Increase Engine Efficiency Research Articles

DEVELOPMENT OF BOOST SYSTEMS FOR FORCED DIESEL ENGINES

The paper analyzes the world experience in boosting diesel engines by improving the air supply system, i.e. the installation of drive superchargers and (turbochargers) TKR. Two main types of mechanical superchargers, rotary and centrifugal, are considered. The most common models of rotatory superchargers, Roots, Eaton and Lysholm, the scheme and principle of operation of centrifugal superchargers are analyzed. The main disadvantage of mechanical supercharging is that all the power needed to compress the air is taken from the engine crankshaft. Therefore, gas turbine supercharging is considered the most promising. Single-stage boost systems are analyzed using the example of well-known car manufacturers such as Pegaso and Volkswagen. It has been established that the use of turbocharging increases engine efficiency, which leads to a decrease in specific effective fuel consumption. The further development is aimed at improving single-stage turbocharging systems, reducing the size of turbochargers, reducing inertia, using turbine controls and using two-stage boost systems. In addition, an analysis is made of the work of well-known companies developing boost systems (ABB Turbo Systems, MTU, MAN, Borg Warner Turbo System), which showed that for diesel engines with a liter capacity of more than 60 kW / l it is rational to use a two-stage boost system with intermediate cooling of the charge air. The advantages of using a two-stage boost system are: high torque at low engine speeds; increase in rated power; increase in boost pressure; reduction in fuel consumption; smoke reduction; high potential to reduce NOx emissions; improved transient characteristics. The use of a two-stage controlled turbocharging with cooling of the charge air type R2S achieves a high average effective pressure. Depending on the setting, the system can be implemented both at low and high engine speeds.

The Virtual Engine Development for Enhancing the Compression Ratio of DISI-Engines Combining Water Injection, Turbulence Increase and Miller Strategy

<div class="section abstract"><div class="htmlview paragraph">The increase in efficiency is the focus of current engine development by adopting different technologies. One limiting factor for the rise of SI-engine efficiency is the onset of knock, which can be mitigated by improving the combustion process. HCCI/SACI represent sophisticated combustion techniques that investigate the employment of pre-chamber with lean combustion, but the effective use of them in a wide range of the engine map, by fulfilling at the same time the need of fast load control are still limiting their adoption for series engine. For these reasons, the technologies for improving the characteristics of a standard combustion process are still largely investigated. Among these, water injection, in combination with the Miller cycle, offers the possibility to increase the knock resistance, which in turn enables the rise of the engine geometric compression ratio.</div><div class="htmlview paragraph">The need for reducing measurements and executing specific tests are mandatory to make still the IC-Engines competitive to other powertrain solutions. The implementation of water injection can be realized through different engine layouts and injection strategies. Besides, the results of injecting water are strictly dependent on the base engine features and load point. Therefore, virtual development becomes essential to study many engine configurations.</div><div class="htmlview paragraph">In this work, indirect and direct water injection strategies are considered to increase the engine knock limit. The investigation is conducted with the 3D-CFD-Tool QuickSim, which was developed at IVK/FKFS Stuttgart. The implementation of water physics, the extension of simulation domain up to full engine (including intake and exhaust system), and the possibility to analyze multiple cycles allow understanding the effects of water and valve timing on engine behavior. The simulation validation was accomplished through the experiments carried out on a single-cylinder engine, equipped with indirect and direct water injections. The set-up of a virtual test bench is exploited to increase the engine geometric compression ratio, by combining Miller valve timing strategies with water injection. Particularly the investigation of a water-optimized injector targeting and position for the direct water injector enables increasing the turbulence within the cylinder and compensating for the effect of early intake valve closure. With the support of a newly developed knock model, the effect of water and the modified valve overlap on the combustion process is analyzed, to increase engine efficiency and propose a new approach for future powertrain engine development process.</div></div>

Reactive computational fluid dynamics modelling of methane–hydrogen admixtures in internal combustion engines: Part I – RANS

The effects of hydrogen addition to internal combustion engines operated by natural gas/methane has been widely demonstrated experimentally in the literature. Already small hydrogen contents in the fuel show promising benefits with respect to increased engine efficiency, lower CO2 emissions, extended lean operating limits and a higher exhaust gas recirculation tolerance while maintaining the knock resistance of methane. In this article, the influence of hydrogen addition to methane on a spark ignited single cylinder engine is investigated. This article proposes a modelling approach to consider hydrogen addition within three-dimensional reactive computational fluid dynamics in order to establish a framework to gain further insights into the involved processes. Experiments have been performed on a single-cylinder spark-ignition engine situated at a test bed and cater as reference data for validating the proposed reactive computational fluid dynamics modelling approach based around the G-Equation combustion model. Within the course of the first part, crucial aspects relevant to the modelling of the mean engine cycle are highlighted. In this article, a simplified early combustion phase model which considers the transition towards a fully developed turbulent flame following ignition is introduced, along with a second submodel considering combined effects of the walls. The sensitivity of the combustion process towards the modelling approach is presented. The submodels were calibrated for a reference operating point, and a sweep in hydrogen content in the fuel as well as stoichiometric and lean operation has been considered. It is shown that the flame speed coefficient A appearing in the used turbulent flame speed closure, weighting the influence of the turbulent fluctuating speed [Formula: see text], has to be adjusted for different hydrogen contents. The introduced submodels allowed for significant improvement of the in-cylinder pressure and heat release rate evolution throughout all considered operating conditions.

Propulsive modelling for JT9D-3, JT15D-4C and TF-30 turbofan engines using particle swarm optimization

Purpose The purpose of this paper is to create high-accuracy thrust modelling for cruise flight using particle swarm optimization (PSO) algorithm. Design/methodology/approach In this study, using PSO, new thrust models with high accuracy for the cruise flight stages of Pratt & Whitney JT9D-3, JT15D-4C and TF-30 engines were created. For this aim, real Mach number, flight altitude and thrust values taken from the engine manufacturers were used. In the model, thrust is given as a function of altitude and Mach number. The sensitivity of the results given by the PSO thrust model has been examined using several different error types. Finally, the effect of some PSO parameters on the created models is examined. Findings It was observed that the model created predicted real thrust values with high precision. Practical implications The PSO thrust model can be used in the trajectory estimates of today’s aircraft with the use of accurate scaling factors. In addition, using the developed PSO thrust model together with a correct aerodynamic model provides more effective management of air traffic flow in air traffic management applications. Combining the PSO model with fuel flow-rate models will significantly increase engine efficiency and performance; thus, making a major contribution to reducing engine emissions. Originality/value The originality of this study is that it is the first thrust modelling made with PSO in the literature for turbofan engines. The use of real data in the study and the creation of models for several different turbofan engines are important for the reliability of thrust models.

Thermoelectric power generations from vehicle exhaust gas with TiO2 nanofluid cooling

Vehicle engine efficiency is considered low by approximately 30% only. More than half of the fuel energy from the engine is lost in exhaust piping and dissipated through cooling systems. One alternative approach to increase engine efficiency is by utilizing the waste heat recovery system that emphasizes on the conversion from heat to electrical energy. This is possible with the use of a thermoelectric generator (TEG). The challenges of using a TEG in the heat exchanger application is due to its low thermal conversion efficiency and low power output. To increase the efficiency of TEG, the nanofluid cooling, specifically titanium oxide (TiO2), was introduced into the system. Nanofluids have been tested in the past in many heat exchanger applications and have shown heat transfer improvements. This study had conducted testing using a TEG set-up that connected to a vehicle exhaust system. The TiO2-water nanofluid functioned as a cooling medium to remove the heat from the TEG cold surface. Engine speed in idling conditions varied during the testing between 700 and 1500 RPMs. This project aimed to investigate and conduct an experiment on TEG power generation using waste heat from vehicle exhaust gas with TiO2-water cooling. The experiment objective was to assess the effectiveness of TiO2-water nanofluids cooling, and its effect on the TEG power output and efficiency. TiO2 has positively enhanced TEG thermal conversion and electrical power output when compared to water cooling, through various engine speeds.

Ceramic Composite Materials Obtained by Electron-Beam Physical Vapor Deposition Used as Thermal Barriers in the Aerospace Industry.

This paper is focused on the basic properties of ceramic composite materials used as thermal barrier coatings in the aerospace industry like SiC, ZrC, ZrB2 etc., and summarizes some principal properties for thermal barrier coatings. Although the aerospace industry is mainly based on metallic materials, a more attractive approach is represented by ceramic materials that are often more resistant to corrosion, oxidation and wear having at the same time suitable thermal properties. It is known that the space environment presents extreme conditions that challenge aerospace scientists, but simultaneously, presents opportunities to produce materials that behave almost ideally in this environment. Used even today, metal-matrix composites (MMCs) have been developed since the beginning of the space era due to their high specific stiffness and low thermal expansion coefficient. These types of composites possess properties such as high-temperature resistance and high strength, and those potential benefits led to the use of MMCs for supreme space system requirements in the late 1980s. Electron beam physical vapor deposition (EB-PVD) is the technology that helps to obtain the composite materials that ultimately have optimal properties for the space environment, and ceramics that broadly meet the requirements for the space industry can be silicon carbide that has been developed as a standard material very quickly, possessing many advantages. One of the most promising ceramics for ultrahigh temperature applications could be zirconium carbide (ZrC) because of its remarkable properties and the competence to form unwilling oxide scales at high temperatures, but at the same time it is known that no material can have all the ideal properties. Another promising material in coating for components used for ultra-high temperature applications as thermal protection systems is zirconium diboride (ZrB2), due to its high melting point, high thermal conductivities, and relatively low density. Some composite ceramic materials like carbon–carbon fiber reinforced SiC, SiC-SiC, ZrC-SiC, ZrB2-SiC, etc., possessing low thermal conductivities have been used as thermal barrier coating (TBC) materials to increase turbine inlet temperatures since the 1960s. With increasing engine efficiency, they can reduce metal surface temperatures and prolong the lifetime of the hot sections of aero-engines and land-based turbines.

Performance Characteristics of VCR Engine by Adding Waste Plastics Oil to Diesel

The waste plastics are collected at India in every year nearly 10 tons per day. The waste plastic has affects the humans being, house animals, birds and see foods earth and environment. The period of plastic decay may be taking nearly 1000 years. These waste plastics are used for filling purpose, or it may dump in back water area and ocean. But this technology process is recycling of these all type waste plastic in pyrolysis method. The pyrolysis methods the waste plastics are to heating the waste material in the vacuum chamber. In this study state condition 650 Celsius temperature need for melting and vaporizing. It condensed to make a fuel from waste plastics. It works like conventional fuel. This type of system can helping to reduced amount of waste plastic and can be provide 60% oil for gasoline to vehicles. The fuel does not emit any emission gases. It increases engine efficiency. This will be residue 5% of carbon block. The plastic oil will be mixed with diesel in some percentage like 5%, 10%, 20% and added with some additives, this additive is increase the engine performance, combustion characteristics and reduce emission. By making the use of pyrolysis technique, the levels of smoke is reduced which is verified by the experimental results. Brake Thermal Efficiency (BTE) also high when compared convention fuel. The pollutants such as carbon monoxide and NOx are presented in the waste plastic which is reduced by the proposed methods and it is observed that addition of oxygenates enhanced the combustion process

High Efficiency by Miller Valve Timing and Stoichiometric Combustion for a Naturally Aspirated Single Cylinder Gas Engine

<div class="section abstract"><div class="htmlview paragraph">Small-scale cogeneration units (P<sub>el</sub> < 50 kW) frequently use lean mixture and late ignition timing to comply with current NO<sub>x</sub> emission limits. Future tightened NO<sub>x</sub> limits might still be met by means of increased dilution, though both indicated and brake efficiency drop due to further retarded combustion phasing and reduced brake power. As an alternative, when changing the combustion process from lean burn to stoichiometric, a three-way-catalyst allows for a significant reduction of NO<sub>x</sub> emissions. Combustion timing can be advanced, resulting in enhanced heat release and thus increased engine efficiency.</div><div class="htmlview paragraph">Based on this approach, this work presents the development of a stoichiometric combustion process for a small naturally aspirated single cylinder gas engine (P<sub>el</sub> = 5.5 kW) originally operated with lean mixture. To ensure low NO<sub>x</sub> emissions, a three-way-catalyst is used. In order to achieve high engine efficiency, measures implemented include Miller valve timing, optimized intake system, reduced engine speed and increased compression ratio. In the first step, a detailed 1D engine cycle simulation model was used to investigate the efficiency benefit of Miller valve timing and increased compression ratio. Within the numerical study, inlet valve closing timing and intake pipe length were varied, yet a closed-loop control was implemented to maintain a constant effective compression ratio of 14.66 by adjusting geometrical compression ratio for each configuration. Subsequently, the most expedient valve timing was designed using multi-body simulation of the inlet valve train, while increased compression ratio was achieved by modifying the series piston bowl geometry.</div><div class="htmlview paragraph">Engine trials agree with simulation results and show highest efficiency for a Miller valve timing closing +15 °CA later to the series valve timing and geometrical compression ratio of 15.36. Compared to the series lean burn engine, indicated and brake efficiency increase by 3.2 %-points to 39.0 % and by 3.9 %-points to 34.4 %, respectively, while maintaining original brake power of P<sub>e</sub> = 6.1 kW. Finally, an experimental study accompanied by 3D-CFD simulations was conducted to investigate the potential of optimized piston geometry to further increase efficiency. However, results reveal only minor effect of piston geometry on efficiency, what is likely stemming from interrelation of combustion efficiency, wall heat losses and heat release rate.</div></div>

Multiple Combustion Stages Inside a Heavy-Duty Diesel Engine Retrofitted to Natural-Gas Spark-Ignition Operation

Abstract Converting existing diesel engines to natural-gas (NG) spark-ignition (SI) operation can reduce the dependence on oil imports and increase energy security. NG-dedicated conversion can be achieved by the addition of a gas injector in the intake manifold and of a spark plug in place of the diesel injector. Previous studies indicated that lean-burn NG inside the traditional diesel chamber (i.e., a bowl-in-piston geometry) is a two-stage combustion (i.e., a fast burn inside the bowl followed by a slower burn inside the squish). However, a triple-peak apparent heat release rate (AHRR) was seen at specific operating conditions (e.g., advanced spark timing (ST) at medium load and engine speed), suggesting that one of the two combustion stages may separate again. Specifically, the burn inside the squish region divided in two events before and after top dead center (TDC). This was due to the different flow motion inside the squish during the compression stroke compared to the one in the expansion stroke, which affected the combustion environments. The result was the apparition of two close peaks in pressure trace, which suggest larger gradients in pressure and temperature than at a more delayed ST. In addition, the phasing and magnitude of three peaks of the heat release changed cycle-to-cycle. As an advanced ST is the usual strategy used in lean-burn SI combustion, understanding phenomena such as the one presented here can be important for reducing engine-out emissions and increase engine efficiency.

Research and design of grid connection and waste heat utilization of marine generating units

This work is based on the use of waste heat from the temperature difference semiconductor heat exchanger, which can effectively use the waste heat in the exhaust gas, and convert it into electrical energy output through the temperature difference semiconductor material, which can increase engine efficiency and reduce energy consumption; at the same time, it can reduce engine noise and vibration. Extended service life. Due to the strong electromagnetic interference and severe vibration of the generator, there are few remote control devices on the market for the generator. This project uses a 2.4G wireless communication module to control the frequency conversion and speed regulation of the generator. In order to save manpower, start remotely, stop as soon as possible, monitor the operating status of the waste heat temperature difference power generation, reasonably replace the power, start quickly, and reach the electromechanical Integrated product. The realization of intelligent frequency conversion technology can adjust the engine speed according to different electrical appliances, adapt to external loads, realize automatic voltage adjustment, and save fuel consumption. The grid-connected system solves the frequency and phase problems of generators of different models, generations, and manufacturers in parallel, and realizes the re-mixing of old generators, which greatly improves the service life of engines and the best power generation supply, and reduces power generation systems and storage. The configuration cost of the energy unit improves the comprehensive utilization rate of the equipment, has a higher working efficiency, has good economic benefits, and can achieve the purpose of energy saving and emission reduction.

Emission analysis of CuO2 nanoparticle addition with blend of Botryococcus braunii algae biodiesel on CI engine

The energy crisis is due to two reasons: one is the rapid growth of the global human population, and the other is the transformation of the residing human style. Traditional fuel is also a major component of adding pollutants to the environment. Changes in fuel consumption play a major role in increasing engine efficiency and reducing emissions.In the current research, fuel changes in the diesel engine were developed. The single-cylinder diesel engine was initially equipped with Botryococcus braunii algae oil methyl ester and its diesel blends with CuO2 nano additives B20, B20 + 25 ppm, B20 + 50 ppm, B20 + 75 ppm, B20 + 100 ppm at different loads at steady engine speed. From the experimental analysis, it has been shown that B20 is the more efficient fuel ratio than other blends. The results showed a significant reduction in CO, HC and smoke emissions. The current analysis shows that BBAME's biodiesel with CuO2 nano additives is best suited as an alternative diesel engine fuel.

Combustion analysis of CuO2 nanoparticle addition with blend of botryococcus braunii algae biodiesel on CI engine

The energy crisis is attributed to two reasons: one is the rapid growth of the global human population and the other is the evolution of the human lifestyle. Modern oil is also a key component in introducing contaminants to the atmosphere. Changes in fuel consumption play a key role in increasing engine efficiency and reducing emissions. In the current research, fuel changes in the diesel engine were developed. The single-cylinder diesel engine was initially equipped with botryococcus braunii algae oil methyl ester and its diesel blends with CuO2 nano additives B20, B20 + 25 ppm, B20 + 50 ppm, B20 + 75 ppm, B20 + 100 ppm at different loads at steady engine speed. From the experimental analysis, it has been shown that B20 is the more efficient fuel ratio than other blends. The results showed a significant reduction in CO, HC and smoke emissions. The current analysis shows that BBAME's biodiesel with CuO2 nano additives is best suited as an alternative diesel engine fuel.

Performance study of the hypocycloid gear mechanism for internal combustion engine applications

Fuel conversion efficiency is one of the main concerns in the field of internal combustion engine systems. Although the Otto cycle delivers the maximum efficiency possible in theory, the kinematics of the slider–crank mechanism of the conventional internal combustion engines makes it difficult to reach this level of efficiency in practice. This study proposes using the unique hypocycloid gear mechanism instead of the conventional slider–crank mechanism for the internal combustion engines to increase engine efficiency and minimize frictional power losses. The hypocycloid gear mechanism engine’s kinematics provides the means for the piston-rod assembly to reciprocate in a straight-line motion along the cylinder axis besides achieving a nonlinear rate of piston movement. As a result, this characteristic allows for a true constant-volume combustion, which in turn would lead to higher work output. An in-cylinder gas volume change model of the hypocycloid gear mechanism engine was developed and incorporated into the thermodynamic model for the internal combustion engine cycle. The thermodynamic model of the hypocycloid gear mechanism engine was developed and simulated using MATLAB/Simulink software. A comparison between the conventional engine and the hypocycloid gear mechanism engine in terms of engine performance characteristics showed the enhancements achieved using hypocycloid gear mechanism for internal combustion engine applications. The hypocycloid gear mechanism engine analysis results indicated higher engine efficiency approaching that of the Otto cycle.

Rapid Prototyping for Optimization of the Charge Motion in Internal Combustion Engines Driven by Sewage Gas

Abstract This paper presents a newly developed method using rapid prototyping (RP) to develop gas engine cylinder heads with optimized charge motion characteristics to adapt to lean-burn and Miller combustion process requirements. The geometry in close vicinity to the inlet valve seats was designed to increase swirl and flow performance of the cylinder heads. A three-dimensional (3D) printer was used to realize a rapid prototyping concept for the testing of multiple designs; the effects of the different designs were measured using a static flow test bench and a laser-optical method to visualize the flow patterns. The results of the static flow bench tests showed potentially higher flow and swirl performance, with one high-swirl version proving beneficial specifically for lean-combustion and one high-flow version matching the Miller combustion requirements. The two cylinder head versions were then manufactured and the lean-combustion version was tested for on-engine performance on a 150 kW sewage-gas driven lean-combustion engine. It has been shown that the cylinder head generates higher swirl on the test bench but achieves only a slight increase in combustion speed on the test engine. The potential to increase engine efficiency by intensifying swirl is, therefore, considered exploitable. Research has further shown the coefficient of variance (CoV) was reduced by 0.3–1.2%. Charge exchange losses have also been demonstrated to decrease at all tested engine settings. It has further been found that higher swirl intensity has a positive impact on engine emission levels, as the engine out carbon monoxide (CO) emission can be reduced by approximately 70 mg·m−3.

Autoignition behavior of a full boiling-range gasoline: Observations in RCM and GCI engine environments

The understanding of, and capability to modulate fuel autoignition behavior are important aspects towards the development of advanced, low temperature combustion (LTC) engine concepts, which have potential to significantly increase engine efficiency while at the same time addressing emissions concerns. Proper combustion phasing and control of heat release rates via, for instance, multiple injections and exhaust gas recirculation, are significant challenges that can vary with fuel composition. Overall reactivity, which is a strong function of the in-cylinder temperature and pressure, is a prime driver for regulating combustion timing, while preliminary exothermicity, in the form of low- and intermediate-temperature heat release (LTHR, ITHR) can inhibit, or facilitate operational success, e.g., control combustion phasing. There are still gaps in understanding these features and how they interact with needs of advanced combustion engines, and how practical fuels can be rated for the new challenges of LTC engines.This work utilizes a rapid compression machine (RCM) and gasoline compression ignition (GCI) engine to probe the autoignition behavior of a California Reformulated Gasoline Blendstock for Oxygenate Blending (CARBOB) (RON = 86, MON = 81.4) under quasi- homogeneous charge compression ignition (qHCCI) operation. A wide range of thermodynamic conditions is explored (Tc = 700–1000 K, Pc = 15–90 bar) where ignition delay times and LTHR/ITHR are quantified. Both stoichiometric, dilute (11% O2) and lean (equivalence ratio (ϕ) = 0.23) fuel loading conditions are considered. The GCI engine is operated under fuel-lean conditions (ϕ = 0.23) using no external exhaust gas recirculation over a range of intake temperature (Tin = 30–70 °C), with the intake pressure adjusted (Pin = 1.2–1.3 bar) to achieve constant combustion phasing (CA50 = −4 °aTDC). Preliminary exothermicity is also quantified under these conditions.The stoichiometric, dilute RCM measurements reveal negative temperature coefficient (NTC) behavior for this fuel and indicate that rates and extents of LTHR and ITHR are both affected by the compressed conditions, with temperature imposing an inverse dependence, while increased pressure causes LTHR to increases, but ITHR to decrease. These are the first experimental quantifications of ITHR trends for a practical fuel under well-controlled, static conditions. When the lean RCM measurements are mapped to the in-cylinder conditions of the engine, it is found that under a constant combustion phasing scenario (as used in the engine), the fuel has little overall temperature sensitivity, while the starts of high temperature heat release (soHTHR) and top dead center (TDC) points seen along the engine compression trajectories correspond to isopleths of ignition delay times τRCM = 6 and 3 ms, respectively. In addition, the points of peak LTHR rate in the engine correspond to an isopleth of first-stage ignition τ1,RCM = 0.50–0.75 ms. Correlating the magnitudes of LTHR and ITHR measured in the RCM to the engine requires quantification of the preliminary exothermicity at the thermodynamic conditions of peat LTHR rate and soHTHR, respectively. The current measurements demonstrate how fundamental data from an RCM can be used to project expected trends in overall fuel reactivity to a qHCCI engine environment, and thus provide a possible avenue for characterizing fuels for LTC engines.

2-Stroke Scavenging in Conventional and Minimally-Modified 4-Stroke Engines for Heavy Duty Applications at Low to Medium Speeds

The transformation of a standard 4-stroke cylinder head into a torque-improved and gradually more efficient 2-stroke design is discussed. The concept with an effective loop scavenging via an extended inlet valve holds promise for engines at low- to medium-rotational speeds for typical designs of conventional 4-stroke cylinder heads. Calculations, flow simulations, and visualizations of experimental flows in relevant geometries and time scales indicate feasibility, followed by a small engine demonstration. Based on presumably long-forgotten and outdated patents, and the central topic of this contribution, an additional jockey rides on the inlet valve’s disk (facing away from the combustion chamber) and reshapes the in-cylinder flow into a reverted tumble. A quick gas exchange with a well-suppressed shortcut into the open exhaust is approached. For overall mechanical efficiency, the required charge pressure for scavenging is of paramount importance due to the short scavenging time and the intake’s reduced cross-section. Herein, still acceptable charging pressures are reported for scavenging periods equivalent to low or medium rotational speeds, as characteristic for heavy-duty applications. Using widely available components (charger, direct injection, variable camshaft angles) an increased engine efficiency is suggested due to the 2-stroke’s downsizing effect (relatively less internal friction as well as the promise of more torque and a decreased size).

Solidification of niobium-silicide-based alloys during laser additive manufacturing process

Niobium silicide-based composites, in the application of gas turbine blades, promise significant efficiency improvements compared to current Ni-based alloys. The higher temperature capability would allow the engine to run at a higher temperature than that of current alloys, increasing engine efficiency. Nb-Si based composites possess a lower density, due to the presence of ceramic phases such as Nb5Si3 and/or Nb3Si. This would reduce the weight of the rotating blades. However, improvements in certain properties, such as room temperature toughness and oxidation resistance are needed.This study focuses on the manufacturability aspect of the powder feeding laser additive manufacturing (LAM) process to engineering Nb-Si based alloy samples. LAM has the advantage of forming near-net shapes without the use of expensive cores and moulds for the reactive Nb-Si melt. Fine microstructure and even chemical composition distribution with reduced macro-segregation are obtained. With the use of power feeding system, new Nb-Si based alloys are LAMed with varying atomic composition. Microstructures of the LAMed alloys will be presented, and the relationship between the microstructure and the alloy chemistry will be reported.

Novel Spring-Buffered Variable Valve Train for an Engine Using Magneto-Rheological Fluid Technology

Vehicle manufacturers have been attempting to increase engine efficiency and decrease pollution through various methods. Variable valve actuation technology is one of these methods. Several mechanisms have been established already and have been used to develop this technology. However, these systems have common problems such as complex design, large volume, low response rate, and high-energy consumption. In this study, a novel variable valve actuation device that is compact and requires less energy was developed using magnetorheological (MR) fluid technology. The main components used in this device are an MR valve, passive buffer spring, cam, and rocker arm. This study was divided into three parts. First, an MR valve train was designed. This valve train can be constructed easily, and has fewer hydraulic and mechanical components and consumes less energy than other technologies. Second, the magnetic plate block design was optimized to obtain the required control force at optimal volume and energy. Finally, dynamical simulations pertaining to the springs and the structure were executed to analyze the dynamic condition of the valve. The simulation results indicated that the proposed MR valve could effectively provide functions of variable valve timing and variable valve lift by dynamically controlling the external current in the magnetic coil.

Cyclic Ketones as Future Fuels: Reactivity with OH Radicals.

For a sustainable energy future, research directions should orient toward exploring new fuels suitable for future advanced combustion engines to achieve better engine efficiency and significantly less harmful emissions. Cyclic ketones, among bio-derived fuels, are of significant interest to the combustion community for several reasons. As they possess high resistance to autoignition characteristics, they can potentially be attractive for fuel blending applications to increase engine efficiency and also to mitigate harmful emissions. Despite their importance, very few studies are rendered in understanding of the chemical kinetic behavior of cyclic ketones under engine-relevant conditions. In this work, we have conducted an experimental investigation for the reaction kinetics of OH radicals with cyclopentanone and cyclohexanone for the first time over a wide range of experimental conditions ( T = 900-1330 K and p ≈ 1.2 bar) in a shock tube. Reaction kinetics was followed by monitoring UV laser absorption of OH radicals near 306.7 nm. Our measured rate coefficients, with an overall uncertainty (2σ) of ±20%, can be expressed in Arrhenius form as (in units of cm3 molecule-1 s-1): (902-1297 K); (935-1331 K). Combining our measured data with the single low-temperature literature data, the following three-parameter Arrhenius expressions (in units of cm3 molecule-1 s-1) are obtained over a wider temperature range: k1(CPO + OH) = (298-1297 K); (298-1331 K). Discrepancies between the theoretical and current experimental results are observed. Earlier theoretical works are found to overpredict our measured rate coefficients. Interestingly, these cyclic ketones exhibit similar reactivity behavior to that of their linear ketone counterparts over the experimental conditions of this work.

Laser metal deposition strategies for repairing flat and notched substrates made of Ni-based single crystalline superalloys

Laser metal deposition, or laser cladding, has been applied to repair and manufacture turbine blades as well as other superalloy components. In some cases, these applications can lower parts manufacturing and maintenance costs, or even increase engine efficiency; therefore, they attract considerable interest from the aerospace industry. However, the single crystalline (SX) repair of Ni-based superalloy parts is still a technology under development. Recent works aimed to understand the solidification phenomena present in a laser-formed melt pool or to achieve SX depositions through epitaxial solidification computational modeling. Here, to attain high SX depositions on flat and notched substrates without the need of such sophisticated methods, a previously developed design of experiments (DoE) for laser remelting was used to produce SX clad tracks. New data related to this DoE are presented, describing its characteristics and possible improvement. Furthermore, a remolten clad track extracted from the DoE was used as a basis to three cladding strategies applied on flat (010) substrates. From such depositions, one strategy was chosen to also be applied on a (110) substrate, yielding insights on the interaction between substrate orientation, cladding strategy, and track parameterization adequacy. The depositions were evaluated through electron backscatter diffraction mapping and profiling, as well as oriented-to-misoriented observation. Finally, the clad tracks’ disposition of a successful SX deposition was used to determine a notch profile. The notch profile was then machined into a substrate, simulating a crack repair, and filled accordingly. This extrapolation from flat to notch was based on simple geometrical considerations and resulted in an SX notch fill. Therefore, showing evidence that the sequence of considerations taken is a promising approach to define notch geometry for SX repair. The cladding strategies evaluated, the verified DoE, and the approach taken for notch filling may be of use to researchers and engineers when planning more sophisticated procedures that aim the repair of Ni-based SX components.