This patent describes a four-stroke cycle V-engine. Typical combustion mean effective pressures (MEPcombustion) of naturally aspirated gasoline engines are up to 10 bar, thus this concept has the potential to significantly increase the engine efficiency and fuel economy while not resulting in a decrease in power density. The range of MEPsteam calculated for the geometry of a conventional gasoline spark-ignited internal combustion engine and for plausible water injection parameters is from 0.75 to 2.5 bars. The value of this exhaust valve closing for maximum MEPsteam depends on the limiting conditions of either one bar or the dew point temperature of the expansion gas/moisture mixture when the exhaust valve opens to discard the spent gas mixture in the sixth stroke. By changing the exhaust valve closing angle during the exhaust stroke, the ideal amount of exhaust can be recompressed for the amount of water injected, thereby minimizing the work input and maximizing the mean effective pressure of the steam expansion stroke (MEPsteam). This concept has the potential of a substantial increase in fuel efficiency over existing conventional internal combustion engines, and under appropriate injected water conditions, increase the fuel efficiency without incurring a decrease in power density. Thus, this concept recovers energy from two waste heat sources of current engine designs and converts heat normally discarded to useable power and work.
An ideal thermodynamics model of the exhaust gas compression, water injection at top center, and expansion was more » used to investigate this modification that effectively recovers waste heat from both the engine coolant and combustion exhaust gas. Early exhaust valve closing during the exhaust stroke coupled with water injection are employed to add an additional power stroke at the end of the conventional four-stroke Otto or Diesel cycle. The engine cycle can be thought of as a 4 stroke Otto or Diesel cycle followed by a 2-stroke heat recovery steam cycle. =, number = 1049,Ī concept is presented here that adds two additional strokes to the four-stroke Otto or Diesel cycle that has the potential to increase fuel efficiency of the basic cycle.
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