In the last four years Ricardo has developed a multi-cylinder gasoline DI engine with stratified combustion and multiple injections. Ricardo started in 2008 with literature studies, engine benchmarking, design studies, fuel spray characterization and CFD spray and combustion modelling. The next step was the combustion system development by means of an optical single cylinder engine in order to design the combustion system in detail, a definition of the control system and a validation of the CFD models. With the results of the single cylinder research engine a 4 cylinder engine was built to demonstrate the real potential of the T-SGDI concept. An in-house design of experiments process was utilized to determine the optimal operating parameters for part load lean stratified operation in a spray guided gasoline direct injection engine with respect to fuel consumption, engine operation stability and engine out emissions. The variables for the DoE were engine speed, engine load by means of total fuel quantity, number of injections, injection shape factor and EGR rate. It could be shown that the application of multiple injections can be used to retard the 50% MFB angle to a thermodynamic optimized position when compared to a single injection event. As a result, the peak in-cylinder gas pressures and temperatures were lower, leading to reduced engine out NOx emissions. Furthermore, the range of ignition angle for stable combustion could be increased, when using multiple injections compared to a single injection event. The combustion system has been proven to be comparable to market leading systems, with robust stratified NA engine operation to loads of up to 7 bar BMEP and engine speeds of up to 4500 rev/min. Combining advanced multiple injection strategies with boosting enabled the stratified operating range to be extended to over 15 bar BMEP, with a further significant improvement in fuel consumption to class leading levels. As the load exceeded 8 bar BMEP the MIVIS injection strategy was superior, in fuel consumption terms, to the multiple injection strategy used at the lower loads and on the singe cylinder engine in order to minimize NOx emissions. The extended WOT part load operating region also increased the mass flow through the engine when compared to a conventional throttle boosted gasoline engine: this resulted in an improved turbocharger transient response, which is a key issue particularly for downsized gasoline engines where the downsizing could be as high as 50%. Finally, the robustness of the SGDI combustion system to the highest loads, in combination with the latest boosting and future knock mitigation technologies, has been clearly demonstrated. With these measures the T-SGDI engine achieves a maximum brake thermal efficiency about 41% at 2500 rev/min and 13 bar BMEP. The best fuel consumption at 2000 rev/min, 2 bar BMEP is about 278 g/kWh.


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    Title :

    Next generation of highly turbocharged DI gasoline engines with multiple injections and high EGR rates


    Contributors:


    Publication date :

    2012


    Size :

    14 Seiten, 10 Bilder, 1 Tabelle, 8 Quellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English





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