Thermodynamic analysis of spark-ignition engine using a gas mixture model for the working fluid

Abstract

SUMMARYThis paper presents thermodynamic analysis of spark-ignition engine. A theoretical model of Otto cycle, with a working fluid consisting of various gas mixtures, has been implemented. It is compared to those which use air as the working fluid with variable temperature specific heats. A wide range of engine parameters were studied, such as equivalence ratio, engine speed, maximum and outlet temperatures, brake mean effective pressure, gas pressure, and cycle thermal efficiency. For example, for the air model, the maximum temperature, brake mean effective pressure (BMEP), and efficiency were about 3000 K, 15 bar, and 32%, respectively, at 5000 rpm and 1.2 equivalence ratio. On the other hand, by using the gas mixture model under the same conditions, the maximum temperature, BMEP, and efficiency were about 2500 K, 13.7 bar, and 29%. However, for the air model, at lower engine speeds of 2000 rpm and equivalence ratio of 0.8, the maximum temperature, BMEP, and efficiency were about 2000 K, 8.7 bar, and 28%, respectively. Also, by using the gas mixture model under these conditions, the maximum temperature, BMEP, and efficiency were about 1900 K, 8.4 bar, and 27%, i.e. with insignificant differences. Therefore, it is more realistic to use gas mixture in cycle analysis instead of merely assuming air to be the working fluid, especially at high engine speeds.

Progress in Finite Time Thermodynamic Studies for Internal Combustion Engine Cycles

“…Refs. [89][90][91][92] advanced the SH model varied with temperature with nonlinear relation which was closer to practice:…”

“…Considering HTL, FL and IIL and fixing the cycle maximum temperature, Ge et al [84,167] adopted the VSH model advanced in [89][90][91][92], investigated the optimum power and efficiency performance [84,167], as well as the optimum EF performance [84] of an irreversible Diesel cycle, and examined the influences of the three losses on cycle performance. Furthermore, Aithal [168,169] studied the influence of exhaust gas recycle on the power output and efficiency performance characteristics of an irreversible Diesel cycle when the SH of WF were nonlinear functions of the temperature.…”

“…Furthermore, Aithal [168,169] studied the influence of exhaust gas recycle on the power output and efficiency performance characteristics of an irreversible Diesel cycle when the SH of WF were nonlinear functions of the temperature. Considering IIL and fixing the cycle maximum temperature, Açıkkalp and Yamık [170] used the VSH model advanced in [89][90][91][92], optimized the maximum available work output of an irreversible Diesel cycle with CR and pressure ratio as optimization parameters, and derived the optimum CR and pressure ratio.…”

“…Based on efficient power criteria, Patodi and Maheshwari [178] studied the Atkinson cycle performance when SH of WF varied linearly with temperature and analyzed the effects of some design parameters (including maximum temperature ratio, maximum volume ratio and maximum pressure ratio) on cycle performance under MP, MPD and MEP conditions. Considering HTL, FL and IIL and fixing the cycle maximum temperature, Ge et al [84,184] adopted the VSH model advanced in [89][90][91][92], investigated the optimum power and efficiency performance [84,184], as well as the optimum EF performance [84] of an irreversible Atkinson cycle, and examined the influences of the three losses on cycle performance.…”

“…Considering HTL, FL and IIL and fixing the maximum cycle temperature, Ge [84] and Chen et al [251] adopted a VSH model advanced in [89][90][91][92], investigated the optimum power and efficiency performance [84,251], as well as the optimum EF performance [84] of an irreversible Miller cycle, and examined the influences of the three losses on cycle optimum performance. Considering FL and HTL, Ebrahimi [252] investigated the optimum power and efficiency performance of an irreversible Miller cycle when SH of WF varied with temperature in a non-linear fashion, examined the influence of the ratio of expansion to compression on cycle performance, and found that the power output would first increase and then decrease when expansion-compression ratio increased.…”