Friday, June 21, 2013

Renault presents new hybrid power unit for F1 in 2014

Renault's hybrid power unit for F1 in 2014 includes a turbocharged, direct-injected 1.6L engine plus two motor generator units for energy recovery and use: the MGU-H (heat) and MGU-K (kinetic). Click to enlarge.

At the Paris Air Show at Le Bourget, Renault presented its new power unit designed to the new technical regulations to be used in the FIA Formula One world champion ship from 2014 onwards: the Energy F1-2014. The regulations call for a 1.6L direct injection Turbo V6 plus a single turbocharger; an electric motor for boost is allowed

There is a strong focus on improved vehicle fuel efficiency / reduced fuel consumption, with the fuel quantity for the race limited to 100 kg-about a 35% reduction from the current V8 F1 engines. Fuel mass flow rate is limited to 100 kg/hr max (it is currently unlimited), and Energy Recovery Systems (ERS) are allowed.

The Renault Energy F1 V6 has the required displacement of 1.6 litres and will make around 600 bhp (448 kW). It uses two motor generator units (MGUs): an MGU-H for waste heat energy recovery and an MGU-K for kinetic energy recovery during braking.

The MGU-H is connected to the turbocharger. Acting as a generator, it absorbs power from the turbine shaft to recover heat energy from the exhaust gases. The electrical energy can be either directed to the MGU-K or to the battery for storage for later use. The MGU-H is also used to control the speed of the turbocharger to match the air requirement of the engine (eg to slow it down in place of a wastegate or to accelerate it to compensate for turbo-lag.)

The MGU-K is connected to the crankshaft of the internal combustion engine and is capable of recovering or providing power, limited to 120 kW (160 bhp) by the rules. Under braking, the MGU-K operates as a generator to slow the car (reducing the heat dissipated in the brakes) and so recovers some of the kinetic energy and converts it into electricity. Under acceleration, the MGU-K is powered (from the Energy Store and/or from the MGU-H) and acts as a motor to propel the car.

The Power Unit's ERS (Energy Recovery System) uses the MGU-H and MGU-K plus an energy store, plus some power and control electronics. Heat and kinetic Energy recovered can be consumed immediately if required by the other MGU, or used to charge the energy store. The stored energy can be used to propel the car by the MGU-K or to accelerate the turbocharger by the MGU-H.

Compared to 2013 KERS, the ERS of the 2014 Power Unit will have twice the power (120 kW vs 60 kW) and a performance effect 10 times greater.

The F1 cars for 2014 may be categorized as a hybrid electric vehicle (HEV), which combines a conventional internal combustion engine with an electric propulsion system, rather than a full electric vehicle (EV). Like road-going HEVs, the battery in the F1 cars is relatively small sized. The relevant technical regulations mean that if the battery discharged the maximum permitted energy around the lap, the battery would go flat just after a couple of laps. In order to maintain "state of charge" (SOC) of the battery, electrical energy management will be just as important as fuel management.

The overall objective is to minimize the time going round a lap of the circuit for a given energy budget. This might sound nothing like road-relevant, but essentially, this is the same problem as the road cars: minimizing fuel consumption for a given travel in a given time-the input and output are just the other way around.

Choosing the best split between the fuel-injected engine and electric motor to get the power out of the Power Unit will come down to where operation of these components is most efficient. But again, SOC management presents a constraint to the usage of the electric propulsion. And the optimum solution will vary vastly from circuit to circuit, dependent on factors including percentage of wide open throttle, cornering speeds and aerodynamic configuration of the car.

There are quite a few components which will be directly or indirectly controlled by the energy management system; namely the internal combustion engine, the turbo, the ERS-K, ERS-H, battery and then the braking system. Each has their own requirement at any given time, for example the operating temperature limit. There can also be many different energy paths between those components. As a result, the control algorithm can be quite complex to develop and manage.

What is clear, however, is that at any given time, as much energy as possible, which would otherwise be wasted, will be recovered and put back into the car system. It would not be an over-estimation to state that the F1 cars of next year are probably the most fuel and energy efficient machines on the road.

-Naoki Tokunaga, technical director for new generation Power Units