In the current study, a new integrated system is provided to prevent waste energy and reduce power consumption. This system consists of a cascade refrigeration system (for cooling) and an Organic Rankine cycle(ORC) (for power generation). These two cycles are combined through a heat exchanger. In fact, this heat exchanger acts as a condenser for the cascade refrigeration cycle and evaporator for ORC. The waste heat of the cascade refrigeration cycle is used to handle the ORC. In this way, a part of the power consumption of the cascade refrigeration cycle is satisfied by ORC. Thermodynamic simulation of the proposed system is carried out via Engineering Equation Solver(EES) software. A parametric study is done to evaluate the effects of the operational parameters on the performance of the integrated system. In addition, different working fluids are used in cascade refrigeration and ORC cycles. The results showed that by using the working fluids of R245fa, R717, and R141b in order in the low-temperature refrigeration cycle, high-temperature refrigeration cycle and ORC, one can produce cooling at -50 ° C and also reduce the power consumption up to 48.69% in the cascade refrigeration cycle.

The second law of thermodynamics and exergy is an important issue in the analysis of propulsion systems that have been highly regarded by researchers in recent years. Studies show that the analysis of the first law in air propulsion systems alone has low scientific value, and for a complete study of a system, the second law and exergy should also be considered. Thermodynamic analysis of supersonic air engines, especially Ramjet and SCRAMJET engines, with the aim of studying their performance, has attracted the attention of many researchers in the last decade. In this method, using thermodynamic laws and exergy analyzes, Ramjet and SCRAMJET motors are systematically analyzed, and their optimal state is extracted. The main purpose of this study is to review and present the latest research findings in this field, focusing on Ramjet and SCRAMJET engines.

Metal powder fuel has high energy and volume calorific values, and it is an excellent power fuel for hypersonic aircraft in the future. However, metal powder has poor flow characteristics and is difficult to be effectively mixed with air when supersonic air is injected. The mixing degree of fuel and air is an important factor to the efficiency of the engine. One way to solve this problem is to introduce a jet (the primary jet) upstream of the powder fuel inlet to improve the mixing degree of fuel and increase the residence time. In this study, a doublehole jet two-dimensional SCRAMJET combustor structure was established, the effects of different initial jet conditions on the performance of SCRAMJETs was studied and analyzed. The results show that the introduction of the primary jet can effectively improve the mixing degree of the powdered fuel and air in the combustion chamber, prolong the residence time of the particles in the combustion chamber and improves the combustion efficiency of the metal powder. However, both the combustion efficiency of the metal powder fuel and engine thrust increase and then decrease when the mass flow rate of the primary jet increases.

A multi-stage open cooling cycle of SCRAMJET for electricity and hydrogen co-production is proposed in which the fuel of SCRAMJET is used as a coolant of the cooling cycle. Thermodynamic and exergetic examinations of the advanced system have been conducted to appraise the performance of the cycle, electricity and hydrogen production. In this integral system, the waste heat of SCRAMJET drives the power sub-cycle whilst the PEM electrolyzer input electricity is supplied by a portion of the net electricity output of the cycle. It is fi gured out that the multi-expansion process reveals more advantages in comparison to the single-expansion process in terms of more cooling capacity, electricity, and production. For the fuel mass fl ow 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 rate is attained 42. 16 kg/h. On the other hand, the exergetic analysis results have proved the fact that the PEM electrolyzer has the highest exergy destruction ratio by 48% among all components of the cycle. In this case, the energy and exergy effi ciencies of the overall set-up are acquired by 12. 95% and 22. 16%, correspondingly. The outcomes of parametric evaluation demonstrated that electricity and hydrogen productions are directly proportional to the backpressure of the pump accordingly, more electricity and hydrogen are generated by higher backpressure. But, increasing the mass fl ow rate of fuel does not have any tangible impact on energy and exergy effi ciency of the whole set-up thus both remain approximately constant.

A numerical analysis of the inlet-combustor interaction and flow structure through a SCRAMJET engine at a flight Mach number M=6 with parallel injection (Strut with circular inlet) is presented in the present research article. Three different angles of attack (a=-4o, a =0o a =4o) have been studied for parallel injection.The SCRAMJET configuration used here is a modified version of DLR SCRAMJET model. Fuel is injected at supersonic speed (M=2) through a parallel strut injector. For parallel injection, the shape of the strut is chosen in a way to produce strong stream wise vorticity and thus to enhance the hydrogen/air mixing inside the combustor. These numerical simulations are aimed to study the flow structure, supersonic mixing, and combustion phenomena for the three different types of geometries along with circular shaped strut configuration.

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%.

Efficient combustion in the SCRAMJET combustors depends on the proper air-fuel mixing. Sufficient mixing between the supersonic airstream and the fuel jet is critical for designing of SCRAMJET engines, and this is due to the very short residence timescale for the mixture in supersonic flows. The fluid residence time is only about of the order of milliseconds in a SCRAMJET engine, and therefore injection and spreading of the fuel is an important issue. In this paper staged transverse injection of sonic circular jets into supersonic crossflows behind a step has been studied numerically. In comparison with parallel injection, Transverse injection provides better fuel penetration with sufficient mixing and heat release but imposes larger stagnation pressure loss. Three-dimensional Reynolds Averaged Navier-Stokes equations and k-ω sst turbulence model and the perfect gas equation have been solved by using Fluent software. The results of the numerical solution are compared and validated with available experimental data. Numerical results showed good agreement with the experimental values. The simulations correctly captured the location and shape of the main flow features. The flow filed consists of various shock waves such as bow shocks, separation-induced shocks, and barrel shocks. Results showed that Mach disc height of the second injector is larger than first injector that is due to the stagnation pressure loss of the first injection.

SERN (Single Expansion Ramp Nozzle) nozzles often used in many aerospace vehicles with SCRAMJET engines. Employment of SERN nozzles results in reducing the frictional drag and weight of nozzle and also they produce extra lift. A numerical study of supersonic gas flow in SERN nozzles is presented in this paper. The Navier-Stokes equations are solved with using a FORTRAN code. The governing equations are conservation of mass, momentums, energy and state equation of perfect gas for two dimensional compressible viscose flow. Equations are solved with using time-marching method. For verification, the results of recent numerical solution are compared with experimental results and results of Fluent and results of method of characteristics (MOC) and comparisons show good agreement with experimental results and other numerical solutions.

Transverse fuel injection in supersonic crossflow of SCRAMJET combustors is one of the common methods for fuel-air mixing. Air jet injection before fuel jet can improve fuel penetration but with the excess stagnation pressure loss. In this paper, the position of air jet is changed to find the position that maximum fuel jet penetration height and minimum stagnation pressure loss is achieved. For numerical simulations, Two-dimensional Navier-Stokes equations and k-ω,sst turbulence model and the perfect gas equation are solved. Then the results of the numerical solution are compared and validated with experimental data. Numerical results showed good agreement with the experimental values. In the experimental test, Helium is injected into supersonic crossflow and so numerical simulation is started with Helium injection. In SCRAMJET usually, hydrogen was used as fuel. Therefore, hydrogen fuel injection is used for the parametric study. In the case of air injection near the fuel injection, maximum fuel penetration with minimum stagnation pressure loss is achieved.

Due to the fact that the velocity of air flow in the combustion chamber of SCRAMJETs is supersonic, so there is not enough time for proper mixing of fuel and air at these high speeds, and studying the process of mixing of fuel and air in this situation is one of the important issues for SCRAMJET engine design. One of the most widely used methods of fuel injection in supersonic flows of SCRAMJET engine combustion chambers is the method of transverse injection into supersonic air crossflow. Since the velocity of the passing air is very high in such streams, it is challenging to achieve a suitable mixture for combustion. In the present work, by solving the three-dimensional Reynolds-Averaged-Navier-Stokes equations with the k-ω sst turbulence model and the ideal gas state equation, the transverse injection domain in the supersonic flow is numerically simulated and the effect of injection diameter is investigated based on the mixing properties such as fuel penetration depth, mixing efficiency, effective mixing area ratio and stagnation pressure losses. After that, results of reactive flow are presented.