Two-phase Injection Research Articles

Acoustic response of an injection system to high-frequency transverse acoustic fields

The acoustic coupling between the injection system and the acoustic fluctuations in liquid rocket engine combustion chambers is an important issue in the understanding of the thermo-acoustic instability phenomenon. This paper presents the results of a wide-ranging parametric investigation of the acoustic response of a two-phase injection system submitted to a forced high-amplitude transverse acoustic field. Two domes, one for the gas and one for the liquid, were expressly designed to feed three identical coaxial injectors. The internal mode shapes of the domes were characterized by measuring pressure signals at different locations in the domes. Experimental mode shapes showed good agreement with those predicted by numerical simulations. Acoustic pressure amplitudes up to 23% of those induced in the main cavity can be found in both the gas and liquid domes. The response efficiency in a dome depends on the position of the injectors’ exit in the acoustic field.

Theoretical investigation of vapor mass fraction measurement methods for two-phase injection compression

The economized vapor injection (EVI) method is used to decrease the discharge temperature of scroll compressors and to improve the cycle performance of vapor compression refrigeration systems by directly injecting refrigerant vapor into the compression chamber. In previous studies, the optimal cycle performance for an air conditioning system using EVI was detected during two-phase injection. However, the exact vapor mass fraction could not be measured directly. For further investigations on two-phase injection systems, accurate vapor mass fraction (VMF) measurements need to be conducted. This paper compares different options for the VMF measurement using pure refrigerants or refrigerant mixtures. It focuses on the achievable accuracy of the VMF measurement, based on the propagation of uncertainty.

Stabilisation of oil-contaminated soils using microbially induced calcite crystals by bacterial flocs

Of late, oil spills have occurred frequently in many places around the world, causing serious geoenvironmental problems. The oil products adversely affect the safety of civil engineering infrastructures by altering the engineering properties of soils. This study proposes and describes a new approach for the stabilisation of oil-contaminated soils using a modified approach for the microbially induced calcite precipitation (MICP) technique. In contrast to one common method of MICP treatment that has been applied in the literature through the two-phase injection method, the new approach proposed herein involves premixing ureolytic bacterial flocs with oil-contaminated soils for the purpose of bacteria introduction and fixation. Repeated flushes of cementation solution (i.e. calcium chloride and urea) are then followed, leading to the precipitation of low-soluble calcite (calcium carbonate) crystals. This new MICP exploration was successful in producing an unconfined compressive strength of up to 1200 kPa, thereby providing a high potential for stabilising oil-contaminated soils in regions of oil spills.

Performance of a Two-Phase Injection Heat Pump with the Variation of Injection Quality and Pressure

Heat pumps are becoming more commonly and widely used due to their advantages in efficiency and versatile applications in both cooling and heating. However, the reliability of its compressor is being compromised due to high discharge temperatures caused by harsh operating conditions. Among the numerous studies conducted in improving the discharge temperature and performance of the heat pump, two-phase injection is receiving great interest. In this study, the performance of the two-phase injection heat pump was measured with a variation of operating parameters. The experiment results were used to study the performance change according to the operating parameter such as injection quality and pressure. It was found that the performance of the heat pump using the two-phase injection was better in terms of COP by up to 5.8% compared to that using the vapor injection. Furthermore, the two-phase injection was effective in reducing the discharge temperature to improve the compressor reliability. Two types of optimum injection qualities were suggested through this study: discharge temperature optimum injection quality (TIQ), and performance optimum injection quality (PIQ). It was found that in most conditions PIQ was sufficient in satisfying the compressor reliability, but in harsh operating conditions, where the compression ratio was high, TIQ was required in order to maintain the compressor reliability.

An experimental and theoretical study on an injection-assisted air-conditioner using R32 in the refrigeration cycle

An air-conditioner (AC) that uses refrigerant R32 assisted with one-phase vapor injection shows high energy efficiency and low discharge temperature in the heat-pump cycle, but the performance is not satisfactory in the refrigeration cycle. In this study, an improved injection cycle consisting of one-phase vapor injection mode and two-phase injection mode is proposed and integrated into an AC using R32, which is now referred to as an advanced injection-assisted air-conditioner (IAC). Through an experimental and theoretical study, an optimal injection duration of 8s is attained for maximizing the refrigeration potential of the IAC. Furthermore, in an entire day–night cycle, both the cooling capacity and energy efficiency ratio (EER) of the IAC within the two-phase injection cycle are enhanced by 25% and 32%, respectively, compared with those of a noninjection-assisted AC. Moreover, two-phase injection offers the highest exergetic efficiency, approximately 50% or more in the refrigeration cycle, exhibiting remarkable thermodynamic performance of the IAC. In addition, compared to the conventional AC using R410A, the IAC using R32 within a two-phase injection cycle demonstrates reasonable payback performance and substantial reduction in carbon dioxide and sulfur dioxide emissions in the refrigeration cycle.

Influence of Key Environmental Conditions on Microbially Induced Cementation for Soil Stabilization

AbstractMicrobially induced calcite precipitation (MICP) is a sustainable biological ground improvement technique that is capable of altering and improving soil mechanical and geotechnical engineering properties. In this paper, laboratory column studies were used to examine the effects of some key environmental parameters on ureolytic MICP mediated soils, including the impact of urease concentrations, temperature, rainwater flushing, oil contamination, and freeze–thaw cycling. The results indicate that an effective crystal precipitation pattern can be obtained at low urease activity and ambient temperature, resulting in high improvement in soil unconfined compressive strength (UCS). The microstructural images of such crystals showed agglomerated large clusters filling the gaps between the soil grains, leading to effective crystals formation. The rainwater flushing was detrimental to the biocementation process. The results also indicate that traditional MICP treatment by the two-phase injection method did ...

Evaluation of two-phase suction, liquid injection and two-phase injection for decreasing the discharge temperature of the R32 scroll compressor

R32 has been considered as an important alternative in the phase-out of hydrochlorofluorocarbons (HCFCs) due to its advantages such as relatively low global warming potential compared to R410A, favorable thermal properties. However, the increased discharge temperature of the R32 compressor, compared with R410A, is the main barrier affecting the wide and quick adoption. In this work, three promising methods to decrease the discharge temperature of R32 scroll compressor, namely, two-phase suction, liquid injection and two-phase injection, have been investigated. By considering the variations of motor efficiency and leakage rate, an improved distributed parameter model of the scroll compressor is rebuilt based on a previously developed one (Wang et al., 2008). By that model, the effectiveness of these three methods in decreasing discharge temperature and their influence on thermodynamic performance are researched. It is concluded that all the three methods show excellent potential in decreasing the discharge temperature of R32 scroll compressor. Besides, two-phase injection outperforms the other two methods in cooling capacity and COP by 11.8% and 4.8%, respectively.

Study of Gas Core Behavior of Passive Cyclonic Two-Phase Separator for Microgravity Applications

Separating gas-liquid two-phase flow is of practical importance for many space engineering systems. While droplet and bubble removal is a naturally occurring phenomenon in most terrestrial situations, the absence of buoyancy in a microgravity environment often results in situations where two disparate phases have no distinct inclination to separate from one another. Passive cyclonic separators can perform this task without moving parts and the reliability concerns of active separators. In such separation devices, separation efficiency is strongly influenced by the gas core behavior. Based on experimental and numerical investigations, the behavior of the gas core with two-phase injection is studied. A control-volume model is developed to capture the relevant physics of the flow in the separator. It is shown that the injection nozzle design, swirl number, and volumetric gas quality all have a major influence on the core size. The present investigation covers a range of volumetric quality from 0 to 0.75, and a range of swirl number from 17 to 28. Both homogeneous and non-homogeneous nozzles are used. The implications of the results are discussed in detail.

Gas–liquid two-phase flows in rectangular polymer micro-channels

This study addresses gas–liquid two-phase flows in polymer (PMMA) micro-channels with non-molecularly smooth and poorly wetting walls (typical contact angle of 65°) unlike previous studies conducted on highly wetting molecularly smooth materials (e.g., glass/silicon). Four fundamentally different topological flow regimes (Capillary Bubbly, Segmented, Annular, Dry) were identified along with two transitory ones (Segmented/Annular, Annular/Dry) and regime boundaries were identified from the two different test chips. The regime transition boundaries were influenced by the geometry of the two-phase injection, the aspect ratio of the test micro-channels, and potentially the chip material as evidenced from comparisons with the results of previous studies. Three principal Segmented flow sub-regimes (1, 2, and 3) were identified on the basis of quantified topological characteristics, each closely correlated with two-phase flow pressure drop trends. Irregularity of the Segmented regimes and related influencing factors were addressed and discussed. The average bubble length associated with the Segmented flows scaled approximately with a power law of the liquid volumetric flow ratio, which depends on aspect ratio, liquid superficial velocity, and the injection system. A simplified semi-empirical geometric model of gas bubble and liquid plug volumes provided good estimates of liquid plug length for most of the segmented regime cases and for all test-channel aspect ratios. The two-phase flow pressure drop was measured for the square test channels. Each Segmented flow sub-regime was associated with different trends in the pressure drop scaled by the viscous scale. These trends were explained in terms of the quantified flow topology (measured gas bubble and liquid plug lengths) and the number of bubble/plug pairs. Significant quantitative differences were found between the two-phase pressure drop in the polymer micro-channels of this study and those obtained from previous glass/silicon micro-channel studies, indicating that the effect of wall surface properties is important. Pressure drop trends on the capillary scale along gas bubbles extracted from the measurements in square micro-channels indicated a linear dependence on the Capillary number and did not agree with those predicted by highly idealized theory primarily because explicit and implicit assumptions in the theory were not relevant to practical conditions in this study.

Gas Condensate Reservoir Performance

Abstract Gas condensate reservoirs exhibit complex coupling between phase behaviour, interfacial tension, velocity and pore size distribution. Appropriate characterization of the in situ fluids and relevant flow testing can provide valuable insight into gas condensate reservoir forecasting. The following insights were obtained during the course of this testing:The importance of path dependence was shown to be significant when creating equilibrium phases below saturation pressure for use in quantifying phase interference. Differences, due to compositional path, in API gravity of liquids in solution were quantified to be as much as 10 degrees, with molecular weight differences over 110 daltons.End-point saturations, such as trapped gas and residual condensate saturation, are sensitive to the level of interfacial tension (IFT). Critical condensate saturation was less sensitive to IFT (pressure).The two-phase injection approach and the protocol whereby explicit measurement of relative permeability is performed provide a very thorough gas-condensate reservoir data set, which are amenable for use in simulation and reservoir production forecasting. Background This paper discusses performance of gas condensate reservoirs. These reservoirs have a reservoir temperature located between the critical point and the cricondentherm on the reservoir fluid's pressure-temperature diagram. This is the only unique and accurate means of identifying gas condensate reservoirs; any other definition [condensate-gas ratio, C7+ molecular weight (MW) or C7+ API gravity] is specious and ersatz. In these reservoirs, as the pressure drops, vapour and liquid phases result. Capillary pressure causes phase interference which usually reduces gas productivity. A cross-section of interesting topics that show the complexities of gas-condensate reservoir production have been reported in the literature(1–7). All of the relevant parameters, if well understood, will lead to more accurate evaluation of the amount of hydrocarbon in place, the rate at which the resource can be produced and the optimization strategies as the reservoir matures. Introduction In this paper, retrograde condensate characterization and properties measurement, explicit relative permeability and two-phase dynamic steady-state measurements are discussed. Not withstanding the very specific nature of this paper in quantifying phase behaviour-fluid flow coupling in the laboratory, it was considered important to provide a short commentary on sampling of gas condensate fluids that form the foundation on which experimental gas condensate testing is built. Extensive treatment of this theme was beyond the scope of the current paper. Retrograde Condensate Sampling The bottomhole flowing pressure (PBHF) must be lower than reservoir pressure to induce flow. If the PBHF is less than dew point pressure then liquids drop out in the porous media around the production well. The gas is much more mobile than the condensate and, therefore, the gas-condensate ratios (GCR) exhibited at surface are commonly higher than that of the reservoir fluid. A further complication of this problem is that the composition of the surface liquid also changes. When the PBHF is above dew point, the MW of the surface liquid is the highest. Figure 1 shows the change in composition incident to decreasing bottomhole pressure.

Fixation and distribution of bacterial activity in sand to induce carbonate precipitation for ground reinforcement

The mechanical properties of soil (cohesion, friction, stiffness and permeability) are important parameters for engineering constructions and ecosystems in sedimentary environments. BioGrout is an in situ soil strengthening technique involving microbial-induced carbonate precipitation (MICP). This process involves hydrolysis of urea by bacteria containing the enzyme urease in the presence of dissolved calcium ions, resulting in calcium carbonate precipitation. In order to control the BioGrout process for engineering applications, it is necessary to improve understanding of the relevant phenomena and develop efficiencies to enable up-scaling of the technology to suit commercial applications. Control of a homogeneous distribution of bacterial activity in a sand bed is considered crucial in order to prevent clogging during injection and provide homogeneous reinforcement results. This paper describes a methodology to distribute and fix bacteria (with their enzyme activity) relatively homogeneously in a sand bed, before supplying cementation reagents. The methodology is based on a two-phase injection procedure: a bacterial suspension is injected into the sand body, immediately followed by a fixation fluid (i.e. a solution with high salt content). It is proposed that bacteria are retarded by adsorption and filtration processes and are permanently adsorbed to the sand grains when overtaken by the fixation fluid. The presented experimental approach for optimizing bacterial fixation in porous media can be used as a tool to design the treatment protocol for engineering applications in practice.

Analytical Solutions for Multicomponent, Two-Phase Flow in Porous Media with Double Contact Discontinuities

This article presents the first instance of a double contact discontinuity in analytical solutions for multicomponent, two-phase flow in porous media. We use a three-component system with constant equilibrium ratios and fixed injection and initial conditions, to demonstrate this structure. This wave structure occurs for two-phase injection compositions. Such conditions were not considered previously in the development of analytical solutions for compositional flows. We demonstrate the stability of the double contact discontinuity in terms of the Liu entropy condition and also show that the resulting solution is continuously dependent on initial data. Extensions to four-component and systems with adsorption are presented, demonstrating the more widespread occurrence of this wave structure in multicomponent, two-phase flow systems. The developments in this article provide the building blocks for the development of a complete Riemann solver for general initial and injection conditions.

Improvements of the base bleed effect using reactive particles

A numerical study of the base drag reduction of axisymmetric body projectiles in supersonic flight using a base bleed injection is presented in this paper. Unsteady computations of compressible viscous flow have been achieved in order to investigate the coupled effect of the bleed temperature and the bleed mass flow rate on the base pressure. The idea developed in the study, consists in the addition of metallic particles in the propellant composition used to provide the additional mass injected in order to obtain the lowest base drag. Indeed, for a low mass addition, a significant increase of the mixture energy is expected due to the particles combustion. Base flow with reactive two-phase injection is then simulated. Results show the ability of the method to describe such flows and the efficiency of the particles combustion to increase the base bleed reducing drag effect.

Gas and condensate relative permeability at near-critical conditions: capillary and Reynolds number dependence

Measurement of gas and condensate relative permeabilities is typically performed through steady state linear coreflood experiments. Experiments are normally designed to minimize the saturation variations throughout the core so that the relative permeabilities can be evaluated through direct application of Darcy's Law to each phase. This study addresses relative permeability prediction from linear corefloods for low permeability, near-critical gas–condensate systems at velocities typical of the near wellbore region. In this regime, relative permeabilities are capillary number dependent and non-Darcy terms are significant. This paper looks at combining both the nonlinear (in velocity) terms into a single “effective relative permeability” term. Synthetic “experimental” data were generated numerically through simulation (and not from laboratory experiments). The synthetic data considered a range of capillary numbers at both low and high Reynolds numbers. Simplified correlations were developed to represent both the gas and condensate effective relative permeabilities. Effective relative permeabilities were then history-matched from the synthetic experimental data through non-linear regression. History matching results indicate that the Reynolds number should be included explicitly in the gas effective relative permeability correlation. Two-phase injection experiments are easier to interpret than single-phase injection experiments.

Analysis of Steady-state, Vapor-Liquid Concurrent Flow

ABSTRACT Steady-state methods are commonly used for the determination of the relative permeabilities of single component vapor-liquid systems, such as steam-water. Even though such experiments are performed under adiabatic conditions, the interpretation of results has proved to be difficult. Reasons involve phase change, heat transfer, capillarity and rate considerations. This paper presents a systematic study of the saturation and temperature distributions in steady-state, vapor-liquid flows and examines their sensitivity to parameters such as injection rate, permeability and core length. Two sets are analyzed, one pertaining to the simultaneous injection of a two-phase mixture (Sanchez and Schechter, 1987) and another involving phase change (liquid to vapor) within the core (Miller, 1951). End effects and, in general, effects associated with capillary heterogeneity are also analyzed. Solution trajectories in the temperature-saturation plane are constructed. They allow a unified approach to the two problems (two-phase or single-phase injection), which are shown to lie on different parts of the same trajectory. Minimum conditions for the development of in-situ evaporation are developed. Then, the process sensitivity to parameter values is examined for steady-state two-phase injection and relative permeability estimation. It is found that a plateau region develops, within which the inlet saturation is approximately constant, although corresponding saturation profiles are not necessarily flat. Numerical estimates show that the estimation error involved increases with decreasing enthalpy and decreasing permeability.

Two-phase mass injection from the stagnation zone of a blunt body in a hypersonic flow

A mathematical model of the hypersonic steady gas flow over the stagnation zone of an axisymmetric blunt body ~Mth given twophase injection from the surface is proposed. The two-continuum model of a dusty gas [3] is used for describing the flow in the region of the walt. The problem is solved in the boundary layer and thin viscous shock layer approximations. On the basis of the numerical calculations the distribution of the parameters of the carrier and dispersed phases near the axis of symmetry is obtained. The similarity parameters determining the convective heat transfer are found. The stagnation point heat fluxes w~th and without particles are compared. The range of parameters on which particles can significantly reduce the heat transfer is determined. Research into the thermal erosion behavior of various materials in high-enthalpy gas flows and, moreover, the development of new active thermal protection techniques [1--3] make it necessary to investigate the effect on the thermal load of dispersed particles introduced into the flow from the body surface. In the above-mentioned applications a mixture of gas and disperse particles, which then move in a narrow region near the wall, is injected from the surface. Two-phase injection into a supersonic flow without allowance for the viscosity and thermal conductivity of the carder phase was previously considered in [4]. The influence of particles on the flow in the boundary layer without injection effects was investigated in [5, 6].

High performance heat pump systems accompanying two-phase compression process. COP improvement in quasi-static compression.

Two-phase compression heat pump cycles have been studied from the theoretical point of cycle analysis to clarify the optimum liquid injection conditions as a first and basic step for developing higher-performance high-temperature heat pump systems, which recover the heat from a 150°C heat source and supply a 300°C-thermal output. In the case where the working fluid is water, the COP is improved by utilizing a two-phase compressios process and an optimum gas-liquid ratio brings about the maximum value of COP. The two-phase injection cycle, in which the liquid partially extracted from the outlet of the condenser and the gas separated in the economizer are injected into an intermediate point of the compression process, can effectively improve the COP and reduce the discharge superheating.

A physical model for two-phase flow in steam injection wells

The injection of steam for the recovery of heavy oil is the predominant method of tertiary oil recovery. Annual production in the U.S.A. exceeds 480,000 barrels of oil per day (Leonard, 1986). As deeper resources are exploited, an accurate knowledge of the changes in steam temperature and quality with depth is required so that saturated steam is delivered to the oil reservoir at the proper rate, pressure and heat content. This knowledge is also needed to prevent thermal damage to wellbore equipment during the steam injection process. Upward two-phase vertical flow of steam and hot water occurs in geothermal wells. Geothermal projects in the U.S.A. use aquifers that produce hot water or a steam-water mixture. The two-phase mixture is separated at the surface, and the steam is used for power generation. Again, knowledge of steam pressure and quality variations are needed for proper sizing and design of equipment. Several methods (Farouq Ali, 1981; Fontanilla and Aziz, 1982) are available to calculate changes in temperature, pressure, and steam quality with depth during two-phase steam injection and production from vertical wells. In general, these methods use correlations of dimensionless variables and do not model the process directly. This work was undertaken to find physical models that permit the analytical prediction of the flow patterns, pressure changes, and heat losses in two-phase vaporliquid injection or production.

Supersonic flow past axisymmetric body with strong local two-phase surface injection

It is known [1–3] that in order to provide heat shield or to improve the aerodynamics of the body strong injection of cooling gas into the supersonic stream is utilized. Analysis of flow characteristics in the neighborhood of the solid body in the presence of strong single-phase injection and the effect of injection on the aerodynamic characteristics of some axisymmetric bodies are given, e.g., in [2–4]. Supersonic flow past a blunt-nosed axisymmetric body with blowing of a mixture of gas and solid particles through a porous segment in the leading edge region is considered in the present paper. Such a situation could occur in modeling the breakdown of the heat shield of a flight vehicle during its reentry into the thick layers of atmosphere and also in the case of forced introduction of particles in the flow of the injected gas in order to break up the leading edge shock and accordingly the variation in the drag of the body [5]. A description of the trajectory of the particles has been obtained as a result of numerical and analytical solution of the problem and their analysis is used to arrive at conclusions on their intersection and, consequently, also on the multiple-valued nature of the flow parameters in the neighborhood of the line dividing the external flow and the injected two-phase mixture. Sufficient conditions for multiple-valuedness have been analytically found which agree with numerical results. It has been established that with a change in composition of sufficiently small particles within the limits 0.1 to 0.6 by weight of the injected mixture the drag coefficient of the body does not change by more than 10%.

Automated Injection Procedure for the CERN Intersecting Storage Rings (ISR)

The performance of the ISR is critically dependent on the conservation of the transverse beam size. One important source of transverse blow-up for proton beams is injection errors. A two-phase injection procedure is designed to limit these errors to negligible proportions. The first phase, based on the analysis of the first turn beam trajectory, reduces the errors sufficiently to ensure that nearly all of the particles ejected by the CERN-PS will circulate on the ISR injection orbit. The remaining errors are reduced in a second phase based on the accurate measurement of the injection error amplitude, i.e. the amplitude of the coherent betatron oscillation of the injected beam. The residual error causes a blow-up not exceeding a few per cent. The two phases are fully automated using the ISR control computer.