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This study aims to get the essential data of the solubility and diffusion coefficient of gas in jet fuel for appropriately designing a kind of on-board inert gas generation system.

A test apparatus based on pressure–decay method was constructed to measure solubility and diffusion coefficient of gas in liquid. The test apparatus and method were verified via measurement of solubility and diffusion of CO₂ in the pure water.

The solubility of CO₂ and O₂ in RP-3 jet fuel with the temperature from 253 to 313 K under three various pressures were measured and compared with theoretical value calculated by a relative density method provided in the standard of ASTM D2780-92, and the deviation is within 10 per cent. The diffusion coefficients of CO₂ and O₂ in RP-3 jet fuel are determined by monitoring the gas pressure in a hermetic cell versus time with the temperature from 253 to 333 K. The measured diffusivity-temperature relation can be well fitted through the Arrhenius equation for engineering applications. The obtained correlation can be used to predict the diffusion coefficient of CO₂ and O₂ in RP-3 jet fuel under a wide temperature range.

The semi-empirical correlation of solubility and diffusion coefficient in RP-3 jet fuel obtained from the experimental data could be used to support the design of an inert gas generation system.

There are no essential data of solubility and diffusion of CO₂ and O₂ in RP-3 jet fuel; therefore, it is fatal if the quantity and rate of mass transfer of CO₂ and O₂ in RP-3 jet fuel must be assessed, e.g. during the design of green on-board inert gas generation system.

The purpose of this study is to measure the mass diffusion coefficient of nitrogen in jet fuel using digital holography interferometry for cost-effective designing and modeling of the aircraft tank inerting system.

The mass diffusion coefficients of N₂ in RP-3 and RP-5 jet fuels were measured by digital holography interferometry at temperatures ranging from 278.15 to 343.15 K. The Arrhenius equation is used to adequately describe the relationship between mass diffusion coefficients and temperature. The viscosities of RP-3 and RP-5 jet fuels were also measured to examine the accuracy of the Stokes–Einstein model in calculating mass diffusion coefficients.

As temperature increases from 278.15 to 343.15 K, the mass diffusion coefficients increase 4.23-fold for N₂ in RP-3 jet fuel and 5.13-fold for N₂ in RP-5 jet fuel. The value of Dµ/T is not constant as the Stokes–Einstein equation expressed, but is a weak linear function of temperature.

A more accurate diffusion model is proposed by fitting the measured Dµ/T with the temperature and calculating the mass diffusion coefficients of N₂ in RP-3 and RP-5 jet fuels within 10 per cent relative deviation.

A measurement system for mass diffusion coefficients of N₂ in RP-3 and RP-5 jet fuels was constructed based on the digital holography interferometry. The mass diffusion coefficient can be expressed by a uniform polynomial function of temperature and viscosity.

The purpose of this paper is to compare the combustion characteristics, including the combustion pressure, heat release rate (HRR), coefficient of variation (COV) of indicated mean effective pressure (IMEP), flame development period and combustion duration, of aviation kerosene fuel, namely, rocket propellant 3 (RP-3), and gasoline on a two-stoke spark ignition engine.

This paper is an experimental investigation using a bench test to reflect the combustion performance of two-stroke spark ignition unmanned aerial vehicle (UAV) engine on gasoline and RP-3 fuel.

Under low load conditions, the combustion performance and HRR of burning RP-3 fuel were shown to be worse than those of gasoline. Under high load conditions, the average IMEP and the COV of IMEP of burning RP-3 fuel were close to those of gasoline. The difference in the flame development period between gasoline and RP-3 fuel was similar.

Gasoline fuel has a low flash point, high-saturated vapour pressure and relatively high volatility and is a potential hazard near a naked flame at room temperature, which can create significant security risks for its storage, transport and use. Adopting a low volatility single RP-3 fuel of covering all vehicles and equipment to minimize the number of different devices with the use of a various fuels and improve the application safeties.

Most two-stroke spark ignition UAV engines continue to combust gasoline. A kerosene-based fuel operation can be applied to achieve a single-fuel policy.

The purpose of this paper is to investigate the knock combustion characteristics, including the combustion pressure, heat release rate (HRR) and knock intensity of aviation kerosene fuel, that is, Rocket Propellant 3 (RP-3), on a port-injected two-stoke spark ignition (SI) engine.

Experimental investigation using a bench test and the statistical analysis of data to reflect the knock combustion characteristics of the two-stroke SI unmanned aerial vehicle (UAV) engine on RP-3 kerosene fuel.

Under the full load condition of 4,000 rpm, at the ignition timing of 25 degree of crank angle (°CA) before top dead centre (BTDC), the knock combustion is sensitive to the thinner mixture; therefore, the knock begins to occur when the excess air ratio is larger than 1.0. When the excess air ratio is set as 1.2, the knock obviously appears with the highest knock intensity. At the excess air ratio of 1.2, better engine performance is obtained at the ignition timing range of 20-30 °CA BTDC. However, the ignition timing at 30° CA BTDC significantly increases the peak combustion pressure and knock intensity with the advancing heat release process.

Gasoline has a low flash point, a high-saturated vapour pressure and relatively high volatility, and it is a potential hazard near a naked flame at room temperature, which can create significant security risks for its storage, transport and use. The authors adopt a low-volatility single RP-3 kerosene fuel for all vehicles and equipment to minimise the number of different devices using various fuels and improve the military application safety.

Most two-stroke SI UAV engines for military applications burn gasoline. A kerosene-based fuel for stable engine operation can be achieved because the knock combustion can be effectively suppressed through the combined adjustment of the fuel amount and spark timing.

The purpose of this paper is to investigate power performance, economy and hydrocarbons (HC)/carbon monoxide (CO) emissions of diesel fuel on a two-stoke direct injection (DI) spark ignition (SI) engine.

Experimental study was carried out on a two-stroke SI diesel-fuelled engine with air-assisted direct injection, whose power performance and HC/CO emissions characteristics under low-load conditions were analysed according to the effects of ignition energy, ignition advance angle (IAA), injection timing angle and excess-air-ratio.

The results indicate that, for the throttle position of 10%, a large IAA with adequate ignition energy effectively increases the power and decrease the HC emission. The optimal injection timing angle for power and fuel consumption is 60° crank angle (CA) before top dead centre (BTDC). Lean mixture improves the power performance with the HC/CO emissions greatly reduced. At the throttle position of 20%, the optimal IAA is 30°CA BTDC. The adequate ignition energy slightly improves the power output and greatly decreases HC/CO emissions. Advancing the injection timing improves the power and fuel consumption but should not exceed the exhaust port closing timing in case of scavenging losses. Burning stoichiometric mixture achieves maximum power, whereas burning lean mixture obviously reduces the fuel consumption and the HC/CO emissions.

Gasoline has a low flash point, a high-saturated vapour pressure and relatively high volatility, and it is a potential hazard near a naked flame at room temperature, which can create significant security risks for its storage, transport and use. The authors adopt a low volatility diesel fuel for all vehicles and equipment to minimise the number of different devices using various fuels and improve the potential military application safety.

Under low-load conditions, the two stroke port-injected SI engine performance of burning heavy fuels including diesel or kerosene was shown to be worse than those of gasoline. The authors have tried to use the DI method to improve the performance of the diesel-fuelled engine in starting and low-load conditions.

This paper aims to comprehensively clarify the research status of thermal transport of supercritical aviation kerosene, with particular interests in the effect of cracking on heat transfer.

A brief review of current research on supercritical aviation kerosene is presented in views of the surrogate model of hydrocarbon fuels, chemical cracking mechanism of hydrocarbon fuels, thermo-physical properties of hydrocarbon fuels, turbulence models, flow characteristics and thermal performances, which indicates that more efforts need to be directed into these topics. Therefore, supercritical thermal transport of n-decane is then computationally investigated in the condition of thermal pyrolysis, while the ASPEN HYSYS gives the properties of n-decane and pyrolysis products. In addition, the one-step chemical cracking mechanism and SST k-ω turbulence model are applied with relatively high precision.

The existing surrogate models of aviation kerosene are limited to a specific scope of application and their thermo-physical properties deviate from the experimental data. The turbulence models used to implement numerical simulation should be studied to further improve the prediction accuracy. The thermal-induced acceleration is driven by the drastic density change, which is caused by the production of small molecules. The wall temperature of the combustion chamber can be effectively reduced by this behavior, i.e. the phenomenon of heat transfer deterioration can be attenuated or suppressed by thermal pyrolysis.

The issues in numerical studies of supercritical aviation kerosene are clearly revealed, and the conjugation mechanism between thermal pyrolysis and convective heat transfer is initially presented.

Determining the variation law of the oxygen concentration in the ullage space of the fuel tank is the key to the design of the inert system. Among various factors affecting the oxygen concentration in the ullage space of the fuel tank, the temperature difference between day and night shows particular importance while relevant analysis and calculation are scarce.

This study establishes a theoretical simulation model of the central wing fuel tank of an aircraft according to the relevant provisions of day-night temperature variation in FAR25 airworthiness regulations, verifies the model with the existing experimental data and discusses the corresponding relationship between the oxygen concentration in the ullage space of the fuel tank and the day-night temperature difference. The influence of day and night temperature difference, fuel type, fuel load rate, initial oxygen concentration, dissolved oxygen evolution and other factors on the oxygen concentration in the ullage space of the fuel tank were analyzed, and the limit of initial oxygen concentration of the fuel tank before the shutdown at night meeting the requirements of the airworthiness provisions was proposed.

The results show that the temperature difference between day and night, fuel load rate, initial oxygen concentration and other factors have different effects on the oxygen concentration in the ullage space of fuel tank. The initial oxygen concentration limit before shutdown shall be 2% below the 12% oxygen concentration stipulated by FAA.

The research results in this paper will be of good reference value to the design of the inert system and the calculation of the flammability exposure evaluation time. This paper aims to be good reference of the design of the inert system and the calculation of the flammability exposure evaluation time.

The research results of this paper can provide practical guidance for the current civil airworthiness certification work.

This paper aims to present experimental experience of heavy fuelling of a spark ignition crankcase scavenged two-stroke cycle unmanned aerial vehicle (UAV) engine, particularly focusing on the effects of compression ratio variation, and to cross-correlate with the results of fluid dynamic modelling of the engine and fuels used.

One-dimensional modelling of the engine has been conducted using WAVE software supported by experimental dynamometer testing of a spark ignition UAV engine to construct a validated computational model using gasoline and kerosene JET A-1 fuels.

The investigation into the effects of compression ratio variation via fluid dynamic simulation and experimental testing has allowed an assessment of the approach for improving heavy fuel operation of UAV engines using auxiliary transfer port fuel injection. The power level achieved with reduced compression ratio heavy fuel operation is equal to 15.35 kW at 6,500 revolutions per minute compared to 16.27 kW from the standard gasoline engine or a reduction of 5.7%.

The studied engine is specifically designed for UAV applications. The validation of the computational models to explore the effects of compression ratio and heavy fuel injection on the solution and cost is supported by experimental tests.

The application of auxiliary port fuel injection of heavy fuel and associated compression ratio optimisation offers an alternative approach to achieve the safety and logistical challenges of the single fuel policy for UAVs. The application of WAVE to simulate crankcase scavenged two-stroke cycle engines has been applied in very few cases. This study shows further exploratory work in that context.

This study aims to contrastively investigate the effects of biodiesel and diesel on the power, economy and combustion characteristics of a compression ignition aviation piston engine for unmanned aerial vehicles.

Biodiesel used as alternative fuel will not be mixed with diesel during experimental study. Pure diesel fuel is used for the comparative test. Same fuel injection strategies, including pilot and main injection, are guaranteed for two fuels in same test points.

The engine-rated power of biodiesel is lower than diesel, which results in higher specific fuel combustion (SFC) and effective thermal efficiency (ETE). Biodiesel has the faster burning rate, shorter combustion duration. The crank angle of 50% mass fraction burned (CA50) is earlier than diesel. The ignition delay angle of biodiesel and diesel in the pilot injection stage is almost the same at high engine speed. As the speed and load decrease, the ignition delay angle of biodiesel in the pilot injection stage is smaller than diesel. At 100% high load conditions, the fuel-burning fraction of biodiesel in the pilot injection is the same as diesel. The peak heat release rate (HRR) of biodiesel is slightly lower than diesel. At 20% part load conditions, the fuel-burning fraction of biodiesel in the pilot injection stage is lower than diesel. Because of the combustion participation of unburned pilot injected fuel, the peak HRR of biodiesel in the main injection is equal to or even higher than diesel.

The application feasibility of alternative fuel and its effects on aviation engine power, economy and combustion characteristics will be evaluated according to the “drop-in“ requirements and on the low-cost premise without changing the aviation engine structure and parameters.

The purpose of this paper is to present a computational fluid dynamic simulation for the investigation of the particles segregation phenomenon in the gas–solid fluidized beds.

These particles have the same size and different densities. The k–ε model and multiphase particle-in-cell method have been utilized for modeling the turbulent fluid flow and solid particles behaviors, respectively. The coupled equations of the velocity and pressure have been solved by using a combination of SIMPLE and PISO algorithms. After validating the simulation, different mixing indices, with different calculation bases, have been investigated, and it has been found that the Lacey mixing index, which was defined based on statistical concepts, is suitable to investigate the segregation/mixing phenomena of this bed in different conditions. Finally, the effects of parameters such as velocity, particle density ratio, jetsam concentration, and initial arrangement on the segregation/mixing behaviors of the bed have been studied.

The results show that the increase in the superficial gas velocity decreases the mixing index to a minimum value and then increases this index in the beds with mixed initial condition, unlike the beds with separated initial condition. Moreover, an increase in the particle density ratio increases the minimum fluidization velocity of the bed, and also the amount of segregation, and increase in the jetsam concentration increases the value of the mixing index.

A computational fluid dynamics simulation has been presented for the particles segregation phenomenon in the gas–solid fluidized beds.