Intermittent engine operation : a way to reduce vehicle fuel consumption.

With conventional vehicle drivelines, the engine is normally run at low load, where its efficiency is poor. The fuel consumption could be reduced if the engine were run intermittently at high load and then disengaged. The surplus power produced when the engine is engaged can be used to charge an Energy Storage Unit (ESU), e.g. a flywheel. During the periods of disengagement, the ESU will drive the vehicle. Simulations show a possible reduction at road and city driving of 10 and 18 percent, respectively. Those values are valid for medium-sized and large cars. For small cars, the reductions were lower. An alternative to an ESU is to let the vehicle speed vary. The vehicle will then accelerate when the engine is engaged, and decelerate when it is disengaged. At road driving speeds, simulations indicated a fuel consumption reduction potential of about 14 percent. (A)