Browse Topic: Flywheels
The automotive industry's future hinges on a new AI-native engineering workflow that accelerates iteration, strengthens system thinking, and preserves human judgment. Automotive development cycles are compressing at a pace the industry has never seen. The shift to all-electric fleets of software-defined vehicles is moving faster than traditional processes can absorb. In parallel, regulatory pressure and customer expectations keep rising, demanding greater performance, higher safety, better energy efficiency, and sharper competitiveness. In this environment, OEMs R&D competitiveness depends on three factors: How quickly teams can explore and iterate on design choices while delivering differentiated value, product performance, and cost efficiency. How early system-level interactions can be detected, before they turn into delivery friction or costly late-stage failures. How effectively a company can encode and scale its internal engineering know-how into lean development processes.
Puddling is a crucial process in rice cultivation, involving the preparation of the soil in a flooded field to create a soft, muddy seedbed. There are two classifications for puddling: full cage and half cage. Full cage puddling involves replacing the rear wheels of the tractor with steel paddle wheels, which are used to till the rice paddies directly without any additional implement. In the half cage puddling, the rear wheels remain on the tractor, and a smaller cage or paddle wheel is attached to the outside. Considering the field size, the operator often releases the clutch very quickly after a speed or direction change. This generates torque spikes, which are harmful to Transmission Gears and Clutches. This can lead to gear teeth bending fatigue failure due to repeated higher bending stresses. In this paper, a study related to how to reduce overall product development time by simulating bending fatigue failure of gear in lab environment is presented. A systematic approach is used to understand the field application, data acquisition, Data analysis, new test stand development and replication of failure mode in lab environment. This approach resulted in significant time savings. Multiple design iterations with minimal variation can be executed. This eliminates dependency on field, environmental conditions, and different variabilities. Finally, it supports timely decision-making based on the outcomes.
This SAE Standard was developed to provide a method for indicating the direction of engine rotation and numbering of engine cylinders. The document is intended for use in designing new engines to eliminate the differences which presently exist in industry.
Suppose we have two identical variable-inertia flywheels and we connect them to the inputs of a differential. The output is connected to the driveline of a vehicle. There are several types of three-element mechanical differentials (e.g. ring-gear/carrier, epicyclic, etc.). The specific type of 3-element mechanical differential is inconsequential in the following analysis except to say there are two inputs (e.g. side gears) and one output (e.g. carrier/ring-gear). What’s important is simply the relationship - For example, using the notation ‘a’ for the first side gear and ‘b’ for the second side gear and ‘c’ for the carrier, then the relationship is: c=(a+b)/2. Understand that ‘a’, ‘b’, and ‘c’ can each be an input or an output. Using the designation ‘omega’ (ω) then the relationship looks like this: ωc=(ωa+ωb)/2. So, we have one variable inertia flywheel (VIFa) and a second variable inertia flywheel (VIFb) connected to two side gears, a and b, and a vehicle driveline connected to the differential carrier, c. For starters, we set the inertia of VIFa to its maximum inertia value, Iamx, and the inertia for VIFb to its minimum inertia value, Ibmn. Then we will spin up (with some auxiliary power source) VIFa to a minimum initial velocity (ωamn) and, in a reverse direction, VIFb to its maximum velocity (ωbmx). At this point, the ‘output’ to the vehicle driveline will be (ωamn-ωbmx)/2. But, at these initial conditions we need for the driveline angular velocity to equal zero. This can only be done by incorporating speed-changing gear set between the flywheels and the differential inputs. This gear set can change the speed of either VIFa or VIFb or both. Let’s apply the ratio (r=ωamn/ωbmx) equally to each differential input. Let’s put some numeric values to this system: ωamn=10; ωbmx=-30. If we want equal speed change for both flywheels as a percentage (i.e. equal ratio of change) then we can find the ratio (r) by taking the root: r=sqrt(ωbmx/ωamn)=1.732. Thus, the initial velocity of each VIF at the input to the differential is: ωadif=r*ωamn=17.32 while ωbdif=ωbmx/r=-17.32. What we have accomplished with these two gear sets applied to the differential inputs is that at the initial velocities for each VIF, the output of the differential is zero. The point of this is that when the vehicle is at a standstill, if we change the inertia setting of each flywheel, decreasing the inertia of VIFa (its inertia was initially at its maximum) while simultaneously increasing the inertia of VIFb (its initial inertia was set to its minimum value) we will cause the angular velocity of VIFa to increase (conserving momentum) while the negative angular velocity of VIFb will decrease (conserving momentum) and ,since VIFb is rotating in a reverse direction of VIFa, the torque produced by each flywheel as they change velocity will be in the same direction and applied to the differential output thus accelerating the vehicle.
Automotive companies are constantly looking to increase the fuel efficiency, shift quality, passenger comfort, and to reduce wear and tear on the components. Most of these aspects depend on the accuracy of torque used for transmission control, which determines the required operational gear position at a given speed and road conditions. Currently, SAE J-1939 CAN bus torque estimation relies on steady state maps that are generated during the calibration of the engine for different speeds and loads. In this paper we report the development of a Virtual Flywheel Torque Sensor (VFTS) useful for real time torque measurement based on an engine speed harmonics analysis. The VFTS uses a signal from the flywheel speed sensor to estimate the flywheel angular acceleration, which and provides a proportional torque value which corresponds to torque at the flywheel. The performance of the VFTS is evaluated using an engine with flywheel attached to driving a dynamometer at different torque loads (100%, 75%, and 50% load) and different speeds (900-1800 RPM). The accuracy of the sensor was found to vary within from 2-12% in the load range tested. The dynamometer test results are further validated using 1D AMESim engine modeling and simulation.
Dual mass flywheel (DMF) is an excellent solution to improve the noise, vibration, and harshness (NVH) characteristic of any vehicle by isolating the driveline from the engine torsional vibrations. For the same reason, DMF’s are widely used in high power-density diesel and gasoline engines. However, the real-world usage conditions pose a lot of challenges to the robustness of the DMF. In the present work, by capturing the Real-World Usage Profile (RWUP) conditions, a new methodology is developed to evaluate the robustness of a DMF fitted in a Sports utility vehicle (SUV). Ventilation holes are provided on clutch housing to improve convective heat transfer. Improvement in convective heat transfer will increase the life and will reduce clutch burning concerns. Cities like Mumbai, Chennai, Bangalore, roads will have clogged waters during rainy season. When the vehicle was driven in such roads, water enters inside the clutch housing through ventilation holes. Prolonged usage of vehicle in this condition results in water entering inside the DMF. DMF has grease over the springs to reduce friction. Water entering inside the DMF will reduce the viscosity of grease and subsequently leads to erosion of grease from DMF. This will result in metallic noise concern in Engine ON condition. In the present work, author presents test methodology that shall be used to reproduce the metallic noise concern during development phase. The methodology is the combination of water wading test carried out at 500 mm of water level and subsequently subjecting the vehicle to city drive and high drive profile test of 1000 km. The co-relation was also established with real world failures. Authors also propose design alternatives that shall address metallic noise concern due to water entry. Based on the results of this proposed methodology, the robustness of the DMF could be improved. The paper explains the typical robustness measures needed inside the DMF to avoid real-world NVH failures and the test methodology to evaluate the same.
The goal of reducing fuel consumption and CO2-Emission is leading to turbo-charged combustion engines that deliver high torque at low speeds (down speeding). To meet NVH requirements damper technologies such as DMF (Dual Mass Flywheel) are established, leading to reduced space for the clutch system. Specific measures need to be considered if switching over from SMF (Single Mass Flywheel) to DMF [8]. Doing so has an impact on thermal behavior of the clutch system, for example due to reduced and different distribution of thermal masses and heat transfer to the surroundings. Taking these trends into account, clutch systems within vehicle powertrains are facing challenges to meet requirements e.g. clutch life, cost targets and space limitation. The clutch development process must also ensure delivery of a clutch system that meets requirements taking boundary conditions such as load cycles and driver behavior into account. Relevant load cycles are derived based on feedback and analysis of driver behavior under varying road and traffic conditions. For example, one relevant load cycle is the overriding of the clutch in 1st or 2nd gear in dense traffic condition that causes high thermal clutch load due to heat energy generated at the clutch frictional surfaces. This heat energy is relevant for lifetime or can even destroy the clutch/clutch system if not considered properly within the clutch development process. These load cycles are the input for a simulation based clutch optimization. The virtual optimization process is taking aspects such as thermal and lifetime performance for the given boundary conditions of the system, the available installation space, materials (i.e. friction facing), part geometry and of course the costs into account. This process is based on analytical calculations, thermal and thermal-mechanical simulation and CAD modelling. Recent development in thermal-mechanical simulation methods allow a more application-specific consideration of the thermal behavior of the system, also in the early design phase. To validate simulation results, physical tests were carried out; 1st gear repeat vehicle launches on a gradient and 2nd gear launches on a flat road which includes temperature measurements to determine the rise in temperature until a certain number of cycles is reached. In this paper, the approach for clutch optimization is shown based on the analysis of two different clutch sets of the same size including experimental results based on vehicle measurements.
This paper investigates the FPGA resources for the implementation of in-cycle closed-loop combustion control algorithms. Closed-loop combustion control obtains feedback from fast in-cylinder pressure measurements for accurate and reliable information about the combustion progress, synchronized with the flywheel encoder. In-cycle combustion control requires accurate and fast computations for their real-time execution. A compromise between accuracy and computation complexity must be selected for an effective combustion control. The requirements on the signal processing (evaluation rate and digital resolution) are investigated. A common practice for the combustion supervision is to monitor the heat release rate. For its calculation, different methods for the computation of the cylinder volume and heat capacity ratio are compared. Combustion feedback requires of virtual sensors for the misfire detection, burnt fuel mass and pressure prediction. Different alternatives proposed in the literature are compared based on their accuracy and implementation requirements. In-cycle closed-loop combustion controllers were previously investigated by the authors. A National Instruments Xilinx Virtex-5 platform was used as a case study for the quantification of the total necessary resources. The resources for the implementation of the different modules and control strategies are studied to determine the hardware requirements. The results show that the total number of slices is the main limiting factor on the consumed FPGA resources. The quantification of the required hardware provides guidance on how to select an FPGA to implement the different in-cycle combustion control alternatives. This permits to evaluate the total cost of the system as a trade-off between the increased efficiency by the closed-loop combustion control and the cost for its implementation.
Ensuring continuous electrical power within mission-critical facilities is top of mind for today’s facility managers, data center operators, hospital IT managers, and electrical engineers. Thoughtful planning, design, equipment selection, and maintenance of an organization’s power infrastructure is vital for continuous operations. According to U.S. Energy Information Administration findings, typical utility customers experienced nearly six hours of power interruptions in 2018 in the U.S., largely a result of severe weather or devastating wildfires. With businesses losing upwards of $150 million as a result of blackouts (according to the U.S. Department of Energy), protecting against power outages and disturbances is essential. Equally important is incorporating environmentally friendly power solutions to advance organizations’ green initiatives.
In electric vehicles, there is a continuous shift in the charging and discharging of the battery due to energy generation and regeneration. This adds up to the total number of charging-discharging cycles of the battery. This fluctuation amounts to faster battery degradation and life-cycle reduction. Also, we are exploring solutions to improve the low regeneration efficiency of EVs. For example, overall regeneration efficiency from wheels-to-wheels is only around 64% in Tesla Roadster. Even in current EV powertrains, the regeneration efficiency only reaches up to around 75%, which is much lower compared to the potential efficiency of flywheel-based energy storage (FES) as no energy conversion takes place from one form to another. We implemented FESS in a parallel hybrid setup solely for regenerative braking. Based on the power requirements from the vehicle, the drivetrain smartly switches its power source between the Electric motor and flywheel during the drive cycle. It uses a high-efficiency power transmission system such as half-toroidal CVT or CFT. Based on our simulations using QSS Toolbox on Simulink, an improvement of 2.64% in the range is achieved in the NEDC drive-cycle. We studied another setup where the flywheel is coupled with a generator and performs energy conversion only when the flywheel rotates at rpm range close to its rated-rpm. With a synchronous generator specially designed, an improvement of 2.93% in range is achieved in the NEDC cycle. We developed a novel flywheel design called ‘Centrifugal Flywheel’ similar to a centrifugal clutch with masses and springs. Its moment of inertia reduces with the reduction in kinetic energy and so, the angular velocity reduction is less steep until a point and then reduces more steeply. Based on our simulation, centrifugal flywheel rotates at a high-efficiency energy conversion rpm range for 75% longer time than a conventional flywheel. Graphical comparisons between the conventional and centrifugal flywheel are shown.
The development of energy storage systems has gained increasing interest in recent years, as global energy policies and protocols demand to regulate and use available energy efficiently. Inertia flywheels constitute a simple means of energy storage, which has been integrated into different mechanical systems such as die-cutting machines, internal combustion engines, modern systems such as regenerative braking in automobiles, uninterruptible power systems, etc. In this research work, the design process of a flywheel-based experimental test bench to be used as an up-to 130 kilojouls energy storage capacity, and also to test small capacity internal combustion engines, and to diagnose the performance of engine starters. Setting the requirements and main specifications, the paper presents the followed design process, including the solid modeling, the calculations for the dimensioning of the final concept and prototype. Some experimental performance plots obtained during the preliminary tests performed are presented.
Dual mass flywheel (DMF) is an excellent solution to improve the noise, vibration and harshness (NVH) characteristic of any vehicle by isolating the driveline from the engine torsional vibrations. For the same reason, DMFs are widely used in high power-density diesel and gasoline engines. However, the real-world usage conditions pose a lot of challenges to the structural robustness of the DMF. In the present work, a new methodology is developed to evaluate the robustness of a DMF fitted in a compact sports utility vehicle (SUV) with rear-wheel drive architecture. The abuse conditions (mis-gear, sudden braking, etc) in the real-world usage could lead to a sudden engine stall leading to an abnormally high angular deceleration of the driveline components. The higher rate of deceleration coupled with the higher rotational moment of inertia of the systems might end up in introducing a significantly high impact torque on the DMF. Hence, prolonged usage of the vehicle in abuse conditions could lead to a structural failure of the DMF which needs to be assessed during the development stage of a vehicle. In the present work, the authors propose a unique methodology to assess the structural robustness of any DMF. The methodology is a combination of multiple mis-gear shifts and abuse maneuvers creating a high impact torque. The impact torque throughout the testing was measured to establish a correlation with real-world failures. The effectiveness of the methodology is confirmed by comparing the results of the tested DMFs with the long duration high mileage durability DMFs. Moreover, the duration of the methodology is designed to be extremely short that any DMF could be validated within 2 days. In the present work, based on the results of this proposed methodology, the robustness of the DMF could be improved by modifying the internal child parts of the DMF. The paper explains the typical robustness measures needed inside the DMF to avoid real-world structural failures.
Vehicles with manual transmission are still the most preferred choice in emerging markets like India due to their benefits in cost, simplicity and fuel economy. However, the ever-increasing vehicle population and traffic congestion demand a smooth clutch operation and a comfortable launch behaviour of any manual transmission vehicle. In the present work, the launch performance of a sports-utility vehicle (SUV) equipped with dual mass flywheel (DMF) and self-adjusting technology (SAT) clutch could be improved significantly by optimizing the clutch system. The vehicle was observed to be having a mild judder during clutch release (with 0% accelerator pedal input) in a normal 1st gear launch in flat road conditions. An extensive experimental measurement at the vehicle level could reveal the launch judder is mainly due to the 1st order excitation forces created by the geometrical inaccuracy of the internal parts of the clutch system. Moreover, the forces are amplified by the resonance of the complete driveline with the first eigen mode at 8 to 12 Hz. A detailed study in the 1-dimensional torsional simulation model revealed that the eigen mode frequency of the real-wheel drive architecture is mainly driven by several parameters (mass, inertia, torsional stiffness) of the driveline components. Hence, the 1st order excitation forces were needed to be controlled to improve the launch performance. Based on the detailed design of experiments (DOE), it was evident that the cushion disc stiffness and clutch disc parallelism are the significant contributors to the excitation forces. The launch performance of the vehicle could be significantly improved by reducing the cushion disc stiffness at lower axial load (300 N) and by controlling the clutch disc parallelism within a tight tolerance range. The effect of these modifications on different launch conditions is also explained in detail in the present work. The paper gives a holistic view of improving the launch performance of any vehicle without compromising any other parameter.
Gear rattle is due to impact noise of unloaded gears in transmission having freedom to move in backlash region. Engine order vibrations in the presence of backlash in meshing pairs induce the problem. It is a system behavior wherein flywheel torsional vibrations, the pre-damper characteristics and transmission drag torque plays a vital role in an engine idle condition (hot & cold). Idle rattle is a severe issue, which is highly noticeable in cold condition or after 1st engine crank. Gear rattling observed in idle condition is idle gear rattle or neutral gear rattle, specifically in cold condition is a “Cold idle rattle” and this is one of the critical noise parameters considered for entire vehicle NVH. Damper mechanism in the clutch, is used to serve better isolation (by reducing the input excitation to transmission parts) of vibrations between engine and transmission their by reducing gear rattle intensity. Engine firing order, engine downsizing, down speeding (means high peak torque at low engine speed) and other unbalance masses plays leading role in fluctuation of output torque. Clutch parameters like pre-damper stiffness, hysteresis and wind up angle affects more to the cold idle rattle phenomenon. The gear-rattle phenomenon is also depends on vehicle operating temperatures. Temperature variation affects the frictional drag of transmission, which is a most crucial parameter in clutch Pre-damper characteristics design (input parameter) to address rattle. Through experiments, the effect of temperature variation on transmission drag torque and its effect on clutch pre-damper characteristics, which is sensitive to rattle phenomenon, was established. Clutch designer need to understand the requirements and accordingly optimum pre-damper characteristics need to be defined which would result into acceptable idle rattle. This was demonstrated with the experiments considering different pre-damper characteristics on same powertrain. These experiments will help clutch designers to define correct selection / design of pre-damper in the clutch disc.
Automotive clutches are rotary components which transmits the torque from the engine to the transmission. During the engagement, due to the difference in speed of the shafts the friction lining initially slips until it makes a complete engagement. Enormous amount of heat is generated due to the slippage of the friction lining, leading to poor shift quality and clutch failure. Depending on the road & traffic conditions, and frequency of engagement and disengagement of the clutch, it generates transient heating and cooling cycles. Hill fade test with maximum GVW conditions being the worst case scenario for the clutch. A test was conducted to understand the performance of the clutch, in which clutch burning was observed. The clutch lining got blackened and burning smell was perceived. The friction coefficient drops sharply to a point until it cannot transmit the torque required to encounter the slope. This further worsen clutch slippage and lead to more severe temperature rise. The major reason attributed to the burning was inefficient cooling and less thickness of the flywheel & pressure plate. To address this issue transient CFD simulation is performed. Co-simulation methodology is applied to study how the solid temperature influences the air temperature at different time interval of the cycle. The temperature & convective heat transfer co-efficient data exchange happens across the domains after a fixed time interval mentioned in simulation. The heat generated in the solid components are mapped to the air and cooling effect of the fresh air from the ventilation holes are mapped on the solid. To replicate the exact test scenario varying launch energy, convective heat transfer coefficient and rpm is applied on the frictional discs as compared to the conventional steady state simulation approach where constant heat is applied on the frictional disc neglecting the cyclic variation of heating and cooling. A physical test on vehicle was conducted for hill fade condition by inserting the thermocouples in the clutch housing close to the friction lining to measure the air temperature. The measured air temperature shows good trend of correlation with the predicted temperature.
The present work is focussed on the real-world challenges of a dual mass flywheel (DMF) equipped vehicle in the Indian market. DMFs are widely used to isolate the drivetrain from the high torsional vibrations induced by the engine. While DMFs can significantly improve noise, vibration and harshness (NVH) characteristics of a vehicle, there are multiple challenges experienced in real-world operating conditions when compared with the single mass flywheel (SMF). The present work explains the challenges of using a DMF in a high power-density diesel powertrain for a multi-purpose vehicle (MPV) application in the Indian market. Measurements on the flat-road operating conditions revealed that the DMF vehicle is very sensitive for launch behaviour and requires a higher clutch modulation. Vibration measurements at the driver’s seat confirm that the SMF vehicle could be launched more comfortably at the engine idle speed of 850 RPM. However, the DMF vehicle needs a "launch assist" of an additional 100 RPM to meet the acceptable vibration levels in line with that of the SMF. Further, the gradient launch performance of the vehicle is compared for different gradients (6%, 8%, 12%, 18% and 28%) and the results confirmed that the slip time and launch energy of the DMF variant is ~50% higher than the SMF. Moreover, the DMF vehicle could be launched comfortably only up to 12% gradient whereas the SMF variant could negotiate up to 18% gradient easily. Furthermore, the higher launch energy requirement of the DMF is also responsible for the higher temperature of the clutch system by 33% as confirmed by the temperature measurements inside the clutch housing. The increased temperatures pose a major threat to the robustness and useful life of the clutch system parts. Subjective evaluations reveal that the DMF vehicle is prone to frequent engine stalling in speed-breaker and pot-hole manoeuvres. This is mainly due to the requirement of a fuel cut-off strategy which is usually implemented to avoid DMF spring resonance at low engine speeds. However, the requirement of fuel cut-off strategy is not required for the SMF vehicle and hence it could negotiate varying road conditions without any stalling concern. The present work gives a holistic insight into the mentioned challenges with the detailed objective and subjective evaluation data.
During some critical maneuvers, transmission systems using Dual Mass Flywheel (DMF) may experience overtorques, which could lead to structural damages of the transmission components. In a dual mass flywheel, total inertia is divided into two parts: a primary mass connected to the engine and a secondary mass to the transmission. The torque delivered by the engine is transferred from one mass to the other through a drive plate and a set of arc springs, the latter absorbing the torsional oscillations coming from internal combustion engine and the shocks caused by fast clutch engagements. This paper investigates overtorque issues and proposes a solution based on a torque limiter, consisting of a friction clutch inserted between the two masses, that limits the maximum torque transmitted through it. The basic idea is to replace the classic flat drive plate with a tapered drive plate that functions as a Belleville spring. The experimental analysis carried out on dedicated benches has tested the elastic characteristic of the tapered drive plate, the durability of friction pads and the variation of the slipping torque over time. This article analyzes the torque limiter benefits through a detailed torsional dynamic model implemented in Simcenter Amesim. Overtorque phenomena are excited during cranking-in-gear vehicle launch tests on different slopes. Furthermore, a simplified multi-degree of freedom transmission model developed in Matlab/Simulink is shown; it allows calculating frequency response functions, natural frequencies, mode shapes and overtorque limitation. The comparison between the two models revealed that even the simplified model is capable of predicting the main dynamic aspects involved in the overtorque phenomenon and the positive effect of the torque limiter.
Combustion closed-loop control is now being studied intensively for engineering applications to improve fuel economy. Currently, combustion closed-loop feedback control is usually based on the cylinder pressure signal, which is the most direct and exact signal that reflects engine working process. Although there were some relatively cheap types of in-cylinder pressure sensors, cylinder pressure sensors have not been widely applied because of their high price now. Moreover, the combustion analysis based on cylinder pressure imposes high requirements on the information acquisition capability of the current ECU, such as high acquisition and analog-digital conversion frequency and so on. For developing a low price and feasible technology, a new engine information feedback method based on model calculation and crank angular velocity measurement was proposed. A simplified combustion model was operated in ECU for the real-time calculation of cylinder pressure and combustion parameters. At the same time, the angular velocity of the crankshaft was measured by the crankshaft flywheel end sensor for the indication of real-time cylinder pressure. The first derivative can indicate the peak phase of cylinder pressure. The result from crankshaft sensor was fed back to ECU and used to modify the combustion model for more accurate cylinder pressure curve and peak phase. The combustion parameter from the model was used to enhance the transient control according to the variation of combustion phase. The application of this method has the potential to increase the thermal efficiency compared to the traditional MAP control strategy, and also keeps costs low because of the replacement of combustion pressure sensors.
The new Stage 5 European regulation for Non Road Mobile Machinery has lowered the limits on pollutant emissions for all the categories of internal combustion engines. An interesting alternative to the implementation of sophisticated after-treatment systems is to downsize the engine, and provide the extra power for peak demands with an electric motor, installed in place of the flywheel. The paper explores the potential of this concept, applied to an industrial engine, manufactured by Kohler, and delivering a maximum power of 56 kW@2600 rpm. The study is supported by a comprehensive experimental characterization of the internal combustion engine and of the electric components. A representative duty cycle is also defined, on the basis of a set of measures, taken in real operating conditions. The analysis of this reference cycle is performed by using a GT-Suite model, comparing different power split strategies. It is found that the ICE total displacement can be reduced from 2.5 to 1.9 L (from 4 to 3 cylinders), without any penalization on powertrain performance and weight. A relevant reduction of soot (22%) and NOx (16%) emissions is observed, along with a slight reduction of fuel consumption.
Recent technical advances have enabled flywheel energy storage systems (FESS) to become more compact and able to support higher-power applications. Due to their proven reliability, low cost of ownership, and favorable green environmental aspects, engineers and managers of data centers, hospitals, industrial systems, electric rail, and microgrid applications are reaping the benefits of clean energy storage that flywheels offer.
Three-cylinder engines were launched, given the increasing demand for improved fuel economy and efficiency along with reduced friction and weight. Unlike four-cylinder engines, these engines are not naturally balanced. So, in order to compete with four-cylinder engines, some methods to solve this inherent weakness, such as balance shaft, mass unbalancing of flywheel and crankshaft pulley, or counterweights configuration (angular orientation and correction amount), have been used. Considering the undesirable characteristics of the balance shaft, such as cost, weight, friction, and noise, as well as dynamically inappropriate mass unbalancing method, this research proposes multi-objective optimization of counterweights to reduce vibrations. In this regard, after modeling a three-cylinder engine in constant speed and without the gas force effects, counterweights are optimized by non-dominated sorting genetic algorithm (NSGAII) method, to reduce shaking force, pitch and yaw moments, and bearing loads. Then possibility of removing the balance shaft and mass unbalancing, as the main purpose, with the help of counterweights is shown. Finally, a simple formula aimed at determining counterweights configuration to prevent the implementation of a long-term optimization process for each three-cylinder engine with a new specification is introduced. Due to the 92% reduction in pitching vibration for two similar engines, one with optimized counterweights and the other with mass unbalancing but more bearing loads, optimization is a more appropriate method. Also, with a reduction of about 80% of pitching vibration for two similar engines, one with optimized counterweights and the other with a balance shaft, along with the undesirable characteristics of the shaft, optimization is a good substitute for it.
Gear oscillations are one of the most common sources of Noise, Vibration and Harshness (NVH) issues manifested in automotive powertrains. These oscillations are generated mainly due to impacts of the meshing gear teeth over a broad frequency range. To mitigate NVH phenomena, automotive manufacturers traditionally couple linear tuned vibration absorbers to the driveline. Common palliatives used are clutch dampers and dual mass flywheels, which generally suppress vibrations effectively only over narrow frequency bands. Nonlinear Energy Sinks (NESs) are a class of vibration absorbers with essentially nonlinear characteristics that are designed for dissipating vibration energy over broad frequency ranges (due to the employed nonlinearity). The NES does not have a preferential natural frequency; this is rather characterized by the nonlinear stiffness. An NES functions on the principle of transferring energy between the primary system (e.g. driveline) and the absorber in two ways: (i) the NES induces a unidirectional transfer of the vibration energy excess from the primary system to the absorber and (ii) the NES induces a redistribution of the vibration energy excess in the modes of the primary structure, enhancing the energy dissipation capabilities of the primary structure. This paper presents a study on the use of NESs for reducing oscillations on gear pairs operating at low engine operating speeds. Numerical simulations were performed using a gear pair model equipped with an absorber with essentially cubic nonlinear stiffness, attached to the gear wheel. The stiffness and inertia properties of the absorber were varied with the objective of obtaining the parameter combination that induces significant attenuation of the oscillatory motion of the gear wheel. The occurring motion of the system using different sets of parameters is studied and presented.
In this work, the bearing loads of a flywheel-based kinetic energy recovery system caused by gyroscopic torques and dynamic forces during vehicle maneuvering are investigated. This paper is a follow-up study to a preliminary investigation where the flywheel was assumed to be rigidly supported, thus neglecting the effect of rotor precession. At finite stiffnesses of real bearings, however, the flywheel is enabled to move, due to the compliance of the bearing itself, relative to the vehicle chassis with high angular velocities. Based on the equations for elastic rotor-platform interactions, which relate the vehicle’s roll, pitch and yaw rate with the internal transverse torques acting on the elastically supported flywheel, the radial bearing loads are re-investigated in this work for some selected standardized driving maneuvers. The simulation results of the present work are consistent with the results of the rigid model, provided that the elastic approach is subjected to high bearing stiffnesses. However, it is shown that for less rigid bearings the solutions are progressively different. Bearing stiffnesses that produce nutation frequencies of the rotor equal to the natural frequencies of the vehicle’s suspension yield to substantially higher gyroscopic torques. The present study provides an overview of the flywheel bearing loading characteristics caused by gyroscopic torques induced during vehicle maneuvering and by the acceleration of the flywheel’s mass, and includes a parametric study for a range of radial bearing stiffnesses.
Items per page:
50
1 – 50 of 412