Week-4 Challenge WOT Condition Part-2
Q 1:
What is the difference between mapped and dynamic model of engine, motor and generator? How can you change model type?
Ans:
Powertrain block set provides two types of combustion engine models : 1)Mapped & 2)Dynamic
Mapped model uses a set of steady state 2D look up table to characterize engine/motor performance.The tables provide overall engine characteristics including engine torque,fuel flow rate,BSFC and engine out exhaust emissions.This model leads to faster solving times.
Dynamic model decomposes engine behaviour into engine/motor characteristics that are seperated into lower level components. By combining components this way the models capture the dynamic effects.
They are used if you need a more detail dynamic model and have component level data and also to analyze the individual engine components on the overall performance .
Mapped Diagram:
Dynamic Diagram:
To change between mapped and dynamic model:
Open the powertrain module blockset for the required vehicle.
Click on passenger car/vehicle book and select electric plant/engine.
Right click on engine/Ev/generator based on vehicle model and select variant.
Under variant scroll to label model active choice and choose mapped or dynamic for the required calculation.
Q2 :How does the model calculate miles per gallon? Which factors are considered to model fuel flow?
Ans :
Miles Per Gallon(MPG) and Miles Per gallon equivalent(MPGe) :
For a conventional gasoline vehicle , the fuel efficiency is calculated via miles-per-gallon(MPG). However fuel efficiency for hybrid models is calculated by miles-per-gallon equivalent(MPGe). MPG is the number of miles your car can drive per gallon of gas. Figurin out an MPGe rating is a little more complicated.Since engines that use an alternative source of fuel cant be measured by liquidgallons of fuel, the MPGe rating is calculated by figuring out the number of miles a vehicle can go using the same energy contentas gallon of gas.The EPA calculates that 33.7 Kwhours of electricity is the equivalent to one gallon of gas.
In case of our EV model , inside the visualization block we have another block named Performance calculations.
If we get inside this block we get the actual calculations.
Here three inputs are taken into consideration:
1) Vehicle speed
2) Fuel Flow
3) Battery Power
The vehicle speed is in m/s which is converted into miles by multipying by 0.000621371
Similarly the kilogram of fuel is converted into cubic meter by multiplying by 1/(1000x0.739)
This cubic meter value is then convereted into gallonms by multiplying with 264.172.The mile value value and Gallon value is used to find the MPG of the vehicle.
Now the battery value isinitially converted from watts to kwh by dividing with 1000 and then to gallon equivalent by again dividing it with 33.7( 1 gallon = 33.7kwh)
Then divide value by 3600 to get in per seconds and multiply by 0.00378541 to get the value in cubic meter per gallons.
Q3: Run the HEV ReferenceApplication with WOT drive cycle. Change the grade and wind velocity in the environment block. Comment on the results.
Ans :
Model :
We have changed the drive cycle to WOT with a sample time = 40 s
We have also Altered the Environment block and changed the wind speed to 25m/s & grade =10
The simulation was run for a time period of 40s
Input Parameters:
Environment Blockset:
RESULTS:
Conclusions:
Plot 1: trace Velocity,Target,Actual :
Top velocity achieved = 50.1mph
Time taken to accelerate = 29.034s
time taken to decelerate = 3.226s
Plot 2 : Motor & ENgine RPM :
Total Motor RPM = 12550 rpm
Top Engine RPM = 6188 rpm
Plot 3 : Motor & Engine Torque :
Maximum motor Torque = 50Nm
Maximum Engine torque = 205.3Nm
Plot 4 : Battery ncurrent :
The Battery supply current is at its maximum value pf 167Ampere when full throttle is applied by the end user. It reduces drastically to the value of negative 150 during decelaration of the vehicle.
Plot 5: Battery SOC :
The battery SOC falls from 60% to 40% during the acceleretion period of the vehicle and it increases slightly to 43 % during decelaration due to regenerative braking .
Plot 6 : Fuel Economy :
Maximum Fuel economy achieved is 6.056
Q4: Keeping all other parameters same, compare the simulated results of hybrid and pure electric powertrains.
Simulated Results of HEV:
Simulated results of pure EV:
Conclusion :
1. The top speed achieved by hybrid vehicle is more than that of pure EV.
2. The battery current capacity of pure EV is much higher compared to that of HEV since in EV battery is the only driving unit.
3. Higher fuel economy is achieved in case of pure EV.