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The optimization study presented herein is aimed to minimize the fuel consumption and engine-out emissions using commercially available EN15940 compatible HVO (Hydrogenated Vegetable Oil) fuel. The investigations were carried out on FEV’s 3rd generation HECS (High Efficiency Combustion System) multi-cylinder engine (1.6L, 4 Cylinder, Euro 6). Using a global DOE approach, the effects of calibration parameters on efficiency and emissions were obtained and analyzed. This was followed by a global optimization procedure to obtain a dedicated calibration for HVO. The study was aiming for efficiency improvement and it was found that at lower loads, higher fractions of low pressure EGR in combination with lower fuel injection pressures were favorable. At higher loads, a combustion center advancement, increase of injection pressure and reduced pilot injection quantities were possible without exceeding the noise and NOx levels of the baseline Diesel.

Despite the trend in increased prosperity, the Indian automotive market, which is traditionally dominated by highly cost-oriented producion, is very sensitive to the price of fuels and vehicles. Due to these very specific market demands, the U-LCV (ultra-light commercial vehicle) segment with single cylinder natural aspirated Diesel engines (typical sub 650 cc displacement) is gaining immense popularity in the recent years. By moving to 2016, with the announcement of leapfrogging directly to Bharat Stage VI (BS VI) emission legislation in India, and in addition to the mandatory application of Diesel particle filters (DPF), there will be a need to implement effective NOx aftertreament systems. Due to the very low power-to-weight ratio of these particular applications, the engine operation takes place under full load conditions in a significant portion of the test cycle.

This work is a continuation of earlier results presented by the authors. In the current investigations the biofuels hydrogenated vegetable oil (HVO) and 1-octanol are investigated as pure components and compared to EN 590 Diesel. In a final step both biofuels are blended together in an appropriate ratio to tailor the fuels properties in order to obtain an optimal fuel for a clean combustion. The results of pure HVO indicate a significant reduction in CO-, HC- and combustion noise emissions at constant NOX levels. With regard to soot emissions, at higher part loads, the aromatic free, paraffinic composition of HVO showed a significant reduction compared to EN 590 petroleum Diesel fuel. But at lower loads the high cetane number leads to shorter ignition delays and therefore, ignition under richer conditions.

Improvements in the efficiency of internal combustion engines has led to a reduction in exhaust gas temperatures. The simultaneous tightening of exhaust emission limits requires ever more complex emission control methods, including aftertreatment whose efficiency is crucially dependent upon the exhaust gas temperature. Double-walled (also called air-gap) exhaust manifold and turbine housing modules made from sheet metal have been used in gasoline engines since 2009. They offer the potential in modern Diesel engines to reduce both the emissions of pollutants and fuel consumption. They also offer advantages in terms of component weight and surface temperatures in comparison to cast iron components. A detailed analysis was conducted to investigate the potential advantages of insulated exhaust systems for modern diesel engines equipped with DOC and SCR coated DPF (SDPF).

As emission regulations are becoming increasingly stringent worldwide, multiple exhaust aftertreatment devices are considered in order to minimize diesel engine tailpipe emissions. For the typical diesel applications in developing markets like India, the fuel consumption is a very decisive selling argument for customers. The total cost of ownership needs to be as low as possible. To meet these competing requirements, the aftertreatment and engines must be optimized at the same time as the performance of the one system affects the other. In state-of-the-art calibration processes, the aftertreatment systems are considered separately from the calibration of the thermodynamics. This conventional approach makes it more challenging to achieve a simultaneous optimization of the fuel consumption and tailpipe emissions under transient operating conditions.

Within this study a dual-fuel concept was experimentally investigated. The utilized fuels were conventional EN228 RON95E10 and EN590 Diesel B7 pump fuels. The engine was a single cylinder Diesel research engine for passenger car application. Except for the installation of the port fuel injection valve, the engine was not modified. The investigated engine load range covered low part load operation of IMEP = 4.3 bar up to IMEP = 14.8 bar at different engine speeds. Investigations with Diesel pilot injection showed that the dual-fuel approach can significantly reduce the soot/NOx-trade-off, but typically increases the HC- and CO-emissions. At high engine load and gasoline mass fraction, the premixed gasoline/air self-ignited before Diesel fuel was injected. Reactivity Controlled Compression Ignition (RCCI) was subsequently investigated in a medium load point at IMEP = 6.8 bar.

Within a project of the Research Association for Combustion Engines e.V., different measures for rising the temperature of exhaust gas aftertreatment components of both a passenger car and an industrial/commercial vehicle engine were investigated on a test bench as well as in simulation. With the passenger car diesel engine and different catalyst configurations, the potential of internal and external heating measures was evaluated. The configuration consisting of a NOx storage catalyst (NSC) and a diesel particulate filter (DPF) illustrates the potential of an electrically heated NSC. The exhaust aftertreatment system consisting of a diesel oxidation catalyst (DOC) and a DPF shows in simulation how variable valve timing in combination with electric heated DOC can be used to increase the exhaust gas temperature and thus fulfill the EU6 emission limits.

This study investigated dual-fuel operation with a light duty Diesel engine over a wide engine load range. Ethanol was hereby injected into the intake duct, while Diesel was injected directly into the cylinder. At low loads, high ethanol shares are critical in terms of combustion stability and emissions of unburnt hydrocarbons. As the load increases, the rates of heat release become problematic with regard to noise and mechanical stress. At higher loads, an advanced injection of Diesel was found to be beneficial in terms of combustion noise and emissions. For all tests, engine-out NOx emissions were kept within the EU-6.1 limit.

The present work is a continuation of the earlier published results by authors on the investigation of Hydrogenated Vegetable Oil (HVO) on a High Efficiency Diesel Combustion System (SAE Int. J. Fuels Lubr. Paper No. 2013-01-1677 and JSAE Paper No. 283-20145128). In order to further validate and interpret the previously published results of soot microstructure and its consequences on oxidation behavior, the test program was extended to analyze the impact of soot composition, optical properties, and physical properties such as size, concentration etc. on the oxidation behavior. The experiments were performed with pure HVO as well as with petroleum based diesel and today's biofuel (i.e. FAME) as baseline fuels. The soot samples for the different analyses were collected under constant engine operating conditions at indicated raw NOx emissions of Euro 6 level using closed loop combustion control methodology.

The regulations for mobile applications will become stricter in Euro 6 and further emission levels and require the use of active aftertreatment methods for NOX and particulate matter. SCR and LNT have been both used commercially for mobile NOX removal. An alternative system is based on the combination of these two technologies. Developments of catalysts and whole systems as well as final vehicle demonstrations are discussed in this study. The small and full-size catalyst development experiments resulted in PtRh/LNT with optimized noble metal loadings and Cu-SCR catalyst having a high durability and ammonia adsorption capacity. For this study, an aftertreatment system consisting of LNT plus exhaust bypass, passive SCR and engine independent reductant supply by on-board exhaust fuel reforming was developed and investigated. The concept definition considers NOX conversion, CO2 drawback and system complexity.