The Experts below are selected from a list of 36 Experts worldwide ranked by ideXlab platform
Lauck F. - One of the best experts on this subject based on the ideXlab platform.
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Experimentelle Untersuchung von Detonations- und Flammensperren für einen vorgemischten, grünen Raketentreibstoff aus Lachgas (N2O) und Ethen (C2H4) Experimental investigation of detonation and Flame Arrestors used for a premixed, green propellan
2016Co-Authors: Lauck F.Abstract:Hydrazine is one of the major propellants for attitude and orbital control systems in spacecrafts. The handling of hydrazine is difficult due to its high toxicity. There are political efforts in Europe to restrict the use of hydrazine (REACH-Regulation). For this reason, research for environmentally friendly, alternative propellants is conducted. One of those so called “Green Propellants” is a mixture consisting of nitrous oxide (N2O) and ethylene (C2H4), which is under experimental investigation at the Institute for Space Propulsion of the German Aerospace Center (DLR) in Lampoldshausen. In future application, the propellant is intended to be stored premixed and liquefied in a tank combining the advantages of mono and bipropellants. A specific risk of such premixed fuel-oxidizer-mixtures is flashback into the propellant feeding lines. In this case, the Flame could flash back into the tank. Such an event would be fatal for the propulsion system of a spacecraft and its whole mission. A particular effort must be made to prevent the occurrence of flashback. This thesis looks at the theoretical models of Flame propagation and flashback. Based on this examination and previous experimental test results possible Flame Arrestors are chosen for further investigations. The Flame Arrestors consist of porous sintered metal. To investigate their properties, an ignition test bench was built. The test setup consists of two chambers: a cylindrical ignition chamber and a secondary chamber. The cambers are connected and the Flame arrestor can be placed in between them. Ignition tests were conducted at a constant oxidizer to fuel ratio and variation of the initial pressure. A selection of the tests was recorded by high-speed camera. The gained data is analyzed, illustrated and discussed. It is shown, that there are porous materials with small pore sizes, for example the GKN’s SIKA-B 30 or SIKA-R 200 from a length longer 10.5 mm and with a diameter of 12.45 mm, can prevent flashback to an initial pressure of 4 bar. Furthermore, experiments were conducted on the quenching ability of orifices with a diameter of 0.3 and 0.5 mm. The critical Peclet numbers at our initial conditions are in the order of 30. High-speed recordings of the ignition show, that the Flame in the ignition chamber propagates laminar and the maximum expansion speed of the Flame tip is in the order of 60 to 70 m/s. The maximum expansion speed is combined by the laminar burning rate of the Flame and a velocity induced by the expansion of the combustion products
Dieter Lietze - One of the best experts on this subject based on the ideXlab platform.
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Crimped metal ribbon Flame Arrestors for the protection of gas measurement systems
Journal of Loss Prevention in The Process Industries, 2001Co-Authors: Dieter LietzeAbstract:Abstract This paper summarises the results of extensive research to determine the limit of safety against Flame transmission for Flame Arrestors of relatively small size fitted with arrestor elements made of crimped metal ribbon. Depending on the reactivity of the fuel gas/air mixture and the tube geometry the running up to detonation and hence the stressing of a Flame arrestor by a detonation is possible in longer tubes with relatively small diameters. Only with reactive gas phases of explosion group I this stressing case for a Flame arrestor can be excluded. With detonative gas phases the stressing of the Flame arrestor decisively depends on the place of installation with respect to the point of transition from deflagration to detonation in the system considered. Five different stressing cases with a probably very different limiting pressure of safety against Flame transmission must be distinguished. The results of the investigations will help to evaluate the results from testing of Flame Arrestors carried out according to the requirements in national and international standards or regulations.
Allan Sagle - One of the best experts on this subject based on the ideXlab platform.
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Failure Analysis and Prevention of Fires and Explosions with Plastic Gasoline Containers
Journal of Failure Analysis and Prevention, 2011Co-Authors: Glen Stevick, Joseph Zicherman, David Rondinone, Allan SagleAbstract:Explosions and fire incidents involving portable plastic gasoline containers manufactured for consumer use are known to occur frequently and are verified in databases, engineering literature, legal briefs, and newspapers. This project studied such incidents and presents findings from a comprehensive test program documenting conditions under which such incidents occur. Factors controlling resultant vapor headspace compositions and headspace ignitions and/or explosion occurrences include the following: mass of gasoline in relation to a particular container size, ambient temperature, and “age” of stored gasoline samples. Experimental results also demonstrated the effectiveness of Flame Arrestors to eliminate risk of explosion.
Zhaowu Shen - One of the best experts on this subject based on the ideXlab platform.
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The quenching of propane deflagrations by crimped ribbon Flame Arrestors
Journal of Loss Prevention in The Process Industries, 2016Co-Authors: Luqing Wang, Zhaowu ShenAbstract:Abstract Experimental studies of deflagration Flame quenching by crimped ribbon Flame Arrestors were performed in a circular ducting with propane-air flammable mixture. The corresponding Flameproof velocities were determined systemically. The results showed that the channel length, the expansion ratio and the aperture size must be taken into consideration to predict the performance of the crimped ribbon Flame Arrestors. To explore the relationship between Flameproof velocity and arrestor structure, numerical simulations were carried out. The simulated results showed that with the reduction of the hydraulic diameter of the aperture size, the Flameproof velocity is increased, which implies the basic angle must be considered when crimped ribbon Flame Arrestors are used to quench deflagration Flame. In addition, the influence of the expansion ratio is of great significance on the efficiency of Flame Arrestors. The Flameproof velocity can be reduced to be a value related to the expansion ratio. Two empirical formulas were derived to exhibit the relation between the Flameproof velocity and the characteristics of the Flame arrestor, which can be used to predict the performance of crimped ribbon Arrestors.
Dian Hua Peng - One of the best experts on this subject based on the ideXlab platform.
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Flameless Venting Devices for Dust Explosions and Experimental Confirmation of their Efficiency
Advanced Materials Research, 2013Co-Authors: Dian Hua PengAbstract:In a closed pulverized coal preparation system, a special device must be installed to vent Flames and pressure during unexpected dust explosions. A vent Flame arrestor is a key element in this device, which helps prevent a dangerous second explosion by venting Flames. Traditional vent Flame Arrestors are designed with mounting metal fiber or rock fiber on both the sides and the top of the arrestor to cool dust Flames and arrest burning dust during an explosion. This type of arrestor is widely used, but their application is still problematic, even for St1 dust at low reduced pressure (Pred). To solve these problems, we designed two types of Flameless venting devices. The first is intended for St1 dust explosion venting at Pred 0.07 MPa, and was modified from an original device by adopting a labyrinth-like structure in the interior space to successively reduce the strength of the dust Flame. The second is intended for St1 dust explosion venting at 0.07 < Pred 0.18 MPa, and was modified from the first type by adding a special suppressant in the interior space to make the dust Flames cooler than the ignition point of the dust. Our experiments confirmed that our designs yield improved efficiency of Flameless venting devices, leading to safer vent Flame Arrestors.