Numerical study of EGR effects on reducing the pressure rise rate of HCCI engine combustion

Abstract

The effects of the inert components of exhaust gas recirculation (EGR) gas on reducing the pressure rise rate of homogeneous charge compression ignition engine combustion were investigated numerically by utilizing the CHEMKIN II package and its SENKIN code, as well as Curran's dimethyl ether reaction scheme. Calculations were conducted under constant volume combustion and engine combustion (one compression and one expansion only, respectively) conditions. Results show that with constant fuel amount and initial temperature and pressure, as EGR ratio increases, combustion timings are retarded and the duration of thermal ignition preparation extends non-linearly; peak values of pressure, pressure rising rate (PRR), and temperature decrease; and peak values of heat release rate in both low temperature heat release (LTHR) and high temperature heat release decrease. Moreover, maximum PRR decreases as CA50 is retarded. With constant fuel amount, mixtures with different EGR ratios can obtain the same CA50 by adjusting the initial temperature. Under the same CA50, as EGR ratio increases, the LTHR timing is advanced and the duration of thermal ignition preparation is extended. Maximum PRR is almost constant with the fixed CA50 despite the change in EGR ratio, indicating that the influence of EGR dilution on chemical reaction rate is offset by other factors. Further investigation on the mechanism of this phenomenon is needed.

Effective reduction of in-cylinder peak pressures in Homogeneous Charge Compression Ignition Engine – A computational study

“…As swirl ratio increases; lower peak pressures are obtained at any EGR concentration, but percentage reduction in peak pressures is high at higher swirl ratios and higher EGR concentrations. The reason for this phenomenon is increase in turbulence owing to increased wall heat transfer because of increased swirl ratios [28,29]. This study also indicated modest shift in the occurrence of maximum peak pressure towards TDC with increase in EGR concentrations [30].…”

“…They reported that with increase in EGR fraction retarded the start of combustion and decreased the peak pressure and temperature rise. Under the same conditions with increase in EGR ratio, extension in preparation of thermal ignition and advancement in LTHR timing were observed [7]. Swirl helps in homogeneous mixture formation of the fuel and air [8].…”

Numerical study of effects of the intermediates and initial conditions on flame propagation in a real homogeneous charge compression ignition engine

“…Calculation is carried out based on the following assumptions: (1) A premixed mixture is homogeneous. The LTHR starting is the timing where HRR reaches 1.0 J/CA and the HTHR starting is the timing where the mole fraction of H 2 O 2 reaches its maximum value [31]. (3) No heat transfer.…”

Numerical study of EGR effects on the combustion process parameters in HCCI engines

“…The effects of the inert components of EGR gas on reducing of the pressure rise rate of homogeneous charge compression ignition engine combustion were investigated numerically in paper [8] by utilizing the CHEMKIN II package and its SENKIN code, as well as Curran's dimethyl ether reaction scheme. Calculations were conducted under constant volume combustion and engine combustion conditions (one compression and one expansion only, respectively).…”

“…Badania numeryczne wpływu obojętnych składników EGR na ograniczenie szybkości narastania ciśnienia w silniku HCCI, z wykorzystaniem pakietu CHEMKIN II, kodu SENKIN oraz schematu reakcji Currana dimetylu eteru, przeprowadzono w pracy [8]. Obliczenia prowadzono dla stałej objętości spalania i dla warunków silnika spalinowego (odpowiednio dla jednego suwu sprężania i jednego suwu rozprężania).…”