5 samples of one kind of one-fluid swirl injector which has been designed and manufactured by CNC have been tested. Mentioned injector has a spray cone in the shape of very thin layer because an air core is formed inside the injector. In order to detect acceptable injector among them, characterization tests have been done in the laboratory for all. The methods of experimental characterization have been described in detail. In these tests, injection uniformity, symmetry, mass flow rate versus pressure difference and some other parameters such as spray cone angle are investigated. The results show good agreement between theoretical predictions and experiment. Finally, one injector has been selected as a suitable and nearer to theoretical design injector among them.

In this paper, the operating parameters of a swirl injector were studied as a function of Reynolds number (Re) and Weber number (We). Spray cone angle, liquid sheet breakup length and injector discharge coefficient are the parameters which their dimensionless variations were studied to characterize the injector behavior in terms of Re and We. At the end, these experimental results were compared with those of some famous models, such as LISA. All the experiments were prformed using a simplex swirl injector. Moreover, water was used as the operating fluid sprayed in atmospheric conditions. The Shadowgraphy imaging method was used to visualize the injection spray. Experimental results show that by increasing Re, the injection regime varies from Dripping Mode to Atomization Mode at Re=3´104, and by further increasing Re, the fully developed mode (that creates a clear conical sheet) is achieved at Re=3.7´104. Also, results show that the breakup length varies with We-0.5Re0.6 linearly. Although increasing Re initially increases the spray cone angle, but beyond a specific Re, this trend is stopped.

In this paper, design and calculation method of a swirl injector with tangential inlets has been presented considering some known assumption. The injector designed based on the above method has been manufactured using CNC. Formation and development phenomena of air core within swirl injectors and their simulation is complicated due to two-phase swirl turbulent flow with common free surface. Therefore, in order to predict exit flow properties and investigate test results fitting, internal flow analysis has been performed. The results show agreement between numerical simulations and experiments, and air core has been formed correctly within injector. Two-phase and free surface simulations have been carried out using VOF method and turbulence has been modeled using k-model. The results have been discussed completely in the text.

The research carried out is a study of spray behavior and a better understanding of the Pressure-Swirl Duplex Injector to improve its future design. Therefore, the effect of a number of functional parameters is expressed as a function of pressure, Reynolds and Weber numbers. Water was the experiment fluid and all of the experiments performed at atmospheric standard condition. Spray area shooting were carried out based on fast shooting method. The results show that increasing Reynolds number would tend to change trickle mode regime to atomization then fully developed regime would be dominated as Reynolds numbers further increases. Moreover, Increasing Reynolds numbers would increase spraying angel of both paths followed by maintaining at constant values. Due to Injector's design pressure is estimated equaling to 10 bars because lowest beak-up angel was achieved around this condition. Furthermore, spatial distribution and spraying area measurements showed that the injector has the significant performance to creating a symmetric corn hollow spraying pattern. Additionally, it was realized that discharge coefficient is not only dependent on the geometry of the injector and would raise while Reynolds changes.

In this study, a compressive duplex injector was designed, fabricated, and its operational characteristics were investigated. Effects of pressure and viscosity on injector's operational characteristics (i. e., flow rate, discharge coefficient, break-up length, cone angel, spraying spatial distribution, and droplets' mean diameter) were presented as a function of injector's Reynolds and Weber numbers. Water and Mazut were employed as agent fluids due to their high viscosity differences. All experiments were carried out at atmospheric standard conditions. Picturing of spraying area was performed utilizing fast shooting, based on backlighting. The results showed increasing pressure would lead to raise in flow rate. Furthermore, raising Reynolds number leads to initial cone angel increase, then the spraying angel maintains constant as fully developed condition is dominated. The constant spraying angels are observed at Reynolds numbers above 265 and 7. 5×104 for Mazut and water, respectively. Moreover, break-up lengths are decreased at the Weber numbers lower than 50 and 170 for Mazut and water respectively, followed by maintain constant as the flow pattern is developed. The results showed that discharge coefficient depends on Reynolds number and fluid material, in addition to injector's geometry. The discharge coefficient is increased, as the Reynolds numbers raise to 200 and 5×104 for Mazut and water, respectively. The spatial distribution measurements showed significant performance of the injector for creating a hollow cone spray.

Because of vast applications of Liquid fuel engines in rockets and importance of their functional parameters such as trust, specific impulse and fuel consumption in engine performance, it is needed to be tested in different functional conditions before operation in actual missions. The analysis of test data used to improve the design, engine troubleshooting and to expand the production program for future rockets. Selecting the suitable injector(s) is the key parameter for improving combustion parameters. With respect to finding the effective ways to analyzing the engine hardware performance without neglecting from their main characteristics, one of the alternatives is doing the hot-fire tests by using a sub scaled engine instead of the full-scale engine. In this research, the design process and manufacturing details of a 300N trust (nominal) micro engine with single swirl Injector is presented. Initial firings using the actual fuel and oxide were not successful. Low fuel flow, low mixing area of the fuel and oxide, and contamination in the self-ignition fuel (TR-1) were considered to be the reasons. Overcoming to these problems resulted in successful firing of the subscale engine.

Optimized injectors spray and consequently their proper fluid distribution is one of the most important factors determining the thrust force and combustion stability. Reaching a stable combustion with a high specific impulse needs a proper fuel distribution and atomization. Asymmetric distribution of fuel spray droplets lead to asymmetric spray cone and incomplete combustion that cause the chamber broken.Regarding to the numerous advantages of swirl double-based injectors, 25 number of this injector type are manufactured to be mounted on a circular injector plate. To ensure that they have enough accuracy, macroscopic spray characteristic of all injectors are measured and examined in cold test lab and PDA lab. Having checked the quality of each injector, two types of injector plates are designed and manufactured precisely. Having manufactured a circular and a hexagonally arranged injector plate, their spray characteristics are examined. Results show that the circular injector plate has satisfactory spray characteristics like droplet distribution and desirable spray cone and could be ready for warm test.

The Gelled propellants have a promising future for aerospace applications because of possessing the advantages of both solid and liquid propellants. A gel propellant is a liquid propellant whose rheological properties have changed by the addition of gellant and other additives. The rheological properties of the propellant have a significant influence on the atomization process. In this paper, the rheological properties of the gel propellant are introduced. Then, the effect of gel propellant properties on the atomization in the swirl injector has been investigated. Subsequently, some important points for designing a swirl injector that can influence enhancing the atomization quality of the gelled propellant are presented. The results of the studies revealed that higher initial viscosity of the gelled propellant compared with the mother liquid propellant cause increase in the discharge coefficient, the size of droplet diameter, and the breakup length of the gel sheet while causing a decrease of spray cone angle in the swirl injector compared with liquid propellant and in the point of view of influenced by the size of droplet diameter on the gel propulsion system. Considering the shear thinning effect of the gel propellant and ability to atomization of gelled propellant by swirl injector, to improve the quality of the atomization of gel propellant, the design of the swirl injector should be such that the shear rate applied on the gel propellant should be increased to conquer the initial viscosity of the gel.

The monopropellant thrusters of the situation control system are a requirement for the development and application of satellites and space capsules in space, which are high-tech and expensive. In this paper, the design and simulation of a pressure-swirl injector with full-cone spray as a fuel injector of a monopropellant thruster are presented. For this injector, internal flow simulation was performed in order to predict its output flow characteristics including spray cone angle, output velocity distribution, mass flow rate, spray pattern, etc. For this purpose, VOF fluid volume method is used and the flow turbulence is simulated using the k-eps model. This type of injector is actually a combination of straight flow injector and swirl flow injector. Jet straight flow in the center of the injector and swirl flow along the injector wall are flowed. Both flow regimes are combined in the swirl chamber and the spray is formed as a full-cone. If the ratio of the outlets is selected correctly, the radial and environmental distribution of the liquid jet will be uniform. This injector is preferred to the capillary type (straight flow) and the swirl type. The pressure-swirl injector spray angle is larger than the capillary type, which improves the coverage of the catalyst bed, at the same time, spray angle is not as large as the swirl injector, which enlarges the radial dimensions of the decomposition chamber. Based on the results, it was ensured that the injector provides the desired mass flow rate (about 5. 8 gr/s) at a certain design pressure difference (3 bar) and determines a suitable spray pattern. It also provides the desired spray angle (about 35° ).

In this article, the fundamental calculations of swirl injectors were investigated and the design method for these kinds of injector, i.e. dual-base liquid-liquid injectors, was presented based on this theory and some experimental results. Then, some special conditions related to dual based liquid-liquid injectors were studied and the corresponding results were considered in the design manipulation. The behavior of injector in various performing conditions and mutual effects on twin spray envelopes in dual base injector were investigated, and the design procedure was presented based on the obtained results. Finally, the computer code for designing this type of injector was proposed. Using this code, some injectors were designed and tested. The results were satisfactory.