Two-phase Injection Research Articles

Measurements and analyses on the two-phase fuel transient flow characteristics of dual fuel co-direct injector

In this research, an innovative two-phase fuel transient flow coefficient measurement system is proposed to investigate the flow characteristics and coupling effects of two-phase fuel, and to fill the gap of the two-phase fuel flow characteristics measurement technology of dual fuel injector. For this purpose, microphotography technology is used to obtain the original image of the injector hole, and the accurate area of the injector hole can be obtained by image processing. The two-phase injection momentum and the transient injection pressure are measured by the impact force sensor and the pressure sensor respectively, and the two-phase fuel transient flow coefficient is obtained. Due to the change of the increasing rate of the effective flow area at the nozzle, the gas transient flow coefficient shows two different increasing trends during the upward stage of the gas needle valve. With the background pressure increase, the maximum gas transient flow coefficient decreases and injection duration increases. The influence of pilot diesel injection on subsequent gas injection stages is mainly reflected in that when the gas energizing time is 0.8 ms, the fluctuation range of gas mass flow caused by diesel injection is 52.6%, and the fluctuation range is 14.9% when the gas energizing time is 2 ms, but the influence of diesel injection on the peak value of gas transient flow coefficient can be ignored.

Comparative research on vapor injection heat pump with a novel flash tank

Two major problems for the vapor injection heat pump systems with the flash tank are the high discharge temperature and the lack of flash tank design theoretical basis, which would limit its wide application in extreme operating conditions. One possible way to overcome these problems is to effectively control the two-phase injection in the flash tank by optimizing its structure. The use of the proposed novel flash tank in the quasi-two-stage vapor injection cycle represents an economic and controllable solution. This research experimentally analyzes the influences of flash tank structure and volume on the system heating performance under different compressor frequencies and injection pressures at the ambient temperature of −10 °C. The comparative analysis is done finding that the novel flash tank could maximumly improve the system Coefficient of Performance (COPh) by 6.4% in this test, compared with the traditional type A flash tank cycle. In the meanwhile, a bad design of novel flash tank size could represent a loss of COPh improvement between 5.73% and 13.5%. Due to the particular structure, the implementation of the novel flash tank also allows the injection mass flow ratio can keep a linear relationship with the injection pressure. Moreover, the refrigerant liquid can be regularly injected into the compression chamber to control discharge temperature under 100 °C. From all the analysis, guidelines for optimizing the control strategy and the flash tank design are put forward, which can be used to perfect the real thermodynamic model of the flash tank rather than the ideal two-phase separation model.

Investigation on improving the heating performance of a heat pump using a rotary compressor with vapor and two-phase injection

Refrigerant injection technique can be applied to heat pumps in cold regions to enhance performance and reliability, but currently this technique is mainly used in scroll compressors, and relatively few applications are for rotary compressors. In this paper, the performance of a vapor and two-phase injection (VTI) heat pump with a rotary compressor is experimentally studied under different injection pressures and compressor frequencies. Meanwhile, a numerical model with satisfactory reliability and practicality is developed to predict the heat pump performance. According to the prediction model, the optimal injection pressure for maximal heating capacity and efficiency is analyzed as a function of the injection ratio under different working conditions and the risk of wet compression is analyzed under various operating conditions. The optimal heating capacity and COP are obtained simultaneously under an injection pressure equaling the geometric mean of the evaporating pressure and the condensing pressure and an injection refrigerant state is near the saturated gas state, which improve by 23.76–42.80% and 4.22–8.96% over the non-injection compressor respectively at evaporating temperatures between 0 °C and −30 °C. For fixed-frequency compressors, a fixed injection port area is found to achieve optimal heating performance under any operating conditions, for example, it is about 2.4 mm2 under 50 Hz. Further, it is easier to form a two-phase injection under a higher injection pressure or lower compressor frequency, and a lower injection quality helps to decrease the discharge temperature but to increase the risk of wet compression.

Effects of injection styles on heating performance of a heat pump with sub-cooler refrigerant injection: Experimental and thermodynamic analysis

The performance improvement of heat pump depends on the appropriate injection style such as liquid injection, vapour injection and two-phase injection. In this work, experimental and theoretical investigation on the heat pump with R410A refrigerant reveals three kinds of injection styles can be selectively achieved in the same injection device by suitable control of the sub-cooling electronic expansion valve. Liquid injection and vapour injection improve the heating capacity (Qh), mainly due to the increase of heat exchange in the sub-cooler and compressor compression work, respectively. Two-phase injection lifts the Qh owing to these two effects. Subsequently, the effect of two-phase injection on improving the heat pump performance is superior to the other two injection styles. For instance, the maximum Qh were 14.4 kW at 60 rps with the liquid injection, 12.5 kW and 13.4 kW at 85 rps with vapour injection and two-phase injection, and 8.1%, 7.0% and 18.3% higher than those without injection, respectively. The corresponding coefficient of performance was improved by 10.4%, 4.5% and 10.6%, respectively. Furthermore, the model based on the pressure-enthalpy diagram has been developed to analyze the experimental results and expound the main factors affecting the heat pump performance under different ambient temperatures.

Preferred injection method and curing mechanism analysis for the curing of loose Pisha sandstone based on microbially induced calcite precipitation.

As a loose rock formation with low lithogenic property, low structural strength, and poor intersand cementation, Pisha sandstone is susceptible to chemical weathering and extreme soil erosion and has become an important source of sediment for the Yellow River. There is limited information available on the conditions of microbial distribution homogeneity under grain-mediated conditions in Pisha sandstones, as well as on the influence of dissolved minerals on calcium carbonate morphological mechanisms. In this paper, microbially induced calcium carbonate deposition was used to reinforce and improve the loose Pisha sandstone. First, the influence laws of the single-phase/self-absorption two-phase injection method and added solvent on the curing indexes such as curing volume, curing depth, calcium carbonate yield, and unconfined compressive strength of the specimens were discussed. Field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction spectroscopy were used to analyze the microstructure of the cemented sand columns, as well as the mineral phases and distribution of the biomineralization products mechanistically. The results demonstrated that the single-phase injection treatment could only achieve local solidification of the Pisha sandstone sand column, whereas the self-absorption two-phase injection method could result in a more uniform spatial distribution of bacteria and a monolithic specimen, in which the calcium carbonate yield increased with increasing low concentration CaCl2 injection. The compressive strength appeared to increase significantly, and the effect of the applied liquid CO(NH2)2 was not obvious. Montmorillonite underwent dissolution during the mineralization process, eliminating the characteristics of Pisha sandstone swelling in water. Under the effect of biomineralization, calcium carbonate crystals are formed to wrap around the Pisha sandstone particles, changing their particle size and increasing the interparticle roughness. Meanwhile, the interstices between particles are filled via calcium carbonate precipitation, effectively forming cementation points that can significantly improve the strength of the Pisha sandstone. The results of this study provide a theoretical basis for the application of biomineralization technology in the ecological restoration of Pisha sandstone areas.

Analysis of Injection-Locked Ring Oscillators for Quadrature Clock Generation in Wireline or Optical Transceivers

Injection-locked ring oscillators (ILROs) are widely used for quadrature clock generators (QCG) in multi-lane wireline or optical transceivers because of their low power, low area, and technology scalability. However, locking a four-stage I/Q oscillator with a two-phase injection signal generates imbalances in amplitude and phase, resulting in I/Q phase errors and degraded jitter performance. This paper proposes a modified frequency-domain analysis with amplitude constraint for even-phase ILROs. Combining theoretical derivations with simulation results in 28nm CMOS technology, the behaviors of ring oscillators with partial injection and ILRO-based QCG are discussed and concluded.

Analysis of optimal intermediate temperature and injection pressure for refrigerant injection heat pump systems with economiser

A heat pump cycle with refrigerant injection is one of the effective means for enhancing the heating performance in low-temperature climates. The intermediate temperature and injection pressure have been proven to be important parameters influencing the operating performance of a heat pump system. Previous studies on optimal intermediate pressure were mostly based on empirical formulas, and the calculation result greatly depended on the available scope of the empirical formula, especially in low-temperature conditions. In this study, the optimal intermediate temperature of the refrigerant injection cycle, including the vapour injection cycle and two-phase injection cycle, was analysed through theoretical derivations. This method is based on a thermodynamic analysis of the system and the thermodynamic properties of the R134a refrigerant. The aim of the theoretical analysis was to determine the intermediate temperature and injection pressure corresponding to the maximum COP of the system. First, the factors influencing the optimal intermediate temperature of the two injection cycles were studied using the theoretical calculation model. The optimal intermediate temperature was more sensitive to the system subcooling than the suction superheat. Increasing the heat exchange efficiency of the economiser is conducive to improving the heating COP. For the same operating conditions, the optimal injection pressure was higher than the empirical value. Second, an experimental system of refrigerant injection with an economiser was built to verify the accuracy of the method. The results indicated that the optimal injection pressure calculated by the theoretical derivation method was in good agreement with the experimental values for both the vapour and two-phase injection cycles. The maximum error of the injection pressure was within ±3%.

Experimental investigation on control strategy of electric vehicle heat pump with refrigerant injection at low temperature

A heat pump cycle with refrigerant injection is one of the effective means to enhance the heating performance of electric vehicles in low temperature climate. The control strategy is very critical for the application of refrigerant injection technology in electric vehicles. In this paper, the variation of cabin load demand with ambient temperature is first presented for electric vehicles. Secondly, a test bench of heat pump system with refrigerant injection is built to compare the system heating performance under different control strategies. Considering the compressor discharge temperature and the load demand, the applicable temperature range under different control strategies is determined. The experimental results show that the control strategy of the main branch with slightly wet can effectively reduce the compressor discharge temperature and improve the heating performance of the system. The compressor discharge temperature can be reduced by up to 23°C with above control strategy. The system heating capacity and COP can be increased by up to 5.7% and 4.7%. Vapor injection cycle can meet the demand at the ambient temperature above -15°C. The two-phase injection cycle further extends the temperature range of the system operation at low temperature, and the lowest temperature can reach -22°C.

Numerical analysis of a two-phase injection refrigeration cycle using R32

The present paper reports the performance of a popular refrigerant R32 (Difluoromethane, CF2H2) experiencing the two phase injection process. Two phase injection process may lower the discharge temperature of a multistage compressor. In order to investigate the role and impact of two-phase injection on a compressor, a Scroll compressor is selected because scroll compressor has high tolerance for liquid refrigerant. A reputed compressor is chosen where all the operating conditions and specifications are available in public domain. The modelling and analysis of refrigeration system is carried out using a simple MATLAB code. Around 200 iterations were performed for four different condensing and evaporating temperatures. The maximum reduction in discharge temperature is found to be 44°C when compared to R410A used in the same system.

Associative polymers for disproportionate permeability reduction – Formation wettability effects

Core-based laboratory experiments were performed on water- and chemically-treated-oil-wet Berea sandstone long-core samples to investigate the disproportionate permeability reduction (DPR) potential of a low-molecular weight associative polymer. The impact of single- and two-phase DPR treatments were considered at 60 °C. In the experiments conducted, real-time electrical resistivity measurements were obtained during the coreflood tests to serve as (a) a valuable tool for fluids saturation monitoring and (b) improved core fluids saturation evaluation in flooded porous media. Results from DPR treatments in water-wet cores showed high initial oil residual resistance factors, RRFo (≈20), followed by relatively long clean-up times; stabilized RRFo was achieved at relatively high PVs of oil injection (≈25). For the range of the post-treatment pressure gradients applied in the laboratory experiment, no DPR effects were observed for the water-wet core samples. However, the different shear-dependent behavior for the oil and water phases in the treated zone suggests that a positive DPR effect is possible at extrapolated low post-treatment applied pressure gradients; this could also be translated as higher clean-up times. For the two-phase DPR treatments in water-wet cores, RRFo can be significantly reduced to approximately 8, while RRFw stabilized at the relatively high value of 40. However, the required significantly long clean-up period during oil flow through the treated zone may question the efficiency of the achieved DPR effect. For the two-phase DPR treatment in oil-wet cores, stabilized RRFo were achieved at considerably lower injected oil PVs, i.e., shorter post-treatment clean-up periods were required. In addition, distinguishably smaller RRFo values were achieved for the oil-wet cores compared to the water-wet ones with a substantial separation from the achieved RRFw values (i.e., faster attainment of low values ranging between 6 and 4 for 15 to 40 injected PVs clean-up duration). These results indicate greater potential for effective positive DPR treatment for oil-wet medium treated through two-phase injection methods. Multi-rate tests conducted during polymer injection showed that the mobility reduction (resistance factor, RF) during DPR treatments, for both single- and two-phase methods, are shear dependent. In addition, post-treatment water and oil injection (production) showed different behavior regarding permeability reduction (RRF). In both core wettability cases, water flow experienced a noticeable power-law dependency to the applied differential pressure. On the other hand, the oil flow behavior in the two wettability cases was different; slightly shear-thinning for the water-wet cases and weakly shear-thickening for the oil-wet cores. In both cases the shear dependency of oil flow was much less pronounced than that of the water flow. Finally, the production water cut can be decreased to a noticeable amount using associative polymer DPR treatments. However, one must note that the water cut reduction (economic gain) is associated with a reduced total (oil) production rate (time loss); therefore, implementation of an associative polymer DPR treatment should be considered carefully.

Effect of Hydrocarbon Contamination on Biostabilization of Soil Contaminated with Motor Oil and Gasoline

Environmental problems caused by soil contamination can cause changes in the physical, chemical and geotechnical properties of the soil. Research on a suitable method for soil improvement has focused on the use of biological methods for soil improvement and remediation. Microbial calcium carbonate precipitation has been applied to solve many geotechnical problems. In this study, sandy soil was mixed with two conventional hydrocarbon pollutants and classic soil mechanics tests (compaction, direct shear, uniaxial and permeability tests) were implemented. The use of two bacterial solutions, two-phase injection and bacterial flocculation with injection of cementation solution, produced favorable results. Considering the lower inhibition of gasoline in low dilution, it was possible to improve with both methods. In the case of soil contaminated with motor oil, limitations on the use of microbial calcium carbonate precipitation were improved with the use of bacterial flocculation. The results of this approach were more suitable because the bacteria stabilized between the soil grains. XRD, SEM, EDS and wet chemical analysis were carried out to help confirm and interpret the results.

Energy performance evaluation of two-phase injection heat pump employing low-GWP refrigerant R32 under various outdoor conditions

The refrigerant R32 has been receiving significant attention as an alternative to R410A used in heat pumps, owing to its lower global warming potential. The two-phase injection (TPI) technique is introduced to achieve improved energy performance along with high system reliability in R32 heat pumps, owing to their high discharge temperature. The objectives of this study are to compare the performances as well as reliabilities of the R32 and R410A TPI heat pumps and provide the design guidelines for achieving the best performance with safe operation. The performances of the R32 and R410A TPI heat pumps are measured by varying compressor frequency and outdoor temperature. The TPI technique enables the R32 heat pump to operate at a higher compressor frequency under severe weather conditions. At low outdoor temperatures of −10 °C and −15 °C, the R32 TPI heat pump demonstrates a superior heating capacity and coefficient of performance (COP) compared with the R410A TPI heat pump. In addition, the injection parameters in the R32 TPI heat pump are optimized under various operating conditions.

Angular momentum tearing mechanism investigation through intermolecular at the bubble interface

Two-phase flow with gas-liquid component is commonly applied in industries, specifically in the refinery process of liquid products. Oil products with bubbles contents are undesirable in a production process. This paper describes an investigation of a process mechanism regarding the bubble breakup of the two-phase injection into quiescent water. The analytical model was developed based on the force mechanism of water flow at the bubble interface. The inertia force of water flow continually pushes the bubble while the drag force resists it. The bubble gets shapes change that affects the hydrodynamic flow around the bubble. Vortices with high energy density impact and make the stress interface over its strength so that the interface gets tear. The experiment was carried out by observing in the middle part of the injected flow. It was found that the forming process of bubble breakup can be explained as the following steps: 1) sweep model is a bubble pushed by the inertial force of water flow. The viscous force of water shears the surface of the bubble. The effect of both forces, the bubble changes its shape. Then trailing vortex starts to appear in near bubble tail. The second flow of water is in around of the bubble to strengthen the vortex energy density that causes fragments to detach from the parent bubble; 2) stretching model, the apparent bubble has high momentum force infiltrated in stagnant water depth and bubble ends are stretched out by the inertial force of the bubble and viscous force of water. The bubble surface has experienced stretching and tearing become splitting away. Based on the finding, the breakup process is highly dependent on the momentum of water flow, which triggers the secondary flow as the initial process of vortex flow, and it causes the tear of the bubble surface due to angular momentum

A multifluid Taylor-Galerkin methodology for the simulation of compressible multicomponent separate two-phase flows from subcritical to supercritical states

In various industrial combustion devices, such as liquid rocket engines at ignition or Diesel engines during the compression stage, the operating point varies over a wide range of pressures. These pressure variations can lead to a change of thermodynamic regime when the critical pressure is exceeded, switching from two-phase injection to transcritical injection. Such change modifies the topology of the flow and the mixing, thereby impacting the flame dynamics. This motivates the development of a unified methodology able to address both subcritical and supercritical flows within the same solver. To achieve this, the present work provides an extension of the supercritical real gas Taylor-Galerkin solver AVBP-RG to subcritical two-phase flows, based on diffuse interface models. In particular, the required developments for the integration of a multifluid model into the finite-element framework of this solver are detailed. Then, the ability of the solver to address a subcritical configuration is tested by simulating two subcritical-pressure operating points (G1 at 4.7 MPa and A10 at 1 MPa) of the MASCOTTE test bench operated by ONERA. This allows to confront the model with experimental data, showing good agreement.

Investigation of Waterjet Phases on Material Removal Characteristics

Abrasive waterjet (AWJ) controlled depth machining, often referred to as abrasive waterjet milling, has proven to be one of the most flexible non-conventional production techniques for difficult-to-machine materials. However, the prediction of process results is challenging since existing process models are limited and the jet tool consists of fluid-, solid- and gas-phases i.e. multiple physical processes occurring simultaneously. In this paper, the influence of the distinguished phases of waterjet machining on the material removal characteristics was investigated. In accordance with mechanical properties of the work piece, the process interference was considered at different structural modifications of 42CrMo4 steel, prior to processing and afterwards. With the help of different waterjet systems, the physical phenomena of the respective phases and their machining results were analyzed. Subsequently, a two-phase suspension jet containing water and solids and industry-standard 3-phase injector jet containing water, air and abrasives were used to machine a kerf pattern. Finally, a two-phase injection waterjet of sucking air without solids was used for post processing. A comparison was made by the geometrical features of the machining results. The applied understanding of the waterjet erosion process can lead to a better prediction and optimized waterjet results. Furthermore, the consequences may complete process models for simulation and support future applications of waterjet machining technique.

Effects of subcooling degree and injection super‐heating degree on performance of an air source heat pump with subcooler

For a heat pump, three injection styles including liquid, two-phase, and vapor injection are used to improve its performance. But there is no quantitative index to define the injection styles. They are distinguished from the injection configurations. The subcooler refrigerant injection (SCRI) is generally considered as the vapor injection. In this study, the injection super-heating degree (ΔTinj) is introduced as a technical parameter to define the injection style. The ΔTinj is affected by the subcooling degree (ΔTsc). These two parameters are used to study their effects on the heat pump performance. Experimental and theoretical analysis reveals that three injection styles can be selectively achieved in the SCRI configuration by the suitable control of the main and subcooling electronic expansion valves. Additionally, for liquid and two-phase injection, it can improve heating capacity (Qh) by heightening the ΔTsc to increase the heat exchange amount in the evaporator. For vapor injection, in addition to increase of the ΔTsc, the Qh can be enhanced by raising the ΔTinj to lift the compression power of the compressor. The two-phase injection is more beneficial to enhance the heat pump performance than the liquid injection and two-phase injection. The largest Qh and corresponding increase amplitude (δQh) were, respectively, obtained with two-phase injection to be 13 577 W and 13.5%, and the corresponding COP and increase amplitude (δCOP) were, respectively, 2.36 and 16.8%.

Novel optimized operating strategies of two-phase injection heat pumps for achieving best performance with safe compression

Two-phase injection (TPI) is known to be an effective technique in reducing the discharge temperature and increasing the heating performance of heat pumps. However, for actual applications of TPI heat pumps, optimized operating strategies to guarantee increased energy saving potential with safe compression are still not available. The objectives of this study are to analyze the optimum operating conditions and propose novel optimized operating strategies of TPI heat pumps for achieving best performance with safe compression. The performance of the TPI heat pump is measured as a function of the injection quality, outdoor temperature, and compressor frequency. The optimum and safe injection qualities for achieving maximum performance and high reliability are determined in various operating conditions. Moreover, three novel optimized operating strategies for injection quality in the TPI heat pump are proposed based on the empirical correlations for the electronic expansion valve, injection pressure, and discharge superheat, respectively. In addition, the operating characteristics of these optimized operating strategies are compared to provide a selection guide for actual applications.

Analysis of two-phase injection heat pump using artificial neural network considering APF and LCCP under various weather conditions

The objective of this study is to optimize the performance of a two-phase injection (TPI) heat pump considering annual performance factor (APF) and life cycle climate performance (LCCP). The performances of non-injection (NI), vapor injection (VI), and TPI heat pumps are measured under various outdoor temperatures. Based on the measured data, artificial neural network models for the NI, VI, and TPI heat pumps are developed to predict the performance indexes during cooling and heating seasons. As a result, the TPI heat pump shows higher heating capacity than the NI and VI heat pumps with a lower compressor discharge temperature in cold weather conditions. Therefore, the application of the TPI has a merit on reducing the size of the heat pump due to its lower back-up heater loss and over-capacity penalty. When the objective function maximizes the APF for system optimization in three climate regions, the TPI heat pump shows a 1.4–2.7% higher APF than the NI heat pump, and a 11.1%–18.1% smaller optimum rated heating capacity.

Performance comparison among two-phase, liquid, and vapor injection heat pumps with a scroll compressor using R410A

Although two-phase injection technique is expected to improve the performance and reliability of heat pumps in cold climate conditions, its application is limited due to wet-compression. In this study, a numerical model was developed and validated to predict the performance of liquid, vapor, and two-phase injection heat pumps. The performance characteristics of the liquid, vapor, and two-phase injection heat pumps with a scroll compressor using R410A were compared with the others, based on the predicted data. The optimum injection quality in the two-phase injection heat pump to achieve maximum COP was analyzed as a function of the injection pressure, compressor frequency, and outdoor temperature. The two-phase injection heat pump with the optimum injection quality exhibited the highest COP among all injection types with a proper discharge temperature. In addition, the two-phase injection heat pump with the optimum injection quality was more effective in COP improvement with decreasing outdoor temperature.

Two-phase injected and vapor-injected compression: Experimental results and mapping correlation for a R-407C scroll compressor

Vapor compression systems in hot climates tend to operate at higher pressure ratios, leading to increased discharge temperatures, higher irreversibilities during compression, lower specific enthalpies differences across the evaporator, and possibly a reduction in the compressor life due to the breakdown of the oil. To counter these effects, the use of economized, vapor injection compressors is proposed for vapor compression systems in high temperature climates. Such compressors are commercially available however an accurate method for mapping single-port injection compressors is unclear. This paper establishes compressor maps for a single-speed R-407C scroll compressor with two-phase injection and vapor-injected compression. A dimensionless-PI correlation for mapping the injection ratio, refrigerant discharge temperature, compressor power consumption, overall isentropic and volumetric efficiencies, and the heat loss ratio for these compressor maps and a variable speed R-410A compressor with vapor injection is presented. The mapping results are compared to the AHRI 10-coefficient polynomial and another proposed correlation.