A theoretical investigation of thermodynamic performance for a ramjet based on a magnesium—water reaction

Abstract

A preliminary study on the operating performance of a certain kind of water ramjet engine was implemented theoretically. With regard to this proposed powerplant operating in an available water environment, inspiration drawn from a supercavitation phenomenon coupled with a hydroreactive characteristic of several metals was the inducement for its attractive development. In terms of the requirement to provide the highest possible performance, a multiple water-injection mechanism was employed; i.e. the introduction of sufficient ambient water was suggested in order to maintain a successful combustion, while in the meantime not being too large to avoid a potential condensation phenomenon at the nozzle exit. Then against a ramjet carrying a metal fuel grain with a 50 per cent magnesium mass fraction, a performance analysis proceeded on the basis of a proposed thermodynamic calculation theory. The upper limit of the primary water-fuel ratio was predicted as 2.4 when considering the conditional temperature of the main magnesium-water reaction. Peak values of both specific impulse and thrust exist on the order of 4695.86 N s/kg and 2.57 kN respectively, while the water-fuel ratio approached 4.2. Furthermore, rules governing the characteristic velocity along with the water-fuel ratio were also examined. Then, altering physical conditions such as metal fuel formation and chamber pressure, a conclusion was drawn that a higher performance was related to a relatively higher chamber pressure and a higher magnesium mass fraction as long as normal working conditions were guaranteed.

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“…Yang, et al [16] theoretically analyzed the thermal and dynamic properties of Mg based water ramjet. Han, et al [17] studied the influence of the primary water inlet angle on the specific impulse performance of the secondary water inlet engine, established the two-phase flow reaction model of the engine afterburner, and carried out numerical simulation and ground direct connection experiment.…”

Theoretical Performance Evaluation of a Marine Solid Propellant Water-Breathing Ramjet Propulsor

“…Relatively to aluminum, magnesium has a lower energy density, but the magnesium-water reaction is easier to initiate. Therefore, some researchers suggested using magnesium [4,5,7,8] or using an aluminum-magnesium mixture [6]. The high-temperature stoichiometric reactions of boron, aluminum, and magnesium with water are presented here:…”

“…Therefore, propulsion principles utilizing the surrounding water as a working fluid as well as a chemical reactant (usually oxidizer), have been considered [2][3][4][5][6][7][8]. One of the interesting concepts for propelling high-speed underwater vehicles is the solid propellant water-breathing ramjet [4][5][6][7][8]. It is a powerful propulsion means, independent of atmospheric air, hence, it can operate fully and deeply underwater.…”

Examining Metal Additives in a Marine Hybrid-Propellant, Water-Breathing Ramjet

“…Aluminum has a higher heat of reaction with water, whereas magnesium is more reactive with water, which, in practice, may lead to a better reaction efficiency, compensating for its lower heat of reaction. Works performed in the field have mainly focused on different aspects of solidpropellant, water-breathing ramjets, such as evaluating optimal operating conditions and maximal theoretical performance [7][8][9][10][11], combustion properties of different propellants and fuels tailored for a water-breathing operation [1][2][3][4][5], and static firing tests [12,13] as well as other aspects [14]. Previous research conducted by these authors [15,16] suggested considering the use of a ducted, hybrid, ram-rocket-based water-breathing ramjet.…”