Fuel Mass Flow Rate Research Articles

Effects of oxygen depletion on soot production, emission and radiative heat transfer in opposed-flow flame spreading over insulated wire in microgravity

The main objective of this article is to investigate experimentally and numerically the effects of reduced-oxygen contents on the soot production and emission from solid fuels in microgravity, which constitute an important issue in terms of fire safety for manned space missions. Due to its convenience for the implementation of soot-related optical diagnostics, the configuration of a flame spreading in an opposed flow over thin nickel chromium (NiCr) wires coated by low density PolyEthylene (LDPE) is considered. Experiments are conducted at a pressure of 101.3 kPa and an oxidizer velocity of 150 mm/s. The oxygen mole fraction in the oxidizer, XO2, is varied from 18% to 21% by nitrogen dilution of air. The modeling strategy lies on a surrogate fuel to mimic the combustion of LDPE by preserving its stoichiometry and the laminar smoke-point (LSP) flame height. The numerical model considers a detailed chemistry, a two-equation soot production model involving laminar smoke point (LSP)-based soot formation rates and oxidation by OH and O2, a radiation model coupling the Full-Spectrum correlated-k method with the finite volume method, and a simple degradation model for LDPE. Based on experimental evidence, the soot formation rate is scaled by the adiabatic flame temperature to account for thermal effects due to variation in XO2. The model reproduces quantitatively the increase in flame size, residence time, and soot volume fraction observed experimentally as XO2 is enhanced as well as the transition from a non-smoking to a smoking flame, which occurs for XO2 between 19% and 20%. The increase in soot volume fraction results of a combined enhancement in both residence time, owing to an increase in the fuel mass flow rate, and soot formation rate due to higher temperature in the soot formation region. The radiant fraction increases significantly with XO2 from about 17% for XO2=18% to about 36% for XO2= 21%. This increase in radiative losses is accompanied by a reduction of the temperature in the soot oxidation region. Therefore, for increasing XO2, the soot oxidation process is governed by a competition between oxygen-enhanced conditions that promote the formation of soot oxidizing species and the increase in radiative losses that dampens their formation. For the present flames, the first mechanism prevails as XO2 increases from 18% to 19% whereas the second dominates as XO2 is further increased, leading to smoking flames as actually observed for XO2=20 and 21%. The radiant fraction at the smoke-point transition and the soot oxidation freezing temperature are in line with those reported at normal gravity. Finally, model results show that, whatever XO2, the contribution of radiation to the heating process is negligible ahead of the pyrolysis front and is largely overcome by surface radiative losses along the pyrolysis region.

Fully Coupled Turbojet Engine Computational Fluid Dynamics Simulations and Cycle Analyses Along the Equilibrium Running Line

Abstract This work presents fully coupled computational fluid dynamics (CFD) simulations and thermodynamic cycle analyses of a small-scale turbojet engine at several conditions along the equilibrium running line. The CFD simulations use a single mesh for the entire engine, from the intake to the exhaust, allowing information to travel in all directions. The CFD simulations are performed along the equilibrium running line by using the iterative Secant method to compute the fuel flow rate required to match the compressor and turbine power. The freestream pressure and temperature and shaft angular speed are the only inputs needed for the CFD simulations. To evaluate the consistency of the CFD results with thermodynamic cycle results, outputs from the CFD simulations are prescribed as inputs to the cycle model. This approach enables on-design and off-design cycle calculations to be performed without requiring turbomachinery performance maps. In contrast, traditional off-design cycle analyses require either scaling, calculating, or measuring compressor and turbine maps with boundary condition assumptions. In addition, the CFD simulations and the cycle analyses are compared with measurements of the turbojet engine. The CFD simulations, thermodynamic cycle analyses, and measurements agree in terms of total temperature and pressure at the diffuser–combustor interface, air and fuel mass flow rate, equivalence ratio, and thrust. The developed methods to perform CFD simulations from the intake to the exhaust of the turbojet engine are expected to be useful for guiding the design and development of future small-scale gas turbine engines.

On the quality of micromixing in an oxy-fuel micromixer burner for gas turbine applications: A numerical study

The study examines numerically the non-reacting flow and mixing characteristics inside a single tube of a micromixer burner for potential zero-emission premixed oxy-fuel combustion applications, such as gas turbines. The aim is to investigate how the geometrical parameters can affect the mixing quality in an oxy-fuel reactant mixture consisting of CH4, O2, and CO2. The ranges of design parameters are fuel inlet diameter (from 0.2 to 1.0 mm), number of fuel holes (4 and 6), and tube length (from 5D to 15D). It was found that the mixing quality is significantly improved by increasing the tube length. The results also showed that mixing quality is not directly dependent on fuel hole size but on the ratio of main flow to jet flow momenta. At fixed total fuel mass flow rate, the mixing quality depreciates when the number of fuel holes is increased from four to six for all hole diameters, except for the smallest one of 0.2 mm. The peak mixing quality was achieved with fuel hole diameters of 0.25 mm and 0.2 mm for the micromixer tubes with four and six inlet holes, respectively. The results showed that micromixers can achieve high mixing quality at a reasonable burner height.

An analytical computation of aircraft’s longitudinal trimmed conditions considering its fuel mass flow rate

The aim of this article is to give simple expressions of aircraft’s longitudinal trimmed conditions taking into account the instantaneous fuel mass flow rate, i.e. the variation of total mass. The computation of aircraft trim points is not a new problem. Nevertheless, current analytical computations are classically performed with a constant total weight of the aircraft, hence assuming that the rate of decrease of the weight due to the fuel mass flow rate has insignificant effects on the results. Thus, the goal of this study has been to assess the effect of weight variation on aircraft trimmed condition and to compute correctly “extended trimmed conditions” defined as the equilibrated conditions in flight considering the weight decrease of the aircraft. It has been demonstrated that the weight variation must have an ad-hoc form to lead to extended trimmed conditions. Moreover, extended trimmed conditions do not correspond to a perfect level flight as it is the case at constant weight, but must present a slightly positive flight path angle leading to a regular increase in altitude. And the corrected longitudinal commands including throttle and elevator positions at a given airspeed and altitude have been computed for extended trimmed conditions and compared to the basic case at constant weight. Finally, all the analytical expressions given in this article have been verified through a numerical simulation performed in the case of a twin-engine aircraft representative of the Airbus wide-body family.

Restitution methodology for space and time dependent solid-fuel port diameter evolution in hybrid rocket engines

A post-processing tool for experimental data is developed to rebuild the instantaneous and local distributions of the fuel port diameter and the fuel regression rate throughout the port conduct during a firing test. The main objective is to use the developed methodology to be able, at a given instant during the firing test, to simulate a hybrid rocket engine configuration and to validate the related numerical modeling. The methodology is based on the coupling between the instantaneous fuel mass flow rate obtained by a ballistic reconstruction technique and the port diameter measurement throughout the port conduct after the firing test. The ballistic reconstruction method is adapted and applied to an experimental hybrid rocket, using hydrogen peroxide/high density polyethlylene propellants, with a catalytic injector (HYCAT). Firstly, a set of representative firing tests is selected from the HYCAT hybrid rocket engine testing campaign. Secondly, an analytical approach leads to instantaneous evolutions of the fuel port diameter and the fuel regression rate profiles throughout the fuel port conduct. The rebuilt profiles of the instantaneous port diameter show the ability of the methodology to restore the space and time distribution of the fuel port diameter. Nevertheless, the fuel regression rate distributions show some limitations of the methodology even though the average is coherent with the ballistic reconstruction trends.

Energy and Exergy Analysis and Optimization of Turbofan Engine-TF30-P414

The turbofan engines are one of the constitutes significant components of the aero engines. In this study, the thermodynamic modeling of the TF30-P414 turbofan engine is developed and validated with reference values. The aims of this research are to determine the effect of the changes in the thrust, fuel mass flow rate, and thermal efficiency with changes of the flight-altitude (H) and the flight-Mach number (Ma). Then, the changing of the exergy efficiency and exergy destruction rate were investigated.The results show that between the different components of the engine in different flight circumstances, the highest exergy destruction occurred in the combustion chamber and the lowest exergy destruction occurred in the nozzle. Also, optimization with the objective function of finding optimum flight conditions to find the highest exergetic efficiency in the flight-Mach number of 1.2 to 2.2 and the flight altitude of 10,000 to 15,000 meters.The results of this optimization reported that the maximum exergetic efficiency happened to the conditions of H=11236 meters and Ma=1.944 with an amount of 32.64%.

Development of a novel combined energy plant for multigeneration with hydrogen and ammonia production

In order to meet the energy and fuel needs of societies in a sustainable way and hence preserve the environment, there is a strong need for clean, efficient and low-emission energy systems. In this regard, it is aimed to generate cleaner energy outputs, such as electricity, hydrogen and ammonia as well as some additional useful commodities by utilizing both methane gas and the waste heat of an integrated unit to the whole system. In this paper, a novel multi-generation plant is proposed to generate power, hydrogen and ammonia as a chemical fuel, drying, freshwater, heating, and cooling. For this reason, the Brayton cycle as prime unit using methane gas is integrated into the s-CO2 power cycle, organic Rankine cycle, PEM electrolyzer, freshwater production unit, cooling cycle and dryer unit. In order then to evaluate the designed integrated multigeneration system, thermodynamic analyses and parametric studies are performed, revealing that the energy and exergy efficiencies of the whole plant are found to be 69.08% and 65.42%. In addition, ammonia and hydrogen production rates have been found to be 0.2462 kg/s and 0.0631 kg/s for the methane fuel mass flow rate of 1.51 kg/s. Also, the effects of the reference temperature, pinch point temperature of superheater, combustion chamber temperature, gas turbine input pressure, and mass flow rate of fuel on numerous parameters and performance of the plant are investigated.

Modeling and analysis of windmilling operation during mode transition of a turbine-based-combined cycle engine

Mode transition control is a critical issue of Turbine-Based-Combined Cycle (TBCC) engines when the primary thrust providers change from gas turbine engines to ramjets/scramjets. During mode transition, windmilling operation is inevitable when the fuel mass flow rate of the turbojet engine is decreasing to zero gradually. Existed research on mode transition control of TBCC engines usually neglect this process or simplify this process to a rapid thrust loss due to lacking a windmilling model. However, the absence of the windmilling model might cause critical problems unconsidered at the control system design stage and increase the risk of mission abortion. This paper provides a method of modeling the windmilling operation of a TBCC engine. Sub-idle compressor component maps are obtained by the interpolation method based on a zero-speed line to consider the characteristics that the total pressure ratio is below one. Friction torque is added in the torque balance relationship to achieve the free windmilling operation state when both the compressor and the turbine provide positive torques. The inlet start/unstart status coupled with the operating point of the turbojet engine is also considered. Results show that this model could reflect the characteristics that the total pressure ratio of the compressor is below one, and it provides a positive torque instead of a negative one when the turbojet engine operates at some sub-idle states. Moreover, inlet unstart would happen at some point when the turbojet engine is shutting down to the free windmilling state, under which the turbojet engine would bring in the flight drag instead of a positive thrust. In the descent mode transition when the turbojet engine is accelerating to be restarted, an inappropriate rotating speed of the inlet splitter could result in a fail inlet restart.

Lattice Boltzmann simulation of low-Reynolds-number cavitating contracting-nozzle flow interacting with a moving valve

Investigating internal-injector cavitating flow dynamics is difficult but important. The interaction of nozzle cavitation with the moving needle valve dictates the fuel mass flow rate and therefore spray combustion performance and emissions. In the present study, a two-dimensional low-Reynolds-number cavitating contracting-nozzle flow interacting with a moving valve is simulated using the lattice Boltzmann (LB) method. The Bhatnagar–Gross–Krook algorithm coupled with the immersed boundary method and an improved pseudo-potential multiphase flow model are employed and further developed based on the open-source LB code PALABOS. The performance of the immersed boundary method is first verified in a case where an oscillating cylinder moves according to a sine function in water. In order to improve the pseudo-potential model on its limitation of the density ratio, so to be used in engineering multiphase flow, the Carnahan–Starling equation of state is incorporated together with the exact difference method force scheme and an upgraded interaction force term. The upgraded pseudo-potential model proves via validations to be effective in improving numerical stability at large density ratios. With a seamless cooperation of the improved Shan–Chen model and the immersed boundary method achieved in PALABOS, cavitation in a contracting nozzle is simulated for a whole cycle of the valve motion. Cavitation dynamics under different fuel mass flow rates is investigated. It is found that cavitation dynamics, including interface conditions, cavitation bubble distributions, and inside-bubble vapor-phase flow fields, is distinctly different when the flow path is widely open and completely shut by the valve.

Simulation and technical-economic-environmental optimization of the General Electric GE90 hydrogen turbofan engine

In this study, The General Electric GE90 turbofan engine is thermodynamically simulated MATLAB in both states of using hydrocarbon fuel and hydrogen fuel at the design point conditions. Subsequently, the genetic algorithm is used to determine the best bypass ratio and the best fan pressure ratio in order to obtain optimal performance, environmental, and economic conditions for hydrogen Turbofan, that have been obtained to be 10.2965 and 1.6111, respectively. In the end, the following are observed at the cruise altitude as a result of a change from the hydrocarbon GE90 turbofan to the optimized hydrogen GE90 turbofan: (i). The net thrust force increases by 16.27%. (ii). The thrust-specific fuel consumption decreases by 65.90%. (iii). The thermal efficiency increases by 2.65%. (iv). The propulsive efficiency remains almost unchanged with a mere decrease of 0.2% and provides adequate propulsive conditions. (v). The overall efficiency increases by 2.5%. (vi). The mass flow rate of the fuel decreases by 60.29%. (vii). The total emission of NOx reduces by 68.25% per a specified generated thrust and consumed fuel mass flow rate throughout the cruise phase of the flight cycle. Furthermore, the following are observed at the cruise altitude as a result of a change from the hydrogen GE90 turbofan to the optimized hydrogen GE90 turbofan: (i). The emission of nitrogen oxide for every kilogram of burnt fuel decreases by 3.94%. (ii). The total emission of NOx per a specified mass flow rate of consumed fuel and generated thrust throughout the cruise phase reduces by 16.67%.

Structures of Ethanol Spray Flames under CO2 Dilution of the Oxidizer in the Counterflow Configuration under MILD Combustion Conditions

Structures of both gaseous and liquid ethanol flames in different oxidizing gas environments in the axisymmetric counterflow configuration at atmospheric pressure are studied. Initially, ethanol/air gas flames are considered where pure ethanol is directed against air at initial temperatures of 400 K, and N2 is successively removed to obtain structures of ethanol/O2 gas flames. Furthermore, the addition of CO2 to the oxidizer side is carried out. Then, an ethanol spray is carried by air and directed against an air stream, and the same procedure is performed as described for the gas flames. The gas strain rate at the fuel side of the configuration is increased from low values of 55/s up to extinction, and the initial droplet diameter is varied. For the combustion of gaseous ethanol in air and in pure oxygen, the nitrogen removal results in an increase in the maximum flame temperature from 2010 K to 2920 K at a gas strain rate of 55/s on the fuel side of the configuration, and the extinction strain rates are 630/s and 26,000/s, respectively. It is confirmed that ethanol spray flames in air show two reaction zones at low strain whereas the lean ethanol spray flames in pure oxygen exhibit a single reaction zone in all situations studied. For increased liquid fuel mass flow rate to a global equivalence ratio of unity, two reaction zones are retrieved. An analysis regarding the addition of CO2 in both the ethanol/oxygen gas and spray flames is also discussed and is found that CO2 dilution of the carrier gas the spray is much more efficient than diluting the opposed gas stream in the counterflow configuration for the generation of MILD combustion conditions in oxy-fuel flames.

Experimental Study of Direct Water Injection Effect on NOx Reduction from The Gas Fuel

Direct Water Injection (DWI) is commonly used in many nitrogen oxides (NOx) emissions control applications due to its effect to reduce the adiabatic flame temperature. In this paper an experimental test rig is designed to study the effect of water injection spray inside a simulated gas turbine combustor from the gas fuel. The practical work introduced by the chemical reaction methodology followed by the experiment which was presented and discussed carefully. Results are obtained in term of the exhaust gas temperature and different injection parameters including position, direction and fuel mass flow rate on the nitrogen oxide emission value in PPM (Parts per Million) at different conditions. The results showed that the best water injection effect was obtained at 45° degree inside the primary air zone. Injection location has a major effect on the NOx reduction as the best injected location is the Primary air zone compared with the direct fuel nozzle tip due to the increase of the water droplets residence time inside the combustor and perform a vortex that will affect the reduction of exhaust gas temperature and NOx emission respectively. The huge impact was observed at LPG (Liquefied Petroleum gas) flowrate 2.7L/min and water to fuel ratio about 0.4 as the NOx value was decreased about 73% from almost 381 PPM to 73 PPM. The chemical reaction arrangement order methodology presented good agreement with the experimental results at different fuel flow rate and equivalence ratio. The chemical Reaction equations were implemented to calculate the different adiabatic flame temperatures which is experimentally known as the exhaust gas temperature and impacted directly the NOx emission results.

Comparison and analysis of the effects of spark timing and lambda on a high-speed spark ignition engine fuelled with n-butanol/gasoline blends

In this study, a four-stroke, high-speed spark ignition (SI) engine was conducted to reflect the effects of n-butanol blend ratio, spark timing and lambda. The experiments were conducted with four types of fuels including B0 (0 vol% n-butanol and 100 vol% gasoline), B10, B20 and B30, two operation conditions including the engine speed of 4000 r/min and 8000 r/min, the throttle position of 35% and 45%, respectively; with the spark timing range from 25° to 48° before top dead center (BTDC), and the lambda range from 0.85 to 1.5. The results demonstrate that with the increasing of n-butanol blend ratio, the fuel mass flow rate is increased when the lambda is fixed. The output power, brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) increase with increasing n-butanol ratio. The addition of n-butanol to gasoline can decrease nitric oxide (NO) emissions significantly but increase carbon monoxide (CO) emissions slightly. The lambda relative to the maximum BTE, the minimum BSFC and the maximum combustion efficiency become larger with the content of n-butanol increase. The data of engine parameters were normalized, and a calculation formula of weighted analysis for the engine performance was presented. With the n-butanol blend ratio increasing, the test engine has a better performance. Considering the emissions, the spark timing of the highest weighted normalized score (WNS) is retarded relative to maximum brake power (MBP) timing, and the lambda of the highest WNS becomes larger.

Soot Formation With Light Extinction and Grayscale Extraction Methods Applied to Ethanol-Gasoline Blends Laminar Flame

AbstractIn this paper, the two-dimensional parallel light extinction method was carried out to study the soot formation in laminar diffusion flames of four different ethanol-gasoline blends, of which ethanol volume fractions ranging from 0% up to 100% (E0, E20, E80, and E100). The flame images were processed synthetically via matlab to accurately calculate the flame height. In addition, the flame structure was redefined as three zones to observe the soot formation. The results indicate that the flame height changes with the variation of gas volume flowrate and fuel mass flowrate during the experiment. In terms of soot formation, as the volume fraction of ethanol increases, the proportion of soot forming zone decreases, while the area of blue flame zone grows. Simultaneously, the transition zone accounts for about 21% of the total flame area, which has no significant change with the increase of ethanol volume fraction.

Combust-o-Acoustics: Energy Transition and Implications

Acoustics is an integral constituent of most of combustion processes. While combustion advancements have revolutionized human life, acoustics induced combustion also represents a dominant form of instability. Thermo-acoustics, as an intense area of scientific research, covers a wide range of applications viz., industrial (electricity generation), transportation (jet and space propulsion), engineering (system efficiency and operations) and scientific research. The presence of such inept working systems with instability is likely to result in significant loss of resources, infrastructure, property, mankind, nature, with huge amount of money being spent on research activities. Appreciable work has been done before however; the heterogeneous nature of the problem has prevented comprehensive understanding. Thus, the need to investigate and characterize the acoustics imbibed combustion processes to suggest better combustion alternatives/enhance effectiveness and to minimize the resultant hazards. Present work, attempts to resolve the low effectiveness of combustion systems by classification of thermal acoustics and related major hazards. A simple experimental setup was upraised comprising of butane cylinder with nozzle and systematic experimentation was carried out to explore the phenomenon of energy transition in combustion with acoustics. The exploration was carried out for varying fuel mass flow rates, L/D ratios, material of tubes, interspace distance and counter acoustics impingement. The results were observed with acoustics measurement, along with type and structure of flames. The work is primarily motivated by the need to have technologically enhanced combustion understanding and for fire safety applications. The results exhibit that presence of external enclosures have significant effect on thermoacoustics and with coupled redundancy effect, a special pattern noted was both the controlling parameters results in reduction in maximum acoustics rise and increase in maximum drop levels this contributing significantly to enhancement of system efficiency. The results can be of pertinent significance for the testing, validation of conventional systems and designing of the efficient and safer futuristic propulsive systems.

Exergy and NOx Emission-Based Ecological Performance Analysis of the Scimitar Engine

Abstract Scimitar engine is a hypersonic hybrid engine designed to propel the LAPCAT A2 aircraft. In this study, a novel exergy and NOx emission-based ecological performance analysis of the engine is performed. For this purpose, first, a component-based exergy analysis for the cruise phase of the Scimitar engine in air-turborocket mode is performed and the exergy destruction rates of engine components are determined at Mach 5 by the thermodynamic model developed. Then, a novel objective function, the coefficient of emission-based ecological performance (CEEP) is defined as “the propulsive power produced per unit environmentally harmful exhaust gas emission rate,” which can be utilized to assess the ecological impact of any jet engine. Finally, the impacts of cruise speed, altitude, and air and fuel mass flow rates on the exergetic and NOx emission-based ecological performance of the engine are investigated by the aid of the newly defined CEEP, together with the exergy efficiency and the coefficient of ecological performance. It is found that the combustion chamber is responsible for 57.36% of the overall exergy destruction rate of 123.80 MW at the cruise conditions, and CEEP relatively increases by 13.8% when the hydrogen fuel consumption rate is increased from 3.96 kg/s to 4.17 kg/s. Increasing the cruise speed from Ma = 4.88 to Ma = 5.2 and decreasing the altitude from 25 km to 23 km cause a relative degradation of 12.75% in CEEP.

Reconstructed Ballistic Data Versus Wax Regression-Rate Intrusive Measurement in a Hybrid Rocket

Burning tests of a laboratory-scale hybrid rocket engine were carried out with gaseous oxygen and a microcrystalline-wax-based fuel to look into the feasibility of using an intrusive resistor-based sensor for measuring the fuel regression rate. This initial screening was driven by the need for real-time control of the oxidizer-to-fuel ratio in altering-intensity swirling-flow-type hybrid rocket engines aiming at performance optimization. A traditional ballistic reconstruction technique was critically revised in order to build up a framework for comparison with the measured data; with the measured aft-chamber pressure and oxygen mass flow rate time histories, the fuel regression rate and port diameter were reconstructed over the firing by estimating the combustion efficiency with the constraint that calculated and measured fuel mass consumed are equal. This technique invariably suffers from the issue of presenting multiple solutions for the fuel mass flow rate in the proximity of the optimum mixture ratio, for which a novel variable-efficiency approach is proposed. Reconstructed data show that regression rate is nearly constant in each firing, yielding dependence upon the port diameter other than the mass flux. Resistor-sensor raw data displayed large deviation from the ballistic results for the slower burning rate of the sensor support. A detailed analysis is presented.

Performance optimization of an open simple-cycle gas turbine combined cooling, heating and power plant driven by basic oxygen furnace gas in China's steelmaking plants

Based on production data of some steelmaking plants in China and applying finite-time thermodynamics, this paper establishes a physical model of simple open gas turbine combined cooling, heating and power plant driven by basic oxygen furnace gas. Thermal process of each component is analyzed. Useful energy output rate and first law efficiency are considered as optimization objectives. Cases with or without constraints of fuel mass flow rate and overall size are investigated. In the case of without constraints, compressor inlet pressure drop (i.e. air mass flow rate) and pressure ratio are respectively optimized, and the maximum useful energy output rate is obtained. In the case of with constraints, it is found that the first law efficiency also exists maximum with respect to compressor inlet pressure drop and pressure ratio, the optimal flow area allocations among the components are obtained. The results show that maximum useful energy output rate and first law efficiency increase with heat source temperature, efficiencies of compressors and turbine, component flow area and cooling temperature, while decrease with heating temperature. Effects of energy and exergy saving, CO2 emission reduction and cost saving are analyzed compared with conventional separate generation plants, and partial model is validated.

Experimental study of injection characteristics under diesel’s sub/trans/supercritical conditions with various nozzle diameters and injection pressures

The supercritical fluid combustion technology was expected to enhance fuel-gas mixing and heat exchange management both in the application of automobile and marine engines. Considering the challenge and shortage of relevant researches, the transcritical injection experiment is conducted in a constant volume chamber to obtain the detailed knowledge about the effect of key factors, such as nozzle diameters, injection pressures and critical conditions, on injection and critical characteristics. A total of 216 experimental cases were operated to analyze the effect of three different injector nozzle diameters (100, 300, 350 μm), four injection pressures (60, 100, 140, 180 MPa) and nine ambient conditions, with two optical techniques (backlight illumination, schlieren imaging). The fuel injection characteristics are studied, where the spray structure is recorded, and the liquid length, R-parameter, spray volumes, cone angles as well as relevant empirical correlations are calculated to investigate the axial and radial dispersion. The results show that different critical conditions dominate the fuel spray to behave as different structures. The 350 μm nozzle produces a higher fuel mass flow rate than other nozzles to expand the side periphery region, while the 100 μm nozzle is prone to be dominated by ambient gas entrainment to strength the puffing process. The injection pressure has an insignificant effect on the liquid length, liquid volume and spray cone angles, but an increasing influence on the jet volume with higher pressures. Under supercritical condition, higher injection pressure can promote the fuel-gas mixing and hot gas entrainment in the downstream region.

Single hole direct injector simulation validation and parametric sensitivity study

This paper presents a parametric study conducted on electronically controlled solenoid direct fuel injector running on compressed natural gas. The purpose of the study is to identify the influential injector parameters on the output fuel mass flow rate. These injector parameters are to be optimize in the next stage of the study. The parametric study is conducted using zero-dimensional, first principle injector model which consist of electro-magnetic, mechanical and flow sub-models. In current study, seven (six input and one output) selected parameters have been analysed which are the injection pressure, injection duration, nozzle diameter, armature mass, the input voltage, spring constant and the output mass flow rate. Each input parameters are varied in the prescribed range based on the literature. Based on the study, the most influential parameters (in rank) are the nozzle diameter, the armature mass and the injection duration. The input voltage, the injection pressure and the spring constant were found to have no impact on the injector mass flow rate based on the values of parameter’s sensitivities. Based on the results, the potential parameters to be optimized are identified.