Use of a “green” propellant in low-thrust control jet engine systems

The aim of this work is to analyze the state of the art in the development and use of pollution-free (“green”) propellants in low-thrust jet engines used as actuators of spacecraft stabilization and flight control systems and to adapt computational methods to the determination of “green”-propellant engine thrust characteristics. The monopropellant that is now widely used in the above-mentioned engines is hydrazine, whose decomposition produces a jet thrust due to the gaseous reaction products flowing out of a supersonic nozzle. Because of the high toxicity of hydrazine and the complex technology of hydrazine filling, it is important to search for its less toxic substitutes that would compare well with it in energy and mass characteristics. A promising line of this substitution is the use of ion liquids classed with “green” ones. The main components of these propellants are a water solution of an ion liquid and a fuel component. The exothermic thermocatalytic decomposition of a “green” propellant is combined with the combustion of its fuel component and increases the combustion chamber pressure due to the formation of gaseous products, which produces an engine thrust. It is well known that a “green” propellant itself and the products of its decomposition and combustion are far less toxic that hydrazine and the products of its decomposition, The paper presents data on foreign developments of “green” propellants of different types, which are under test in ground (bench) conditions and on a number of spacecraft. The key parameter that governs the efficiency of the jet propulsion system thrust characteristics is the performance of the decomposition and combustion products, which depends on their temperature and chemical composition. The use of equilibrium high-temperature process calculation methods for this purpose is too idealized and calls for experimental verification. Besides, a substantial contribution to the end effect is made by the design features of propellant feed and flow through a fine-dispersed catalyst layer aimed at maximizing the monopropellant-catalyst contact area. As a result, in addition to the computational determination of the thrust characteristics of a propulsion system under design, its experimental tryout is mandatory. The literature gives information on the performance data of “green”-propellant propulsion systems for single engines. However, in spacecraft control engine systems their number may amount to 8–16; in addition, they operate in different regimes and may differ in thrust/throttling characteristics, which leads to unstable propellant feed to operating engines. To predict these processes, the paper suggests a mathematical model developed at the Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine and adapted to “green”-propellant engine systems. The model serves to calculate the operation of low-thrust jet engine systems and describes the propellant flow in propellant feed lines, propellant valves, and combustion chambers. To implement the model, use was made of the results of experimental studies on a prototype “green”-propellant engine developed at Yuzhnoye State Design Office. The analysis of the experimental results made it possible to refine the performance parameters of the monopropellant employed and obtain computational data that may be used in analyzing the operation of a single engine or an engine system on this propellant type in ground and flight conditions

Research on characteristics of dual-frequency coupling electroaerodynamic thruster

Breaking through the corona discharge current limit and improving the ionization and acceleration process are beneficial to improve the performance of the electroaerodynamic thruster. In this paper, a dual-frequency source of DC and NSP (nanosecond pulse) are applied to generate ionic wind. Electrical, optical and thrust characteristics are compared for the electroaerodynamic thruster with and without the NSPD (nanosecond pulse discharge). The experimental results indicate that the thrust characteristics are enhanced under the effect of dual-frequency sources. Moreover, the inception DC voltage to generate ionic wind is much lower.

Investigation on Thrust Characteristics of a Downstream Offshore Floating Wind Turbine under Yawed Inflow Conditions

In the natural marine environment, offshore floating wind turbines (OFWTs) inevitably experience yawed inflow conditions, which will make their aerodynamics more complicated than uniform inflow conditions and difficult to understand. In the present study, the thrust characteristics of a wake-influenced OFWT under dynamic, static, and coupled yawed inflow conditions are investigated thoroughly. Analytical characterizations of yawed inflow and upstream wake are integrated into the blade element momentum (BEM) method to achieve the investigation. Based on this method, simulations by the FAST code have been conducted, and the results are analyzed. It is shown that the three inflow conditions have considerable influences on the thrust coefficient of the wind rotor or the normal force at the blade section, especially in the wake case where the downstream OFWT is located at a specific offset from the central line of a single upstream wake. In order to validate the analyses of simulation results, experimental tests by a set of dedicated apparatus are conducted. The comparison results are good, proving the reliability of simulation results. This work can provide some theoretical contributions to the aerodynamic design and control of OFWTs.

Thrust characteristics of compact high-voltage pulsed plasma thruster utilizing liquid propellant

In this work, we present the results on thrust performance of 0.5 kg sub-joule pulsed plasma thruster prototype based on a high-voltage transformer with magnetic storage capable of work at frequency of 400 Hz. The discharge unit is made of ferroelectric ceramics with an option for utilizing liquid propellant. In case of vacuum oil as a propellant, we obtained values of thrust of ~ 80 nN·s per discharge and 33 μN·s for 400 pulses in 1 second.

Scaling of on-board characteristics of waterjet propulsion based on bench thrust testing data and loop test results

The on-board “speed-resistance-power” curves are profiled by a fitted jet thrust deduction factor relation, where the raw data are obtained from both bench thrust testing data and loop test results. Firstly, the thrust characteristics of a waterjet were tested by a thrust testing bench, while the pump performance such as capacity, head and shaft power of the waterjet was measured on a loop test rig. The useful fitted jet thrust deduction factor relation involves three related variables, that is to say, thrust coefficient, torque coefficient, and advance coefficient. Then, the best efficiency propulsion points are indicated by a collapsing technology and the subsequent results that the best efficiency propulsion points are actually existed. Cavitation margins are also noted by the two groups of data obtained by the loop data and the bench data, respectively. The discrepancy of the two margins shows the measuring error of the loop test means. In addition, the non-consistency features of the curves in the cavitation zone indicate the complex cavitation instabilities in the waterjet propulsion. At last, the bench tested thrust results are supplemented and therefore a useful map is completed.

AERODYNAMIC THRUST CHARACTERISTICS AND PERFORMANCE VALUATIONS FOR AN AEROSPIKE NOZZLE- REVIEW

Aerospike nozzles are now-a-days one of the most emerging topics for research and development work leading for the futuristic goals of an aerospace industries and organizations. They are indulging in a class of elevation balancing nozzle engines. These nozzle engines are basically constructed for single-stage-to-orbit (SSTO) as well as foremost engine for space vehicles. These nozzles are about 75% shorter than the standard nozzle for similar expansion ratios. Aerodynamic thrust variation and performances play a key role in estimating forces along with the injected flow and their characteristics. This review paper deals with the aerodynamics characterization, its properties at different conditions in addition with the performance analysis of the aerospike nozzle.