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We explore the potential for adaptive air barriers to mitigate convective heat losses from cavity receivers, especially at large tilt angles, using both suction and blowing nozzles. A heated scaled-down cylindrical cavity receiver was fitted with nozzles on four sides of the aperture, at 30° to the aperture plane. The tilted cavity receiver was mounted in a large wind tunnel to allow systematic variation of wind speed and direction. The effectiveness of different nozzle arrangements was calculated from the measured convective heat losses for a series of different mitigation strategies. The results reveal that a suction nozzle mounted at the bottom of the aperture is more effective than a blowing nozzle mounted at the top of aperture for tilt angles of θ= 45°, and under different wind speeds. The effectiveness ranged from 0 at a low suction flow rate to ~80% at a high suction flow rate. With the use of three suction nozzles, at the bottom and both sides of aperture, the effectiveness decreased markedly for both tilt angles and all wind speeds. For more challenging conditions of a 45° tilt angle and 45° yaw angle, the most effective approach is the use of suction through nozzles aligned diametrically opposite to the wind, while other nozzle combinations were ineffective in mitigating losses. Finally, the results highlight the need to apply an adaptive aerodynamic strategy that can respond to measured changes in the environmental conditions to achieve the highest thermal efficiency.
Elham Alipourtarzanagh; Alfonso Chinnici; Graham J. Nathan; Bassam B. Dally. An adaptive aerodynamic approach to mitigate convective losses from solar cavity receivers. Solar Energy 2021, 224, 1333 -1343.
AMA StyleElham Alipourtarzanagh, Alfonso Chinnici, Graham J. Nathan, Bassam B. Dally. An adaptive aerodynamic approach to mitigate convective losses from solar cavity receivers. Solar Energy. 2021; 224 ():1333-1343.
Chicago/Turabian StyleElham Alipourtarzanagh; Alfonso Chinnici; Graham J. Nathan; Bassam B. Dally. 2021. "An adaptive aerodynamic approach to mitigate convective losses from solar cavity receivers." Solar Energy 224, no. : 1333-1343.
This study presents an investigation of the influence of solar-to-fuel energy input ratio (S/F) on performance and stability characteristics of hybrid processes of solar and MILD combustion of H2. A laboratory-scale MILD Hybrid Solar Receiver Combustor was operated at 8-kWth capacity under MILD combustion and in the mixed-mode (MILD plus solar energy simultaneously). An 18-kWe three-lamp metal-halide solar simulator and the combustion of pure hydrogen were used as energy sources. The global combustion performance and stability limits for each mode of operation are reported for different levels of heat extraction and S/F values in the range 5–25%. It was found that similar thermal performance can be achieved for both modes across a wide range of conditions, together with steady operation in response to transients, indicating for the first time that MILD combustion can be used to efficiently compensate for variability in the solar resource, reduce thermal stresses and guarantees constant output. Steady solar-MILD operations retain similar features of conventional MILD processes (nearly-zero emissions, thermal field uniformity) even at relatively high S/F ratio. The global combustion characteristics, performance and stability limits are found to correlate with S/F in the mixed mode, while the operability region for which steady MILD processes can occur was found to increase significantly by adding high-flux concentrated solar radiation to the combustion process and by increasing S/F.
A. Chinnici; G.J. Nathan; B.B. Dally. Experimental investigation of the influence of solar-to-fuel ratio on performance and stability characteristics of hybrid solar-MILD hydrogen processes. Proceedings of the Combustion Institute 2020, 38, 6723 -6731.
AMA StyleA. Chinnici, G.J. Nathan, B.B. Dally. Experimental investigation of the influence of solar-to-fuel ratio on performance and stability characteristics of hybrid solar-MILD hydrogen processes. Proceedings of the Combustion Institute. 2020; 38 (4):6723-6731.
Chicago/Turabian StyleA. Chinnici; G.J. Nathan; B.B. Dally. 2020. "Experimental investigation of the influence of solar-to-fuel ratio on performance and stability characteristics of hybrid solar-MILD hydrogen processes." Proceedings of the Combustion Institute 38, no. 4: 6723-6731.
Flames in hot, low oxygen environments exist in a variety of practical applications. These conditions result in significant mixing between fuel and combustion products, such as water vapour, or diluents included for emissions control. The chemical and physical effects of water vapour as a diluent are investigated in a series of ethylene flames in a jet in hot coflow burner to determine the effects on temperature and soot fields. The combined analyses of photographs, non-linear excitation regime two-line atomic fluorescence (NTLAF) of indium, planar laser-induced incandescence (LII) and one-dimensional opposed-flow flame simulations demonstrate the dominance of the chemistry, driven by the hot and vitiated oxidant, in soot reduction. Although photographs appear to suggest that both highly vitiated coflows, and highly diluted jet flames have global effect on the flames, detailed measurements reveal significantly different trends in their soot and temperature fields. The chemical contribution of water vapour as a reactant, as a third-body in ethylene decomposition and a source of H and OH in the rich mixture is further described, and trends subsequently identified, in the context of formation of polycyclic aromatic hydrocarbons and soot reduction.
Michael John Evans; Alfonso Chinnici. Water vapour effects on temperature and soot loading in ethylene flames in hot and vitiated coflows. Proceedings of the Combustion Institute 2020, 38, 5383 -5391.
AMA StyleMichael John Evans, Alfonso Chinnici. Water vapour effects on temperature and soot loading in ethylene flames in hot and vitiated coflows. Proceedings of the Combustion Institute. 2020; 38 (4):5383-5391.
Chicago/Turabian StyleMichael John Evans; Alfonso Chinnici. 2020. "Water vapour effects on temperature and soot loading in ethylene flames in hot and vitiated coflows." Proceedings of the Combustion Institute 38, no. 4: 5383-5391.
We report on the effectiveness of an air curtain to mitigate convective heat losses from a heated cylindrical cavity receiver operated at fixed tilt (15°) and yaw angles (0°). The cavity was heated electrically with a controller to maintain a constant inside temperature of 300 °C, varying wind speed, air curtain velocity and discharge angle. It was found that the greatest convective heat losses occur over the lower internal surfaces of the cavity for all cases, spanning both natural and forced convection regimes, while a discharge angle of 30° relative to the face of the cavity is more effective than a parallel curtain, which was found to increase heat losses. It was also found that, for a discharge angle of 0°, increasing the velocity of the air curtain leads to higher convective heat losses. However, for a curtain discharge angle of 30°, increasing the air curtain velocity can reduce heat losses by up to 60%. The measured distribution of air temperature across the aperture plane and convective heat losses through the surface were used to provide insight into the causes of these observations. These results suggest that, for tilted, tower-mounted cavity receivers, the orientation of an air curtain should be directed with a component towards the wind, rather than parallel to the aperture plane.
Elham Alipourtarzanagh; Alfonso Chinnici; Graham J. Nathan; Bassam B. Dally. Experimental insights into the mechanism of heat losses from a cylindrical solar cavity receiver equipped with an air curtain. Solar Energy 2020, 201, 314 -322.
AMA StyleElham Alipourtarzanagh, Alfonso Chinnici, Graham J. Nathan, Bassam B. Dally. Experimental insights into the mechanism of heat losses from a cylindrical solar cavity receiver equipped with an air curtain. Solar Energy. 2020; 201 ():314-322.
Chicago/Turabian StyleElham Alipourtarzanagh; Alfonso Chinnici; Graham J. Nathan; Bassam B. Dally. 2020. "Experimental insights into the mechanism of heat losses from a cylindrical solar cavity receiver equipped with an air curtain." Solar Energy 201, no. : 314-322.
This work presents the thermal performance, emissions and stability limits for steady-operations of a laboratory-scale combustor operating in the Moderate or Intense Low oxygen Dilution (MILD) combustion regime and fed with syngas fuels. The device was operated at 12-kWth using syngas with different H2/CO composition (H2/CO by v/v = 1–3). The global performance of the device, namely thermal efficiency, pollutant emissions, heat flux distribution and stability limits, were measured as a function of the heat extracted. It was found that the MILD combustion regime can be achieved over a broad range of fuel composition and operating parameters, with nearly-zero NOx and CO emissions. An increase in the H2/CO ratio of the syngas stream was found to increase both the stability limits for steady MILD processes and the NOx emissions. Irrespective of the fuel type, similar thermal efficiencies were measured for all cases investigated, providing evidence that the device can efficiently (i) operate with low-calorific fuels and (ii) accommodate for variability in the composition of the syngas fuel stream. In addition, the numerical analysis highlighted that the syngas composition strongly influences the rate of radiative heat transfer and reactions as well as the characteristics of the reaction zone.
A. Chinnici; G.J. Nathan; B.B. Dally. Experimental and numerical study of the influence of syngas composition on the performance and stability of a laboratory-scale MILD combustor. Experimental Thermal and Fluid Science 2020, 115, 110083 .
AMA StyleA. Chinnici, G.J. Nathan, B.B. Dally. Experimental and numerical study of the influence of syngas composition on the performance and stability of a laboratory-scale MILD combustor. Experimental Thermal and Fluid Science. 2020; 115 ():110083.
Chicago/Turabian StyleA. Chinnici; G.J. Nathan; B.B. Dally. 2020. "Experimental and numerical study of the influence of syngas composition on the performance and stability of a laboratory-scale MILD combustor." Experimental Thermal and Fluid Science 115, no. : 110083.
An experimental investigation of the interaction between the internal and external flows through a simplified laboratory-scale hybrid solar cavity receiver is presented. The experiments were conducted under isothermal conditions using the Particle Image Velocimetry (PIV) technique. The device comprises a cylindrical chamber (70 mm inner diameter and 225 mm long) fitted with four jets (3.35 mm inner diameter) simulating fuel and air supply and an aperture. Four different configurations have been tested, with two different jet inclination angles (25° and 50°) and with two different jet azimuthal angles (0° and 5°). Water was used as the working fluid and the models were placed in a water channel with variable speed to allow the influence of an external flow to be simulated. The results show that the flow behaviour within the cavity is strongly dependent on the jets’ configuration, the aperture ratio and tilt angle. A significant flow of external fluid was entrained through the aperture for all of configurations, with an additional 22% and 42% to the internal flow for the (αj = 25°, γj = 0°) case with zero and 0.24 m/s exteral velocity, respectively. The effect of openning the apreture on jet decay, turbulence intensity and recirculation pattern was also recorded. It is found that while opening the aperture and introducing an external flow have little qualitative influence on the flow pattern and jet decay, the turbulence intensity in the proximity of the aperture changes considerably. The need to manage the complex interactions between the external and internal flows through the cavity receiver is defined.
Elham Alipourtarzanagh; Alfonso Chinnici; Zhao Feng Tian; Graham J. Nathan; Bassam B. Dally. The coupling between the internal and external flows through a hybridized solar cavity receiver under isothermal conditions. Experimental Thermal and Fluid Science 2019, 113, 110028 .
AMA StyleElham Alipourtarzanagh, Alfonso Chinnici, Zhao Feng Tian, Graham J. Nathan, Bassam B. Dally. The coupling between the internal and external flows through a hybridized solar cavity receiver under isothermal conditions. Experimental Thermal and Fluid Science. 2019; 113 ():110028.
Chicago/Turabian StyleElham Alipourtarzanagh; Alfonso Chinnici; Zhao Feng Tian; Graham J. Nathan; Bassam B. Dally. 2019. "The coupling between the internal and external flows through a hybridized solar cavity receiver under isothermal conditions." Experimental Thermal and Fluid Science 113, no. : 110028.
We report a joint experimental, numerical and theoretical study of particle residence times in a novel vortex-based vessel for thermal processing of suspended particles. The tracer pulse-response method, in which the particle phase itself is employed as the tracer, is used to measure the particle residence time distribution (RTD) within a laboratory-scale model of a class of Solar Expanding Vortex Receiver-Reactor (SEVR). The operating parameters of particle size, gas volumetric flow rate and inlet velocity were systematically varied to assess their influence on the particle RTD and to determine the mechanisms controlling the behaviour of the two-phase flow in the SEVR. The particle RTD behaviour is also described by a compartment model consisting of a small plug flow reactor followed by a series of two interconnected continuously-stirred tank reactors (CSTRs).
Dominic Davis; Maurizio Troiano; Alfonso Chinnici; Woei Lean Saw; Timothy Lau; Roberto Solimene; Piero Salatino; Graham J. Nathan. Particle residence time distributions in a vortex-based solar particle receiver-reactor: An experimental, numerical and theoretical study. Chemical Engineering Science 2019, 214, 115421 .
AMA StyleDominic Davis, Maurizio Troiano, Alfonso Chinnici, Woei Lean Saw, Timothy Lau, Roberto Solimene, Piero Salatino, Graham J. Nathan. Particle residence time distributions in a vortex-based solar particle receiver-reactor: An experimental, numerical and theoretical study. Chemical Engineering Science. 2019; 214 ():115421.
Chicago/Turabian StyleDominic Davis; Maurizio Troiano; Alfonso Chinnici; Woei Lean Saw; Timothy Lau; Roberto Solimene; Piero Salatino; Graham J. Nathan. 2019. "Particle residence time distributions in a vortex-based solar particle receiver-reactor: An experimental, numerical and theoretical study." Chemical Engineering Science 214, no. : 115421.
The intermittent nature of solar energy limits its further deployment to applications where firm supply and constant output is required. While energy storage is a viable option to increase solar share, in itself is not sufficient without an additional dispatchable energy source. Combustion of both fossil-based and renewable fuels can provide the demand ready energy source required and lends itself to hybridization with tower based Concentrated Solar Thermal, CST, energy. The Hybrid Solar Receiver Combustor, HSRC, is a novel technology that integrates both sources of energy in one device and offers tangible benefits in increased solar share, thermal efficiency and reduced capital and operation costs. This paper reports a brief review of the different findings from experimental and computational research carried out at the Center for Energy Technology of the University of Adelaide into optimizing the HSRC design, developing the first-of-a-kind laboratory-scale HSRC unit and evaluating its performance under different fuels, operating conditions and modes of operation. It highlights the benefits and need for utilizing MILD combustion in the HSRC to match the heat transfer characteristics and stability required to achieve similar operational range and efficiency from both sources of energy. A 5-kWel xenon-arc solar simulator and the combustion of a wide variety of fuels are used as the energy sources. This paper reports on the effectiveness of MILD combustion under these conditions and in particular it discusses flame stability envelop and its relation to heat extraction, temperature and pollutant emissions. It also reports on thermal efficiency, heat losses and heat flux distribution within the cavity for all fuels and operating conditions. It is found that the HSRC thermal performance is similar under the three operation modes (solar, combustion, and combined) and that operating under MILD combustion mode allowed fuel flexibility, homogeneous heat distribution and very low emission of NOx and CO. Also found that H/C ratio plays a minor role in the radiated energy to the heat exchanger within the cavity. Future research and further technology development need is also discussed in this paper.
Alfonso Chinnici; Graham J. Nathan; Bassam B. Dally. Hybrid Solar-MILD Combustion for Renewable Energy Generation. Frontiers in Mechanical Engineering 2019, 5, 1 .
AMA StyleAlfonso Chinnici, Graham J. Nathan, Bassam B. Dally. Hybrid Solar-MILD Combustion for Renewable Energy Generation. Frontiers in Mechanical Engineering. 2019; 5 ():1.
Chicago/Turabian StyleAlfonso Chinnici; Graham J. Nathan; Bassam B. Dally. 2019. "Hybrid Solar-MILD Combustion for Renewable Energy Generation." Frontiers in Mechanical Engineering 5, no. : 1.
Dominic Davis; Maurizio Troiano; Alfonso Chinnici; Woei Lean Saw; Timothy Lau; Roberto Solimene; Piero Salatino; Graham J. Nathan. Particle residence time distributions in a vortex-based solar particle receiver-reactor: The influence of receiver tilt angle. Solar Energy 2019, 190, 126 -138.
AMA StyleDominic Davis, Maurizio Troiano, Alfonso Chinnici, Woei Lean Saw, Timothy Lau, Roberto Solimene, Piero Salatino, Graham J. Nathan. Particle residence time distributions in a vortex-based solar particle receiver-reactor: The influence of receiver tilt angle. Solar Energy. 2019; 190 ():126-138.
Chicago/Turabian StyleDominic Davis; Maurizio Troiano; Alfonso Chinnici; Woei Lean Saw; Timothy Lau; Roberto Solimene; Piero Salatino; Graham J. Nathan. 2019. "Particle residence time distributions in a vortex-based solar particle receiver-reactor: The influence of receiver tilt angle." Solar Energy 190, no. : 126-138.
This paper reports the impact of surrounding oxygen (O2) concentrations on the burning characteristics of pulverised brown coal under MILD (Moderate or Intense Low-oxygen Dilution) combustion conditions. A combined experimental and computational study is conducted to probe the volatiles' release and reactions from the micro sized coal particles and its effect on the production of CO, CO2 and NOx in a vertical furnace. Pulverised high volatile Victorian brown coal was introduced into the furnace utilising CO2 as a carrier gas through a central jet with a constant bulk jet Reynolds number Rejet = 20,000, and two co-flow oxygen concentration of 5.9% and 8.9%. For all the cases investigated, stable MILD combustion was achieved, featuring a uniform temperature distribution within the furnace. It was found that the co-flow O2 concentration significantly influences the CO emission. The measured CO emission for the 5.9% co-flow O2 concentration case is approximately eight times higher than that of the 8.9% co-flow O2 concentration case. In addition, the CFD analysis showed that an increase in the local O2 concentration leads to an increase in the volatiles release and reaction rates. Also, up to 63% more NO is produced for the 5.9% co-flow O2 concentration case in comparison with the 8.9% O2 case through the fuel-NO route.
Manabendra Saha; Bassam B. Dally; Alfonso Chinnici; Paul R. Medwell. Effect of co-flow oxygen concentration on the MILD combustion of pulverised coal. Fuel Processing Technology 2019, 193, 7 -18.
AMA StyleManabendra Saha, Bassam B. Dally, Alfonso Chinnici, Paul R. Medwell. Effect of co-flow oxygen concentration on the MILD combustion of pulverised coal. Fuel Processing Technology. 2019; 193 ():7-18.
Chicago/Turabian StyleManabendra Saha; Bassam B. Dally; Alfonso Chinnici; Paul R. Medwell. 2019. "Effect of co-flow oxygen concentration on the MILD combustion of pulverised coal." Fuel Processing Technology 193, no. : 7-18.
The first systematic experimental study of the combined influences of wind speed (0–9 m/s), aperture ratio (0.33–1) and tilt angle (15°–45°) on the mixed (free and forced) convective heat losses from a heated cavity, is presented. The cylindrical cavity is heated by 16 individually temperature-controlled heating elements in the open section of a wind tunnel. Heat flux distribution and total heat losses from the cavity were measured. A complex inter-dependence was found between aperture ratio, wind speed and convective heat losses. In particular, the total heat losses can vary by up to ∼75% by varying the aperture ratio from 0.33 to 0.75, for no wind condition, but the effect of aperture ratio is decreased as wind speed is increased. The tilt angle was found to have a small effect on the heat losses relative to the aperture ratio and wind speed. Nevertheless, the average minimum mixed heat loss for various wind speeds occurs for a tilt angle of between 15° and 30° for a downward tilting solar tower system.
Ka Lok Lee; Alfonso Chinnici; Mehdi Jafarian; Maziar Arjomandi; Bassam Dally; Graham Nathan. The influence of wind speed, aperture ratio and tilt angle on the heat losses from a finely controlled heated cavity for a solar receiver. Renewable Energy 2019, 143, 1544 -1553.
AMA StyleKa Lok Lee, Alfonso Chinnici, Mehdi Jafarian, Maziar Arjomandi, Bassam Dally, Graham Nathan. The influence of wind speed, aperture ratio and tilt angle on the heat losses from a finely controlled heated cavity for a solar receiver. Renewable Energy. 2019; 143 ():1544-1553.
Chicago/Turabian StyleKa Lok Lee; Alfonso Chinnici; Mehdi Jafarian; Maziar Arjomandi; Bassam Dally; Graham Nathan. 2019. "The influence of wind speed, aperture ratio and tilt angle on the heat losses from a finely controlled heated cavity for a solar receiver." Renewable Energy 143, no. : 1544-1553.
Shen Long; Timothy C. W. Lau; Alfonso Chinnici; Zhao Feng Tian; Bassam B. Dally; Graham J. Nathan. Characteristics of swirling and precessing flows generated by multiple confined jets. Physics of Fluids 2019, 31, 055102 .
AMA StyleShen Long, Timothy C. W. Lau, Alfonso Chinnici, Zhao Feng Tian, Bassam B. Dally, Graham J. Nathan. Characteristics of swirling and precessing flows generated by multiple confined jets. Physics of Fluids. 2019; 31 (5):055102.
Chicago/Turabian StyleShen Long; Timothy C. W. Lau; Alfonso Chinnici; Zhao Feng Tian; Bassam B. Dally; Graham J. Nathan. 2019. "Characteristics of swirling and precessing flows generated by multiple confined jets." Physics of Fluids 31, no. 5: 055102.
An experimental investigation is presented of the effects of wind speed (0 - 9 m/s), yaw angle (0° and 90°), and tilt angle (15° and -90°) on the mixed convective heat losses from a cylindrical cavity heated with different internal wall temperature distributions. The internal wall comprised 16 individually controlled heating elements to allow the distribution of the surface temperature to be well controlled, while the air flow was controlled with a wind tunnel. It is found that temperature distribution has a strong influence on the convective heat losses, with a joint dependence on the wind speed and its direction. For the no-wind and side-on wind conditions, the measured range of the heat losses varied by up to 50% with a change in the wall temperature distribution. However, for high head-on wind speeds, this variation reduced down to ∼20%. In addition, the heat losses from downward tilted were ∼3 times larger than the upward facing heated cavity for high wind speeds (typical of tower-mounted and beam-down configurations, respectively). Also, the measured heat losses were found to be only slightly dependent on wind speed and direction in contrast with the downward tilted cases.
Ka Lok Lee; Alfonso Chinnici; Mehdi Jafarian; Maziar Arjomandi; Bassam Dally; Graham Nathan. The influence of wall temperature distribution on the mixed convective losses from a heated cavity. Applied Thermal Engineering 2019, 155, 157 -165.
AMA StyleKa Lok Lee, Alfonso Chinnici, Mehdi Jafarian, Maziar Arjomandi, Bassam Dally, Graham Nathan. The influence of wall temperature distribution on the mixed convective losses from a heated cavity. Applied Thermal Engineering. 2019; 155 ():157-165.
Chicago/Turabian StyleKa Lok Lee; Alfonso Chinnici; Mehdi Jafarian; Maziar Arjomandi; Bassam Dally; Graham Nathan. 2019. "The influence of wall temperature distribution on the mixed convective losses from a heated cavity." Applied Thermal Engineering 155, no. : 157-165.
A numerical analysis of the isothermal flow field within a directly irradiated Rotating Fluidized Bed Receiver (RFBR), is presented to provide a systematic assessment of the influence of key receiver control parameters, namely fluidized bed rotational speed and radial fluidizing gas velocity, on the flow field inside the receiver and particle deposition onto the receiver window. To achieve these aims, a Computational Fluid Dynamics (CFD) model of the RFBR was developed and coupled with Discrete Phase Model (DPM) to analyse the fluid flow and particle trajectory in the receiver cavity due to systematic variations in the key control parameters. The fluid flow modelling approach was partially verified by comparing the numerical predictions with previously published experimental flow measurements in a rotating vortex flow device that is geometrically similar to the RFBR. Using the reported modelling approach, the sensitivity of the flow field and particle deposition to the variations in the key control parameters was determined. Flow features and physical mechanisms linked to particle deposition onto the receiver window were identified with the view to better understand the operation of the RFBR and determine suitable operating regimes that achieve a low risk of particle deposition.
Zhao Lu; Alfonso Chinnici; Mehdi Jafarian; Maziar Arjomandi; Graham J. Nathan. Numerical investigation of the isothermal flow field and particle deposition behaviour in a rotating fluidized bed solar receiver. Solar Energy 2019, 182, 348 -360.
AMA StyleZhao Lu, Alfonso Chinnici, Mehdi Jafarian, Maziar Arjomandi, Graham J. Nathan. Numerical investigation of the isothermal flow field and particle deposition behaviour in a rotating fluidized bed solar receiver. Solar Energy. 2019; 182 ():348-360.
Chicago/Turabian StyleZhao Lu; Alfonso Chinnici; Mehdi Jafarian; Maziar Arjomandi; Graham J. Nathan. 2019. "Numerical investigation of the isothermal flow field and particle deposition behaviour in a rotating fluidized bed solar receiver." Solar Energy 182, no. : 348-360.
The scenario of fuel injected into hot surrounds is found in a range of practical combustion applications. These flame conditions have been emulated using a jet-in-hot-coflow-burner using prevaporised n-heptane and mixtures of n-heptane and toluene, relevant to gasoline and diesel fuel surrogates. This paper reports measurements of six lifted, turbulent flames, with a constant jet flow of a prevaporised fuel/N2 mixture at 380 K into various hot and vitiated coflow conditions. Five of these flames issued into coflows generated by the combustion of different mixtures of ethylene/air and one had a coflow from a natural gas/air flame. Two n-heptane/toluene fuel blends were also measured to study the effect of soot propensity. Gas sampling, non-linear excitation regime two-line atomic fluorescence (NTLAF) and laser-induced incandescence (LII) were used to characterise the flames, investigate the mixing between the hot coflow and the surrounding air, and measure the flame temperature for the different coflow configurations. A comparison of results of the flames issuing into hot coflows is presented, indicating that the hottest flame is not associated with the coflow containing the highest concentration of O2, but with the minimum soot loading and, consequently, the minimum radiative heat loss. Subsequent numerical simulations of canonical opposed-flow flames demonstrate that the soot loading in the downstream region of the flames is strongly dependent on PAH formation in the hot coflow region and further analyses reveal the chemical pathways which are most impacted by small variations in hot coflow composition.
Michael J. Evans; Paul R. Medwell; Zhiwei Sun; Alfonso Chinnici; Jingjing Ye; Qing N. Chan; Bassam B. Dally. Downstream evolution of n-heptane/toluene flames in hot and vitiated coflows. Combustion and Flame 2019, 202, 78 -89.
AMA StyleMichael J. Evans, Paul R. Medwell, Zhiwei Sun, Alfonso Chinnici, Jingjing Ye, Qing N. Chan, Bassam B. Dally. Downstream evolution of n-heptane/toluene flames in hot and vitiated coflows. Combustion and Flame. 2019; 202 ():78-89.
Chicago/Turabian StyleMichael J. Evans; Paul R. Medwell; Zhiwei Sun; Alfonso Chinnici; Jingjing Ye; Qing N. Chan; Bassam B. Dally. 2019. "Downstream evolution of n-heptane/toluene flames in hot and vitiated coflows." Combustion and Flame 202, no. : 78-89.
Alfonso Chinnici; Graham J. Nathan; Bassam B. Dally. Performance characteristics of a hybrid solar receiver combustor utilising hydrogen or syngas. SOLARPACES 2018: International Conference on Concentrating Solar Power and Chemical Energy Systems 2019, 1 .
AMA StyleAlfonso Chinnici, Graham J. Nathan, Bassam B. Dally. Performance characteristics of a hybrid solar receiver combustor utilising hydrogen or syngas. SOLARPACES 2018: International Conference on Concentrating Solar Power and Chemical Energy Systems. 2019; ():1.
Chicago/Turabian StyleAlfonso Chinnici; Graham J. Nathan; Bassam B. Dally. 2019. "Performance characteristics of a hybrid solar receiver combustor utilising hydrogen or syngas." SOLARPACES 2018: International Conference on Concentrating Solar Power and Chemical Energy Systems , no. : 1.
A. Chinnici; G.J. Nathan; B.B. Dally. An experimental study of the stability and performance characteristics of a Hybrid Solar Receiver Combustor operated in the MILD combustion regime. Proceedings of the Combustion Institute 2019, 37, 5687 -5695.
AMA StyleA. Chinnici, G.J. Nathan, B.B. Dally. An experimental study of the stability and performance characteristics of a Hybrid Solar Receiver Combustor operated in the MILD combustion regime. Proceedings of the Combustion Institute. 2019; 37 (4):5687-5695.
Chicago/Turabian StyleA. Chinnici; G.J. Nathan; B.B. Dally. 2019. "An experimental study of the stability and performance characteristics of a Hybrid Solar Receiver Combustor operated in the MILD combustion regime." Proceedings of the Combustion Institute 37, no. 4: 5687-5695.
We report a systematic study of the interaction between four rotationally symmetric jets within a cylindrical chamber obtained with particle image velocimetry, under conditions relevant to a wide range of practical applications including the hybrid solar receiver combustor. The geometry consists of a cylindrical cavity with four inlet jets (representing four burners), which are configured in an annular arrangement and aligned at an inclination angle (αj) to the axis with a tangential component (azimuthal angle θj) to generate a swirl in the chamber. The configurations of αj = 25° were assessed with two azimuthal angles θj = 5° and 15°, a range of chamber aspect ratios (Lc/Dc), and a fixed nozzle Reynolds number of ReD = 10 500. The experimental results reveal a significant dependence of the mean and turbulent flow-fields on the aspect ratio Lc/Dc for the values of αj and θj considered here. Three different flow regimes and their controlling parameters were identified within the range 1 ≤ Lc/Dc ≤ 3. The de...
Shen Long; Timothy Lau; Alfonso Chinnici; Zhao Feng Tian; Bassam B. Dally; Graham J. Nathan. The influence of aspect ratio on the iso-thermal flow characteristics of multiple confined jets. Physics of Fluids 2018, 30, 125108 .
AMA StyleShen Long, Timothy Lau, Alfonso Chinnici, Zhao Feng Tian, Bassam B. Dally, Graham J. Nathan. The influence of aspect ratio on the iso-thermal flow characteristics of multiple confined jets. Physics of Fluids. 2018; 30 (12):125108.
Chicago/Turabian StyleShen Long; Timothy Lau; Alfonso Chinnici; Zhao Feng Tian; Bassam B. Dally; Graham J. Nathan. 2018. "The influence of aspect ratio on the iso-thermal flow characteristics of multiple confined jets." Physics of Fluids 30, no. 12: 125108.
We report a first-order assessment of a novel vortex-based solar particle receiver and the sensitivity of its thermal performance to a number of key operational parameters. This assessment is made with a one-dimensional numerical model developed here to adapt the zonal method to calculate heat and mass transport within the enclosure of the solar vortex receiver (SVR) and to incorporate radiative and convective heat transfer between the particle phase, the air phase and the receiver wall together with re-radiative and conductive loss from the receiver. This simplified one-dimensional model allows for the systematic assessment of first order trends of mass and energy balance within the SVR and is used here to advance understanding of the dominant mechanisms controlling its thermal performance. Sensitivity studies of the thermal performance of the SVR reveal that the receiver can be configured to operate as either an air-heater or a particle-heater, depending primarily on the particle mass loading. For the present SVR configuration, the critical value of mass loading, ṁp/ṁair ≈ 1 was found to define the boundary, above which the device acts as a particle heater, and below which it acts as an air heater. Furthermore, an assessment of the two-phase flow direction found that a counter-flow (relative to the incident concentrated solar radiation) tends to result in a higher efficiency than a co-flow direction. The first order trends of the sensitivity of thermal performance of the SVR to the particle and air mass flow rates, particle size and receiver length were also assessed, finding that the ratio of receiver thermal input to heat capacity of the two-phase flow has a controlling influence on the thermal efficiency of the SVR, particularly with the front entry configuration. Overall receiver thermal efficiencies of up to 88% were predicted for the SVR operating with high mass flow rates of both particles and air, but it is expected that the thermal efficiency of the device for all operating conditions assessed here would increase with an increase in receiver scale from the laboratory-scale device considered here.
Dominic Davis; Mehdi Jafarian; Alfonso Chinnici; Woei Lean Saw; Graham J. Nathan. Thermal performance of vortex-based solar particle receivers for sensible heating. Solar Energy 2018, 177, 163 -177.
AMA StyleDominic Davis, Mehdi Jafarian, Alfonso Chinnici, Woei Lean Saw, Graham J. Nathan. Thermal performance of vortex-based solar particle receivers for sensible heating. Solar Energy. 2018; 177 ():163-177.
Chicago/Turabian StyleDominic Davis; Mehdi Jafarian; Alfonso Chinnici; Woei Lean Saw; Graham J. Nathan. 2018. "Thermal performance of vortex-based solar particle receivers for sensible heating." Solar Energy 177, no. : 163-177.
The use of hybrid solar thermal devices, which integrate the energy from both concentrated solar radiation and combustion, is receiving growing attention due to their potential to provide a firm and dispatchable thermal energy supply while lowering the costs of energy systems and assisting the penetration of renewable energy. The hybrid solar receiver combustor, HSRC, directly integrates the function of a solar receiver and a combustor into a single device for applications in combined heat and power generation. Compared with the present state-of-the-art of hybrid solar-combustion systems (which collect the thermal energy from the solar and combustion sources in separate devices and then combine them subsequently), the HSRC offers a reduction in total infrastructure (and hence capital costs), levelised cost of electricity, surface area for heat losses and start-up/shut-down losses, as well as lower pollutant emissions, associated with the need to start-up the back-up combustion plant before its heat is required. Its design allows the system to operate in three modes: solar-only (when solar radiation is abundant), combustion-only (in absence of solar energy, with natural gas as the energy source) and a mixed-mode (a combination of both solar and combustion, to manage short and long-term variability of the solar source). This paper presents the first-of-a-kind experimental demonstration of a mixed-mode reaction chamber. A laboratory-scale (20-kWth maximum capacity) HSRC was built and tested under the three different modes of operation. The device was configured to operate with Moderate or Intense Low oxygen Dilution (MILD) combustion to offer low NOx and potential for increased heat transfer. The combustion process was in direct fluid/heat interaction with the environment through the aperture (i.e. no window was employed), when operating under mixed-mode. Natural gas and a 5-kWel xenon-arc solar lamp simulator were used as energy sources for the combustion and solar modes, respectively. The influence of the mode of operation on the thermal efficiency, heat losses and heat flux distribution within the cavity were investigated. Despite the different contributions from the two dominant modes of heat transfer, namely radiation and heat convection, under the different regimes of operation, it was found that the device can achieve similar thermal efficiency in all modes (considering heat recovery from the exhausts). Also, the thermal efficiency was found to increase when operating under mixed-mode in comparison with the combustion-only mode, as a direct effect of hybridisation and due to low heat/mass transfer with the environment (low convective heat losses). The heat flux distributions on the heat transfer fluid coils were found to be significantly different under the different modes of operation.
Alfonso Chinnici; Graham J. Nathan; Bassam B. Dally. Performance of a hybrid solar receiver combustor. AIP Conference Proceedings 2018, 2033, 180004 .
AMA StyleAlfonso Chinnici, Graham J. Nathan, Bassam B. Dally. Performance of a hybrid solar receiver combustor. AIP Conference Proceedings. 2018; 2033 (1):180004.
Chicago/Turabian StyleAlfonso Chinnici; Graham J. Nathan; Bassam B. Dally. 2018. "Performance of a hybrid solar receiver combustor." AIP Conference Proceedings 2033, no. 1: 180004.