Lift Profile Research Articles

A comprehensive mathematical theory and optimized design of a high-frequency electro-pneumatic variable valve actuator for a camless IC engine

This paper discusses the development of a detailed mathematical theory and its use for the design of an electronically controlled, double-acting Variable Valve Actuation (VVA) mechanism for a camless internal combustion engine, that offers a comprehensive control over the timings and the motion of the valves such that any arbitrary time-variation of the valve lift profile can be obtained at variable rotational speeds of the engine shaft. The developed theory encompasses the thermo-fluid-dynamic as well as the applied-mechanical aspects of the actuator cylinder-engine valve system performance, the dynamics of the valve actuation being characterized by parameters such as valve opening duration, peak lift and seating velocity. The prediction of the mathematical theory compares well with several experimental data sets obtained from an in-house pneumatic VVA set-up. A new design methodology is formulated for determining the appropriate dimensions of the actuator, operating thermodynamic parameters and the electronic control of the various valve events for a desired range of engine rotational speed. Several parameters in the new design philosophy are kept within acceptable ranges established from time-tested data obtained from conventional cam-based valve actuation. For example, a new pneumatic cushioning strategy has been developed that is simple, effective and energy-efficient, and is able to keep the valve seating velocity within an acceptable range (0.08–1.13 m/s). The work also discusses the implementation of several constraints that are necessary for the design of a practically viable pneumatic actuator. The evolution of a design matrix map for the electro-pneumatic VVA is quantified for the engine rotational speed varying up to 5500 rpm.

Lift tailoring on unsteady airfoils with leading-edge vortex shedding using an inverse aerodynamic approach

In this paper, we present a physics-informed approach to tailor the lift profile of an unsteady airfoil through the execution of an appropriate maneuver. In previous research, a low-order aerodynamic model based on the unsteady thin airfoil theory was developed for predicting the flowfield and loads on airfoils undergoing arbitrary motions. The theory was phenomenologically augmented using the concept of leading edge suction parameter (LESP) to incorporate the capability to predict intermittent leading edge vortex (LEV) shedding. The criticality of LESP was used to predict the onset and termination of LEV shedding and thus model the effect of LEVs on the flowfield and loads for a prescribed motion. In the current work, an inverse aerodynamic formulation is developed based on this framework for tackling the inverse problem: to obtain the motion kinematics required for generating a prescribed lift profile for an airfoil operating in the dynamic-stall regime. The LEV-modeling capability of the aerodynamic model enables the motion-design algorithm to take into account the effect of complex phenomena, such as dynamic stall and LEV shedding, which are not taken into account in previous research approaches. Several case studies are presented to demonstrate various scenarios such as lift tracking using pitching and heaving motions, lift cancellation during unsteady motion, and the generation of a given lift profile using two equivalent motions. The kinematic profiles generated by the inverse formulation are also simulated using a high-fidelity unsteady computational fluid dynamics solver to validate the predictions.

Iterative Learning for Laboratory Electro-Hydraulic Fully Flexible Valve Actuation System Transient Control

<div>Fully flexible valve actuation (FFVA) is a key enabling technology of internal engine combustion research and development. Two laboratory electro-hydraulic FFVA systems have been developed and implemented in R&D test cells. These FFVA systems were designed using repetitive control (RC), which is based on internal model principle (IMP), for constant engine speed operation. With the engine operating in a steady-state condition, the valve profile input is periodic. This can be accommodated by a repetitive controller, which provides the function of flexible control to step changes in valve lift, valve opening duration, and cam phase angle position.</div> <div>During engine speed transients, as the valve reference trajectory becomes aperiodic in the time domain, the controllers based on the linear time invariant (LTI) IMP, such as RC, are no longer applicable. Engine speed transient control is a desired function to engine research and other similar applications, such as motor control. Several investigations are reported with limited results because of the assumption of IMP and periodic input.</div> <div>This article presents the control design and verification of the iterative learning control (ILC) algorithm for the laboratory electro-hydraulic FFVA system. This algorithm tracks valve lift profiles under steady-state and transient operation. A dynamic model of the plant was obtained from experimental data to design and verify the effectiveness and robustness of this approach. The simple structure of the ILC in implementation and low cost in computation are crucial benefits to recommend the ILC. It is not an IMP-based approach, and its structure does not depend on the system input. Therefore, it has higher robustness to perturbation and modeling errors than other control methods for repetitive valve lift profile tracking tasks.</div>

Inertial migration of a neutrally buoyant spheroid in plane Poiseuille flow

We study the cross-stream inertial migration of a torque-free neutrally buoyant spheroid, of an arbitrary aspect ratio $\kappa$ , in wall-bounded plane Poiseuille flow for small particle Reynolds numbers ( $Re_p\ll 1$ ) and confinement ratios ( $\lambda \ll 1$ ), with the channel Reynolds number, $Re_c = Re_p/\lambda ^2$ , assumed to be arbitrary; here $\lambda =L/H$ , where $L$ is the semi-major axis of the spheroid and $H$ denotes the separation between the channel walls. In the Stokes limit ( $Re_p =0)$ , and for $\lambda \ll 1$ , a spheroid rotates along any of an infinite number of Jeffery orbits parameterized by an orbit constant $C$ , while translating with a time-dependent speed along a given ambient streamline. Weak inertial effects stabilize either the spinning ( $C=0$ ) or tumbling orbit ( $C=\infty$ ), or both, depending on $\kappa$ . The asymptotic separation of the Jeffery rotation and orbital drift time scales, from that associated with cross-stream migration, implies that migration occurs due to a Jeffery-averaged lift velocity. Although the magnitude of this averaged lift velocity depends on $\kappa$ and $C$ , the shape of the lift profiles are identical to those for a sphere, regardless of $Re_c$ . In particular, the equilibrium positions for a spheroid remain identical to the classical Segre–Silberberg ones for a sphere, starting off at a distance of about $0.6(H/2)$ from the channel centreline for small $Re_c$ , and migrating wallward with increasing $Re_c$ . For spheroids with $\kappa \sim O(1)$ , the Jeffery-averaged analysis is valid for $Re_p\ll 1$ ; for extreme aspect ratio spheroids, the regime of validity becomes more restrictive being given by $Re_p \kappa /\ln \kappa \ll 1$ and $Re_p/\kappa \ll 1$ for $\kappa \rightarrow \infty$ (slender fibres) and $\kappa \rightarrow 0$ (flat disks), respectively.

Cyclic Analysis of In-Cylinder Vortex Interactions Based on Data-Driven Detection and Characterization Framework

Abstract The complex vortex flow interactions are critical to affect the fuel–air mixing and combustion stability in direct-injection engine. However, due to the strong cyclic variations inside engine, the multiscale swirl flow characteristics with cyclic details are difficult to be sufficiently revealed. Therefore, a vortex detection and characterization framework, including physical and data-driven methods, is implemented to elucidate the cyclic vortex interaction process. In this study, a high-speed time-resolved particle image velocimetry is applied to record the spatiotemporal flow behavior under three different swirl ratio conditions. First, the presence of vortex motion is detected at each crank angle for each engine cycle. Results show that the vortex interaction processes under different swirl ratio conditions exhibit distinctive characteristics. The presence of multiple vortices and their interactions are found to trigger dramatic changes and variations in swirl flow behavior. Then, the individual-cycle analysis of the vortex interaction effects on flow characteristics is conducted. The vortex characteristics including vortex location, strength, and size are examined with cyclic detail using data-driven unsupervised clustering. Results indicate that the vortex merging is the main source inducing the vortex characteristics variations. Furthermore, the occurrence and duration of the vortex merging process are found to be closely related to the intake swirl ratio and valve lift profile. Increased swirl ratio and valve lift cause vortex to merge earlier and reduce the merging duration. This finding provides a potential idea to alleviate the cyclic variation issue by controlling the vortex merging process.

Challenges and feasibility of a six-stroke engine using water direct injection

As fuel efficiency and exhaust regulations have become more stringent, many studies have been conducted to improve fuel efficiency. One interesting proposal is to develop a six-stroke engine using water injection. However, there is a lack of research on this concept, and existing studies have only taken a theoretical approach or did not involve comparisons with a four-stroke engine, obscuring the feasibility of a six-stroke engine using water injection. So, in this study, we performed experiments and simulations of a six-stroke engine using water injection and compared the results with those of a four-stroke engine. We optimized the exhaust valve lift profile through simulation for an actual exhaust cam of the six-stroke engine, and modified a four-stroke port fuel injection engine to a six-stroke engine. Then, through experiments and simulations, we evaluated the feasibility and the challenges of building a six-stroke engine using water injection. We used the CONVERGE v2.4 software application and validated the simulation models through the results of experiments. Using these models, we conducted simulations with various injection timings, masses, and water temperatures. The results indicate that the cylinder wall is cooled due to continuous water injection making evaporation unstable and that wall-temperature control is required in order to realize a six-stroke engine using water injection. In a simulation assuming the constant temperature of the wall, as additional strokes are added, the indicated mean effective pressure (IMEP) decreases by about 0.4 bar compared to that of the four-stroke engine, and only about 40% of this loss is recovered through water injection. The wall evaporation ratio is more critical to the feasibility of the six-stroke engine using water injection than other parameters. We show that it is very difficult to achieve a six-stroke engine using water injection unless a significant amount of heat energy for evaporation is brought from sources other than the mixture in the cylinder. The challenges of a six-stroke engine using water injection were cylinder temperature control and latent heat of water. If excessive cooling does not occur, such as in steam injection, IMEP can increase due to an increase in mass. However, this is very ideal case. It is difficult to obtain energy elsewhere for evaporation, and due to the latent heat of water, the mixture is inevitably cooled down making it difficult to realize this concept of six-stroke engine.

Sectional Leading Edge Vortex Lift and Drag Coefficients of Autorotating Samaras

Autorotating samaras such as Sycamore seeds are capable of descending at exceptionally slow speeds and the secret behind this characteristic is attributed to a flow mechanism known as the leading edge vortex (LEV). A stable LEV is known to increase the maximum lift coefficient attainable at high angles of attack and recent studies of revolving and flapping wings have proposed suitable lift and drag coefficient models to characterise the aerodynamic forces of the LEV. For the samara, however, little has been explored to properly test the suitability of these low-order lift and drag coefficient models in describing the aerodynamic forces produced by the samara. Thus, in this paper, we aim to analyse the use of two proposed aerodynamic models, namely, the normal force and Polhamus models, in describing the sectional aerodynamic lift of a samara that is producing a LEV. Additionally, we aim to quantify the aerodynamic parameters that can describe the lift and drag of the samara for a range of wind speed conditions. To achieve this, the study first examined the samara flight data available in the literature, and from it, the profiles of the lift coefficient curves were investigated. Subsequently, a numerical Blade Element-Momentum model (BEM) of the autorotating samara encompassing different lift profiles was developed and validated against a comprehensive set of samara flight data, which were measured from wind tunnel experiments conducted at the University of Bristol for three different Sycamores. The results indicated that both the normal force and Polhamus lift models combined with the normal force drag can be used to describe the two-dimensional lift characteristics of a samara exhibiting an LEV. However, the normal force model appeared to be more suitable, since the Polhamus relied on many assumptions. The results also revealed that the aerodynamic force parameters can vary with windspeed and with the samara wing characteristics, as well as along the span of the samara wing. Values of the lift curve slope, zero-lift drag coefficient, and maximum lift coefficient are predicted and presented for different samaras. The study also showed that the low-order BEM model was able to generate a good agreement with the experimental measurements in the prediction of both rotational speed and thrust. Such a validated BEM model can be used for the initial design of bio-inspired rotors for micro-air vehicles.

The Aerodynamic Characteristics Investigation on NACA 0012 Airfoil with Owl’s Wing Serrations for Future Air Vehicle

Owls have an incredibly unique ability to fly in silence, and this ability has significant potential to reduce noise pollution from aircraft engines. For decades, researchers have been studying the noise abatement system in conventional aircraft, but only a few of them had looked into the owl’s ability to reduce the aircraft noise level, especially on the serrated wing. The present study aims to investigate the lift and drag coefficient of the serrated wings including leading-edge serrations, trailing-edge serrations, both-edge serrations, and the original/baseline wing model from the NACA 0012 airfoil. The experimental testing was performed in a wind tunnel at Reynolds numbers of 20,000 and 40,000 and angle of attack from 2° to 30°, in 2° angle intervals. In general, the results showed that each wing model produced a similar lift and drag coefficient profiles, which were proportional to the angle of attack. At Reynolds number of 40,000, the lift coefficient increases from 0.45 to 1.5, as the angle of attack increases from 2° to 24°. Afterward, it decreased as the angle of attack exceeded 24°. According to the data, the trailing-edge serrations model showed the lowest drag coefficient at a Reynolds number of 40,000. Meanwhile, the highest lift coefficient at Reynolds number of 40,000 had been produced by the baseline wing model. This result is beneficial in reducing the noise generation produced by wing structure and at the same time enhancing aerodynamic efficiency.

ОБОСНОВАНИЕ КОНСТРУКЦИИ ГЛУБОКОРЫХЛИТЕЛЯ ЧИЗЕЛЬНОГО ТИПА С ОСЦИЛЛЯТОРОМ

Target: using models of interaction of the system of deep–loader deformers with the soil to substantiate the emergence and creation of an innovative system of ripper deformers with elements in the architecture of which oscillatory phenomena occur – flutter. The consideration of the interaction process was based on a critical analysis of various soil models and corresponding schemes of its destruction by horizontal elements of the broken profile of the system of deformers of the deep-digger. The constructed model of interaction is based on the basic principles of mechanics of solids and mechanics of soils (soils). The research was carried out to integrate symmetrically broken soil-forming plates into the architecture of the innovative deep-drilling deformator system in accordance with the current ГОСТ standards and the СТО АИСТ. Data processing was performed using standard and special techniques. A new horizontal element (ground lift) of the system of deformers of the working body of the chisel-type implement, patent for invention No. 2742657, has been developed. The polyline architecture of the soil lift profile allows for better crumbling of the over-compacted soil layer, and also contributes to the occurrence of undamped oscillations. The presence of such an oscillator in the tool deformator system reduces the friction of the soil on the working body, which reduces the energy intensity of the process while improving the quality of loosening. Using the innovative architecture of a chisel deep-loader with an oscillator leads to the occurrence of additional deformations in the decompressed layer and prevents the soil from sticking, as a result of which there is no “soil wedge”, which significantly increases the traction resistance of the deep-loader and reduces the quality of soil loosening. Allows you to profile the loosening area more efficiently and provide the required loosening without turning the treated soil layer to a depth of up to 60 cm.

Development of Two-Step Exhaust Rebreathing for a Low-NOx Light-Duty Gasoline Compression Ignition Engine

The global automotive industry is undergoing a significant transition as battery electric vehicles enter the market and diesel sales decline. It is widely recognized that internal combustion engines (ICE) will be needed for transport for years to come; however, demands on ICE fuel efficiency, emissions, cost, and performance are extremely challenging. Gasoline compression ignition (GCI) is one approach for achieving the demanding efficiency and emissions targets. A key technology enabler for GCI is partially-premixed, compression ignition (PPCI) combustion, which involves two high-pressure, late fuel injections during the compression stroke. Both NOx and smoke emissions are greatly reduced relative to diesel, and this reduces the aftertreatment (AT) requirements significantly. For robust low-load and cold operation, a two-step valvetrain system is used for exhaust rebreathing (RB). Exhaust rebreathing involves the reinduction of hot exhaust gases into the cylinder during a second exhaust lift event during the intake stroke to help promote autoignition. The amount of exhaust rebreathing is controlled by exhaust backpressure, created by the vanes on the variable nozzle turbine (VNT) turbocharger. Because of the higher cycle temperatures during rebreathing, exhaust HC and CO may be significantly reduced, while combustion robustness and stability also improve. Importantly, exhaust rebreathing significantly increases exhaust temperatures in order to maintain active catalysis in the AT system for ultra-low tailpipe emissions. To achieve these benefits, it is important to optimize the rebreathe valve lift profile and develop an RB ON→OFF (mode switch) strategy that is easy to implement and control, without engine torque fluctuation. In this study, an engine model was developed using GT-Suite to conduct steady-state and transient engine simulations of the rebreathing process, followed by engine tests. The investigation was conducted in four parts. In part 1, various rebreathe lift profiles were simulated. The system performance was evaluated based on in-cylinder temperature, exhaust temperature, and pumping work. The results were compared with alternative variable valve actuation (VVA) strategies such as early exhaust valve closing (EEVC), negative valve overlap (NVO), positive valve overlap (PVO). In part 2, steady-state simulations were conducted to determine an appropriate engine load range for mode switching (exhaust rebreathing ON/OFF and vice-versa). The limits for both in-cylinder temperature and exhaust gas temperature, as well as the external exhaust gas recirculation (EGR) delivery potential were set as the criteria for load selection. In part 3, transient simulations were conducted to evaluate various mode switch strategies. For RB OFF, the cooled external EGR was utilized with the goal to maintain exhaust gas dilution during mode switches for low NOx emissions. The most promising mode-switch strategies produced negligible torque fluctuation during the mode switch. Finally, in part 4, engine tests were conducted, using the developed RB valve lift profile, at various low-load operating conditions. The mode switch experiments correlated well with the simulation results. The tests demonstrated the simplicity and robustness of the exhaust rebreathing approach. A robust engine response, low CNL, high exhaust gas temperature, and low engine out emissions were achieved in the low load region.

Thermodynamic analysis of improving fuel consumption of natural gas engine by combining Miller cycle with high geometric compression ratio

The goal of this work is to solve the problem of low thermal efficiency of stoichiometric natural gas engines by combining the Miller cycle with a high geometric compression ratio (GCR). A one-dimensional thermodynamic model of a stoichiometric natural gas engine with turbocharger is established, and its effectiveness is verified by experimental data. On this basis, the influence of the high GCR combined with the Miller cycle achieved by early intake valve closing (EIVC) or late intake valve closing (LIVC) on the fuel consumption is studied in detail. The results show that the reasonable matching of the GCR and intake valve lift profile is beneficial to improve fuel consumption. The upper limit of fuel consumption improvement is determined by the performance of the turbocharger. The EIVC50 + GCR14 and LIVC75 + GCR13.5 solutions can not only ensure that the load and knock level are consistent with the baseline engine (IVC558 + GCR11.5), but also obtain the optimal fuel economy. Thermodynamic analysis further reveals the fuel-saving mechanism. The fuel consumption can be improved by 4.1%, mainly thanks to a good balance between theoretical efficiency and combustion loss. In addition, the reduction in gas exchange loss further improves fuel consumption. Unfortunately, the increase in heat transfer loss and friction loss limits the further improvement in fuel consumption.

Eddy current detection of laser-dispersed markers as a new approach to determining the position of load supporting means

The logistic industry has a steady need for improved positioning of goods to keep commercial success. Next to high accuracy, a low maintenance system is needed to ensure the benefits of automation. While state of the art position determination is done by mechanical, optical, or hydraulic techniques, this research addresses a new approach using laser-dispersed position markers and contactless eddy current technology for detection. A fiber laser is used to create thin melt tracks on lifting profiles, and zirconium oxide powder is added to the melt to create a dispersed track as a position marker. The influence of the laser process parameters on the track width and surface topology is determined, as well as the influence on eddy current measurements. It has been found that increasing the laser power and the powder feed rate of zirconium oxide in the investigated range from 190 to 490 W and 1.16 to 3.6 g/min, respectively, increased the signal from the eddy current sensor unit. Positioning concepts are examined by moving the eddy current sensor above the lifting profile with speeds up to 4000 mm/min. The laser-dispersed markers are clearly recognizable in the sensor signal with a minimum distance of 2 mm from each other and an interspace of 0.8 mm from the lifting profile to the sensor head. The recognition error rate is quite low at around 0.0037%. However, the resolution, which can be derived from the eddy current sensor signal, is about 0.5 mm ± 0.11 mm. In order to gain insight into the suitability of the examined technology for forklifts, the eddy current sensor is mounted on the fork bracket and typical actions are simulated. Last, other applications for eddy current detection of laser-dispersed markers, such as storing and reading information for component identification, are demonstrated.

Effects of Intake Valve Lift Form Modulation on Exhaust Temperature and Fuel Economy of a Low-loaded Automotive Diesel Engine

Exhaust after-treatment (EAT) systems on automotive vehicles cannot perform effectively at low loads due to low exhaust temperatures (Texhaust < 250oC). Con-ventional late intake valve closure (LIVC) technique - a proven method to im-prove diesel exhaust temperatures - generally requires the modulation of the whole valve lift profile. However, an alternative method - boot-shaped LIVC - only needs partial lift form modulation and can rise exhaust temperatures signif-icantly. Therefore, this study attempts to demonstrate that boot-shaped LIVC can be an alternative solution to improve exhaust temperatures above 250oC at low-loaded operations of automotive vehicles.A 1-D engine simulation program is used to model the diesel engine system operating at 1200 RPM engine speed and at 2.5 bar brake mean effective pres-sure (BMEP) engine load. Boot-shaped LIVC is achieved via keeping the valve lift constant (at 4.0 mm) for a while during closure and then closing it at different closure angles. The method results in up to 55oC exhaust temperature rise through reduced in-cylinder airflow and thus, is adequate to keep EAT system above 250oC at low loads. The longer the boot is kept during closure, the lower the air-to-fuel ratio is reduced and the higher the exhaust temperature flows at turbine exit. Similar to conventional LIVC, boot-shaped LIVC improves fuel con-sumption as pumping losses are decreased in the system. Despite aforementioned improvements, EAT warm-up is affected negatively due to the significant drop-off on exhaust mass flow rates. The need to modify only some parts of the lift profile is a technical advantage and can reduce production costs.

X-Ray Characterization of Real Fuel Sprays for Gasoline Direct Injection

Abstract The effects of fuel blend properties on spray and injector performance has been investigated in a side-mount injector for gasoline direct injection (GDI) using two certification fuel blends: Euro 5 and Euro 6. Several X-ray diagnostic techniques were conducted to characterize the injector and spray morphology. Detailed internal geometry of the GDI injector was resolved to 1.8 μm, through the use of hard X-ray tomography. The geometry characterization of this six-hole GDI, side mount injector, quantifies relevant hole and counterbore dimensions and reveals the intricate details within the flow passages, including surface roughness and micron-sized features. Internal valve motion was measured with a temporal resolution of 20 μs and a spatial resolution of 2.0 μs, for three injection pressures and several injector energizing strategies. The needle motion for both fuels exhibits similar lift profiles for common energizing commands. A combination of X-ray radiography and ultra-small-angle X-ray scattering (USAXS) was used to characterize the fuel mass distribution and the droplet sizing, respectively. Tomographic spray radiography revealed the near-nozzle distribution of fuel mass for each of the fuels and the asymmetry produced by the angled nozzles. Under evaporative conditions, the two fuels show minor differences in peak fuel mass distribution during steady injection, though both exhibit fluctuations in injection during the early, transient phase. USAXS measurements of the path-specific surface area of the spray indicated lower peak values for the more evaporative conditions in the near nozzle region.

Methane Emissions Evaluation on Natural Gas/Diesel Dual-Fuel Engine during Scavenging Process

Natural gas/diesel dual-fuel engine is known as a solution for shipping industries to simultaneous reduces NOx and PM emissions nowadays. Unfortunately, high HC emissions are produced, especially at low loads conditions. However, there are two possibilities for the source of HC emissions from the engine, namely during the combustion process and during the scavenging process. This study evaluates the methane emissions (part of HC emissions) concentration during the scavenging process. Cold flow engine simulations are evaluated and validated to this study at low load condition using natural gas injection at intake port during valve overlap. Moreover, several natural gas injection timings are conducted to observe the effect on the methane emissions concentrations at exhaust port after the exhaust valve closed. The natural gas penetration is nearly after the intake valve closed (IVC) thus the natural gas enters the combustion chamber at the next intake cycle. It observed that the scavenging process contributes to the methane emissions formation on natural gas/diesel dual-fuel engine using intake port natural gas penetration after IVC. Besides, the concentration of methane emissions during the scavenging process has very low contribution than the combustion process. It is possibly a variation of the methane emissions concentration in the other valve lift profile and natural gas injection strategies. Thus, it recommends to widely observing how significant the methane emissions generated during the scavenging process on the other engines with those variations.

Experimental verification of improved performance of Savonius turbine with a combined lift and drag based blade profile for ultra-low head river application

Savonius turbine is a prominent drag based turbine used for harnessing wind or water power. It can be customized for run-off river stream locations having ultra-low head (<1 m) and low water velocities, for the turbine is self-starting and requires low starting torque. However, considering its low efficiency, an improved blade design of the turbine is needed to enhance its performance. If a Savonius turbine can generate power by utilizing lift force in addition to drag force then its performance can be improved; however any changes in its design need to be experimentally verified. In this paper, the performance of a combined lift and drag based modified Savonius water turbine is investigated in an open flow water channel at different water velocities between 0.3 m/s and 0.5 m/s, which are commonly found in a perennial river. The semi-circular blade design is modified by combining straight (drag profile) and airfoil (lift profile) blades. Detailed measurements show that maximum coefficient of power (0.268) is higher than some of the recently modified designs of Savonius water turbine. Further, correlation equations for power curves of the improved design for river stream application are also developed. The present work delineates the significance of modified Savonius turbine for efficient and cleaner production of water power.

Designing, modeling, and structural analysis of a newly designed double lobe camshaft for a two-stroke compressed air engine

With the rapid increase of urbanization and industrialization, the energy demand has expeditiously risen. The natural resources are limited and will be extinct in the next few years. If the depletion of fossil fuels continues at the same rate as it is, the world will suffer from severe energy scarcity in the nearer future. Therefore, to reduce the dependency on liquid-based petroleum fuels, there is an urgent need for alternative fuels that could compensate for diesel demand and reduce harmful emissions from the atmosphere. The paper presents the designing, modeling, and analyzing a newly designed double lobe camshaft for a compressed air engine. In this study, a 100-cc Four-Stroke SI engine manufactured by Bajaj Auto, an Indian motorcycle manufacturer, was used and tested on compressed air. The engine was modified from a conventional four-stroke to a two-stroke engine by designing a new camshaft for opening the valves at different timings. The newly designed camshaft contains axisymmetric double lobes on both the inlet and outlet cams. Thus, in one complete revolution of the crankshaft, both the valves open once, resulting in one power stroke and one exhaust stroke, eliminating the compression and intake stroke. Any modifications in the camshaft cause various changes in the stress distribution and deformation along the shaft, which should be studied to provide us vital information about the life and effectiveness of the new modified camshaft. The objective is to determine the new valve lift profile, deformation, and equivalent (Von-Mises) stress under loading conditions on the double lobe camshaft. The designing and modeling of the camshaft are done in SOLIDWORKS 2020, and structural analysis is carried out in ANSYS 2020. The maximum total deformation resulted from the analysis comes out to be 5.72 × 10-4 mm, and the maximum value of equivalent stress evaluated is 31.17 MPa.

Numerical investigation on the effect of nozzle geometry and needle lift profile on the cavitation flow and efficiency of the marine diesel engine injector

Numerical investigation on the effect of nozzle geometry and needle lift profile on the cavitation flow and efficiency of the marine diesel engine injector

Optical study on needle lift and its effects on reacting diesel sprays of a single hole solenoid injector

Precise control of needle lift provides one possibility to control the diesel spray and combustion process actively. However, most studies of needle lift focus on internal flow or near nozzle spray. Little work has been performed on its effects on reacting spray. In this work, one way to change the needle lift profile of a solenoid injector has been developed and the relationship between needle lift and reacting spray has been investigated. The needle movement was detected with an optical nozzle. In addition, the visualization of reacting sprays of the same injector equipped with a single hole nozzle was conducted in a combustion chamber. Some simulations were also performed to assist the analysis. The results show that the needle lift profile can be regulated by changing the thickness of an adjusting pad. It seems the different needle lift profiles do not bring in significant influences on reacting spray characteristics. The CFD results indicate that it is mainly caused by the similar internal flow characteristics which do not show strong variation when needle lift is higher than 0.1 mm. However, the discharge coefficient and velocity coefficient decrease sharply when needle lift is smaller than 0.05 mm because of the ?throttle? effect.

Shape optimization of SG6043 airfoil for small wind turbine blades

The geometry of airfoil sections in small wind turbine blades affect the boundary layer separation, promote the flow transition to turbulence and consequently influence the performance of many types of small wind turbines. However, few optimization results are available for typical small wind turbine blades. Here, we report a particular shape optimization study of the standard SG6043 airfoil that applies the genetic algorithm along with the low-Re XFOIL solver. The numerical model is first validated against available experimental values for the SG6043 airfoil at a Reynolds number of 100, 000. The predicted lift and drag profiles are qualitatively found in good agreement with the experimental values, particularly in the pre-stall regime, provided that the XFOIL’s transition exponent is adjusted to 11. The simulation is then extended to a lower Reynolds number of 60, 000 that is consistent with an average tip-speed-ratio λ = 4.0. Four specific scenarios seeking different objective functions are proposed for optimization. While the first two scenarios focus on typical optimum configurations at which the maximum lift-to-drag ratios are realized, the objective function of the latter scenarios considers the maximum arithmetic-mean over multiple consecutive degrees of the corresponding angle of attacks. The preliminary results show remarkable improvement in the range from 24% to 10% in the predicted lift-to-drag ratios in comparison with the original configuration at the expense of the corresponding airfoils’ stiffness. This is followed by an elaboration on the entire blade design along with the specification of the resulting power coefficient and annual energy production.