Browse Topic: Downsizing
The implementation of enablers on a luxury sport utility vehicle is used to illustrate the development process for reduction of road noise. The vehicle in this case study was launched into production with two tuned mass dampers for reduction of low frequency road noise content which was amplified by frame modes. Additionally, resonators were integrated into the wheels (rims) to address the dominant cavity resonance frequencies. The results of this successful production implementation are illustrated herein. An RNC (road noise cancellation) system was integrated into the case vehicle to assess its performance relative to the passive enablers listed above. This production representative (embedded software solution) RNC system utilized the vehicle’s existing audio system for creation of active noise to cancel noise content which was predicted using accelerometers mounted to the vehicle chassis. A comparison of in-vehicle noise indicated a significant reduction at low frequencies (at all seating locations) when utilizing the active noise control solution. These noise improvements are coupled with a vehicle mass reduction of greater than 4 kg, when compared to the passive enabler solution.
The prime target of IEA (international energy association) to reduce global average emission by 50% in 2030 has prompted focused R&D on automotive emission reduction as well as NEV (new energy vehicles). Of these strategies, engine downsizing constitutes the group of strategies employed to meet lower emission and fuel consumption targets in IC engines. Downsizing strategies have been proved successful in reducing emissions. There is widespread trend of downsizing existing engines with a goal to produce lower emissions along with equal or better performance. To achieve the stated goals downsized engines are usually charged or employ higher compression ratios. This raises NVH as well as structural issues that need further analysis. While the concept of downsizing has been studied in deep, its structural effects and NVH related issues are of concern. This paper throws light into different engine downsizing strategies and their effect on NVH. The variations in unbalanced forces, increase in higher frequency excitations due to use of higher compression ratios, noise and vibration challenges related to turbocharging are discussed with respect to its NVH and structural aspects. A prevalent approach of reducing number of cylinders adds to concern of NVH engineers as unbalanced forces increases with odd number of cylinders. The effect of gas pressure and inertial forces on overall vibration levels are discussed in detail. An analytical approach to calculation of unbalanced forces, various testing and CAE methodologies for optimization of vibration and noise responses is discussed. Finally, comparison of a downsized single cylinder diesel engine with its base engine and strategies adopted is presented
Small engines are considered as independent power units with less than 25 horsepower of power output. They are commonly used in construction and industry appliances, as Electric Generators, Hydraulic pumps, and in homologated racing series. The work presented in this document evaluates the mechanical attributes of a small engine piston as a pressure of 3.1 MPa is applied to the top surface. The methodology used aims to create a series of improvements such as mass reduction and geometry optimization, keeping the initial mechanical properties of the Aluminum A380 piston. To achieve this, a comparison between three iterations of SOLIDWORKS® Topology Optimization Analysis is made. Each iteration contains the same two constraints, two loads applied to the body and a geometric fixture. The constraints include a constraint for region preservation and a value of at least 10% of mass reduction for each iteration. The loads include a load applied on the top end of the piston and a load applied on the external area of the skirts. Lastly, the fixture is at the center of the body, simulating a critical scenario. To create a validation of the topology optimization results of each iteration, a finite element analysis was held to found where the minimum and maximum stress and strain parameters were placed and validate the analysis of geometric changes created by topology optimization. This comparison results in the creation of complex geometries where conventional manufacturing methods do not represent a viable option. Additive manufacturing and its different alloy metals with different mechanical properties offer a method in which these geometries can be manufactured since topology optimization offers a new range of mechanical properties using less amount of material to create a body capable of filling the needs of performance and resistance.
The optimization of the exhaust port shape for best mass flow is an excellent opportunity to improve fuel economy, emissions, and knock sensitivity of internal combustion engines (ICE). This is valid for many different types of combustion systems including gasoline, alcohols, alternative fuels such as compressed natural gas (CNG) or hydrogen, and e-fuels. Nowadays, so-called cylinder-head integrated exhaust manifolds (IEM) guide the exhaust gas from the combustion chamber to the turbocharger. This specific design requires lots of strong bends and turnings of the exhaust ports in very narrow space, since they need to be guided through a labyrinth of bolts, water cores, and oil passages. In fact, this challenges the avoidance of increased pressure drops, reduced mass flow rates, and deterioration of port flow efficiencies. The optimization of the individual port by computational fluid dynamics (CFD) is a proper means to minimize or even eliminate these drawbacks. Meanwhile, there are several powerful optimization methods for three-dimensional flows on the market. In this paper, a combined strategy of CFD topology and shape optimization is presented. This method has been applied to several Ford four-valve engine designs with either twin (Siamese) exhaust ports as well as single ports within two separate IEMs. CFD optimizations have been done for various valve lifts resulting in improved mass flow rates by up to 14 % and an improved mass flow balance between the twin exhaust ports. New flow cross-sections such as L-, F-, and T-shapes have been identified. At the end, an initial design of flow-optimized ports has been generated including body-fitted water jacket surfaces. This allows the designer to already start with an optimized exhaust port design. The new workflow is highly efficient, reduces development time, improves result quality, and may reduce the number of expensive prototypes as well as time-consuming test-rig measurements.
In today’s era, due to increasing energy demands, it is necessary to make vehicles lightweight without affecting their strength. In order to achieve this, the subassemblies of the automobile should be optimized. Optimizing the product not only saves energy consumption but also reduces the material required for manufacturing and increases the overall performance of the product. Taking the same as the base, this article focuses on optimization of a straight bevel gear pair used in automotive differential and performing finite element analysis (FEA) to validate its results. FEA is carried out on the optimized bevel gear to check its durability, and topology optimization is performed on the optimized gear to reduce the mass. Finally, the optimized gear is checked for fatigue. For design optimization, nonlinear multi-objective problem is formulated with a number of teeth and modules as the design parameters. Nondominated Sorting Genetic Algorithm (NSGA)-II algorithm is chosen for optimization. Also multi-body dynamics is performed on the design optimized and topology optimized gear, and the results are compared to understand the effects of weight reduction in the gear with respect to (wrt) vibrations. Design Optimization is accomplished using MATLAB 2018 optimization toolbox, finite element analysis and topology using ANSYS V16.0, and multi-body dynamics using MSC ADAMS 2016.
The brake system is of vital importance when engineering a new vehicle due to its implication with both safety and overall performance. One of the main questions that arise when designing the brake system, not only in terms of performance but also in efficiency and fuel economy is how to make a better brake rotor. When designing the brake rotor, thinking about mass reduction and design optimization is a desire not only for high-performance motorsport, but for daily user applications. The impact on the vehicle performance would lead to improved fuel economy and braking safety. In this work, we propose to exploit some characteristics that can optimize the rotor design to achieve better performance, compared to a baseline design proposed. Some constructive characteristics are kept constant such as the rotor diameter and thickness. The use of computational fluid dynamics (CFD) simulations is considered in this study as a benchmark to future physical prototypes experiments. Within the results, this study aims to quantify the influence of the number of vanes on the brake rotor in terms of performance, but also compare the application of curved vanes with the current straight ones. Trying to find the best number of vanes and ideal angle for curved vanes is a complementary object we propose with this study.
The automotive industry is continuously striving to reduce vehicle mass by reducing the mass of components including wheel bearings. A typical wheel bearing assembly is mostly steel, including both the wheel and knuckle mounting flanges. Mass optimization of the wheel hub has traditionally been accomplished by reducing the cross-sectional thickness of these components. Recently bearing suppliers have also investigated the use of alternative materials. While bearing component performance is verified through analysis and testing by the supplier, additional effects from system integration and performance over time also need to be comprehended. In a recent new vehicle architecture, the wheel bearing hub flange was reduced to optimize it for low mass. In addition, holes were added for further mass reduction. The design met all the supplier and OEM component level specifications. Vehicle testing, however, revealed that the wheel bearing developed high assembled lateral runout (ALRO) and judder. This was due to the tires and wheels being rotated multiple times during a durability schedule. Excessive ALRO will generate high disc thickness variation (DTV) which will lead to pulsation or judder complaints. The root cause of the vehicle level judder was determined to be caused by excessive ALRO and DTV in the brake corner. The major contributor to this LRO issue was plastic deformation of the bearing wheel flange that occurred with use and multiple tire/wheel rotations. This vehicle was validated in multiple regions of the world. Regional differences in vehicle service procedures were observed on the same architecture. Further investigation showed that the regions which performed more wheel rotations and other maintenance observed the vehicle judder, while the other region that did less maintenance did not. To better understand the effect of bearing wheel flange geometry on ALRO in this condition, a lab evaluation was performed. Multiple wheel flange designs were evaluated, including bearing designs with different wheel flange thicknesses and versions with and without weight saving holes. Additionally, bearings with a hybrid aluminum/steel wheel flange were tested.
Ever since mainstreaming of automobiles, engineers are focusing on making the vehicles better by means of making them more efficient, powerful and less polluting. In this study, venues of improving low end torque via improvement in volumetric efficiency as well as proper selection of turbochargers is done. An in-depth analysis of gas dynamics with respect to valve timing is studied along with the AVL Boost 1D simulation. It was found that volumetric efficiency starts to improve when there is a reduction in exhaust - exhaust valve overlap. There is an improvement found in the fresh air ratio (lambda) as the residual gas content is reduced. After the selection of valve timing, turbocharger optimization is done with comparison between two turbine sizes. Along with turbocharger comparison, technology comparison is also done namely between normal electronic VGT (Variable Geometry Turbo) (bigger turbine) and electronic VGT coupled with waste gate (smaller turbine). Dynamic as well as static performance is compared on vehicle level as well as testbed level. Time to torque (TTT) value was measured for the turbos and performance was compared for different lambda limits. A MATLAB tool was programmed to predict the vehicle level performance from the TTT values. The performance was validated on vehicle level as well. In summary, better low-end response was observed with smaller turbine size with 5% improvement in low end volumetric efficiency and similar efficiency at rated power.
Over the years, Internal Combustion engines have evolved drastically from large naturally aspirated engines to small sized forced aspiration engines which have a power output comparable to that of higher capacity engines. Engine downsizing has become more prominent in the present world due to higher focus being exerted on Fuel Economy and tighter emission norms. In the process of achieving these highly efficient engines, their cooling systems are also designed to handle the higher thermal operating conditions. This leads to a negative impact on the cold NEDC cycle by resulting in a longer warmup periods to get the engine upto its optimum operating temperature. This has a major effect on both the combustion efficiency as well as the frictional resistance of the engine. Switchable coolant pumps are one way to address this problem by creating zero flow conditions to warmup the engine by restricting any unnecessary heat rejection and improving the in-cylinder temperature. Since cold NEDC has become the global standard to assess a vehicle’s fuel economy and emissions, we have conducted a study to assess the overall energy distribution across the cycle & effect on Fuel economy & emissions due to the usage of a switchable coolant pump, and also on how it’s potential can be maximized by coupling it with alternate strategies to meet CAFÉ 2022 regulations.
Complex FEAD system in modern powertrain is reality today due to demanding regulation, hybrid powertrain and increasing customer expectation. Gasoline engines are going to be preferred over diesel engines specially for passenger car application. These downsized engines lead to increase engine excitation and so to higher dynamics. Use of overrunning alternator pulley (OAP) is globally accepted as cost effective and technically proven product for FEAD system to make it robust by optimizing the system performance such as belt tension, hub load, slippage and vibrations to improve fuel consumption and to reduce engine emissions. OAP is a mechanical device with one-way clutch unit which eliminates the torsional vibrations coming from engine crankshaft and ensures only accelerating proportions of crankshaft forces are transferred to alternator which means reduction in force level of belt drive system. This paper describes the advantage of usage of OAP to achieve reduction in fuel consumption and emissions, to make the FEAD system efficient over the rigid alternator pulley by eliminating the rotational irregularities coming from FEAD system. In this paper, various engine driving conditions have been simulated to assess FEAD system performance in terms of hub load, belt pre-tension, belt slippage and vibrations by comparing rigid pulley and overrunning alternator pulley, followed by engine validation, which shows effectiveness of OAP.
Noise & Vibration refinement of automotive vehicles is becoming important parameter due to its influence on environmental aspect and comfort perceived by occupants. NVH parameters are driving factors in current vehicle design strategy. Drivers comfort is extremely important, and driver’s expectations from commercial and heavy-duty trucks are as good as refined passenger cars. Other trends in commercial vehicle segment such as engine downsizing, weight, cost reduction and meeting stringent emission norms have influenced vehicle design dynamics. These parameters are critical and often contribute to vehicle NVH issues. Considering these new trends in commercial vehicle segment, it becomes challenging for an NVH engineer to provide optimized solutions. NVH issues could be related to the various subsystems such as driveline, axle, transmission steering wheel etc. in the vehicle and its resonant frequencies. In commercial vehicles, driveline design parameters, power train mounting system and secondary isolation of cab mounting system plays vital role in providing optimized solutions to the NVH refinement. This paper represents a case study on a commercial vehicle for low frequency NVH performance evaluation and refinement using experimental techniques to achieve targeted NVH performance. This paper describes optimization of cab mounts and driveline design parameters through DOE method to reduce the vibrations transmitted in a passenger cabin at tactile locations and corresponding cabin noise. The results of the analysis depict the significant improvement in vibration transmitted to the driver’s and passenger locations with reduced stiffness of engine mounts, cab mounts and optimized driveline parameters.
The objective of this study was to evaluate the fuel saving potential of various hybrid powertrain architectures for medium and heavy duty vehicles. The relative benefit of each powertrain was analyzed, and the observed fuel savings was explained in terms of operational efficiency gains, regenerative braking benefits from powertrain electrification and differences in vehicle curb weight. Vehicles designed for various purposes, namely urban delivery, utility, transit, refuse, drayage, regional and long haul were included in this work. Fuel consumption was measured in regulatory cycles and various real world representative cycles. A diesel-powered conventional powertrain variant was first developed for each case, based on vehicle technical specifications for each type of truck. Autonomie, a simulation tool developed by Argonne National Laboratory, was used for carrying out the vehicle modeling, sizing and fuel economy evaluation. Performance based sizing rules implemented in Autonomie were used to determine the component sizes for the hybridized concept trucks. In addition to the conventional baseline, a 48V start-stop system, parallel pre-transmission system and a series plug in hybrid system were considered in this work. This study shows that not all trucks can utilize engine downsizing as part of hybridization strategy. Hybrid trucks designed to match conventional vehicle performance in all functional requirements, will require engines that are comparably sized as the conventional counterparts. Plug in hybrids can have downsized engines and still meet performance goals, as the larger battery packs can be used to assist engine for a longer period of time. Depending on the drive cycle, the observed fuel economy for the hybrid powertrains will vary. It could be comparable to that of baseline vehicle in highway driving while resulting in over 30% fuel savings in more transient drive cycles.
The body strength, stiffness and crashworthiness are the key aspects for the mass reduction of the commercial bus body frame. Heavy computation cost is one of the critical problems by the finite element (FE) method to accomplish a high-efficient multi-objective optimizing design. Starting from this point, in this paper, the surrogate model method is adopted to optimize the electric bus frame to reduce the mass as possible while guaranteeing the side-impact strength. The optimizing objective comprises the total mass and side-impact intrusion while the performances of static strength and stiffness in bending and torsion conditions are chosen as the constraints in optimization. First, an FE model is developed to perform the static strength analysis, modal analysis and side-impact strength analysis. Nine groups of candidate variables are determined as the optimizing design variables by sensitivity analysis. Then surrogate models have been formulated based on the methods of least squares regression (LSR) and radial basis function neural network (RBFNN). The precision of the surrogate models are evaluated and validated by comparing with the FE simulation results. Based on the surrogate models the bus body frame is finally optimized by the multi-objective genetic algorithm (MOGA) method. With the optimized parameters, the performance of the body frame is evaluated by comparing with that before optimizing. It is demonstrated that the design objective of lightweight (mass reduction) has been achieved and the side-impact crashworthiness have been improved as well while guaranteeing the basic performance including the static strength and stiffness.
The development of new components that have a structural commitment and still achieve mass reduction is becoming increasingly complex and sophisticated materials for production for the automotive market for commercial and passenger vehicles. To achieve this level of demand the use of composite materials such as carbon fiber, glass fiber or a compound of the two has become a reality, however the production rate was still considered a problem for medium volume parts (up to one hundred thousand parts per year). The work demonstrates the construction and simulation of a PoC (proof of concept) using these composites in a warm stamp process where the material a thermoset composite plate is preheated to the working temperature, then it is inserted in a tool preheated stamping, remaining closed for a few minutes where the material is consolidated and then the part is extracted already cured without the need for cooling, thus ensuring the projected production tackt compared to the autoclave curing process that can take hours. The PoC was designed with the aim of evaluating stamping conditions such as: spherical conformation, constant cross section and depth reduction, characteristics that are considered classic problems of the stamping process. Therefore, the work presents a viable proposal to produce items for the automotive market for commercial and passenger vehicles.
The Brazilian logistic system constantly aims to increase the efficiency of cargo transportation in its trips. One way is to use a the most volume to allocate the cargo, whit the least gross vehicle weight, in such a way that the transported net weight is higher. That way the highway semitrailers industry looks that their manufacturers develop lighter and robust products, not leaving aside reliability and safety. Through this motivation, this paper has the objective to achieve a study of a comparison on how a van can be used in favor of logistic transportation. Allowing to increase volume by decreasing structural parts of the chassis, and also decreases the weight of the semitrailer by reducing the mass of components through the increase of resistance of the vehicle chassis frame and van, where the van can be a factor that only increases weight to the set.
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