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Heat Shield Insulation for Thermal Challenges in Automotive Exhaust System

Sharda Motor Industries, Ltd.-Sivanandi Rajadurai, Ananth S
  • Technical Paper
  • 2019-28-2539
Published 2019-11-21 by SAE International in United States
While advanced automotive system assemblies contribute greater value to automobile safety, reliability, emission/noise performance and comfort, they are also generating higher temperatures that can reduce the functionality and reliability of the system over time. Thermal management and proper insulation are extremely important and highly demanding for the functioning of BSVI and RDE vehicles. Frugal engineering is mandatory to develop heat shield in the exhaust system with minimum heat loss. Heat shield design parameters such as insulation material type, insulation material composition, insulation thickness, insulation density, air gap thickness and outer layer material are studied for their influences on skin temperature using mathematical calculation, CFD simulation and measurement. Simulation results are comparable to that of the test results within 10% deviation. The performance index is calculated using the temperature gradient between the pipe surface and the external skin temperature. The performance index increases with material insulation thickness and insulation material density. Increase in insulation thickness from 6 mm to 19 mm reduces the skin temperature from 44% to 77%. The specialty insulation material provides a high…
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Criticality of Tube Bending Through CAE Understanding

Sharda Motor Industries, Ltd.-Sivanandi Rajadurai, Guru Prasad Mani
Published 2016-04-05 by SAE International in United States
Tube bends are critical in an exhaust system. The acceptability of tube bends is based on the induced level of shape imperfections considered. An analysis is presented for the performance tuning of the genetic algorithm including the importance of raw material selection, ovality and elongation property. This study is an attempt to analyze the ovality effect of STAC 60/60 material. CAE tools are essential to exploit the design of experiments and find out the optimum values of the design parameters in comparison with full factorial designs.Especially the effects of materials, dimensions and geometry shape of the ultimate strength were discussed by both CAE and experiments. The ultimate strength of steel tube was evaluated at least 20-30% as a local strain independent of the materials. The dependency of ultimate bending angle on original centre angle of the tube bend was clarified.The finite element method is used to model and analyze a stand-alone, long-radius tube bend with 50.8 mm nominal diameter and a 100 mm bend radius with specified length. The computed results are compared and the…
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Effective Methodology for Backpressure Prediction of Hot Exhaust Gas in Cold Flow Bench Test

Sharda Motor Industries, Ltd.-Sivanandi Rajadurai, Madhusudhanan Paulraj, Alrin Maria Victor
Published 2016-04-05 by SAE International in United States
The numerical methodology is developed to estimate the backpressure value acquired from the cold flow bench into the hot flow conditions by equalizing various gas flow properties such as gas density and gas constant. The exhaust muffler geometry is adopted for virtual analysis. Computational Fluid Dynamics (CFD) modeling of the exhaust muffler in hot and cold flow conditions shows 60% of difference in back pressure values. The same muffler sample is tested in hot and cold flow test bench for back pressure on same measurement location used in CFD tool, the test result difference between these two conditions is obtained as 61%. By using derived 1D calculation, the cold flow back pressure results are extrapolated to generate hot flow back pressure values for the exhaust muffler system. These extrapolated values are then validated with the back pressure analysis results performed in both CFD and flow test bench using cold and hot flow conditions. The difference of back pressure gap between the cold and hot flow results are reduced to 5% and 4% respectively. The paper…
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Computational Simulation to Validate Resonator through Bending Moment

Sharda Motor Industries Ltd. - R&D-Sivanandi Rajadurai, Guru Prasad Mani, Kavin Raja, Sundaravadivelu Mohan
Published 2015-06-15 by SAE International in United States
Bending moment is one of the strongest pursuits in resonator's structural validation. Eigen problems play a key role in the stability and forced vibration analysis of structures. This paper explains the methodology to determine the weak points in the resonator assembly considering the additional effects of the installation forces and temperature impacts. Using strain energy plots, weakest part of the product is identified in the initial stage.The solution comes in unique way of utilizing the worst case scenarios possible. As a consequence, the stress generated by these analyses will prove to be critical in concerning the durability issue of the system.These conditions are evaluated by a finite element model through linear approaches and results are summarized.
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Influence of Linear and Parabolic Elements in Structural Rigidity of Converter Mounting Brackets

Sharda Motor Industries, Ltd.-Sivanandi Rajadurai, Guru Prasad Mani, Kavin Raja, Sundaravadivelu Mohan
Published 2015-04-14 by SAE International in United States
Generation of discretization with prescribed element sizes are adapted to the geometry. From the rules of thumb, for a complicated geometry it is important to select the reasonable element order, shapes and size for accurate results. In order to that, this paper describes the influence of elemental algorithm of the catalytic converter mounting brackets. Brackets are main source of mounting of various systems mainly intake and exhaust in the engine. In hot end exhaust system, a bracket design plays a vital role because it has to withstand heavy structural vibrations without isolation combined with thermal loads.Bracket design and stiffness determines the whole catalytic converter system's rigidity. So, here discretization of converter brackets by linear and parabolic elements is studied with different elements types and compared. The study shows disparity in the structural accuracies of the brackets in each of elemental orders respect to the element shapes i.e. in the stiffness and resonance frequencies. For an optimized proposal it is significant to predict the accurate resonances along with desired stiffness target in less time consumption. To…
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Computational Simulation to Ascertain Hot Vibration Test Assembly for Converter Validation

Sharda Motor Industries Ltd., R&D-Sivanandi Rajadurai, Guru Prasad Mani, Kavin Raja, Sundaravadivelu Mohan, Balaji Manivannan
Published 2015-01-14 by SAE International in United States
Automotive exhaust system components are exposed to many types of vibrations, from simple sinusoidal to maximum random excitations. Computer-Aided engineering (CAE) plays an inevitable role in design and validation of hot vibration shaker assembly.Key Life Test (KLT), an accelerated hot vibration durability test, is established to demonstrate the robustness of a catalytic converter. The conditions are chosen such a way that the parts which passes key life test will always pass in the field, whereas the parts which fail in the key life test need not necessarily fail in the field. The hot end system and the test assembly should survive in these aggressive targeted conditions. The test fixture should be much more robust than the components that it should not fail even if the components fail.This paper reveals the computational methodology adopted to address the design, development and validation of the test assembly. The breakdown issue of the system due to oxidation, creep, plasticity, and mechanical load factors are discussed. Thermal expansion aggregated over the mechanical loading for different configurations helps in detecting the…
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Partial Controlled Canning for Thin Wall and Ultra Thin Wall Substrates - A New Approach

Sharda Motor Industries Ltd-R&D-Sivanandi Rajadurai, Prakash Krishnan, Naveen Sridharan, Manimaran Sethuramasubramaniyam
Published 2014-09-30 by SAE International in United States
The trend lately has shifted towards usage of thin wall and ultra-thin wall substrates. This change has come to existence due to the increased acting surface area available in these substrates. However these types of substrates have reduced isostatic strength comparatively, reducing its canning durability. This phenomenon has induced a new canning methodology which shall not disturb the substrate integrity during canning and also perform effectively to the requirements. This can be achieved by controlled canning which includes a huge investment and so a new methodology has been devised using the available resources and a partial controlled canning process is established and verified for canning performance and found to be effective. The paper shall include the procedural explanation and a set of results obtained by the new methodology to support its effectiveness.
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Influence of Coupled Analysis for a Hot End Exhaust System Validation

ACS Industries Inc-Sivanandi Rajadurai
Sharda Motor Industries Ltd, R&D-Guru Prasad Mani, Sundaravadivelu Mohan, Kavin Raja
Published 2014-09-30 by SAE International in United States
Simulation's drive towards reality boundary conditions is the toughest challenge. Experience has shown that often the most significant source of error in thermal and dynamic analyses is associated within specified boundary conditions. Typically, validating the system by considering both thermal and dynamic loads with predefined assumptions is time consuming and inconclusive when confronted with reality boundary conditions.Thus, the solution comes in unique way of combining thermal and dynamic loads with specified boundary conditions and will convey computational results closer to the real scenario. As a consequence, strain concentrated regions due to thermal expansion are aggregated more, when coupled with dynamic loading. The stress generated by the coupled analyses will prove to be critical in concerning the durability issue of the hot end system.These conditions are evaluated by a finite element model through linear and non-linear approaches and results summarized.
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Durability Improvisation of Exhaust System Resonator Internal

Sharda Motor Industries Ltd.-Sivanandi Rajadurai, N. Suresh, P. A. Sairaman, S. Ananth
Published 2013-01-09 by The Automotive Research Association of India in India
A combined Computer Aided Engineering (CAE) simulation and physical fatigue testing of a passenger car exhaust system resonator with wire mesh seal between the inlet and outlet pipe is performed to evaluate the durability and improvise the design. The outlet pipe end cap of the exhaust system resonator deformed and cracked at the fillet region repeatedly upon the application of the maximum load from a pre developed accelerated specification test. However, the system meets the end usage on-road durability target of 5 years / 1,00,000 km. There is a gap between the accelerated bench test and the end usage durability target. The current study correlates CAE simulation and biaxial fatigue testing and improvise possible alternate resonator design. Conventionally, components passing the accelerated test always meets the end usage durability target whereas components meeting the end usage durability target need not necessarily pass the accelerated test. Developing accelerated test procedure from Road Load Data Acquisation (RLDA) on an application specific vehicle is the way to bridge the gap between end usage durability target and accelerated test.
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Improved NOx Reduction Using Wiremesh Thermolysis Mixer in Urea SCR System

ACS Industries Inc.-Sivanandi Rajadurai
Published 2008-10-07 by SAE International in United States
A compact, knitted, crimped wiremesh mixer disposed in the exhaust system of an internal combustion engine, between the reductant injection and the urea SCR unit, increases the uniformity of the reductant in the exhaust stream by the time the stream reaches the SCR catalysis unit. Wiremesh mixer enhances thermolysis of urea into ammonia and iso-cyanic acid (HNCO). Computational Fluid Dynamics (CFD) modeling shows improved uniformity index from 0.94 to 0.99 within 35 mm travel length due to longitudinal and radial flow of the exhaust gas through the body of the wiremesh mixer. The higher thermolysis and rapid warm-up nature of the wiremesh provides enhanced ammonia production from urea thermolysis. Wiremesh physical attributes such as material composition, geometry and structure, wire diameter, mesh crimp pitch, crimp depth, crimp angle and the contour are optimized for minimum back pressure and maximum mixing efficiency. The modified geometry and channel dimensions of the wiremesh provide zigzag path for the gas flow to obtain efficient mixing. NOx reduction performance was improved in steady state engine tests. About 10-30 % improvement…
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