The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform
Edgar Y. Choueiri - One of the best experts on this subject based on the ideXlab platform.
-
A Critical History of Electric Propulsion: The First 50 Years (1906-1956)
Journal of Propulsion and Power, 2004Co-Authors: Edgar Y. ChoueiriAbstract:Nomenclature A = beam cross-sectional area a = vehicle acceleration i ≡ p/V = current per unit vehicle mass j = current density M v = vehicle mass ˙ m = propellant mass flow rate P = input electric power p ≡ P/M v = input electric power per unit vehicle mass T = thrust u ex = rocket Exhaust Velocity V = voltage η = thrust efficiency
-
Scaling laws for electromagnetic pulsed plasma thrusters
Plasma Sources Science and Technology, 2001Co-Authors: John Ziemer, Edgar Y. ChoueiriAbstract:The scaling laws of pulsed plasma thrusters operating in the predominantly electromagnetic acceleration mode (EM-PPT) are investigated theoretically and experimentally using gas-fed pulsed plasma thrusters. A fundamental characteristic Velocity that depends on the inductance per unit length and the square root of the capacitance to the initial inductance ratio is identified. An analytical model of the discharge current predicts scaling laws in which the propulsive efficiency is proportional to the EM-PPT performance scaling number, defined here as the ratio of the Exhaust Velocity to the EM-PPT characteristic Velocity. The importance of the effective plasma resistance in improving the propulsive performance is shown. To test the validity of the predicted scaling relations, the performance of two gas-fed pulsed plasma thruster designs (one with coaxial electrodes and the other with parallel-plate electrodes), was measured under 70 different operating conditions using an argon plasma. The measurements demonstrate that the impulse bit scales linearly with the integral of the square of the discharge current as expected for an electromagnetic accelerator. The measured performance scaling is shown to be in good agreement with the theoretically predicted scaling. Normalizing the Exhaust Velocity and the impulse-to-energy ratio by the EM-PPT characteristic Velocity collapses almost all the measured data onto single curves that uphold the general validity of these scaling laws. [12pt]This paper is dedicated to the memory of Dr Daniel Birx
-
A Characteristic Velocity for Gas-Fed PPT Performance Scaling
2000Co-Authors: John Ziemer, Edgar Y. ChoueiriAbstract:The performance scaling of gas-fed pulsed plasma thrusters (GFPPTs) is investigated theoretically and experimentally. A characteristic Velocity for GFPPTs that depends on the inductance-per-unit-length and the square root of the capacitance to initial inductance ratio has been identifled. An analytical model of the discharge current predicts the e‐ciency to be proportional to the GFPPT performance scaling number, deflned here as the ratio of the Exhaust Velocity to the GFPPT characteristic Velocity. To test the validity of the predicted scaling relations, the performance of two rapid-pulse-rate GFPPT designs, PT5 (coaxial electrodes) and PT9 (parallel-plate electrodes), has been measured over 70 difierent operating conditions with argon propellant. The measurements demonstrate that the impulse bit scales linearly with the integral of the discharge current squared as expected for an electromagnetic accelerator. The measured performance scaling in both electrode geometries is shown to be in good agreement with theoretical predictions using the performance scaling number. Normalizing the Exhaust Velocity and the impulse-to-energy ratio by the GFPPT characteristic Velocity collapses almost all the measured data onto single curves that represent the scaling relations for these GFPPTs.
-
Scaling Laws for Pulsed Electric Propulsion with Application to the Pluto Express Mission ∗ Scaling Laws for Pulsed Electric Propulsion Systems
International Electric Propulsion Conference, 1995Co-Authors: John Ziemert, Edgar Y. Choueiri, Robert G. JahnAbstract:A set of universal laws for the scaling of pulsed elec- tric propulsion systems is presented. The Langmuir characteristic Velocity and another characteristic ve- locity defined here as the pulsed electric propulsion (PEP) characteristic Velocity are the two governing parameters in these scaling laws. The Langmuir and PEP characteristic velocities describe the relation of the power generator mass and the energy storage sys- tem mass to the propellant mass required to perform a given mission. An optimal Exhaust Velocity that maximizes the useful mass fraction of the spacecraft can be found using these two parameters. This tech- nique especially applies to low power, small space- craft where the mass of the energy storage system could make up a significant fraction of the total mass. An Ablative Pulsed Plasma Thruster (APPT) is used as an example low power pulsed electric propulsion system applied to the Pluto Express Mission. A 100% increase in the scientific payload mass of a recent probe design is demonstrated by replacing the chem- ical propulsion system with an optimized APPT sys- tem using only well proven off-the-shelf technologies.
Takeshi Tachibana - One of the best experts on this subject based on the ideXlab platform.
-
Plasma-assisted combustion of N2O/Ethanol propellant for Space Propulsion
46th AIAA ASME SAE ASEE Joint Propulsion Conference & Exhibit, 2010Co-Authors: Akira Kakami, Taku Egawa, Natsuki Yamamoto, Takeshi TachibanaAbstract:This paper describes a Nitrous Oxide (N2O)/Ethanol thruster using arc discharge assisted combustion. Ethanol and N2O, which are neither toxic nor reactive, can be stored as liquid owing to their relatively low freezing point. Arc discharge is used for the assistance of N2O/Ethanol combustion, as an alternative to Iridium based particulate catalyst, which has been applied to conventional chemical thrusters. The experiment showed that the combustion was successfully started and sustained with assistance of 1-kW class arc discharge. Thrust chamber pressure measurement yielded 88-% characteristic Exhaust Velocity (C* efficiency), which indicates the degree of combustion completion, at a specific power of 2.8 MJ/kg.
-
plasma assisted combustion of n2o ethanol propellant for space propulsion
46th AIAA ASME SAE ASEE Joint Propulsion Conference & Exhibit, 2010Co-Authors: Akira Kakami, Taku Egawa, Natsuki Yamamoto, Takeshi TachibanaAbstract:This paper describes a Nitrous Oxide (N2O)/Ethanol thruster using arc discharge assisted combustion. Ethanol and N2O, which are neither toxic nor reactive, can be stored as liquid owing to their relatively low freezing point. Arc discharge is used for the assistance of N2O/Ethanol combustion, as an alternative to Iridium based particulate catalyst, which has been applied to conventional chemical thrusters. The experiment showed that the combustion was successfully started and sustained with assistance of 1-kW class arc discharge. Thrust chamber pressure measurement yielded 88-% characteristic Exhaust Velocity (C* efficiency), which indicates the degree of combustion completion, at a specific power of 2.8 MJ/kg.
Jiaming Zhao - One of the best experts on this subject based on the ideXlab platform.
-
Experimental Investigation on the Discharge of Pollutants from Tunnel Fires
Sustainability, 2020Co-Authors: Lihua Zhai, Zhisheng Xu, Zhongxing Nong, Guanhong He, Jiaming ZhaoAbstract:Many pollutants are generated during tunnel fires, such as smoke and toxic gases. How to control the smoke generated by tunnel fires was focused on in this paper. A series of experiments were carried out in a 1:10 model tunnel with dimensions of 6.0 m × 1.0 m × 0.7 m. The purpose was to investigate the smoke layer thickness and the heat Exhaust coefficient of the tunnel mechanical smoke Exhaust mode under longitudinal wind. Ethanol was employed as fuel, and the heat release rates were set to be 10.6 kW, 18.6 kW, and 31.9 kW. The Exhaust Velocity was 0.32–3.16 m/s, and the longitudinal Velocity was 0–0.47 m/s. The temperature profile in the tunnel was measured, and the buoyant flow stratification regime was visualized by a laser sheet. The results showed that the longitudinal ventilation leads to a secondary stratification of the smoke flow. In the ceiling extract tunnel under longitudinal ventilation, considering the research results of the smoke layer height and the heat Exhaust coefficient, a better scheme for fire-producing pollutants was that an Exhaust Velocity of 1.26–2.21 m/s (corresponding to the actual Velocity of 4.0–7.0 m/s) should be used. The longitudinal Velocity should be 0.16–0.32 m/s (corresponding to the actual Velocity of 0.5–1.0 m/s).
-
Analysis on the influence of the smoke block board on the entrainment phenomena near a mechanical Exhaust vent
Case Studies in Thermal Engineering, 2018Co-Authors: Zhisheng Xu, Lu He, Hongguang Chen, Jiaming ZhaoAbstract:Abstract In this study, the Fire Dynamics Simulator (FDS) numerical simulation method is adopted to analyze the influence of various smoke block board sizes, heat release rates (HRR) and Exhaust velocities on the smoke entrainment near a mechanical Exhaust vent. The results indicate that the smoke extraction performance of the board-coupled shaft is influenced by the coordination of the smoke block board layout, the heat release rate and Exhaust Velocity. Besides, the reasonable size of the board can effectively reduce the air entrainment and achieve the best smoke Exhaust efficiency. When the board size is smaller than the Exhaust vent size, there will be an inefficient Exhaust smoke. When the board size is larger than the Exhaust vent size, the Exhaust smoke efficiency increases rapidly with the increase in the board size. In addition, the Exhaust efficiency is insensitive to the HRR under the same board. However, the Exhaust Velocity exerts a significant effect on the layered stability and smoke extraction performance near the Exhaust vent.
Akira Kakami - One of the best experts on this subject based on the ideXlab platform.
-
Plasma-assisted combustion of N2O/Ethanol propellant for Space Propulsion
46th AIAA ASME SAE ASEE Joint Propulsion Conference & Exhibit, 2010Co-Authors: Akira Kakami, Taku Egawa, Natsuki Yamamoto, Takeshi TachibanaAbstract:This paper describes a Nitrous Oxide (N2O)/Ethanol thruster using arc discharge assisted combustion. Ethanol and N2O, which are neither toxic nor reactive, can be stored as liquid owing to their relatively low freezing point. Arc discharge is used for the assistance of N2O/Ethanol combustion, as an alternative to Iridium based particulate catalyst, which has been applied to conventional chemical thrusters. The experiment showed that the combustion was successfully started and sustained with assistance of 1-kW class arc discharge. Thrust chamber pressure measurement yielded 88-% characteristic Exhaust Velocity (C* efficiency), which indicates the degree of combustion completion, at a specific power of 2.8 MJ/kg.
-
plasma assisted combustion of n2o ethanol propellant for space propulsion
46th AIAA ASME SAE ASEE Joint Propulsion Conference & Exhibit, 2010Co-Authors: Akira Kakami, Taku Egawa, Natsuki Yamamoto, Takeshi TachibanaAbstract:This paper describes a Nitrous Oxide (N2O)/Ethanol thruster using arc discharge assisted combustion. Ethanol and N2O, which are neither toxic nor reactive, can be stored as liquid owing to their relatively low freezing point. Arc discharge is used for the assistance of N2O/Ethanol combustion, as an alternative to Iridium based particulate catalyst, which has been applied to conventional chemical thrusters. The experiment showed that the combustion was successfully started and sustained with assistance of 1-kW class arc discharge. Thrust chamber pressure measurement yielded 88-% characteristic Exhaust Velocity (C* efficiency), which indicates the degree of combustion completion, at a specific power of 2.8 MJ/kg.
Zhisheng Xu - One of the best experts on this subject based on the ideXlab platform.
-
Experimental Investigation on the Discharge of Pollutants from Tunnel Fires
Sustainability, 2020Co-Authors: Lihua Zhai, Zhisheng Xu, Zhongxing Nong, Guanhong He, Jiaming ZhaoAbstract:Many pollutants are generated during tunnel fires, such as smoke and toxic gases. How to control the smoke generated by tunnel fires was focused on in this paper. A series of experiments were carried out in a 1:10 model tunnel with dimensions of 6.0 m × 1.0 m × 0.7 m. The purpose was to investigate the smoke layer thickness and the heat Exhaust coefficient of the tunnel mechanical smoke Exhaust mode under longitudinal wind. Ethanol was employed as fuel, and the heat release rates were set to be 10.6 kW, 18.6 kW, and 31.9 kW. The Exhaust Velocity was 0.32–3.16 m/s, and the longitudinal Velocity was 0–0.47 m/s. The temperature profile in the tunnel was measured, and the buoyant flow stratification regime was visualized by a laser sheet. The results showed that the longitudinal ventilation leads to a secondary stratification of the smoke flow. In the ceiling extract tunnel under longitudinal ventilation, considering the research results of the smoke layer height and the heat Exhaust coefficient, a better scheme for fire-producing pollutants was that an Exhaust Velocity of 1.26–2.21 m/s (corresponding to the actual Velocity of 4.0–7.0 m/s) should be used. The longitudinal Velocity should be 0.16–0.32 m/s (corresponding to the actual Velocity of 0.5–1.0 m/s).
-
Analysis of entrainment phenomenon near mechanical Exhaust vent and a prediction model for smoke temperature in tunnel fire
Tunnelling and Underground Space Technology, 2018Co-Authors: Lu He, Zhisheng Xu, Hongguang Chen, Yixiao Wang, Yang ZhouAbstract:Abstract To investigate the entrainment phenomenon near a mechanical Exhaust vent in the tunnel fire, the computational fluid dynamics method employing the software Fire Dynamics Simulator (FDS) is utilized to analyse the effects of heat release rate (HRR) and Exhaust Velocity on the entrainment near the vent. The simulation results indicate that the total amount of fresh air entrained in the tunnel increases continuously with increasing HRR and Exhaust Velocity. However, when the smoke temperature is low, the mass flow rate of fresh air Exhausted through the shaft is insensitive to the HRR, while is affected more by the Exhaust rate. In addition, a simplified prediction model for downstream smoke temperature is developed to account for the entrainment effect on smoke temperature variation. The predicted values accord well with the simulated ones. Results in this work can provide a reference to the optimization design and management of smoke control system in tunnels.
-
Analysis on the influence of the smoke block board on the entrainment phenomena near a mechanical Exhaust vent
Case Studies in Thermal Engineering, 2018Co-Authors: Zhisheng Xu, Lu He, Hongguang Chen, Jiaming ZhaoAbstract:Abstract In this study, the Fire Dynamics Simulator (FDS) numerical simulation method is adopted to analyze the influence of various smoke block board sizes, heat release rates (HRR) and Exhaust velocities on the smoke entrainment near a mechanical Exhaust vent. The results indicate that the smoke extraction performance of the board-coupled shaft is influenced by the coordination of the smoke block board layout, the heat release rate and Exhaust Velocity. Besides, the reasonable size of the board can effectively reduce the air entrainment and achieve the best smoke Exhaust efficiency. When the board size is smaller than the Exhaust vent size, there will be an inefficient Exhaust smoke. When the board size is larger than the Exhaust vent size, the Exhaust smoke efficiency increases rapidly with the increase in the board size. In addition, the Exhaust efficiency is insensitive to the HRR under the same board. However, the Exhaust Velocity exerts a significant effect on the layered stability and smoke extraction performance near the Exhaust vent.