High Mixture Ratio Research Articles

Study on bias residual control of high mixture ratio bi-propellant

Lift capacity is the key performance of the launch vehicle, and high chemical energy bi-propellants are commonly used for the modern large liquid rockets. The residual unburned propellant has a strong effect on the lift capacity and the lift efficiency, especially for the orbital stages. In this paper, the bias residual control of high mixture ratio propellant is studied, three models, including equal-probability depletion model (EPDM), equal-mass residual model(EMRM) and optimum residual model(ORM) are analyzed. Comparing with the traditional equal-probability depletion, the bias residual control of bi-propellants, especially for LOX and LH2, is benefit to the lift capacity. The effect between EMRM and ORM on the residual unburned propellant is negligible, and the EMRM is preferred in engineering.

Quantitative Clarification of Stable Ignition Region for HKP110 Green Hypergolic Bipropellant

As a candidate for a green hypergolic bipropellant, the combination of highly concentrated hydrogen peroxide and fuel with dissolved sodium borohydride has been widely studied. In this study, a drop test using such a green hypergolic bipropellant was conducted to investigate the stable ignition region in terms of the mixture ratio. As a result, stagnation phenomena of flame growth were observed in high mixture ratio conditions. In addition, impinging-jet tests using a windowed chamber were conducted with the green hypergolic bipropellant to observe the ignition phenomena inside the combustion chamber. As a result, unstable ignition phenomena were observed in oxidizer-lead injection cases. Besides the unstable ignition, hard starts occurred several times during the test series. Data analysis demonstrated that controlling the transient mixture ratio in the early phase of injection is essential for preventing unstable ignition and hard starts. The quantitative threshold of mixture ratio for stable ignition was clarified based on the test results.

Research on Ignition Property of Reduced-Toxicity Hypergolic Bipropellant

Ignition property of reduced-toxicity hypergolic bipropellant was investigated under the condition that various parameters such as concentration, mixture ratio, propellant temperature were changed. 3-Methylaminopropylamine doped with sodium borohydride was used as a fuel, and propellant grade hydrogen peroxide was used as an oxidizer. As a result, it was found that this bipropellant has two ignition mode. Under the condition that concentrations of hydrogen peroxide and sodium borohydride are higher than certain values, ignition delay times are less than 4msec and do not depend on mixture ratio. On the other hand, ignition delay times become larger as mixture ratio increases under the condition of lower concentration. Even in the former ignition mode, it was observed that the growth of flame almost stopped for a while just after ignition under the high mixture ratio conditions. It was also found that temperature of hydrogen peroxide has some effect on ignition delay time, whereas that of fuel has little effect. Considering from these experimental results, ignition model formed by three phases was proposed. In this model, the cooling effect by unreacted hydrogen peroxide in condensed phase is considered to have potent effect on ignition delay time and post ignition behavior. This feature is caused by high optimum mixture ratio and exothermic self-decomposition property of hydrogen peroxide.

Development of repair method using polymer for ballasted tracks with a high-mixture ratio of fine particles

Development of repair method using polymer for ballasted tracks with a high-mixture ratio of fine particles

Potential of Methane Production by Thermophilic Anaerobic Co-Digestion of Pulp and Paper Sludge with Pig Manure

This study investigated the potential of methane production of thermophilic anaerobic co-digestion of diluted pulp and paper sludge (DPPS) with diluted pig manure (DPM). The mixture ratios, that is, pulp and paper sludge (PPS) and pig manure (PM) were mixed with tap water to create slurry with a volatile solid (VS) content of 4% as substrate, respectively. The co-digestion was carried out in a 2 liter reactor tank which was stirred semi-continuously with a five phase organic loading rate (OLR) consequently the contents were being drawn-and-fed daily. This experimental design was operated by a triplicate with steady state operations during a thermophilic condition of 50 � C and a constant solid retention time (SRT) of 10 days. The results demonstrated that the co-digestion of DPPS and DPM mixture ratio (50:50) resulted in higher methane production, specific methane yields (SMY), and soluble chemical oxygen demand (SCOD) removal efficiency. The highest methane content of biogas, SMY, volatile solid (VS) degradation rate and SCOD removal efficiency of 5654 ± 421%, 7158 ± 875 ml-CH4/g-VSadded ,5 574 ± 027% and 8354 ± 632%, respectively, were achieved with process stability. However, it added too high mixture ratio of PM to reduce methane yield and SCOD removal efficiency. This study showed that there was a good potential of PPS and PM on thermophilic anaerobic co-digestion for methane production.

Approaches to Low Fuel Regression Rate in Hybrid Rocket Engines

Hybrid rocket engines are promising propulsion systems which present appealing features such as safety, low cost, and environmental friendliness. On the other hand, certain issues hamper the development hoped for. The present paper discusses approaches addressing improvements to one of the most important among these issues: low fuel regression rate. To highlight the consequence of such an issue and to better understand the concepts proposed, fundamentals are summarized. Two approaches are presented (multiport grain and high mixture ratio) which aim at reducing negative effects without enhancing regression rate. Furthermore, fuel material changes and nonconventional geometries of grain and/or injector are presented as methods to increase fuel regression rate. Although most of these approaches are still at the laboratory or concept scale, many of them are promising.

Circumferential Film Cooling Effectiveness in a LOX/H2 Subscale Combustion Chamber

In order to study wall temperature distribution, film cooling effectiveness and wall heat flux reduction due to film cooling in the circumferential direction, experimental investigations have been carried out, using gaseous hydrogen (GH_2) as a film coolant with tangential slot injection in close proximity to the injector face plate. A Vulcain 2 like test case has been performed, using a combustion chamber pressure up to 11.5 MPa at a high mixture ratio ROF = 6 with ambient temperatures of hydrogen. The experimental investigations have shown significant variations of wall temperatures due to injector design as well as a distribution of film cooling effectiveness which persists far downstream from the film coolant injection slots. Circumferential variations of wall temperature and film cooling effectiveness are much more pronounced at higher combustion chamber pressures.

Crystal orientations of InSb films grown on a Si(111) substrate by inserting AlSb buffer layer

AbstractThe heteroepitaxial growth of InSb film via AlSb buffer layer on a Si(111) substrate was performed in an ultra high vacuum. The grown InSb films were characterized by X‐ray diffraction and atomic force microscopy. XRD patterns (ϕ‐scan) of the samples showed different epitaxial relationship between InSb/Si and InSb/AlSb/Si. It is found that surface condition has a significant influence on the growth of InSb films and the surface of InSb films became rough due to the high mixture ratio of domains. The two‐step growth procedure was also tried to further improve the crystal quality of the InSb films. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of surface coating ratio of surface modified particles on the contact potential difference between a powder bed and a metal

Abstract Experimental and theoretical studies have been conducted on the effect of the surface coating ratio of surface modified SiO2 particles on the measurement of the contact potential difference between a powder bed and a metal. The applied potential, which is a characteristic property of an electrostatic charge, and surface coating ratio have the same tendency in relation to the mixture ratio of fine to core particles. The surface coating ratio peaks at a certain mixture ratio. On scanning electron microscope photographs, agglomerated particles are observed on core particle surfaces at a high mixture ratio. The surface coating ratio starts to decrease after peaking at a certain mixture ratio, because the fine particles re-entrain. The experimental data agree well with the calculated results that take into account the sticking probability of the fine particles to the core particle surfaces. A theoretical equation is derived for the relationship between the surface coating ratio and the mixture ratio. The relationship between the angle of repose of powder and the mixture ratio indicates the same tendency as the relationship between the applied voltage and the mixture ratio.

Dual mixture ratio H2/O2 engine for single stage to orbit application

This paper discusses propulsion requirements for rocket-powered single stage to orbit (SSTO) vehicles and defines a dual mixture ratio Hi/Oi staged combustion engine concept with characteristics matched to those requirements. The objective of this study was to configure an engine within the limits of current technology that when combined with a vehicle based on the material advances of the National Aerospace Plane program could provide an effective SSTO system. This engine uses high mixture ratio to provide high bulk density propellant usage and high thrust for the booster mode and transitions to low mixture ratio for high specific impulse during the upper stage mode. The internal operating characteristics of this engine are within the limits of current technology. Preliminary SSTO system studies indicate significant vehicle weight reductions relative to the Space Shuttle main engine (SSME) powered systems. This engine could be available before the end of this century.

COMBINED EXTERNAL AND INTERNAL COOLING

various freeze area ratios. These data are shown in Fig. 2. The estimated freeze area ratios from Fig. 1 also are shown for the rate coefficient 6 X 10 (cm/mole)/sec at several large exit area ratios. The effects of increasing the rate constant to 10, the upper limit on rate coefficient, also are shown. The salient results are as follows: 1) In the region of the throat the rate of change of impulse with freeze area ratio is large and the lower mixture ratio theoretical performance is greater than the higher mixture ratio. 2) When kinetic considerations are superimposed on this graph, the performance at the higher mixture ratio is always greater than the lower, regardless of small perturbations in geometry or rate constant. 3) The performance loss is higher for larger exit area ratios and lower mixture ratios. Results of Fig. 2 are summarized in Table 2. Other losses, such as combustion, drag, divergence, etc., can be added to the recombination losses by known methods to predict delivered 7sp. Thus, the kinetic scheme shown here provides a powerful tool for predicting the performance of space engines using the presently most attractive storable propellant combinations.