SELECTION OF POWERTRAIN TO ACHIEVE PERFORMANCE OF VEHICLE

Journal for Research | Volume 02 | Issue 09 | November 2016 ISSN: 2395-7549

Selection of c to Achieve Performance of Vehicle Pankaj Raut B.E Student Department of Mechanical engineering Institute Tata Technologies Ltd.

Abstract Selection of powertrain for vehicle is depends upon vehicle type & application of vehicle. To achieve performance of vehicle, engine torque at maximum revolutions, Transmission ratio, Axle ratio & tire plays important role. In order to understand vehicle performance in theoretical calculation there should be proper selection of power train aggregates. All these aggregates technically will evaluate the actual vehicle performances. For example, trucks are seldom run at their rated maximum speed. In fact, they are usually operated with engine speed at maximum torque or at the speed where fuel consumption is minimized. In climbing hills, there may be occasions when the engine revolution is raised to its maximum to produce the maximum horsepower; however, the most efficient method of operation is to use the range of engine speed, which maximizes torque. If an engine's speed range, producing maximum torque, is extremely narrow, a slight increase of rpm will cause a substantial loss of power and sign of poor performance characteristic. In other words, engines with high maximum torque and horsepower are not necessarily the most "powerful engine." Factors other than the maximum values of the torque and horsepower must be evaluated in determining the practical performance of engines. Furthermore, a high performance engine must be combined with the correct transmission and differential in order to produce the desired running performance. It is necessary to understand the factors affecting its ease of operations. This Paper tells how to integrate powertrain and judge performance of vehicle according to application and type of vehicle by reading performance curves and calculation. Keywords: Powertrain, Vehicle _______________________________________________________________________________________________________ I.

INTRODUCTION

Current scenario of vehicles is to produce more power and better fuel economy. For that care should be taken while power train integration that power loss should not be minimum. For example, a high speed truck for carrying goods applications within intra city. Truck need max speed 100 km/hr but at the same time it is able to carry heavy goods in hilly area or gradient area. Truck mostly runs 90% on flat road. For such application we should optimize the power train integration such that it should get top speed on flat road and max torque on tires in gradient road. To meet vehicle performance, should select an engine whose torque curve is flat with respect engine rpm (see fig 1). Also consider transmission ration, Rear axle ration tire size (table 1) and set Maximum speed of vehicle and % of grade ability. II. OBJECTIVE OF WORK Opportunity     

Optimization of power train aggregates Better fuel economy Reduction of engine power loss in gradient road Use the range of engine speed, which maximizes torque Can set Vehicle max speed Customer Impact

 

Customer satisfaction due to better fuel economy Enhanced grade ability. III. METHODOLOGY: - VEHICLE PERFORMANCE OPTIMIZATION Vehicle speed

To optimize vehicle performance 1st set vehicle application. In this paper vehicle application is cargo vehicle which has to max speed of 103 Km/h. This vehicle run mostly runs 90% on flat road. As per engine curve (Fig 1) and transmission ratio (Table1) we can calculate speed at different gear ratio. Speed at different gear ratio as per equation (Fig 2).

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Selection of c to Achieve Performance of Vehicle (J4R/ Volume 02 / Issue 09 / 002)

Fig 1

Table â&#x20AC;&#x201C; 1

Gear Reverse 1st 2nd 3rd 4th 5th

Ratio Efficiency 6.875 0.903 6.875 0.913 4.189 0.913 4.189 0.913 1.542 0.913 1 0.931

Rear Axle ratio: 5.571 Tire Size: 10R22.5 (static radius 0.492 meter) Engine Max RPM: 3100 Vehicle max speed is at top gear (i,e: transmission ration 1 at 5th gear) Vmax = 2Ď&#x20AC;R X N X 60 Yt X Ya = 2 X 3.14 X 0.492 X 3100 5.571 X 1 = 103.2 Km/h Where: R is radius of driving tire in meters N is maximum RPM of engine Yt is gear ratio Ya is rear axle ratio This will be Maximum speed for vehicle on flat road with this max engine rpm corresponding transmission ratio and axle ratio. Correspondingly Vehicle speed at five speed transmission (Fig 2)

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Selection of c to Achieve Performance of Vehicle (J4R/ Volume 02 / Issue 09 / 002)

Fig. 2: Running resistance Running resistance includes rolling resistance, grade resistance and Air resistance.

Rolling resistance is a resistance feel by tires of vehicle due to ground surface in contact. Rr = µ X W X Cosθ Where: W is the weight of the truck (G.V.W.) transmitted to the ground through the tires θ is the grade of the road over which the truck is traveling µ is coefficient of resistance. Grade resistance is the resistance to vehicle due to gradient of road. Rg = W X Sinθ Air resistance is a resistance due to dynamic drag of vehicle in running. Ra = λAV2 Where: A is projected front area of truck (m2) V is speed of truck in motion (km/h) λ is coefficient of resistance. Total Resistance = Rr + Rg + Ra Vehicle weight: 14030 kg Projected area: 5.07 m2 Coefficient of resistance (dynamic drag) : 0.0035 Contact surface resistance: 0.01 From the above value resistance at variable speed of vehicle with specified % gradient (Fig 3)

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Selection of c to Achieve Performance of Vehicle (J4R/ Volume 02 / Issue 09 / 002)

Fig 3

Tractive Effort Tractive effort is how much torque is transfer from engine to vehicle tire.

F = T X 0.95 X Yt X Ya X ษณ R

Where: T is engine torque (kg-m) R is tire size (m) ฮท is mechanical efficiency of power train Yt is transmission gear ratio Ya is rear axle ratio Tractive effort at variable vehicle speed at different transmission speed with specified % gradient (Fig 4) All rights reserved by www.journalforresearch.org

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Selection of c to Achieve Performance of Vehicle (J4R/ Volume 02 / Issue 09 / 002)

Fig. 4:

IV. ANALYZE PHASE By analyzing Fig 2, Fig 3 & Fig 4 comes to know how the vehicle perform with all the factor considering for powertrain integration (Fig 5) Vehicle performance curves can give you lot of information The Maximum speed is defined as the fastest speed attainable by fully loaded truck (GVW Basis) on a flat road (0% grade) A vertical limit A drawn from the maximum value at the end of the vehicle speed curve for fifth gear shows the maximum speed of the vehicle. In this case, the maximum speed is approximately 115Km. From this see that the engine speeds at this time is about 3600 rpm. Maximum Hill climbing ability (Gradeability) The intersection between the running resistance curve B and the tractive efforts maximum value (found in the first gear curve) show the maximum grade ability. In this case the maximum climbable grade is about 34%

Fig. 5: Vehicle Performance Curve

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Selection of c to Achieve Performance of Vehicle (J4R/ Volume 02 / Issue 09 / 002)

Moreover, the Fig 5 shows that when running at 80 Km/h (vertical Line), the maximum climbable grade is 2% in fifth gear, and 3% in fourth gear. From the intersection of the vehicle speed curve and line C the engine rpm is 2400 rpm in fifth gear and 3400 rpm in fourth gear The graph also tells that vehicle cannot climb a 5 % grade in fifth gear. The fourth gear tractive effort curve shows that, while climb it can climb grade in fourth gear the speed must be dropped to 40Km/h Surplus Tractive Effort The surplus tractive effort is the difference between the tractive effort curves for each transmission gear and the running resistance (Note that running conditions). This surplus tractive effort is available for acceleration and condition. Let’s determine the surplus tractive effort when the vehicle is driving at 50Km/h on a 0% grade in fifth gear. The value at the intersection of vertical line from 50 Km/h E and the fifth gear tractive effort curve 280kg. The value at the intersection of line E and the 0% running resistance curve 90Kg. The difference between these two values, 280Kg - 90kg = 190 kg is the surplus tractive effort in fourth gear is 350 kg (440kg - 90kg) V. CONCLUSION This Paper tells how to integrate powertrain and optimize performance of vehicle, according to selection of powertrain sub components with help of power train calculations using MS excel and reading performance curves of vehicle. According to application of Vehicle and type of vehicle, power train selection will depend. This paper helps to perform soft calculation in initial phase of vehicle project to select power train component for set customer targets. This paper suggest that each powertrain component is having same importance as that of power generating source (engine) to achieve performance of vehicle with minimum fuel consumption to Happy customer. REFERENCES [1] [2]

Automotive Engineering Powertrain, Chassis System and Vehicle Body “David A. Corolla”: 2009 Vehicle Powertrain Systems: Integration and Optimization “Crolla, David; Mashadi, Behrooz”: 2012

ABBREVIATIONS Vmax Rr Rg Ra

Vehicle Max Speed Rolling Resistance Grade Resistance Air drag Resistance

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SELECTION OF POWERTRAIN TO ACHIEVE PERFORMANCE OF VEHICLE

Published on Feb 24, 2017

Journal 4 Research

Selection of powertrain for vehicle is depends upon vehicle type & application of vehicle. To achieve performance of vehicle, engine torque at maximum revolutions, Transmission ratio, Axle ratio & tire plays important role. In order to understand vehicle performance in theoretical calculation there should be proper selection of power train aggregates. All these aggregates technically will evaluate the actual vehicle performances. For example, trucks are seldom run at their rated maximum speed. In fact, they are usually operated with engine speed at maximum torque or at the speed where fuel consumption is minimized. In climbing hills, there may be occasions when the engine revolution is raised to its maximum to produce the maximum horsepower; however, the most efficient method of operation is to use the range of engine speed, which maximizes torque.