Week-4 Challenge WOT Condition Part-2
In HEV WOT(wide open throttle) challenge Part - 2
1. The difference between mapped and dynamic model of engine, motor and generator
| Mapped Model Engine |
Model uses a set of steady-state lookup tables to characterize engine performance. The tables provide overall engine characteristics, including actual torque, fuel flow rate, BSFC, and engine-out exhaust emissions. |
Most of components are modelled by steady sate maps and charts in backward facing modelling approach, therefore energy consumption and performance of different components (engine) during transient periods of the drive are not calculated correctly. The mapped model is also known as the backward facing approach. |
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 tradeoffs. |
| Dynamic Model Engine |
Model decomposes the engine behavior into engine characteristics that are separated into lower-level components. By combining components in this way, the models capture the dynamic effects. |
The dynamic model uses the forward facing approach, . In the forward facing approach, required demands for torque, voltages and currents are compared with actual variables of the system |
Dynamic engine models are suitable for designing control, estimator, and diagnostic algorithms that depend on dynamic subsystem states, for example, in closed-loop AFR control algorithm development. |
Dynamic SI Engine Model
Dynamic EV engine
Mapped EV Engine
2. How to calculate miles per gallon?
Electric cars do not directly burn fuel, and so do not have fuel economy per se, but equivalence measures, such as miles per gallon gasoline equivalent have been created to attempt to compare them. One gallon of fuel is equal to 3.785 litres of gasoline and 1 mile is equal to 1.609Km of distance travelled.
The above diagram show the powertrain blockset of the EV vehicle to calculate the miles per gallon. The input given in the model is vehicle speed, fuel flow and battery power to get the vehicle fuel efficiency in terms of US MPG(miles per gallon) and L/100Km.
The step used in calcuation of the MPG is explained in the below
1. The distance is calculated by integrating the vehicle speed with the time and it is converted into miles by multiplied it with 0.000621371 factor and it also converted into 100km by dividing distance by the factor of 10^5.
2. The battery power consumed in covering the distance is calculated by converting the Watt into Kw by dividing it by 1000 and then multiply it with time to get power into the terms of KWhr. The KWhr is converted into the US MPG (miles per gallon) term by multiplying it with 33.7 factor. The KWhr/US gal equivalent is divided by 3600 to convert KWhr into KW-sec.
3. The volume flow rate of the fuel is expressed into the m^3 term is converted into gallon by multiplying it with 0.00378541 and then integrated with repect to time to calculate the volume of the fuel.
The Miles per gallon is calculated by dividing the distance covered by the vehicles ( 1 m = 0.000621371 miles) into miles and fuel used from the battery & the gasoline in terms of gallon(1 m^3 = 264.172 gallon).
The miles per gallon give the efficiency of the vehicle engine.
The Factors considered to model the fuel flow
1. Vehicle speed.
2. Battery power
3. Run the HEV Reference Application with WOT drive cycle. Change the grade and wind velocity in the environment block. Comment on the results.
A hybrid electric vehicle (HEV) is a type of hybrid vehicle that combines a conventional internal combustion engine (ICE) system with an electric propulsion system.
The hybrid electric vehicle reference application represents a full multimode hybrid electric vehicle (HEV) model with an internal combustion engine, transmission, battery, motor, generator, and associated powertrain control algorithms.
The hybrid electric vehicle model is selected with the Wide open Throttle drive cycle and we run the simulation in the matlab with the given input to the drive cycle.
The above diagram show the simulation result of the HEV engine with WOT drive cycle with the given input in the drive cycle. There are total 6 different plot in the image of differenent engine parameter. The x- axis show the time of 100 sec and the y axis show the value of the different parameter.
The Wind and Grade value is changed in the environment block of the powertrain blockset
The simulation result in this condition is different from the previous condition where the grade and the wind velocity is not considered.
Observation from both the simulation result
1. The top velocity in the 2nd simulation condition is not achieved but in the 1st simulation condition the top speed is more than the target top speed.
2. The fuel economy in the 2nd simulation is half of the 1st simulation result. The Engine speed is also reduced in the 2nd condition.
3. the rest of the parameter is same in both the siulation result.
4. Keeping all other parameters same, compare the simulated results of hybrid and pure electric powertrains.
Pure electric Vehicle
An electric vehicle is a vehicle that uses one or more electric motors or traction motors for propulsion.
keeping all the parameter same as in the HEV
With all this parameter, run the simulation and result obtained are plot in the given figure below
For the condition 2 with grade and wind velocity
If we compared the both simulation result of the EV vehicle we should get the variation in the top speed, engine speed and the fuel efficiency of the engine. The top speed, engine speed and the fuel efficieny is reduced compared with the 1st condition simulation result.
Compare between the HEV and EV
1. The fuel efficiency of the EV is too much high than the HEV vehicle.
2. The discharging rate in the EV is lower compared to the HEV and the Battery SOC is also higher in the EV.
3. The EV produced zero emission with respect to the HEV vehicle.
4. The HEV vehicle come with IC engine, motor and generator due to which its weight is more than the EV vehicle with has only motor for power producing.