Chamber Valve Characteristic
Total Page:16
File Type:pdf, Size:1020Kb
Appendix A Chamber Valve Characteristic The position of a valve can be read by the MCC system from end switches; they indicate the full open or close status (Fig. A.1). In a valve switch test characteristic time delays can be identified. Open Close 250 256 371 248 Appears Appears Disappears Disappears Open Closed Open Closing Command Closed Fig. A.1 Time delay in Opening Command milliseconds for the manoeuvring of a valve Feed Back Back Feed (chamber valve hydrogen of a Back Feed Feed Back Back Feed Vulcain engine) (Photo: DLR) Back Feed W. Kitsche, Operation of a Cryogenic Rocket Engine, Springer Aerospace Technology, 95 DOI 10.1007/978-3-642-10565-4, C Springer-Verlag Berlin Heidelberg 2011 Appendix B Chamber Igniter Characteristic The chamber igniter is itself ignited by a pill of powder at its tip. A wire in a short- circuit conducting a current of 6 A for 50 ms ignites the pill. Thus the main powder charge is ignited and the internal pressure (Fig. B.1) of the pyrotechnical element increases. At a pressure of about 120 bar, three membranes which had sealed the element burst. Via three openings at an angle of 120◦ to each other the hot smoke is injected into the combustion chamber and ignites the fuel/oxidiser mixture. The time taken to reach 80% of the maximum pressure inside the igniter in this context is called the ignition delay (Fig. B.1). Figure B.2 is a series of photos showing the ignition of the fuel/oxidiser mixture and the flame evolution in the combustion chamber. The photos were taken with a high speed camera (2000 frames per second) via a mirror below the engine. 140 120 100 80 60 Pressure [bar] Pressure 40 20 0 0 100 200 300 400 500 600 700 Time [ms] Fig. B.1 Ignition delay of a chamber igniter (Photo: DLR) Fig. B.2 Ignition of a Vulcain-combustion chamber (Photo: DLR) 97 Appendix C Measurement and Correction of the Ovality of a Vulcain Nozzle The measurement and correction of the ovality of the Vulcain nozzle has been per- formed regularly since 1993. The protocol (Fig. C.1) documents such a procedure. The diameter was measured at different circumferential positions (before and after) and with a special clamping device the nozzle exit was reformed into a shape close to the circle. Fig. C.1 Inspection sheet (Inspection sheet: VOLVO) 99 Appendix D Compare of Flow Schemes Vulcain/Vulcain 2 Fig. D.1 Compare of Flow Schemes Vulcain/Vulcain 2 (Photo: SNECMA) 101 Appendix E Flow Scheme of the Ariane 5 Main Stage Fig. E.1 Flow scheme of the Ariane 5 main stage (Photo: SNECMA/EADS (formerly SEP/ Aerospatiale)) 103 Flow Scheme of Appendix F LAO + EVSCP (conditionnement GHe) FEFP (évacuation huile GAM) BMO (balayage TPO) LAO (alim.LOX) PGD (GHe commande) ECCH (conditionnement GHe) LAH (conditionnement GHe) PPH (Pressurisation RLH2) EVAE (alimentation LHe) TPCO (purge LOX) CTPCH (chasse ergols) BMH (balayage hydrogène) PPO (pressu. RLOX) EVSCP (purge SCP) ETAGE TPCH (purge LH2) LAH (alim.LH2) F F F CBPTM1 F B E P F FBSH P CBOR CBPTM2 FPOE FCE FPHE S P R FEC C H O 1 O V U L C A I N R E LEFP1 R 1 VCBPTM TP LH2 TP LOX DM CBCER VGC CBJTOS LTO Ce documentestlapropriétédeSNECMA.Ilnepeutêtrereproduitoucommuniquésanssonautorisationpréalabl LTH CBJPH CBJTO CBJTH Vulcain 2 LPRO CEVC VMRH CBGO1 GG L CBGH r F AG LEP u e P f f m u O SFAVGO u a i l SFAVGH h F é CBGO2 c h é P EVVGO R EVVGC O M CAVGO V V CAVGH EVVGH EVBO G G (BCO + BGO) VPO VPH CBCO2 O H FPHM EVVCO L L EVVP G G (VPO + VPH) O H LMRH EVVCH (VCH+VMRH) SFAVCO CBCO1 BEVC BEVB CBH LCO AC SFAVCH VCO CBCH CP LEO LCH2 LCH1 L F H VCH e etécrite LEH SYNOPTIQUE VULCAIN 2 Hydrogène liquide Gaz chaud + GHe Huile GAM Schéma fonctionnel fluides Diffusion provisoire Hydrogène gazeux GOX+GHe Volume conditionné pour information, en MOTEUR 105 présenté en phase propulsée Oxygène liquide Hélium gazeux Conditionnement attente d'une édition LEFP2 Mise à jour : 119901 du document officiel EPC A5E Gaz chaud Hélium liquide Matériels Fig. F.1 Flow scheme of Vulcain 2 (Photo: SNECMA/EADS (formerly SEP/Aerospatiale)) Appendix G Flow Scheme of Vinci (Photo: SNECMA) Vinci Flow scheme of Fig. G.1 107 Appendix H Mixtures of Oxygen and Nitrogen Close to Their Boiling Points The main component of an oxygen (O2) supply to a rocket engine is the run tank with liquid O2. If the tank is pressurised with nitrogen (N2) the condensation of N2 at the surface of the liquid O2 has to be considered. The equilibrium of both fluids close to their boiling point is shown in the phase diagram (Fig. H.1). For the calculation of the dewpoint and boilingpoint curve (H.1) and (H.2), [16] were used; the vapour pressure Pi (T ) was calculated according to [21]. − ( ) = P P2 T Boiling curve X1 (H.1) P1(T ) − P2(T ) − ( ) ( ) ( ) = P1 T P2 T 1 + P1 T Dew curve X1 (H.2) P1(T ) − P2(T ) P P1(T ) − P2(T ) The symbols are: T temperature of the mixture (here the temperature of the liquid O2), P pressure of the mixture (here the pressure in the vessel), P1(T ) vapour pressure of the first component (here N2), P2(T ) vapour pressure of the second component (here O2), X liquid mole fraction of N2, 1 X1 gaseous mole fraction of N2. Pressure = 1 bar Pressure = 2 bar Pressure = 6 bar Temperature of the Mixture [ K] Temperature of the Mixture[ K] Temperature of the Mixture [ K] 100 100 120 Mixture of Gas Mixture of Gas 95 Mixture of Gas 95 115 Gas/Liquid Mixture 110 90 K Line 90 K Linie 90 90 105 Gas/Liquid Mixture Gas/Liquid Mixture 85 85 100 95 80 80 Mixture of Liquids 90 Mixture of Liquids Mixture of Liquids 90 K Line 75 75 85 0 0,2 0,4 0,6 0,8 1 0 0,2 0,4 0,6 0,8 1 0 0,2 0,4 0,6 0,8 1 Nitrogen Fraction of the Mixture Nitrogen Fraction of the Mixture Nitrogen Fraction of the Mixture Fig. H.1 Phase diagram of O2/N2 mixtures at 1, 2 and 6 bar (Photo: DLR) 109 110 Appendix H Mixtures of Oxygen and Nitrogen Close to Their Boiling Points In fact the mixture is not homogeneous in time and space and is not at equi- librium. The pressure is defined by the pressurisation system; above the liquid it is constant, below the surface it increases with depth. The temperature around the surface is dominated by the temperature of the liquid oxygen, normally close to 90 K. If the tank pressure is held at 1 bar for a long time only very small fractions of N2 can be found in the liquid. When the pressurisation is started the condensation at the surface begins and the N2 fraction increases. We can assume that the condensed N2 remains mainly in the upper layers of the liquid (see below). After test, particularly when the pressure is reduced to 1 bar, the N2 as the more volatile component evaporates again. The typical evaporation rate of a vacuum insulated tank is 0.1% of the inner volume per day. For the oxygen tank (200 m3) on the facility P5 that means 200 L per day. Hence it takes 7 days to re-evaporate the N2. But in the normal test cycle the tank is refilled the day after the test. Due to this dilution the concentration of N2 decreases to a tenth part, which is a far more drastic decrease than that due to the evaporation. Nevertheless, for the engine test the N2 fraction in the oxygen means pollution. A sample taken during a normal test period had a fraction of 0.36% of N2 in O2. Diffusion of Liquid N2 in Liquid O2 In order to check whether a fast diffusion can distribute the N2 fraction all over the tank, we have to look for the solution of the diffusion equation (H.3)atthe applicable conditions. We also need the coefficient of N2 diffusion in liquid O2. The diffusion equation has the same mathematical structure as the heat conduction equation (H.5) for which we find the general solution (H.6)in[16] and transfer it to the diffusion equation. For the diffusion coefficient D no measured value could be found in the literature or on the internet; therefore the Stokes-Einstein-equation (H.4) was applied. ∂ c ∂2c Diffusion equation = D (H.3) ∂ t ∂ xi ∂ x j where c is the concentration, t the time, and xi the position vector (or, more cor- rectly, the coefficients of the components of the position vector). The Stokes-Einstein equation gives us K T − D = B = 97.6 × 10 9 Ns/m2 (H.4) 6 πμR0 −23 where K B = 1.38 × 10 as the Boltzmann number, T = 90 K as temperature, −6 2 μ = 6.5 × 10 Ns/m as the dynamic viscosity (of O2 at 90 K, 6 bar) and R0 = −11 10.4 × 10 m as particle radius (of N2). We obtain the general solution for the concentration c(x, t) in the one dimen- sional case: Appendix H Mixtures of Oxygen and Nitrogen Close to Their Boiling Points 111 ( , ) = + + − 2 ( ( ) + ( )) c x t c0 c1x exp Dant An cos an x Bn sin an x (H.5) n with the constants c0, c1, an, An, Bn.