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Technical Paper

Brake squeal noise reduction in city buses

2019-06-05
2019-01-1572
Buses have become one of the most widely used mode of public transportation, particularly for city applications. Indeed, passenger comfort and vehicle noise are a major concern faced by automotive industry. Brake system is one such contributor to undesired vibrations and obnoxious noise. Squeal noise, caused due to friction-induced vibrations, is a serious customer irritant to the bus passengers as well as the environment, also leading to brake performance deterioration and monetary abominations in terms of warranty costs. Brake squeal noise has been considerably studied for over years. Several design modifications and structural changes have been incorporated to prevent the occurrence of squeal noise, but the issue persists. In this paper, we have discussed on brake squeal noise reduction in city buses by optimisation brake drum diameter, selection of different friction liner linings and optimising other brake components sizes. Keywords: Squeal, brakes, drum, vibration, bus, comfort
Technical Paper

Analytical Estimation of Clutch Life for Manual Transmission

2019-04-02
2019-01-0335
The clutch is the connecting link between engine and the power train. It connects and disconnects the engine to the gearbox as per the wish of the driver. Clutch has a friction disc which acts like a fuse wire which wears in the process of the connection. This paper tries to calculate the clutch life analytically (In terms of Kms. run by vehicle), of automotive vehicles having manual transmission. As the clutch engages and disengages the engine to the gearbox, during this time due to slippage, energy is dissipated which results in the wear of the clutch disc. It calculates life based on the volumetric wear of the clutch disc and wear allowance available. The work done by other people in this domain include the empirical estimation of clutch life based on the past data, effect of the surface topography on the friction characteristics of the wet clutches, modeling of clutch housing and facing temperature for the estimation of the clutch life of a manual transmission etc.
Technical Paper

Investigation and Resolution of Gear Slippage Issue in Manual North-South Transmission

2019-04-02
2019-01-1299
Gearbox and driveline durability is always been a sensitive subject from both end user and manufacturer’s point of view. Since powertrain is heart of vehicle, naturally it is expected to long last and perform satisfactorily for the entire vehicle life. Sometimes the driveline aggregates especially gearbox might face some issues because of various factors, but this is distinctively noted by the driver since it is one of the important touch point of the vehicle. The gear slippage is a very typical phenomenon observed in automotive gearbox. The issue of gear slippage is very sensitive because it leads to compromising safety of the driver, also it deteriorates gear shift quality and thereby performance of the vehicle. Generally gear slippage is not observed during end of line testing or during early kilometers of vehicle. It is observed after some thousand kilometers, that to initially gear slippage is not observed consistently and that’s why it is difficult to identify at early stage.
Technical Paper

Transmission Breather Evaluation

2019-01-09
2019-26-0339
Breather assembly is mounted on transmission to maintain the pressure equilibrium inside transmission. Breather allows the transmission to breathe air when the air inside transmission expands or contracts due to heating and cooling of lubricating oil during vehicle running. Breather allows the hot air to escape and cool air to enter into the transmission to prevent overheating issue. Failure of breather assembly can lead to pressure buildup inside transmission and further leading to leakage from transmission oil seals. Oil leakage through the breather assembly is governed by parameters such as opening pressure, location and orientation of breather etc. The transmission undergoes different operating conditions of input speed, load, temperature, inclination etc. Also, breather assembly is designed and positioned in such a way that there is no leakage through breather due to oil splash inside the transmission.
Technical Paper

Refurbished and Repower: Second Life of Batteries from Electric Vehicles for Stationary Application

2019-01-09
2019-26-0156
Rising environmental concerns and depleting natural resources have resulted in faster adoption of green technologies. These technologies are pushed by the government of states through certain schemes and policies as to make the orbit shift ensuring greener environment in near future. Major actions can be easily seen in transportation sector. Hybrid Electric Vehicle (EV), EV and Fuel cell EV are being deployed on roads rapidly but even though some challenges are still unsolved such as battery cost, fast charging and life cycle of the automotive battery. Automotive batteries (Lithium ions) are declared as unfit for automotive usage after the loss of 20% to 15% of their initial capacity. Still 80% to 85% of battery capacity can be utilized in stationary applications other than automotive. Stationary application doesn’t demand high current density or energy density from the battery pack as of automotive requirements.
Technical Paper

An Analytical Approach to Derive Free Package Space Requirement for Pedestrian Head Form

2019-01-09
2019-26-0013
Pedestrians are a vulnerable road user group, comprising 22% of global road traffic deaths [1]. In Japan, pedestrian fatalities accounted for 28% of total road fatalities and approximately 16% in Australia. These figures compare with 13% for the USA and 40-50% for India and Thailand [2]. Various pedestrian safety requirements are mandated in different markets in recent years worldwide. For pedestrian head-form, vehicle front-end styling and the free package space below bonnet plays a vital role in deciding the pedestrian head-form safety performance. Currently during initial phase of vehicle development, the free package space requirement is decided based on benchmark data. However, the benchmarking data does not give any insight into the physics involved and is subjective in nature as it varies from vehicle to vehicle. This paper gives an analytical approach for defining the free package space requirements for meeting the targeted pedestrian head form performance requirements.
Technical Paper

DFSS to Design Engine Cooling System of Small Gasoline Vehicle with Rear Engine

2019-01-09
2019-26-0037
In automobile design, a rear-engine layout mainly espoused for small entry-level cars and light commercial vehicles for three reasons - packaging, traction, and ease of manufacturing. The aim of this paper is to strategize cooling system of rear-mounted engine of a small gasoline car. Radiator and cooling fan packaged close to engine at rear of the car for simple packaging. Efficient thermal management ensured by robust overheat protection stratagem using EMS software. DFSS, a disciplined problem prevention approach that helps in achieving the most optimum design solution and provides improved and cost effective quality products; is used to finalize an optimum design based on the analysis of the various tests carried out as per DOE [1]. This paper is about designing a distinctive cooling system of a car having rear-mounted engine with rear radiator but front mounted HVAC system [2].
Technical Paper

Evaluation of the Tire Wear Possibility due to Non-Steerable Twin Tire Lift Axle on Heavy Commercial Vehicle

2019-01-09
2019-26-0066
The commercial vehicle market in India is shifting to higher payload capacity vehicles due to a lower transportation cost per unit goods. To cater this requirement, the vehicle manufacturers are designing the heavy multi-axle commercial vehicles and with higher per axle loading capacity. One of such a vehicle design involves five-axle vehicle with non-steerable, twin tire, lift axle. Though using a twin tires have increased loading capacity of lift axle compared to a single tire self-steerable lift axle, it can cause tire scrub while vehicle is turning and leads to a significant tire wear. The tire wear possibility due to use of non-steerable lift axle is estimated through simulation using full vehicle model in ADAMS. The operating zone of the vehicle, where maximum tire wear can occur, is identified through simulation. Different alternatives to reduce tire wear for this scenario are also discussed.
Technical Paper

Air Intake System Optimization for Passenger Car Engine

2019-01-09
2019-26-0044
The customer expectations in the passenger car market are predominantly in the areas of engine/vehicle performance along with NVH refinement. In addition, continuously evolving regulatory emission and crash norms with system cost considerations bring out multiple challenges on to design engineers. One of the vehicle systems that has its footprints on all of the above requirements is the engine air intake system. In this paper, using multidisciplinary approach we discuss the impact of air intake system design of a 3-cylinder gasoline engine on different attributes of customer requirements. The primary function of the air intake system is to provide filtered air to the engine. However, this paper explains how requirements like engine performance, NVH refinement, regulatory and styling, durability, servicing and system cost are affected by intake system design parameters.
Technical Paper

Prediction of Seat Rail and Steering Wheel Vibration at Idle Using Crank Drive and 16-DOF ADAMS Model

2019-01-09
2019-26-0181
Due to the recent trend in auto industry to opt for higher power engines, causes increase in vibrations levels in the passenger’s compartment. This requires a better and comprehensive model to analyze vibrations from engine to seat and steering wheel much before the proto stage of development in the design stage itself. For this purpose, modelling is done in ADAMS multi dynamics and assuming the 16 degrees of freedom of the vehicle. Further, a crank drive model is developed to simulate engine excitation forces comprising unbalanced inertia forces and torque fluctuations and their effects seat rail and steering wheel vibration is derived. This tool is an attempt to predict such vibrations caused and assist in design enhancement and streamline the procedure.
Technical Paper

Chemical Kinetics Modelling of Exhaust After-Treatment System: A One Dimensional Simulation Approach

2019-01-09
2019-26-0249
The Indian automotive industry has taken a big leap towards stringent Bharat Stage VI (BS VI) emission standards by year 2020. A digital driven design and development focusing on innovative and commercially viable technologies for combustion and exhaust after-treatment system is the need of the time. One-dimensional (1D) simulation serves as a best alternative to its counterparts in terms of obtaining faster and accurate results, which makes it an ideal tool for carrying out optimization studies at system level. In this work, 1D chemical kinetics modelling and analysis of exhaust after-treatment system (EAT) for a heavy-duty diesel has been performed using GT-Power. Initially, a single site 1D model for a diesel oxidation catalyst (DOC) has been developed and then, a two-site, 1D model for a selective catalytic reduction (SCR) catalyst was also developed based on reactor data.
Technical Paper

Multi Body Dynamics Based Method for Twist Beam Cross Articulations Evaluation in Realistic Hilly Area Scenarios

2019-01-09
2019-26-0251
Twist beam is a semi-independent suspension having two trailing arms attached to the chassis via rubber bushes. Closed profile ‘V’ shaped cross beam interconnects left and right side arms. It provides roll stiffness of the suspension, by twisting as the two wheels moves relative to each other. Due to driving and road conditions twist beam structures are subjected to cyclic twist loads resulting into roll fatigue failure mode [1]. To design twist beam for mass, package and performance it is required to find realistic cross articulations based on vehicle application, usage pattern and protect twist beam from roll fatigue failure mode. The objective of this paper is to develop a virtual method using ‘ADAMS ®’ multibody dynamics software for maximum relative wheel center displacements during realistic hilly areas conditions. This paper describes half and full vehicle based virtual approach for twist beam cross articulations in hilly area conditions.
Technical Paper

Methodology for Exhaust System Design Optimization for Light Weight Passenger Vehicles

2019-01-09
2019-26-0269
While designing the exhaust system of passenger car on one hand there is stringent emission regulations, packaging constraints, high NVH performance requirement. On the other hand with lightweight vehicle design there is tremendous pressure on weight reduction of exhaust system while keep the same NVH performance levels. Exhaust system consist of muffler, bellows, pipes and hangers. For muffler design both acoustic (transmission loss, pass-by noise, tail pipe noise etc.) and non-acoustic (backpressure) parameters needs to be considered. In the current paper, methodology for muffler design optimization using 1D acoustic simulation software is presented. The baseline exhaust design consist of two mufflers; main muffler and post muffler. Simulation methodology is developed to optimize main muffler design in order to eliminate post muffler requirement while achieving the same performance of baseline exhaust design.
Technical Paper

HVAC System Noise Prediction through CFD Simulation

2019-01-09
2019-26-0210
Vehicles with Heating, Ventilation and Air Conditioning (HVAC) system have shown growing demand for in-cabin acoustic comfort in recent days. This is mainly due to advancement in new generation quieter powertrains and improved cabin sealing which has made HVAC system noise more dominant inside the cabin. HVAC system noise is predominantly flow induced. Further, considering future hybrid and Electric vehicles where engine powertrain noise will be insignificant, more attention will be required for HVAC system design. Contribution of noise in the cabin from HVAC system is in the frequency range 400 Hz to 5000 Hz. The noise produced by a HVAC system is mainly due to aeroacoustics mechanisms related to the flow fluctuations due to the blower rotation and complex flow path in HVAC unit flaps, duct and vents. Air borne noise is becoming important as other noise sources reduced with advancement of material, insulation and architectural strategies.
Technical Paper

Full Vehicle NVH CAE Methodology Development to Address Tailgate Rattling on a Future Tata SUV

2019-01-09
2019-26-0213
In recent years, car manufacturers have been working intensively on new ways to improve the quality of interior trims. Elimination of squeak and rattle has become one of the main concerns for car manufacturers lately, given the significance of these incidences in customers' perception of overall quality. Traditionally, rattle problems are found and fixed with physical tests at the late design stage, mainly due to lack of up-front CAE simulation prediction methodology and tools availability. This article presents a finite element based methodology for the improvement of rattle performance of a vehicle tailgate. In this study, appropriate finite element (FE) modeling technique was introduced to accurately predict occurrence of tailgate rattle. Simulation process using commercial software “Nastran” employing modal and forced frequency response analyses was illustrated. Design modifications were incorporated for performance improvement of rattling on present and future SUVs.
Technical Paper

Diagnosis and Elimination of Vehicle Lateral Shake in Passenger Car through Modification of Driveshaft Joints and Engine Mount System

2019-01-09
2019-26-0214
Vehicle lateral shake during take-off is sensitively felt by customers when the vehicle is driven at a low speed under drive away acceleration. The take-off shudder is complained by customers during 1st and 2nd gear take off. Under an engine torque and half shaft angle, the drive-away shudder usually occurs during acceleration to a specific low speed at 1200 to 1600 engine rpm, which makes the vehicle shake severely. A thorough investigation with possible design optimization of mounting system, drive shaft joint and lubrication is done to reduce the lateral vibration. This paper focuses on a passenger car, the take-off shudder of which occurs at a speed between 20 km/h and 30 km/h. The test vehicle is a monocoque construction with front wheel drive east west engine. Vehicle lateral shake is observed during the low gear power train run up in Wide Open Throttle (WOT) condition.
Technical Paper

Study of Clutch Judder Phenomenon in Manual Transmission Vehicle and Its Analysis Approach

2019-01-09
2019-26-0215
Clutch engagement judder is a phenomenon wherein the driver experiences vibrations on seat during the clutch engagement process for the vehicle launch. Clutch engagement judder is one of the critical vehicle attributes as a part of overall vehicle NHV. Torsional oscillations, specifically originating from clutch in the driveline during clutch engagement, are referred as clutch engagement judder. Judder is a phenomenon wherein friction induced torsional vibrations are generated in the driveline because of sliding contact between clutch and flywheel, during engagement. These resulting oscillations inherit the first resonance frequency of the driveline. The engagement judder not only affects the dynamics of transmission system but also the vehicle, because of excitations being transferred to body via suspensions and mounts. Passengers experience these oscillations as vibrations during vehicle launch. If excitation level is high then it may cause discomfort to passengers.
Technical Paper

External Aerodynamic Drag Coefficient Prediction of Full Scale Passenger Car Based on Scale Model Assessment

2019-01-09
2019-26-0224
Aerodynamics performance evaluation of passenger cars is important during early vehicle development phase as it influences fuel economy, vehicle stability and drivability. Usually during initial styling phase, scale model is prepared and tested in wind tunnel to check aerodynamic performance like drag coefficient and these are used to predict aerodynamic performance of full scale model as testing on full scale model is costly and time consuming. To ensure its correctness, it is important to understand difference in physics from scale model to full scale model. In predicting full vehicle aerodynamics performance from scale model assessment; importance of Reynolds number, effect of geometric scaling on flow i.e. flow separation and wake zone change needs to be understood and addressed. This paper discusses about effect of scaling on aerodynamic flow behavior and drag.
Technical Paper

Development and Prediction of Vehicle Drag Coefficient Using OpenFoam CFD Tool

2019-01-09
2019-26-0235
Vehicle aerodynamic design has a critical impact on fuel efficiency of the vehicle. Reducing aerodynamic wind resistance of the vehicle's exterior shape and reducing losses associated with requirements for engine compartment cooling through vehicle front openings plays key role in achieving desired aerodynamic efficiency. Today fairly large number of computational fluid dynamics (CFD) simulations are being performed during the vehicle aerodynamic design and development process and it is rapidly increasing day by day. Vehicle aerodynamic design and development process involves mainly aerodynamic shape development, aerodynamic optimizations of vehicle external components (side view mirror, spoilers, underbody shield etc.) and number of” what if studies during preliminary design process. Licensing costs of the available commercial CFD simulation solver has significant impact on product development cost when numbers of aerodynamic simulations expand.
Technical Paper

CAE Based Head Form Impact Simulations for Development of Vehicle Interiors

2019-01-09
2019-26-0237
The interior components of a passenger vehicle are designed to provide comfort and safety to its occupants. In the event of accident, vehicle interiors are primary source of injuries when occupants interact with them. Vehicle interiors consists of Instrument panel (IP), center console, seats and controls in front of seating position etc. Severity of the injuries depends on the energy dissipating characteristics, profiles, projections of different interior components. These are assessed by ECE R21 and IS12553 head form impact tests. To evaluate the Head form impact performance on Interior components, Computer Aided Engineering (CAE) simulations are extensively used during the vehicle development. In order to predict failure of plastic components and snap joints which might lead to expose sharp edges, it is critical to model plastic material and snap joint.
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