Browse Topic: Brake torque

Items (296)
The purpose of this AIR (Aerospace Information Report) is to provide aircraft and engine designers with a better understanding of helicopter turboshaft engine idle power characteristics and objectives to be considered in the design process. Idle is the lowest steady state power setting. At this setting, the engine typically does not produce enough power to obtain governed output shaft speed (i.e. the shaft speed is determined by the load imposed by the aircraft). In the aircraft, the engine is typically stabilized at this power setting after starting, prior to taxi and for some period of time after rotor shutdown for cool down prior to engine shutoff. Traditionally, the aircraft designer wants idle power scheduled as low as possible and of course, does not want any resulting aircraft operational difficulties such as overcoming the rotor brake. The engine designer, however, desires a higher scheduled power because of the reduced probability of engine operational problems. The attributes of conflicting idle desires are discussed. Other inputs are also considered to establish the engine idle power settings. The information contained herein will assist in the early design phase and ultimately will result in a more optimum match between engine and aircraft requirements.
S-12 Powered Lift Propulsion Committee
This SAE Standard provides test procedures for air and air-over-hydraulic disc or drum brakes used for on-highway commercial vehicles over 4536 kg (10000 pounds) GVWR. This recommended practice includes the pass/fail criteria of Federal Motor Vehicle Safety Standard No. TP-121D-01.
Truck and Bus Foundation Brake Committee
Integrated Regenerative Braking System and Anti-Lock Braking System for Hybrid Electric Vehicles & Battery Electric Vehicles2020-01-08464/14/2020
This paper describes development of an integrated regenerative braking system and anti-lock brake system (ABS) control during an ABS event for hybrid and electric vehicles with drivelines containing a single electric motor connected to the axle shaft through an open differential. The control objectives are to recuperate the maximum amount of kinetic energy during an ABS event, and to provide no degraded anti-lock control behavior as seen in vehicles with regenerative braking disabled. The paper first presents a detailed control system analysis to reveal the inherent property of non-zero regenerative braking torque control during ABS event and explain the reason why regenerative braking torque can increase the wheel slip during ABS event with existing regenerative braking control strategies. Then, the regenerative brake control problem during ABS events is formulated with a unified control system architecture where the regenerative braking torque is coordinated with the friction braking torque of ABS system. An integrated closed loop based wheel slip control including both regenerative braking control loop and friction braking control loop during ABS event, referred to as RBS-ABS event control, is developed. The maximum regenerative braking is achieved and optimal vehicle braking performances and vehicle stability are maintained during ABS event. Finally, simulation tests are provided to illustrate RBS-ABS event control as an effective solution to satisfy desired wheel slip with the same level of stop distance in comparison with that of ABS control only while performing energy recuperation.
Yao, YixinZhao, YananYamazaki, Mark
Effect of Stator Surface Area on Braking Torque and Wall Heat Dissipation of Magnetorheological Fluid Retarder2020-01-09374/14/2020
Magnetorheological fluid (MRF) is used as the transmission medium of the hydraulic retarder. The rheological properties are regulated by changing the magnetic field to achieve accurate control of the retarder's braking torque. Under the action of the external magnetic field, the flow structure and performance of the MRF retarder will be changed in a short time. The apparent viscosity coefficient increases by several orders of magnitude, the fluidity deteriorates and the heat generated by the brake cannot be transferred through the liquid circulation, which will affect the braking torque of the retarder. Changing the surface area of the stator also has an influence on the braking torque of the retarder and the wall heat dissipation. In this study, the relationship between the braking torque of the MRF retarder and the stator surface area of the retarder was analyzed. In addition, phase change materials were used to directly dissipate heat on the retarder surface to improve the heat dissipation rate of retarder and improve the stability of the retarder's braking torque. In order to study the effect of stator radius on braking torque of MRF retarder under an external magnetic field, a braking torque model was established based on MRF with Bingham model properties, and a heat transfer model of wall phase change material was established to analyze the relationship between heat transfer and braking torque of MRF retarder. The results show that the braking torque of the MRF retarder increases rapidly with the increase of the radius outside the effective working area of MRF, which increases faster at high speed and increases the stator wall surface heat dissipation, but the rate of heat dissipation increases relatively slowly. The wall surface with a heat pipe can take away the heat generated by the retarder and cool the retarder. Under the appropriate stator surface conditions, phase change materials are used on the wall surface of the retarder to dissipate heat, which improves the stability of the braking torque of the retarder and promotes the development of MRF retarder to high power.
Liu, ZhiQiangTan, GangfengTian, ZhongpengZhou, MiAgyeman, PhilipFrimpong, Justice
Development challenges of hydraulic brakes for commercial vehicles2019-36-00131/13/2020
The automotive research and development environment is increasingly challenging and complex, full of new technologies, regulations and customized customer needs. In addition, the cargo transportation market is very dynamic and competitive, becoming complex the strategies for companies in this segment. According to Anfavea (2018), this trend, especially in large urban centers, has driven the intention to use light commercial vehicles to capillize deliveries in destinations with a high demographic concentration and traffic limited to medium and heavy vehicles. In this scenario, the demand for diversified products is increasing in order to overcome the main tradeoff: “minimizing the size of the trucks and maximize the load capacity”. It brings the number of complex projects. The brake system is greatly impacted in these developments mainly because light commercial vehicles are situated in a weight range that we can call "identity crisis" if on the one hand they need an upgrade compared to a conventional car and use the hydraulic brake on the other one need a downgrade of a medium or heavy truck that brings robustness and pneumatic brakes. The definition of the type of assistance is a determining factor, hydraulic brake; pneumatic brake or a hybrid brake (air over hydraulic). Each type has its advantages and disadvantages, which are directly related to the vehicle's application such as installation package, serviceability, service brake costs and performance and especially parking brake. This work shows the study and development of the brake system including the detailed presentation of a dry caliper, implemented as disruptive innovation technology. It also has a new concept applied to a commercial vehicle, developed in Brasil and used as footprint own knowledge for the specific needs of the market and provides a very cost-benefit commitment for the customer, yet brings the wished confidence of the parking brake function for drivers.
Vetter, Narã VieiraCarlos de Oliveira, AntonioFontes, Eduardo Henrique SouzaNogueira, FelipeFonseca, Guilherme HenriqueNuss de Souza, Luis FernandoOliveira dos Reis, Rodrigo deManenti, Vangelo Cardoso
Analysis of Active Collision Avoidance Performance Based on Cooperative Regenerative Auxiliary Braking System2019-01-502711/4/2019
Active collision avoidance can assist drivers to avoid longitudinal collision through active brake. Regenerative braking can improve the driving range and braking response speed. At this stage, conventional hydraulic braking system limits the implements of above technologies because of its poor performance of response speed and coordinated control. While the brake-by-wire system is a better actuator that can fulfill requirements of automotive electric and intelligent development due to its rapid response and flexible adjustment. However, the system control algorithm becomes more complicated with introduction of regenerative braking and active collision avoidance function, which is also the main problem solved in this paper. First, a new type of cooperative regenerative auxiliary braking system (CRABS) of intelligent electric vehicles, which integrates the functions of brake-by-wire, regenerative braking and active collision avoidance, is proposed, for purpose of analyzing the improvement of active collision avoidance performance after the introduction of regenerative braking. The design of the system focuses on the Electro Hydraulic Brake (EHB) unit, control strategy of active collision avoidance and brake force distribution. Then, modeling and simulation are done to validate the feasibility of the proposed system scheme. Based on the Autonomous Emergency Braking (AEB) test procedures of European New Car Assessment Programme(Euro-NCAP), the simulation analysis scheme is made including simulation process, simulation test conditions and evaluation indicators. Finally, the hardware-in-loop (HIL) test bench based on the real motor system is set up to validate the conclusion drawn in the simulation analysis. The results show that compared with the conventional hydraulic braking system, CRABS system proposed in this paper conducts faster in braking response and closer to the ideal braking distance, and the performance of active collision avoidance is improved.
Hou, XiaohuiZhang, JunzhiZhang, ZhongshiHe, Chengkun
The Improvement Brake’s Qualities of Vehicle by Developing the Method of the Choosing Frictional Pairs of the Brakes Mechanisms2019-01-21459/15/2019
One of the reasons for the large number of road accidents on highways in Ukraine [1] is the instability of the braking properties due to the unstable characteristics of the brake mechanisms’ friction pairs. The manufacturer produces new automobiles with installed brake pairs (brake pads and their counter bodies), which have passed long-term tests for the stability of the friction coefficient and braking forces distribution of between the axles. This ensures the compatibility of the friction pairs characteristics for front and rear brake mechanisms according to the criteria of heat resistance. During operation, instead of worn-out brake pads, brake discs and drums, drivers can purchase new ones, manufactured as spare parts. However, in the well-known literature there are no methods that allow to check the compatibility of the friction pairs characteristics for front and rear brake mechanisms according to the criteria of heat resistance. In the article a method for choosing a set of friction pairs of brake mechanisms for passenger car during operation is proposed. Assessment of the compatibility of the friction pairs characteristics for front and rear brake mechanisms was carried out according to the criteria of heat resistance.
Podrigalo, MikhailKlets, DmytroKholodov, MykhailoBogomolov, ViktorTurenko, AnatoliyMolodan, AndriiRudzinskyi, VolodymyrTarasov, YuriiMykolai, AloksaHatsko, Vasyl
Brake Rotor Corrosion and Friction Cleaning Effect on Vehicle Judder Performance2019-01-21159/15/2019
Brake disc corrosion has emerged as an important field of study within the automotive industry due to the wide range of lining materials that are currently used worldwide, and their inherent rust-cleaning properties. The presence of oxide layers irregularly deposited on the cast iron disc surfaces usually leads to a forced, braking-induced vibration that can reach the driver’s position as a pronounced annoyance. Hence, the friction material composition directly impacts on the judder performance during the early corrosion-removal stage. This study incorporates both dynamometer and vehicle tests into the definition of a predictive methodology that allows corrosion-induced vibrations to be investigated at both system and vehicle levels. The oxide film is artificially generated by means of a salt spray chamber under steady-state climate conditions in order to guarantee a repetitive and robust procedure. The vibration response of the system is objectively evaluated in the form of caliper accelerations and pressure (BPV) / torque (BTV) oscillations throughout a reduced rust-removal test sequence composed of 30 snubs; basic spectral and order analyses are conducted with the gathered data. Furthermore, vehicle-based results are correlated with the subjective ratings that an expert driver gives to the different vibrations perceived at chassis level. The in-service roughness of the oxide layer, on the other hand, is indirectly monitored by using a couple of non-contacting capacitive sensors that measure the variation in disc thickness (DTV). Ultimately, this paper is intended to characterize the inherent corrosion-cleaning capability of different friction materials -paying special attention to the presence of copper-, as well as revealing their impact on the vehicle judder subsequently induced during the actual removal of the oxide layers.
Molina Montasell, NarcísFerrer, Bernat
Research on Constant Speed Control Strategy of Water Medium Retarders for Heavy-Duty Vehicles2019-01-13044/2/2019
Hydraulic retarders are extensively used in heavy-duty vehicles because of their advantages, such as their large braking torque and long continuous operating hours. They can reduce the vehicle velocity by converting the kinetic energy of a traveling vehicle to the thermal energy of the working fluid. The water medium retarder is a new type of hydraulic retarder with the characteristics of high power density and simple structure. It uses the engine's coolant as the working medium, and the heat is directly taken away by the vehicle cooling system. Therefore, the heavy-duty vehicle can achieve long-term continuous braking during the downhill process. One of the main functions of water medium retarder is driving downhill at a constant speed which determines whether the vehicle drives stably and safely. Therefore, studying the constant-speed control strategy during downhill driving is particularly important. In this paper, the structure and working principle of water medium retarder and the dynamic characteristic are analyzed. The dynamic models of vehicle and water medium retarder are established based on dynamic analysis during downhill process. The braking process that involves the water medium retarder is divided into three stages. Then the constant speed controller of water medium retarder which include three control algorithms is designed, respectively, PID algorithm, fuzzy algorithm and fuzzy-PID algorithm. The vehicle dynamic model and the constant speed control model of water medium retarder are established using MATLAB/SIMULINK. The simulation has been carried out and the comparative analysis of three algorithms mentioned above is conducted. The simulation results show that three controllers designed in this paper can quickly and accurately calculate the target filling ratio, fuzzy controller has better constant torque control performance, and the vehicle speed error is significantly reduced, which improves the stability of the vehicle during downhill process.
Lei, YulongSong, PengxiangFu, YaoWang, YuhaiZhang, Yuchen
Properties and Limitation of an Oxide Coated Aluminum Brake Rotor2018-01-187710/5/2018
The electrification of the powertrain and the thereto related recuperation of the electric engine saves the energy in the battery and thus reduces the thermally dissipated brake energy, which leads to lower brake rotor temperatures compared to combustion engine vehicles (ICEVs). These new conditions enable to reconsider brake disc concepts. Including lightweight design in heavy battery electric vehicles (BEVs) and the increasingly reliant corrosion resistance of brake rotors, Aluminum is a promising approach for new brake disc concepts. In the past, Aluminum brake disc concepts have already been deployed. For instance Aluminum Metal-Matrix Composite (Al-MMC) concepts in the Lotus Elise S1 and on the rear axle of the Volvo V40 [1]. The presented concept is a different approach and separates the friction system from the bulk Aluminum brake disc, achieved by coating of the friction rings. By locally reinforcing the friction rings, the good machinability and ductility of the base body is maintained and simultaneously the friction surface is sufficiently protected to resist the frictional loading during a brake application. In this work, fundamental studies on a brake dynamometer were conducted and supplemented by microstructural investigation to identify damage mechanisms and to judge the technical application of the concept.
Gulden, FlorianGramstat, SebastianStich, AntonHoppel, Heinz WernerTetzlaff, Ulrich
A New Model Describing the Formation of Heat Cracks in Brake Discs for Commercial Vehicles2018-01-188210/5/2018
During the development process of brake discs for commercial vehicles, heat cracks are a frequent problem. Since no profound model to forecast the occurrence of cracks has been presented yet, their prediction is hardly ever possible. The standardized heat crack test puts the brake disc under severe thermomechanical load and therefore forces it into cracking. In this paper, results from a series of heat crack tests on the dynamometer are presented, which provide insight into the hidden processes that accelerate or slow down the heat crack propagation in brake discs. This includes an extensive experimental setup using a thermographic camera, a set of capacitive displacement sensors, a pyrometer, and sliding thermocouples as well as a unique eddy-current heat crack detector that was developed at TU Darmstadt. Continuous monitoring of disc deformation, surface temperature, and crack propagation at high sampling rates provides the base for a new, profound causal model. The model describes a chain of effects including the qualitative and quantitative influence of the surface temperature distribution to local crack propagation rates in connection with local deformation and coning of the disc. Therefore, spatiotemporal patterns of thermal and mechanical distortions of the disc are compared to each other and to the crack pattern in time and frequency domain. The observation of local hardening effects as well as microstructural transformations in regions of high crack growth completes the model. Furthermore, relations between crack propagation and brake disc design are evaluated, which reveal the influence of the cooling channel pin configuration to the crack propagation. Finally, possible future applications of the model are shown, regarding its ability to forecast the cracking tendency of a certain brake disc design during finite element analysis as well as its integration into the development process of brake discs.
Bilgic Istoc, SamiWinner, Hermann
Performance Evaluation of Two Wheeler Brake System Using Coupled Thermo-Mechanical Simulation2018-01-189610/5/2018
Safety aspect has been a key requirement in designing braking system. However, non-safety aspect like NVH and thermal performance are gaining equal importance. High engine capacity (cc) motorcycles are prone to thermal and NVH issues as braking energies are more. Therefore, virtual validation of brake disc system by considering both dynamic and thermal load with predefined assumptions is a toughest challenge when confronted with reality boundary conditions. Thus, the paper comes in a unique way of coupling dynamic and thermal load executed between multi body dynamics (MBD) and heat transfer equation which will convey results closer to real time scenario. MBD solves motion and the dynamic influence on heat transfer is calculated using “sliding boundary condition”. A series of repeated braking condition are performed on front brake disc of motorcycle. The results obtained from the analysis shows critical temperature rise. As a consequence, disc thickness variation (DTV) due to thermal expansion are aggregated when coupled with dynamic friction. DTV will prove to be critical in concerning NVH and durability issues of brake disc. Braking conditions are numerically simulated on finite element method (FEM) using nonlinear approach and results are summarized with test data.
Sukumaran, SurajKalani, DineshSuryavanshi, YogeshKokane, GirishDeshpande, MoreshKharul, Ravindra
Investigation of Flame Propagation Description in Quasi-Dimensional Spark Ignition Engine Modeling2018-01-16559/10/2018
The engine development process has been enhanced significantly by virtual engineering methods during the last decades. In terms of in-cylinder flow field, charge flow and combustion modelling, 3D-CFD (three dimensional) simulations enable detailed analysis and extended investigations in order to gain additional knowledge about design parameters. However, the computational time of the 3D-CFD is an obvious drawback that prevents a reasonable application for extensive analysis with varying speed, load and transient conditions. State-of-the-art 0D (zero dimensional) approaches close the gap between the demand of high computational efficiency and a satisfying accordance with experimental data. Recent improvements of phenomenological combustion approaches for gasoline spark ignition engines deal with the consideration of detailed flow parameters, the accuracy of the laminar flame speed calculation and the prediction of the knock limit. Little attention has been given to the influence of different combustion chamber designs on the prediction capability so far. This leads to an often used simplification consisting of a combustion chamber modeled as a disk and an acceptable inaccuracy of combustion modelling. With an increasing deviation of the surrogate combustion chamber from the investigated real chamber, the prediction capability becomes insufficient. This effect is intensified by the shift of the combustion process to a fast combustion nearby the top dead center (TDC), typical for high performance engines with advanced ignition timing for maximum brake torque. In order to improve the model accuracy, this examination highlights the effect of different descriptions of the flame propagation in 0D combustion modeling. Two calculation paths are introduced. On the one hand the flame propagation description is determined by the combustion chamber geometry prior to the model calibration process, and on the other hand the flame data is derived from measured data after the model calibration. The forward path considers exemplary combustion chamber designs, e.g. through different piston cavities, their effect on the flame front as well as on the 0D model results. A deep analysis via 3D-CFD of the flame propagation reveals characteristic points, which are related to different geometrical aspects. Despite the consideration of the flame maps, the related changes of the charge motion are calculated through 3D-CFD and transferred to 0D. The improvement of the predictive capability through the flame data and flow parameters is investigated by experimental data of two different high performance engines. The backward path deals with the calculation of flame propagation from measured cylinder pressure data. On the one hand this gives the opportunity to analyze the combustion process with the knowledge gained by the previous introduced characteristic aspects, on the other hand it creates flame maps that are simple to use. Latter improve the 0D combustion model accuracy even without knowing the exact geometry.
Malcher, SimonBargende, MichaelGrill, MichaelBaretzky, UlrichDiel, HartmutWohlgemuth, SebastianRöttger, Gordon
Understanding the Adverse Effects of Inlet Valve Deposits on SI Engine Operation, through a Novel Technique to Create Surrogate Deposits2018-01-17429/10/2018
For gasoline spark ignition engines, port fuel injection (PFI) on a global basis remains the most common type of fuel delivery. When operated with lower quality fuels and lubricants, PFI engines are prone to suffering from the build-up of harmful deposits on critical engine parts including the inlet valves. High levels of inlet valve deposits (IVDs) have been associated with drivability issues like engine stumble and hesitation on sudden acceleration. Fuels formulated with the appropriate level of deposit control additive (DCA) can maintain engine cleanliness and even remove deposits from critical components. This study, involving a single cylinder research bench engine operated in PFI injection mode and heavily augmented with measurement equipment, aimed to gain a deeper understanding of the detrimental impacts of IVDs on engine efficiency and performance. Guided by 3D-scans of carbonaceous IVDs sourced from industry standard tests conducted per ASTM D5500, surrogate metal deposits were generated, utilizing the novel approach of powder-laser-cladding (PLC). The modified inlet valves were evaluated in the research engine across eight different speed load conditions including full-load. Using this approach and building on the results previously obtained on the industry standard Mercedes-Benz M111 bench engine, it was possible to quantify an increase of more than 3 crank angle degrees in combustion duration at a 95% level of statistical confidence, due to the presence of the simulated IVDs. Similarly, IVDs limited the quantity of air entering the cylinder which reduced power output of the engine for a given condition by 1.9% at a 99% level of statistical confidence. These effects were corroborated by supporting secondary metrics such as exhaust temperature increases and peak pressure reductions. Overall, it was shown that the presence of IVDs shifted the center of combustion away from the engine’s optimum point for efficiency as defined by the maximum brake torque (MBT) spark timing.
Glawar, Andreas F. G.Ziman, Pauline R.Wu, KaihuaNatarajan, VinodWolgast, Eike J.Dankers, CarolinGroves, Adrian P.
Experimental Investigation of Low-Frequency Vibration Patterns in Automotive Disk Brake Systems: Utilization Study for Modal Simulation Methods2018-01-15136/13/2018
Increasing demands on automotive comfort as well as diminishing vehicle noise levels draw new attention towards low-frequency vibration and noise issues of disk brake systems such as creep groan and moan. In view of this problem, the experimental investigation of relevant phenomena is within the scope of this article. The related experiments concerning two different setups have been performed at a drum driven suspension and brake test rig. Both assemblies consisted of a front axle corner including all parts of the integrated brake system. In order to gain understanding of characteristic triggering mechanisms and fundamental subsystem interactions, and moreover, to verify the suitability of modal methods for simulative evaluations of creep groan or moan, specifically elaborated Operating Deflection Shape (ODS) techniques have been applied. Via analyses of four different creep groan emergences, global stick-slip cycles between disk and pads are revealed. For two dissimilar vibrations in the typical frequency range of moan, mechanisms rather associated with dynamic instabilities are identified. Based on measurement results and further theoretical considerations, the suitability of a disk brake Complex Eigenvalue Analysis (CEA), which is a linear modal simulation method designated to efficiently evaluate disk brake squeal noise, is verified with respect to the relevant friction-induced low-frequency phenomena. Even though the disk brake CEA is inappropriate to estimate a highly non-linear behavior such as involved in all four creep groan signatures, its application for accompanying damped natural oscillations as well as for both observed moan appearances is plausible. By investigation of characteristic pad vibration patterns and speeds belonging to the disk rotation, generic parameter spaces for the utilization of modal methods on harmonic low-frequency phenomena are deduced.
Pürscher, ManuelHuemer-Kals, SeverinFischer, Peter
A Braking Force Distribution Strategy in Integrated Braking System Based on Wear Control and Hitch Force Control2018-01-08274/3/2018
A braking force distribution strategy in integrated braking system composed of the main braking system and the auxiliary braking system based on braking pad wear control and hitch force control under non-emergency braking condition is proposed based on the Electronically Controlled Braking System (EBS) to reduce the difference in braking pad wear between different axles and to decrease hitch force between tractors and trailers. The proposed strategy distributes the braking force based on the desired braking intensity, the degree of the braking pad wear and the limits of certain braking regulations to solve the coupling problems between braking safety, economical efficiency of braking and the comfort of drivers. Computer co-simulations of the proposed strategy are performed. The braking force distribution strategy is verified under condition of equal wear of braking pad, condition of greater wear on the front axle of tractor and condition of greater wear on the rear axle of the tractor. The simulation results show that the proposed strategy balanced the braking pad wear by regulating the braking cylinder pressure of each axle and ensured the same braking distance under different wear conditions of braking pad. Under unloaded or loaded conditions, each axle braked according to the desired braking intensity and reached the control objective that the same braking pedal opening rate is in accord with the same braking intensity. Under different load conditions, the strategy ensured the same braking distance and reduced the hitch force, which definitely enhanced the braking safety, economical efficiency of braking and the comfort of drivers.
Zheng, HongyuLiu, ChenWang, Linlin
Optimal Torque Allocation for Distributed Drive Electric Skid-Steered Vehicles Based on Energy Efficiency2018-01-05794/3/2018
Steering of skid-steered vehicles without steering mechanism is realized by differential drive/brake torque generated from in-wheel motors at left and right sides. Compared to traditional Ackerman-steered vehicles, skid-steered vehicles consume much more energy while steering due to greater steering resistance. Torque allocation is critical to the distributed drive skid-steered vehicles, since it influences not only steering performance, but also energy efficiency. In this paper, the dynamic characteristics of six-wheeled skid-steered vehicles were analyzed, and a 2-DOF vehicle model was established, which is important for both motion tracking control and torque allocation. Furthermore, a hierarchical controller was proposed. Considering tire force characteristics and tire slip, the upper layer calculates the generalized force and desired yaw moment based on anti-windup PI (proportion-integral) control method. On the fundamental of dynamic characteristics of skid-steered vehicles and electric motor efficiency characteristics, the lower layer utilizes different optimal torque allocation strategies based on energy efficiency at different driving conditions, namely, straight line driving condition and steering condition. The control results show that the motion controller can track the reference yaw rate accurately and at the same time much energy can be saved by proposed torque allocation strategy.
GAO, LetianXiong, LuGao, XiangYu, Zhuoping
Parallel Thermal Management System of the Water Medium Retarder2018-01-07774/3/2018
The thermal management system of the water medium retarder using engine coolant (water and ethylene glycol) as transmission medium, omits oil-water heat exchanger in the structure. When the hydraulic retarder is operated, the valve is connected with the retarder and water pump, and then the engine coolant enters the working chamber. The kinetic energy of the vehicle is converted into internal energy of the coolant, and the heat is discharged to the external environment through the engine thermal management system. The braking torque of the water medium hydraulic retarder is determined by the water medium flow rate in the working chamber. The smaller the valve opening degree, the greater the braking torque and the faster the heating transmission fluid. Small valve opening is not conducive to the loss of heat. It will affect the normal working of the engine and hydraulic retarder. In this paper, the thermal management system of the water medium hydraulic retarder is independent of the engine. Hydraulic retarder can be controlled individually so that to improve the auxiliary braking performance. Firstly, the independent thermal management system is designed according to the heat dissipation requirement of the hydraulic retarder. Secondly, the heat transfer of the hydraulic retarder thermal management system is analyzed. Finally, compare to the thermal management system of the traditional water medium retarder and the paper. The results show that the thermal management system of parallel water medium hydraulic retarder can effectively use the radiator cooling capacity, and reduce the working temperature of the water hydraulic retarder.
Gao, XinLei, YulongChen, WeiCui, GuokaiZhong, Lei
Systematic Experimental Creep Groan Characterization Using a Suspension and Brake Test Rig2017-01-24889/17/2017
Vehicle road tests are meaningful for investigations of creep groan noise. However, problems in reproducing experiments and partly subjective evaluations may lead to imprecise conclusions. This work proposes an experimental test and evaluation procedure which provides a precise and objective assessment of creep groan. It is based on systematic corner test rig experiments and an innovative characterization method. The exemplary setup under investigation consisted of a complete front wheel suspension and brake system including all relevant components. The wheel has been driven by the test rig’s drum against a brake torque. The main parameters within a test matrix were brake pressure and drum velocity. Both have been varied stepwise to scan the relevant operating range of the automobile corner system for potential creep groan noise. Additionally, the experiments were extended to high brake pressures, where creep groan cannot be observed under road test conditions. The measurements with creep groan showed vibration characteristics of a non-linear stick-slip effect, particularly at high brake pressures. A novel method to detect and evaluate creep groan events within a large number of systematic measurements has been developed and tested. It uses the characteristic patterns of acceleration signals which are analyzed in the frequency domain. The main evaluation results are displayed collectively in multi-dimensional maps. Such Creep Groan Maps (CGM) show vibration intensity levels and relevant frequencies in dependence of brake pressure and drum velocity. An overall Creep Groan Index (CGI) scores the groaning tendency of a whole setup by a single number. Its calculation is based on the acceleration signals across the observed test matrix as well. CGM and CGI both allow a simple and objective comparison of different mechanical and/or tribological setups as well as parameter influence studies.
Pürscher, ManuelFischer, Peter
Influences of Initial DTV on Thermomechnical Coupling in Disc Brake System2017-01-24929/17/2017
In this paper, the initial disc thickness variation (DTV) of a ventilated disc in automotive brake system is modeled as sinusoidal function of the second order. The transient thermomechanical coupling properties of the brake system is simulated using finite element (FE) modeling. The system models and results were verified by a thermomechanical coupling test of a disc brake conducted on a brake dynamometer. By using varied evaluation indexes such as the temperature distribution, the normal stress and the elastic deformation of disc surfaces, the influences of the initial DTV and its direction as well as its amplitude on the thermomechanical coupling characteristics were analyzed. The simulation results show that the distribution of temperature and the normal stress in circumferential direction exhibit the same sinusoidal function of the second order as the modeled initial DTV property, which is different from the thermomechanical coupling characteristics caused by disc surface initial run-out (LRO). Whereas the thermomechnical coupling property of the disc in circumferential direction exhibit the same sinusoidal function of the second order as that of the initial DTV, the distribution of the temperature, the normal stress and the elastic deformation in radial direction are found to be uniform. The changes in the magnitude of initial DTV are found to have insignificant effects on the changes in the overall thermomechnical coupling property. However, the circumferential gradients of the temperature, the normal stress, and the maximum disc distortion increase linearly with the increase of the magnitude of the initial DTV. The radial gradients of these quantities are not linear proportional to the magnitude of the initial DTV.
Meng, DejianWang, ZiyiZhang, LijunYu, Zhuoping
Sizing Next Generation High Performance Brake Systems with Copper Free Linings2017-01-25329/17/2017
The high performance brake systems of today are usually in a delicate balance - walking the fine line between being overpowered by some of the most potent powertrains, some of the grippiest tires, and some of the most demanding race tracks that the automotive world has ever seen - and saddling the vehicle with excess kilograms of unsprung mass with oversized brakes, forcing significant compromises in drivability with oversized tires and wheels. Brake system design for high performance vehicles has often relied on a very deep understanding of friction material performance (friction, wear, and compressibility) in race track conditions, with sufficient knowledge to enable this razor’s edge design. With significant restrictions in copper content of automotive brake linings becoming reality in California and Washington State in 2021, and a more or less complete phase-out of copper in linings occurring in 2024, one of the key ingredients of high performance linings - critical for heat transfer, high temperature tribofilms, and medium to high temperature friction - can no longer be used. This paper looks at dynamometer-based performance data from a new generation of copper-free high performance brake linings, and makes comparisons where appropriate to a current copper-containing lining. Following brake system sizing methodologies (some of which have been described in literature previously, and some of which are new and generate improved correlation to race track operation), the brake system of a case study high performance vehicle is reviewed for the impact that the copper free linings has on it. Data are generated using analysis tools, with correlation to vehicle test results. It will be shown that meeting the demands of race track usage with copper-free lining materials is possible, but that it will affect brake system design in some cases.
Antanaitis, David B.Shenberger, MichaelVotteler, Max
Effect of Temperature on Braking Efficiency Stability of Magnetorheological Fluid Auxiliary Braking Devices2017-01-25109/17/2017
Fluid auxiliary braking devices can provide braking torque through hydraulic damping, fluid auxiliary braking devices can also convert vehicular inertia energy into transmission fluid heat energy during the braking, which can effectively alleviate the work pressure of the main brake. Traditional hydraulic auxiliary braking devices use transmission fluids to transmit torque, however, there is a certain lag effect during the braking. The magnetorheological fluid (MR fluid) can also be used to transmit torque because it has the advantages of controlling braking torque linearly and responding fast to the magnetic field changed. The temperature of MR fluid will increase when the vehicle is engaged in continuous braking. MR fluid temperature changes will cause a bad influence on the efficiency stability of auxiliary braking. So it is necessary to clear about the effect of temperature on MR fluid auxiliary braking torque in order to keep the braking efficiency stability through torque compensated by other factors, such as changing the magnetic field strength. In order to analyze the effect of temperature on MR fluid auxiliary braking torque, this study established the mathematical model of the MR fluid auxiliary braking device through the theory of one dimensional flow theory of hydraulic retarders, and the properties of MR fluid are described based on the Bingham model. This paper researched the change of the properties of MR fluid under the same magnetic field condition with different temperatures, and summarized how much compensated torque is needed to keep the braking efficiency stability. Research showed that when the vehicle is engaged in continuous braking, the temperature effect on the braking torque is non-linear. The braking torque increases with the increase of temperature under the same magnetic field condition, the braking torque increases fast at high rotating speed of the rotor.
Xiong, ShengguangTan, GangfengYang, BoXiao, LongjieXu, YongbingWang, Yishi
A Comparison of Braking Behavior between an IC Engine and Pure Electric Vehicle in Los Angeles City Driving Conditions2017-01-25189/17/2017
The Los Angeles City Traffic Brake Test Schedule has been an established procedure used almost universally for generations by vehicle manufacturers to evaluate and validate braking systems for the attributes of NVH and brake wear behavior. The Los Angeles driving route, commonly known as the Los Angeles City Traffic Test (LACT), has long been considered an effective and “quasi” extreme set of real world driving conditions representative of the US passenger vehicle market and have been covered in other analysis including SAE Technical Paper 2002-01-2600 [1] The performance of a vehicle, relative to braking, in LACT conditions is typically influenced by basic vehicle and brake system attributes including the ratios of vehicle mass to brake sizing attributes, friction material selection, and the acceleration, drag, and cooling behavior of the vehicle. The general character of the LACT Route and typical driving behavior establishes an energy input to the braking system that must be managed by the chosen set of brake components overlaid to a set of vehicle attributes. Brake system sizing has generally converged on typical sizing choices based on market forces and the typicality of vehicles in their associated segment. As a result, the general sizing of brakes systems tends to revert to a mean within a segment. Tradeoffs between, noise, wear, dust and other performance attributes are made with the selection of the friction material. Where, by example, a brake designer may tradeoff the attributes of higher dust, lower lining and rotor life in LACT for higher performance in extreme fade testing to achieve a desired market differentiation. The need for the work presented is motivated by the relatively recent entry to the market of pure electric vehicles. Many of the Pure EV’s offer significant capability to employ regenerative braking, which allows the conversion of vehicle kinetic energy to electrical energy. Therefore, the potential exists to significantly affect the amount of energy input to a vehicle’s friction braking system. As the performance in a LACT is highly dependent on the energy input the brake system must manage, it is important to objectively understand how this may change with the contribution of regenerative braking. If it is determined that the energy input to the friction brake system is significantly different in pure EV’s, then the potential exists to design fundamental brake system attributes differently with the potential to realize an improved totality of associated metrics by altering many of the traditional tradeoff balances commonly constraining brake system designers. This paper will provide an analysis by comparison between an exemplar IC engine based vehicle and a pure electric vehicle during a typical “day in Los Angeles”. The paper will provide an assessment of how regenerative braking influences the energy the brake system must manage, as well as any changes to the usage profile of the brake system in these driving conditions. Finally, this paper will offer some thoughts on how this could affect future design of brake systems of pure electric vehicles
Hall, Thomas J.
Brake System Performance at Higher Mileage2017-01-25029/17/2017
The purchase of a new automobile is unquestionably a significant investment for most customers, and with this recognition, comes a correspondingly significant expectation for quality and reliability. Amongst automotive systems -when it comes to considerations of reliability - the brakes (perhaps along with the tires) occupy a rarified position of being located in a harsh environment, subjected to continuous wear throughout their use, and are critical to the safe performance of the vehicle. Maintenance of the brake system is therefore a fact of life for most drivers - something that almost everyone must do, yet given the potentially considerable expense, it is something that of great benefit to minimize. Additionally, the performance of the brake system (like the tires) can change over the useful life of the components, realized in the form of changing friction levels, fluid consumption, and drag at a brake corner level, and realized to the driver in the form of changing pedal effort, travel, response time, and fuel economy. Most studies of brake system performance, and most regulatory requirements that affect the design of the brake system, focus on the “near-new” condition. This is not accidental, the simple fact is that it is extremely difficult, expensive, and time consuming to realistically accelerate wear of brake components so that performance can be assessed in a worn condition. On a well-designed brake system, components in the hands of an average customer can last 5-10 years before wear out occurs, meaning that any practical study of wear effects must be greatly accelerated to occur within a typical vehicle development timeline. Environmental exposure involves many complex and time-dependent chemical reactions, which puts an upper limit on how much simulated field exposure can be accelerated. The present study is based primarily on evaluation of brake corner performance after vehicle-level durability test exposure. Brake corners from a diverse selection of vehicles (including two hybrid vehicle examples) were retrieved from end-of test vehicles that had received the structural equivalent of 160,000 km of test exposure, along with 10 years of simulated corrosion exposure, and then subjected to performance and residual drag tests. To supplement the findings, lab-based studies of brake hardware with simulated 50% worn use and corrosion exposure are also referenced. Brake corner performance including apparent friction level, fluid consumption, drag, torque variation, and torque hysteresis were studied and related to observations of the physical condition of the parts. The effect of the measured brake corner level performance was then accounted for at a vehicle level in the form of pedal feel, fuel economy, and lining life for representative case studies.
Antanaitis, David B.Robere, Matthew
Estimation of Brake Friction Coefficient for Blending Function of Base Braking Control2017-01-25209/17/2017
The brake architecture of hybrid and full electric vehicle includes the distinctive function of brake blending. Known approaches draw upon the maximum energy recuperation strategy and neglect the operation mode of friction brakes. Within this framework, an efficient control of the blending functions is demanded to compensate external disturbances induced by unpredictable variations of the pad disc friction coefficient. In addition, the control demand distribution between the conventional frictional brake system and the electric motors can incur failures that compromise the frictional braking performance and safety. However, deviation of friction coefficient value given in controller from actual one can induce undesirable deterioration of brake control functions. The main objective of the presented study is to propose a method to compensate disturbances induced by variations of brake linings friction coefficient through modifications of the brake torque demand for the enhancement of both brake performance and active safety. The achievement of a compensation mechanism requires the estimation of relevant vehicle states. Hereunto, a novel technique based on a linear Kalman observer is proposed for the online estimation of the brake friction coefficient by relying upon the wheel speed sensors and inertia measurement unit (IMU). Such a tool enables a more efficient use of the frictional brakes aimed at minimizing losses of friction coefficient by keeping them in the optimal operational conditions. A simulation analysis will be carried out using the commercial vehicle dynamics simulation software IPG CarMaker to test the functionality of the developed estimator in the real-time mode. Experimental results from brake dynamometric test rig will be considered in the vehicle dynamics simulation software to reproduce the real behaviour of brake linings friction coefficient. The resulting improvements in brake control functions will be analysed against longitudinal base braking cases involving blending functions also in presence of failure of the electric motors.
Ricciardi, VincenzoSavitski, DzmitryAugsburg, KlausIvanov, Valentin
Enhancing Transmission NVH Performance through Powertrain Control Integration with Active Braking System2017-01-17786/5/2017
This paper explores the potentiality of reducing noise and vibration of a vehicle transmission thanks to powertrain control integration with active braking. Due to external disturbances, coming from the driver, e.g. during tip-in / tip-out maneuvers, or from the road, e.g. crossing a speed bump or driving on a rough road, the torsional backlashes between transmission rotating components (gears, synchronizers, splines, CV joints), may lead to NVH issues known as clonk. This study initially focuses on the positive effect on transmission NVH performance of a concurrent application of a braking torque at the driving wheels and of an engine torque increase during these maneuvers; then a powertrain/brake integrated control strategy is proposed. The braking system is activated in advance with respect to the perturbation and it is deactivated immediately after to minimize losses. The powertrain control compensates for the added resistance and reestablishes the vehicle longitudinal performance according to driver’s commands. The torsional preload created in the driveline is effective in preventing/reducing vibrations and associated noise. It is worth underlining that the proposed methodology can be directly applied to existing ABS/ESC units, composed of digital solenoid valves, and does not require additional hardware components. The effectiveness of this method has been experimentally validated by means of a Hardware In the Loop (HIL) test bench which includes a Dual Clutch (DCT) transmission and a hydraulic brake system with a customized ABS/ESC unit.
Galvagno, EnricoTota, AntonioVelardocchia, MauroVigliani, Alessandro
Anti-Lock Braking System Control Design on An Integrated-Electro-Hydraulic Braking System2017-01-15783/28/2017
Two control strategies, safety preferred control and master cylinder oscillation control, were designed for anti-lock braking on a novel integrated-electro-hydraulic braking system (I-EHB) which has only four solenoid valves in its innovative hydraulic control unit (HCU) instead of eight in a traditional one. The main idea of safety preferred control is to reduce the hydraulic pressure provided by the motor in the master cylinder whenever a wheel tends to be locking even if some of the other wheels may need more braking torque. In contrast, regarding master cylinder oscillation control, a sinusoidal signal is given to the motor making the hydraulic pressure in the master cylinder oscillate in certain frequency and amplitude. Hardware-in-the-loop simulations were conducted to verify the effectiveness of the two control strategies mentioned above and to evaluate them. The simulation platform consists of the I-EHB hardware and software including CarSim and MATLAB/Simulink as well as LabVIEW serving as the communication tool. Conclusions can be reached in the light of testing results that both control strategies were able to achieve anti-lock braking under emergency situations. Compared with safety preferred control, master cylinder oscillation control performed better on the functionality of avoiding braking lock and the reduction of braking distance. Also, it is capable of working with electronic stability control systems (ESC) while safety preferred control cannot.
Liu, TianyangYu, ZhuopingXiong, LuHAN, Wei
Literature Survey of Water Injection Benefits on Boosted Spark Ignited Engines2017-01-06583/28/2017
The automotive industry has been witnessing a major shift towards downsized boosted direct injection engines due to diminishing petroleum reserves and increasingly stringent emission targets. Boosted engines operate at a high mean effective pressure (MEP), resulting in higher in-cylinder pressures and temperatures, effectively leading to increased possibility of abnormal combustion events like knock and pre-ignition. Therefore, the compression ratio and boost pressure in modern engines are restricted, which in-turn limits the engine efficiency and power. To mitigate conditions where the engine is prone to knocking, the engine control system uses spark retard and/or mixture enrichment, which decrease indicated work and increase specific fuel consumption. Several researchers have advocated water injection as an approach to replace or supplement existing knock mitigation techniques. Water, having high latent heat of vaporization, acts as a heat sink and reduces temperatures in the end gas zone, thereby reducing the tendency for auto-ignition. The added water also changes the ratio of specific heats of the charge mixture, and slightly dilutes the oxygen concentration. These changes greatly reduce the tendency to knock or detonate, in addition to reducing NOx emissions. The optimum strategy for injection to maximize benefits is still debatable, due to the fact that the latent heat of vaporization decreases as pressure increases. The ability of water to improve anti-knocking properties can potentially allow engine designs with higher compression ratio and boost pressure, and this will enable operation closer to maximum brake torque (MBT) spark timing under all operating conditions. It is worth to note that most of the research work done on water injection focuses on extending permissible engine power output. However the current trend toward boosted and downsized engines demands extending the knock limit without increasing exhaust temperatures or specific fuel consumption (which are the major limitations of existing knock mitigating techniques). This paper examines the prior research in using water injection to extend knock limit in boosted spark ignition engines, and its potential effects on performance and emissions.
Rohit, AchintSatpathy, SridevChoi, JeongyongHoard, JohnSurnilla, GopichandraHakeem, Mohannad
Conversion of Drum Brake System to Disc Brake with CAE and CFD: Resulted in Optimized Brake Rotor Design and Improved Performance2017-26-02611/10/2017
Paper explains conversion of existing drum brake system to disc brake system with complete digital validation at structural as well as thermal level to make sure First Time Right Design before physical part development. To provide leverage to quick design, modification and selection of brake system according to vehicle configuration, a virtual computational fluid dynamics (CFD) simulation process is developed and validated with test results. Temperature variation over brake drum and disc in internal standard braking cycle is measured virtually and correlated with test results. Also Fade testing criteria’s were considered during CFD analysis. This up gradation is must considering technology enhancement trend and safety in automotive segment. In current competitive market scenario and as per customer requirements, front disc brake module is becoming necessary not only for passenger segment but also for commercial segment vehicle. Brake system design is challenging task as it deals with safety norms and also required to meet stringent performance. Brake Rotor is very important component in brake system which is expected to withstand high braking torque and dissipate heat during braking event. Hence proper design and selection of braking system is very important before implementing on vehicle. Also rigorous testing process to measure the temperature rise of disc, calliper and hub of brake system is very important along with physical testing at vehicle level. Brake rotor is major part of disc brake system and First step of development is design calculation, followed up with CAD model preparation and later on CAE. All vehicle level structural loads considered during digital/CAE validation and post structural analysis, CFD analysis is completed. Detailed brake thermal loading cycle in terms of braking heat flux, meshing methodology and simulation processes revealed in paper. A transient simulation of three different types of disc profile performed. In transient thermal simulation of brake system, maximum temperature rise over disc and pads at different location are monitored and evaluated. These were compared with similar case of drum brake system. Based on conduction heat loss and convection heat loss calculation, the brake cooling effect is evaluated. Finally after confirmation from CFD analysis Brake rotor/ Brake system design frozen. All digital simulation results co-related with physical rig level and vehicle level testing, and results were acceptable. Finally weight optimized disc brake system meeting all performance criteria implemented in 8 × 2 commercial vehicle at all wheel ends. It resulted in customer delight with 20% payload increment and performance improvement from drum brake system to Disc brake system.
Anil Shah, AsheshPatidar, Ashok
The Effect of Lean Operation, Ignition Advance, and Compression Ratio on the Performance and Emissions of a Propane Fueled Electronic Fuel Injected Engine2016-32-006811/8/2016
The performance and exhaust emissions of a commercially available, propane fueled, air cooled engine with Electronic Fuel Injection (EFI) were investigated by varying relative Air to Fuel Ratio (λ), ignition timing, and Compression Ratio (CR). Varying λ and ignition timing was accomplished by modifying the EFI system using TechniCAL Industries’ engine development software. The CR was varied through using pistons with different bowl sizes. Strong relationships were recorded between λ and ignition timing and the resulting effect these parameters have on engine performance and emissions. Lean operation (λ > 1) has the potential to significantly reduce NOx production (110 g/kW-hr down to 5 g/kW-hr). Unfortunately, it also reduces engine torque by up to an order of magnitude (31 Nm down to 3 Nm). Moving ignition initiation to earlier in the compression stroke, 10o to 40o Before Top Dead Center (BTDC), improved engine performance considerably (25% improvement in brake torque) in the presence of excess air. Unfortunately, advancing the ignition also caused NOx production to increase. The effects these parameters have on engine performance are significant enough that the same engine can be used for vastly different applications with changes only to the control software. Compression ratio has a less significant effect on engine performance, but increasing CR does result in an increase engine torque. Increasing CR from 9.1:1 to 11:1 resulted in an increase in engine torque of approximately 10% for the operating parameters tested.
Lobo, Joel PrinceLee, James HowardOswald, EricLionetti, SpenserGarrick, Robert
Compositional Effects of Gasoline Fuels on Combustion, Performance and Emissions in Engine2016-01-216610/17/2016
Commercial gasoline fuels are complex mixtures of numerous hydrocarbons. Their composition differs significantly owing to several factors, source of crude oil being one of them. Because of such inconsistency in composition, there are multiple gasoline fuel compositions with similar octane ratings. It is of interest to comparatively study such fuels with similar octane ratings and different composition, and thus dissimilar physical and chemical properties. Such an investigation is required to interpret differences in combustion behavior of gasoline fuels that show similar knock characteristics in a cooperative fuel research (CFR) engine, but may behave differently in direct injection spark ignition (DISI) engines or any other engine combustion modes. Two FACE (Fuels for Advanced Combustion Engines) gasolines, FACE F and FACE G with similar Research and Motor Octane Numbers but dissimilar physical properties were studied in a DISI engine under two sets of experimental conditions; the first set involved early fuel injection to allow sufficient time for fuel-air mixing hence permitting operation similar to homogenous DISI engines, while the second set consists of advance of spark timings to attain MBT (maximum brake torque) settings. These experimental conditions are repeated across different load points to observe the effect of increasing temperature and pressure on combustion and emission parameters. The differences in various engine-out parameters are discussed and interpreted in terms of physical and thermodynamic properties of the fuels.
Ahmed, AhfazWaqas, MuhammadNaser, NimalSingh, EshanRoberts, WilliamChung, SukhoSarathy, Mani
Experimental Analysis of Combustion Noise Reduction with Performance Optimization in 110cc CVT Scooter Engine2016-01-231110/17/2016
Indian two wheeler market is one of the largest and highly competitive in the world. Indian scooter segment grows at a pace of around 30% YOY. The stiff competition among OEM’s to increase the market share with fuel efficient and high performance products pushes development and calibration engineers to burn the midnight oil to concoct innovative methods to design technology boosted product. Customer expectations are always high in terms of fuel economy, drivability and NVH. Due to higher level of complexity involved in CVT (Continuously Varying Transmission) engine, it is difficult to optimize for achieving best of NVH characteristics along with Fuel Economy, drivability and reduced exhaust emission. This paper describes the experiment conducted during the development of 110cc CVT four stroke scooter engine. The development and calibration of this scooter was mainly based on real world usage pattern (RWUP). In order to obtain best performance from engine, ignition timing, fuel metering and CVT were optimized to achieve Maximum Brake Torque. With the ignition timing which can provide maximum braking torque the performance characteristics of the engine was meeting the PALS/FI target but severe combustion noise was observed which restricted the use of MBT ignition Timing. This technical paper describes the optimization methodology of this four stroke scooter engine on which the combustion noise (Noise generated due to rapid combustion of charge) is substantially reduced within acceptable noise levels without compromise in engine performance. The experiment comprise of noise source identification, analyzing the factors which affects combustion noise and optimization of these parameters to reduce engine combustion noise. Engine combustion parameters like peak cylinder pressure, pressure rise rate, and mass fraction burned along with heat release rate were analyzed by varying ignition timing and carburetion. The Engine ignition timing being dual curve, ignition timing varies with engine speed and operating condition (namely Partially Open Throttle, POT and Wide Open Throttle, WOT). Combustion noise was observed to be higher at both POT and WOT condition. Ignition timing was optimized at specific operating zones where combustion noise was observed to be predominantly higher, the loss in engine performance due to change in ignition timing was substantiated with optimization of carburetor venturi size, air filter connecting tube effective diameter and CVT ratio. Experimental results shows significant reduction in combustion noise up to 5dB(A), without any compromise in engine performance, Fuel economy and drivability.
Prasath G, ArunDuraiarasan, SaravananGovindarajan, R
The Upper-Load Extension of a Boosted Direct Injection Poppet Valve Two-Stroke Gasoline Engine2016-01-233910/17/2016
Engine downsizing can effectively improve the fuel economy of spark ignition (SI) gasoline engines, but extreme downsizing is limited by knocking combustion and low-speed pre-ignition at higher loads. A 2-stroke SI engine can produce higher upper load compared to its naturally aspirated 4-stroke counterpart with the same displacement due to the double firing frequency at the same engine speed. To determine the potential of a downsized two-cylinder 2-stroke poppet valve SI gasoline engine with 0.7 L displacement in place of a naturally aspirated 1.6 L gasoline (NA4SG) engine, one-dimensional models for the 2-stroke gasoline engine with a single turbocharger and a two-stage supercharger-turbocharger boosting system were set up and validated by experimental results. The simulation results show that when a single-stage turbocharger with wastegate is used in the two-cylinder 2-stroke poppet valve gasoline engine, a compressor with high pressure ratio at low mass flow rate should be selected in order to maintain the positive pressure difference between intake and exhaust ports. The maximum brake torque of the turbocharged 2-stroke gasoline engine cannot reach that of the NA4SG engine at 1000 rpm and 1500 rpm. Its maximum brake power at 3000 rpm is lower than that of the NA4SG engine at 6000 rpm. However, in the case of two-stage serial boosting system with a supercharger and a downstream turbocharger, the 2-stroke poppet valve gasoline engine can produce the torque and power of the NA4SG engine.
Fu, Xue-QingHe, Bang-QuanZhao, Hua
Alkali-Activated Inorganic Based Brake Pads: Realization and Performances of Alternative Friction Materials for a Concrete Industrial Application2016-01-19139/18/2016
Organic brake pads for automotive can be defined as brake linings with bonding matrix constituted of high-temperature thermosetting resins. Bonded together inside the polymeric binder are a mix of components (e.g. abrasives, lubricants, reinforcements, fillers, modifiers…), each playing a distinctive role in determining the tribology and friction activity of the final friction material. The herein reported work presents inorganic “alkali-activated”-based materials suitable for the production of alternative brake linings (i.e. brake pads), by means of an unconventional low-temperature wet process. Exploiting the hydraulic activity of specific components when exposed to an alkaline environment, such peculiar inorganic materials are capable of coming to a complete hardening without the need of traditional high-temperature energivorous procedures. The main advantages of these materials resides in: the decreased embodied energy of the employed raw materials, the reduction of process costs, a potential drop of the emitted pollutants coming from the high-temperature degradation of organic resins. In the present work the results of our investigation in the field are illustrated, our prototype inorganic material is indeed compared to the original resin-based OE and to another traditional phenolic alternative. Brake pads were tested on a full-scale automotive brake dynamometer, following SAE J2522 (AK Master) procedure. In order to prove the excellent performance of such inorganic materials even under high-demanding conditions, brake pads were also tested by means of an internal fading procedure. The results obtained so far are promising and pave the way to further developments toward a concrete industrialization of these unconventional class of friction materials.
Sanguineti, AlessandroTosi, FedericoBonfanti, AndreaRampinelli, Flavio
Interactive Effects of Thermal Deformation and Wear on Lateral Runout and Thickness Variation of Brake Disc Rotors2016-01-19399/18/2016
Brake judder is one of the most serious problems in automotive-brake systems. It is basically a forced vibration caused by the friction-surface geometry of a brake disc, and therefore, disc rotors play a significant role in judder. There are two types of judder: cold and hot. Hot judder is caused by the thermo-mechanical deformation of a brake disc due to high-speed braking. There are several shapes of deformation, e.g., coning and circumferential waviness. Circumferential waviness is caused by thermo-mechanical buckling and typically found as a butterfly shape in a 2nd rotational-order and hot-spotting. In a previous paper, two groups of disc castings with different material homogeneity were machined intentionally to have two kinds of dimensional variations. From repetitive high-speed braking tests of these discs, both the material and dimensional homogeneity were found to affect the wave-like deformation of discs in the 1st and 2nd rotational-orders with different significance between the two casting groups. There are many mechanisms affecting disc geometry during braking. Plastic deformation and wear cause permanent effects, while thermal expansion and elastic deformation are reversible. A disc’s initial shape before braking affects its geometry both transiently and permanently. Considering these effects, the previous test results were reanalyzed in the present paper. Some discs exhibited large transient runout and DTV but small permanent DTV, while others behaved differently. The thermal deformation and differential wear were confirmed to interactively affect the transient and permanent geometry of operating brake discs.
Okamura, Toshikazu
Study on Commercial Vehicle ECR Thermal Management System2016-01-19359/18/2016
With the continuous increasing requirements of commercial vehicle weight and speed on highway transportation, conventional friction brake is difficult to meet the braking performance. To ensure the driving safety of the vehicle in the hilly region, the eddy current retarder (ECR) has been widely used due to its fast response, lower prices and convenient installation. ECR brakes the vehicle through the electromagnetic force generated by the current, and converted vehicle mechanical energy into heat through magnetic field. Air cooling structure is often used in the traditional ECR and cooling performance is limited, which causes low braking torque, thermal recession, and low reliability and so on. The water jacket has been equipped outside the eddy current region in this study, and the electric ECR is cooled through the water circulating in the circuit, which prolongs its working time. The cooling flow water also can be modulated to control the temperature of the ECR precisely, which also reduces the eddy current retarder’s heat fade. The mathematical model of TRJ1500Nm ECR electric-magnetic-heat has been established, and flow channels integrated to the retarder shell have been designed based on the heat source distribution characteristics, the effect of flow rate’s controlling capacity to the ECR wall’s temperature also has been studied. The characteristic parameters of thermal management unit has been determined combined with the system simulation. And finally the relationship among the braking torque, the flow of water medium and the electric ECR temperature has been determined. Anticipate results has been achieved that heat fade rises gradually once the working temperature over 500 degrees Celsius while lower working temperature doesn’t influence it obviously, and water cooled medium could control the upper limit of the ECR’s working temperature, improve braking torque and reduce the thermal recession in this study. This method provides a new way for the cooling of ECR, and has a certain reference value to the design of thermal management system of ECR.
Mei, BinyuGuo, XuexunTan, GangfengChen, MingHuang, BoXiao, Longjie
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