Week-4 Challenge WOT Condition Part-2

- 1.Aim:

- Understanding the difference between the mapped and dynamic model of engine, motor and generator.

- To find out how does the model calculate miles per gallon? Which factors are considered to model fuel flow.

- Run the HEV ReferenceApplication with WOT drive cycle. Change the grade and wind velocity in the environment block.

- Compare the simulated results of hybrid and pure electric powertrains. 

- 2.Objectives:

- Doing changes in the default system like grade, initial velocity and also change the cycle.

- Comparing the objectives of HEV and EV model.

- To find how the model calculates miles per gallon.

- 3.Method:

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

- Mapped:

- CI mapped- Model uses a set of steady-state lookup tables to characterize engine performance.

- SI mapped- The tables provide overall engine characteristics, like torque, fuel flow rate, BSFC.

- Use:

-If you have engine data from a dynamometer or a design tool like GT-POWER.

-For quasi-steady-state engine simulations.

- Dynamic: 

- CI Engine: Model decomposes the engine behaviour into engine characteristics that are separated into lower-level components. By combining components in this way, the models capture the dynamic effects.

- Use:

-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.

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

- The block is shown above is used to represent the miles per gallon of the vehicle i.e the amount of fuel consumed by the vehicle. However, though this is an HEV and the amount of battery consumed is need to be taken into amount. But as the battery provides the current, directly it can not be taken into consideration.

- The blocks shown below are nothing but converting the battery used while running the vehicle into equivalent fuel quantity. As the vehicle engine is running on certain fuel, it is necessary to convert this battery use into equivalent quantity.

- After integrating the velocity, we get distance which is needed to be converted into proper units. Like what is there converting meter to miles. For converting the units gain blocks are used. Saturation block is used to give upper and lower limits for distance. 

- A product blocks are provided in order to get the final output as per requirement. For example, after converting the fuel unit and distance into miles and gallon, a product block is provided which consist of '*' & '/' which will convert the two separate quantities into miles/gallon. 

- Factors considered for the fuel flow are velocity, fuel used and battery. Here the fuel like gasoline and battery both has to be considered while calculating the fuel economy. However, the battery can not be directly considered, so a conversation is needed which is shown above. Also in order to obtain the distance covered by the vehicle, it is necessary to find the displacement. 

- In order to get the displacement it is necessary to do integration the velocity. After this, it is necessary to convert the units and it is done by the gain blocks. 

3.3. Run the HEV Reference Application with WOT drive cycle. Change the grade and wind velocity in the environment block.

- The first two images are showing the input and output. And the third image is showing the output as per the default settings. It is clear that the acceleration time and top speed in both cases are different and it depends upon the initial conditions. The comparison is shown below.

- As compared to the default setting it is in which the battery is getting charged a number of time from 80 to 70%, it is not in this case of WOT. In this, the battery when starts dropping it drops to a particular value and then stops there.

- Also as it is a WOT, it means the throttle is opened from its zero position to its maximum position. This results in changing the velocity suddenly in less time interval, remaining constant for some time and again reducing to zero as there is no further increase.

- In the WOT, the current it provided during the sudden acceleration and after the cycle, it reaches to 0, whereas in the default cycle the current passes as per the requirement throughout the cycle. 

- Same behaviour can be seen in Engine speed, Engine torque, where there is change only during the sudden acceleration.

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

- Putting the same input parameters as the HEV like WOT, a grade of 7, the velocity of 10. As both, the models are working on the same cycle and parameters the difference can be observed.

- From the  1st plot it can be seen that the thought both the vehicles are having the same input cycle and parameters like grade and velocity, still, the maximum acceleration the EV can achieve is more than HEV. Not only the acceleration, but the battery conditions are totally different. 

- In EV the current remains same for most of the cycle then at the end there is some fluctuation, whereas for HEV it there is continuous fluctuation in the current as the cycle goes.  

- In case of the EV the SOC does not go below 75 whereas in the HEV it goes to 70. There is small regeneration in the EV when battery SOC goes below 77.5.

- In HEV as the WOT condition the parameters are continuously varying the current which is dynamic current. This does not happen in the case of EV.

- 4. Learning outcome: 

- Comparing the outcomes of HEV & EV after changing the default parameters.

- Understanding how to find fuel consumption in miles/gallon.

- Comparing the WTO with and without the change in the parameters.