Assignment 1 solutions

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Concordia University *

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Mechanical Engineering

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Apr 3, 2024

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Assignment 1 Solutions Total: 50 points Problem 1 on theoretical questions (20 ponints) a. Draw the topology of a series-parallel hybrid electric vehicle (5 points). Describe all possible operating modes of a series-parallel hybrid electric vehicle (8 points). b. Describe the key components of a Plugin hybrid electric vehicle and what is the main difference with other types of electrified vehicle? (7 points) a. The topology of a series-parallel hybrid electric vehicle is a combination of the series and parallel hybrids, and it can have various topologies due to the location for coupling the engine and motor output. The key feature of this type of hybrids is that it has two electric machines with one connected to the engine for electrical power generation and one mainly for traction. Students can draw it as one of the two diagrams shown below. Engine Generator Traction motor

Operation modes: • Motor alone mode: 1) Vehicle is only propelled by the motor with supply from battery only; or 2) the motor is supplied by both the battery and the engine generator when the battery SoC is low. • Engine alone mode: Vehicle is only propelled by the ICE (traction) • Combined mode: Both ICE and motor drive the vehicle during high power demand. • Power split mode: For ICE power higher than vehicle demand, engine power is split to drive the vehicle and charge the battery via the generator. • Stationary charging mode: The vehicle is stationary, and the engine drives the generator to charge the battery. • Regenerative braking mode: Traction motor works as a generator to recharge the battery. • Hybrid battery charging mode: Both the engine–generator and the traction motor operate as generators in braking to charge the batteries. b. The key components of a Plugin hybrid electric vehicle are similar to the other hybrids with 1) Internal Combustion Engine; 2) Electric motor and/or generator; 3) Battery pack/supercapacitor; 4) Power Electronics and Control Unit; 5) Hybrid drivetrain; and 6) the interface or connecting unit for charging (onboard charger or the charging outlet for connecting to external chargers). • Compared with the non-plugin hybrids, PHEV includes the interface for charging and it has higher energy storage capacity that enables a longer driving range in the electric-only mode. • Compared with battery or fuel cell electric vehicles, PHEV includes an engine for extending the vehicle driving range with the alternative energy source. Problem 2 on vehicle efficiencies (12 points) Find the energy usage for traveling a distance of 1 km by an ICE car and a battery electric vehicle considering well-to-wheel energy efficiency. a. Consider that petrol for ICE cars has a calorific value of 34.3 MJ/liter. There are 30% losses in the process of refinery & distribution to gas stations. The ICE car can travel 11 km/liter. Calculate the energy in Wh for this ICE car to travel a distance of 1 km considering the well- to-wheel energy usage. (note: 1 Wh = 3,600 J) (8 points)

b. In the case of battery electric vehicle, the EV itself consumes 200 Wh battery energy per km. For well-to-wheel efficiency, consider that the power generation efficiency (losses in refinery and power conversion are all considered) is 40%, the transmission and distributions losses is 10%, the battery charger efficiency is 92%, the full cycle battery charging and discharging efficiency is 95%. Determine the energy in Wh for this EV to travel a distance of 1 km considering the well-to-wheel energy usage. (4 points) Note: Calculation for problem 2a . is that the energy content of petrol (34.3 MJ/liter) minus the refinement & transportation losses (30%), multiplied by the km per liter. Problem 3 on Basic sizing of an EV Powertrain (18 points) When we size the powertrain of an EV, we must ensure sufficient tractive force for the vehicle to: • accelerate from zero speed to a certain speed within a required time limit • overcome wind resistance force if headwind speed is non‐zero • overcome aerodynamic force • overcome rolling resistance • climb a certain slope (grade) You are asked to find the approximate ratings of an electric vehicle powertrain with a vehicle mass of 1,000 kg.

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a. Determine the total tractive force needed to accelerate at 5 m/s 2 , assuming that aerodynamic, rolling, and hill‐climbing force counts for an extra 10% of the needed acceleration force. (4 points) b. What is the time required for the vehicle to accelerate from 0 to 100 km/h. (4 points) c. Calculate the average and peak power needed to accelerate the vehicle from 0 to 100 km/h. (6 points) d. Determine the tractive force needed for this vehicle to accelerate to 100 km/h in 10 seconds, assuming a constant acceleration. What is the average and peak power required for this acceleration? (4 points) a. Determine the total tractive force needed to accelerate at 5 m/s 2 , assuming that aerodynamic, rolling, and hill‐climbing force counts for an extra 10% of the needed acceleration force. F te = 1.1 × mass × acceleration =1.1 × 1000 × 5 = 5500N b. What is the time required for the vehicle to accelerate from 0 to 100km/h? 0 0 5 100 / 27.78 / 27.78 5.556 5 v v at t km h m s t s = + = + = = = = Note: the energy required to accelerate the vehicle from 0 to 100 Km/h is: 2 2 1 1 Energy required=1.1 1.1 1000 27.78 424450.62 2 2 Mv J   × = × × × =     There can be some other ways to calculate the energy. c. Now, we can calculate the average and peak power needed to accelerate the vehicle from 0 to 100 km/h. 424450.62 averge power= 76.395 5.556 energy kW time = = peak power=F 5500 27.78 152.79 tr v kW × = × = d. Determine the tractive force needed for a 1000kg vehicle to accelerate to 100km/h in 10 seconds, assuming a constant acceleration. What is the power required for this acceleration?

_ _ max 27.78 1000 2778 10 The peak power= 2778 27.78 77.2 77.2 The average power= 38.6 2 tr new tr new dv F Ma M N dt F V kW kW kW = = = × = × = × = =