|The KSPG-FEV two-cylinder range extender. Click to enlarge.|
Automotive supplier KSPG Automotive (formerly Kolbenschmidt Pierburg), a subsidiary of Rheinmetall AG, and FEV have jointly developed a concept for a compact, 30 kW range extender for battery-electric vehicles. KSPG is showcasing the unit, along with other of its engine efficiency technologies such as the UniValve variable valve system, at the Detroit Auto Show.
The new power unit consists of a two-cylinder, 800 cc V-type gasoline engine with a vertically positioned crankshaft and two generators with gear wheel drive. The use of two generators (2 x 15 kW) serves to provide balance for the two-cylinder V-configuration to help to reduce NVH (noise, vibration and harshness) from the engine—especially important in a range-extending application for a battery-electric vehicle, which normally is quiet.
The system also includes FEV’s Full Engine Vibration Compensator (FEVcom), which has been designed into the range extender to reduce NVH. With FEVcom, a reduction in the engine vibration of more than 95% at the engine mount could be measured in various engine applications, according to FEV.
KSPG sized the output to 30 kW, said Dr. Hans-Joachim Esch, Chief Technical Officer, based on the need for the target A-segment vehicle “to be faster than a truck”. KSPG analysis found that 26 kW was sufficient to move the car up a grade of 3% at 100 km/h; they chose 30 kW.
The engine, with a 90° V, is port fuel injected, with two valves per cylinder, and meets Euro 6 emission requirements. A combined cooling circuit serves the inverter, generator and combustion engine.
Except for the fuel tank and the radiator, all components, including the power electronics, are mounted on a support frame. The vertical crank shaft requires only a short construction height, such that the module can be integrated beneath the floor of a small passenger vehicle and, for example, be placed comfortably within a spare tire well in the trunk. This installation option offers the easiest and least expensive modification procedure relative to conventional vehicle construction and leaves room for interesting compact vehicle packaging and styling options.
The range extender weighs a little more than 60 kg, together with the generators and all related parts.
The power unit is conceived in such a way that the vehicle interfaces are reduced to a minimum. Vehicle integration thus proves comparatively unproblematic and installation or disassembly can be performed easily and efficiently, according to KSPG. This enables the range extender to be reduced to an additional accessory equipment option. The automobile can thus be delivered with or without a range extender and allows for a modular design concept.
A bridge technology such as a range extender could expedite market entry for a new generation of battery-powered vehicles and support legislators in their efforts to reduce CO2 emissions, KSPG suggests. The advantages of such power units lie in the fact that they reduce battery size and costs and lower additional related weight. With range extenders, normal ranges can be achieved even without long en route recharging periods.
Variable valve system. KSPG acquired the rights to the “UniValve” variable valve system conceived by enTec Consulting GmbH and is now pressing ahead with development toward series production. UniValve is a mechanical system for the simultaneous and continuous adjustment of valve lift and opening event. The control shaft is driven by a wear-free, brushless electric motor. Dyno tests with a complete engine have already been conducted with an early group of customers and have demonstrated attractive potential for reducing fuel consumption and emissions with high operating reliability, according to KSPG.
In a gasoline engine with fully variable valve train the fresh air-fuel mixture providing the engine output is no longer controlled by the throttle flap, but rather through the selection of valve timing and valve lift. Through early closure of the intake valve, both the gas exchange work and the (directly related) specific fuel consumption steadily decrease. In order to reap the advantages of very early closure, the opening event must therefore be as short as possible. For engines with conventional, i.e. non-variable valve trains, this represents a trade off to the maximum engine performance, calling for longer opening events and late intake closure.
By contrast, UniValve allows continuous variation of the valve opening event with a simultaneous, operationally specific adjustment of valve lift all the way down to zero lift. The system on the one hand thereby reduces partial load fuel consumption due to less pumping work, an optimized residual gas control and a high dilution capability of the combustion process, and on the other hand through the reduced power demand for valve activation.
When used on the intake side, UniValve can lower partial load fuel consumption of conventional, naturally aspirated gasoline engines in combination with cam-phasing systems by up to 12%. At the same time, its high flexibility also allows an increase in low end torque and engine performance. A smaller engine can thus deliver the same driving performance and open up additional consumption advantages through this downsizing.
The exhaust side also considerably influences the gas exchange process and consumption to such an extent that at least cam phasers should be available. An engine with fixed exhaust valve timings cannot fully utilize the large potential of the UniValve that has been opened up on the intake side; it is therefore more advantageous, KSPG suggests, when the UniValve system is also used on the exhaust side. This is especially true for the increasingly popular turbocharged four-cylinder gasoline engine.
The trade-off between partial load fuel consumption and high low end torque can be significantly mitigated. In a test involving a turbocharged 2.0-liter, four-cylinder gasoline engine, it was possible to reduce fuel consumption in a representative partial load point by 9% compared to throttled operation with direct fuel injection. At the same time, torque was significantly increased at low end.