Injection Mass Flow Rate Research Articles

The Application of Suction and Blowing in Performance Improvement of Transonic Airfoils with Shock Control Bump

Shock Control Bump (SCB) reduces the wave drag in transonic flight. In high Mach transonic flows, the boundary layer separation downstream the bump, induced by the shock wave, results in the poor performance of the SCB. To control the boundary layer separation and to reduce the wave drag for two transonic airfoils, RAE-2822 and NACA-64A010, we investigate the application of two conventional flow control methods, i.e. suction and blowing, to be added to the SCB. An adjoint gradient based optimization algorithm is used to find the optimum shape and location of SCB. The performance of both hybrid suction/SCB (HSS) and hybrid blowing/SCB (HBS) is a function of the sucked or injected mass flow rate, and their position. A parametric study is performed to find the near optimum values of the aerodynamic coefficients and efficiency. A RANS solver is validated and used for this flow analysis. This study shows that both HSS and HBS methods considerably improve the aerodynamic efficiency (L/D), while the HBS method is more effective in control of the shock wave/boundary layer interaction. Using HSS method, the aerodynamic efficiencies of these two airfoils are increased by, respectively, 8.6% and 3.9%, respect to the airfoils with optimized bumps. For HBS configuration, improvements are respectively 13.5% and 9.0%. The best non-dimensional mass flow rate for suction is found to be around 0.003 for both airfoils, and for blowing this is about 0.0025 for RAE-2822 airfoil and about 0.002 for NACA-64A010. The best location for suction and blowing are found to be, respectively, right before and after the SCB.

Effects of Non-axisymmetric Casing Grooves Combined with Airflow Injection on Stability Enhancement of an Axial Compressor

AbstractThis paper presents a performance evaluation of non-axisymmetric casing grooves combined with airflow injection in a transonic axial compressor with NASA Rotor 37, using three-dimensional Reynolds-averaged Navier-Stokes equations with the k-ε turbulence model. An axisymmetric casing groove was divided circumferentially into 36 non-axisymmetric grooves. The numerical results for adiabatic efficiency and total pressure ratio were validated with experimental data. A parametric study for stall margin, stable range extension, peak adiabatic efficiency, and total pressure ratio at peak adiabatic efficiency of the compressor was performed using five parameters: the front and rear lengths, the height of the casing groove, the injection mass flow rate, and the injection angle. The non-axisymmetric casing grooves combined with injection improve greatly the stall margin and stable range extension of the transonic axial compressor, but reduce only slightly the peak adiabatic efficiency in all cases, compared to the results for a smooth casing.

Application of Killer Whale Algorithm in ASP EOR Optimization

Enhanced Oil Recovery (EOR) is utilized to increase oil production after primary and secondary methods. EOR is classified into three main categories i.e. thermal recovery, chemical flooding and miscible flooding. Alkaline Surfactant Polymer (ASP) EOR is a method of chemical flooding in which the increase of oil recovery is ranging from 19% to 34% of original oil in place (OOIP). In order to obtain optimal results of ASP EOR needs to consider several parameters i.e. the concentration of ASP, ASP material procurement costs, the injection pressure and mass flow rate of injection. Beggs-Brill method is used to model the pressure drop in the injection well and production well. The mean error of Beggs-Brill method to PIPESIM simulation result is 0.5076%. Meanwhile the modelling of reservoir pressure conducted using Darcy equation shows that the mean error of Darcy equation model to COMSOL Multiphysics simulation result is 3.378×10-5%. The optimization results using Killer Whale Algorithm (KWA) exhibits the net profit of ASP EOR increases up to 87.72% or net profit can be optimized from 9586.40 USD/day to 17995.19 USD/day.

A Three-Dimensional Coupled Thermal-Hydro Model for Enhanced Geothermal Systems

A three-dimensional numerical model of coupled fluid flow and heat transfer in EGS system is investigated. The model considers a single uniform fracture surrounded by a three dimensional low permeable rock matrix. The flow is imposed on a fracture plane, consisting of a doublet system. The primary objectives of this paper are to analyze the effects of injection temperature and mass flow rates on heat extraction performances. The study results showed that for lower injection temperature heat extraction rates from the reservoir are higher. In case of higher injection mass flow rate, energy output increased significantly. However, after thermal breakthrough the energy output drops are seen faster in comparison of lower mass injection case. The faster energy drop with the time are result of the slower heat conduction inside the low permeable rock matrix perpendicular to the fracture. The present model neglected the fracture aperture evolution even though transmissivity reduction is observed. The transmissivity reduction is the results of flow resistance. The flow resistance inside the fracture is increased due to the non-laminar flow and cooling. The combined effect leads to rise the flow impendence of the reservoir. These effects are more for the higher mass at the lower injection temperature.

New characterization methodology for vapor-injection scroll compressors

This paper presents a characterization methodology for vapor-injection scroll compressors (SCVI). An SCVI was characterized in a modified calorimetric test bench, which is able to control the intermediate pressure and the injection superheat independently. Based on the characterization results, the injection mass flow rate was correlated with the intermediate pressure through a linear expression, and a modified AHRI polynomial was proposed to estimate the compressor power input. The correlations were used in a simple model to predict the intermediate conditions of the SCVI installed in a heat pump prototype with an economizer. The deviations obtained for the evaporator mass flow rate, injection mass flow rate, intermediate pressure, and compressor power input were lower than 5% in all cases. The proposed methodology allows evaluating SCVI in a wide range of operating conditions, being only dependent on compressor characteristics and totally independent of the system in which it is installed.

Numerical study on the optimal design of injection-hole geometries of a twin rotary compressor in a liquid injection heat pump

In a liquid injection heat pump, it is very essential to control the compressor discharge temperature without wet-compression problems at extreme outdoor conditions. The objective of this study was to optimize the injection-hole geometries of a liquid injection heat pump in order to prevent the risk of wet-compression while reducing compressor discharge temperature at overload cooling conditions. In this study, a simulation model for predicting the performance of a liquid injection heat pump was developed and validated. The optimum injection-hole geometries were determined to obtain the maximum multiplication ratio, which led to a lower instant injection mass flow rate in terms of R- and θ-directional positions. In addition, the injection-hole diameter was minimized to prevent wet-compression while obtaining the target injection mass flow rate. The discharge temperature of the optimized compressor was decreased by 9.2°C over the baseline compressor while maintaining the same risk for wet-compression at the overload cooling test condition.

Utilization of ANN and ANFIS models to predict variable speed scroll compressor with vapor injection

The use of numerical models and experimental setups to evaluate various parameters of variable speed scroll compressors with vapor injection (VSSCV) seems to be time-consuming, expensive, and fairly complex for engineers; hence development of an intelligent predictive model that is quick, simple to use, robust, and accurate in this field of study is worthwhile and highly necessary for work. In this regard, the paper presents two intelligent modeling approaches using an Artificial Neural Network (ANN) and an Adaptive Neuro Fuzzy Inference System (ANFIS) for the first time to accurately calculate the suction, discharge and injection mass flow rates (m˙SUC, m˙DIS, and m˙INJ), compressor electrical power (W˙COMP), and refrigerant temperature at compressor discharge (TDIS) for a VSSCV. The comparison between the developed models via statistical criteria showed the higher precision of applying the ANFIS approach as a suitable model for the prediction of VSSCV parameters compared to the ANN one.

Analysis on slot-type casing treatment injection flow in an axial transonic compressor

The purpose of this work is to understand the properties of the injection flow through slots opening surfaces with steady and unsteady simulations. The feasibility of evaluating slot effectiveness by steady results is demonstrated. Transient features of injection flow are detailed investigated. Numerical investigations are carried out in a 1.5 axial transonic compressor stage at a specified rotating speed with seven kinds of slot-type casing treatments. Comparisons between steady/unsteady results show that differences of overall performance and injection mass flow rate are dependent on simulation methods, rather than slot configurations. Thus, correlation analysis by steady results of seven slot configurations is considered valid and reveals strong linear correlation between injection mass flow and stall margin improvements/efficiency drops. Therefore, it is practical to evaluate the effectiveness of a specific slot configuration in this compressor with steady results by calculating injection mass flow rate. Afterwards, unsteady simulations are performed with a specific configuration of arc-curve skewed slots. It is clarified that the dividing locations between suction/injection regions moves along the axial direction based on the relative rotor/slots location. Exchanging flow through slots opening surfaces displays periodic variations over time. The variation cycle for one single slot equals blade passing period T. For summation of mass flow through all slots, the cycle equals to T divided by slots number in one passage. The net flow rate through all opening surfaces is always less than zero during a blading passing period, i.e. injection mass flow rate is larger than suction flow all the time.

Large eddy simulations of partially premixed ethanol dilute spray flames using the flamelet generated manifold model

The paper presents Large Eddy Simulations (LESs) for the Sydney ethanol piloted turbulent dilute spray flames ETF2, ETF6, and ETF7. The Flamelet Generated Manifold (FGM) approach is employed to predict mixing and burning of the evaporating fuel droplets. A methodology to match the experimental inflow spray profiles is presented. The spray statistical time-averaged results show reasonable agreement with mean and RMS data. The Particle Size Distribution (PSD) shows a good match downstream of the nozzle exit and up to x/D = 10. At x/D = 20 and 30 the PSD is under-predicted for droplets with mean diameter D10 > 20μm and over-predicted for the smaller size droplets. The simulations reasonably predict the reported mean flame structure and length. The effect of increasing the carrier velocity (ETF2–ETF7) or decreasing the liquid fuel injection mass flow rate (ETF2–ETF6) is found to result in a leaner, shorter flame and stronger spray–flow interactions. Higher tendency to local extinction is observed for ETF7 which is closer to blow-off compared to ETF2 and has higher scalar dissipation rates, higher range of Stokes number, and faster droplet response. The possible sources of LES-FGM deviations from the measurements are discussed and highlighted. In particular, the spray time-averaged statistical error contribution is quantified and the impact of the inflow uncertainty is studied. Sensitivity analysis to the pre-vaporized nozzle fuel mass fraction show that such small inflow perturbations (by ± 2% for the ETF2 flame) have a strong impact on the flame structure, and the droplets’ dynamics. Conditional scatter plots show that the flame exhibits wide range of mixing conditions and bimodal mixing lines particularly at upstream locations (x/D < 20), where the injected droplets are still penetrating the centerline. This is relaxed further downstream as droplets gradually evaporate and burn in a diffusion like mode.

Operational strategy of pre-cooling process of CO2 storage tank in CCS ship transportation using model-based optimization

CO2 storage tanks must be cooled before loading cryogenic liquid CO2 to prevent physical and thermal damage to the tank wall. This pre-cooling process gasifies a fraction of the liquid CO2 cargo and injects the resulting gas into the storage tank until the tank reaches the target temperature of 243.15K and pressure of 500kPa. In this paper, we propose a model predictive control approach for optimizing the injection flowrate of CO2 gas to reduce the loss of liquid CO2 cargo and CO2 capturing and compression cost. First, the process is mathematically formulated into a nonlinear multi-input-multi-output (MIMO) gas-phase system in which the injection mass flowrate and the outlet purging mass flowrate of CO2 gas act as control inputs. Then, a finite-horizon linearized model predictive control (MPC) scheme is designed to make the tank system reach the target state within 24h with a maximum cooling rate of −10K/h. A terminal penalty is suboptimally approximated by solving a modified discrete Lyapunov stability condition. The performance of the proposed method in optimizing the pre-cooling process is illustrated with example case studies based on the SIMULINK environment in MATLAB R2015a.

Active Insulation Technique Applied to the Experimental Analysis of a Thermodynamic Control System for Cryogenic Propellant Storage

A technological barrier for long-duration space missions using cryogenic propulsion is the control of the propellant tank self-pressurization (SP). Since the cryogenic propellant submitted to undesired heat load tends to vaporize, the resulting pressure rise must be controlled to prevent storage failure. The thermodynamic vent system (TVS) is one of the possible control strategies. A TVS system has been investigated using on-ground experiments with simulant fluid. Previous experiments performed in the literature have reported difficulties to manage the thermal boundary condition at the tank wall; spurious thermal effects induced by the tank environment spoiled the tank power balance accuracy. This paper proposes to improve the experimental tank power balance, thanks to the combined use of an active insulation technique, a double envelope thermalized by a water loop which yields a net zero heat flux boundary condition and an electrical heating coil delivering a thermal power Pc∈[0−360] W, which accurately sets the tank thermal input. The simulant fluid is the NOVEC1230 fluoroketone, allowing experiments at room temperature T ∈ [40–60] °C. Various SP and TVS experiments are performed with this new and improved apparatus. The proposed active tank insulation technique yields quasi-adiabatic wall condition for all experiments. For TVS control at a given injection temperature, the final equilibrium state depends on heat load and the injection mass flow rate. The cooling dynamics is determined by the tank filling and the injection mass flow rate but does not depend on the heat load Pc.

Development of High Efficiency and Low Emission Low Temperature Combustion Diesel Engine with Direct EGR Injection

Focus on energy and environmental sustainability policy has put automotive research & development directed to developing high efficiency and low pollutant power train. Diffused flame controlled diesel combustion has reach its limitation and has driven R&D to explore other modes of combustions. Known effective mode of combustion to reduce emission are Low temperature combustion (LTC) and homogeneous charge combustion ignition by suppressing Nitrogen Oxide(NOx) and Particulate Matter (PM) formation. The key control to meet this requirement are chemical composition and distribution of fuel and gas during a combustion process. Most research to accomplish this goal is done by manipulating injected mass flow rate and varying indirect EGR through intake manifold. This research paper shows viable alternative direct combustion control via co-axial direct EGR injection with fuel injection process. A simulation study with OpenFOAM is conducted by varying EGR injection velocity and direct EGR injector diameter performed with under two conditions with non-combustion and combustion. n-heptane (C7H16) is used as surrogate fuel together with 57 species 290 semi-detailed chemical kinetic model developed by Chalmers University is used for combustion simulation. Simulation result indicates viability of co-axial EGR injection as a method for low temperature combustion control.

Experimental study of combustion behavior during continuous hydrogen injection with an operating igniter

Deliberate hydrogen ignition systems have been widely installed in many water cooled nuclear power plants to mitigate hydrogen risk in a loss-of-coolant accident. Experimental studies were performed at a large scale facility to simulate a post-accident containment scenario, where hydrogen is released into a volume (not closed) with an energized igniter. The test chamber had a volume of 60m3. The test parameters included hydrogen injection mass flow rate, injection elevation, igniter elevation, and level of turbulence in the chamber. Several dynamic combustion behaviors were observed. Under certain conditions, slow burning occurred periodically or locally without significant pressurization, and the hydrogen concentration could be maintained near the lean hydrogen flammability limit or a steady hydrogen distribution profile could be formed with a maximum hydrogen concentration less than 9vol.%. Under other conditions, a global fast burn or a burn moving along the hydrogen dispersion pathway was observed and was followed by an immediate initiation of a standing flame. The study provided a better understanding of the dynamic combustion behavior induced by a deliberate igniter during a continuous hydrogen release. The data can be used for validation of combustion models used for hydrogen safety analysis.

Supersonic Boundary-Layer Combustion via Multiporthole Injector Arrays

The flowfield characteristics of boundary-layer combustion using a multiporthole injector array were investigated in a numerical study. Hydrogen fuel was injected at four different mass flow rates and two streamwise porthole spacings within the boundary layer on a flat plate through an array of small portholes in a Mach 4.5 crossflow. The jet-to-jet spacings used were those identified in a previous investigation of film cooling as yielding the greatest drag reduction and mixing efficiency, respectively. The effect of injectant mass flow rate and streamwise jet-to-jet spacing was investigated using the three-dimensional Reynolds-averaged Navier–Stokes equations with Menter’s shear stress transport turbulence model and a 13-species, 33-reaction hydrogen–air chemistry model. At high injection mass flow rates, ignition occurred at the injection point; however, the ignition length increased as the mass flow rate was decreased. At the lowest injection rate, ignition did not occur within the investigated domain. Where combustion occurred, significant thickening of the boundary layer and high local heating was found near the ignition point. Total viscous drag reductions of up to 78% over a plate length of 0.5 m were achieved. The mechanism of drag reduction was found to be associated with a reduction in near-wall Reynolds stresses. Even with the presence of combustion in the boundary layer, significant wall heat transfer rate reductions were also found in all cases compared with no injection.

Development of an empirical model of a variable speed vapor injection compressor used in a Modelica-based dynamic model of a residential air source heat pump

This paper presents a steady-state model of a variable speed vapour injection scroll compressor. Two compressors were investigated. The developed empirical model is based on five dimensionless polynomials that were fitted using experimental data from a 2.7kW scroll compressor. A second set of data was used to show the prediction of the presented model for an other device which exhibits a different swept volume. In both cases, the suction and injection mass flow rate were respectively predicted with a coefficient of determination equal to 99.9 and 94.3% and for the consumed power, 98.4% and 95.6%. A Modelica based dynamic model is then presented. The steady-state validation of the main components models is performed. Finally the control of the cycle using two PID controllers is presented and commented.

Optimization of the Efficiency of Stall Control Using Air Injection for Centrifugal Compressors

Numerical investigation of the optimization of the stall control efficiency for a high speed centrifugal compressor using air injection is presented. External air was injected close to the diffuser entrance at the shroud surface of the vaneless region. Injection was applied with mass flow rates of 0.7%, 1%, and 1.5% of the design inlet mass flow rate with six different angles of 0 deg, 10 deg, 20 deg, 30 deg, 40 deg, and 180 deg measured from the positive tangential direction at the vaneless region. Detailed comparisons were made between the case without using air injection and the different air injection cases by comparing velocity, pressure, and force fluctuations with time. Results showed that as the injection mass flow rate increases, the number of diffuser passages with reversed flow decreases for all cases of injection except for the case of reverse tangent injection. Results indicated that using angle of injection of 30 deg minimized the stall area and provided the least force fluctuations with no reversed flow compared to other injection angles. Finally, it was found that injecting air with mass flow rate of 1.5% of the inlet mass flow rate at an angle of 30 deg resulted in shifting of stall onset to a mass flow rate corresponding to 3.8 kg/s instead of 4 kg/s for a compressor without using air injection control.

EFFECT OF INJECTION HOLE DIAMETER ON OPERATIONAL CONDITIONS OF COMMON-RAIL FUEL-INJECTION SYSTEM FOR PORT-INJECTION HYDROGEN-FUELED ENGINE

Modeling of the hydrogen-fueled engine injection system is a very important tool that can be used to explain or predict the effect of advanced injection strategies on combustion and emissions. This work proposes a common-rail (CR) injection system for a four-stroke four-cylinder hydrogen-fueled engine with a port-injection feeding system. A numerical one-dimensional gas dynamic model was developed considering a single injection event for each injector per cycle. For this purpose, one-dimensional flow equations in conservation form are used to simulate wave propagation phenomena throughout the CR (accumulator). The effect of the CR on the injection-system characteristics has been clarified. These characteristics include: rail pressure, sound velocity, rail mass flow rate, injected mass flow rate and pressure drop across injectors. The interaction effects of operational conditions (engine speed and rail pressure) and geometrical features (injector hole diameter) are illustrated. The required compromise solutions are highlighted. The CR injection system is shown to be a promising enhancement for the port-injection hydrogen-fueled engine.

히트 펌프용 비대칭 스크롤 압축기의 가스 인젝션 포트 설계

For an asymmetric scroll compressor for heat pump application, a numerical simulation was carried out to investigate the effects of injection port design on the compressor`s performance under gas injection. To validate the simulation, the numerical results were compared with experimental results obtained from a scroll compressor with a base injection port design. There was good agreement between simulation and experimental results, with around a 1% difference in the injection mass flow rate when the injection pressure was below for the heating mode. Various injection port angular positions were numerically tested to yield better injection performance. The largest improvement in heating capacity was obtained at angles of and inward from the scroll wrap end angle for low-temperature and standard heating conditions, respectively, while the maximum COP improvement was at and , respectively. A considerable improvement in cooling capacity was also found at the injection port angle of .

Investigation of film cooling on nose cone by a forward facing array of micro-jets in Hypersonic flow

A numerical study has been performed to investigate the film-cooling heat reduction performance of a single jet (diameter 2mm and 0.9mm), and an array forward facing of micro-jets (diameter 300μm each) of the same effective area (corresponding to the respective single jet). Helium and/or Nitrogen are injected as coolant gases from the tip of the nose through an array of micro into a Mach 5.9 counterflow free stream. Parametric studies were conducted on injection total pressure with various diameters by using the Reynolds-averaged Navier–Stokes equations with Menter's Shear Stress Transport turbulence model. Complex jet interactions were found in the injection region with a variety of flow features depending upon the specific configuration. These flow features were found to have subtle effects on the overall system performance. Total heat load reductions of up to 40% over a nose were achieved for micro jet with low Pressure Ratio. Significant wall heat transfer reductions were also found in all cases. The heat transfer rates were strongly influenced by injection mass flow rate, and only moderately affected by the number of micro jets. The maximum heat reduction performance was found in the highest injection total jet pressure (consequently more mass flow rate) with the highest micro array.

Characterisation of acoustic energy content in an experimental combustion chamber with and without external forcing

The influence of injection conditions on rocket engine combustion stability is investigated for a sub-scale combustion chamber with shear coaxial injection elements and the propellant combination hydrogen–oxygen. The experimental results presented are from a series of tests conducted at subcritical and supercritical pressures for oxygen and for both ambient and cryogenic temperature hydrogen. The stability of the system is characterised by the root mean squared amplitude of dynamic combustion chamber pressure in the upper part of the acoustic spectrum relevant for high frequency combustion instabilities. Results are presented for both unforced and externally forced combustion chamber configurations. It was found that, for both the unforced and externally forced configurations, the injection velocity had the strongest influence on combustion chamber stability. Through the use of multivariate linear regression the influence of hydrogen injection temperature and hydrogen injection mass flow rate were best able to explain the variance in stability for dependence on injection velocity ratio. For unforced tests turbulent jet noise from injection was found to dominate the energy content of the signal. For the externally forced configuration a non-linear regression model was better able to predict the variance, suggesting the influence of non-linear behaviour. The response of the system to variation of injection conditions was found to be small; suggesting that the combustion chamber investigated in the experiment is highly stable.