Initial Chamber Research Articles

Fuel Regression Characteristics of Axial-Injection End-Burning Hybrid Rocket Using Nitrous Oxide

This is an investigation of fuel regression characteristics in an axial-injection end-burning hybrid rocket using nitrous oxide. Experiments were conducted using 38 mm cylindrical fuel grains with an array of 0.8 mm ports made from curable resin. Previous studies of end-burning hybrid rockets used gaseous oxygen as oxidizer. Nitrous oxide may be more suitable than gaseous oxygen for use in space-based missions because of the weight savings associated with the oxidizer storage vessels, supply system, and motor mass. In this study, two types of nozzle closures were employed to increase the initial chamber pressure and promote the formation of stabilized combustion in multiport fuels. The results of 12 firing tests showed that the regression rates when using nitrous oxide as the oxidizer were as high as that from previous research (0.61–4.5 mm/s at 0.25–0.75 MPa) using gaseous oxygen as the oxidizer. These high regression rates were nearly five times higher than that of experiments using single-port fuels. It is clear from a visualization experiment that fuel flakes break off and travel downstream in solid form during firing, which could cause the fuel regression rate of multiport fuels to be higher than that of single-port fuels.

The ideal habitat for leaf-cutting ant queens to build their nests

Queens of Atta sexdens Forel (Hymenoptera: Formicidae) face biotic and abiotic environmental factors in the environment while establishing their nests. Biotic factors such as predation, microbial pathogens, successful symbiotic fungus regurgitation, excavation effort and abiotic factors such as radiant sunlight, temperature, density, and soil moisture exert selection pressures on ant queens. Biotic factors such as temperature and solar irradiation affect the survival of the initial colony differently, in different environments in the field. Queens of the leaf-cutting ant A. sexdens, were installed in sunny and shaded conditions to test this hypothesis. Two hundred A. sexdens queens were collected and individualized in two experimental areas (sunny and shaded), each in an experimental area (25 m2) in the center of a square (50 × 50 cm). Temperature, irradiance, nest depth, rainfall and queen mortality were evaluated. Atta sexdens colony development was better in the shaded environment, and the depth and volume of the initial chamber, fungus garden biomass and number of eggs, larvae, pupae and workers were greater. The queen masses were similar in both environments but mortality was higher in the sunny environment. The worse parameter values for A. sexdens nests in the sunny environment are due to the greater solar irradiance, increasing the variation range of the internal temperature of the initial chamber of the nest. On the other hand, the more stable internal temperature of this chamber in the shaded environment, is due to the lower incidence of solar irradiance, which is also more advantageous for queen survival and the formation and development of A. sexdens colonies. Shaded environments are a better micro habitat for nesting A. sexdens than sunny ones.

Verification of Seismic Cone Penetration Test Calibration Chamber Tests on a Sand

Abstract Calibration chambers are experimental apparatuses that allow the physical modeling of an in situ testing method, such as the cone penetration test (CPT), by performing laboratory experiments on soil samples with known stress, strain, and density characteristics. Over a series of development and improvements, more recent calibration chambers and laboratory cone penetrometers have become compact and less laborious than their predecessors. This includes the focus of this study where a miniature cone penetration testing (MCPT) calibration chamber previously designed and used at Western University is upgraded to measure shear wave velocity (VS) and enable anisotropic consolidation of soil specimens using a hydraulic piston. In addition to VS, MCPT can also measure cone tip resistance, sleeve friction, and excess pore water pressure developed behind the cone tip. A full test plan using the newly upgraded MCPT calibration chamber is presented in this study. These tests are performed on Fraser River sand at various relative densities and effective stresses. Results of this testing program are validated by comparison with a series of in situ seismic CPTs in the Fraser River delta, existing correlations between VS and cone tip resistance, and several other calibration chamber tests on different sands. Through these comparisons, the overall viability of the initial MCPT calibration chamber design, modifications made to the MCPT setup, and ultimately the results produced from this device are confirmed.

Prediction and verification for the models of temperature rising by medium bubbles in hydraulic system

In order to obtain the influence of the medium bubble contents on temperature rising characteristics of a hydraulic system, the working hydraulic system of a wheel loader was taken as the research object. By carrying out the comparison experiments of the hydraulic system with and without de-aeration devices on a 5-ton wheel loader, the air bubble contents and concerning temperatures were obtained. To identify the factors which have impact on temperature rising of the hydraulic system, the head chamber of boom cylinder is taken to analyze, and the temperature rising expression in a volume were deduced. By the utilization of the thermal hydraulic library, combining with mechanism and control libraries on AMESim simulation platform, the integrated simulation model of the whole system was established and verified, meanwhile, the simulation was carried out from aspects in different air contents and initial chamber temperatures. From the simulation, the prediction models of the air contents to temperature rising, and the pressures to temperature rising were predicted. Finally, the correctness of the prediction models are verified by experiment data and showing good results, which can be used to enrich and improve the calculation and evaluation methods of heat generation to any other hydraulic systems.

Experimental and numerical investigation of swirling H[formula omitted]O2 and polypropylene hybrid rocket motor with regenerative cooling

In this paper, the experimental and numerical investigations of both swirling hybrid rocket motors without and with the design of regenerative cooling (RC hereafter), using 90%-wt H2O2 and polypropylene (PP) as the liquid oxidizer and the solid fuel, respectively, were performed and compared. We implemented a new design of regenerative cooling using the oxidizer to transfer the heat generated from combustion. A series of ground horizontal hot-fire tests, which include the catalytic-bed only and the motor without/with RC were performed to measure the propulsion performance related parameters. The resulting C* efficiency of the RC design with catalytic-bed only remained in comparison with the one without RC. With a similar initial combustion chamber geometry, the RC implementation resulted in a better engine Isp efficiency from 96.3 to 98.6 with a lower O/F ratio from 6.49 to 5.94. In addition, the topologies of the burned fuel grain surface were optically measured by a 3D laser scanner. The resulting variation of regression rates between the upstream and downstream fuel for the chamber with the RC was smaller than case without the RC. Moreover, a simplified semi-empirical computational fluid dynamics (CFD) model based on the measured regression rates was constructed for investigating the physical phenomenon inside the hybrid rocket combustion chamber. The simulations show that a higher swirling number in the later portion of the port was found for the RC case. By concerning about the different O/F ratios and port size of the burned fuel, a series of simplified numerical CFD investigation with a fixed O/F and a fixed port size varying the regression rates from upstream to downstream fuel systematically with the same average region rate was performed to complement the semi-empirical CFD simulations. The results showed that there were two distinct regions including an upstream non-classical region dominated by the gas impingement of gas and a downstream classical region caused by the swirling effect of gases. In the non-classical region, the calculated distributions of the swirling numbers of the former are essentially the same for all the cases no matter what the magnitude of the regression rate is, while in the classical region higher swirling numbers are found for the case of more uniform distribution of regression rates. Heat generated near the upstream of the fuel grain was transferred more efficiently through the design of RC, which makes the resulting fuel regression more uniform than that without RC. The resulting swirling efficiency in the RC case was higher than that without RC. The HRM with RC hence had a better engine Isp efficiency with a lower O/F ratio.

Recycling Lithium from Waste Lithium Bromide to Produce Lithium Hydroxide.

Lithium resources face risks of shortages owing to the rapid development of the lithium industry. This makes the efficient production and recycling of lithium an issue that should be addressed immediately. Lithium bromide is widely used as a water-absorbent material, a humidity regulator, and an absorption refrigerant in the industry. However, there are few studies on the recovery of lithium from lithium bromide after disposal. In this paper, a bipolar membrane electrodialysis (BMED) process is proposed to convert waste lithium bromide into lithium hydroxide, with the generation of valuable hydrobromic acid as a by-product. The effects of the current density, the feed salt concentration, and the initial salt chamber volume on the performance of the BMED process were studied. When the reaction conditions were optimized, it was concluded that an initial salt chamber volume of 200 mL and a salt concentration of 0.3 mol/L provided the maximum benefit. A high current density leads to high energy consumption but with high current efficiency; therefore, the optimum current density was identified as 30 mA/cm2. Under the optimized conditions, the total economic cost of the BMED process was calculated as 2.243 USD·kg−1LiOH. As well as solving the problem of recycling waste lithium bromide, the process also represents a novel production methodology for lithium hydroxide. Given the prices of lithium hydroxide and hydrobromic acid, the process is both environmentally friendly and economical.

A two-dimensional neutron detector assembly at the China Mianyang Research Reactor

A two-dimensional neutron detector consisting of 96 3He position-sensitive proportional counters was assembled at the China Mianyang Research Reactor. With a count rate limit that is higher than that of the initial multi-wire proportional chamber detector at CMRR, it will be used for the small-angle neutron scattering spectrometer Suanni. The problems caused by low air pressure and γ radiation in the working environment are pretreated, and detector performance is evaluated and compared with that of the initial proportional chamber. Now the new detector is ready to be used for Suanni.

Quantifying Late Pennsylvanian Multivariate Morphological Change in the Fusulinid GenusTriticitesfrom the Central and Southwestern United States

ABSTRACTFusulinid Foraminifera are important for biostratigraphic correlation of strata in the Upper Paleozoic of the central and southwestern United States due to their high abundance and diversity in shallow marine carbonates. These correlations rely on consistent species-level identifications as well as geographically consistent morphological variation within species. However, many taxonomically important characters are described qualitatively, which can lead to conflicting identifications among taxonomists and cause biostratigraphic disagreements. Quantitative morphometric comparisons among species can increase the consistency of identifications among workers and capture temporal and geographic morphological gradients. Here, we used 14 linear measurements to describe the morphology of 18 biostratigraphically important species within the genus Triticites. Canonical variates analysis (CVA) showed that whereas specimens of a given species occupy similar areas of morphospace, species overlap considerably and, thus, these linear measurements poorly differentiate among species. However, species morphology covaried with geological age and multivariate analyses focused on age differences reveal an increase in the size of the initial chamber (proloculus) and a relative decrease in test expansion along the long axes over time. These morphological changes are consistent with an adaptation to shallow water conditions following the fall in relative sea-level across the Virgilian-Newwellian/Bursumian transition. Given the consistency of the morphological shift among North American basins, these morphological changes may be more useful for the recognition of the Virgilian-Newwellian/Bursumian transition than species-level biozones because they do not depend on consistent species identification.

Management Patterns and Outcomes for Intravitreal Injection-Related Endophthalmitis.

This work describes the clinical management and outcomes in cases of presumed infectious endophthalmitis following intravitreal injection at a tertiary academic medical center. A retrospective review took place of eyes that presented to the Duke Eye Center over a 9-year period and were diagnosed with intravitreal injection-related endophthalmitis. Clinical presentation, management, microbiologic yield, visual outcomes, and complications were abstracted from medical records. Of 23 eyes diagnosed with postinjection endophthalmitis, 52.2% underwent anterior chamber tap (33.3% of which first underwent dry needle vitreous tap), 47.8% underwent needle vitreous tap, 17.4% underwent neither, and none underwent pars plana vitrectomy (PPV) for initial management. Subsequent PPV was performed in 6 eyes (26.1%). Mean visual acuity (VA) improved by 50 Early Treatment Diabetic Retinopathy Study letters at 6 months. Eyes that underwent initial anterior chamber tap had worse presenting VA than those that did not (P = .01). Eyes undergoing subsequent PPV had worse VA at presentation (P = .02) and at 6 months (P < .001). Eyes presenting with VA of hand motion (20/8000) or worse were more likely to undergo subsequent PPV (P = .02). Eyes with intravitreal injection-related endophthalmitis presenting with VA of hand motion or worse were more likely to undergo subsequent PPV. Future studies with larger cohorts may reveal whether earlier vitrectomy should be considered in these patients.

Ignition process and propellant grains distribution of the two-module charge

The accumulation form of propellant grains has a great effect on the initial chamber pressure wave in the ignition and flame-spreading process of a modular charge. In this process, the grains distribution is determined by the dynamic characteristics of grains after the cartridge is broken. Therefore, a visualized ignition simulation experimental device was designed for the ignition test of the two-module charge with different initial loading positions. A high-speed camera system was used to observe the ignition and flame propagation, the rupture of combustible cartridge cases, and the moving process of the propellant grains. The experimental results show as follows. When the two-module charging position is far from the primer and the spacing between the two modules is increased, the time of flame propagation in the chamber is prolonged. And the cartridge cases are more completely burned and their rupture areas become larger. The propellant grains in the chamber are finally scattered in the axial 195–500 mm area starting from the end face of the primer side. The grains are mainly distributed in the steep-slope accumulation on the right side of the chamber. On the basis of the experiment, a three-dimensional unsteady gas-solid two-phase flow model for the modular charge was established. The dynamic process and distribution of the propellant grains was simulated. The calculation results are basically consistent with the test ones, which validate the rationality of the established model.

Effect of hydrogen enrichment of compressed natural gas on combustible limit and flame kernel evolution in a constant volume combustion chamber using laser ignition

Laser ignition of hydrogen-enriched compressed natural gas (HCNG) enables lean-burn combustion, a key technology for future emissions norms compliance for internal combustion (IC) engines. HCNG overcomes the limitations of low volumetric energy density and lowers the flame speed of CNG fueled spark ignition (SI) engine-powered vehicles. In this study, laser beam profile and beam quality (M2) of a Q-switched Nd: YAG laser at fundamental wavelength of 1064 nm, having 6–9 ns pulse duration, were characterized. During the Constant volume combustion chamber (CVCC) experiments, relative air-fuel ratio (λ) of different HCNG blends were varied to identify the lean-burn limits, and observe flame kernel evolution, pressure–time history, and detect the start of combustion (SoC). At 10 bar initial chamber filling pressure, lean flammability limit increased due to hydrogen (H2) enrichment of CNG. It was found to be λ = 1.6, 1.8, 1.9, 2.0, and 2.1 for CNG, 10HCNG (10% v/v hydrogen and balance CNG), 20HCNG, 30HCNG, and 40HCNG respectively. Flame kernel displacement (Early stages of flame initiation and its development in µs time-scale) was the highest for λ = 1.1 for all HCNG mixtures, irrespective of the test fuel composition. Knocking or two-stage combustion increased with lowering λ at 10 bar initial chamber filling pressure. SoC advanced and combustion duration (CD) decreased with increasing H2 enrichment of CNG. Increased H2 enrichment of CNG accelerated the flame kernel evolution and made it a predominantly a 3D combustion phenomenon (volumetric combustion). Lower λ and higher H2 enriched CNG mixtures were effective in reducing the CD.

Factors affecting the corneal endothelium after selective laser trabeculoplasty in primary open angle and angle closure glaucoma

PurposeTo study the factors affecting the corneal endothelium after selective laser trabeculoplasty (SLT) in primary open angle glaucoma (POAG) and primary angle closure glaucoma (PACG).MethodThis prospective interventional study included 56...

Experimental Investigation in the Autoignition Behaviour of Aviation Jet Fuel in a Rapid Compression Machine

Jet A-1 fuel’s autoignition behaviour was examined experimentally in a newly developed rapid compression machine (RCM) at the University of Sheffield. The experiment was conducted at a compressed temperature at compressed temperatures of 697 K ⩽ Tc ⩽ 796 K, compressed pressure of 6 and 10 bar, and under lean and stoichiometric conditions (φ = 0.75 and 1.0). The initial chamber wall temperature was varied from 115°C - 135°C. The effect of the compressed temperature, compressed pressure and equivalence ratio was seen to have influence on the ignition delay time (IDTs) of Jet A-1. In the experimental condition studied, Jet A-1 exhibited an Arrhenius behaviour that is increasing the compressed temperature, compressed pressure and equivalence ratio decreases monotonically with IDTs. Evidence of two-stage ignition delay and absence of Negative Temperature Coefficient (NTC) behaviour was observed within the condition studied.

Microbial Flow Within an Air-Phyllosphere-Soil Continuum.

The phyllosphere is populated by numerous microorganisms. Microbes from the wider environment, i.e., air and soil, are considered key contributors to phyllosphere microbial communities, but their contribution is unclear. This study seeks to address this knowledge gap by controlling the movement of microbes along the air-phyllosphere-soil continuum. Customized equipment with dual chambers was constructed that permitted airflow to enter the first chamber while the second chamber recruited filtered microbe-free air from the initial chamber. Allium schoenoprasum (chive) and Sonchus oleraceus (sow thistle) were cultivated in both chambers, and the microbial communities from air, phyllosphere, and soil samples were characterized. Shares of microbial OTUs in the equipment suggested a potential interconnection between the air, phyllosphere, and soil system. Fast expectation-maximization microbial source tracking (FEAST) suggested that soil was the major source of airborne microbial communities. In contrast, the contribution of airborne and soil microbes to phyllosphere microbial communities of either A. schoenoprasum or S. oleraceus was limited. Notably, the soilborne microbes were the only environmental sources to phyllosphere in the second chamber and could affect the composition of phyllosphere microbiota indirectly by air flow. The current study demonstrated the possible sources of phyllosphere microbes by controlling external airborne microbes in a designed microcosm system and provided a potential strategy for recruitment for phyllosphere recruitment.

ВЕРТИКАЛЬНАЯ ЗОНАЛЬНОСТЬ МЕДНО-МОЛИБДЕНОВОЙ ФОРМАЦИИ КУЗНЕЦКОГО АЛАТАУ (ХАКАСИЯ)

The previously identified zoning of the copper-molybdenum formation based on a comparison of geological features of the Sorskoye, Ipchulskoye and other deposits, is confirmed by a comparison of their deep structure and general model of the ore-magmatic system. As a result, it was possible to determine the distribution of ore matter and the degree of concentration of fluids and metals in the evolutionary chain in the first approximation: the initial granite melt-leucogranite residual chamber – ore-forming apophyse from the chamber. The maximum concentration in apophyse is 1000–2000 times higher than the initial content in an ordinary granite. This makes it possible to consider the fluidized apophyse melt as “ore magma” responsible for the ore formation.

Investigation of Chemical Kinetic Model for Hypergolic Propellant of Monomethylhydrazine and Nitrogen Tetroxide

Abstract Hypergolic bipropellant of monomethylhydrazine (MMH) and nitrogen tetroxide (NTO) is extensively used in spacecraft propulsion applications and rocket engines. But studies on the chemical kinetic mechanism of MMH/NTO are limited. So, in this study by integrating the submechanisms of MMH decomposition, NTO thermal decomposition, MMH/NTO and intermediates, and small hydrocarbons, the comprehensive chemical mechanism of MMH/NTO bipropellant is proposed. The present chemical mechanism consists of 72 species and 406 elementary reactions. In two respects of ignition delay times and combustion flame temperatures, the present model has been validated against the theoretical calculation results and also compared with other kinetic models in the literature. The validations show that the predicted ignition delay times by the present kinetic model are highly consistent with the theoretical data and well describe the pressure-dependent characteristic. For combustion flame temperature, the present model also exhibits better predictions to the theoretical calculation results, which are also the same as the predictions by the MMH-RFNA model. Furthermore, the influences of initial temperature, chamber pressure, and NTO/HHM mass ratio (O/F) on the ignition delay time and combustion flame temperature are investigated. The auto-ignition behavior of MMH/NTO propellant is sensitive to initial temperature and chamber pressure, and the combustion flame temperature is more sensitive to the O/F. This study provides a detail chemical kinetics model for further mechanism simplification and combustion numerical simulation.

Ignition delay measurements of four component model gasolines exploring the impacts of biofuels and aromatics

This study explores the impacts of combinations of biofuel (ethanol, isobutanol and 2-methyl furan) and aromatic (toluene) compounds in a four component fuel blend, at fixed research octane number (RON) on ignition delay measured in an advanced fuel ignition delay analyzer (AFIDA 2805). Ignition delay measurements were performed over a range of temperatures from 400 to 725 °C (673 to 998 K) and two chamber pressures of 10 and 20 bar. The four component mixtures are compared to primary reference fuels at RON values of 90 and 100. The ignition delay measurements show that as the aromatic and biofuel concentrations increased, two stage ignition behavior was suppressed, at both initial chamber pressures. But both RON 100 (isooctane) and RON 90 reference fuels showed two stage ignition behavior, as did fuel mixtures with low biofuel and aromatic content. RON 90 fuels showed stronger two stage ignition behavior than RON 100 fuels, as expected. Depending on the type of biofuel in the mixture, the ignition delay at low chamber temperatures could be far greater than for the reference fuels. In particular, for the RON 100 mixtures at either 10 or 20 bar initial chamber pressure, the ignition delay at 400 °C (673 K) for the high level blend of 2-methyl furan and toluene (30 vol% of each) exhibited an ignition delay that was 10 times longer than for neat isooctane. The results show the strong non-linear octane blending response of these three biofuel compounds, especially in concert with the kinetic antagonism that toluene is known to display in mixtures with isooctane. These results have implications for the formulation of biofuel mixtures for spark ignition and advanced compression ignition engines, where this non-linear octane blending response could be exploited to improve knock resistance, or modulate the autoignition process.

Initial and pulp chamber concentration of hydrogen peroxide using different bleaching products

Objective: This study’s aim was to quantify the hydrogen peroxide (HP) penetration into the pulp chamber of teeth submitted to different protocols of bleaching. Material and Methods: Ninety premolars were randomly divided into nine groups according to the bleaching agent protocol (n = 10): control (no bleaching), carbamide peroxide 10% [10% CP], carbamide peroxide 16% [16% CP], carbamide peroxide 22% [22% CP], hydrogen peroxide 4% [4% HP], hydrogen peroxide 6% [6% HP], hydrogen peroxide 7.5% [7.5% HP], hydrogen peroxide 10% [10% HP] and hydrogen peroxide 35% [35% HP]. The penetration of HP was measured via spectrophotometric analysis of the acetate buffer solution from the pulp chamber. The absorbance of the resulting solution was determined in a spectrophotometer and converted into equivalent concentration of HP (?g/ mL). To analyze the concentration of HP, the titration of bleaching agents with potassium permanganate was used. Data were subjected to ANOVA and Tukey’s test for pairwise comparison (? = 0.05). Results: Higher concentration of HP in the pulp chamber was found in the HP 35% group (p &lt; 0.0001). No significant difference between at-home protocols were observed (p = 0.64). Titration values showed that the concentration of the products was similar to that claimed by the manufacturer. Conclusion: It follows that the amount of HP that reaches the pulp chamber is not proportional to the concentration of whitening gels, but depends on the application time recommended by the manufacturers.KEYWORDSAt-home bleaching; Dental enamel permeability; Inoffice bleaching; Tooth bleaching.

Numerical modeling on thermoelastoplastic responses of Karamay oil sand reservoir upon steam circulation considering phase change of bitumen

Steam assisted gravity drainage technology has been widely applied to bitumen recovery in Karamay, northwest China. Steam circulation prior to production is designed to establish the thermal inter-well communication, aiming to create a desired initial steady steam chamber. Phenomenologically, the in situ immobile extremely viscous bitumen undergoes the change from solid to fluid state due to rheological fusion, and correspondingly the pay zone displays heated fusion and cold solid regions, within which thermal and mechanical properties differ considerably. To investigate these complex geomechanical responses, the heat transfer with phase change here was treated as a heat conduction with a moving boundary, and the modified Drucker-Prager model with cap plasticity was adopted to depict the mechanical behavior of oil sands. All models here used temperature-dependent constitutive parameters. This contribution coupled heat transfer, phase change and thermoelastoplastic deformation behaviors using a finite element code. A case study on SAGD well pairs using field operation parameters was conducted, and all reservoir information concerning temperature, phase change, deformation, stress and plastic zones were predicted. Temperature, deformation and stress along some typical paths at varying circulation periods were exhibited and discussed. The evolutions of phase change interfaces and plastic zones were provided. The changes of reservoir temperature as well as bitumen fluidity have significant impacts on the geomechanics, characterized by these interesting phenomena such as a maximum reservoir uplift occurring right above injection well, a high stress interference zone with shapes of arch or ellipse, and a plastic zone related to temperature distribution. This paper provides a coupled approach for the evaluation of reservoir thermoelastoplastic responses in steam circulation process, and it can also predict deformation change in permafrost and hydrate formation where transient heat transfer occurs incorporating phase change behavior.

Modeling of reservoir temperature upon preheating in SAGD wells considering phase change of bitumen

Steam circulation prior to production is usually employed to establish inter-well thermal communication and create an expected initial steam chamber in the process of bitumen recovery using steam assisted gravity drainage (SAGD). To realistically evaluate the efficiency of steam circulation, and to find the indicator for terminating the steam circulation and switching to SAGD production, modeling of the temperature propagation considering the bitumen-rich oil sand reservoir properties and oilfield operations is required. This study proposed two new modified methodologies, including an analytical model as well as a numerical model, in which the latent heat effect caused by the phase change of bitumen was involved for thermo-phase change coupled analyses. The modeling was conducted for a real SAGD steam circulation project in an oilfield located in Karamay, northwest of China, using oilfield operation parameters and thermo-dynamical properties obtained from laboratory tests. The models can predict the temperature propagation and bitumen phase change behavior in the domain encompassing dual wells. In general, the predicted results obtained from both analytical and numerical approaches agree well with those in published articles in terms of the cooling time derived from temperature falloff tests and inter-well midpoint temperature. The modeling draws major conclusions that the temperature drops rapidly with the distance to wellbore in the fusion zone, but decreases slowly in the solid zone. The heat flux on wellbore exhibits an exponential reduction in the beginning, but ultimately tends to be a constant. The moving speed of phase change interface decreases with injection time, and finally increases up to only a short distance. The inter-well midpoint temperature is heated to exceed the threshold temperature, and the whole inter-well area is ultimately occupied by the fusion zone. These findings not only can provide a criterion for evaluating the efficiency of steam circulation and an indicator for terminating the steam circulation and switching to production, but also the approaches proposed may be used to analyze these heat injection and phase change problems occurring in other types of oil and gas-rich reservoirs like the natural gas hydrate formation.