Energy-saving Principle And Application Foundation Of New Cycle Internal Combustion Engine Based On Charge Transit And Water Injection

To greatly improve the efficiency of internal combustion (IC) engine, thereare many new cycle IC engines. Two common characteristics can be drawn bysummarizing some typical new cycle IC engines, which are charge transit andwater injection. Studying these two common characteristics has the greatsignificance to explain the energy-saving principle of the new cycle IC enginesand develop the new high efficiency IC engine.To study the energy-saving principle and application foundation of thesenew cycle engines, the author developed a test co-cycle engine based on atraditional4-cylinder4-stroke gasoline IC engine, which had the technologies ofcharge transit and water injection at the same time. The working cycle of theco-cycle engine is formed by one former cylinder and one later cylinder. Theburned gas of former cylinder is transferred into later cylinder by a connectionpipe, and the water is injected into the high temperature burned gas to evaporateand work in the later cylinder. By the experimental study, it was discovered that,compared with the original engine, the co-cycle engine could achieve lower fuelconsumption just by charge transit in low load conditions, and the co-cycleengine could save energy by water injection in high load conditions.The energy-saving principle of the co-cycle engine by the charge transit inlow load conditions is secondary expansion of the former cylinder’s burned gas.According to the working mode of the expansion cylinder, the secondaryexpansion engine could be separated into two working modes, which are2-stroke secondary expansion and4-stroke secondary expansion. Compared withthe traditional engine, the4-stroke secondary expansion working mode couldsave energy in low load conditions, while the2-stroke secondary expansionworking mode has higher working efficiency in high load conditions. Therefore,the author proposed a2/4stroke switchable secondary expansion engineconception to save energy in both low and high load conditions. According tothe simulation study, the energy-saving working condition of this new conceptengine could save fuel by10-17.6%and cover all of the frequently-usedconditions of a normal vehicle. For the water injection energy-saving technology, the principle is studiedby the water injected into high temperature gas in a fixed volume cylinder. Itwas discovered that the flashing boiling of water injection could improve theevaporation power capability. The author summarized three designing aims ofthe water injection engine, which are ‘one low and two high’. The cylinderpressure should be low when the water injected into the cylinder, the watertemperature should be high before injection, and the cylinder wall temperatureshould be high. Based on these aims, a flashing boiling water injection ICengine concept was proposed in this paper. Compared with the co-cycle engine,this new concept engine could pre-heat the water by the high temperature burnedgas outside the cylinder, pre-heat the cylinder wall by the burned gas afterheating the water, and exhaust the burned gas during the second stroke beforewater injection to decrease the cylinder pressure in the later cylinder. Accordingto the simulation, compared with the traditional IC engine, this new enginecould improve the torque by15.4%and decrease the fuel consumption by9.4%.The cylinder wall may get wet when the water is injected into the cylinder,which may increase the friction loss and wear. To improve the hydrophobicperformance of the cylinder wall, the elliptical vibration texturing (EVT) isproposed in this paper to generate different patterns on the cylinder wall andpiston ring surfaces. The experimental study showed that the surface wettabilitycan be controlled using EVT just by carefully choosing the process parameters.The surface hydrophobic performance can be improved by the dimple patterns.