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Gear Shift Pattern Optimization for Best Fuel Economy, Performance and Emissions

Chidhanand S.
Mahindra & Mahindra, Ltd.-Lemuel Paulraj, Saravanan Muthiah
  • Technical Paper
  • 2020-01-1280
To be published on 2020-04-14 by SAE International in United States
As the FTP-75 drive cycle does not have a prescribed gear shift pattern, automotive OEMs have the flexibility to design. Conventionally, gear shift pattern was formulated based on trial and error method, typically with 10 to 12 iterations on chassis dynamometer. It was a time consuming (i.e. ~ 3 to 4 months) and expensive process. This approach led to declaring poor fuel economy (FE). A simulation procedure was required to generate a gear shift pattern that gives optimal trade-off amongst conflicting objectives (FE, performance and emissions). As a result, a simulation tool was developed in MATLAB to generate an optimum gear shift pattern. Three different SUV/UV models were used as test vehicles in this study. Chassis dyno testing was conducted, and data was collected using the base and optimized gear shift patterns. Dyno test results with optimized gear shift pattern showed FE improvement of ~ 4 to 5% while retaining the NOx margin well above engineering targets. This labeling FE improvement method did not require any hardware or software changes, thus, involved no additional expense.…
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A Holistic Approach to Develop a Modern High Power Density Diesel Engine to Meet Best-in-class NVH levels.

Mahindra & Mahindra, Ltd.-Vikraman Vellandi, Prasad Namani, Rajkumar Bhagate, Madhu Chalumuru
  • Technical Paper
  • 2020-01-0406
To be published on 2020-04-14 by SAE International in United States
The ever-increasing customer expectations put a lot of pressure on car manufacturers to constantly reduce the noise, vibration and harshness (NVH) levels. This papers presents the holistic approach used to achieve best-in-class NVH levels in a modern high-power density 1.5 lit 4 cylinder diesel engine. The base engine architecture was designed with NVH reduction features such as crank-offset, cast iron crankcase, stiffened ladder frame, structural oil pan and front cover. Piston skirt profile was optimized to reduce the slapping noise by carefully studying the secondary motion and skirt contact pressure. The plastic parts such as cylinder head cover and intake manifold were designed with closely spaced ribs and high wall thickness. Natural frequency targets for different parts were set for the entire engine at component level and system level and confirmed through simulations. High frequency acoustic simulation was carried out to identify and improve the areas of high surface velocity. "Acoustic holography" technology was extensively used to identify the areas of high noise radiation in the running engine. Based on the measurements, it was identified…
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Robust and optimum design selection for crank train dampers

Mahindra & Mahindra, Ltd.-Anup Bhattacharya, Vivek Yadav, Abhijit Londhe
  • Technical Paper
  • 2020-01-0603
To be published on 2020-04-14 by SAE International in United States
Reduced engine noise and vibrations is a key challenge in product development which leads to better comfort for end customer. Cranktrain is a major contributor in the transfer path of gas oscillations. The noise and vibrations induced by cranktrain torsional resonances are reduced by providing torsional dampers. Dampers are also important for avoiding resonant failures. The requirements from dampers is high reliability, lesser sensitivity for manufacturing variability in rubber properties with respect to desired performance. The requirement from a cranktrain damper is to achieve minimum crankshaft vibratory torque. Also, damper heat dissipation and torsional oscillations need to be within acceptable limits. This depends on selection of damper dimensions, damper hub inertia, ring inertia and rubber stiffness. There is a non-linear dependence of these parameters on damper performance. Hence, it needs an optimizer with better design space exploration capabilities. This paper presents, reliability based optimization process starting with generation of RSM followed by NSGA-II evolutionary search algorithm to achieve robust optimum damper design in early phase of product development through simulation. The process reduced number of…
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A component level laboratory test methodology development for validating transmission bush

Mahindra & Mahindra, Ltd.-Devanshu Kathrecha, Abhirup Chakraborty, Avinash Sirur, Jobin Sebastian, Jinesh Savla
  • Technical Paper
  • 2020-01-1409
To be published on 2020-04-14 by SAE International in United States
In the era of fierce competition, launching a defect free product on time would be the key to success. In modern automobile, the transmission system is designed with utmost care in order to transfer the maximum power from engine to driveline smoothly and efficiently. Optimized design of all the transmission components is necessary in order to meet the power requirement with the least possible weight. Transmission bush failure was observed in one of the transmissions during complete system level testing. Bushes are generally press fitted on the main shaft and counter shaft on which the needle roller bearing is mounted. In some cases, the free axial movement of the gear is restricted by the hub or shaft itself. But in other cases, due to assembly constraints, the bush itself is flanged to restrict the axial free play of the gear. When the respective gear is not in engaged condition, the bush does not get any axial thrust. Once the gear is engaged, due to the axial thrust caused by the helical gear, the bush experiences…
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Using Vehicle Specifications to Gain Insights into Different Automotive Market Requirements

Mahindra & Mahindra, Ltd.-Lemuel Paulraj, Saravanan Muthiah
  • Technical Paper
  • 2020-01-1283
To be published on 2020-04-14 by SAE International in United States
Determination of vehicle specifications (for example, powertrain sizing) is one of the fundamental steps in any new vehicle development process. The vehicle system engineer needs to select an optimum combination of vehicle, engine and transmission characteristics based on the product requirements received from Product Planning (PP) and Marketing teams during concept phase of any vehicle program. This process is generally iterative and requires subject matter expertise. For example, accurate powertrain sizing is essential to meet the required fuel economy (FE), performance and emission targets for different vehicle configurations. This paper analyzes existing vehicle specifications (Passenger Cars/SUVs - Gasoline/Diesel) in different automotive markets (India, Europe, US, Japan) and aims to determine underlying trends across them. Scatter band analysis is carried out for specifications such as vehicle kerb weight (WT), vehicle length (L), vehicle width (W), vehicle height (H), footprint area (FPA), engine cubic capacity (CC) and engine power (P). CC/WT vs FE, CC/FPA vs FE, P/WT vs FE, FPA/(LXW), CC/(FPAXH), FPAXH and WXH trends are analyzed amongst others. It is interesting to note that similarities exist…
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Calibration and parametric investigations on Lean NOx Trap and Particulate Filter models for a light-duty diesel engine

Mahindra & Mahindra, Ltd.-S. Suresh Bagavathy
IIT Madras-A Ramesh, Anand Krishnasamy
  • Technical Paper
  • 2020-01-0657
To be published on 2020-04-14 by SAE International in United States
To comply with the stringent future emission mandates of light duty diesel engines, it is essential to deploy a suitable combination of emission control devices like diesel oxidation catalyst (DOC), diesel particulate filter (DPF) and DeNOx converter (LNT or SCR). Arriving at an optimum size and layout of these emission control devices for a particular engine through experiments is both time and cost intensive. Thus, it becomes important to develop suitable well-tuned simulation models that can be helpful to optimize individual emission control devices as well as arrive at an optimal layout for achieving higher conversion efficiency at minimal cost. Towards this objective, the present work intends to develop a one dimensional Exhaust After Treatment Devices (EATD) model using a commercial code. The model parameters are fine-tuned based on experimental data. The EATD model is then validated with experiments data that are not used for tuning the model. Subsequently, the model was used for studying the effects of geometrical parameters of the after-treatment devices like diameter and length on the conversion efficiency and the pressure…
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A unique approach to optimize the gear-shift map of a compact SUV to improve fuel economy and performance

Mahindra & Mahindra, Ltd.-Sangeetha RT, Vignesh Shankar, Anshuman Bose, Bharatraj Jayaraman
  • Technical Paper
  • 2020-01-0969
To be published on 2020-04-14 by SAE International in United States
Automated manual transmission (AMT) is often preferred by the car manufacturers as an entry-level automation technology. The AMT technology can provide the comfort of an automatic gearbox at a reasonable cost impact over the manual transmission (MT). This paper explains the unique approach to define the gear-shift map of a compact sports utility vehicle (SUV) considering the unique requirements of the Indian market. The real-world measurements revealed that an aggressive shift pattern with delayed upshift and quick downshift can deliver a good low-end drivability and performance while compromising on fuel economy. Moreover, the chassis dyno measurements in the modified Indian drive cycle (MIDC) indicated lower fuel economy values. On the other hand, a shift pattern with early upshifts and delayed downshifts could help in achieving a better fuel economy while compromising on drivability and performance. Hence, a unique approach is used to derive the most optimal gear shift map for each operating gear. Gear-shift points of actual vehicle were measured in real-world operating conditions in a reference vehicle under different operating conditions (traffic, user, road)…
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EGR flow control strategy for a smaller capacity diesel engine using a phase shifting chamber

Mahindra & Mahindra, Ltd.-Karthikeyan N. Krishnan, Padmavathi Ramadandi, Vinodini Bhargava, Karthik Chandana
  • Technical Paper
  • 2020-01-1358
To be published on 2020-04-14 by SAE International in United States
Exhaust gas recirculation (EGR) is an effective strategy to control NOx emissions in diesel engines. EGR reduces NOx through lowering the oxygen concentration in the combustion chamber, as well as through heat absorption. The stringent emission norms have forced diesel engines to further improve thermal efficiency and reduce nitrogen oxides (NOx). Throttle control is adopted in diesel intake system to control the EGR & fresh charge flow and to meet the emissions norms. In three or lesser cylinder. diesel engines, predominantly single and two-cylinder diesel engines, there is a higher possibility of the exhaust gas reaching the intake throttle and Particulate matter getting deposited on the throttle body. This can significantly affect the idling stability and intake restriction in prolonged usage. In idling condition, the clogged throttle body stagnates the fresh charge from entering the cylinder. The work aims at the study of flow pattern for EGR reaching the throttle body. A numerical study is conducted on a two-cylinder smaller displacement diesel engine. In a two-cylinder engine with an EGR circuit the intake valve of…
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Design and Development of Ultra-Low Friction High-Power Density Diesel Engine for the Indian Market

Mahindra & Mahindra, Ltd.-Vikraman Vellandi, Prasad Namani, Suresh Bagavathy, Madhu Kishore Chalumuru
  • Technical Paper
  • 2020-01-0834
To be published on 2020-04-14 by SAE International in United States
Diesel engines are known for their excellent low-end torque, drivability, performance and fuel economy. The ever-increasing customer demands push the diesel engines continuously to deliver higher torque and power. However, the requirement of higher power and torque puts a great challenge on the mechanical friction which can greatly influence the vehicle level fuel economy in a negative way. This paper explains the methodology to design a high power-density diesel engine capable of 180 bar peak firing pressure yet achieving the lowest level of mechanical friction. The base engine architecture consists of 8mm crank-offset which is an optimized value to have the lowest piston side forces. The honing specification is changed from a standard plateau honing to an improved helical slide honing with optimized Rz, Rpk and Rvk values. The cumulative tangential force of the piston rings are reduced to an extreme value of 24 N. A rectangular special coated top ring and a low-friction architecture oil ring is used to reduce the friction without increasing the blow-by and oil consumption. A special low-friction coating is…
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Spot Weld Fatigue Correlation Improvement in Automotive Structures using Stress based Approach with Contact Modelling

Mahindra & Mahindra, Ltd.-Srikesh Kadakuntla, Durga Prasad Mohapatra, Suhas Kangde
  • Technical Paper
  • 2020-01-0182
To be published on 2020-04-14 by SAE International in United States
In automotive Body-In-White (BIW) structures, stiffness and the fatigue behavior are greatly influenced by the properties of its joints. Spot welding is one of the most widely used process for joining of sheet metals in BIW. Spot weld fatigue life under Accelerated Durability Test (ADT) is crucial for durability performance of BIW structures. Current experience of BIW validations highlighted significant number of spot weld failures in CAE when compared to actual tests. Hence, lot of iterations in the form of design modifications are required to be carried out to make these CAE failure spots pass which leads to increased design & development time and cost. Current practice uses force-based approach for predicting spot weld fatigue life in CAE under accelerated durability test. In order to improve the spot weld fatigue life correlation, extensive study has been carried out on the approaches for calculating spot weld life, namely force & stress-based approaches. This study highlights the limitations of force-based approach and addresses the advantages of stress-based approach. Standard double cup (DC) spot weld specimen has been…