71 results found
Hamzehloo A, Aleiferis PG, 2013, Computational Study of Hydrogen Direct Injection for Internal Combustion Engines, SAE Technical Paper Series, Vol: 2013, ISSN: 0148-7191
Hydrogen has been largely proposed as a possible fuel forinternal combustion engines. The main advantage of burninghydrogen is the absence of carbon-based tailpipe emissions.Hydrogen’s wide flammability also offers the advantage ofvery lean combustion and higher engine efficiency thanconventional carbon-based fuels. In order to avoid abnormalcombustion modes like pre-ignition and backfiring, as well asair displacement from hydrogen’s large injected volume percycle, direct injection of hydrogen after intake valve closure isthe preferred mixture preparation method for hydrogenengines. The current work focused on computational studies ofhydrogen injection and mixture formation for direct-injectionspark-ignition engines. Hydrogen conditions at the injector’snozzle exit are typically sonic. Initially the characteristics ofunder-expanded sonic hydrogen jets were investigated in aquiescent environment using both Reynolds-Averaged NavierStokes(RANS) and Large-Eddy Simulation (LES) techniques.Various injection conditions were studied, including areference case from the literature. Different nozzle geometrieswere investigated, including a straight nozzle with fixed crosssection and a stepped nozzle design. LES captured details ofthe expansion shocks better than RANS and demonstratedseveral aspects of hydrogen’s injection and mixing. Incylindersimulations were also performed with a side 6-holeinjector using 70 and 100 bar injection pressure. Injectiontiming was set to just after inlet valve closure with duration of6 μs and 8 μs, leading to global air-to-fuel equivalence ratios typically in the region of 0.2–0.4. The engine intake airpressure was set to 1.5 bar absolute to mimic boostedoperation. It was observed that hydrogen jet wall impingementwas always prominent. Comparison with non-fuelled engineconditions demonstrated the degree of momentum exchangebetween in-cylinder hydrogen injection and air motion. LEShighlighted details of hydroge
Butcher AJ, Aleiferis PG, Richardson D, 2013, Development of a Real-Size Optical Injector Nozzle for Studies of Cavitation, Spray Formation and Flash-Boiling at Conditions Relevant to Direct-Injection Spark-Ignition Engines, International Journal of Engine Research, Vol: 14, Pages: 557-577, ISSN: 1468-0874
High-pressure multi-hole injectors for direct-injection spark-ignition engines have shown enhanced fuel atomisation and flexibility in fuel targeting by selection of the number and angle of the nozzle holes. The nozzle internal flow is known to influence the characteristics of spray formation; hence, understanding its mechanisms is essential for improving mixture preparation. However, currently, no data exist for fuel temperatures representative of real engine operation, especially at low-load high-temperature conditions with early injection strategies that can lead to phase change due to fuel flash-boiling upon injection. This challenge is further complicated by the predicted fuel stocks, which may include new (e.g. bio-derived) components. The physical/chemical properties of such components can differ markedly from gasoline, and it is important to have the capability to study their effects on in-nozzle flow and spray formation, taking under consideration their different chemical compatibilities with optical materials as well. The current article presents the design and development of a real-size quartz optical nozzle, 200 µm in diameter, suitable for high-temperature applications and also compatible with new fuels such as alcohols. First, the internal geometry of a typical real multi-hole injector was analysed by electron microscopy. Mass flow was measured, and relevant fluid mechanics dimensionless parameters were derived. Laser and mechanical drilling of the quartz nozzle holes were compared. Abrasive flow machining of the optical nozzles was also performed and analysed by microscopy in comparison to the real injector. Initial validation results with a high-speed camera showed successful imaging of microscopic in-nozzle flow and cavitation phenomena, coupled to downstream spray formation, under a variety of conditions including high fuel temperature flash-boiling effects. The current work used gasoline and iso-octane to provide proof-of-concept imag
Cairns A, Zhao H, Todd AR, et al., 2013, A Study of Mechanical Variable Valve Operation with Gasoline-Alcohol Fuels in a Spark-Ignition Engine, Fuel, Pages: 802-813, ISSN: 1873-7153
Aleiferis PG, van Romunde ZR, 2013, An Analysis of Spray Development with iso-Octane, n-Pentane, Gasoline, Ethanol and n-Butanol from a Multi-Hole Injector Under Hot Fuel Conditions, Fuel, Vol: 105, Pages: 143-168, ISSN: 0016-2361
High-pressure multi-hole injectors for direct-injection spark-ignition engines offer some great benefits in terms of fuel atomisation, as well as flexibility in fuel targeting by selection of the number and angle of the nozzle’s holes. However, very few data exist for injector-body temperatures representative of engine operation with various fuels, especially at low-load conditions with early injection strategies that can also lead to phase change due to fuel flash boiling upon injection. The challenge is further complicated by the predicted fuel stocks which will include a significant bio-derived component presenting the requirement to manage fuel flexibility. The physical/chemical properties of bio-components, like various types of alcohols, can differ markedly from gasoline and it is important to study their effects in direct comparison to liquid hydrocarbons. This work outlines results from an optical investigation (high-speed imaging and droplet sizing) into the effects of fuel properties, temperature and pressure conditions on the extent of spray formation. Specifically, gasoline, iso-octane, n-pentane, ethanol and n-butanol were tested at 20, 50, 90 and 120 °C injector body temperatures for ambient pressures of 0.5 bar and 1.0 bar in order to simulate early homogeneous injection strategies for part-load and wide open throttle engine operation; some test were also carried out at 180 °C, 0.3 bar. Droplet sizing was also performed for gasoline, iso-octane and n-pentane using Phase Doppler and Laser Diffraction techniques in order to understand the effects of low- and high-volatility components on the atomisation of the multi-component gasoline. The boiling points and distillation curves of all fuels, their vapour pressures and bubble points, as well as density, viscosity and surface tension were obtained and the Reynolds, Weber and Ohnesorge numbers were considered in the analysis.
Aleiferis PG, Serras-Pereira J, Richardson D, 2013, Characterisation of Flame Development with Ethanol, Butanol, iso-Octane, Gasoline and Methane in a Direct-Injection Spark-Ignition Engine, Fuel, Vol: 109, Pages: 256-278, ISSN: 0016-2361
Research into novel internal combustion engines requires consideration of the diversity in future fuels that may contain significant quantities of bio-components in an attempt to reduce CO2 emissions from vehicles and contribute to energy sustainability. However, most biofuels have different chemical and physical properties to those of typical hydrocarbons; these can lead to different mechanisms of mixture preparation and combustion. The current paper presents results from an optical study of combustion in a direct-injection spark-ignition research engine with gasoline, iso-octane, ethanol and butanol fuels injected from a centrally located multi-hole injector. Methane was also employed by injecting it into the inlet plenum of the engine to provide a benchmark case for well-mixed ‘homogeneous’ charge preparation. Crank-angle resolved flame chemiluminescence images were acquired and post-processed for a series of consecutive cycles for each fuel, in order to calculate in-cylinder rates of flame growth and motion. In-cylinder pressure traces were used for heat release analysis and for comparison with the image-processing results. All tests were performed at 1500 RPM with 0.5 bar intake plenum pressure. Stoichiometric (ϕ = 1.0) and lean (ϕ = 0.83) conditions were considered. The combustion characteristics were analysed with respect to laminar and turbulent burning velocities obtained from combustion bombs in the literature and from traditional combustion diagrams in order to bring all data into the context of current theories and allow insights by making comparisons were appropriate.
Serras-Pereira J, Aleiferis PG, Richardson D, 2012, An Analysis of the Combustion Behavior of Ethanol, Butanol, Iso-Octane, Gasoline, and Methane in a Direct-Injection Spark-Ignition Research Engine, Combustion Science and Technology, Vol: 185, Pages: 484-513, ISSN: 0010-2202
Future automotive fuels are expected to contain significant quantities of bio-components. This poses a great challenge to the designers of novel low-CO2 internal combustion engines because biofuels have very different properties to those of most typical hydrocarbons. The current article presents results of firing a direct-injection spark-ignition optical research engine on ethanol and butanol and comparing those to data obtained with gasoline and iso-octane. A multihole injector, located centrally in the combustion chamber, was used with all fuels. Methane was also employed by injecting it into the inlet plenum to provide a benchmark case for well-mixed “homogeneous” charge preparation. The study covered stoichiometric and lean mixtures (λ = 1.0 and λ = 1.2), various spark advances (30–50° CA), a range of engine temperatures (20–90°C), and diverse injection strategies (single and “split” triple). In-cylinder gas sampling at the spark-plug location and at a location on the pent-roof wall was also carried out using a fast flame ionization detector to measure the equivalence ratio of the in-cylinder charge and identify the degree of stratification. Combustion imaging was performed through a full-bore optical piston to study the effect of injection strategy on late burning associated with fuel spray wall impingement. Combustion with single injection was fastest for ethanol throughout 20–90°C, but butanol and methane were just as fast at 90°C; iso-octane was the slowest and gasoline was between iso-octane and the alcohols. At 20°C, λ at the spark plug location was 0.96–1.09, with gasoline exhibiting the largest and iso-octane the lowest value. Ethanol showed the lowest degree of stratification and butanol the largest. At 90°C, stratification was lower for most fuels, with butanol showing the largest effect. The work output with triple injection was marginally higher for the alcoh
Aleiferis PG, Rosati MF, 2012, Controlled Autoignition of Hydrogen in a Direct-Injection Optical Engine, Combustion and Flame, Vol: 159, Pages: 2500-2515, ISSN: 0010-2180
Research into novel internal combustion engines requires consideration of the diversity in future fuels in an attempt to reduce drastically CO2 emissions from vehicles and promote energy sustainability. Hydrogen has been proposed as a possible fuel for future internal combustion engines and can be produced from renewable sources. Hydrogen’s wide flammability range allows higher engine efficiency than conventional fuels with both reduced toxic emissions and no CO2 gases. Most previous work on hydrogen engines has focused on spark-ignition operation. The current paper presents results from an optical study of controlled autoignition (or homogeneous charge compression ignition) of hydrogen in an engine of latest spark-ignition pentroof combustion chamber geometry with direct injection of hydrogen (100 bar). This was achieved by a combination of inlet air preheating in the range 200–400 °C and residual gas recirculated internally by negative valve overlap. Hydrogen fuelling was set to various values of equivalence ratio, typically in the range ϕ = 0.40–0.63. Crank-angle resolved flame chemiluminescence images were acquired for a series of consecutive cycles at 1000 RPM in order to calculate in-cylinder rates of flame expansion and motion. Planar Laser Induced Fluorescence (LIF) of OH was also applied to record more detailed features of the autoignition pattern. Single and double (i.e. ‘split’ per cycle) hydrogen injection strategies were employed in order to identify the effect of mixture preparation on autoignition’s timing and spatial development. An attempt was also made to review relevant in-cylinder phenomena from the limited literature on hydrogen-fuelled spark-ignition optical engines and make comparisons were appropriate.
Aleiferis PG, Rosati MF, 2011, Flame Chemiluminescence and OH LIF Imaging in a Hydrogen-Fuelled Spark-Ignition engine, International Journal of Hydrogen Energy, Vol: 37, Pages: 1797-1812, ISSN: 0360-3199
Research into novel internal combustion engines requires consideration of the diversity in future fuels in an attempt to reduce drastically CO2 emissions from vehicles and promote energy sustainability. Hydrogen has been proposed as a possible fuel for future internal combustion engines. Hydrogen’s wide flammability range allows higher engine efficiency with much leaner operation than conventional fuels, for both reduced toxic emissions and no CO2 gases. This paper presents results from an optical study of combustion in a spark-ignition research engine running with direct injection and port injection of hydrogen. Crank-angle resolved flame chemiluminescence images were acquired and post-processed for a series of consecutive cycles in order to calculate in-cylinder rates of flame growth. Laser induced fluorescence of OH was also applied on an in-cylinder plane below the spark plug to record detailed features of the flame front for a series of engine cycles. The tests were performed at various air-to-fuel ratios, typically in a range of φ = 0.50–0.83 at 1000 RPM with 0.5 bar intake pressure. The engine was also run with gasoline in direct-injection and port-injection modes to compare with the operation on hydrogen. The observed combustion characteristics were analysed with respect to laminar and turbulent burning velocities, as well as flame stretch. An attempt was also made to review relevant hydrogen work from the limited literature on the subject and make comparisons were appropriate.
Birgel A, Ladommatos N, Aleiferis P, et al., 2011, Investigations on Deposit Formation in the Holes of Diesel Injector Nozzles, SAE International Journal of Fuels and Lubricants, Vol: 5, Pages: 123-131, ISSN: 1946-3960
Serras-Pereira J, Aleiferis PG, Richardson D, 2011, Imaging and Heat Flux Measurements of Wall Impinging Sprays of Hydrocarbons and Alcohols in a Direct-Injection Spark-Ignition Engine, Fuel, Vol: 91, Pages: 264-297, ISSN: 0016-2361
The latest generation of fuel systems for direct-injection spark-ignition engines uses injection nozzles that accommodate a number of holes with various angles in order to offer flexibility in in-cylinder fuel targeting over a range of engine operating conditions. However, the high-injection pressures that are needed for efficient fuel atomisation can lead to deteriorating effects with regards to engine exhaust emissions (e.g. unburned hydrocarbons and particulates) from liquid fuel impingement onto the piston and liner walls. Eliminating such deteriorating effects requires fundamental understanding of in-cylinder spray development processes, taking also into account the diversity of future commercial fuels that can contain significant quantities of bio-components with very different chemical and physical properties to those of typical liquid hydrocarbons. This paper presents high-speed imaging results of spray impingement onto the liner of a direct-injection spark-ignition engine, as well as crank-angle resolved wall heat flux measurements at the observed locations of fuel impingement for detailed characterisation of levels and timing of impingement. The tests were performed in a running engine at 1500 RPM primarily at low load (0.5 bar intake pressure) using 20, 50 and 90 °C engine temperatures. Gasoline, iso-Octane, Butanol, Ethanol and a blend of 10% Ethanol with 90% Gasoline (E10) were used to encompass a range of current and future fuel components for spark-ignition engines. The collected data were analysed to extract mean and standard deviation statistics of spray images and heat flux signals. The results were also interpreted with reference to physical prop
Malcolm JS, Behringer MK, Aleiferis PG, et al., 2011, Characterisation of Flow Structures in a Direct-Injection Spark-Ignition Engine using PIV, LDV and CFD, SAE Technical Paper Series, ISSN: 0148-7191
Aleiferis PG, Kolokotronis D, Hardalupas Y, et al., 2010, Experimental Investigation of Cavitation in Gasoline Injectors, SAE Technical Paper Series, ISSN: 0148-7191
Aleiferis PG, Serras-Pereira J, Augoye A, et al., 2010, Effect of Fuel Temperature on In-Nozzle Cavitation and Spray Formation of Liquid Hydrocarbons and Alcohols from a Real-Size Optical Injector for Direct-Injection Spark-Ignition Engines, International Journal of Heat and Mass Transfer, Vol: 53, Pages: 4588-4606, ISSN: 0017-9310
High-pressure multi-hole injectors for direct-injection spark-ignition engines offer some great benefits in terms of fuel atomisation, as well as flexibility in fuel targeting by selection of the number and angle of the nozzle holes. The flow through the internal passages of injectors is known to influence the characteristics of spray formation. In particular, understanding how in-nozzle cavitation phenomena can be used to improve atomisation is essential for improving mixture preparation quality under homogeneous or stratified engine operating conditions. However, no data exist for injector body temperatures representative of real engine operation, especially at low-load conditions with early injection strategies that can also lead to phase change due to fuel flash-boiling upon injection. This challenge is further complicated by the predicted fuel stocks which will include a significant bio-derived component presenting the requirement to manage fuel flexibility. The physical/chemical properties of bio-components, like various types of alcohols, can differ markedly from gasoline and it is important to study their effects. This work outlines results from an experimental imaging investigation into the effects of fuel properties, temperature and pressure conditions on the extent of cavitation, flash-boiling and, subsequently, spray formation. This was achieved by the use of real-size transparent nozzles, replica of an injector from a modern direct-injection spark-ignition combustion system. Gasoline, iso-octane, n-pentane, ethanol and butanol were used at 20, 50 and 90 °C injector body temperatures for ambient pressures of 0.5 bar and 1.0 bar in order to simulate early homogeneous injection strategies for part-load and wide open throttle engine operation. The fuel matrix also included a blend of 10% ethanol with 90% gasoline (E10) because the vapour pressure of E10 is higher than the vapour pressure of either ethanol or gasoline and the distillation curve of E10 re
Cairns A, Todd AR, Fraser N, et al., 2010, A Study of Alcohol Blended Fuels in an Unthrottled Single Cylinder Spark Ignition Engine, SAE Technical Paper Series, ISSN: 0148-7191
This work involved study of the effects of alcohol blends on combustion, fuel economy and emissions in a single cylinder research engine equipped with a mechanical fully variable valvetrain on the inlet and variable valve timing on the exhaust. A number of splash blends of gasoline, iso-octane, ethanol and butanol were examined during port fuel injected early inlet valve closing operation, both with and without variable valve timing. Under low valve overlap conditions, it was apparent that the inlet valve durations/lifts required for full unthrottled operation were remarkably similar for the wide range of blends studied. However, with high valve overlap differences in burning velocities and internal EGR tolerances warranted changes in these valve settings. In turn, it was concluded that high ethanol content blends facilitated minimum throttling at the inlet valve itself and the largest relative savings in terms of fuel consumption, engine-out emissions of NOx and (corrected) unburned hydrocarbons.
Serras-Pereira J, van Romunde Z, Aleiferis PG, et al., 2010, Cavitation, Primary Break-up and Flash Boiling of Gasoline, iso-Octane and n-Pentane with a Real-Size Optical Direct-Injection Nozzle, Fuel, Vol: 89, Pages: 2592-2607, ISSN: 0016-2361
Improvements to the direct-injection spark-ignition combustion system are necessary if the potential reductions in fuel consumption and emissions are to be fully realized in the near future. One critical link in the optimization process is the design and performance of the injectors used for fuel atomization. Multi-hole injectors have become the state-of-the-art choice for gasoline direct-injection engines due to their flexibility in fuel targeting by selection of the number and angle of the nozzle holes, as well as due to their demonstrated stability of performance under a wide range of operating conditions. Recently there has been increased attention devoted to the study of the flow through the internal passages of injectors because of the presence of particular fluid phenomena, such as large-scale vortical motion and cavitation patterns, which have been shown to influence the characteristics of primary break-up. Understanding how cavitation can be used to improve spray atomisation is essential for optimizing mixture preparation quality under early injection and stratified engine operating conditions but currently no data exist for injector-body temperatures representative of real engine operation, particularly at low-load conditions that can also lead to phase change due to fuel flash boiling. This paper outlines results from an experimental imaging investigation into the effects of fuel properties, temperature and pressure conditions on the extent of cavitation, flash boiling and, subsequently, primary break-up. This was achieved by the use of a real-size transparent nozzle of a gasoline injector from a modern direct-injection combustion system. Gasoline, iso-octane and n-pentane fuels were used at 20 and 90 °C injector-body temperatures for ambient pressures of 0.5 and 1.0 bar in order to simulate early homogeneous injection strategies for part-load and wide-open-throttle engine operation.
Aleiferis PG, Serras-Pereira J, van Romunde Z, et al., 2010, Mechanisms of Spray Formation and Combustion from a Multi-Hole Injector with E85 and Gasoline, Combustion and Flame, Vol: 157, Pages: 735-756, ISSN: 0010-2180
The spray formation and combustion characteristics of gasoline and E85 (85% ethanol, 15% gasoline) have been investigated using a multi-hole injector with asymmetric nozzle-hole arrangement. Experiments were carried out in a quiescent optical chamber using high-speed shadowgraphy (9 kHz) to characterise the spray sensitivity to both injector temperature and ambient pressure in the range of 20–120 °C and 0.5, 1.0 bar. Spray-tip penetrations and ‘umbrella’ spray cone angles were calculated for all conditions. Phase Doppler Anemometry was also used to measure droplet sizes in the core of one of the spray plumes, 25 mm below the injector tip. To study the effect of fuel properties on vaporisation and mixture preparation under realistic operating conditions, a separate set of experiments was carried out in a direct-injection spark-ignition optical engine. The engine was run at 1500 RPM under cold and fully warmed-up conditions (20 °C and 90 °C) at part load and full load (0.5 and 1.0 bar intake pressure). Floodlit laser Mie-scattering images of the sprays on two orthogonal planes corresponding to the swirl and tumble planes of in-cylinder flow motion were acquired to study the full injection event and post-injection mixing stage. These were used to make comparisons with the static chamber sprays and to quantify the liquid-to-vapour phase evaporation process for both fuels by calculating the projected ‘footprint’ of the sprays at different conditions. Analysis of the macroscopic structure and turbulent primary break-up properties of the sprays was undertaken in light of jet exit conditions described in terms of non-dimensional numbers. The effects on stoichiometric combustion were investigated by imaging the natural flame chemiluminescence through the engine’s piston crown (swirl plane) and by post-processing to derive flame growth rates and trajectories of flame motion.
Cairns A, Todd AR, Aleiferis PG, et al., 2009, A Comparison of Inlet Valve Operating Strategies in a Single-Cylinder Spark-Ignition Engine, Internal Combustion Engines: Performance, Fuel Economy and Emissions, Pages: 3-17
Rosati MF, Aleiferis PG, 2009, Hydrogen SI and HCCI Combustion in a Direct-Injection Optical Engine, SAE International Journal of Engines, Vol: 2, Pages: 1710-1736, ISSN: 1946-3944
Hydrogen has been largely proposed as a possible alternative fuel for internal combustion engines. Its wide flammability range allows higher engine efficiency with leaner operation than conventional fuels, for both reduced toxic emissions and no CO2 gases. Independently, Homogenous Charge Compression Ignition (HCCI) also allows higher thermal efficiency and lower fuel consumption with reduced NOX emissions when compared to Spark-Ignition (SI) engine operation. For HCCI combustion, a mixture of air and fuel is supplied to the cylinder and autoignition occurs from compression; engine is operated throttle-less and load is controlled by the quality of the mixture, avoiding the large fluid-dynamic losses in the intake manifold of SI engines. HCCI can be induced and controlled by varying the mixture temperature, either by Exhaust Gas Recirculation (EGR) or intake air pre-heating. A combination of HCCI combustion with hydrogen fuelling has great potential for virtually zero CO2 and NOX emissions. Nevertheless, combustion on such a fast burning fuel with wide flammability limits and high octane number implies many disadvantages, such as control of backfiring and speed of autoignition and there is almost no literature on the subject, particularly in optical engines. Experiments were conducted in a single-cylinder research engine equipped with both Port Fuel Injection (PFI) and Direct Injection (DI) systems running at 1000 RPM. Optical access to in-cylinder phenomena was enabled through an extended piston and optical crown. Combustion images were acquired by a high-speed camera at 1° or 2° crank angle resolution for a series of engine cycles. Spark-ignition tests were initially carried out to benchmark the operation of the engine with hydrogen against gasoline. DI of hydrogen after intake valve closure was found to be preferable in order to overcome problems related to backfiring and air displacement from hydrogen’s low density. HCCI combustion of hydrogen was i
Cairns A, Todd AR, Hoffmann H, et al., 2009, Combining Unthrottled Operation with Internal EGR under Port and Central Direct Fuel Injection Conditions in a Single Cylinder SI Engine, SAE Technical Paper Series, ISSN: 0148-7191
van Romunde ZR, Aleiferis PG, 2009, Effect of Operating Conditions and Fuel Volatility on Development and Variability of Sprays from Gasoline Direct-Injection Multi-Hole Injectors, Atomization and Sprays, Vol: 19, Pages: 207-234, ISSN: 1046-5111
Aleiferis PG, van Romunde ZR, Serras-Pereira J, et al., 2009, Spray Development of E85 and Gasoline in a Quiescent Chamber and in a Direct-Injection Spark-Ignition Engine, Fourth International Conference on Thermal Engineering: Theory and Applications
Alelferis PG, Charalambides AG, Hardalupas Y, et al., 2008, The Effect of Axial Charge Stratification and Exhaust Gases on Combustion Development in a Homogeneous Charge Compression Ignition Engine, Proceedings of IMechE, Part D, Journal of Automobile Engineering, Vol: 222, Pages: 2171-2183, ISSN: 0020-3483
Birgel A, Ladommatos N, Aleiferis PG, et al., 2008, Deposit Formation in the Holes of Diesel Injector Nozzles: A Critical Review, SAE Technical Paper Series, ISSN: 0148-7191
Current developments in fuels and emissions regulations are resulting in increasingly severe operating environment for the injection system. Formation of deposits within the holes of the injector nozzle or on the outside of the injector tip may have an adverse effect on overall system performance. This paper provides a critical review of the current understanding of the main factors affecting deposit formation.Two main types of engine test cycles, which attempt to simulate field conditions, are described in the literature. The first type involves cycling between high and low load. The second involves steady state operation at constant speed either at medium or high load.A number of influences on the creation of deposits are identified. This includes fouling through thermal condensation and cracking reactions at nozzle temperatures of around 300°C. Also the design of the injector holes is an influence, because it can influence cavitation. The implosion of cavitation bubbles is believed to limit nozzle deposits. Field and laboratory tests showed that small amounts (around 1ppm) of zinc tend to increase the formation of deposits and are therefore another influence. But it is not clear whether zinc acts catalytically to accelerate deposit formation or if it becomes part of the solid deposits. Bio-diesel has been observed to lead to higher deposit formation in the injector nozzle.The chemical and physical processes that lead to deposit formation are not known or well understood, due to their complexity. A physical mechanism put forward focuses on the role of the residual fuel that remains in the nozzle holes after the end of the injection process.
Serras-Pereira J, Aleiferis PG, Richardson D, et al., 2008, Characteristics of Ethanol, Butanol, Iso-Octane and Gasoline Sprays and Combustion from a Multi-Hole Injector in a DISI Engine, SAE International Journal of Fuels and Lubricants, Vol: 1, Pages: 893-909, ISSN: 1946-3960
Aleiferis PG, Malcolm JS, Cairns A, et al., 2008, An Optical Study of Spray Development and Combustion of Ethanol, iso-Octane and Gasoline in a DISI Engine, SAE Technical Paper Series, ISSN: 0148-7191
Malcolm JS, Aleiferis PG, Cairns A, et al., 2007, A Study of Alcohol Blended Fuels in a New Optical Spark-Ignition Engine, International Conference on Internal Combustion Engines: Performance, Fuel Economy and Emissions, Pages: 223-234
Aleiferis PG, Serras-Pereira J, van Romunde ZR, et al., 2007, Optical Studies of Spray Development in a Quiescent Chamber and in a Direct-Injection Spark-Ignition Engine, International Conference on Internal Combustion Engines: Performance, Fuel Economy and Emissions, Pages: 3-13
Aleiferis PG, Serras-Pereira J, Richardson D, et al., 2007, Spray Development, Flow Interactions and Wall Impingement in a Direct-Injection Spark-Ignition Engine, SAE Technical Paper Series, ISSN: 0148-7191
Aleiferis PG, van Romunde ZR, Cracknell RF, et al., 2007, Effect of Fuel Properties on Spray Development from a Multi-Hole DISI Engine Injector, SAE Transactions, Journal of Engines, Vol: 116, Pages: 1313-1331, ISSN: 0096-736X
Aleiferis PG, Serras-Pereira J, Richardson D, et al., 2007, Mixture Preparation and Combustion Variability in a Spray-Guided DISI Engine, SAE Technical Paper Series, Vol: 116, Pages: 1332-1356, ISSN: 0148-7191
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