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Technical Paper

Injection Strategy Optimization for a Light Duty DI Diesel Engine in Medium Load Conditions with High EGR rates

Further restrictions on NOx emissions and the extension of current driving cycles for passenger car emission regulations to higher load operation in the near future (such as the US06 supplement to the FTP-75 driving cycle) requires attention to low emission combustion concepts in medium to high load regimes. One possibility to reduce NOx emissions is to increase the EGR rate. The combustion temperature-reducing effects of high EGR rates can significantly reduce NO formation, to the point where engine-out NOx emissions approach zero levels. However, engine-out soot emissions typically increase at high EGR levels, due to the reduced soot oxidation rates at reduced combustion temperatures and oxygen concentrations.
Technical Paper

Gasoline HCCI Modeling: Computer Program Combining Detailed Chemistry and Gas Exchange Processes

A skeletal reaction mechanism (101 species, 479 reactions) for a range of aliphatic hydrocarbons was constructed for application to computational fluid dynamics (CFD) Gasoline Homogeneous Charge Compression Ignition (HCCI) engine modeling. The mechanism is able to predict shock tube ignition delays and premixed flame propagation velocities for the following components: hydrogen (H2), methane (CH4), acetylene (C2H2), propane (C3H8), n-heptane (C7H16) and iso-octane (C8H18). The mechanism is integrated with a simulation code combining both modeling of detailed chemistry and gas exchange processes. This simulation tool was constructed by connecting the SENKIN code of the CHEMKIN library to the AVL BOOST™ engine cycle simulation code. Using a complete engine cycle simulation code instead of a code that only considers the combustion process has a major advantage. The initial conditions at the intake valve closure (IVC) have no longer to be set.
Technical Paper

Gasoline HCCI Modeling: An Engine Cycle Simulation Code with a Multi-Zone Combustion Model

For the application to Gasoline Homogenous Charge Compression Ignition (HCCI) modeling, a multi-zone model was developed. For this purpose, the detailed-chemistry code SENKIN from the CHEMKIN library was modified. In a previous paper, the authors explained how piston motion and a heat transfer model were implemented in the SENKIN code to make it applicable to engine modeling. The single-zone model developed was successfully implemented in the engine cycle simulation code AVL BOOST™. A multi-zone model, including a crevice volume, a quench layer and multiple core zones, is introduced here. A temperature distribution specified over these zones gives this model a wider range of application than the single-zone model, since fuel efficiency, emissions and heat release can now be predicted more accurately. The SENKIN-BOOST multi-zone model predictions are compared with experimental data.
Technical Paper

Experimental and Numerical Investigation of Split Injections at Low Load in an HDDI Diesel Engine Equipped with a Piezo Injector

In order to investigate the effects of split injection on emission formation and engine performance, experiments were carried out using a heavy duty single cylinder diesel engine. Split injections with varied dwell time and start of injection were investigated and compared with single injection cases. In order to isolate the effect of the selected parameters, other variables were kept constant. In this investigation no EGR was used. The engine was equipped with a common rail injection system with a piezo-electric injector. To interpret the observed phenomena, engine CFD simulations using the KIVA-3V code were also made. The results show that reductions in NOx emissions and brake specific fuel consumption were achieved for short dwell times whereas they both were increased when the dwell time was prolonged. No EGR was used so the soot levels were already very low in the cases of single injections.
Technical Paper

A Novel Concept for Combined Hydrogen Production and Power Generation

A novel concept of combined hydrogen production and power generation system based on the combustion of aluminum in water is explored. The energy conversion system proposed is potentially able to provide four different energy sources, such us pressurized hydrogen, high temperature steam, heat, and work at the crankshaft on demand, as well as to fully comply with the environment sustainability requirements. Once aluminum oxide layer is removed, the pure aluminum can react with water producing alumina and hydrogen while releasing a significant amount of energy. Thus, the hydrogen can be stored for further use and the steam can be employed for energy generation or work production in a supplementary power system. The process is proved to be self-sustained and to provide a remarkable amount of energy available as work or hydrogen.