Comparison of Different Boosting Strategies for Homogeneous Charge Compression Ignition Engines - A Modeling Study

Abstract

Boosted Homogeneous Charge Compression Ignition (HCCI) has been modeled and has demonstrated the potential to extend the engine's upper load limit. A commercially available engine simulation software (GT-Power®) coupled to the University of Michigan HCCI combustion and heat transfer correlations was used to model a 4-cylinder boosted HCCI engine with three different boosting configurations: turbocharging, supercharging and series turbocharging. The scope of this study is to identify the best boosting approach in order to extend the HCCI engine's operating range. The results of this study are consistent with the literature: Boosting helps increase the HCCI upper load limit, but matching of turbochargers is a problem. In addition, the low exhaust gas enthalpy resulting from HCCI combustion leads to high pressures in the exhaust manifold increasing pumping work. The series turbocharging strategy appears to provide the largest load range extension. Single turbocharging is the most efficient but is limited by increased mass flow rates at increased engine speeds. Supercharging helps avoid the backpressure problem but the mechanical work of the supercharger reduces useful work affecting overall brake efficiency.

The effects of boost pressure on stratification and burn duration of gasoline homogeneous charge compression ignition combustion

“…The intake and exhaust manifold absolute pressures are set at 1, 1.5 and 2 bar for the boost sweep. For turbocharged HCCI, the exhaust manifold pressures are typically much greater than the intake manifold pressures; 11–14 however, this work makes a modeling simplification by setting the intake and exhaust pressures equal to each other. The amount of fuel injected is increased with boost to hold the mixture composition constant in terms of fuel-to-oxygen equivalence ratio ( ϕ FO ), fuel-to-charge equivalence ratio ( ϕ ′ ), residual gas fraction (RGF) and oxygen mole percentage ( χ O 2 ).…”

“…9 In addition to experimental studies, 6–9 a number of simulation studies have been performed to assess the requirements of boosted HCCI turbomachinary. 10–14 Typically, boosted HCCI demands higher intake pressures at similar conditions than conventional engines due to greater dilution required to beat the NOx emission limit. 7 On the other hand, intake boost for turbocharged HCCI comes at a significant pumping penalty.…”

The interaction between compression ratio, boosting and variable valve actuation for high load homogeneous charge compression ignition: A modeling study

“…Mamalis et al 1,8 have presented detailed literature reviews in previous publications regarding VVA and boosting for HCCI engines. Some key findings will be summarized here for completeness.…”

Boost System Development for Gasoline Direct-Injection Compression-Ignition (GDCI)

“…A study of boosting strategies for HCCI performed by Mamalis, et al, [14] concluded that a staged turbocharger system extends the load range at 2000 rev/m. The additional pumping work of the boost system reduced the brake efficiency, however.…”