Influence Of Injection Pressure Research Articles

Analysis of dynamic characteristics and influencing factors of CO2 low-permeability coal reservoir sequestration

ABSTRACT Abandoned coal seams can be an important carrier for CO2 geological storage. Considering the gas seepage-diffusion and physical adsorption coupling characteristics in the process of CO2 adsorption and storage in coal and rock, a two-dimensional model of coupled flow-solidity for geological storage of CO2 in low-permeability reservoir with double voids was established by introducing the Zhang Hongbin model algorithm and adding the Klinkenberg effect and the compression effect of the rock skeleton in coal reservoirs in the controlling equation for rock deformation. The coupled flow-solid model was solved by using the PDE equation of COMSOL Multiphics program, and the simulation results difference between the new model and the traditional model in terms of sequestration dynamics were compared. The dynamic characteristic of reservoir gas pressure, formation stress, permeability and sequestration density in the process of CO2 geologic sequestration and injection were analyzed, and the influences of injection pressure and injection well diameter on the amount of CO2 sequestration were explored. The results show that the new model is more reasonable for calculating reservoir gas pressure and permeability compared with the Palmer-Mansoori model (PM model), and can simulate the free-state seepage movement of CO2 in the fracture system as well as its physical adsorption process compared with the single-heavy pore medium model. With continuous CO2 injection, the maximum sequestration density was raised to a limit value of about 1000 kg/m3 after 1 year. The date of reaching the limit of the sequestration volume was advanced by about 45 d when the positive pressure of the injected gas was increased from 10 kPa to 50 kPa. This model can reproduce the main parameters including, when affecting the effect, and realize the calculation of parameters such as CO2 density reaching the limit value, sealing limit day, sealing limit amount, which can provide a theoretical basis for further deep understanding of CO2 geological sealing law and scientific development of gas injection scheme.

Effect of injection timings and injection pressure on knock mitigation with a compression stroke injection of hydrous ethanol in spark ignition

Direct injection fuel systems provide precise control over the amount of fuel injected and can enable higher compression ratio operation and earlier combustion phasing under knock-limited operation, particularly for fuels with a high cooling potential like hydrous ethanol, a blend of 92% ethanol and 8% water. Moving a portion of the total fuel mass from an intake stroke injection to a compression stroke injection can provide a knock suppression benefit, which can enable more efficient operation. In this work, the influence of injection pressure on this split injection spark ignition strategy is examined. The effect of injection pressure on two intake stroke injections were characterized, with an injection pressure of 200 bar improving combustion efficiency by ∼3 percentage points and advancing knock-limited CA50 by 1 crank angle degree over an injection pressure of 30 bar. Then, a compression stroke injection was introduced and swept into the compression stroke while maintaining the two intake stroke injections. Direct injections at an injection pressure of 30 bar enabled a small knock intensity reduction of ∼20%, whereas an injection pressure of 200 bar enabled a larger reduction of ∼90% in knock intensity. The spark timing advance permitted by the reduction in knock intensity with a compression stroke injection timing of −80 degrees after top dead center was 0.3 and 2.0 degrees at an injection pressure of 30 and 200 bar, respectively. Then, the second intake stroke injection was varied at 200 bar to evaluate how the stratification profile prior to the compression stroke injection impacted its ability to reduce knock intensity. It was found that compression stroke injections with an early second intake stroke injection was effective at reducing knock intensity throughout the compression stroke. As the second intake stroke injection was retarded, the early compression stroke injections became less effective at suppressing knock.

The influence of injection pressure and exhaust gas recirculation on a VCR engine fueled by microalgae biodiesel

AbstractBiodiesel has been chosen as a decent alternative to diesel in the context of establishing environmentally pleasant conditions and saving petroleum‐based resources for future generations. It is well‐established that biodiesel‐powered diesel engines may achieve outcomes equivalent to those of diesel engines. The current investigation was conducted to study the effect of injection pressure (190, 210, and 230 bar) and exhaust gas recirculation (EGR) (5%, 10%, and 15%) on a single‐cylinder variable compression ratio (VCR) diesel engine running using a B20 (20% MB + 80% PD) blend of microalgae biodiesel (MABD). This experiment was conducted in two stages. During the first stage of experimentation, the efficiency and emission characteristics of a diesel engine with a B20 blend of MABD at various fuel injection pressures and fresh air were investigated. During the second phase, fresh air was mixed with 5%, 10%, and 15% exhaust gases, and the experiment was conducted. It was discovered that increasing injection pressure to 230 bar provided considerable improvements. Brake thermal efficiency increased by 2.35%, brake‐specific fuel consumption decreased by 3.57% and pollutants such as carbon monoxide (CO), hydrocarbon, and smoke were reduced by more than 50% compared to conventional diesel. These reductions were similarly significant (over 22%) as compared to the B20 blend at lower injection pressure (210 bar). However, there was a slight trade‐off: nitrogen oxide (NOx) emissions increased partially (3.14%), while exhaust gas temperature (EGT) increased by 1.72% at a higher pressure. The study then investigated the influence of EGR (5%, 10%, and 15%) at various injection pressures. The optimal value seems to be 10% EGR at 230 bar injection pressure. This combination substantially reduced NOx emissions (by over 41% compared to the normal B20 blend) and EGT (by more than 8%), while having no notable effect on other performance or emission variables. Overall, the results show that employing a B20 MABD blend with high injection pressure (230 bar) and moderate EGR (10%) improves engine performance while reducing hazardous emissions.

Study on the influence of injection pressure and frequency on the deformation and damage law of the surrounding rock in the old cavity of salt mine

AbstractThe long‐term cyclic gas injection and production mode of the gas storage will lead to accelerated deformation of the surrounding rock of the old cavity, and even the instability and failure of the cavity. Considering the geological conditions and cavity measurement data of the old cavity of the horizontal butted‐well in China, the deformation and failure characteristics of the long‐term cyclic injection‐production process of the surrounding rock of the old cavity under different internal pressure difference and injection‐production frequency are studied. The long‐term stability of the gas storage is predicted by six indexes: the deformation of surrounding rock, dilatancy safety factor, volume shrinkage rate, plastic zone volume, equivalent strain, and no tensile stress. The results show that with the increase of operation duration and cycle times, the deformation, volume shrinkage rate, and plastic zone volume of the surrounding rock gradually increase after the old cavity is reconstructed into the gas storage and the difference of results under different UGS and CAES gradually expands. The stability of the surrounding rock of the old cavity under the cycle action of CAES will be lower. The number of cycles has a limited impact on the stability of the surrounding rock of the old cavity, while the operation duration and injection‐production pressure are the main determinants of the stability of the surrounding rock of the old cavity. If the old cavity of the salt mine is reconstructed into CAES, the parameters such as the number of cycles, the operation duration, and the injection‐production pressure still need to be considered comprehensively. The research results can provide reference value for the reasonable design of the gas storage pressure range of the old cavity and the safety and stability evaluation of the surrounding rock.

Influence of injection pressure on gas adsorption and desorption of anthracite

In this paper, THM model and coal molecular model are established to study the gas adsorption and desorption behavior in coal seam at different injection pressures. The results show that, the total energy decreases during the adsorption process and increases in the desorption process. CO2 has a stronger adsorption capacity which is in a dominant position in the competition adsorption process, while N2 is in a weak position. The order of the diffusion coefficient is N2>CH4(CH4–N2) > CH4(CH4–CO2) > CO2. The diffusion coefficient does not necessarily increase with the increase of injection pressure. At the same injection pressure, the relative concentration of CH4 in the CH4–CO2 system is greater than that in the CH4–N2 system, and injection of CO2 to promote CH4 desorption is significantly better than the injection of N2. With the increase of injection pressure, the average relative concentration of CH4/CO2/N2 in the vacuum layer increased. The optimal injection pressure for N2 injection to promote CH4 desorption is 2 MPa, and the reasonable injection pressure for CO2 injection is 1–3 MPa.

Pore-scale modeling of thermal-hydro-mechanical-chemical coupled rock dissolution and fracturing process

Acid fracturing can effectively improve the connectivity inside underground reservoirs, which is of significance for geothermal exploitation and geological carbon sequestration. It involves a complex thermal-hydro-mechanical-chemical (THMC) coupled process. This work first develops a pore-scale THMC coupled model combining the lattice Boltzmann method (LBM) and the discrete element method (DEM) to describe the acid fracturing process, particularly covering chemical damage, rock dissolution, and solute transport. A chemical damage variable based on the cohesive bond is proposed to characterize the alteration of mechanical parameters caused by local rock dissolution. The change of fluid pathway due to rock dissolution is handled by the lattice Boltzmann solute transport model combined with the volume of pixel method. Based on the proposed model, the influence of injection pressure and Damkohler number (Da) on the THMC coupled rock dissolution and fracturing process is analyzed. Results indicate three types according to dissolution morphologies, i.e., permeation, cavity, and permeation-cavity. The first and second types are related to the reaction-controlled and diffusion-controlled processes, respectively. Particularly, the permeation-cavity type occurs at conditions with high injection pressure and high Da and is the combination of the first two types, where the dissolution around the main fracture presents the cavity type but converts into the permeation type around secondary fractures. Additionally, the evolution patterns of reactive surface area and dissolution rate with time differ significantly with rock dissolution types. In particular, for the permeation type, the aperture of fracture far away from the injection hole could be larger than that near the injection hole under the THMC coupling, which is quite different from HM and THM coupling.

Thermal-Hydraulic-Mechanical Coupling Simulation of CO2 Enhanced Coalbed Methane Recovery with Regards to Low-Rank but Relatively Shallow Coal Seams

CO2 injection technology into coal seams to enhance CH4 recovery (CO2-ECBM), therefore presenting the dual benefit of greenhouse gas emission reduction and clean fossil energy development. In order to gaze into the features of CO2 injection’s influence on reservoir pressure and permeability, the Thermal-Hydraulic-Mechanical coupling mechanism of CO2 injection into the coal seam is considered for investigation. The competitive adsorption, diffusion, and seepage flowing of CO2 and CH4 as well as the dynamic evolution of fracture porosity of coal seams are considered. Fluid physical parameters are obtained by the fitting equation using MATLAB to call EOS software Refprop. Based on the Canadian CO2-ECBM project CSEMP, the numerical simulation targeting shallow low-rank coal is carried out, and the finite element method is used in the software COMSOL Multiphysics. Firstly, the direct recovery (CBM) and CO2-ECBM are compared, and it is confirmed that the injection of CO2 has a significant improvement effect on methane production. Secondly, the influence of injection pressure and temperature is discussed. Increasing the injection pressure can increase the pressure difference in the reservoir in a short time, so as to improve the CH4 production and CO2 storage. However, the increase in gas injection pressure will also lead to the rapid attenuation of near-well reservoir permeability, resulting in the weakening of injection capacity. Also, when the injection temperature increases, the CO2 concentration is relatively reduced, and the replacement effect on CH4 is weakened, resulting in a slight decrease in CBM production and CO2 storage.

Schlieren and mie-scattering visualization of an evaporating spray under marine diesel engine conditions

Due to the critical influence on combustion, extensive research has been carried out to deepen the understanding of diesel spray evolution. However, for the greater share of land-based diesel engines, most of the studies have focused on the injectors with small nozzle diameter and rare studies can be found on marine diesel engines, which has a larger mass flow rate and longer injection duration with large nozzle diameter. In this study, the influence of injection pressure, ambient temperature, ambient density and nozzle diameter on spray morphology for medium speed marine diesel engine injectors (with nozzle diameter up to 0.53 mm) were investigated under various non-reacting but evaporative conditions. The experiments were performed via a highly enhanced constant volume chamber (highest temperature of 900 K and highest pressure of 8 MPa) with an optical window diameter of 205 mm. Liquid and vapor penetration of sprays were recorded by Mie-scattering and schlieren optical configurations respectively. Results show that the vapor penetration velocity is mainly affected by injection pressure. Ambient temperature has the most significant effect on liquid penetration length, but less effect can be found on the vapor penetration velocity. Given the obvious deviation from heavy duty engine sprays, the empirical correlations for liquid penetration length and vapor spray evolution are updated to fit the spray characteristics of medium speed marine diesel engine injectors, which is helpful to understand the spray behavior for large nozzle diameter injector under marine diesel engine conditions.

Influence of Injection Pressure and Aluminium Oxide Nano Particle-Added Fish Oil Methyl Ester on the Performance and Emission of Compression Ignition Engine

The present experimental examination was carried out to suggest a better fuel blend with an optimised dosage level of alumina nanoparticles (Al2O3)—in a mixture of Fish Oil Methyl Ester (FOME) biodiesel and diesel—and injection pressure, wherein enhanced performance and reduced emissions were obtained via a diesel engine. The aluminium nanoparticles were added to the mixture in 5 mg/l steps through varying concentrations from 5 to 20 mg/L. The experimental results showed that engine performance quietly reduces with increased emission characteristics with the addition of raw FOME biodiesel compared to diesel. Furthermore, the addition of aluminium nanoparticles (Al2O3) improved the performance as well as the emission characteristics of the engine. Among all the test blends, the B40D60A20 blend provided a maximum brake thermal efficiency of 30.7%, which is 15.63% superior to raw FOME and 3.90% inferior to diesel fuel. The blend also showed reduced emissions, for instance, a reduction of 48.38% in CO, 17.51% in HC, 16.52% in NOx, and 20.89% in smoke compared to diesel fuel. Lastly, it was concluded that B40D60A20 at 260 bar is the optimised fuel blend, and 20 mg/l is the recommended dose level of aluminium nanoparticles (Al2O3) in the FOME–diesel mixture biodiesels in order to enhance the performance and emission parameters of a diesel engine.

Effects of Injection Pressure and Duration on Alternate High-Pressure Water-Gas Sequestration of Coalbed Methane

To solve the problems of high ground stress, low permeability and low coalbed methane recovery, this paper proposes an optimization technique for improving coal seam permeability, i.e., water-gas alternating displacement enhances coalbed methane recovery (WGA-ECBM). The seepage field of gas-water two-phase flow is derived and a multiphase fluid-solid coupling model between physical parameters is established. This paper studies the effects of three displacement methods (water injection, air injection and water-air alternating injection) on methane recovery. The influence of injection pressure and injection duration on the WGA-ECBM technique is also studied. The V C H 4 (methane volume fraction) of the three methods decrease by 17.84%, 12.72% and 44.62% in the borehole, respectively. The influence ranges (diameter) are 24.68 m, 149.73 m and 135.21 m, respectively. Pore pressures and displacement area also increase as injection pressure increases in a 5 MPa gradient. And V C H 4 in the borehole decrease by 35.57%, 43.82%, 46.78% and 51.72% from 10 MPa to 25 MPa, respectively. With the increase of injection duration, the influence range expands significantly but the pore pressure distribution changes little. And V C H 4 decreases slightly in the displaced area and the displacement velocity gradually slows down. This technique promotes multiphase flow migration in coal seam, and increases the displacement range and methane recovery efficiency.

Influence of Injection Pressure on the Dual-Fuel Mode in CI Engines Fueled with Blends of Ethanol and Tamanu Biodiesel

The acceleration of global warming is primarily attributable to nonrenewable energy sources such as conventional fossil fuels. The primary source of energy for the automobile sector is petroleum products. Petroleum fuel is depleting daily, and its use produces a significant amount of greenhouse emissions. Biofuels would be a viable alternative to petroleum fuels, but a redesign of the engine would be required for complete substitution. The use of CNG in SI engines is not new, but it has not yet been implemented in CI engines. This is due to the fuel having a greater octane rating. The sole use of CNG in a CI engine results in knocking and excessive vibration. This study utilizes CNG under dual-fuel conditions when delivered through the intake manifold. In a dual-fuel mode, compressed natural gas (CNG) is utilized as the secondary fuel and a blend of 90% tamanu methyl ester and 10% ethanol (TMEE10) is used as the primary fuel. The injection pressure (IP) of the primary fuel changes between 200 and 240 bar, while the CNG induction rate is kept constant at 0.17 kg/h. The main combustion process is governed by the injection pressure of the pilot fuel. It could be affecting factors such as the vaporization characteristics of the fuel, the homogeneity of the mixture, and the ignition delay. Originally, tamanu methyl ester (TME) and diesel were used as base fuels in the investigation. As a result of its inherent oxygen content, TME emits more NOx than diesel. The addition of 10% ethanol to TME (TMEE10) marginally reduces NOx emissions in a CI mode because of its high latent heat of vaporization characteristics. Under peak load conditions, NOx emissions of TMEE10 are 6.2% lower than those of neat TME in the CI mode. Furthermore, the experiment was conducted using TMEE10 as the primary fuel and CNG as the secondary fuel. In the dual-fuel mode, the TMEE10 blend showed higher combustion, resulting in an increase in performance and a significant decrease in emission characteristics. As a result of the CNG’s high-energy value and rapid burning rate, the brake thermal efficiency (BTE) of TMEE10 improves to 29.09% compared to 27.09% for neat TME. In the dual-fuel mode of TMEE10 with 20.2% CNG energy sharing, the greatest reduction in fuel consumption was 2.9%. TMEE10 with CNG induction emits 7.8%, 12.5%, and 15.5% less HC, CO, and smoke, respectively, than TME operation.

Atomization Characteristics of Low-Volatility Heavy Fuel for Low-Pressure Direct Injection Aviation Piston Engines

Abstract Due to safety and convenience, aviation heavy fuel (AHF) is quite suitable for use as an energy source in aviation piston engines for small aerial drones, although its atomization is an important issue. The purpose of this article is to present the atomization mechanism of AHF during low-pressure direct injection (LPDI) and the results of the investigation of the mixing process and flow state of fuel–air two-phase flows. In this study, experimental data were obtained for parameters of fuel spray, which verified the improved calculation model of LPDI that considered the primary atomization of AHF inside the premixing chamber. The influences of injection pressure, ambient pressure, and AHF temperature on the spray characteristics were compared and analyzed. Increasing the injection pressure reduced the spray cone angle and increased the spray area. The penetration distance increased, and the Sauter mean diameter (SMD) of the fuel droplets decreased. Increasing the ambient pressure had significant effects on penetration distance and SMD. The spray area decreased, and the spray cone angle showed small variations. Increasing the AHF temperature had small effects on the penetration distance, and the SMD obviously decreased with increasing fuel temperature. The spray cone angle increased slightly, and the spray area decreased. The results showed that low-volatility AHF for safe and stable engine combustion could be achieved with air-assisted LPDI. In addition, the efficient atomization of AHF can be effectively implemented through the combined adjustment of injection control and physical and chemical parameters.

Investigations of bubble size distribution on swirl effervescent atomizer flotation

Atomizer flotation has the advantages of low cost, low energy consumption, adjustable, and long cycle life in industrial applications. The bubble diameter is an important parameter for floatation. The smaller the bubble diameter, the better the flotation effect. However, the bubble diameter produced by the atomizer during flotation separation is large at present. In this paper, a swirl effervescent atomizer is designed and experimental diagnosis through a spray measurement system and submerged spray visualization system. The diameter and size distribution of bubbles in 5 mm from the atomizer outlet to the jet cross-section spray were discussed. The results showed that the swirl effervescent atomizer obtained a fine Sauter mean diameter (SMD is 13–25 μm) compared with the traditional atomizer. Three flow patterns were observed at the submerged spray system: large bubbly flow, discrete bubbly flow, and slug flow. A statistical method of bubbles under high injection pressure was proposed. The effects of the operating conditions of the effervescent atomizer on the bubble diameter were investigated. The average bubble diameter decreased with the increase in injection pressure and gas–liquid mass flow ratios (GLR). However, with the GLR being increased to 0.15, the influence of injection pressure on bubble diameter was reduced. The backpressures (Liquid level heights) have less effect on bubbles compared with injection pressure and GLR. This paper has great significance for the sustainable development of the atomizer in the flotation separation application.

Experimental study on spatial distribution characteristics of cylinder-wall oil films under fuel spray impinging condition of GDI engine

This research investigates GDI (Gasoline Direct Injection) fuel spray characteristics, and spray impingement on cylinder-wall oil film were carried out in a constant volume chamber. For studying free spray and spatial distribution characteristics of oil film under spray impinging conditions, the backlight method and LIF (Laser Induced Fluorescence) technology were used, respectively. The influence of injection pressure, ambient pressure, and ambient temperature on the distribution characteristics of oil film with spray impingement were examined. Detailed results on coalescence/splash thresholds criteria of oil film were obtained by considering the incident spray Weber number and the injected fuel mass. In addition, the formation mechanism of oil dilution and splash following the collision were analyzed. It has been found that the incident Weber number is not the only discriminant parameter that can be used to determine the splash criticality of a fuel droplet or spray hitting an oil film. Meanwhile, spray impingement at a higher injection pressure results in a wider spread of oil film, whereas a higher ambient pressure inhibits the spread of oil film.

Emission Characteristics and Engine Performance from Castor Oil Methyl Ester Blends in Diesel Engine under Various Injection Pressures

The use of fuel injection pressure and oxygenated fuels in transport sector are the considerable challenges in making environmentally clean without any modifications in engine design. Therefore, the influence of injection pressure on engine performance and exhaust emission characteristics of common-rail diesel engine has been investigated in this study. The research engine was operated with castor oil blended into the diesel in different percentages at different injection pressures (200, 300, 400 and 500 bar). The results showed that the BSFC increased by 37.2%, 26.8%, 24.53% and 20.31%, from the combustion of COD100, COD10, COD20 and COD30, respectively, and also the thermal efficiency increased from the oxygenated fuels in comparison with diesel under low and high injection pressure. Furthermore, the average reduction of CO and HC emissions was 27.4% and 21.6% from the combustion of castor oil-diesel (COD) blends under 500 bar. The NOX emissions slightly decreased by 7.3% with increasing the injection pressure up to 500 bar from all COD blends compared to the diesel. It is indicated that the CO2 emissions increased by 8.6% form the COD blends combustion compared to the diesel with increasing FIP. The PM concentrations gradually decreased with increase the injection pressures by 33.6%, 26.25%, 20.7%, and 17.4% from CO100, CO30D, CO20D and CO10D, respectively.

Influence of injection pressure and injection timing on pollution levels of insulated diesel engine fuelled with CNG and cotton seed biodiesel

In the context of fast depletion of fossil fuels, increase of pollution levels with fossils and increase of economic burden due to increase of import cost of crude petroleum, the search for alternative fuels has become pertinent. The most common alternative fuels for CI engine are vegetable oils, biodiesel and alcohols. Gaseous fuels have many advantages than liquid fuels, as the pollutants emitted by gaseous fuels are low, calorific value of the gases is very high and running and maintenance cost is low. The drawbacks associated with vegetable oils such as high viscosity and low volatility can be rectified to some extend by converting them into biodiesel. How they (biodiesel) cause combustion problems in diesel engine and hence call for low heat rejection (LHR) engine, which can burn low calorific value fuel, give high heat release rate and faster rate of combustion. Investigations were carried out with CNG as primary fuel inducted by port injection and cottonseed biodiesel blended with 15% of diethyl ether (DEE) was injected into the engine in conventional manner with LHR engine consisted of ceramic coated cylinder head. The purpose of DEE was to improve cetane (a measure of combustion quality in diesel engine) and to reduce viscosity of the cotton seed biodiesel. Particulate matter (PM), oxides of nitrogen (NOx), carbon mono oxide (CO) levels and un-burnt hydro carbons (UBHC) are the exhaust emissions from a diesel engine. They cause health hazards, once they are inhaled in. They also cause environmental effects like Green-house effect, acid raining, Global Warming etc,. Hence control of these emissions is an immediate effect and an urgent step. The pollutants of PM, NOx, CO and UBHC were determined at full load operation of the engine and compared with diesel operation on conventional engine. The maximum induction of CNG was 35% of total mass of biodiesel, with CE, while it was 45% with LHR engine at full load operation. Particulate emissions were determined by AVL Smoke meter, while other emissions were measured by Netel Chromatograph multi-gas analyzer at full load operation. The optimum injection timing with cottonseed biodiesel was 31obTDC (before top dead centre), with CE, while it was 28obTDC with LHR engine. These pollutants were drastically reduced with induction of CNG and further reduced with the provision of LHR engine. They were further reduced with advanced injection timing and increase of injection pressure.

Influence of injection pressure on performance and emission characteristics of single cylinder RCCI engine fuelled with ethanol gasoline and diesel biodiesel blends

Reactivity controlled compression ignition (RCCI) has great potential for a simultaneous reduction in Nitrogen oxides (NOx) and particulate matter (PM) with increase in thermal efficiency. In this experimentation, an attempt is made to investigate the effect of injection pressure on the performance emission and combustion characteristics of single cylinder RCCI engine. Literature reveals that injection pressure has a great influence on the quality of charge preparation, fuel stratification, and incylinder reactivity. Suitably modified engine was operated for 0 to 12 kg loads, for 400 to 700 injection pressure. The blend of ethanol gasoline E20 used as a low reactivity fuel and blend of diesel jatropha biodiesel B20 used as a high reactivity fuel. Experimental results showed that increase in injection pressure enhances the degree of charge homogeneity, reduces the combustion duration, and provides higher rate of energy release. For 12 kg load and 700 bar injection pressure, it is observed that 5% rise in thermal efficiency, 27% reduction in smoke opacity, 2% reduction in HC, 4% reduction in CO and 20% rise in NOx as compared to 400 bar injection pressure.

Liquid Propane Injection in Flash-Boiling Conditions

This study aimed to investigate the influence of flash-boiling conditions on liquid propane sprays formed by a multi-hole injector at various injection pressures. The focus was on spray structures, which were analysed qualitatively and quantitatively by means of spray-tip penetration and global spray angle. The effect of flash boiling was evaluated in terms of trends observed for subcooled conditions. Propane was injected by a commercial gasoline direct injector into a constant volume vessel filled with nitrogen at pressures from 0.1 MPa up to 6 MPa. The temperature of the injected liquid was kept constant. The evolution of the spray penetration was observed by a high-speed camera with a Schlieren set-up. The obtained results provided information on the spray evolution in both regimes, above and below the saturation pressure of the propane. Based on the experimental results, an attempt to calibrate a simulation model has been made. The main advantage of the study is that the effects of injection pressure on the formation of propane sprays were investigated for both subcooled and flash-boiling conditions. Moreover, the impact of the changing viscosity and surface tension was limited, as the temperature of the injected liquid was kept at the same level. The results showed that despite very different spray behaviours in the subcooled and flash-boiling regimes, leading to different spray structures and a spray collapse for strong flash boiling, the influence of injection pressure on propane sprays in terms of spray-tip penetration and spray angle is very similar for both conditions, subcooled and flash boiling. As for the numerical model, there were no single model settings to simulate the flashing sprays properly. Moreover, the spray collapse was not represented very well, making the simulation set-up more suitable for less superheated sprays.

Effect of Injection Pressure on the Performance and Emission Characteristics of Niger-Diesel-Ethanol Blends in CI Engine

Biodiesel is promising as the best substitute/alternative fuel to most diesel engines due to its low sulfur content, lower aromatic hydrocarbon, renewable, and more oxygenated fuel. The dried Niger seeds were collected for their oil extraction and biodiesel production in the current research. This paper concerns about the influence of injection pressure on a single-cylinder VCR direct injection diesel engine using Niger oil biodiesel, diesel and ethanol blends, B5+D90+E5 (5% Biodiesel + 90% Diesel + 5% Ethanol), B10+D80+E10 (10% Biodiesel + 80% Diesel + 10% Ethanol) and B15+D70+E15 (15% Biodiesel + 70% Diesel + 15% Ethanol). The performance, combustion, and emission characteristics are observed for the above blends at the various pressures of 180 bar to 220 bar with 20 bar variations. At low injection pressures, the two blends (B5+D90+E5 and B10+D80+E10) show considerable improvement in brake thermal efficiency and mechanical efficiency compared to baseline diesel. At high injection, pressures blend B15+D70+E15 produce higher brake thermal efficiency and mechanical efficiency. Consequently, less brake-specific fuel consumption and less ignition delay period for the blends respectively. The exhaust pipe emissions such as Carbon Dioxide (CO2), Carbon Monoxide (CO), Hydrocarbons (HC), Nitrogen oxides (NOX) are measured at rated power at all injection pressures. CO2, CO, and HC are low at high injection pressure, but NOX increases as injection pressure increases.

Numerical study on the mixing and evaporation process of a liquid kerosene jet in a scramjet combustor

The mixing and evaporation process of a liquid kerosene jet in a scramjet combustor with dual-cavity is investigated by two-phase Large Eddy Simulation. The gas-droplet flow system is solved through a two-way coupled Eulerian-Lagrangian method. The primary and secondary breakup processes of the liquid fuel jet are taken into account. The Langmuir-Knudsen evaporation model, which considers the non-equilibrium effect, is used to calculate the evaporation process of the droplets. The penetration depth of the jet is in good agreement with the experimental value. The dynamic process of the liquid jet breakup, spray evaporation, and fuel transportation within the combustor are well described by the numerical results. The distribution and evaporation characteristics of the spray are analyzed and most droplets are evaporated within 30 mm downstream of the jet orifice. However, a small portion of droplets with high velocity and low temperature can survive for a long distance. The influence of injection pressure on the mixing process near the cavity is also analyzed, and it is found that the injection pressure affects the total quantity of fuel entrained into the cavity by affecting the fuel distribution in the near-wall region and the total fuel mass flow rate. The local distribution of the liquid and gas phase fuels, local temperature and turbulence characteristics in the cavity are analyzed, and the ignition environment on the development path of the flame kernel is discussed. The results indicate that the injection pressure and the distance between the cavity and the orifice have a critical effect on the quantity of the kerosene entrained into the cavity, which then have a great influence on the ignition environment in the cavity.