Mathematicval Modeling of Functional States in Humans under 7-Days Head-Down Bed Rest
- Paper number
IAC-04-G.1.02
- Author
Mrs. A.G. Chernikova, Institute for Biomedical Problems, Russia
- Year
2004
- Abstract
In the present paper, relations of the internal thrust and the specific impulse with the nozzle exit pressure have been established by means of one-dimensional fluid dynamics conservation models and chemical equilibrium hypothesis. With the new relations, difficulties in estimating the performance of scramjet engines based on experimental measurements can be removed. The existing theoretical models for predicting the internal thrust and specific impulse of scramjet engines are based on the nozzle exit Mach number and exit temperature, which are difficult to measure. Especially, the combustor performance is hardly to assess. However, the nozzle exit pressure can be measured conveniently. The relations have been deducted to resolve the problem on performance prediction of combustors as well as scramjet engines with experimental nozzle exit pressure measurements. In order to validate this method, the predicted thrust augmentation (ΔF) of an experimental scramjet combustor in CAAA (China Academy of Aerospace Aerodynamics) has been obtained from the present relations and has been compared with the experiment measurement. In the experiment, the flight altitude H and Mach number Mi are 20.5km and 6.0 separately with the designed inlet total pressure recovery coefficient σ=0.3, mass flux qa=1.408kg/s, combustor inlet Mach number Mc=2.7, fuel/air equivalence ratio Φ=0.95. ΔF is obtained based on the momentum difference between non-ignition and ignition status, and the pressure distribution on the wall is measured. A series of predicted results of ΔF vs the ratio of the nozzle exit pressure to the free flow pressure (pe/pi) at different combustion efficiencies (η) are given in Fig.1. It shows the predicted ΔF is equal to the experiment data with η near 0.9. The performance of another kind of low internal drag scramjet is evaluated with new relations based on the nozzle exit pressure with H=30km, Mi=6.0, combustor Mc=2.7, σ=0.5, qa=1.157kg/s. The results are given in Fig.2 and Fig.3. Fig.2 shows the relation of the internal thrust F with pe/pi under different η and fuel/air equivalence ratio Φ. As shown in Fig.2, F declines with pe and increases with η and Φ. If the combustion gas is expanded completely, that is, pe/pi=1, F will be 600N at Φ=0.6, and will be 1000N at Φ=1.0 with η=0.6. Fig.3 is the relation of the specific impulse Isp with pe/pi under different η and Φ. When pe/pi=1 and η=0.6, Isp will be 1340s at Φ=0.6, 1300s at Φ=0.8 and 1280s at Φ=1.0.
- Abstract document
- Manuscript document
IAC-04-G.1.02.pdf (🔒 authorized access only).
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