Kurs Oranı Ve Artık Gaz Kesrinin Otto Çevrimli Bir Motorun Performansına Etkisi

Abstract

İçten yanmalı motorların tasarım parametrelerinin pratik bir şekilde incelenmesi için sonlu zaman termodinamiği (FTT) modeli sıklıkla kullanılmaktadır. Yapılan bu çalışmada kurs oranı ve artık gaz kesrinin, tersinmezlikler, ısı kayıpları ve sürtünmenin de hesaba katıldığı bir otto çevrimli motorun performansı üzerindeki etkileri incelenmiştir. Çevrim başlangıç sıcaklığı artık gaz kesrinin bir fonksiyonu olarak tanımlanmıştır. Bu çalışma sonucunda kurs oranının artmasıyla, ve artık gaz kesrinin artmasıyla birlikte motor performansında belirgin bir seviyede düşüş yaşandığı görülmüştür.

Thermodynamic analysis of endoreversible six-stroke Otto cycle with respect to equivalence ratio, residual gas fraction and mean piston speed

“…In the figure 2, the 0→1 and 1'→0'→1"→0 processes shown in the P-v diagram are the gas change processes for the sixstroke Otto engine cycle. The relations between the fuel flow (̇) and mean piston speed ( ̅ ) [6][7][8], between ̇ and the fuel-air-residual gas (mixture) flow (̇) [6][7][8] are defined as:…”

“…where is the heat leakage coefficient of the cylinder wall. The relationship betweeṅ, ̇ andḣ can be defined as follows [6][7][8]:…”

“…The six-stroke Otto engine cycle is a modified version of the four-stroke Otto engine cycle, and for this reason, firstly equations have been presented for the four-stroke Otto engine cycle and finally the modifications required for the six-stroke Otto engine cycle have been explained [1]. The relations between the fuel flow (̇) and mean piston speed ( ̅ ) [6][7][8], between ̇ and the fuel-air-residual gas (mixture) flow (̇) [6][7][8] are defined as:…”

“…The term finite time thermodynamics, first applied by Curzon and Ahlborn in 1975, enables the examination of parameters affecting engine performance such as friction, heat transfer, variable specific heat, volumetric efficiency in ideal cycles, and acknowledges that the cycle has been completed in a certain time. Thus, ideal cycles are practically approximated to the actual engine cycle [7][8][9][10]. In the finite time thermodynamics, the cycles are internal-reversible and expressed as endoreversible [10].…”

“…Because the processes in the infinite time are realized as if they are quasi-static, the work output obtained from the cycle is maximum while the power is equal to zero. For this reason, it is very difficult to simulate the actual engine performance of the ideal cycles with the subject of classical thermodynamics and is not suitable for parametric work [6][7][8]. The term finite time thermodynamics, first applied by Curzon and Ahlborn in 1975, enables the examination of parameters affecting engine performance such as friction, heat transfer, variable specific heat, volumetric efficiency in ideal cycles, and acknowledges that the cycle has been completed in a certain time.…”