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Reciprocating Engines
Published in Neil Petchers, Combined Heating, Cooling & Power Handbook: Technologies & Applications, 2020
Mep is the constant averaged pressure on the piston over the length of the piston stroke. It reduces the varying pressure on the piston to a single averaged value. Mep is useful in evaluating the ability to produce power. Since the product of piston travel and piston area is piston volume (displacement), the relative power-producing capability of two pistons can be established by comparing the product of mep times displacement in each case. The force on the piston is equal to the pressure times the area (A). Since mep is equivalent to a constant force on the piston over the length of the piston stroke, the work done per power stroke is F times L, where L is the length of the stroke. Thus, for a given displacement, mep is useful in evaluating an engine’s ability to produce power due to the following relationship: () Enginepower=displacement×speed×mep
Thermal cycles
Published in Mike Tooley, Lloyd Dingle, Engineering Science, 2020
The MEP is effectively a measure of engine work and thus power, and is the average constant pressure that is assumed to act over the whole swept volume of the cycle that produces the same power output as the actual cycle. Figure 15.6 illustrates the concept of MEP.
Investigation of water/steam direct injection on performance and emissions of two-stroke marine diesel engine
Published in International Journal of Green Energy, 2021
Xiuxiu Sun, Zhiyuan Jia, Xingyu Liang, Guoxi Jing, Hai Liu, Guoji Shen, Sen Xiao
The comparisons of brake power for WI and SI at different injected timing are shown in Figure 4. The obvious difference was found for WI and SI on the effect of brake power. The brake power decreases by using WI method, especially injected water during the combustion process. The reduction range of brake power is increased from 2.1% to 9.3%. The brake power increases by using SI method when steam was injected at −50 °CA. The brake power increases 7.8% at 10 °CA. The power is directly proportional to mean effective pressure. The mean effective pressure is lower than that of the baseline engine by using WI method. It can be obtained from Figure 3(b). The WI method cannot improve the performance of marine engine. However, it can reduce NOx emissions significantly, as can be seen in Figure 5.
Effects of ethanol, methyl tert-butyl ether and gasoline-hydrogen blend on performance parameters and HC emission at Wankel engine
Published in Biofuels, 2020
The volumetric efficiency curves are given in Figure 6 for gasoline, ethanol, MTBE and the gasoline–hydrogen mixture. The torque in an internal combustion engine is a direct function of the volumetric efficiency and the brake mean effective pressure. The volumetric efficiencies of G98H2 and ethanol are overall 5.87% and 4.89% higher than that of gasoline, respectively. The volumetric efficiency for gasoline is overall 1.92% lower than that of MTBE. The volumetric efficiency values reached a maximum of 95% at 5000 rpm for ethanol and G98H2, whereas the volumetric values for MTBE and gasoline reached approximately 89% at 5000 rpm. The volumetric efficiency values for the four fuels decreased sharply in the range 5000–6000 rpm. Hydrogen addition in gasoline leads to taking heat from the stroke volume and increases the volumetric efficiency. Ethanol has nearly 3 times the heat of vaporization of gasoline, providing greater cooling effects in the engine and improving volumetric efficiency.
Modeling and Simulation of Single Ethanol/Water Droplet Evaporation in Dry and Humid Air
Published in Combustion Science and Technology, 2020
P. Narasu, S. Boschmann, P. Pöschko, F. Zhao, E. Gutheil
Costa and Sodré (2010) compared the performance of a four-stroke engine fueled by hydrous ethanol or gasoline-ethanol blends. It was observed that when hydrous ethanol fuel was used, higher torque, break mean effective pressure and power were attained for high engine speeds. For low engine speeds, the power produced was about the same by both the fuels. Throughout the engine speed range studied, higher specific fuel consumption and higher thermal efficiency were observed by hydrous ethanol compared to the gasoline-ethanol blend. This provides motivation for further research on hydrous ethanol combustion.