Explosion damage effects of aviation kerosene storage tank under strong ignition

In order to study the blast damage effects of aviation kerosene storage tanks,the out-field explosion experiments of 8 m3fixed-roof tanks were carried out.The fragments,shock wave and fireball thermal radiation of the tank in the presence of bottom oil,half oil and full oil,as well as empty tank,were investigated under internal explosion by various TNT charge contents(1.8 kg,3.5 kg and 6.2 kg).The results showed that the tank roof was the only fragment produced,and the damage forms could be divided into three types.The increase of TNT charge content and oil volume enlarged the deformation of the tank,while the hole ratio presented a trend of increase first and then decrease.The H_r,maxand V_(max)values positively increased as increasing the TNT charge content and oil volume(from empty to half oil),but decreased in full oil.The Pmaxvalues had a progressive increase with the increment of TNT charge content,but not the case with the increase in oil volumes.The development of fireball was divided into three stages:tank roof‘towed'flame,jet flow flame tumbling and rising,and jet flow flame extinguishing.The Dmaxand Hf,maxvalues both increased as increasing TNT charge content and oil volumes.The oscillation phenomenon of fireball temperature was observed in the cooling process.The average temperature of fireball surface was positively correlated with TNT charge content,and negatively correlated with oil volumes.

Tribology behavior of double-glow discharge Mo layers on titanium alloy in aviation kerosene environment

In order to improve the tribology behavior in aviation kerosene, molybdenum （Mo） modified layers were fabricated on Ti6Al4V base alloy using a double-glow plasma surface alloying technique. The morphology, microstructure, microhardness and element depth distribution of the Mo modified layers were studied. The tribology properties of Ti6Al4V base alloy, Mo modified layers and 5CrMnMo tool steel sliding with GCr15 steel or QSn4-3 copper alloy counterparts in aviation kerosene were comparatively researched. The effect of roughness on the sliding wear behavior was discussed. The results indicate that the Mo modified layers with polishing treatments not only reduce the friction coefficient of Ti6Al4V base, but also enhance the wear resistance of the counterparts. The Mo modified layers have better tribology behavior than 5CrMnMo steel. It is also found that the wear volume loss of the counterparts is proportional to the value of roughness of Mo modified layers, which is related directly to the ploughing wear between micro convex bodies of the layers and counterparts.

Numerical study on non-uniform heat transfer deterioration of supercritical RP-3 aviation kerosene in a horizontal tube

The convective heat transfer of supercritical-pressure RP-3(Rocket Propellant 3)aviation kerosene in a horizontal circular tube has been numerically studied,focusing mainly on the non-uniform heat transfer deterioration along the circumferential direction.The governing equations of mass,momentum and energy have been solved using the pressure-based segregated solver based on the finite volume method.The re-normalization group(RNG)k-εturbulence model with an enhanced wall treatment was selected.Considering the heat conduction in the solid wall,the mechanism of heat transfer deterioration and the buoyancy effect on deteriorated heat transfer were discussed.The evolution of secondary flow was analyzed.Effects of the outer-wall heat flux,mass flux,pressure and tube thermal conductivity on heat transfer were investigated.Moreover,the buoyancy criterion and the heat transfer correlation were obtained.Results indicate that the poor flow performance of near-wall fluid causes the pseudo-film boiling,further leads to the heat transfer deterioration.The strong buoyancy has an effect of enhancing the heat transfer at the bottom of tube,and weakening the heat transfer at the top of tube,which results in the non-uniform inner-wall temperature and heat flux distributions.Decreasing the ratio of outer-wall heat flux and mass flux,increasing the pressure could weaken the heat transfer difference along the circumferential direction,while the effect of thermal conductivity of tube on the circumferential parameters distributions is more complicated.When the buoyancy criterion of(Grq/Grth)max≤0.8 is satisfied,the effect of buoyancy could be ignored.The new correlations work well for non-uniform heat transfer predictions.

The Effect of Ignition Parameters on the Combustion Characteristics of an Aviation Piston Engine

A cylinder combustion simulation model was established for a two-stroke aviation piston engine used in a small unmanned aerial vehicle. The influence of different ignition system parameters on the combustion process of aviation kerosene was studied using this model. The research results showed that under the working conditions of 5500 r/min and 50% throttle opening, as the ignition energy increased, the peak values of average cylinder pressure and average temperature increased, and the combustion duration shortened, The advance of the combustion center of gravity increases the tendency of the engine to knock. Under the same operating conditions, as the ignition timing advances, the peak values of average pressure and average temperature in the cylinder increase, gradually approaching the top dead center, and the tendency of engine detonation increases more significantly.

Numerical investigation on flow and convective heat transfer of aviation kerosene at supercritical conditions

In this paper,characteristics of flow and convective heat transfer of China RP-3 kerosene in straight circular pipe were numerically studied.Navier-Stokes equations were solved using RNG k-turbulence model with low Reynolds number correction.The thermophysical and transport properties of the China RP-3 kerosene were calculated with a 10-species surrogate and the extended corresponding state method(ECS) combined with Benedict-Webb-Rubin equation.The independence of grids was first studied and the numerical results were then compared with experimental data for validation.Under flow conditions given in the paper,the results show that deterioration of convective heat transfer occurs when the wall temperature is slightly higher than the pseudo-critical temperature of kerosene for cases with wall heat flux of 1.2 and 0.8 MW/m 2.The degree of the heat transfer deterioration is weakened as the heat flux decreases.The deterioration,however,does not happen when the heat flux on the pipe wall is reduced to 0.5 MW/m 2.Based on the analysis of the near-wall turbulent properties,it is found that the heat transfer deterioration and then the enhancement are attributed partly to the change in the turbulent kinetic energy in the vicinity of pipe wall.The conventional heat transfer relations such as Sieder-Tate and Gnielinski formulas can be used for the estimation of kerosene heat convection under subcritical conditions,but they are not capable of predicting the phenomenon of heat transfer deterioration.The modified Bae-Kim formula can describe the heat transfer deterioration.In addition,the frictional drag would increase dramatically when the fuel transforms to the supercritical state.

Effect of dicarboxylic acid esters on the lubricity of aviation kerosene for use in CI engines

To reduce their fuel related logistic burden,North Atlantic Treaty Organization(NATO)Armed Forces are advancing the use of a single fuel for both aircraft and ground equipment.To this end,F-34(the commercial equivalent is Jet A-1)is replacing distillate diesel fuel in many applications.However,tests conducted with this kerosene type on high frequency reciprocating rig showed that this type of fuel causes unacceptable wear.This excessive wear is caused by the poor lubricity of aviation fuel.In order to make this type of fuel compatible with direct injection compression engines,seven di-carboxylic acid esters have tested to improve the lubricity of kerosene.Tribological results showed that all esters tested in this series of experiments seem to be suitable for increasing the kerosene lubricity to a satisfactory level.

Numerical Investigation of Boundary Grid Effect on Heat Transfer Computation of RP-3 at Supercritical Temperature of Helical Tube Wall

To get reliable computational results,the RNG k-ε turbulence model with enhanced wall treatment was validated to solve the heat transfer of supercritical RP-3 in a helically coiled tube,and models of the thermo-physical properties of RP-3 were optimally chosen.Most significantly,the grid independence was validated by two-step procedure,and the effect of boundary grids of the supercritical-temperature wall on the computational accuracy was well studied.Through adjusting boundary-layer girds' size,four regions (increased,pseudo-convergence,decreased and convergence) of the outlet temperature Tout were obtained and analyzed.The results showed that the maximum computation errors of Tout and the pressure differential between the inlet and outlet ΔP reached 20.65% and 98.15%,respectively,indicating that boundary grids have a significant influence on computation of flow and heat transfer.Based on this,a dimensionless distance from the wall-adjacent cell to the wall y+=Prw-1/1.78 (Prw denotes Wall Prandtl number) was recommended as a convergence point.The variation laws of viscous length scale y* were discussed under different structural parameters,operation parameters,and helical lengths.An explicit model of y* was proposed to calculate the height (y) of the first boundary layer grids and refine boundary grids efficiently.A modified model for coefficient of fiiction factor Cf was proposed based on Rogers's,and Nusselt number Nu was proposed based on an analogy of momentum and heat transfer.The above models about y*,Cf and Nu could apply to both the entrance region and the whole tube length,and showed good performance when Reynolds number was extended to above 70 000,or whenever the outlet temperature is below or above the critical point.

The Design and Performance of a High Temperature Rise Combustor for Wind Tunnel

A high-temperature-rise combustor that can be used in high-temperature wind tunnel is introduced in this study.Aviation kerosene is used in this type of combustor,with division combustion scheme and evaporator fuel-supply device adopted.In the performance test under atmospheric pressure,when the inlet temperature is 500K and air flow is within the range of 1.5-3.0 kg/s,the outlet temperature can be precisely regulated within the range of 1050K-2100K.Moreover,higher uniformity of outlet temperature distribution and higher combustion efficiency can be achieved.After the long-time working in the wind tunnel,various components of the combustor,especially the combustor liners are checked without finding any anomaly such as thermal deformation.

Frictional resistance of supercritical pressure RP-3 flowing in a vertically downward tube at constant heat fluxes

Based on the demands of compact heat exchangers and micro cooling channels applied for aviation thermal protection, the flow resistance characteristics of aviation kerosene RP-3 were experimentally studied in a vertically downward circular miniature tube with an inner diameter of 1.86 mm at supercritical pressures and constant heat fluxes. A long and short tube method was used to accurately calculate the frictional pressure drop, and experimental conditions are supercritical pressures of 4 MPa, mass flow rates of 2–4 g/s(i.e., mass fluxes of 736–1472 kg/(m^(2)·s)), heat fluxes of 100–500 kW/m^(2), and inlet temperatures of 373–673 K. Results show that the sharp variations of thermophysical properties, especially density, have significant influences on frictional resistances.Generally, the frictional pressure drop and the friction factor increase with increasing inlet temperatures, and this trend speeds up in the relatively high-temperature region. However, the friction factor has a sudden decline when the fuel outlet temperature exceeds the pseudo-critical temperature.The frictional pressure drop and the friction factor basically remain unchanged with increasing heat flux when the inlet temperature is relatively low, but increase quickly when the inlet temperature is relatively high. Besides, a larger mass flux yields a higher pressure drop but does not necessarily yield a higher friction factor. Finally, an empirical friction factor correlation is proposed and shows better predictive performance than those of previous models.