CFD Investigation into Diesel PCCI Combustion with Optimized Fuel Injection

Abstract

A multi-pulse injection strategy for premixed charge compression ignition (PCCI) combustion was investigated in a four-valve, direct-injection diesel engine by a computational fluid dynamics (CFD) simulation using KIVA-3V code coupled with detailed chemistry. The effects of fuel splitting proportion, injection timing, spray angles, and injection velocity were examined. The mixing process and formation of soot and nitrogen oxide (NO x ) emissions were investigated as the focus of the research. The results show that the fuel splitting proportion and the injection timing impacted the combustion and emissions significantly due to the considerable changes of the mixing process and fuel distribution in the cylinder. While the spray, inclusion angle and injection velocity at the injector exit, can be adjusted to improve mixing, combustion and emissions, appropriate injection timing and fuel splitting proportion must be jointly considered for optimum combustion performance.Keywords: diesel combustion; KIVA-3V; split injection; premixed charge compression ignition; emissions Acronyms: ATDC = after top dead centre; CO = carbon monoxide; EGR = exhaust gas recirculation; EVC = exhaust valve close; EVO = exhaust valve opening; HCCI = homogeneous charge compression ignition; HC = hydrocarbon; HRR = heat release rate; HSDI = high speed direct injection; HTHR = high temperature heat release; ISFC = indicated specific fuel consumption; IVC = intake valve close; IVO = intake valve OPEN ACCESSEnergies 2011, 4 518 opening; LTC = low temperature combustion; NO x = nitrogen oxides; PCCI = premixed charge compression ignition; PRR = pressure rise rate; TDC = top dead centre; TSC = two-stage combustion; UHC = unburned hydrocarbon

Combustion process shaping by use of different strategies of multiple fuel injection in a CI model engine

“…Similar effects were observed in research [9] when a small pilot fuel dose was applied. The investigations presented in [10,11] also indicate a reduction of the emission of particulate matter; (b) The results of the investigations presented in [12,13] indicate an improvement in the fuel combustion and consequently a reduction of the fuel consumption through fuel dose division (as compared to a single fuel dose injection); (c) From the investigations presented in [9] results the dependence of the NO x emission from the size of the first fuel dose: a large pilot fuel dose increases the homogeneity of the charge and a reduction of the NO x emission can be obtained through a delay of the injection of the main fuel dose. In a situation when the injection angle of the first fuel dose was increased by 20°-25°a lower emission of HC and CO was observed; (d) Literature analysis [8,13] is related to an engine fitted with an exhaust recirculation system.…”

Application of canola oil operation in a diesel engine with common rail system

“…Because of the flexibility of the common rail injection, it was possible to introduce new kinds of combustion processes, such as Premixed Charge Compression Ignition-based combustion (PCCI [1,2] in diesel engines. Recently, modified PCCI process with dual-fuels was reported by different engine researchers [3,4].…”

Investigation on an Injection Strategy Optimization for Diesel Engines Using a One-Dimensional Spray Model

“…To cope with the emission problem and improve the performance of diesel engines, the common rail technology has flourished around the world. The advanced fuel injection technologies in a common rail system, such as the ultrahigh injection pressure [1][2][3][4] and the multiple-injection strategy [5][6][7] as well as the high control accuracy [8], have greatly improved the performance of diesel engines. Under the action of ultrahigh injection pressures, the fuel can be injected into the cylinder in a short time, while the multiple-injection strategy divides the whole injection duration into many parts, creating shorter injection durations.…”