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21.
Optimization of the design of recuperative heat exchangers in the exhaust nozzle of an aero engine 总被引:1,自引:0,他引:1
Kyros Yakinthos Dimitris Missirlis Achilles Palikaras Paul Storm Burkhard Simon Apostolos Goulas 《Applied Mathematical Modelling》2007
Today the needs for safer, cleaner and more affordable civil aero engines are found to be of great importance. Five years ago, the EU initiated an action for the design and the construction of efficient and environmentally friendly aero engines (EEFAE). One of the major European gas turbine industries, MTU, has presented a new technology for an advanced aero engine design, which uses an alternative thermodynamic cycle. The basis of this cycle is the adoption of a recuperation part with the use of a system of heat exchangers, installed in the exhaust nozzle of the aircraft engine. Thermal energy in the turbine exhaust is used in the recuperator to pre-heat the compressor outlet air before combustion. The benefits of this technique are focused on reduced pollutants and decreased fuel consumption. In this work, the procedure of the optimization of this installation, by means of the imposed pressure drop downstream the aircraft engine and the balanced mass inflow to the heat exchangers is presented. The optimization is based on experimental measurements in laboratory conditions and preliminary 2D CFD modeling for the flow inside the exhaust duct and through the heat exchangers. It is shown that with a careful approach, a better arrangement of the heat exchangers can be achieved in order to have a minimum pressure drop in the exhaust nozzle which can positively affect the engine’s performance. 相似文献
22.
The magnetic structure of the tetragonal ErCo2Si2 compound is determined by neutron diffraction on powder sample at 4.2 K. The magnetic ordering is connected with a symmetry lowering, magnetic space group P2s (Sh72)k = 000. The structure is collinear antiferromagnetic with the erbium magnetic moments making an angle of 56.2° with the c axis. The magnetic moment value for erbium is 6.75μB. 相似文献
23.
J.K. Yakinthos Ch. Routsi Penelope Schobinger-Papamantellos 《Journal of Physics and Chemistry of Solids》1984,45(6):689-693
Neutron diffraction studies of polycrystalline PrCo2Si2 and TbCo2Si2 compounds were carried out at 4.2 and 293 K. Both samples have collinear antiferromagnetic order below TN(31(1) and 46(1) K for Pr and Tb compound respectively), with their magnetic moments parallel to the c axis. The ordered magnetic moment values of Pr and Tb at 4.2 K (3.19 and 9.12 μB respectively), are close to the saturation value of the free ions. The corresponding magnetic space group Pl4/mnc (Sh410128) is body-anticentered ( refering to Pl cell). 相似文献
24.
A comparison is made of the electric field gradient at the Dy nucleus in DyCo3 estimated by a point charge calculation and that measured by Mössbauer spectroscopy. 相似文献
25.
J.K. Yakinthos 《Journal of Physics and Chemistry of Solids》1978,39(5):485-488
Neutron diffraction measurements, made on powder samples, show that Ho4Co3 and Er4Co3 intermetallic compounds are ferrimagnetic at 4.2 K. The magnetic moments of the 2 holmium sites are 8.7 and 2.1 μB and those of the erbium sites are equal to 8.7 and 8.1μB. The cobal+ magnetic moment is 0.2μB for both compounds. The easy magnetization direction lies on the hexagonal plane for Ho4Co3 while for Er4Co3 there are 2 anisotropy directions. Exchange interactions between rare-earth ions of both sites are very weak compared with the total crystal field splitting of the ground state multiplet J. The crystal field parameters are calculated and the magnitude and direction of the rare-earth magnetic moments in each site is determined. 相似文献
26.
The nucleide 73Kr has been identified by on-line mass separation as a precursor of β-delayed proton emission. The proton branch is (6.8 ±1.2) × 10−3 proton/decay. The protons populate the ground state and also the first excited 2+ state at 866 keV in 72Se with a relative intensity of (35±9) %. The value of QEC−Bp, where Bp is the proton separation energy for the nucleus 73Br, is found to be 4.85 ±0.30 MeV based on the fraction of proton events preceded by positron decay. 相似文献
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The magnetic susceptibility of the ternary compounds, RPd2Si2 (where R=Gd, Tb, Dy, Ho and Er) has been measured. GdPd2Si2 order antiferromagnetically at 13 and 20 K respectively; the rest of the compounds do not show clear ordering down to 4.2 K. Palladium carries no moment in these compounds. The De Gennes formula is not obeyed indicating that the exchange interaction between the 4f moments via conduction electrons is not isotropic 相似文献
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J.K. Yakinthos P.F. Ikonomou T. Anagnostopoulos 《Journal of magnetism and magnetic materials》1978,8(4):308-312
Magnetic properties of nine RE2Au compounds have been studied in fields of up to 19 kOe in the temperature range 4.2K–300K. It has been found that all compounds are paramagnetic at room temperature except Gd2Au. The compounds with Pr, Nd, Ho, Er and Tm exhibit Curie-Weiss behaviour with paramagnetic moments in close agreement with those expected for the free RE3+ ion. The moment of gold was found to be zero. The compounds with Pr, Nd, Tb, Dy, Er and Tm are antiferromagnetic at low temperatures. It appears that Ho2Au is ferromagnetically ordered below 4.5 K. No evidence for magnetic ordering was found for Y2Au. The compound with Tb exhibits metamagnetic behaviour. 相似文献