Injection Pressure Drop Research Articles

Determination and controlling of gas channel in CO2 immiscible flooding

In order to study the effect of gas channel on CO2 flooding in porous medium, the gas flow velocity is divided into two parts: gas breakthrough stage and gas channeling stage. The breakthrough velocity has an exponential relationship with concentration in the frontal zone of gas area, while the channeling velocity has a linear relationship with injection pressure drop. A new method is proposed to determine the gas channeling time by using the trend line of gas–oil ratio in gas breakthrough and gas channeling stage. The production characteristics in CO2 flooding show that recovery greatly improves after the gas breakthrough at the outlet of core sample, and most of the oil displaces before gas channeling. Thus, the extension of the stage between gas breakthrough and gas channeling becomes a key factor to improve CO2 recovery efficiency. Improving the injection pressure drop increases the dissolved gas diffusion, which will improve the oil displacement efficiency of simultaneous oil and gas production stage, but it also increases gas channeling velocity, which will increase the gas/oil ratio sharply and result in ineffective gas injection. An optimal displacement pressure can control the diffusion rate, the channeling rate and improve the recovery of CO2 flooding effectively. Keeping a constant pressure drop, increasing of injection pressure can not only increase the diffusion rate, but also reduce the gas channeling velocity. The achievement of a lower gas channeling velocity is advisable for extending the stage of gas–liquid production, and improving the immiscible CO2 recovery significantly.

CFD Modeling of Kerosene Combustion with Various Initial Conditions and Fuel Droplet Diameters

This paper presents the numerical models for the analysis of combustor fuel spray, characteristics, invarious injection conditions in a can type of combustor with a double stage radial swirler. Spray consists of twofundamental and consecutive steps, means the primary breakup and the secondary breakup. The primary breakupis modeled by Linearized Instability Sheet Atomization (LISA) which are mostly used in a pressure swirlatomizers. Secondary breakup is modeled by Taylor analogy breakup model (TAB). The trajectory and velocityof generated fuel droplets is determined by Lagrangian Particle Tracking. Characteristics of jet breakup, dependson a variety of factors such as turbulence, injection pressure drop, velocity profiles, nozzle geometry, and thephysical state of the liquid fuel. In this paper Jet-A aviation fuel (kerosene), modeled as a two-componentsurrogate fuel (by mass 60 % C10H22 and 40 % C9H12). The standard k–e model with the enhanced walltreatment and the Euler-Lagrange method were employed for the simulation of the turbulence and spray. Allresults of the simulation in this paper are analyzing in 3 various injection conditions and one of these cases waschosen and implemented in a real annular combustion chamber of a gas turbine. A PDF Flamelet model wasemployed to simulate combustion process.

Optical Methods for Studies of Self-Excited Oscillations and the Effect of Dampers in a High Pressure Single Sector Combustor

Self-excited periodic instabilities in a staged lean burn injector could be forced by operating the combustor at off-design conditions. These pressure oscillations were studied in a high pressure single sector combustor with optical access. Two damper configurations were installed and tested with respect to their damping efficiency in relation to the configuration without dampers. For a variety of test conditions, derived from a part load case, time traces of pressure in the combustor were measured, and amplitudes were derived from their Fourier transformation. These measurements were performed for several combinations of the operating parameters, i.e., injector pressure drop, air/fuel ratio (AFR), pilot/main fuel split, and preheat temperature. These tests “ranked” the respective damper configurations and their individual efficiency with respect to the configuration without dampers. Although a general trend could be observed, the ranking was not strictly consistent for all operating conditions. For several test cases, preferably with pronounced self-excited pressure oscillations, phase-resolved planar optical measurement techniques were applied to investigate the change of spatial structures of fuel, reaction zones, and temperature distributions over a period of an oscillation. A pulsating motion was detected for both pilot and main flame, driven by a pulsating transport of the liquid fuel. This pulsation, in turn, is caused by a fluctuating air velocity, in connection with a prefilming airblast type atomizer. A phase shift between pilot and main injector heat release was observed, corresponding to a shift of fuel penetration. Local Rayleigh indices were calculated qualitatively, based on phase-resolved OH chemiluminescence used as marker for heat release, and corresponding pressure values. This identified regions, where a local amplification of pressure oscillations occurred. These regions were largely identical to the reaction regions of pilot and main injector, whereas the recirculation zone between the injector flows was found to exhibit a damping effect.

Direct observation of single- and two-phase flows in spacer filled membrane modules

Spacers are introduced in membrane modules as turbulence promoter to enhance mass transfer while the detailed hydrodynamics inside the flow channel is hard to recognize. The situation becomes more complicated when air bubbles are incorporated as second phase, i.e. air sparging processes. In this work, transparent modules with precise slit accommodating for spacer were fabricated to visualize the behavior of single- and two-phase flows. For single-phase flow, dye injection method and pressure drop measurement were conducted in channel with and without net-type spacer. The results show that with the incorporation of the spacer the critical Reynolds number decreases from 1000 to 100 approximately which is lower than channel with ladder-type spacer always adopted by researchers. For two-phase flow consisted of liquid and air bubbles, the behavior of bubbles in coalescence system (water–air) and non-coalescence system (ethanol–water–air) were investigated respectively. With stationary liquid in tubular module, the bubble size increases accordingly with the increase of the gas flow rate while the size of the bubbles is obviously shrunken in non-coalescence systems. In empty rectangular channel, the smallest bubble we found (2mm approximately) in non-coalescence system is larger than the channel height. Therefore bubbles of both systems could keep contact with channel wall which equips them with ability to clean fouling. Three different flow behaviors of two-phase flow are classified from the flow visualization in channel with diamond-like spacer D1. For both systems, working conditions in region (III) is optimal since the flow distribution is well managed. The threshold of region (III) is higher in non-coalescence system, because higher liquid and gas flow rate is required to sweep stagnant bubbles away. Higher porosity contributes less to the energy saving therefore porosity between 0.887 and 0.917 for the test spacer geometry is appropriate. Ladder-type spacers could avoid maldistribution of bubbles, which are suitable for conditions required lower gas and liquid flow rate.

GHGT-12 Performance of the IGCC with distributed feeding of H2 in the gas turbine burner

Abstract A main hurdle for realizing the IGCC with CO 2 capture is the lack of gas turbines capable of burning hydrogen in an environmental-friendly, yet energy-efficient manner. With currently proposed combustion schemes an efficiency penalty is caused by the preparation (separation and compression) of the inert diluent, i.e. nitrogen. Distributed Fuel Injection (DFI) , where hydrogen is provided to the combustion air through a H2-separating membrane or a porous wall, could be a means of avoiding both concentrated fuel point sources and N2 dilution of the fuel. The paper presents two potential schemes for DFI: Scheme 1 with upstream H2 separation and scheme 2 with integrated H2 separation from the shifted syngas. First process simulation results for an IGCC with a reheat gas turbine yielded an IGCC efficiency increase of 0.7%-points with Scheme 1 and of 1.3%-points with scheme 2, compared to a reference case with nitrogen fuel dilution. This is mainly due to savings in N2 compression work but for scheme 2 also because the partial pressure difference of H2 over the Pd membrane can be employed as driving force. The results should however be regarded as indicative only one of the reasons being that fuel injection pressure drop for DFI is yet unknown, and is presumably a trade-off between membrane/porous wall size.

Wormhole Propagation Behavior and Its Effect on Acid Leakoff under In Situ Conditions in Acid Fracturing

In acid fracturing, excessive acid leakoff is thought to be the main reason that limits fracture propagation and live acid penetration distance. Although acid leakoff has been studied under experimental conditions, the acid leakoff theory developed under experimental conditions cannot be extended to in situ conditions because the injection rate or pressure drop across a core plug is fixed in the experiments. In this paper, we used a model that couples a two-scale continuum model simulating wormholing in the invaded zone and a reservoir flow model for the compressed zone to simulate acid leakoff process under in situ conditions. Based on this model, we investigated wormhole propagation behavior and its effect on acid leakoff under in situ conditions. The study shows different wormhole propagation behavior under in situ conditions from that under experimental conditions. Wormholes grow fast at the beginning and slow down at later time due to the rise of reservoir pressure caused by the leakoff and the growth of the invaded zone. In oil reservoirs, wormholing has minor effect on acid leakoff because of small compressibility and relatively high reservoir fluid viscosity, but in gas reservoirs, the influence of wormholing on acid leakoff becomes significant due to large compressibility and low reservoir fluid viscosity. Acid viscosity has more notable influence on acid leakoff in gas reservoirs than in oil reservoirs.

Effects of Recess Length on Discharge Coefficients of Swirl Coaxial Injectors

An experimental study has been performed to investigate the effects of the recess length on the discharge coefficients of swirl coaxial injectors. Liquid oxygen and kerosene (Jet A-1) were burned in a range of mixture ratios (1.97–3.31) and chamber pressures (43–80 bar) in small liquid rocket thrust chambers. Each thrust chamber was equipped with 19 liquid–liquid swirl coaxial injectors. While changing the recess length of the injectors, static pressure, temperature, and flow rate data were collected and analyzed to calculate the discharge coefficient. The discharge coefficients obtained from hot-firing tests are compared with those from cold-flow tests. Operating conditions such as oxidizer-to-fuel mixture ratio and chamber pressure have some influence on the discharge coefficients. The recess length of the injectors significantly affects the discharge coefficients in the hot-firing tests, but not in the cold-flow tests. The results show that the longer recess length gradually reduces the discharge coefficients. Especially when the liquid oxygen film collides with the kerosene film inside the fuel nozzle, the discharge coefficients of the outer fuel-side injectors decrease more remarkably than those of the inner oxidizer-side. It is thought that the flame anchored inside the recessed region in the swirl coaxial injector confines propellant flows, and the internal mixing of propellants strongly disturbs the outer fuel flow. Since the discharge coefficient is directly related to the injection pressure drop, the effects of recess length on discharge coefficients must be carefully considered when designing liquid–liquid swirl coaxial injectors.

Simulation on the Surfactant-Polymer Flushing of Heterogeneous Aquifers Contaminated with Nonaqueous Phase Liquids

:A three-dimensional, multiphase, multicomponent compositional simulator is employed to simulate the NAPL migration and groundwater flow and transport in spatially correlated heterogeneous fields during surfactant-polymer flushing. Spatial distributions of saturations in the NAPL and temporal changes of organic recovery, effluent concentrations of organics and surfactant, and pressure drop at the injection well were compared with those in homogeneous aquifer and related to heterogeneity. Variations in permeability fields have a pronounced effect on the organic recovery efficiency due to the long-term persistence of nonaqueous phase liquid in low permeability regions and additional dispersion caused by the randomly heterogeneous aquifer. Results of simulations illustrate associated tailing of effluent organic concentrations at the production well. Permeability heterogeneity also increases the injection pressure drop and results in significant loss in injectivity over the remediation life. For a small slug, surfactant-enhanced remediation had a relatively small improvement on the recovery of NAPL, especially in highly heterogeneous aquifers. The tendency of the high concentration organic plumes to migrate to the other layer by gravity forces and crossflow is also demonstrated and is shown to enhance remediation of aqueous phase organic.

Studies on Spray Behavior of a Pressure Swirl Atomizer in Transition Regime

Hollow-cone sprays produced by pressure-swirl atomizers find application in a wide range of propulsive systems. During throttling and under low-thrust requirements, however, the spray pattern may change from a fully developed hollow cone to a solid (collapsed) spray resulting in an increase in pollutant emissions, thermal spikes, and decrease in efficiency. Also, the solid and developing cone regimes are susceptible to flow instabilities. The transition regime from a collapsed to a developing hollow-cone spray from a pressure-swirl atomizer has been investigated in this paper. The present atomizer uses a helical insert having a swirl number of 3.6. At low injection pressures (ΔP inj ) the spray cone angle did not change appreciably with increasing ΔP inj as a result of the dominating surface tension forces. However, with increasing pressure, the conical sheet opens up. Under these conditions, the spray cone angle increases monotonically with injection pressure, finally leading to fully developed hollow-cone regime. Experiments were also carried out to determine spatial drop-size distribution and patternation. Average drop sizes were found to decrease from 150 to 100 μm for a twofold increase in injection pressure drop, along with a narrower drop-size spectrum with the transition from collapsed to developing cone regime. Increasing axial distance resulted in a narrower spray drop-size spectrum with slightly higher drop sizes. This could be attributed to the combined effect of coalescence, evaporation, and aerodynamic influences on drops. The drop size along the spray axis was found to be higher in comparison to the periphery for the collapsed spray regime, with a reversed trend in case of higher pressures. Mass distribution obtained using a mechanical patternator clearly reveals the flow features during the transition from collapsed regime to the developing cone regime.

A TECHNIQUE FOR DROP SIZE CONTROL DURING THROTTLING OF A ROCKET ENGINE

Experimental studies have been conducted on a new type of injector which can be used very advantageously in rocket engines designed for throttling applications. The aim is to keep the drop size constant for varying chamber pressures. The injector uses very small quantities of a gas to atomize a straight liquid jet before discharging into the combustion chamber. The concept is demonstrated over an eightfold variation of injector pressure drop. A feedback control system, which can regulate the air pressure with respect to the sensed chamber pressure, based on the input transfer function, so as to keep the drop size constant, is suggested. The transfer function is obtained from the experimental data. The major advantage of this injector is that it uses a very small quantity of gas, thereby limiting the weight penalty to a minimum. This system is much less complicated compared to variable area injector and cavitating venturi valves used for this purpose.

Experimental and Theoretical Studies of a Novel Venturi Lean Premixed Prevaporized (LPP) Combustor

A new gas turbine engine using a unique layout patented in Norway has a low-emission combustion system under development. The gas generator uses entirely radial rotating components and employs a dual entry LP radial compressor, a radial HP compressor, and a radial HP turbine. The power turbine is of a two-stage axial design, coupled to an epicyclical gear embedded in the exhaust duct. Several combustor concepts have been tested and evaluated during the development of the engine. The engine is targeted for marine, power generation, and train propulsion. For the marine and train application liquid fuel operation is needed, thus the primary focus in the development has been for a lean premixed prevapourised system. An interesting concept utilizing two venturi premixers has been studied intensively. By utilizing venturi premixers the following advantages can be achieved: (1) low overall pressure drop but high injector pressure drop and velocities in the mixing region (throat region), (2) high shear forces and drag imposed on the droplets enhancing droplet shedding and evaporation, and (3) excellent emission behavior at designated load conditions. Although these advantages can benefit gas turbine low-emission combustion, the challenges in using venturi premixers are: (1) venturis are susceptible to separation and thus flame stabilization within the venturi which is detrimental and (2) inlet flow disturbances enhance the tendency for separation in the venturis and must be minimized. Studies were launched to investigate a proposed combustor configuration. These studies included analytical studies, computational fluid dynamics (CFD) calculations of isothermal and combusting flow inside the combustor together with rig tests at atmospheric, medium, and full pressure. Finally, engine tests within the full operating range were conducted with very favorable emission figures for lean premixed prevaporized (LPP) operation. The system was capable of running at below 20 ppm NOx and CO, at elevated power for liquid fuel. Control of part load performance and emissions is by variable fuel staging of the two venturi stages. The paper highlights the features of the venturi combustor development and discusses the characteristics in terms of flow conditions and droplet motion, heat transfer, ignition delay time, and emissions.

Jet Interaction in Liquid-Liquid Coaxial Injectors

Interaction between two conical sheets of liquid formed by a coaxial swirl injector has been studied using water in the annular orifice and potassium permanganate solution in the inner orifice. Experiments using photographic techniques have been conducted to study the influence of the inner jet on outer conical sheet spray characteristics such as spray cone angle and break-up length. The core spray has a strong influence on the outer sheet when the pressure drop in the latter is low. This is attributed to the pressure variations caused by ejector effects. This paper also discusses the merging and separation behavior of the liquid sheets which exhibits hysteresis effect while injector pressure drop is varied.

Experimental study of liquid sheets formed in coaxial swirl injectors

The shape and disintegration characteristics of swirled annular liquid sheets formed in coaxial injectors are investigated. The effects of ambient pressure and gas flows over the outer and inner surfaces of the liquid sheet are determined. Two general regimes of annular sheets, comprised of a tulip shape and a conical diverging shape, are shown to be formed depending on injector pressure drop, swirl, and orifice size. The transition from the tulip shape to the diverging conical shape occurs when the centrifugal forces at the injector orifice exit exceeds the surface tension forces by about two orders of magnitude. A conical sheet is not formed in annular orifice when the radial clearance of the orifice is of the same order of magnitude as the thickness of the liquid film. The tulip-shaped sheet is very sensitive to small changes in environmental and injection conditions, unlike the diverging conical liquid sheet.

Experimental study on liquid quench of solid rocket motor

This article proposes a physical model for liquid quench of solid rocket motor and presents the results of experimental study. It is found that there is a critical value of injection pressure drop during liquid quench of solid rocket motor. The critical value of injection pressure drop increases with propellant energy (gy). The additive selected appropriately added in liquid is able to reduce significantly the liquid quantity required (LQR) Ws, for extinction of solid rocket motor. LQR reduced by the addition of 0.5% CE by weight in water are about 35 and 25% for double base propellant and nonmetalized polyurethane-ammonium perchlorate composite propellant, respectively. LQR is mainly dependent upon the propellant energy, i.e., it increases with increasing propellant energy. For pure water, Ws * O.lg^and for water + 0.5% CE, Ws * 0.76gy* The variation of LQR with the chamber pressure is related to pressure exponent of propellant (n). If n > 0, it increases with increasing chamber pressure; and if n < 0, it decreases with increasing chamber pressure. With the injection pressure drop increasing, LQR decreases and the depressurization rate of solid rocket motor increases, respectively. The experimental results and the analysis indicate that the theoretical study on liquid quench of solid rocket motor should include the coupling effects of transient burning of propellant, heat transfer of liquid jet impinged on burning surface, evaporation of liquid droplets, and internal ballistics of rocket motor.

Potential Benefit of CO2 in Oxygen Combustion

Introduction in-situ combustion with oxygen instead of air has high potential for recovering heavy and medium oils. Fig. 1 potential for recovering heavy and medium oils. Fig. 1 illustrates the oxygen combustion process. Among the many advantages is a higher concentration of CO2 ( is greater than 80 %) in the flue gas resulting from the absence of nitrogen. This allows more CO2 dissolution in the oil that helps swell the oil and reduce its viscosity, thus enhancing oil recovery. Although oxygen combustion has been investigated in the laboratory before, the beneficial effect of CO2 has never been demonstrated explicitly. In an attempt to simulate the nitrogen-free environment of oxygen combustion and to study the CO2 effect, we conducted a novel combustion tube run in which a CO2/O2 gas mixture was used in place of air. For comparison, a parallel test was performed that involved use of air at the same operating conditions. Experiment The laboratory apparatus and the experimental procedure have been described previously. A 13.4API [0.9765-g/cm3] California heavy oil and sands from the same reservoir were used. The oil has a viscosity of 6,600 cp [6.66 Pa s] at75F [23.9C] and an atomic H/C ratio of 1.52. The pack properties and operating conditions are listed in Table 1. Both runs were made in the dry combustion mode with about 21 % oxygen in the injection gas. Operations of both tests were smooth and ignition with the CO2/O2 mixture was successful. Results Stabilized combustion was achieved between 2 and 7 hours after ignition for both runs. The burning characteristics averaged over this time period are summarized in Table 1. The reaction temperature, the combustion front velocity, and the product gas composition for both tests were similar, except that the air test had a lower oxygen utilization. The fuel consumptions were practically the same for both runs. This was expected practically the same for both runs. This was expected since the temperature profiles in both runs were nearly identical and the fuel deposition process was largely a function of temperature. The oxygen/fuel ratios were also the same, indicating that the elemental compositions of the fuel were identical. It therefore appeared that substituting N2 in air with CO2 did not change the combustion characteristics for this oil. The oil displacement vs. volume burned is shown in Fig. 2. The fill-in time for the CO2/O2 run was a little longer because of a somewhat higher gas saturation. Once in production, the displacement rates in both runs were almost identical. The injection pressure and pressure drop across the tube are shown in Fig. 3. In pressure drop across the tube are shown in Fig. 3. In both tests, the injection pressure was set at 250 psi [1.7 MPa] by regulating the backpressure. The pressure drop started to increase shortly after ignition, indicating the formation of an oil bank ahead of the thermal front. It reached a maximum at about 2 to 2.5 hours when the oil bank started producing. As seen, the air test had a higher pressure drop that was associated with a bank of oil at the pressure drop that was associated with a bank of oil at the original viscosity, The oil bank in the CO2/O2 run, on the other hand, contained oil at a lower viscosity because of CO2 dissolution. As a result, less pressure drop was required to displace the oil at the same rate. Conclusions The system pressure of the tests was rather low, only 250 psi [1.7 MPa], simulating conditions in a typical psi [1.7 MPa], simulating conditions in atypical California heavy oil reservoir. P. 1137

Influence of the injector pressure drop on low frequency instability in liquid propellant rockets

Influence of the injector pressure drop on low frequency instability in liquid propellant rockets

Instruction in mechanical engineering

The incident shock wave strongly affects the transversal injection field in cold kerosene-fueled supersonic flow, possibly due to its affecting the interaction between incoming flow and the fuel through various operation conditions. Optimum selection of fuel injection parameters indicates optimum interaction between incoming flow and fuel. Based on three dimensional Couple Level Set & Volume of Fluids (CLSVOF) approach, a detailed Computational Fluid Dynamics model of a cold kerosene-fueled scramjet combustor is developed in this study. Next, the effects of various injection angles on the interaction between incident shock wave and transversal cavity injection are addressed. The injection angles are specified from 45̊ to 135̊ in 45̊increments when other operation parameters, i.e. the injection diameter, velocity and pressure drop are all constant. The CLSVOF-based predictions are focused on penetration height, span-wise expansion area, angle of shock wave and sauter mean diameter (SMD) distribution of the kerosene droplets. Our findings show that the penetration depth, span-wise angle and expansion area of the transverse cavity jet all increased with the injection angle, and that the kerosene droplets are more prone to breakup and atomization at the outlet of the combustor for the injection angle of 45̊. This study demonstrates the effectiveness of CLSVOF modeling for better understanding of kerosene-fueled supersonic mixing and scramjet combustor design improvement.