Week-4 Challenge WOT Condition Part-2

Objective -

To understand the difference between mapped and dynamic model using HEV referencr application.

To learn which factors effect the fuel efficiency in HEV referencr application.

To model Pure electric vehicle for a Wide open throttle cycle with and without grade and wind resistance.

Compare the simulated results for a hybrid and a pure electirc vehicle by keeping all the other parameters same.

Solution - What is a powertrian blockset.

Powertrain Blockset provides fully assembled reference application models of automotive powertrains, including gasoline, diesel, hybrid, and electric systems. It includes a component library for simulating engine subsystems, transmission assemblies, traction motors, battery packs, and controller models. You can use it for design tradeoff analysis and component sizing, control parameter optimization, and hardware-in-the-loop testing.

• Drive cycle
• Drivetrain
• Energy storage
• propulsion
• transmission
• vehicle dynamics

To understand Mapped and Dynamic Model.

Power train blockset provides two types of models for engine battery motor and generator.

Mapped engine represent the macro engine behaviour as a steady state look up table when subjected to different parameters changes such as fuel flow, exhaust temperature, efficiency etc as a function of commanded load and measured engine speed. It uses this lookup table to characterise engine performance.

here we see the mapped engine model

Dynamic model of the engine refers to behaviour of engine under dynamic conditions and working performance of engine.

Dynamic model decomposes the motor behaviour into individual component models that accounts for motor dynamics. By combining the components we can capture the dynamic effect of motor.

here we see the dynamic motor model

In mapped models the data is take from a look up table which characterises the engine/motor/generator performance under certain parameters while in dynamic model it combines the result of different componenets to get the dynamic effect.

To change mapped to dynamic model first we need to go into passanger car >> electric plant>> motor and then to mapped motor Right clicking on it

Factors Affecting Fuel Efficiency

Model for EV

If we consider a pure electric vehicle then the miles per gallon or fuel economy depends on the vehicle speed and the battery power.

Model for HEV

As this model shows if we consider a hybrid electric vehicle as the engine is also running thus the factors affecting the fuel economy are vehicle speed battery power and fuel flow to the engine.

Simulation of Wide open Throttle with and without grade and wind speed

Wide Open Throttle - Wide open throttle (WOT) refers to an internal combustion engine's maximum intake of air and fuel that occurs when the throttle plates inside the carburetor or throttle body are "wide open", providing the least resistance to the incoming air.

here we see a schematic diagram for a Pure electric vehcile. It consists of a battery motor gear box, axle and wheels.

In the image below we see the Reference application model for a Pure EV. It is a backward model as the drive cycle is the input and the motor power is the out put.

By change the drive cycle to WOT cycle and keeping other parameters as it is we run the first simulation. In this we insert 50 m/s as nominal speed thus giving a step wave of 0-50m/s for first 70 seconds. The total time for the cycle is 150 seconds

In Passenger car block we see a electric plant and drive trian

in the Controller block we see regenerativ brake control and motor torque.

Case 1 - By change the drive cycle to WOT cycle and keeping other parameters as it is we run the simulation. Without any grade angle or wind resistance

Case 2 - With grade angle or wind resistance

changing the grade angle to 7 deg and wind speed to 5 m/s we run the simulation

• Comparing results we can say that without grade and wind resistance the model is able to achive 50m/s or 111.8 mph in approximately 50 seconds. While with grade and wind resistance the model is not able to achieve the target speed and has a max speed of 60 mph or 26m/s.
• For the fuel economy in case 1 we see that without resistance the economy is higher upto 40 mile/gallon and due to regenerative braking it jumps to 45 miles/ gallon. But the fuel economy is just 20mil/g and increases to 23mil/g in case 2.
• In both the cases we see that the current does not go higher then 210 amps.
• In case 2 the motor speed or RPM is also less as compared to case 1. And finally the SOC(state of charge) reduces to less then 74% in case 2 as compared to case 1.

Simulation of FTP75 Drive cycle for both Hybrid electric and pure electirc vehicle keeping other parameters same.

Pure Electric vehicle

Hybrid Electric vehicle

As shown in schematic for Hybrid electric vehicle the engine and the electric motor are in parallel to each other.

The reference model uses a mapped SI engine it also consists of a generator and electric motor connected to gear box. We can switch between mapped to dynamic engine model depending on the results we desire.

Mapped Engine

Drive trian

we run the simulation with FTP 75 Drive cycle which runs for a total of 2474 seconds in both the cases. Not changing any other parameters we run the simulation.

EV results

For the EV results we see

1. Velocity Vs time Plot - It shows the drive cycle of 2474 seconds
2. SOC Vs time plot - It show that as the distance travelled increases the SOC decreases
3. Motor speed VS time plot - This shows that as the velocity of vehicle increases the motor speed also increases.
4. Battery current vs time plot - we can say that battery current is directly proportional to motor torqur and thus if the motor torque increases the motor draws more current.
5. BSFC vs Time plot - We see that the fuel consumed by vehicle at the start of cycle is more.

HEV results

comparing the results we see

• Velocity Vs time Plot - It shows the drive cycle of 2474 seconds
• SOC Vs time plot - It show that the battery has a range of 70 to 80% charge during the drive cycle. as the distance travelled increases the SOC decreases and goes to 70% then the engine starts and the motor rotates in opposite direction in turn charging the battery. And when the battery reaches 80% charge the engine shuts down and motor gives the required torque output.
• Motor speed VS time plot - This shows that as the velocity of vehicle increases the engine and motor speed also increases. The yellow line is engine speed the blue line is motor speed and the red line is the generator speed. As the acceleration increases or due to hill climbing the power required increases and thus the rpm also increases for all three.
• Battery current vs time plot - we can say that at the start of the cycle only the motor is running so the current drawn is high as soon as the motor stops and the engine stars current value changes to negative till the time the battery charges. When battery discharges current values are positive.
• BSFC vs Time plot - We see that the fuel consumed by vehicle at the start of cycle is less as the vehicle runs on battery alone. As the engine kicks in the fuel consumtion is high and fuel efficiency decreases. In the middle when the vehicle runs on battery alone the Fuel economy tries to improve.