Advantage of ethanol fuel for gas generator cycle air turbo ramjet engine

Performance analyses of Gas Generator cycle Air Turbo Ramjet (GG-ATR) engine are conducted to investigate the feasibility of ethanol fuel, as comparing Liquefied Hydrogen (LH2), Liquefied Natural Gas (LNG), and n-C12H26. Liquefied Oxygen (LOX) is considered as an oxidizer. Gas generator combustion temperature and compressor pressure ratio are selected as the analytical parameters, which are varied from 900 to 1700 K and from 2.0 to 4.0, respectively. In general, specific impulses of light molecule weight fuels, such as LH2 and LNG, are higher than those of large molecule weight fuel. For storable fuel, Isp of ethanol is larger than that of n-C12H26 when gas generator temperature is less than 1300 K, although specific heat release of ethanol is only two thirds of n-C12H26 heat release. The main chemical species of n-C12H26 gas generator (GG) combustion gas are CH4 and CO. On the other hand, ethanol GG combustion gas is mainly composed of H2 and CO, resulting in smaller molecular weight than n-C12H26. These characteristics contribute to larger Isp of ethanol than n-C12H26 and indicate the feasibility of ethanol for GG-ATR engine fuel.本アーカイブに掲載したPDFは校正前の原稿である

Experimental Measurements of Starting Loads and Model Behaviors in the Indraft Supersonic Wind Tunnel

Measurements of starting load in the indraft supersonic wind tunnel of Muroran Institute of Technology were conducted for Mach 2, 3 and 4 conditions with the AGARD-B model. The high-speed photographs covering the behaviors of the wind tunnel model from the start to end of the operation were taken. Those photographs make clear that the oscillations of the model coincide with the measured starting load oscillation and starting loads were caused by two shock waves. The first shock wave is the reflection shock, generated at the nozzle throat by expansion wave reflection. The second wave is comprised asymmetric oblique shock waves (AOS) coming from upstream. AOS can generate asymmetric conical shock (ACS) around the nose cone of the model, which would have directly caused the starting loads on the wind tunnel model. Based on these observations, propose a conical shock theory, as an alternative starting load prediction theory instead of the normal shock theory

Overspeeding characteristics of turbomachinery for gas generator cycle air turbo ramjet engine

The main interest in the current study focuses on the possibility of overspeeding for the gas-generator cycle air turbo ramjet (GG-ATR) engine. The authors developed the air turbo ramjet engine and investigated its compressor performance. Based on those data, the authors developed the analytical code for the air turbo ramjet engine, which calculates the performances of turbomachinery, gas-generator, and ram combustor. The previous study described that the rotor overspeeding would not occur in the air turbo rocket engine. However, the current results show that degraded ram combustion can decrease the compressor pressure ratio and the compressor power. This reduced compressor power can cause overspeeding for the air turbo ramjet engine. The experimental results of compressor power and turbine inlet pressure support those analytical results

Numerical and experimental investigations on Mach 2 and 4 pseudo-shock waves in a square duct

The structures and characteristics of λ-shaped and X-shaped pseudo-shocks in a square duct are investigated through numerical simulations and experiments at Mach 2 and Mach 4, respectively. The experiments were carried out in a pressure-vacuum supersonic wind tunnel with a test cross section of 80 x 80 mm(2). Numerical simulations were carried out using the Harten-Yee second-order TVD scheme and the Baldwin-Lomax turbulence model. The Reynolds numbers for the Mach 2 and 4 cases were Re-∞ = 2.53 x 10(7) and Re-∞ = 2.36 x 10(7), respectively, and the flow confinement was δ(∞)/h = 0.35 for both cases. The computational results for the Mach 2 pseudo-shock wave are in good agreement with the experimental results. Based on this agreement, the flow quantities, which are very difficult to obtain experimentally, were analyzed by numerical simulation. Although several differences were found between the computational results and experiments in the case of Mach 4 due to asymmetric characteristics in experiment which could not be reproduced in numerical simulation, the computational results are valuable for understanding this complex asymmetric phenomenon

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