Browse Publications Technical Papers 2017-01-0779

The Impact of a Combustion Chamber Optimization on the Mixture Formation and Combustion in a CNG-DI Engine in Stratified Operation 2017-01-0779

A previous study by the authors has shown an efficiency benefit of up to Δηi = 10 % for stratified operation of a high pressure natural gas direct injection (DI) spark ignition (SI) engine compared to the homogeneous stoichiometric operation with port fuel injection (PFI). While best efficiencies appeared at extremely lean operation at λ = 3.2, minimum HC emissions were found at λ = 2. The increasing HC emissions and narrow ignition time frames in the extremely lean stratified operation have given the need for a detailed analysis. To further investigate the mixture formation and flame propagation und these conditions, an optically accessible single-cylinder engine was used. The mixture formation and the flame luminosity have been investigated in two perpendicular planes inside the combustion chamber. By quantifying the equivalence ratio using the laser-induced fluorescence (LIF) technique a correlation between the presence of an ignitable mixture at the spark plug and the indicated start of combustion (SOC) was shown [1]. Through the investigation of the flame luminosity, the main reason for incomplete combustion and the according emissions was revealed. With this cause-and-effect comprehension, the combustion chamber has been modified to enforce an improved charge stratification. A geometric modification of the piston head ensures deflecting the ignitable mixture to the spark plug and prevents the injection from reaching the inner cylinder wall and crevices. Optical investigations were used to develop a design that improves mixture formation.


Subscribers can view annotate, and download all of SAE's content. Learn More »


Members save up to 16% off list price.
Login to see discount.
Special Offer: Download multiple Technical Papers each year? TechSelect is a cost-effective subscription option to select and download 12-100 full-text Technical Papers per year. Find more information here.
We also recommend:

Meeting 2025 CAFE Standards for LDT with Fuel-Efficient Diesel Powertrains - Approaches and Solutions


View Details


Spark Ignited Direct Injection Natural Gas Combustion in a Heavy Duty Single Cylinder Test Engine - Nozzle Included Angle Effects


View Details


Optimization of the E-TEC™ Combustion System for Direct-Injected Two-Stroke Engines Toward 3-Star Emissions


View Details