Effect Of Fuel Temperature Research Articles

Fuel Temperature Effects on Combustion Stability of a High-Pressure Liquid-Fueled Swirl Flame

The influence of fuel temperature on combustion instabilities is investigated in a liquid-fueled, piloted swirl flame at 1.0 MPa. Fuels used for this study include Jet A and a Fischer–Tropsch-based synthetic paraffinic fuel (Shell GTL GS190). Simultaneous OH* chemiluminescence, particle image velocimetry, and Mie scattering measurements are performed in an optically accessible combustion chamber at 10 kHz for fuel temperatures ranging from 294 to 525 K. At ambient fuel temperature, a self-excited longitudinal instability is observed at 825 Hz. A higher instability amplitude is observed for Jet A compared to GS190 at all fuel temperatures. Analysis of the chemiluminescence images shows axial flame fluctuations at the instability frequency that are coupled to oscillations in fuel droplet consumption. Lower fuel temperatures lead to unburnt fuel accumulation in low-velocity regions of the flame, and consumption during the acoustic compression wave arrival results in high heat release magnitude that amplifies acoustic perturbations. Spatial correlations of the axial velocity and heat release fluctuation highlight the flame shear layers as predominant regions driving the global dynamics. Increased fuel temperature results in higher droplet evaporation rates in these regions, which promotes more uniform fuel deposition and subsequent burning over the thermoacoustic cycle, attenuating the instability.

Investigation of Thermal Radiation, Atomization Air, and Fuel Temperature Effects on Liquid Fuel Combustion

Abstract The purpose of the present study is to investigate the effects of radiative heat transfer, atomization air temperature and mass flowrate, and fuel initial temperature on liquid diesel fuel (C16H34) combustion. Fuel is injected by an airblast atomizer inside a model cylindrical combustion chamber. Geometry of the airblast atomizer is modeled in detail so that its impacts on droplet breakup and flow formation are accurately considered. Evaporating fuel spray is simulated by the discrete phase model based on the Eulerian–Lagrangian approach. Turbulent viscosity is numerically computed by the realizable k–ɛ turbulence model while the discrete ordinates model and the steady flamelet model are applied for modeling the radiative heat transfer and combustion, respectively. NO species concentrations are achieved using post-processing. It turns out that neglecting thermal radiation in well-atomized spray combustion only affects high-temperature zones by increasing the axial temperature values of the mixture by almost 8%. Thermal radiation has an imperative effect on producing NO species. Without considering thermal radiation, axial NO concentration becomes almost doubled. Augmentation in mass flowrate and temperature values of atomization air enhances spray formation and combustion efficiency by increasing the evaporation rate. Changing the fuel temperature from 300 K to 325 K rises the total temperature at the end of the centerline of the model combustion chamber by 9.8%. It is shown that increasing the fuel’s initial temperature is not a suitable choice compared to enhancing the temperature and mass flowrate of the atomization air.

Experimental Study on the Effect of Sub-Flash Point Fuel Temperature on the Spread Characteristics of Spill Fire

The spill fires caused by liquid fuel leaks greatly threaten the safety of fuel transportation and storage. In this work, the effect of fuel temperature on the spread characteristics of flowing flames was investigated through n-butanol spilling fire experiments. The spill fire spread can be divided into three stages at different temperatures and leakage rates (I) full spread, (II) gradually extinguished spread, and (III) unable to spread. The oscillation of the flame is related to the fuel thickness and the discharge rate. As the discharge rate or temperature increases, the spread mode changes from pulsation to uniform. With an increase in temperature, the surface flow of the flame is reduced, leading to a decrease in both the preheating time and pulsation amplitude. However, the rate of liquid surface detachment from the flame increases with increasing temperature. The view factor of flame spread can be calculated by the solid flame model, and the flame influences the heat radiation spread state with stable phases or peaks. The research findings presented in this paper hold significant implications for the development of fire safety regulations pertaining to fuel leakage fires.

The influences of flow conditions on heat transfer of supercritical cracked-kerosene

The main component of propulsion system for hypersonic vehicle, such as scramjet, always sustains extremely high thermal loads, and actively regenerative cooling must be considered using its own hydrocarbon fuel as coolant. Due to the limited amount of coolant and the complex physical and chemical problems involved in heat transfer process, the difficulty of cooling channel design increases. In order to explore the ways to improve cooling efficiency, the influences of inlet velocity and flow direction on heat transfer of supercritical cracked-kerosene were investigated via a solid-fluid conjugated simulation method. The results indicate that increasing the coolant velocity can enhance cooling effect with a constant mass flow rate, and the wall temperature at peak heat flux decreased obviously. However, as the wall thickness increases, the enhanced cooling effect is gradually cancelled out. Flow direction has significant influence on heat transfer process. Compared with forward flow, the reverse flow shows considerable uniform wall temperature and low fuel temperature effect. These conclusions can be used as an important reference for cooling channel design under supercritical conditions.

Effect of fuel flexibility on combustion performance of a micro-mixing gas turbine combustor at different fuel temperatures

An H-class gas turbine combustor prototype that employs the micro-mixing combustion technology is first proposed in the current research. It consists of 60 interior jet-in-crossflow micro-mixing nozzles with a distributed arrangement. To analyze the fuel flexibility, a blend of 50% H2 and 50% CO by volume and the pure H2 are considered for the micro-mixing combustor prototype in terms of the design and alternative fuels, respectively. Secondly, this research discusses the fuel temperature effects on the rated and off-design combustion performance for both fuels, because the fuel temperature is an important factor for the power generation efficiency in the gas turbine combined cycles. The results indicate that at the rated fuel temperature of 473 K and off-design ones of 423, 523 and 573 K, the micro-mixing combustor prototype has a great fuel flexibility, in which NO emission is lower than 15 μL/L at 15% O2, outlet temperature distribution factor is lower than 15%, combustion efficiency is higher than 99%, and total pressure recovery factor is higher than 95% for both fuels. Through the trends of combustion performance in different radial planes, it can be found that the high temperature zone of flue gas produced by H2 is longer than H2/CO (50%/50%), and far away the nozzles. Thus, the H2-fired micro-mixing combustor prototype needs a longer axial liner length than H2/CO (50%/50%), in order to realize the enhanced temperature distribution uniformity and combustion efficiency. Eventually, an optimal relationship between the axial liner length and fuel hole diameter is proposed for both fuels based on the trade-offs around the whole combustion performance from the perspective of engineering applications.

Experimental investigation of fuel temperature effects on transient needle motion and injection velocity of solenoid type diesel injector

Real driving emission (RDE) test conducted in sub-zero temperature conditions has been acting as a severe emission regulation over the existing test methods for diesel engines. In order to cope with this tightened regulation, many studies have been conducted to interpret the factors causing the deteriorated diesel engine combustion in cold operation conditions. The deteriorated fuel injection performance has been regarded as one of the key contributing factors but the governing mechanisms are not thoroughly understood so far. This study aims to provide a comprehensive understanding of the effects of fuel temperature including sub-zero conditions on fuel injection performance by measuring the transient needle motion and injection velocity of a diesel injector using synchrotron X-ray imaging techniques. The factors causing the deteriorated injector performance and their contributions are discussed thoroughly based on the results. The results showed that the injection duration was shortened as the fuel temperature decreased as a result of decreased needle opening speed and increased needle closing speed. The increase of fuel viscosity and bulk modulus was discussed as the main factors associated with these results. The total injection mass was reduced by lowering the fuel temperature not only by the shortened injection duration but also by the decreased injection velocity. These factors exerted near equivalent contribution to the reduced injection mass at low fuel temperatures.

Strategies for Fast Fission Matrix Estimation with Fuel Temperature and Control Rod Feedback

Monte Carlo methods are useful for simulating new reactor designs, but even with advances in computing, these methods still require a significant amount of time to perform transient or multiphysics calculations coupled with thermal modeling. This work demonstrates a hybrid reactor physics method that uses Monte Carlo to precalculate an initial database of fission matrix parameters, then combines these results for fast calculations on arbitrary system states. This paper extends previous work that demonstrated these methods on the Penn State Breazeale Reactor (PSBR). Approaches for reducing time and memory cost and increasing the accuracy in reproducing Monte Carlo output are considered. For modeling fuel temperature, a representative temperature distribution is used while tallying the initial fission matrix database. Different approaches for modeling the coupling between individual control rod insertions as well as control and fuel temperature effects are presented as well. Individual solutions are completed in less than 1 s on a single core, and error with respect to Monte Carlo is within 35 pcm for multiplication factor, 0.6% root-mean square, and 2.8% maximum for the normalized three-dimensional fission source distribution on critical, steady-state configurations. Further qualification on different reactor types is needed, but the simplicity and flexibility of this method make further development promising.

Effect of Heavy Liquid Fuel Temperature on The Twin Fluid Atomization Characteristics.(Dept.M|)

Effect of Heavy Liquid Fuel Temperature on The Twin Fluid Atomization Characteristics.(Dept.M|)

Effect of Diesel Fuel Temperature on the Nitrogen Oxides Emission from a Compression-Ignition Engine

Effect of Diesel Fuel Temperature on the Nitrogen Oxides Emission from a Compression-Ignition Engine

Effects of the Initial Gel Fuel Temperature on the Ignition Mechanism and Characteristics of Oil-Filled Cryogel Droplets in the High-Temperature Oxidizer Medium

The ignition mechanism was studied for a group of gel fuel compositions in a high-temperature oxidizer medium. It was determined how the initial temperature of the fuel influences the ignition char...

Estimation of control rod worth, xenon effect on reactivity and power defect of BAEC TRIGA Mark-II research reactor

In this work, control rod worth, xenon (Xe) effect on reactivity and power defect have been measured by doing experiments in the BAEC TRIGA Mark-II research reactor (BTRR) and through established theoretical analysis. Firstly, to study the xenon-135 effect on reactivity, reactor is critical at 2.4 MW for several hours. Next, experiments have been performed at very low power (50 W) to avoid temperature effects. Moreover, for the power defect experiment, different increasing power level has been tested by withdrawing the control rods. Finally, it is concluded that the total control rods worth of the BAEC TRIGA Mark-II research reactor, as determined through this study, is enough to run the reactor at full power (3 MW) considering the xenon-135 and fuel temperature effects.

The Effect of Air Fuel Ratio and Temperature on Syngas Composition and Calorific Value Produced from Downdraft Gasifier of Rubber Wood-Coal Mixture

Rubber wood (Ficus elastica) is one the biomass waste that can be used as raw material for a gasification process and has a calorific value of 4,069 cal/gram. Gasification is a process to convert a solid fuel to syngas (CO, CH4, and H2) through a combustion process using limited air between 20% to 40% of air stoichiometry. Depending on the direction of airflow, the gasifiers are classified as updraft, downdraft, and cross-flow. The downdraft type of gasifier produces a lower tar content than updraft type. The gasification of rubber wood and rubber wood-coal mixture were carried out in this research. The purpose of the research is to determine the effect of Air Fuel Ratio (AFR) and temperature on calorific value and composition of syngas by using a downdraft gasifier. The variations of AFR were 0.64, 0.95, and 1.26. The temperature of gasification was varied between 600oC-1000oC. The result showed that the percentage of CO, H2, and CH4 decreased with increasing of AFR, so decreasing the calorific value. The calorific value of syngas increased along with the temperature. The use of coal in the gasification process can maintain stable combustion the temperatures and increase the syngas produced. The best-operating conditions in the research occurred at AFR of 0.64, the temperature of 800oC and use of coal as a stabilizer. At this condition, the percentage of syngas of 35.95% of CO, 15.95% of H2, 9.38% of CH4, and caloric value of 9,420 MJ/m3 was obtained.

Effects of fuel temperature on injection performance of an EUP system

The fuel temperature has a great influence on the characteristics of an electronic unit pump (EUP) system, especially on the injection performance. This paper studies the regularity of the high-pressure fuel supply system performance at different fuel temperatures. The injection quantity, the injection rate, the fuel pressure, and the needle lift were measured by the EUP system test bench. Investigation results showed that, with the increase of fuel temperature, the injection quantity and maximum injection rate decreased, the time of start injection was delayed, and the peak fuel pressure value decreased. For the needle valve, as the temperature was raised its closing time was advanced at low speed conditions but delayed at high speed conditions. In addition, the empirical equations for the fuel temperature effects on the circulating fuel injection quantity and peak pressure are proposed by the experimental test and simulation data. This study will help to further apply and study the engine, and provide a reference for engine fuel supply control system design.

Analysis of fuel temperature effects on reactivity of light water reactor fuel assemblies by using MVP-2 adopting an exact resonance elastic scattering model

ABSTRACTUsing the continuous-energy Monte Carlo code MVP-2 adopting a resonance elastic scattering model considering the thermal motion of a target nucleus (the exact model) for major heavy nuclides, analysis of fuel temperature effects on reactivity of mockup UO2 and MOX fuel assemblies for light water reactors was performed, and the results were compared with those of the conventional asymptotic model. A base condition was a hot operating condition with an in-channel void fraction of 40% and fuel temperature of 520 ℃ for the BWR fuel assemblies and a hot zero-power condition with fuel temperature of 284 ℃ for the PWR fuel assemblies. The fuel temperature of a high-temperature condition was 1500 ℃ for both types of assemblies. The calculated results showed that the exact model made the neutron multiplication factors at the high-temperature condition lower by −220 to −440 pcm (10−5 Δk) and the Doppler reactivity between the base- and high-temperature conditions more negative by 7% to 10% compared with those obtained by the asymptotic model. The energy-dependent reaction rates of capture and ν-fission were also analyzed to study the detail mechanism in the effect of the exact model on the assembly reactivity.

Influence of fuel temperature on atomization parameters in a pressure-swirl atomizer from a port fuel injector by Shadowgraphy technique

The atomization process that occurs in fuel injectors has a strong relation with the subsequent combustion reaction and thus with the engine thermal efficiency. Experiments were performed to investigate the fuel temperature effect on atomization parameters in a pressure-swirl atomizer. The experimental apparatus consisted of a flow control rig connected with a heat control system. The flow rig was built specifically for that purpose and the heat system goal was to vary the fuel temperature. The atomization parameters were evaluated by means of Shadowgraphy technique. Gasoline and ethanol in different temperatures, from 16 to 55 $$^{\circ }$$ C, were used to provide variation in liquid properties and the same injection pressure (0.3 MPa) was used for both fuels. The results for drop sizing were expressed in terms of Sauter mean diameter (SMD) and the velocity field as well as the particle size distribution measurements were taken into two different axial distances from the nozzle exit. SMD and velocity field were also evaluated as function of injection pressure (from 0.1 to 0.5 MPa) as an additional test. At both distances, 25 and 100 mm, SMD and velocity seemed to be insensitive to the range of temperature used because it provided low variation in fuel properties. On the other hand, particle size distribution allowed the visualization of temperature effect on drop diameters, showing that increasing temperatures decrease droplet sizes, and the comparison between two axial distances allowed seeing the effects of first and second atomization on the spray.

The Effect of Fuel Temperature on the Ethanol Direct Injection Spray Characteristics of a Multi-hole Injector

Ethanol direct injection (EDI) is a new technology to use ethanol fuel more efficiently in spark ignition engines. Fuel temperature is one of the key factors which determine the evaporation process of liquid fuel spray, and consequently influence the combustion and emission generation of the engine. To better understand the mixture formation process of the EDI spray and provide experimental data for engine modelling, experiments were conducted in a constant volume chamber in engine-like conditions. The high speed Shadowgraphy imaging technique was used to capture the ethanol spray behaviours. The experiments covered a wide range of fuel temperature, ranged from 275 K (non-evaporating) to 400 K (flash-boiling). Particularly the transition of the ethanol spray from normal-evaporating to flash-boiling was investigated. The temporal Shadowgraphy spray images, spray tip penetration, angle and projected area were applied to evaluate the evaporation of EDI spray under different fuel temperature conditions. The results showed that the non-evaporating spray's characteristics were similar to the normal-evaporating sprays' in terms of spray tip penetration, angle and projected area. When the fuel temperature increased from 350 K to flash-boiling spray , the spray angle and projected area reduced significantly, but the spray tip penetration increased. Increasing the fuel temperature from 275 K to 325 K did not cause significant increase of the evaporating rate, but with further increase of the fuel temperature, the ethanol spray's evaporation became faster. The transition temperature at which the ethanol spray collapsed at atmospheric pressure was between 355 K and 360 K.

Modeling of Turbulent Natural Gas and Biogas Flames of the Delft Jet-in-Hot-Coflow Burner: Effects of Coflow Temperature, Fuel Temperature and Fuel Composition on the Flame Lift-Off Height

The structure of a turbulent non-premixed flame of a biogas fuel in a hot and diluted coflow mimicking moderate and intense low dilution (MILD) combustion is studied numerically. Biogas fuel is obtained by dilution of Dutch natural gas (DNG) with CO2. The results of biogas combustion are compared with those of DNG combustion in the Delft Jet-in-Hot-Coflow (DJHC) burner. New experimental measurements of lift-off height and of velocity and temperature statistics have been made to provide a database for evaluating the capability of numerical methods in predicting the flame structure. Compared to the lift-off height of the DNG flame, addition of 30 % carbon dioxide to the fuel increases the lift-off height by less than 15 %. Numerical simulations are conducted by solving the RANS equations using Reynolds stress model (RSM) as turbulence model in combination with EDC (Eddy Dissipation Concept) and transported probability density function (PDF) as turbulence-chemistry interaction models. The DRM19 reduced mechanism is used as chemical kinetics with the EDC model. A tabulated chemistry model based on the Flamelet Generated Manifold (FGM) is adopted in the PDF method. The table describes a non-adiabatic three stream mixing problem between fuel, coflow and ambient air based on igniting counterflow diffusion flamelets. The results show that the EDC/DRM19 and PDF/FGM models predict the experimentally observed decreasing trend of lift-off height with increase of the coflow temperature. Although more detailed chemistry is used with EDC, the temperature fluctuations at the coflow inlet (approximately 100K) cannot be included resulting in a significant overprediction of the flame temperature. Only the PDF modeling results with temperature fluctuations predict the correct mean temperature profiles of the biogas case and compare well with the experimental temperature distributions.

Initial Fuel Temperature Effects on Flame Spread over Aviation Kerosene in Low- and High-Altitude Environments

Long-distance petroleum or oil pipelines and aircraft taking off and landing cover a wide range of altitudes in practice. An increase in altitude leads to a decline in atmosphere pressure, as well as a decrease of the partial pressure of oxygen, which may influence the burning behavior of liquid fuels involved in accidental spills. In order to gain understanding on the hazards of spills from aircraft tanks or oil transport networks, experimental work was conducted in Hefei (50 m) and Lhasa (3,650 m) to investigate the effect of initial fuel temperature on flame spread over aviation kerosene both in low- and high-altitude environments. Data shows that flame spread is faster as the initial temperature increases. The transition from liquid-phase to gas-phase-controlled flame spread occurred at the initial fuel temperature of 65°C in Lhasa, but 82.5°C in Hefei. Moreover, for the same initial fuel temperature and under the regime controlled by liquid-phase transport, the rate of flame spread and temperature rise at low altitudes were smaller than those at higher altitudes, while the subsurface convection length and preheating time were larger. Direct evidence was also obtained to show the flame at both altitudes propagated in a pulsating forward-back-forward manner, whereas the average flame pulsation wavelength and frequency at the high altitude were larger than at the low altitude. Theoretical analyse predicts that an increase in initial fuel temperature or altitude led to an increase in fuel evaporation rate, which enhances flame spread and causes unsteady behavior. Given the difference in flame speed, fire accidents at high altitude are potentially more hazardous than those at low-altitude environment.

Fuel property and fuel temperature effects on internal nozzle flow, atomization and cyclic spray fluctuations of a direct injection spark ignition–injector

The effect of fuel properties and fuel temperature on the behaviour of the internal nozzle flow, atomization and cyclic spray fluctuations is examined for a three-hole direct injection spark ignition injector by combining numerical simulation of the nozzle flow with macroscopic and microscopic spray visualization techniques. A dominant influence of the liquid fuel viscosity on the highly unsteady, cavitating nozzle flow and spray formation was observed. A reduced viscosity (or larger Reynolds number) increases the flow velocity, turbulence and cavitation in the nozzle and leads to a slim spray with a reduced width but increased spray penetration. Furthermore, the spray cone angle is larger for lower Reynolds numbers due to the changed internal nozzle flow profile as predicted by the numerical calculation. The shot-to-shot fluctuations of the sprays were found to have their origin in the highly unsteady, cavitating nozzle flow. Larger cyclic spray fluctuations were observed at low Reynolds numbers although the predicted vapour formation in the nozzle is weaker. This can be explained by flow instabilities at low Reynolds numbers leading to large fluctuations in the nozzle flow.

Effects of Fuel Temperature on Injection Process and Combustion of Dimethyl Ether Engine

To investigate the effects of fuel temperature on the injection process in the fuel-injection pipe and the combustion characteristics of compression ignition (CI) engine, tests on a four stroke, direct injection dimethyl ether (DME) engine were conducted. Experimental results show that as the fuel temperature increases from 20 to 40 °C, the sound speed is decreased by 12.2%, the peak line pressure at pump and nozzle sides are decreased by 7.2% and 5.6%, respectively. Meanwhile, the injection timing is retarded by 2.2 °CA and the injection duration is extended by 0.8 °CA. Accordingly, the ignition delay and the combustion duration are extended by 0.7 °CA and 4.0 °CA, respectively. The cylinder peak pressure is decreased by 5.4%. As a result, the effective thermal efficiency is decreased, especially for temperature above 40 °C. Before beginning an experiment, the fuel properties of DME, including the density, the bulk modulus, and the sound speed were calculated by "ThermoData." The calculated result of sound speed is consistent with the experimental results.