Increase Engine Performance Research Articles

Dynamic Response of a Metal and a CMC Turbine Blade During a Controlled Rub Event Using a Segmented Shroud

Ceramic matrix composites (CMCs) provide several benefits over metal blades including weight and increased temperature capability, and have the potential for increased engine performance by reduction of the cooling flow bled from the compressor and by allowing engines to run at higher turbine inlet temperatures. These CMC blades must be capable of surviving fatigue (high cycle and low cycle), creep, impact, and any tip rub events due to the engine missions or maneuvers that temporarily close blade tip/shroud clearances. As part of a cooperative research program between GE Aviation and the Ohio State University Gas Turbine Laboratory, OSU GTL, the response of a CMC stage 1 low-pressure turbine blade has been compared with the response of an equivalent metal turbine blade using the OSU GTL large spin-pit facility (LSPF) as the test vehicle. Load cells mounted on the casing wall, strain gages mounted on the airfoils, and other instrumentation are used to assess blade tip rub interactions with a 120-deg sector of a representative turbine stationary casing. The intent of this paper is to present the dynamic response of both the CMC and the metal blades with the turbine disk operating at design speed and with representative incursion rates and depths. Casing wear and blade tip wear are both characterized for several types of rub conditions including a light, medium, and heavy rub at room temperature. For each condition, the rub primary dynamic modes have been evaluated, and the corresponding blade tip loads have been calculated. The preliminary results suggest that a CMC blade has similar abilities to a metal blade during a rub event.

Possibility to Increase Biofuels Energy Efficiency used for Compression Ignition Engines Fueling

The paper presents the possibilities of optimizing the use of biofuels in terms of energy efficiency in compression ignition (CI) engines fueling. Based on the experimental results was determinate the law of variation of the rate of heat released by the combustion process for diesel fuel and different blends of biodiesel. Using this law, were changed parameters of the engine management system (fuel injection law) and was obtain increased engine performance (in terms of energy efficiency) for use of different biofuel blends.

Extending Lean Operating Limit and Reducing Emissions of Methane Spark-Ignited Engines Using a Microwave-Assisted Spark Plug

A microwave-assisted spark plug was used to extend the lean operating limit (lean limit) and reduce emissions of an engine burning methane-air. In-cylinder pressure data were collected at normalized air-fuel ratios ofλ=1.46,λ=1.51,λ=1.57,λ=1.68, andλ=1.75. For eachλ, microwave energy (power supplied to the magnetron per engine cycle) was varied from 0 mJ (spark discharge alone) to 1600 mJ. At lean conditions, the results showed adding microwave energy to a standard spark plug discharge increased the number of complete combustion cycles, improving engine stability as compared to spark-only operation. Addition of microwave energy also increased the indicated thermal efficiency by 4% atλ=1.68. Atλ=1.75, the spark discharge alone was unable to consistently ignite the air-fuel mixture, resulting in frequent misfires. Although microwave energy produced more consistent ignition than spark discharge alone atλ=1.75, 59% of the cycles only partially burned. Overall, the microwave-assisted spark plug increased engine performance under lean operating conditions(λ=1.68)but did not affect operation at conditions closer to stoichiometric.

‘Double-Newtonian’ rheological model for the two-dimensional Reynolds equation

In different mechanical applications, such as automotive engines, lubricants have undergone important changes over the past decades. Oil companies have added more and more additives to ensure correct performance of specific engine contacts, while increasing engine performance. Polymer additives are among these, used to increase viscosity at high temperatures and thus to flatten the viscosity–temperature curve. This viscosity increase occurs at low shear rates, but at high shear rates, the polymers are less efficient and the viscosity diminishes. This viscosity reduction at high shear rate is due to the distortion and alignment of the polymer molecules, and their breakage for extreme shear rates. This article derives the 2D Rabinowitsch Reynolds equation. It then analyses the influence of the double–Newtonian rheology on pressure, friction, and load-carrying capacity in a 2D linear contact. The influence of micro-geometrical features such as micro cavities is also studied.

Combustion Characteristics of Methane in A Direct Injection Engine Using Spark Plug Fuel Injector

The combustion characteristics of methane in a direct injection spark ignition engine using Spark Plug Fuel Injector (SPFI) was investigated. SPFI is a system developed to convert any externally-mixing (port injection, carburetor) spark ignition engine to direct injection by combining fuel injectors into spark plugs. The burning rates of methane were measured using normalized combustion pressure method, where the normalized pressure rise due to combustion is equivalent to the mass fraction burnt at the specific crank angle. A single cylinder research engine was installed with the SPFI system. Cylinder pressures were taken with engine running at 1100 rpm and stoichiometric air/fuel ratio. The spark timing was set at 25 o BTDC. For comparison, the engine was run with methane port injection. The optimal fuel injection timing with SPFI was found to be 170 o BTDC. Results showed that SPFI direct injection, increased the volumetric efficiency by 11% compared to port injection, resulting in higher heating value of cylinder charge per cycle. Combustion analysis show that the overall burning rate of methane direct injection is faster than the ones of port injection although is slower at the initial stage. Injection pressures affect ignition delay but not the combustion duration. Changing mixture stoichiometry affects the magnitude of ignition delay. Combustion duration increases with leaner mixture. Different load conditions have significant effect on combustion process. Lower loads tend to increase combustion duration but shorten ignition delay. SPFI Di methane system has the potential of increasing engine performance due to increased volumetric efficiency and faster burning rate.

Numerical Simulation of Low-Pressure Turbine Blade Separation Control

Low-pressure turbines are a common and important element of many modern jet engines. Any performance improvement will lead to net savings in aircraft operating costs. At low operating Reynolds numbers or for reduced stage solidities laminar separation from the constituent blades can noticeably deteriorate overall engine performance. Under such conditions active control of laminar separation may eliminate or reduce associated losses resulting in increased engine performance. A high-order-accurate finite volume Navier-Stokes code for investigating separation control for the PackB blade geometry at a Reynolds number based on axial chord of 25,000 was employed. For this Reynolds number laminar separation was observed in the experiments. First, a grid resolution study for the uncontrolled flow was carried out, which shows grid convergence for our simulations. Then separation control by pulsed vortex generator jets was investigated. It is shown how this control results in an earlier transitioning of the flow and the introduction of spanwise coherent structures. The increased wall-normal mixing associated with these two mechanisms results in an effective separation control. An even more efficient separation control can be accomplished by harmonic blowing through a slot. The astounding effectiveness of the latter control scheme is attributed to an amplification of the disturbance input through a hydrodynamic instability mechanism and to the suppression of three-dimensional structures, which weaken the spanwise structures. Finally, separation control by streamwise vortices that were generated by volume forces was investigated. As the flow does not amplify such structures the energy input required for accomplishing an effective control was found to be large compared with the other flow control techniques. Because the structures are steady they can, however, likely be generated with passive devices such as vortex generators.

Double-Newtonian rheology in a model piston-ring cylinder-wall contact

In automotive engines, lubricants have undergone important changes over the last decades. Oil companies have added more and more additives to ensure correct performance of specific engine contacts, whilst increasing engine performance. Polymer additives are amongst these, used to increase viscosity at high temperatures and thus to flatten the viscosity temperature curve. This viscosity increase occurs at low shear rates, but at high shear rates the viscosity diminishes and tends to a lower value. This viscosity reduction at high shear rate is due to the distortion and alignment of the polymer molecules, and their breakage for extreme shear rates. This paper analyses the influence of the double Newtonian rheology on friction and load carrying capacity in a model piston ring cylinder wall contact. It is found that the friction coefficient changes with increasing shear rate, as the contact goes through the non-Newtonian transition.

Effects of Oxygenated Gasoline on Fuel and Air Mass Flow Rates and Air-Fuel Ratio

The effects of excess feeding oxygen to the fuel-air mixture on air and fuel mass flow rates and also on air-fuel ratio are investigated here experimentally. This study concerned with the effects of injecting pure oxygen quantity to the mixture of fuel and air before interring the combustion chambers. It is found that the mass flow rate of fuel with the oxygen feeding is less than that of with no oxygen feeding at some specific values of engine speeds and the same thing was found for air mass flow rate. The air-fuel ratio also is less with considerable values in the case with oxygen feeding than that with no oxygen samples. Also this technique can be used partially, in some conditions oxygen can be feed into the combustion chambers to increase engine performance.

Numerical Analysis of the Combustion Process in a Compressed Natural Gas Direct Injection Engine

The design, development and optimization of an internal combustion engine require the application of a modern sophisticated analysis tool. In addition to experimental work, numerical calculations are now necessary to provide an insight into the complex in-cylinder process. The combustion process and its emission characteristics in a compressed natural gas direct injection engine were analyzed and investigated. The numerical studies were performed on a single cylinder of a 1.6-liter engine running at wide open throttle. The grid generation was established through an embedded algorithm for moving mesh and boundary in order to provide a more accurate transient condition. The combustion process was modelled with the eddy break-up model of Magnussen for unpremixed or diffusion reaction with three global reaction scheme. The computational fluid dynamics (CFD) simulations at two baseline conditions are carried out to examine the fluid flow, air-fuel mixing formation, combustion process, carbon monoxide emission distribution as well as NO emission formation occurred inside engine cylinder. The CFD results were compared with the experimental data and showed a very good agreement for two baseline conditions. A set of parametric studies were carried out by varying the timings of start of injection (SOI) and start of ignition (SI). The examined engine performance is in-cylinder pressure, while the considered emissions to be minimised are CO and NO levels. In order to study the effect of injection timing, the SOI timing was varied from 120o -140o with fixed ignition timing at 19o bTDC. On the other hand, SI timing was positioned from 15o-23o bTDC with fixed SOI timing for studying its influences. The CFD results indicated that slightly retarded SOI and SI timing can be chosen to reduce CO and NO levels while increasing engine performance.

Comparisons of hydrogen and gasoline combustion knock in a spark ignition engine

Combustion knock is one of the primary constraints limiting the performance of spark-ignition hydrogen fuelled internal combustion engines (H2-ICE) as it limits the torque output and efficiency, particularly as the equivalence ratio nears stoichiometric operation. Understanding the characteristic of combustion knock in a H2-ICE will provide better techniques for its detection, prevention and control while enabling operation at conditions of improved efficiency. Engine studies examining combustion knock characteristics were conducted with hydrogen and gasoline fuels in a port-injected, spark-ignited, single cylinder cooperative fuel research (CFR) engine. Characterization of the signals at varying levels of combustion knock from cylinder pressure and a block mounted piezoelectric accelerometer were conducted including frequency, signal intensity, and statistical attributes. Further, through the comparisons with gasoline combustion knock, it was found that knock detection techniques used for gasoline engines, can be applied to a H2-ICE with appropriate modifications. This work provides insight for further development in real time knock detection. This would help in improving reliability of hydrogen engines while allowing the engine to be operated closer to combustion knock limits to increase engine performance and reducing possibility of engine damage due to knock.

Virtual aluminum castings: An industrial application of ICME

The automotive product design and manufacturing community is continually besieged by Hercule an engineering, timing, and cost challenges. Nowhere is this more evident than in the development of designs and manufacturing processes for cast aluminum engine blocks and cylinder heads. Increasing engine performance requirements coupled with stringent weight and packaging constraints are pushing aluminum alloys to the limits of their capabilities. To provide high-quality blocks and heads at the lowest possible cost, manufacturing process engineers are required to find increasingly innovative ways to cast and heat treat components. Additionally, to remain competitive, products and manufacturing methods must be developed and implemented in record time. To bridge the gaps between program needs and engineering reality, the use of robust computational models in up-front analysis will take on an increasingly important role. This article describes just such a computational approach, the Virtual Aluminum Castings methodology, which was developed and implemented at Ford Motor Company and demonstrates the feasibility and benefits of integrated computational materials engineering.

Modelling route for abradable coatings

Improving sealing between rotating and stationary parts in aerospace gas turbines significantly increases engine performance by improving thermal efficiencies. To reach this aim, abradable seals are being incorporated into turbine casings. With an abradable seal, the blade tips incur into the shroud, thereby reducing the gap between the rotor and the coating to a minimum. These coatings are generally multiphase materials applied by thermal spray techniques and consisting in a combination of metallic matrix and additional dislocator phases with a controlled amount of porosity. The sealing effectiveness requires a combination of properties that are usually optimised empirically with thermal spray coatings generally made up from a range of two-phase powder mixtures. The present study intends to initiate a theoretical approach for the study of these materials aiming at developing a prediction strategy for structure improvement. Image analyses and finite element calculations were used to examine the effect of phase morphology on the mechanical behaviour of two reference abradable systems, namely AlSi-hBN and NiCrAl-Bentonite for compressor stages. Scanning Electronic Microscopy (SEM) was used to obtain a series of micrographs for coating characterisation. These micrographs were then treated to create equivalent images based on geometrical description of the inherent morphology. The resultant reduced images are used to carry out finite element calculations, in order to determine the mechanical properties of each coating. It is believed that this approach provides consistent results and is believed to be a reliable starting point for further coatings design.

Artificial neural-network based modeling of variable valve-timing in a spark-ignition engine

Variable valve-timing and lift are significant operating and design parameters affecting the performance and emissions in spark-ignition (SI) engines. Previous investigations have demonstrated that improvements in engine performance can be accomplished if the valve timing is variable. Traditionally, valve timing has been designed to optimize operation at high engine-speed and wide-open throttle conditions. Controlling valve timing can improve the torque and power curve of a given engine. Variable valve-timing can be used to reduce fuel consumption and increase engine performance. Intake valve-opening timing was changed from 10° crankshaft angle (CA) to 30° CA for both advance and retard with 10° CA intervals to the original opening timing. In this study, artificial neural-networks (ANNs) are used to determine the effects of intake valve timing on the engine performance and fuel economy. Experimental studies were completed to obtain training and test data. Intake valve-timing and engine speed have been used as the input layer; engine torque and fuel consumption have been used as the output layer. For the torque testing data, root mean squared-error (RMSE), fraction of variance ( R 2) and mean absolute percentage error (MAPE) were found to be 0.9017%, 0.9920% and 7.2613%, respectively. Similarly, for the fuel consumption, RMSE, R 2 and MAPE were 0.2860%, 0.9299% and 7.5448%, respectively. With these results, we believe that the ANN can be used for the prediction of engine performance as an appropriate method for spark-ignition (SI) engines.

Wear of diesel engine inlet valves and seat inserts

Valve wear has been a problem to engine designers and manufacturers for many years. Although new valve materials and production techniques are constantly being developed, these advances have been outpaced by demands for increased engine performance. The aim of this work was to establish the effect of engine operating parameters on diesel engine inlet valve recession and to screen potential new seat materials using test apparatus designed to simulate the loading environment and contact conditions to which a valve and seat are subjected. These data were then used, along with the mechanisms of wear identified during previous work [1-3], to develop a quantitative model for predicting valve recession. Valve recession was shown to increase with combustion loading, valve closing velocity and misalignment of the valve. Drip feed lubrication of the valve/seat interface reduced valve recession, on the material combination tested, by a factor of 3.5. The lubricant, however, was supplied in a larger amount and at a lower temperature than would be experienced in an engine. Two materials, of those tested, stand out as having improved wear resistance. These are maraging steel and ductile cast iron. Both gave significantly higher wear resistance than the other seat materials tested. The semi-empirical valve recession model, based on the fundamental mechanisms of valve and seat wear, provides a good approximation of valve recession for both engine tests and tests run on the hydraulic loading apparatus. Modelling of a diesel engine test indicated that impact was the major cause of valve recession.

이색 PIV 기술을 이용한 5밸브 가솔린엔진 연소실 내의 유동특성 분석

A 5-valve(intake 3-valve) engine has been developed to increase engine performance. These engines have a high power caused by the decrease of inertia mass of an intake valve and the increase of intake effective area. In this study, in-cylinder flow patterns were visualized with laser sheet method and velocity profiles at near intake valves were inspected by using a two-color PIV. In addition, steady flow tests were performed to quantify tumble ratio of flow-fields generated by a tumble control valve(TCV). Experimental results of steady flow test show that the cure of tumble ratio in intake 3-valve engine farmed as a S shape with valve lift changes. This tendency is different from the one in intake 2-valve engine. Using laser sheet method and two color PIV method, we can find that the intake flow through upper valve increases and the velocity gradient also slightly increases as valve lift increases. From this study, the in-cylinder flow characteristics around intake valves were made clearly.

High-performance muffler

A muffler for automotive vehicles. The muffler includes a passageway, an inlet at one end of the passageway, and a single outlet or dual outlets at the passageway's other end. The portion of the muffler connected to the inlet is substantially untapered. The portion of the passageway connected to the outlet or outlets tapers from wide to narrow away from the inlet and toward the outlet or outlets. This tapered geometry results in a very appreciable reduction of heat transmitted from the muffler back to the engine, increases engine performance, and produces a pleasant, deep sound while the engine is running.

Ultrasound whistles for internal combustion engine

A plurality of ultrasound engine whistles used in an internal combustion engine. The whistles may be placed inside a carburetor, inside a cylinder head, around an engine valve stem and other locations inside the engine. The whistles provide for greatly improved air fuel mixture prior to ignition. Also, the whistles allow for increased engine performance and acceleration, improved fuel mileage and a cleaner burning air fuel mixture for reduced fuel emissions into the environment. The ultrasound whistles include a whistle body having a first end portion and a second end portion. A whistle hole with whistle lip therearound is formed in the first end portion of the whistle body. The whistle hole has a depth in a range of 0.032 to 0.050 inches. Also, the whistle hole has a diameter in a range of 0.031 to 0.033 inches. The whistles may have various lengths in a range of ⅛ inch to 1 inch and longer depending on the application inside the engine. The whistles help create a greater and more homogenous and atomized air fuel mixture prior to ignition in the engine cylinder.

Wettability of porous media after exposure to synthetic gasolines

The wettability of a porous medium plays a critical role in the capillary phenomena governing the migration of a nonaqueous-phase liquid (NAPL) and subsequent efforts to recover this type of pollutant source from the subsurface. Although it is usually assumed that water-wetting conditions occur, limited field evidence at NAPL sites suggests that wettability characteristics can change to intermediate or organic-phase wetting, especially for complex NAPL's containing polar or surfactant molecules. The focus of this work was an assessment of potential wettability conditions for quartz mineral surfaces after exposure to synthetic gasolines. Many of the chemicals added to gasoline to increase engine performance have polar or surfactant characteristics. It is hypothesized that these additives could sorb to the quartz, causing the surface to become less hydrophilic. Four gasoline additives were added to isooctane, the base chemical for the synthetic gasoline. Following the exposure of the mineral surfaces to the organic phases, wettability was measured by three different techniques: oil-water contact angles, air-water imbibition rates and oil-water capillary pressure curves coupled with calculation of the USBM wettability index. Results show a change to intermediate-wetting conditions for two of the additives considered. Both concentration and the molecular structure of the additives affect the extent of these alterations.

Macroeconomics in Crisis: Agriculture in an Underachieving Economy

The American economy performs like an auto engine whose radiator is choked with lime deposits. Some time ago, it was discovered that adding generous amounts of tap water to the radiator permitted high power output without overheating. As the years went by, however, lime deposited in the radiator by the tap water reduced cooling capacity-tap water had to be added continuously for adequate engine performance even under normal loads on level highways. Deposits finally built to the point where nearly all agree that something has to be done to restore power to this basically sound, but occluded, engine. One recommendation is to use a high pressure radiator cap for increasing engine performance without continually adding water. But the concern is that something will burst under the pressure. Another recommendation is to remove the radiator and cook out the lime deposits. The drawback is protracted engine downtime. These are basically the dilemmas and options facing macroeconomic policy today. Performance of the economy as apparent in high inflation and unemployment rates, in slow real growth, and in a weak dollar in international exchange has reached crisis proportions. Economists and the public are convinced the economy is capable of better performance, but there is no concensus about how to restore

The Shape of Piston‐Ring Grooves

THE tendency towards increased engine performance combined with the lowest possible constructional weight has resulted in the stresses on pistons being carried to the extreme limits of fatigue strength. Further, it has always been the aim to raise the limits of fatigue strength as far as possible. These problems may be approached from the materials aspect, but, by improvement in production methods (i.e. from the workshop side), much advantage may be derived from the materials available while continuing to use present designs.