scholarly journals Microbial healing of nature-like rough sandstone fractures for rock weathering mitigation

2022 ◽  
Author(s):  
Zhi-Hao Dong ◽  
Xiaohua Pan ◽  
Chao-Sheng Tang ◽  
Bin Shi
Keyword(s):  
Fracture Healing ◽  
Injection Pressure ◽  
Solution Concentration ◽  
Fracture Aperture ◽  
Rock Weathering ◽  
Calcium Carbonate Precipitation ◽  
High Fracture ◽  
Injection Strategy ◽  
Healing Efficiency ◽  
Fracture Transmissivity

Abstract Rock weathering fractures in nature are complex and fracture healing is an effective strategy for rock weathering mitigation. This study is a first attempt to apply microbially induced calcium carbonate precipitation (MICP) technology in the healing of nature-weathering-like rough fractures (NWLRF). Sandstone was studied as an example due to it is a wide-spread construction, sculpture and monuments material all over the world. In order to achieve a high healing efficiency, a repeated mixture injection strategy was proposed. Based on a series of laboratory MICP injection experiments on four types of NWLRF, we systematically explored the fundamental micro-healing mechanism and the influence of factors including fracture aperture, characteristics of branch fractures, and cementation solution concentration. Experimental results demonstrated that MICP healing with the repeated mixture injection strategy had the ability to efficiently heal the penetrated NWLRF well with length in centimeter-scale and aperture in millimeter-scale, but cannot heal the non-penetrated branch fractures under low injection pressure. The repeated mixture injection strategy furtherly achieved a high apparent fracture healing ratio and a significant reduction of transmissivity. The apparent fracture healing ratios of all main fractures were higher than 80% and the maximum was 99.1%. Fracture transmissivity was reduced by at least three orders of magnitude from about 1×10-4 m2/s to less than 1×10-7 m2/s, and the highest reduction reached to four orders. For the aspect of the effects, larger cementation solution concentration, finer aperture and the existing of penetrated branch fracture were beneficial to improve the healing effect. Moreover, the MICP healing mechanism with high fracture healing ratio and significant reduction of transmissivity on sandstone NWLRF was also analyzed. The research results have important theoretical significance and technical guidance value for the disaster prevention and mitigation of rock weathering.

Effect of the Fuel Injection Strategy on Diesel Particulate Filter Regeneration in a Single-Cylinder Diesel Engine

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Sungjun Yoon ◽  
Hongsuk Kim ◽  
Daesik Kim ◽  
Sungwook Park
Keyword(s):  
Fuel Injection ◽  
Injection Pressure ◽  
Operating Conditions ◽  
Particulate Filter ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Diesel Particulate ◽  
Injection Strategy ◽  
Dpf Regeneration ◽  
Exhaust Gas Temperature

Stringent emission regulations (e.g., Euro-6) have forced automotive manufacturers to equip a diesel particulate filter (DPF) on diesel cars. Generally, postinjection is used as a method to regenerate the DPF. However, it is known that postinjection deteriorates the specific fuel consumption and causes oil dilution for some operating conditions. Thus, an injection strategy for regeneration is one of the key technologies for diesel powertrains equipped with a DPF. This paper presents correlations between the fuel injection strategy and exhaust gas temperature for DPF regeneration. The experimental apparatus consists of a single-cylinder diesel engine, a DC dynamometer, an emission test bench, and an engine control system. In the present study, the postinjection timing was in the range of 40 deg aTDC to 110 deg aTDC and double postinjection was considered. In addition, the effects of the injection pressure were investigated. The engine load was varied among low load to midload conditions, and the amount of fuel of postinjection was increased up to 10 mg/stk. The oil dilution during the fuel injection and combustion processes was estimated by the diesel loss measured by comparing two global equivalences ratios: one measured from a lambda sensor installed at the exhaust port and one estimated from the intake air mass and injected fuel mass. In the present study, the differences of the global equivalence ratios were mainly caused by the oil dilution during postinjection. The experimental results of the present study suggest optimal engine operating conditions including the fuel injection strategy to obtain an appropriate exhaust gas temperature for DPF regeneration. The experimental results of the exhaust gas temperature distributions for various engine operating conditions are discussed. In addition, it was revealed that the amount of oil dilution was reduced by splitting the postinjection (i.e., double postinjection). The effects of the injection pressure on the exhaust gas temperature were dependent on the combustion phasing and injection strategies.

Low End Performance Improvement by Effective Use of Multiple Injection Strategy in Common Rail Diesel Engine

2009 ◽  
Author(s):  
Dilunath Hareendranath ◽  
Nilesh Gajarlawar ◽  
Murali Manickam ◽  
Ghodke Pundlik
Keyword(s):  
Diesel Engine ◽  
Engine Speed ◽  
Injection Pressure ◽  
Common Rail ◽  
Multiple Injection ◽  
Injection Strategy ◽  
Part Load ◽  
Black Smoke ◽  
Multiple Injection Strategy ◽  
Lower Engine Speed

Main advantages of diesel engine are low fuel consumption coupled with high specific power output. However, benchmark Noise, Vibration and Harshness (NVH) of its counterpart (Gasoline), future stringent emission norms and overall system cost poses tough challenges. In a growing market like India, these benefits of diesel attract the buyer over its counterpart. Diesel engines are known for its heavy visible black smoke. The black smoke formation is more prominent in lower engine speed. This is due to lower injection pressure and the system limitation in conventional injection system and less air availability. Introduction of the common rail injection technology overcomes this difficulty by allowing the injection pressure to build irrespective of the engine speed. However, improving the air flow is a challenge. Generally waste gate turbo chargers are optimized for higher engine speed to match the rated engine performance, but compromising the lower engine speed performance. The use of Variable Geometry turbo charging (VGT), increase in number of valves per cylinder, two stage turbo charging are some of the solutions to this problem but it involves additional cost and fundamental design changes. Hence, it was a challenge to come up with a strategy to overcome this problem without any cost impact. Multiple injection strategy is one of the tools which improve the engine torque without the penalty of smoke. In this paper, a Multi Utility Vehicle (MUV) powered by a 2.5Ldiesel common rail engine, low end performance was effectively improved by this strategy. Current engine has BOSCH 2nd generation common rail system with waste gate Turbocharger. Torque at full load in lower engine speed was improved by introducing the early pilot with relatively higher quantity. However, in the part load, this pilot quantity was split into two successive pilot injections. Selection of pilot separation was optimized in such a way that Noise and Smoke levels are maintained or improved. In part load, improvement in smoke and BSFC was achieved without sacrificing noise level. Engine level trials were conducted with cylinder pressure and Noise Measurement with AVL Indicom. The Concept of Design of experiment (DOE) was used to minimize the number of iteration and for analysis of results. The vehicle performance, pass by noise were found to be improved.

Artificial Neural Network to Predict the Thermal Drawdown of Enhanced Geothermal System

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
S. N. Pandey ◽  
M. Singh
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Mass Flux ◽  
Operating Conditions ◽  
Percentage Error ◽  
Geothermal System ◽  
Fracture Aperture ◽  
Enhanced Geothermal System ◽  
Fracture Transmissivity ◽  
Artificial Neural

Abstract This work presents the prediction of thermal drawdown of an enhanced geothermal system (EGS) using artificial neural network (ANN). A three-dimensional numerical model of EGS was developed to generate the training and testing data sets for ANN. We have performed a quantitative study of geothermal energy production for various injection operating conditions and reservoir fracture aperture. Input parameters for ANN include temperature, mass flux, pressure, and fracture transmissivity, while the production well temperature is the output parameter. The Levenberg–Marquardt back-propagation learning algorithm, the tan-sigmoid, and the linear transfer function were used for the ANN optimization. The best results were obtained with an ANN architecture composed of eight hidden layers and 20 neurons in the hidden layer, which made it possible to predict the production temperature with a satisfactory range (R2 > 0.99). An appropriate accuracy of the ANN model was obtained with a percentage error less than (± 4.5). The results from the numerical simulations suggest that fracture transmissivity has less effect on thermal drawdown than the injection mass flux and temperature. From our results, we confirm that ANN modeling may predict the thermal drawdown of an EGS system with high accuracy.

Soluble Silicates as Additives for Self-Sealing and Self-Healing Concrete

2016 ◽  
Vol 1813 ◽  
Author(s):  
L. E. Rendon Diaz Miron ◽  
M. E. Lara Magaña
Keyword(s):  
Mechanical Properties ◽  
Crack Formation ◽  
Healing Process ◽  
Self Healing ◽  
Reaction Products ◽  
Calcium Carbonate Precipitation ◽  
Broad Perspective ◽  
Healing Efficiency ◽  
Tensile Forces ◽  
Solubility Ratio

ABSTRACTTensile strength of concrete is limited and therefore is sensitive to crack formation. Steel reinforcement is added to bear the tensile forces; nonetheless, this does not completely omit crack formation. Repair of cracks in concrete is time-consuming and expensive. Self-sealing and self-healing of cracks upon appearance would therefore be a convenient property. We propose a mechanism to obtain self-repair of the concrete by adding soluble silicates (ASS) which will induce a self-sealing and self-healing process catalyzed by natural periods of wet and dry states of the concrete. Self-sealing approaches prevent the ingress of harsh chemical substances which may deteriorate the concrete matrix. This can be achieved by self-healing of concrete cracks (e.g. further cement hydration, calcium carbonate precipitation) and autonomous healing (e.g. further hydration of partially soluble silicates added as healing agents). The autogenous healing efficiency depends on the amount of deposited reaction products (ASS), its solubility (ratio of calcium to sodium silicate), the availability of water, and the crack width (restricted by adding microfibers). The self-sealing efficiency is generally evaluated by measuring the decrease in water permeability and air flow through the crack. The healing efficiency is usually evaluated by testing concrete´s regain in mechanical properties after crack formation; by reloading the cracked and autonomously healed specimen and comparing the obtained mechanical properties with the original ones. Self-sealing and self-healing of concrete gives a broad perspective and new possibilities to make future concrete structures more durable.

Characterization of the distribution-nozzle operation for mixture homogenization by a late-diesel-injection strategy

2011 ◽  
Vol 226 (4) ◽  
pp. 529-546 ◽  
Author(s):  
M Weclas ◽  
J Cypris
Keyword(s):  
Combustion Process ◽  
Injection Pressure ◽  
Ignition Timing ◽  
Mixture Formation ◽  
Penetration Length ◽  
Injection Strategy ◽  
Fuel Distribution ◽  
Diesel Injection ◽  
Fuel Vaporization ◽  
Homogeneous Combustion

In order to realize a homogeneous combustion process it is necessary to decouple this combustion process from fuel injection. This homogeneous combustion process requires the charge to be homogeneous prior to simultaneous volumetric ignition. This kind of ignition is a self-ignition process requiring control of the ignition timing. A late-injection strategy as used in a conventional diesel engine permits control of the ignition timing; however, the time available for mixture formation and the homogenization process is very limited. The present paper deals with a distribution-nozzle concept which combines both strategies: a late-injection strategy for controlling the ignition timing with significantly accelerated fuel distribution in space and corresponding mixture homogenization. The distribution-nozzle concept combines a conventional diesel nozzle with a porous element (ring) positioned in proximity to the nozzle outlet. Because of multi-jet splitting as a result of the diesel-jet interaction with a porous structure, the fuel leaving the porous ring spreads widely in space. Additionally, a very effective fuel vaporization process occurs within the porous structure, supporting quick mixture formation. The paper describes both the fuel distribution in space and its vaporization for different configurations of the distribution elements, the injection pressure, and the porous ring temperature. In comparison with a free diesel injection, the distribution nozzle results in a significantly increased fuel surface area, a reduced jet penetration length, a reduced jet velocity, and very quick fuel vaporization. This process is three dimensional in nature. Depending on the distribution-element structure, the geometry, and its temperature, as well as the injection pressure, the contributions of multi-jet splitting, and fuel vaporization, are different with respect to the surface area, penetration length, and exit velocity, as well as intensity distribution. Generally, at higher injection pressures these parameters are less temperature dependent, except for the fact that the intensity distribution is a function of the fuel vapour’s concentration.

Fuel Injection Strategy for Utilization of Mineral Diesel-Methanol Blend in a Common Rail Direct Injection Engine

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Akhilendra Pratap Singh ◽  
Nikhil Sharma ◽  
Vikram Kumar ◽  
Dev Prakash Satsangi ◽  
Avinash Kumar Agarwal
Keyword(s):  
Fuel Injection ◽  
Direct Injection ◽  
Injection Pressure ◽  
Pilot Injection ◽  
Oxides Of Nitrogen ◽  
Gas Temperature ◽  
Injection Strategy ◽  
Main Injection ◽  
Pilot Fuel ◽  
Fuel Injection Pressure

Abstract Methanol fueled internal combustion (IC) engines have attracted significant attention due to their contributions in reducing environmental pollution and fossil fuel consumption. In this study, a single-cylinder research engine was operated on MD10 (10% (v/v) methanol blended with mineral diesel) and baseline mineral diesel to explore an optimized fuel injection strategy for efficient combustion and reduced emissions. The experiments were conducted at constant engine speed (1500 rpm) and load (3 kW) using two different fuel injection strategies, namely, single pilot injection (SPI) and double pilot injection (DPI) strategy. For each pilot fuel injection strategy, the start of main injection (SoMI) timing was varied from −3 to 6° crank angle (CA) before top dead center (bTDC). To examine the effect of fuel injection pressure (FIP), experiments were performed at three different FIPs (500, 750, and 1000 bars). Results showed that the MD10 fueled engine resulted in superior combustion compared with baseline mineral diesel, which was further improved by DPI at higher FIPs. The use of DPI strategy was found to be more effective at higher FIPs, resulting in higher brake thermal efficiency (BTE), lower exhaust gas temperature (EGT), and reduced oxides of nitrogen (NOx) emissions compared with SPI strategy. Detailed investigations showed that the addition of methanol in mineral diesel reduced particulates, especially the accumulation mode particles (AMP). Different statistical analysis and qualitative correlations between fuel injection parameters showed that higher FIP and advanced SoMI timings were suitable for particulate reduction from the MD10 fueled engine.

Numerical Study on Proppant Transport in Hydraulic Fractures Using a Pseudo-3D Model for Multilayered Reservoirs

SPE Journal ◽  
2021 ◽  
pp. 1-16
Author(s):  
Xi Zhang ◽  
Lifeng Yang ◽  
Dingwei Weng ◽  
Zhen Wang ◽  
Robert G. Jeffrey
Keyword(s):  
Hydraulic Fracture ◽  
Transport Model ◽  
Numerical Study ◽  
Soft Rock ◽  
Injection Pressure ◽  
Field Measurements ◽  
Fracture Plane ◽  
Hydraulic Fractures ◽  
Fracture Aperture ◽  
Proppant Transport

Summary In this paper, we incorporated a kinematic proppant transport model for spherical suspensions in hydraulic fractures developed by Dontsov and Peirce (2014) in a pseudo-3D hydraulic-fracture simulator for multilayered rocks to capture a different proppant transport speed than fluid flow and abridged fracture channel by highly concentrated suspensions. For pressure-driven proppant transport, the bridges made of compact proppant particles can lead to both proppant distribution discontinuity and increased fracture aperture and height because of the higher pressure. The model is applied to growth of a fracture from a vertical well, which can contain thin-bedded intervals and more than one opened hydraulic-fracture interval, because the fracture plane extends in height through layers with contrasts in stress and material properties. Three numerical examples demonstrate that a loss of vertical connectivity can occur among multiple fracture sections, and proppant particles are transported along the more compliant layers. The proppant migration within a narrow fracture in a thin soft rock layer can result in bridging and formation of a proppant plug that strongly limits fluid speed. This generates an increase of injection pressure associated with fracture screenout, and these screenout events can emerge at different places along the fracture. Next, because of the lack of pretreatment geomechanical data, the values of layer stress and leakoff coefficient are adjusted for a field case so that the varying bottomhole pressure and fracture length are in line with the field measurements. This paper provides a useful illustration for hydraulic-fracturing treatments with proppant transport affected by and interacting with reservoir lithological complexities.

scholarly journals Effect of Intake Air Temperature, Pressure And Fuel Injection Pressure On Low Temperature Combustion (LTC) Engine BY Using Dual Injection Strategy For Pollution Reduction

2021 ◽  
Author(s):  
Bharathiraja Moorthy ◽  
Nithyanandhan Kamaraj ◽  
Somasundaram Periasamy ◽  
Saji Raveendran Padmavathy ◽  
Gaurav Dwivedi ◽  
...  
Keyword(s):  
Air Temperature ◽  
Thermal Efficiency ◽  
Fuel Injection ◽  
Injection Pressure ◽  
Vital Role ◽  
Low Temperature Combustion ◽  
Injection Strategy ◽  
Dual Injection ◽  
Treatment Measures ◽  
Fuel Injection Pressure

Abstract Starting from the invention of engines, automobiles require engines for their application. Even though several alternatives have been proposed like fuel cells, engines play the vital role in the automobile sector. In this scenario, the emissions coming out from the engine contributes to the global air pollution at an unbelievable rate. This led the government to enforce strict emission regulations on automobiles. To achieve those regulations several ideas have been proposed so far, which are generally classified into two categories as in-cylinder measures and after-treatment measures. But the thing is after-treatment measures are too costly and also it mainly depends on combustion rate. So obviously in-cylinder controls will be the potential area for the research. Automobile sector not only focused on emissions; it also wants high thermal efficiency in engine. Due to high thermal efficiency and good fuel economy diesel engines are the favorite one in automobiles. But it emits NOx and PM at higher rate. To overcome this issue low temperature combustion (LTC) concept is introduced, added to the objective it can also maintain high thermal efficiency as like as diesel combustion. The problem regarding to LTC are combustion phasing control, transient operations, limited operating range and mainly it contributes to HC and CO emissions while concentrating on reduction of NOx and PM. In the present work, control emissions and combustion phasing of LTC combustion concept by dual injection strategy was studied and the effect of fuel injection pressure, intake air temperature and pressure also studied. The project was done only on partial load with diesel as fuel. Late injection strategy of LTC was used. Results shown that compared to single injection strategy, thermal efficiency was improved by dual injection strategy. Pilot injection timing and mass fraction played a vital role in controlling emissions and improving thermal efficiency. In all intake air temperature, if fuel injection pressure increase result in increase of thermal efficiency, NO emission and decrease of smoke, CO and HC emissions. Likewise in all intake air temperature and fuel injection pressure, if Intake air pressure increase result in increase of thermal efficiency, smoke and decrease of NO, HC and CO emissions. Maximum Indicated thermal efficiency achieved was 38% which was 8% higher than base readings. Lowest NO emission achieved was 187 ppm, that was 68% less than base reading. Lowest smoke achieved was 3% of opacity, which was 75% less than base reading. An overall comparing result, optimized fuel injection pressure is 600 bar, intake air temperature is 310 K, intake air pressure is 107 kPa. At that condition, smoke reduced to 23%, NO reduced to 63%, CO reduced to 75% and indicated thermal efficiency increased to 4% compare to base readings.

scholarly journals Temporal Evolution of Split-Injected Fuel Spray at Elevated Chamber Pressures

Energies ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 4284 ◽  
Author(s):  
Gang Wu ◽  
Xinyi Zhou ◽  
Tie Li
Keyword(s):  
High Speed ◽  
Fuel Injection ◽  
Penetration Rate ◽  
Injection Pressure ◽  
Test System ◽  
Injection Rate ◽  
Spray Angle ◽  
Split Injection ◽  
Injection Strategy ◽  
Injection Strategies

For reducing soot and NOx emissions, an effective method is to apply split injection strategies. In this research, characteristics of split injection were investigated by applying the pilot-main injection strategy and main-post injection strategy. The injection mass of fuel with the two strategies was measured by an in-house fuel injection rate test system based on the Bosch method. The development of spray tip and tail penetrations, as well as the evolvement of the spray angle when applying these two injection strategies, were explored by employing the high speed shadowgraphy at various injection pressures and surrounding gas densities. The results indicate the tail penetration rate of spray has no relation to the fuel injection pressure. However, the increased injection pressure causes a faster penetration development in the spray tip position. It was also found that the spray tip penetration rate of the second spray is slightly slower than that of the first spray at the beginning stage of injection, but it was significantly larger than the first one at the later stage.

scholarly journals Application of bacteria in concrete: a critical evaluation of the current status

2016 ◽  
Vol 1 ◽  
pp. 56 ◽  
Author(s):  
Nele De Belie
Keyword(s):  
Concrete Strength ◽  
Critical Evaluation ◽  
Current Status ◽  
Carbonate Precipitation ◽  
Self Healing ◽  
Calcium Carbonate Precipitation ◽  
Healing Efficiency ◽  
New Strategy ◽  
Concrete Elements ◽  
Urea Decomposition

Microbially induced carbonate precipitation has been tested over more than a decade as a technique to enhance concrete properties. Mainly bacteria following the pathways of urea decomposition, oxidation of organic acids, or nitrate reduction have been studied for this purpose. For bacteria mixed into fresh concrete, it is difficult to prove that they actively contribute to calcium carbonate precipitation and the effects on concrete strength are variable. Application of bacteria for surface consolidation has been shown to reduce water absorption and increase durability. Microbial self-healing of cracks in concrete shows promising results at the laboratory scale. Especially the use of self-protected mixed cultures opens perspectives for practical application. However, their self-healing efficiency needs to be further proven in larger concrete elements, and under non-ideal conditions. The use of denitrifying cultures for concurrent self-healing and production of corrosion inhibiting nitrites is a promising new strategy.

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