Characterization of Engine Control Authority on HCCI Combustion as the High Load Limit is Approached

Abstract

In this study the authority of the available engine controls are characterized as the high load limit of homogeneous charge compression ignition (HCCI) combustion is approached. A boosted single-cylinder research engine is used and is equipped with direct injection (DI) fueling, a laboratory air handling system, and a hydraulic valve actuation (HVA) valve train to enable negative valve overlap (NVO) breathing. Results presented include engine loads from 350 to 650 kPa IMEP net and manifold pressure from 98 to 190 kPaa. It is found that in order to increase engine load to 650 kPa IMEP net , it is necessary to increase manifold pressure and external EGR while reducing the NVO duration. While both are effective at controlling combustion phasing, NVO duration is found to be a "coarse" control while fuel injection timing is a "fine" control. NO X emissions are low throughout the study, with emissions below 0.1 g/kW-h at all boosted HCCI conditions, while good combustion efficiency is maintained (>96.5%). Net indicated thermal efficiency increases with load up to 600 kPa IMEP net , where a peak efficiency of 41% is achieved. Parametric investigations reveal that increasing exhaust gas recirculation (EGR) at a constant intake manifold pressure (MAP) and increasing MAP at a constant external EGR rate both retard combustion phasing. It is also found that combustion phasing becomes increasingly sensitive to NVO duration as engine load increases. Finally, comparisons are made between commonly used noise metrics. It is found that compared to the AVL combustion noise meter, ringing intensity (RI) significantly underestimates combustion noise under boosted HCCI conditions. CITATION: Szybist, J., Edwards, K., Foster, M., Confer, K. et al., "Characterization of Engine Control Authority on HCCI Combustion as the High Load Limit is Approached," SAE Int. J. Engines 6(1):2013,

Correlation of cylinder pressure–based engine noise metrics to measured microphone data

“…Equation (11) gives the PPRR for point n. In this study, the data acquisition CA resolution and u(n) À u(n À 1) were 0.2°CA for the diesel engine and 0.5°CA for the gasoline engine (discussed in section ''Results'')…”

“…Recent research has shown a lack of correlation between the three metrics discussed above. Szybist et al 11 demonstrated that RI and PPRR under-predict noise compared to AVL noise meter at boosted conditions. Dernotte et al 12 investigated the effect of intake pressure on noise and RI and demonstrated that increasing intake pressure would cause a noticeable decrease in RI at a fixed noise level.…”

Effects of Exhaust Gas Recirculation and Boost Pressure on Reactivity Controlled Compression Ignition Engine at High Load Operating Conditions

“…It has been reported that a high boost pressure benefits HCCI-like LTC [9]. The effect of boost pressure was studied based on the baseline case.…”

“…The use of cooled EGR at high load allows the intake pressure to be increased without having to decrease the intake temperatures below ambient, while still maintaining sufficiently delayed com bustion timings [8]. Szybist et al [9] also found that in order to reach higher load, it is necessary to increase the boost pressure and EGR while reducing NVO duration. The engine was equipped with DI fuelling and gasoline fuel containing nominally 10% etha nol (E10) was used.…”

Drive cycle simulation of high efficiency combustions on fuel economy and exhaust properties in light-duty vehicles

“…It is well known that diesel engines require complex and expensive lean exhaust afertreatment systems for NOx and PM emissions control [14][15][16]. To address aftertreatment costs, studies are exploring innovative combustion strategies which enable higher fuel efficiencies than diesel engines while simultaneously lowering engine-out emissions to reduce aftertreatment costs [17][18][19][20]. Such novel combustion modes usually involve flameless or staged fuel combustion and are known as low-temperature combustion (LTC).…”