Week-4 Challenge WOT Condition Part-2

1.What is the difference between mapped and dynamic model of engine, motor and generator? How can you change model type?

The powertrain blockset provides two types of propulsion models
1. Mapped Model uses a set of steady-state 2-d lookup tables to characterize engine/motor performance. The tables provide overall engine characteristics,including actual torque, fuel flow rate, BSFC, and engine-out exhaust emissions. This model leads to faster solving times.
2. Dynamic Model decomposes the engine behavior into engine/motor characteristics that are separated into lower-level components. By combining components in this way, the models capture the dynamic effects. They are used
*If you need a more detailed dynamic model and have component-level data.
*To analyze the impact of individual engine components on the overall performance.
To change between mapped & dynamic model:
*Open the powertrain module blockset for the required vehicle.
*Click on passenger car/vehicle block and select electric plant or engine.
*Right click on Engine/EV motor/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

2.How does the model calculate miles per gallon? Which factors are considered to model fuel flow?

Miles per gallon (MPG) is a fuel economy rating determined by how far a car can travel on a gallon of gasoline or diesel for a conventional IC Engine vehicle. In the case of an electric vehicle, this is a measure how much electrical energy is consumed by the battery pack to travel a fixed distance.

The powertrain block has an inbuilt model for this which can be found inside the visualization block.

The above image has two fuels electricity and fuel. As discussed earlier 1 gallon of gas equal to 33.7 kwh of electricity.
So battery power is first converted into KW (W/1000) then its divides by 33.7 kwh. The fuel equivalent of battery is added to the fuel flow. Using the vehicle speed and time the distance of travel is calculated. Then distance is converted into miles by conversions. Then as we have the fuel flow in m^3 and distance in miles. We can calculate the fuel efficiency.

3.Run the HEV ReferenceApplication with WOT drive cycle. Change the grade and wind velocity in the environment block. Comment on the results.

Use the command 'autoblkHevStart ' in the command window to open the HEV reference application. Then double click Drive cycle source block and then change the drive cycle to 'WOT' as shown in the below image. Also configure the parameters like time duration, WOT start time, initial speed, final speed, max speed and time to start deceleration.

HEV Reference Application Blockset

WOT Drivecycle inputs
Total simulation time = 100s
Nominal Speed = 50m/s
Deceleration time = 50s
Default grade (0 degrees) and wind velocity (0 m/s

Observations:
A visible difference is observed between the actual trace velocity curve and input trace velocity curve due to the limitation of power available from the
energy source.
The maximum speed achieved is lower in case 2 because of the gradient slope considered and also the wind resistance.
Since more power from the energy source is required to overcome these resistances, the battery SOC and the fuel economy is decreased.

4. Keeping all other parameters same, compare the simulated results of hybrid and pure electric powertrains

EV Powertrain configuration

EV reference application blockset

After comparing the graphs of both EV and HEV following conclusions can be drawn:
1. The first graph (target and actual velocity graph) performance is almost same. the reason could be that in that region only motor was operating so the
performance in both EV and HEV is similar.
2. The battery current drawn by HEV initially is upto 500 A and later decreases to 200 A. This can be attributed to the fact that initially only motor takes all the
load and later engine kicks in so motor load drops thus current drawn by motor reduces. And during the deceleration it is seen that negative current
(regenerative braking) flows for a longer time in HEV as compared to EV. So we can say that, regenerative braking is more aggressive in HEV.
3. SOC improvement of almost 15% is seen in HEV during deceleration and only 2% improvement can be seen in EV during deceleration. This can be
understood by the same reason explained in point 2.
4. Motor torque and motor speed are stable in EV and they keep fluctuating a lot in HEV during the starting. Also the peak RPM of the motor in EV is less than
HEV. These differences can attributed to the fact that battery power of EV is more than HEV.
5. Fuel economy of EV is significantly greater than HEV. This is because electric motor is more efficient than engine.