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Journal Article

An Assessment of the Influence of Gas Turbine Lubricant Thermal Oxidation Test Method Parameters Towards the Development of a New Engine Representative Laboratory Test Method

2013-12-20
2013-01-9004
In the development of a more accurate laboratory scale method, the ability to replicate the thermal oxidative degradation mechanisms seen in gas turbine lubricants, is an essential requirement. This work describes an investigation into the influence of key reaction parameters and the equipment set up upon extent and mechanism of oil degradation. The air flow rate through the equipment was found to be critical to both degradation rate and extent of volatilization loss from the system. As these volatile species can participate in further reactions, it is important that the extent to which they are allowed to leave the test system is matched, where possible, to the conditions in the gas turbine. The presence of metal specimens was shown to have a small influence on the rate of degradation of the lubricant. Loss of metal from the copper and silver specimens due to the mild corrosive effect of the lubricant was seen.
Journal Article

Experimental Investigation of Different Blends of Diesel and Gasoline (Dieseline) in a CI Engine

2014-10-13
2014-01-2686
Combustion behaviour and emissions characteristics of different blending ratios of diesel and gasoline fuels (Dieseline) were investigated in a light-duty 4-cylinder compression-ignition (CI) engine operating on partially premixed compression ignition (PPCI) mode. Experiments show that increasing volatility and reducing cetane number of fuels can help promote PPCI and consequently reduce particulate matter (PM) emissions while oxides of nitrogen (NOx) emissions reduction depends on the engine load. Three different blends, 0% (G0), 20% (G20) and 50% (G50) of gasoline mixed with diesel by volume, were studied and results were compared to the diesel-baseline with the same combustion phasing for all experiments. Engine speed was fixed at 1800rpm, while the engine load was varied from 1.38 to 7.85 bar BMEP with the exhaust gas recirculation (EGR) application.
Journal Article

The Use of a Partial Flow Filter to Assist the Diesel Particulate Filter and Reduce Active Regeneration Events

2014-10-13
2014-01-2806
This study investigates the potential of using a partial flow filter (PFF) to assist a wall flow diesel particulate filter (DPF) and reduce the need for active regeneration phases that increase engine fuel consumption. First, the filtration efficiency of the PFF was studied at several engine operating conditions, varying the filter space velocity (SV), through modification of the exhaust gas flow rate, and engine-out particulate matter (PM) concentration. The effects of these parameters were studied for the filtration of different particle size ranges (10-30 nm, 30-200 nm and 200-400 nm). For the various engine operating conditions, the PFF showed filtration efficiency over 25% in terms of PM number and mass. The PFF filtration behaviour was also investigated at idle engine operation producing a high concentration of nuclei particulates for which the filter was able to maintain 60% filtration efficiency.
Technical Paper

Experimental Investigation of Injection Pressure Fluctuations Employing Alternative Fuels

2020-09-15
2020-01-2122
Injection pressure oscillations are proven to determine considerable deviations from the expected mass flow rate, leading to the jet velocities non-uniformity, which in turn implies the uneven spatial distribution of A/F ratio. Furthermore, once the injector is triggered, these oscillations might lead the rail pressure to experience a decreasing stage, to the detriment of spray penetration length, radial propagation and jet break-up timing. This has urged the research community to develop models predicting injection-induced pressure fluctuations within the rail. Additionally, several devices have been designed to minimize and eliminate such fluctuations. However, despite the wide literature dealing with the injection-induced pressure oscillations, many aspects remain still unclear. Moreover, the compulsory compliance with environmental regulations has shifted focus onto alternative fuels, which represent a promising pathway for sustainable vehicle mobility.
Journal Article

The Effect of Exhaust Throttling on HCCI - Alternative Way to Control EGR and In-Cylinder Flow

2008-06-23
2008-01-1739
Homogeneous Charge Compression Ignition (HCCI) has emerged as a promising technology for reduction of exhaust emissions and improvement of fuel economy of internal combustion engines. There are generally two proposed methods of realizing the HCCI operation. The first is through the control of gas temperature in the cylinder and the second is through the control of chemical reactivity of the fuel and air mixture. EGR trapping, i.e., recycling a large quantity of hot burned gases by using special valve-train events (e.g. negative valve overlap), seems to be practical for many engine configurations and can be combined with any of the other HCCI enabling technologies. While this method has been widely researched, it is understood that the operating window of the HCCI engine with negative valve overlap is constrained, and the upper and lower load boundaries are greatly affected by the in-cylinder temperature.
Journal Article

Dual-Injection as a Knock Mitigation Strategy Using Pure Ethanol and Methanol

2012-04-16
2012-01-1152
For spark ignition (SI) engines, the optimum spark timing is crucial for maximum efficiency. However, as the spark timing is advanced, so the propensity to knock increases, thus compromising efficiency. One method to suppress knock is to use high octane fuel additives. However, the blend ratio of these additives cannot be varied on demand. Therefore, with the advent of aggressive downsizing, new knock mitigation techniques are required. Fortuitously, there are two well-known lower alcohols which exhibit attractive knock mitigation properties: ethanol and methanol. Both not only have high octane ratings, but also result in greater charge-cooling than with gasoline. In the current work, the authors have exploited these attractive properties with the dual-injection, or the dual-fuel concept (gasoline in PFI and fuel additive in DI) using pure ethanol and methanol.
Journal Article

Effects of Combustion Phasing, Injection Timing, Relative Air-Fuel Ratio and Variable Valve Timing on SI Engine Performance and Emissions using 2,5-Dimethylfuran

2012-04-16
2012-01-1285
Ethanol has long been regarded as the optimal gasoline-alternative biofuel for spark-ignition (SI) engines. It is used widely in Latin and North America and is increasingly accepted as an attractive option across Europe. Nevertheless, its low energy density requires a high rate of manufacture; in areas which are deficient of arable land, such rates might prove problematic. Therefore, fuels with higher calorific values, such as butanol or 2,5-dimethylfuran (DMF) deserve consideration; a similar yield to ethanol, in theory, would require much less land. This report addresses the suitability of DMF, to meet the needs as a biofuel substitute for gasoline in SI engines, using ethanol as the biofuel benchmark. Specific attention is given to the sensitivity of DMF to various engine control parameters: combustion phasing (ignition timing), injection timing, relative air-fuel ratio and valve timing (intake and exhaust).
Journal Article

Interrogating the surface: the effect of blended diesel fuels on lubricity

2011-08-30
2011-01-1940
The lubricating properties of two sustainable alternative diesels blended with ultra low sulphur diesel (ULSD) were investigated. The candidate fuels were a biodiesel consisting of fatty acid methyl esters derived from rapeseed (RME) and gas-to-liquid (GTL). Lubricity tests were conducted on a high frequency reciprocating rig (HFRR). The mating specimen surfaces were analysed using optical microscopy and profilometery for wear scar diameters and profiles respectively. Microscopic surface topography and deposit composition was evaluated using a scanning electronic microscope (SEM) with an energy dispersive spectrometer (EDS). Like all modern zero sulphur diesel fuel (ZSD), GTL fuels need a lubricity agent to meet modern lubricity specifications. It has been proven that GTL responds well to typical lubricity additives in the marketplace.
Journal Article

An Investigation into the Characteristics of DISI Injector Deposits Using Advanced Analytical Methods

2014-10-13
2014-01-2722
There is an increasing recognition of injector deposit (ID) formation in fuel injection equipment as direct injection spark ignition (DISI) engine technologies advance to meet increasingly stringent emission legislation and fuel economy requirements. While it is known that the phenomena of ID in DISI engines can be influenced by changes in fuel composition, including increasing usage of aliphatic alcohols and additive chemistries to enhance fuel performance, there is however still a great deal of uncertainty regarding the physical and chemical structure of these deposits, and the mechanisms of deposit formation. In this study, a mechanical cracking sample preparation technique was developed to assess the deposits across DISI injectors fuelled with gasoline and blends of 85% ethanol (E85).
Journal Article

Low Ambient Temperature Effects on a Modern Turbocharged Diesel engine running in a Driving Cycle

2014-10-13
2014-01-2713
Engine transient operation has attracted a lot of attention from researchers due to its high frequency of occurrence during daily vehicle operation. More emissions are expected compared to steady state operating conditions as a result of the turbo-lag problem. Ambient temperature has significant influences on engine transients especially at engine start. The effects of ambient temperature on engine-out emissions under the New European Driving Cycle (NEDC) are investigated in this study. The transient engine scenarios were carried out on a modern 3.0 L, V6 turbocharged common rail diesel engine fuelled with winter diesel in a cold cell within the different ambient temperature ranging between +20 °C and −7 °C. The engine with fuel, coolant, combustion air and lubricating oil were soaked and maintained at the desired test temperatures during the transient scenarios.
Journal Article

High Speed Imaging Study on the Spray Characteristics of Dieseline at Elevated Temperatures and Back Pressures

2014-04-01
2014-01-1415
Dieseline combustion as a concept combines the advantages of gasoline and diesel by offline or online blending the two fuels. Dieseline has become an attractive new compression ignition combustion concept in recent years and furthermore an approach to a full-boiling-range fuel. High speed imaging with near-parallel backlit light was used to investigate the spray characteristics of dieseline and pure fuels with a common rail diesel injection system in a constant volume vessel. The results were acquired at different blend ratios, and at different temperatures and back pressures at an injection pressure of 100MPa. The penetrations and the evaporation states were compared with those of gasoline and diesel. The spray profile was analyzed in both area and shape with statistical methods. The effect of gasoline percentage on the evaporation in the fuel spray was evaluated.
Technical Paper

Performance, Emissions and Exhaust-Gas Reforming of an Emulsified Fuel: A Comparative Study with Conventional Diesel Fuel

2009-06-15
2009-01-1809
The fuel reforming technology has been extensively investigated as a way to produce hydrogen on-board a vehicle that can be utilized in internal combustion engines, fuel cells and aftertreatment technologies. Maximization of H2 production in the reforming process can be achieved when there is optimized water (steam) addition for the different reforming temperatures. A way to increase the already available water quantity on-board a vehicle (i.e. exhaust gas water content) is by using emulsified fuel (e.g. water-diesel blend). This study presents the effect of an emulsified diesel fuel (a blend of water and diesel fuel with an organic surfactant to make the mixture stable) on combustion in conjunction with exhaust gas assisted fuel reforming on a compression ignition engine. No engine modification was required to carry out these tests. The emulsified diesel fuel consisted of about 80% (mass basis) of conventional ultra low sulphur diesel (ULSD) fuel and fixed water content.
Technical Paper

Engine Performance and Emissions from Dual Fuelled Engine with In-Cylinder Injected Diesel Fuels and In-Port Injected Bioethanol

2009-06-15
2009-01-1853
Biofuels development and specification are currently driven by the engine (mainly gasoline- and diesel-type) technology, existing fossil fuel specification and availability of feedstock. The ability to use biofuels with conventional fuels without jeopardising the standard fuel specifications is a very effective means for the implementation of these fuels. In this work the effect of dual fuelling with in-cylinder injected ULSD fuel or synthetic second generation biofuels (a Gas-To-Liquid GTL fuel as a surrogate of these biofuels as its composition, specifications and production process are very similar to second generation biofuels) and with inlet port injected bioethanol on the engine performance and emissions were investigated. The introduction of anhydrous bioethanol improved the NOx and smoke emissions, but increased total hydrocarbons and carbon monoxide.
Technical Paper

Effect of Fuel Temperature on Performance and Emissions of a Common Rail Diesel Engine Operating with Rapeseed Methyl Ester (RME)

2009-06-15
2009-01-1896
The paper presents analysis of performance and emission characteristics of a common rail diesel engine operating with RME, with and without EGR. In both cases, the RME fuel was pre-heated in a heat exchanger to control its temperature before being pumped to the common rail. The studied parameters include the in-cylinder pressure history, rate of heat release, mass fraction burned, and exhaust emissions. The results show that when the fuel temperature increases and the engine is operated without EGR, the brake specific fuel consumption (bsfc) decreases, engine efficiency increases and NOx emission slightly decreases. However, when EGR is used while fuel temperature is increased, the bsfc and engine efficiency is independent of fuel temperature while NOx slightly increases.
Technical Paper

A 1D Analysis into the Effect of Variable Valve Timing on HCCI Engine Parameters

2008-10-06
2008-01-2459
The effects of variable intake-valve-timing on the gas exchange process and performance of a 4-valve direct-injection HCCI engine were computationally investigated using a 1D gas dynamics engine cycle simulation code. A non-typical strategy to actuate the pair of intake valves was examined; whereby each valve was assumed to be actuated independently at different timing. Using such an intake valves strategy, the obtained results showed a considerable improvement of the engine parameters such as load and charging efficiency as compared with the typical identical intake valve pair timings case. Additional benefits of minimizing pumping losses and improving the fuel economy were demonstrated with the use of the non-simultaneous actuation of the intake valve pair having the opening timing of the early intake valve coupled with a symmetric degree of crank angle for the timing of exhaust valve closing.
Technical Paper

Diesel Engine Performance and Emissions when First Generation Meets Next Generation Biodiesel

2009-06-15
2009-01-1935
Limits on the total future potential of biodiesel fuel due to the availability of raw materials mean that ambitious 20% fuel replacement targets will need to be met by the use of both first and next generation biodiesel fuels. The use of higher percentage biodiesel blends requires engine recalibration, as it affects engine performance, combustion patterns and emissions. Previous work has shown that the combustion of 50:50 blends of biodiesel fuels (first generation RME and next generation synthetic fuel) can give diesel fuel-like performance (i.e. in-cylinder pressure, fuel injection and heat release patterns). This means engine recalibration can be avoided, plus a reduction in all the regulated emissions. Using a 30% biodiesel blend (with different first and next generation proportions) mixed with Diesel may be a more realistic future fuel.
Technical Paper

Residual Gas Trapping for Natural Gas HCCI

2004-06-08
2004-01-1973
With the high auto ignition temperature of natural gas, various approaches such as high compression ratios and/or intake charge heating are required for auto ignition. Another approach utilizes the trapping of internal residual gas (as used before in gasoline controlled auto ignition engines), to lower the thermal requirements for the auto ignition process in natural gas. In the present work, the achievable engine load range is controlled by the degree of internal trapping of exhaust gas supplemented by intake charge heating. Special valve strategies were used to control the internal retention of exhaust gas. Significant differences in the degree of valve overlap were necessary when compared to gasoline operation at the same speeds and loads, resulting in lower amounts of residual gas observed. The dilution effect of residual gas trapping is hence reduced, resulting in higher NOx emissions for the stoichiometric air/fuel ratio operation as compared to gasoline.
Technical Paper

An Optical Study of DMF and Ethanol Combustion Under Dual-Injection Strategy

2012-04-16
2012-01-1237
The new fuel, 2, 5-dimenthylfuran, known as DMF, captured worldwide attention since the discovery of its new production method. As a potential bio-fuel, DMF is competitive to gasoline in many areas, such as energy density, combustion efficiency and emissions. However, little work has been performed on its unconventional combustion mode. In this work, high speed imaging and thermal investigation are carried out to study DMF and gasoline dual-injection on a single cylinder, direct injection spark ignition optical engine. This dual-injection strategy combines direct injection (DI) and port fuel injection (PFI) simultaneously which means two different fuels can blend in the cylinder with any ratio. It provides a flexible way to use bio-fuels with gasoline. DMF DI with gasoline PFI and ethanol DI with gasoline PFI are studied under different injection proportions (by volume) and IMEPs.
Technical Paper

Understanding the Role of Filtered EGR on PM Emissions

2011-08-30
2011-01-2080
In earlier work we have shown that engine operation with oxygenated fuels (e.g., biodiesel) reduces the particulate matter (PM) emissions and extends the engine tolerance to exhaust gas recirculation (EGR) before it reaches smoke limited conditions. The same result has also been reported when high cetane number fuels such as gas-to-liquid (GTL) are used. A likely mechanism for engine-out particulate growth is the reintroduction of particle nuclei into the cylinder through EGR. These recirculated PM particles serve as sites for further condensation and accumulation promoting larger and greater number of particles. In order to further our understanding of EGR influence on total PM production, a diesel particulate filter (DPF) was integrated into the EGR loop. A PM reduction of approximately 50% (soot) was achieved with diesel fuel through filtered EGR, whilst still maintaining a significant NOX reduction.
Technical Paper

Improving Cold Start and Transient Performance of Automotive Diesel Engine at Low Ambient Temperatures

2016-04-05
2016-01-0826
Ambient temperature has significant impact on engine start ability and cold start emissions from diesel engines. These cold start emissions are accounted for substantial amount of the overall regulatory driving cycle emissions like NEDC or FTP. It is likely to implement the low temperature emissions tests for diesel vehicles, which is currently applicable only for gasoline vehicles. This paper investigates the potential of the intake heating strategy on reducing the driving cycle emissions from the latest generation of turbocharged common rail direct injection diesel engines at low ambient temperature conditions. For this investigation an air heater was installed upstream of the intake manifold and New European Driving Cycle (NEDC) tests were conducted at -7°C ambient temperature conditions for the different intake air temperatures. Intake air heating reduced the cranking time and improved the fuel economy at low ambient temperatures.
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