Plot the level load curve and determine the engine power

Reference no: EM13960298

1. Object

(a) To determine the power needed to give the chosen vehicle the required performance; to determine the bottom and intermediate gear ratios.

(b) To arrive at a suitable engine specification for the vehicle in order to give the required performance.

2. Data

(a) Use the data for the vehicle chosen from the following table:

Mass C_DA r_tyre V_max

___ ____ ____ _____

Kg m² m km/h

1. Sports car 1150 0.65 0.28 234

2. Large saloon 1600 0.69 0.33 216

3. Small hatch 950 0.61 0.27 144

4. Panel van 3500 1.50 0.36 126

The mass values given above for an unladen vehicle, expect for the panel van (for which the gross mass is given). An appropriate payload allowance must therefore be made.

(b) For all the vehicles, the following rolling resistance coefficient values may be used, though alternative values may be substituted if though appropriate.

(c) Transmission efficiency: make the appropriate assumptions. One method of estimating transmission efficiency is to assume 97% per meshing pair.

For all the vehicles assume that the gearbox has 5 forward speeds; that the 4th gear is "correctly" matched so that the maximum power speed of the engine corresponds to the maximum possible vehicle speed, and that 5th gear is 25% "overdrive".

For all the vehicles there is a requirement to be able to climb a 36% gradient at the maximum torque speed in the lowest gear.

3. Method

Note that the transmission matching required in this assignment may be determined by plotting either the tractive power or road load power against vehicle speed, or plotting tractive force and road load against vehicle speed.

(a) Select one of the four vehicles given above. The same calculations are required for all the vehicles: only the values of the parameters differ.

(b) Plot the level load curve and determine the engine power required to give the stated vehicle maximum speed.

• engine type: spark ignition or Diesel;
• a suitable type of combustion chamber and appropriate mean effective pressure at torque peak for the chosen engine type;
• suitable maximum port velocity based in inner valve seat diameter (d);
• suitable valve sizes and hence determine the mean piston speed; check that this is appropriate for the engine duty;
• a suitable value of torque "back-up" in order to determine the mean effective pressure at the power peak.

(d) For the required maximum power determine the required total piston area using:

Power = ¼ Pe A Vp

where: Pe = mean effective pressure at maximum engine speed, as chosen above;
Vp = mean piston speed (at maximum engine speed);
A = total piston area;
& note that the ¼ is replaced by ½ for a 2-stroke engine.

For the required duty choose the number of cylinders and hence the bore size. Determine the stroke to give a suitable engine speed, and hence determine the swept volume.
Is the swept volume appropriate for the class of vehicle and engine type?

Note that an interactive process may be needed to obtain the best compromise between the number of cylinders; the stroke/bore ratio; an acceptable maximum engine speed. The bore and stroke values may also be rounded at this stage, or slightly adjusted to bring the swept volume below a target value (e.g. a tax threshold of 2.0 litres).

(e) Choose an appropriate engine speed at which peak torque will be developed; convert the chosen mean effective pressure values at peak power and peak torque into torque values at the flywheel. Use these values to sketch an appropriate torque curve (on graph paper). Read off torque values from the graph for speeds between peak torque and peak power.

(f) Determine the overall gear ratios for 4th and 5th gears (25% difference).

Convert the engine torque curve to a tractive effort curve, or a tractive power curve in 5th gear, plotting this on the road load curve. (Remember transmission efficiency, which may differ in 4th and 5th). Hence determine the maximum speed of the vehicle in 5th gear.

(g) Determine the first gear ratio by plotting either the road load power or torque to climb the required gradient. Determine 2nd and 3rd gear ratios assuming a geometric progression.

References

H. Bauer (ed.): Bosch automotive handbook, WileyBlackwell; 7th edition, 2007.
W-H. Hucho: Aerodinamics of road vehicles, Society of Automotive Engineers (SAE); 4th Revised edition edition, 1998.

Reference no: EM13960298

Questions Cloud

Risk-return and the capital asset pricing model : This week we focus our attention to Risk, Return, and the Capital Asset Pricing Model (CAPM). One of the primary concepts in the field of finance is the risk-reward trade off. An assumption of risk-reward is the tenet of risk aversion for investor..

How many boxes should the inventory analyst order : Assume that weekly demand for boxes of Legos at Wal-Mart is normally distributed with a mean of 2,500 boxes and a standard deviation of 500 boxes. The replenishment lead time is two weeks and the inventory is reviewed and an order is placed every 4 w..

Was the jury unduly prejudiced against wal-mart : Do you think that Wal-Mart willfully did not disclose the evidence of the grease spill? Did the jury consider Wal-Mart's conduct when it reached its verdict? Was the jury unduly prejudiced against Wal-Mart?

What might have been one or two ethical issues : You may recall hearing about a past legal case in which a woman sued McDonalds because of burns she received when hot coffee spilled in her lap. At the time, she was riding in her nephew’s sports car and they purchased the coffee at McDonalds’ drive-..

Plot the level load curve and determine the engine power : Determine the overall gear ratios for 4th and 5th gears - Choose an appropriate engine speed at which peak torque will be developed; convert the chosen mean effective pressure values at peak power and peak torque into torque values at the flywheel.

What is the probability that the ball may be brown is : Box A contains three balls with colors red, green and blue and box B contains a balls with colors red, yellow ,blue, white and brown A box is chosen and a ball is picked. What is the probability that the ball may be brown is? What is the probability ..

Limited-life intangible assets : As of 12-31-13, G owned several limited-life intangible assets. During 2014, G purchased an unlimited-life intangible asset for $60,000.

Code of ethics for corporate financial managers : 1. Do you believe maximizing shareholders' wealth is consistent with ethical behavior? 2. What do you think is important in a code of ethics for corporate financial managers? What considerations should a company make when adopting a code of ethics..

Calculate the magnitude of the friction force : A car travels at a speed of 24 m/s around a curve of radius 57 m. The acceleration of gravity is 9.8 m/s^2 . What is the net centripetal force needed to keep the car from skidding sideways?

User Account

All Pages