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The objective of the study is to characterize combustion and performance of a multi-cylinder turbocharged direct-injection (DI) diesel engine at altitude conditions according to the International Standard Atmosphere (ISA). Experiments were performed on the 6.6-liter turbocharged DI diesel engine, a model similar to that of the Army’s Joint Light Tactical Vehicle. The engine was installed in the US Army Research Laboratory Small Engine Altitude Research Facility. Outside air temperature (OAT) and outside air pressure were independently controlled to match the ISA-OAT at selected altitude conditions: sea level, 1524, 3048, and 4572 m. The test engine is equipped with a single-stage variable nozzle turbocharger and Bosch CRIN 3 common-rail injection system. Three load conditions (i.e., low, mid, and high) were selected at 1400 rpm to investigate combustion and performance of the engine using Jet Propellant-8 (JP-8) fuel.

The objective of the study was to investigate the spray and combustion characteristics of Jet Propellant-8 (JP-8) using a high-pressure fuel injector which is capable of up to 250-MPa fuel injection pressure. Experiments were performed in a constant-pressure flow-through combustion chamber at the ambient conditions of 825 K and 6 MPa for the oxygen concentration of 0 and 21%. JP-8 was injected over a range of fuel injection pressures from 50 to 250 MPa for single injection events to establish a baseline operation. Pilot and post injections were used to study the effect of multiple injections on spray and combustion of the high-pressure fuel injector. Both pilot and post injection separation times and quantities were systematically varied. JP-8 spray and combustion events were imaged at 75 kHz using a combination of Mie scattering and OH* chemiluminescence imaging.

Current regulations stipulate acceptable levels of particulate emissions based on the mass collected on filters obtained by sampling in diluted exhaust. Although precise, this gives us only aggregated information. If in addition to the mass based measurements, detailed chemical analysis of the particulate matter (PM) is performed, additional subtle information about the combustion process can be revealed. This paper reports the results of detailed chemical analysis of trace metal in the PM emitted from a single cylinder heavy-duty diesel engine. The trace metal concentrations are used as an indicator of oil consumption. Two techniques were used to make the trace metal concentration measurements. PM was captured on filters and trace metals were quantified with an Inductively Coupled Plasma Mass Spectrometer (ICPMS), and also an Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) was used to perform particle size and composition measurements in real time.

Local deposition of thermal energy can be used to assist the combustion process of low cetane number (CN) fuels in compression-ignition engines, here termed energy-assisted compression ignition (EACI). In the current work, a commercial ceramic glow plug, operated beyond its conventional operation range, was used as the ignition assistant (IA) and sensitivity of fuel jet ignition to operation parameters was studied for two fuels using EACI in an optical engine. A design-of-experiments (DoE) study was devised to determine which engine parameters influenced the energy-assisted pilot injection ignition process the most. The DoE was constructed with four parameters: injection pressure, injected mass, injection timing, and ignition assistant temperature. The fuels used were F24 (Jet-A with military additives) with a cetane number of 48 and a cetane number 35 fuel mixture consisting of 60% F24 and 40% of an alcohol-to-jet fuel (ATJ), blended on a volumetric basis.

The combined impacts of engine speed and fuel reactivity on energy-assisted compression-ignition (EACI) combustion using a commercial off-the-shelf (COTS) ceramic glow plug for low-load operation werexxz investigated. The COTS glow plug, used as the ignition assistant (IA), was overdriven beyond its conventional operation range. Engine speed was varied from 1200 RPM to 2100 RPM. Three fuel blends consisting of a jet-A fuel with military additives (F24) and a low cetane number alcohol-to-jet (ATJ) sustainable aviation fuel (SAF) were tested with cetane numbers (CN) of 25.9, 35.5, and 48.5. The ranges of engine speed and fuel cetane numbers studied are significantly larger than those in previous studies of EACI or glow-plug assisted combustion, and the simultaneous variation of engine speed and fuel reactivity are unique to this work. For each speed and fuel, a single-injection of fixed mass was used and the start of injection (SOI) was swept for each IA power.

Airborne compression-ignition engine operations differ significantly from those in ground vehicles, both in mission requirements and in operating conditions. Unique challenges exist in the aviation space, and electrification technologies originally developed for ground applications may be leveraged to address these considerations. One such technology, electrically assisted turbochargers (EATs), have the potential to address the following: increase the maximum system power output, directly control intake manifold air pressure, and reignite the engine at altitude conditions in the event of an engine flame-out. Sea-level experiments were carried out on a two-liter, four-cylinder compression-ignition engine with a commercial-off-the-shelf EAT that replaced the original turbocharger. The objective of these experiments was to demonstrate the technology, assess the performance, and evaluate control methods at sea level prior to altitude experimentation.