NOx Reduction from Diesel Combustion Using Pilot Injection with High Pressure Fuel Injection

This paper describes the research carried out in the European Commission co-funded project LEMCOTEC (Low Emission Core Engine Technology), which is aiming at a significant increase of the engine overall pressure ratio. The technical work is split in four technical sub-projects on ultra-high pressure ratio compressors, lean combustion and fuel injection, structures and thermal management and engine performance assessment. The technology will be developed at subsystem and component level and validated in test rigs up to TRL5. The developed technologies will be assessed using three generic study engines (i.e. regional turbofan, mid-size open rotor, and large turbofan) representing about 90% of the expected future commercial aero-engine market. Two additional study engines from the previous NEWAC project will be used for comparison. These are based on intercooled and intercooled-recuperated future engine concepts. The compressor work is targeting efficiency, stability margin and flow capacity by improved aerodynamic design. High-pressure and intermediate-pressure compressors are addressed. The mechanical and thermo-mechanical functions, including the variable-stator-systems, will be improved. Axial-centrifugal compressors with impeller and centrifugal diffuser are under investigation too. Three lean burn fuel injection systems are developed to match the technology to the corresponding engine pressure levels. These are the PERM (Partially Evaporating Rapid Mixing), the MSFI (Multiple Staged Fuel Injection) and the advanced LDI (Lean Direct Injection) combustion systems. The air flow and combustion systems are investigated. The fuel control systems are adapted to the requirements of the ultra-high pressure engines with lean fuel injection. Combustor-turbine interaction will be investigated. A fuel system analysis will be performed using CFD methods. Improved structural design and thermal management is required to reduce the losses and to reduce component weight. The application of new materials and manufacturing processes, including welding and casting aspects, will be investigated. The aim is to reduce the cooling air requirements and improve turbine aerodynamics to support the high-pressure engine cycles. The final objective is to have innovative ultra-high pressure-ratio core-engine technologies successfully validated at subsystem and component level. Increasing the thermal efficiency of the engine cycles relative to year 2000 in-service engines with OPR of up to 70 (at max. condition) is an enabler and key lever of the core-engine technologies to achieve and even exceed the ACARE 2020 targets on CO2, NOx and other pollutant emissions: • 20 to 30 % CO2 reduction at the engine level, exceeding both, the ACARE 15 to 20% CO2 reduction target for the engine and subsequently the overall 50% committed CO2 and the fuel burn reduction target on system level (including the contributions from operations and airframe improvements), • 65 to 70 % NOx reduction at the engine level (CAEP/2) to attain and exceed the ACARE objective of 80% overall NOx reduction (including the contributions from both, operational efficiency and airframe improvement), reduction of other emissions (CO, UHC and smoke/particulates) and • Reduction of the propulsion system weight (engine including nacelle without pylon).

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Effect of Premixed Fuel Preparation for Partially Premixed Combustion With a Low Octane Gasoline on a Light-Duty Multicylinder Compression Ignition Engine

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4030281 ◽

2015 ◽

Vol 137 (11) ◽

Cited By ~ 15

Author(s):

Adam B. Dempsey ◽

Scott Curran ◽

Robert Wagner ◽

William Cannella

Keyword(s):

High Pressure ◽

Thermal Efficiency ◽

Fuel Injection ◽

Premixed Combustion ◽

Injection System ◽

Injection Timing ◽

Pilot Injection ◽

Compression Ignition ◽

Partially Premixed Combustion ◽

Injection Strategies

Gasoline compression ignition (GCI) concepts with the majority of the fuel being introduced early in the cycle are known as partially premixed combustion (PPC). Previous research on single- and multicylinder engines has shown that PPC has the potential for high thermal efficiency with low NOx and soot emissions. A variety of fuel injection strategies have been proposed in the literature. These injection strategies aim to create a partially stratified charge to simultaneously reduce NOx and soot emissions while maintaining some level of control over the combustion process through the fuel delivery system. The impact of the direct injection (DI) strategy to create a premixed charge of fuel and air has not previously been explored, and its impact on engine efficiency and emissions is not well understood. This paper explores the effect of sweeping the direct injected pilot timing from −91 deg to −324 deg ATDC, which is just after the exhaust valve closes (EVCs) for the engine used in this study. During the sweep, the pilot injection consistently contained 65% of the total fuel (based on command duration ratio), and the main injection timing was adjusted slightly to maintain combustion phasing near top dead center. A modern four cylinder, 1.9 l diesel engine with a variable geometry turbocharger (VGT), high pressure common rail injection system, wide included angle injectors, and variable swirl actuations was used in this study. The pistons were modified to an open bowl configuration suitable for highly premixed combustion modes. The stock diesel injection system was unmodified, and the gasoline fuel was doped with a lubricity additive to protect the high pressure fuel pump and the injectors. The study was conducted at a fixed speed/load condition of 2000 rpm and 4.0 bar brake mean effective pressure (BMEP). The pilot injection timing sweep was conducted at different intake manifold pressures, swirl levels, and fuel injection pressures. The gasoline used in this study has relatively high fuel reactivity with a research octane number of 68. The results of this experimental campaign indicate that the highest brake thermal efficiency (BTE) and lowest emissions are achieved simultaneously with the earliest pilot injection timings (i.e., during the intake stroke).

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Analysis of the Influence of Pilot Injection Timing on Diesel Combustion in an Optical Engine by the Two-Color Method

Volume 1: Large Bore Engines; Advanced Combustion; Emissions Control Systems; Instrumentation, Controls, and Hybrids ◽

10.1115/icef2013-19104 ◽

2013 ◽

Cited By ~ 2

Author(s):

Weilin Zeng ◽

Xu He ◽

Senjia Jin ◽

Hai Liu ◽

Xiangrong Li ◽

...

Keyword(s):

Ignition Delay ◽

High Speed ◽

Fuel Injection ◽

Injection System ◽

High Speed Photography ◽

Injection Timing ◽

Pilot Injection ◽

Diesel Combustion ◽

Optical Engine ◽

Combustion Duration

High-speed photography, two-color method, and thermodynamic analysis have been used to improve understanding of the influence of pilot injection timing on diesel combustion in an optical engine equipped with an electronically-controlled, common rail, high-pressure fuel injection system. The tests were performed at four different pilot injection timings (30 degree, 25 degree, 20 degree, and 15 degree CA BTDC) with the same main injection timing (5 degree CA BTDC), and under 100MPa injection pressure. The engine speed was selected at 1200 rev/min, and the whole injection mass was fixed as 27.4 mg/stroke. The experimental results showed that the pilot injection timing had a strong influence on ignition delay and combustion duration: advancing the pilot injection timing turned to prolong the ignition delay and shorten the combustion duration. The combustion images indicated that when pilot injection was advanced, the area of luminous flames decreased. The results of two-color method suggested pilot injection timing significantly impacted both the soot temperature distribution and soot concentration (KL factor) within the combustion chamber. 30 degree CA BTDC was the optimal pilot injection timing for in-cylinder soot reduction.

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