet mass flow rate and inlet temperature) on pressure drop.
Technical Paper

Effects of EGR and Injection Strategies on the Performance and Emissions of a Two-Stroke Marine Diesel Engine

Clean combustion is critical for marine engines to meet the Tier III emission regulation. In this paper, the effects of EGR and injection strategies (including injection pressure, injection timing as well as multiple injection technology) on the performance and emissions of a 2-stroke, low speed marine diesel engine were investigated by using computational fluid dynamics (CFD) simulations to reach the IMO Tier III NOx emissions target and reduce the fuel consumption rate. Due to the large length scale of the marine engine, RANS simulation was performed in combination with the CTC-SHELL combustion model. Based on the simulation model, the variation of the cylinder pressure curve, the average temperature in the cylinder, the combustion heat release rate and the emission characteristics were studied.
Technical Paper

Simulation of the Effect of Intake Pressure and Split Injection on Lean Combustion Characteristics of a Poppet-Valve Two-Stroke Direct Injection Gasoline Engine at High Loads

Poppet-valve two-stroke gasoline engines can increase the specific power of their four-stroke counterparts with the same displacement and hence decrease fuel consumption. However, knock may occur at high loads. Therefore, the combustion with stratified lean mixture was proposed to decrease knock tendency and improve combustion stability in a poppet-valve two-stroke direct injection gasoline engine. The effect of intake pressure and split injection on fuel distribution, combustion and knock intensity in lean mixture conditions at high loads was simulated with a three-dimensional computational fluid dynamic software. Simulation results show that with the increase of intake pressure, the average fuel-air equivalent ratio in the cylinder decreases when the second injection ratio was fixed at 70% at a given amount of fuel in a cycle.
Technical Paper

Numerical Investigation of the Potential of Late Intake Valve Closing (LIVC) Coupled with Double Diesel Direct-Injection Strategy for Meeting High Fuel Efficiency with Ultra-Low Emissions in a Heavy-Duty Reactivity Controlled Compression Ignition (RCCI) Engine at High Load

In this study, the potential of diesel/gasoline RCCI combustion equipped with late intake valve closing (LIVC) combined with double direct injection strategy for meeting high fuel efficiency with ultra-low emissions was investigated. The study was aiming at high load operation based on a heavy-duty diesel engine. The RCCI combustion was realized by port injection of gasoline and in-cylinder direct injection for the formation of stratified reactivity of the in-cylinder charge. Moreover, with the employment of double injection of diesel fuel, the concentration stratification of the high-reactivity fuel was obtained, which is to further realize effective control of the combustion phasing, pressure rise rate. Meanwhile, the employment of LIVC strategy is to control the maximum in-cylinder pressure and NOx emissions.
Technical Paper

The application of Controlled Auto-Ignition Gasoline Engines -The challenges and solutions

Controlled auto-ignition (CAI) combustion, also known as homogeneous charge compression ignition (HCCI), has the potential to simultaneously reduce the fuel consumption and nitrogen oxides (NOx) emissions of gasoline engines. However, narrow operating region in loads and speeds is one of the challenges for the commercial application of CAI combustion to gasoline engines. Therefore, the extension of loads and speeds is an important prerequisite for the application of CAI combustion to gasoline engines. The effect of intake charge boosting, charge stratification and spark-assisted ignition on the operating range in CAI mode was reviewed. Stratified flame ignition (SFI) hybrid combustion is one form to achieve CAI combustion under the conditions of highly diluted mixture caused by the flame in the stratified mixture with the help of spark plug.