Progress and recent trends in homogeneous charge compression ignition (HCCI) engines

Conceptual models for partially premixed low-temperature diesel combustion

Evolution, challenges and path forward for low temperature combustion engines

Diesel spray experiments at controlled high-temperature and high-pressure conditions offer the potential for an improved understanding of diesel combustion, and for the development of more accurate CFD models that will ultimately be used to improve engine design. Several spray chamber facilities capable of high-temperature, high-pressure conditions typical of engine combustion have been developed, but uncertainties about their operation exist because of the uniqueness of each facility. For the IMEM meeting, we describe results from comparative studies using constant-volume vessels at Sandia National Laboratories and IFP. Targeting the same ambient gas conditions (900 K, 60 bar, 22.8 kg/m{sup 3}, 15% oxygen) and sharing the same injector (common rail, 1500 bar, KS1.5/86 nozzle, 0.090 mm orifice diameter, n-dodecane, 363 K), we describe detailed measurements of the temperature and pressure boundary conditions at each facility, followed by observations of spray penetration, ignition, and combustion using high-speed imaging. Performing experiments at the same high-temperature, high-pressure operating conditions is an objective of the Engine Combustion Network (http://www.ca.sandia.gov/ECN/), which seeks to leverage the research capabilities and advanced diagnostics of all participants in the ECN. We expect that this effort will generate a high-quality dataset to be used for advanced computational model development at engine conditions.

Comparison of Diesel Spray Combustion in Different High-Temperature, High-Pressure Facilities

Entrainment Waves in Diesel Jets

Optical Investigation of Dual-fuel CNG/Diesel Combustion Strategies to Reduce CO 2 Emissions

On the origin of Unburned Hydrocarbon Emissions in a Wall Guided, Low NOx Diesel Combustion System

Formation of Unburned Hydrocarbons in Low Temperature Diesel Combustion

Improving Emissions, Noise and Fuel Economy Trade-Off by using Multiple Injection Strategies in Diesel Low Temperature Combustion (LTC) Mode

The influence of piston geometry on the in-cylinder mixture distribution and combustion process in an optically-accessible, direct injection HCCI Diesel engine has been investigated. A new, purpose-designed piston which allows optical access directly into the combustion chamber bowl permitted the application of a number of optical diagnostic techniques. Firstly, laser-induced exciplex fluorescence (LIEF) has been applied in order to characterize the fuel spray and vapor development within the piston bowl. Subsequently a detailed study of the auto-ignition and two-stage Diesel HCCI combustion process has been conducted by a combination of direct chemiluminescence imaging, laser induced fluorescence (LIF) of the intermediate species formaldehyde (CH 2 O) which is present during the cool flame and LIF of the OH radical later present in the reaction and burned gas zones at higher temperature. Finally, spectrometry measurements were conducted with the objective of determining the emitting species of the chemiluminescence signal. The experiments were performed on a single cylinder optical engine equipped with a conventional common rail injection system and narrow angle injector. Results obtained for two re-entrant piston bowl designs (flat piston and bowl-dome piston) show that the geometry plays a significant role on mixture preparation and subsequently the combustion and emissions characteristics for late injection in HCCI mode particularly in such cases where liquid impingement is unavoidable. Planar LIF 355 imaging revealed the presence of the intermediate species formaldehyde allowing the temporal and spatial detection of auto-ignition precursors prior to the signal observed by chemiluminescence in the early stages of the cool flame. Formaldehyde was then rapidly consumed at the start of the 'hot' combustion which was marked not only by the increase in the main heat release but also by the first detection of OH, present within the reaction and burned gas zones. In the case of the flat piston geometry, soot precursors were also detected, as indicated by the strong PAH fluorescence signal observed later in the cycle (from 375 CAD).

Mixture Preparation and Combustion via LIEF and LIF of Combustion Radicals in a Direct-Injection, HCCI Diesel Engine

Julian Kashdan

Papers

Optical Investigation of Dual-fuel CNG/Diesel Combustion Strategies to Reduce CO 2 Emissions

On the origin of Unburned Hydrocarbon Emissions in a Wall Guided, Low NOx Diesel Combustion System

Formation of Unburned Hydrocarbons in Low Temperature Diesel Combustion

Improving Emissions, Noise and Fuel Economy Trade-Off by using Multiple Injection Strategies in Diesel Low Temperature Combustion (LTC) Mode

Mixture Preparation and Combustion via LIEF and LIF of Combustion Radicals in a Direct-Injection, HCCI Diesel Engine