Week-4 Challenge WOT Condition Part-2

FIRST-

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

Powertrain Block set provides two types of combustion engine models-

• mapped
• dynamic

MAPPED ENGINE-

• Mapped engines represent macro engine behaviour as a set of lookup tables (brake torque, fuel flow, air mass flow, exhaust temperature, efficiency, and emissions) as functions of commanded load and measured engine speed
• Mapped engine models are suitable for analysis and design activities that do not require engine subsystem dynamic characteristics, for example, in engine and transmission powertrain matching analysis for fuel economy, emissions, and performance trade-offs.

DYNAMIC ENGINE-

• Dynamic engines decompose engine behaviour into individual component models that account for engine dynamics, most notably intake airflow and turbocharger dynamics.
• Dynamic engine models are suitable for designing control, estimator, and diagnostic algorithms that depend on dynamic subsystem states, for example, in closed-loop AFR (Air-Fuel Ratio) control algorithm development.

We can switch between mapped and dynamic engines by following the below procedures-

• Open the EV model in Simulink.
• Enter the passenger car block by double-clicking it.
• Then go to the Electric plant block.
• Inside the motor, block right-clicks to find the variant option.

SECOND-

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

Miles per Gallon (MPG) & 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 via miles-per-gallon equivalent (MPGe).MPG is the number of miles your car can drive per gallon of gas. Figuring out an MPGe rating is a little more complicated. Since engines that use an alternative source of fuel can’t be measured by liquid gallons of fuel, the MPGe rating is calculated by figuring out the number of miles a vehicle can go using the same energy content as a gallon of gas. The EPA calculates that 33.7 kilowatt-hours of electricity are equivalent to one gallon of gas.

In the case of our EV model, inside the visualization block, we have another block named Performance Calculations.

If we get inside this block we find the actual (MPG) calculations

Here The three different inputs are taken into consideration-

• Vehicle Speed
• Fuel flow
• Battery power

The vehicle speed input is in m/s which is converted into miles by multiplying by 0.000621371.

Similarly, the kilogram of fuel is converted into cubic meters by multiplying by 1/(1000*0.739).

This cubic meter value is then converted into gallons by multiplying it by 264.172. The mile value and gallon value are used to find the MPG of the vehicle.

Now the battery value is initially converted from watts to kWh by dividing by 1000 and then to gallon equivalent by again dividing it by 33.7 (since 33.7 kWh = 1 gallon).

Then divide the value by 3600 to get in per second and multiply by 0.00378541 to get the value in cubic meters per gallon.