جستجوی مقالات مرتبط با کلیدواژه « اسکرمجت » در نشریات گروه « مکانیک »

A novel scramjet multi-stage open cooling cycle for electricity and hydrogen co-production is proposed in which the fuel of scramjet is used as coolant of cooling cycle. Thermodynamic and exergetic examination of the advanced system have been conducted to appraise the system’s performance, electricity and hydrogen productions and multi-expansion effects. For the fuel mass flow rate of 0.4 kg/s, the cooling capacity of the new proposed cycle is computed 9.16 MW, the net electricity output is calculated about 3.38 MW and the hydrogen production is attained 42.16 kg/h. On the other hand, the exergetic results have proved the fact that PEM electrolyzer has the highest exergy destruction ratio by 44% among different components of the cycle. Moreover, the results of exergy analysis exhibited that employing the multi-expansion process concept outstandingly decline the overall exergy destruction of the system. In this case, the energy and exergy efficiencies of the overall set-up are acquired by 13.01% and 22.12%, correspondingly

A numerical study on combustion phenomenon in a scramjet combustion chamber with fuel injection from different wedge angles (11, 12, 17 and 20 degrees) was done. In this combustion chamber, the Mach numbers of inflow air and hydrogen fuel are 2 and 1 respectively. The considered turbulent flow field was simulated by RANS equations in steady state form. In the present simulations, a realizable k   turbulence model was selected for turbulence simulation and also finite-rate/eddy-dissipation model was used for combustion simulation. A comparison was done between numerical and experimental results and accuracy of numerical method verified. These simulations were performed in Ansys Fluent commercial software. Results showed that with increase of wedge angle, the combustion efficiency rises from 63 to 67 percent. On the other hand, an increase in wedge angle results in stronger shock waves and also total pressure loss increases. Therefore, a compromise should be done by designer from both sides to get an efficient thrust.

To improve the mixing of fuel and air in supersonic flows, various methods are used, including the implementation of a ramp ahead of the injection port. In the present work, the effect of ramp height on the area of double hydrogen jet cross-jet flow in supersonic airflow has been investigated numerically and the effect of ramp height on parameters such as mixing efficiency, effective mixing area ratio and stagnation pressure losses has been investigated. Numerical simulations have been performed using the solution of the three-dimensional Reynolds-Averaged Navier-Stokes equations with the two-equation sst k-ω turbulent model. Initially, the results of the numerical solution are validated with the experimental data. It was shown that the numerical solution results have good agreement with experimental data. Then, the effect of the presence of a ramp upstream of the injection port is numerically investigated for several ramps with different heights. The results show that by increasing the height of the ramp from zero to 6 mm, the mixing efficiency at the exit plane increases from 0.37 to 0.52 and the effective mixing area ratio at the exit plane increases from 0.059 to 0.1. Stagnation pressure losses also increase from 8% to 9%.

In this paper, the combustion process in a prototype scramjet (DLR) is numerically simulated and studied. To that end, the scramjet is initially simulated and validated in the non-reacting condition. The results show that the method used has the ability to predict the fields of velocity and pressure with appropriate accuracy. Then, the same scramjet is simulated and validated for the reacting case by considering one-reaction model. The results of these two simulations illustrates that the maximum distance of subsonic area from the strut is 141 mm in the reacting case while this distance is only 22 mm in the non-reacting case. the waves pass through the jet region with a slight deviation in the non-reacting case while they are reflected after hitting the jet region in the reacting case.the waves pass through the jet region with a slight deviation in the non-reacting case while they are reflected after hitting the jet region in the reacting case.

The design of space launch vehicles that can be reused can significantly reduce the cost of space missions. These launch vehicles should be equipped with engines that are capable of proper operation in the supersonic and hypersonic flow regimes. The design of the air intake of these engines is a key challenge. One of the most important issues affecting the performance of these engines is the shocks that are expected at the entrance to the engine. The flow of air from these shocks provides conditions for stable combustion in the engine. The air intake efficiency of these engines is optimized in several ways. In this study, the attempt to optimize a supersonic air intake using the magnetohydrodynamic method has been developed as an advanced flow control technique. The results of this study showed that the MFR parameter increased by 21.62%, the mean temperature increased by 10.51%, pressure recovery of the exhaust particles towards the combustion chamber increased by 14.5%, and the flow distortion decreased by 18.93%.