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D. Richardson - One of the best experts on this subject based on the ideXlab platform.

  • characterisation of flame development with ethanol butanol iso octane gasoline and methane in a direct injection spark ignition engine
    Fuel, 2013
    Co-Authors: P G Aleiferis, J Serraspereira, D. Richardson
    Abstract:

    Abstract 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.

  • 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, 2013
    Co-Authors: D. Richardson
    Abstract:

    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 images of the optical nozzle, and future work will include testing of a range of fuels, some of which will also be bio-derived.

  • a study of Mixture Preparation and pm emissions using a direct injection engine fuelled with stoichiometric gasoline ethanol blends
    Fuel, 2012
    Co-Authors: Longfei Chen, Richard Stone, D. Richardson
    Abstract:

    Abstract The effect of gasoline/ethanol blends in different blending proportions (E0, E10, E20, E50, E70, E85 as #% by volume) on the characteristics of size-resolved particulate number and mass concentrations was investigated in a single-cylinder optical access engine using a differential mobility spectrometer (DMS500) under cold and warm conditions (20 °C, 80 °C) at a stoichiometric condition (1500 rpm, 0.5 bar manifold absolute pressure). The effects on the fuel spray characteristics were also investigated by capturing the injection images and by post-processing to compare the temporal development of the spray with the different fuels. In-cylinder fFID (fast Flame Ionisation Detector) measurements were undertaken to assess the Mixture in-homogeneity in the region of the spark plug. As the ethanol volumetric percentage increases, both the total Pn (Particulate number) and Pm (Particulate mass) increase by a maximum of 16 and 11 for cold conditions and 7 and 8 for warm conditions. This is in agreement with the natural flame chemiluminescence images which showed that fuels with high ethanol proportions generated more soot than fuels with small blending percentages of ethanol. Spray images and combustion analysis showed that ethanol addition results in protracted injection and combustion periods. The effect on spray characteristics is more profound under cold conditions than under warm conditions. The Mixture in-homogeneity increases as the ethanol content increases for E50, E70, and E85 and this would explain the increased level of particulate emissions, although the trend is less clear for the lower ethanol content fuels.

  • 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, 2010
    Co-Authors: P G Aleiferis, J Serraspereira, Roger Cracknell, A Augoye, T J Davies, D. Richardson
    Abstract:

    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 reflects strongly this effect. Therefore, the distillation curves of the fuels, the vapour pressures, as well as density, viscosity and surface tension were obtained and the Reynolds, Weber, Ohnesorge and Cavitation numbers were considered in the analysis. The in-nozzle flow regime and spray formation was found to be sensitive to the fuel temperature and gas pressure as a result of the vapour pressure and temperature relationships.

  • 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, 2010
    Co-Authors: P G Aleiferis, J Serraspereira, Roger Cracknell, A Augoye, T J Davies, D. Richardson
    Abstract:

    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 reflects strongly this effect. Therefore, the distillation curves of the fuels, the vapour pressures, as well as density, viscosity and surface tension were obtained and the Reynolds, Weber, Ohnesorge and Cavitation numbers were considered in the analysis. The in-nozzle flow regime and spray formation was found to be sensitive to the fuel temperature and gas pressure as a result of the vapour pressure and temperature relationships.

P G Aleiferis - One of the best experts on this subject based on the ideXlab platform.

  • flame front analysis of ethanol butanol iso octane and gasoline in a spark ignition engine using laser tomography and integral length scale measurements
    Combustion and Flame, 2015
    Co-Authors: P G Aleiferis, M K Behringer
    Abstract:

    Abstract Direct-injection spark-ignition engines have become popular due to their flexibility in injection strategies and higher efficiency; however, the high-pressure in-cylinder injection process can alter the airflow field by momentum exchange, with different effects for fuels of diverse properties. The current paper presents results from optical studies of stoichiometric combustion of ethanol, butanol, iso-octane and gasoline in a direct-injection spark-ignition engine run at 1500 RPM with 0.5 bar intake plenum pressure and early intake stroke fuel injection for homogeneous Mixture Preparation. The analysis initially involved particle image velocimetry measurements of the flow field at ignition timing with and without fuelling for comparison. Flame chemiluminescence imaging was used to characterise the global flame behaviour and double-pulsed Laser-sheet flame tomography by Mie scattering to quantify the local topology of the flame front. The flow measurements with fuel injection showed integral length scales of the same order to those of air only on the tumble plane, but larger regions with scales up to 9 mm on the horizontal plane. Averaged length scales over both measurement planes were between 4 and 6 mm, with ethanol exhibiting the largest and butanol the smallest. In non-dimensional form, the integral length scales were up to 20% of the clearance height and 5–12% of the cylinder bore. Flame tomography showed that at radii between 8 and 12 mm, ethanol was burning the fastest, followed by butanol, iso-octane and gasoline. The associated turbulent burning velocities were 4.6–6.5 times greater than the laminar burning velocities and about 13–20% lower than those obtained by flame chemiluminescence imaging. Flame roundness was 10–15% on the tomography plane, with largest values for ethanol, followed by butanol, gasoline and iso-octane; chemiluminescence imaging showed larger roundness (18–25%), albeit with the same order amongst fuels. The standard deviation of the displacement of the instantaneous flame contour from one filtered by its equivalent radius was obtained as a measure of flame brush thickness and correlated strongly with the equivalent flame radius; when normalised by the radius, it was 4–6% for all fuels. The number of crossing points between instantaneous and filtered flame contour showed a strong negative correlation with flame radius, independent of fuel type. The crossing point frequency was 0.5–1.6 mm−1. The flame brush thickness was about 1/10th of the integral length scale. A positive correlation was found between integral length scale and flame brush thickness and a negative correlation with crossing frequency.

  • Computational Study of Hydrogen Direct Injection for Internal Combustion Engines
    SAE Technical Paper Series, 2013
    Co-Authors: Arash Hamzehloo, P G Aleiferis
    Abstract:

    Hydrogen has been largely proposed as a possible fuel for internal combustion engines. The main advantage of burning hydrogen is the absence of carbon-based tailpipe emissions. Hydrogen's wide flammability also offers the advantage of very lean combustion and higher engine efficiency than conventional carbon-based fuels. In order to avoid abnormal combustion modes like pre-ignition and backfiring, as well as air displacement from hydrogen's large injected volume per cycle, direct injection of hydrogen after intake valve closure is the preferred Mixture Preparation method for hydrogen engines. The current work focused on computational studies of hydrogen injection and Mixture formation for direct-injection spark-ignition engines. Hydrogen conditions at the injector's nozzle exit are typically sonic. Initially the characteristics of under-expanded sonic hydrogen jets were investigated in a quiescent environment using both Reynolds-Averaged Navier-Stokes (RANS) and Large-Eddy Simulation (LES) techniques. Various injection conditions were studied, including a reference case from the literature. Different nozzle geometries were investigated, including a straight nozzle with fixed cross section and a stepped nozzle design. LES captured details of the expansion shocks better than RANS and demonstrated several aspects of hydrogen's injection and mixing. In-cylinder simulations were also performed with a side 6-hole injector using 70 and 100 bar injection pressure. Injection timing was set to just after inlet valve closure with duration of 6 s and 8 s, leading to global air-to-fuel equivalence ratios φ typically in the region of 0.2-0.4. The engine intake air pressure was set to 1.5 bar absolute to mimic boosted operation. It was observed that hydrogen jet wall impingement was always prominent. Comparison with non-fuelled engine conditions demonstrated the degree of momentum exchange between in-cylinder hydrogen injection and air motion. LES highlighted details of hydrogen's spatial distribution throughout the injection duration and up to ignition timing. Higher peak velocities were predicted by LES, especially on the tumble plane. With the employed injection strategy, the areas closer to the cylinder wall were richer in fuel than the centre of the chamber close to the end of compression. Copyright © 2013 SAE International and Copyright © 2013 KSAE.

  • characterisation of flame development with ethanol butanol iso octane gasoline and methane in a direct injection spark ignition engine
    Fuel, 2013
    Co-Authors: P G Aleiferis, J Serraspereira, D. Richardson
    Abstract:

    Abstract 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.

  • 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, 2010
    Co-Authors: P G Aleiferis, J Serraspereira, Roger Cracknell, A Augoye, T J Davies, D. Richardson
    Abstract:

    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 reflects strongly this effect. Therefore, the distillation curves of the fuels, the vapour pressures, as well as density, viscosity and surface tension were obtained and the Reynolds, Weber, Ohnesorge and Cavitation numbers were considered in the analysis. The in-nozzle flow regime and spray formation was found to be sensitive to the fuel temperature and gas pressure as a result of the vapour pressure and temperature relationships.

  • 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, 2010
    Co-Authors: P G Aleiferis, J Serraspereira, Roger Cracknell, A Augoye, T J Davies, D. Richardson
    Abstract:

    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 reflects strongly this effect. Therefore, the distillation curves of the fuels, the vapour pressures, as well as density, viscosity and surface tension were obtained and the Reynolds, Weber, Ohnesorge and Cavitation numbers were considered in the analysis. The in-nozzle flow regime and spray formation was found to be sensitive to the fuel temperature and gas pressure as a result of the vapour pressure and temperature relationships.

Ashwani K Gupta - One of the best experts on this subject based on the ideXlab platform.

  • toward ultra low emission distributed combustion with fuel air dilution
    Applied Energy, 2015
    Co-Authors: Ahmed E E Khalil, Ashwani K Gupta
    Abstract:

    Colorless distributed combustion (CDC) has been shown to offer enhanced combustor performance for stationary gas turbine application with near zero emissions, high combustion intensity and efficiency, thermal field uniformity, and enhanced stability. Mixture Preparation to form hot and low oxygen concentration environment paves the path to achieve CDC conditions. In this paper, a new approach of air dilution in partially premixed combustion conditions is employed and the results compared to premixed and non-premixed injection of air and fuel. Portion of the fuel is introduced in the air stream and portion of the air is introduced in the fuel stream such that the local equivalence ratios for each stream is well outside the flammability limit to eliminate flashback and instabilities. The experimental data demonstrated ultra-low emissions with this injection scheme. At equivalence ratio of 0.6, NO emission was 63% lower than non-premixed combustion mode. Also NO emission was similar to the premixed combustion with the advantage of eliminating flashback and flame instabilities that often prevail in premixed combustion conditions. Dilution provided 50% CO reduction as compared to non-premixed combustion. Numerical simulations, validated through Particle Image Velocimetry, were performed to outline the mixing process in each of the three cases. The methane Mixture fraction prior to ignition, determined numerically, was found to be one half of that for the non-premixed case and close to that of the premixed case. This enhanced Mixture Preparation, associated with the new air and fuel dilution technique, resulted in reduced emission. Also the jet momentum ratio (between both streams) is enhanced, mainly due to the air addition to the fuel stream, to result in better mixing and a better reaction distribution for ultra-low emissions. Further reduction of NOx is expected with improved distributed combustion condition.

  • Mixture Preparation effects on distributed combustion for gas turbine applications
    Journal of Energy Resources Technology-transactions of The Asme, 2012
    Co-Authors: Ahmed E E Khalil, Ashwani K Gupta, Kenneth M Bryden, Sang C Lee
    Abstract:

    Distributed Combustion is now known to provide significant improvements to the performance of gas turbine combustors. Key features of distributed combustion include uniform thermal field in the entire combustion chamber for significantly improved pattern factor and avoidance of hot-spot regions that promote thermal NO x emissions, negligible emissions of hydrocarbons and soot, low noise, and reduced air cooling requirements for turbine blades. Distributed combustion necessitates controlled mixing between the injected air, fuel, and hot reactive gases from within the combustor prior to Mixture ignition. The mixing process impacts spontaneous ignition of the Mixture to result in improved distributed combustion reactions. Distributed combustion can be achieved in premixed, partially premixed, or non-premixed modes of combustor operation with sufficient entrainment of hot and active species present in the combustion zone and their rapid turbulent mixing with the reactants. Distributed combustion with swirl is investigated here to further explore the beneficial aspects of such combustion under relevant gas turbine combustion conditions. The near-term goal is to develop a high-intensity combustor with ultra-low emissions of NOx and CO and a much improved pattern factor and eventual goal of near-zero emission combustor. Different fuel injection scenarios are examined with focus on mixing to achieve distributed reaction conditions and ultra-low emissions. In all the cases, air was injected tangentially to impart swirl to the flow inside the combustor. Ultra-low NO x emissions were found for both the premixed and non-premixed combustion modes for the geometries investigated here. Results showed very low levels of NO (~10 PPM) and CO (~21 PPM) emissions under non-premixed mode of combustion with air preheats at an equivalence ratio of 0.6 and a moderate heat release intensity of 27 MW/m3-atm. Further enhancement of the mixing process using dilution reduced NO emission to 4.6 PPM which is nearly equivalent to emissions under premixed combustion mode with reduced CO emissions compared to non-premixed combustion mode. Results are also reported on lean stability limits and OH* chemiluminescence under different fuel injection scenarios for determining the extent of distribution combustion conditions. Numerical simulations have also been performed to help develop an understanding of the mixing process for better understanding of ignition and combustion.

  • distributed swirl combustion for gas turbine application
    Applied Energy, 2011
    Co-Authors: Ahmed E E Khalil, Ashwani K Gupta
    Abstract:

    Abstract Colorless distributed combustion (CDC) has been shown to provide significant improvement in gas turbine combustor performance. Colorless distributed combustion with swirl is investigated here to develop ultra-low emissions of NO and CO, and significantly improved pattern factor. Experimental investigations have been performed using a cylindrical geometry combustor with swirling air injection and axial hot gas exit stream from the combustor. Air was injected tangentially to impart swirl to the flow inside the combustor. The results obtained from the combustor have demonstrated very low levels of NO (∼3 PPM) and CO (∼70 PPM) emissions at an equivalence ratio of 0.7 and a high heat release intensity of 36 MW/m 3 -atm under non-premixed combustion. To further simulate gas turbine operating conditions, inlet air to the combustor was preheated to 600 K temperature and the combustor operated at 2 atm pressure. Results showed very low levels of CO (∼10 PPM) but the NO increased somewhat to ∼10 PPM at an equivalence ratio of 0.5 and heat release intensity of 22.5 MW/m 3 -atm under non-premixed combustion conditions. For premixed combustion, the combustor demonstrated low levels of both NO (5 PPM) and CO (8 PPM) at an equivalence ratio of 0.6 and a heat release intensity of 27 MW/m 3 -atm. Results are reported at different equivalence ratios on the emission of NO and CO, lean stability limit and OH * chemiluminescence. These results suggest that further performance improvement can be achieved with improved fuel Mixture Preparation prior to the ignition of fuel at higher operational pressures using swirling combustor design for our quest to develop ultra low emission high intensity combustor for gas turbine application.

  • investigation of forward flow distributed combustion for gas turbine application
    Applied Energy, 2011
    Co-Authors: Vaibhav K Arghode, Ashwani K Gupta
    Abstract:

    Abstract New innovative advanced combustion design methodology for gas turbine applications is presented that is focused on the quest towards zero emissions. The new design methodology is called colorless distributed combustion (CDC) and is significantly different from the currently used methodology. In this paper forward flow modes of CDC have been investigated for application to gas turbine combustors. The CDC provides significant improvement in pattern factor, reduced NOx emission and uniform thermal field in the entire combustion zone for it to be called as an isothermal reactor. Basic requirement for CDC is carefully tailored Mixture Preparation through good mixing between the combustion air and product gases prior to rapid mixing with fuel so that the reactants are at much higher temperature to result in hot and diluted oxidant stream at temperatures that are high enough to autoignite the fuel and oxidant Mixture. With desirable conditions one can achieve spontaneous ignition of the fuel with distributed combustion reactions. Distributed reactions can also be achieved in premixed mode of operation with sufficient entrainment of burned gases and faster turbulent mixing between the reactants. In the present investigation forward flow modes consisting of two non-premixed combustion modes and one premixed combustion mode have been examined that provide potential for CDC. In all the configurations the air injection port is positioned at the opposite side of the combustor exit, whereas the location of fuel injection ports is changed to give different configurations. Two combustion geometries resulting in thermal intensity of 5 MW/m3-atm and 28 MW/m3-atm are investigated. Increase in thermal intensity (lower combustion volume) presents many challenges, such as, lower residence time, lower recirculation of gases and effect of confinement on jet characteristics. The results are presented on the global flame signatures, exhaust emissions, and radical emissions using experiments and flowfield using numerical simulations. Ultra-low NOx emissions are found for both the premixed and non-premixed combustion modes at the two thermal intensities investigated here. Almost colorless flames (no visible flame signatures) have been observed for the premixed combustion mode. The reaction zone is observed to be significantly different in the two non-premixed modes. Higher thermal intensity case resulted in lower recirculation of gases within the combustion chamber and higher CO levels, possibly due to lower associated residence time. The characteristics at the two thermal intensity combustors investigated here were found to be similar.

  • investigation of distributed combustion for gas turbine application forward flow configuration
    ASME 2010 Power Conference, 2010
    Co-Authors: Vaibhav K Arghode, Ashwani K Gupta
    Abstract:

    Colorless Distributed Combustion (CDC) has been investigated here for high efficiency and ultra low pollution gas turbine combustors applications. In this paper forward flow configurations have been examined. Basic requirement for CDC is carefully tailored Mixture Preparation prior to ignition through a combination of product gas recirculation, controlled mixing between the fresh combustion air and recirculated gases to form hot and diluted oxidizer. Rapid mixing between the injected fuel and hot oxidizer is desirable prior to spontaneous ignition of the Mixture in the entire combustion zone to achieve distributed combustion reactions. Distributed reactions can also be achieved in premixed mode of operation with sufficient entrainment of burned gases and faster turbulent mixing between the reactants. In the present investigation forward flow modes are considered in which three non-premixed and one premixed combustion mode have been examined that showed favorable CDC combustion conditions. In the forward flow configurations the air injection port is positioned at a location opposite to the combustor exit. The location of fuel injection ports is changed to give different configurations. The thermal intensity for the present investigation is 28MW/m3 -atm simulating gas turbine conditions. Increase in thermal intensity (lower combustion volume) presents many challenges, such as, lower residence time, lower recirculation of gases and confinement effects on the jet characteristics. The results are presented on the global flame signatures, exhaust emissions, and emission of radical species using experiments and flowfield dynamics using numerical simulations. Ultra low NOx emissions are found for both the premixed and non-premixed combustion modes investigated here. The reaction zone is observed to be significantly different in different combustion modes.© 2010 ASME

J Serraspereira - One of the best experts on this subject based on the ideXlab platform.

  • characterisation of flame development with ethanol butanol iso octane gasoline and methane in a direct injection spark ignition engine
    Fuel, 2013
    Co-Authors: P G Aleiferis, J Serraspereira, D. Richardson
    Abstract:

    Abstract 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.

  • 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, 2010
    Co-Authors: P G Aleiferis, J Serraspereira, Roger Cracknell, A Augoye, T J Davies, D. Richardson
    Abstract:

    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 reflects strongly this effect. Therefore, the distillation curves of the fuels, the vapour pressures, as well as density, viscosity and surface tension were obtained and the Reynolds, Weber, Ohnesorge and Cavitation numbers were considered in the analysis. The in-nozzle flow regime and spray formation was found to be sensitive to the fuel temperature and gas pressure as a result of the vapour pressure and temperature relationships.

  • 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, 2010
    Co-Authors: P G Aleiferis, J Serraspereira, Roger Cracknell, A Augoye, T J Davies, D. Richardson
    Abstract:

    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 reflects strongly this effect. Therefore, the distillation curves of the fuels, the vapour pressures, as well as density, viscosity and surface tension were obtained and the Reynolds, Weber, Ohnesorge and Cavitation numbers were considered in the analysis. The in-nozzle flow regime and spray formation was found to be sensitive to the fuel temperature and gas pressure as a result of the vapour pressure and temperature relationships.

  • cavitation primary break up and flash boiling of gasoline iso octane and n pentane with a real size optical direct injection nozzle
    Fuel, 2010
    Co-Authors: J Serraspereira, Z Van Romunde, P G Aleiferis, D. Richardson, Roger Cracknell
    Abstract:

    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.

  • mechanisms of spray formation and combustion from a multi hole injector with e85 and gasoline
    Combustion and Flame, 2010
    Co-Authors: P G Aleiferis, J Serraspereira, Z Van Romunde, J Caine, M Wirth
    Abstract:

    Abstract 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.

Rolf D Reitz - One of the best experts on this subject based on the ideXlab platform.

  • an equilibrium phase spray model for high pressure fuel injection and engine combustion simulations
    International Journal of Engine Research, 2019
    Co-Authors: Zongyu Yue, Rolf D Reitz
    Abstract:

    High-pressure fuel injection impacts Mixture Preparation, ignition and combustion in engines and other applications. Experimental studies have revealed the mixing-controlled and local phase equilibrium characteristics of liquid vaporization in high injection pressure diesel engine sprays. However, most computational fluid dynamics models for engine simulations spend much effort in solving for non-equilibrium spray processes. In this study, an equilibrium phase spray model is explored. The model is developed based on jet theory and a phase equilibrium assumption, without modeling drop breakup, collision and finite-rate interfacial vaporization processes. The proposed equilibrium phase spray model is validated extensively against experimental data in simulations of the engine combustion network Spray A and in an optical diesel engine. Predictions of liquid/vapor penetration, fuel mass fraction distribution, heat release rate and emission formation are all in good agreement with experimental data. In additio...

  • improved atomization collision and sub grid scale momentum coupling models for transient vaporizing engine sprays
    International Journal of Multiphase Flow, 2016
    Co-Authors: Federico Perini, Rolf D Reitz
    Abstract:

    Abstract A computationally efficient spray model is presented for the simulation of transient vaporizing engine sprays. It is applied to simulate high-pressure fuel injections in a constant volume chamber and in Mixture Preparation experiments in a light-duty internal combustion engine. The model is based on the Lagrangian-Particle/Eulerian-Fluid approach, and an improved blob injection model is used that removes numerical dependency on the injected number of computational parcels. Atomization is modeled with the hybrid Kelvin–Helmholtz/Rayleigh–Taylor scheme, in combination with a drop drag model that includes Mach number and Knudsen number effects. A computationally efficient drop collision scheme is presented, tailored for large numbers of parcels, using a deterministic collision impact definition and kd-tree data search structure to perform radius-of-influence based, grid-independent collision probability estimations. A near-nozzle sub-grid scale flow-field representation is introduced to reduce numerical grid dependency, which uses a turbulent transient gas-jet model with a Stokes–Strouhal analogy assumption. An implicit coupling method was developed for the Arbitrary Lagrangian–Eulerian (ALE) turbulent flow solver. A multi-objective genetic algorithm was used to study the interactions of the various model constants, and to provide an optimal calibration. The optimal set showed similar values of the primary breakup constants as values used in the literature. However, different values were seen for the gas-jet model constants for accurate simulations of the initial spray transient. The results show that there is a direct correlation between the predicted initial liquid-phase transient and the global gas-phase jet penetration. Model validation was also performed in engine simulations with the same set of constants. The model captured Mixture Preparation well in all cases, proving its suitability for simulations of transient spray injection in engines.

  • a comprehensive modeling study of in cylinder fluid flows in a high swirl light duty optical diesel engine
    Computers & Fluids, 2014
    Co-Authors: Federico Perini, Paul C Miles, Rolf D Reitz
    Abstract:

    Abstract The effectiveness of computational fluid dynamics modeling as a tool for researching fuel-lean, low temperature engine combustion strategies relies on its capability to capture the local fluid flow properties that affect spray dynamics, Mixture Preparation and ignition kinetics. In this study, a comprehensive model of an optically accessible, single-cylinder light-duty diesel engine was developed for engine combustion research. The computational model includes the realistic combustion chamber and ducts geometries. Variable orientation throttles in the intake ducts were modeled to reproduce variable swirl generation. Full induction stroke calculations were run over a portfolio of intake swirl conditions, and validated against extensive measurements featuring global intake swirl ratios, in-cylinder particle image velocimetry (PIV)-measured velocity fields and swirl centers. The results showed good agreement with the experiments, and the model was used to understand the effects of different swirl generation strategies on the in-cylinder flow field. The implications of using simplified sector mesh geometries on the predictiveness of in-cylinder flow and turbulence quantities are described.

  • modeling the ignitability of a pilot injection for a diesel primary reference fuel impact of injection pressure ambient temperature and injected mass
    SAE International Journal of Fuels and Lubricants, 2014
    Co-Authors: Federico Perini, Dipankar Sahoo, Paul C Miles, Rolf D Reitz
    Abstract:

    In this paper, we studied the accuracy of computational modeling of the ignition of a pilot injection in the Sandia National Laboratories (SNL) light-duty optical engine facility, using the physical properties of a cetane/iso-cetane Diesel Primary Reference Fuel (DPRF) Mixture and the reaction kinetics of a well-validated mechanism for primary reference fuels. Local fuel-air equivalence ratio measurements from fuel tracer based planar laser-induced fluorescence (PLIF) experiments were used to compare the Mixture formation predictions with KIVA-ERC-based simulations. The effects of variations in injection mass from 1 mg to 4 mg, in-cylinder swirl ratio, and near-TDC temperatures on non-combusting Mixture Preparation were analyzed, to assess the accuracy of the model in capturing average jet behavior, despite its inability to model the nonnegligible jet-by-jet variations seen in the experiments. Fired simulations were able to capture well the measured ignitability trends at the different injection conditions tested, but showed some deviations in the minimum temperature needed for robust ignition, pointing out the need for further work to focus on achieving fully comprehensive modeling with detailed chemical kinetics of the DPRF58 Mixture and a full engine geometry representation.

  • experimental study of pollutant emission reduction for near stoichiometric diesel combustion in a three way catalyst
    International Journal of Engine Research, 2009
    Co-Authors: K Sung, J Kim, Rolf D Reitz
    Abstract:

    An experimental study was performed to examine the possibility of simultaneous reductions of NOx, hydrocarbons (HC), CO, and soot emissions for near-stoichiometric diesel combustion using a three-way catalyst and a diesel particulate filter (DPF). The DPF was deactivated in order to ensure the non-regeneration state and was just used as a soot filter trap upstream of the three-way catalyst. The goal of the research was to investigate the efficiency of emission conversion for an automotive diesel engine with a general three-way catalyst normally used for gasoline-powered vehicles under near-stoichiometric combustion operation. A modified single-cylinder engine was used for the experiments that considered throttled diesel combustion at 65-90kPa intake pressure to achieve near-stoichiometric conditions, and a common rail injection system with 90MPa injection pressure was used for Mixture Preparation and to avoid spray wall impingement. The results showed that the three-way catalyst was able to reduce NOx and CO emissions by up to nearly 98%, and the DPF trapped soot emissions up to 99.6% for near-stoichiometric operation. However, the particular palladium/rhodium catalyst formulation used in the study was less effective for HC emissions, which were only reduced by up to 57%. It is concluded that the use of the present proposed three-way catalyst/DPF aftertreatment system provides significant promise for future efficient, low emission diesel engines