A Specific Heat Ratio Model for Single-Zone Heat Release Models

Abstract

The objective is to investigate models of the specific heat ratio for the single-zone heat release model, and find a model accurate enough to introduce a modeling error less than or in the order of the cylinder pressure measurement noise, while keeping the computational complexity at a minimum. Based on assumptions of frozen mixture for the unburned mixture and chemical equilibrium for the burned mixture, the specific heat ratio is calculated using a full equilibrium program for an unburned and a burned air-fuel mixture, and compared to already existing and newly proposed approximative models of γ. A two-zone mean temperature model, Matekunas pressure ratio management and the Vibe function are used to parameterize the mass fraction burned. The mass fraction burned is used to interpolate the specific heats for the unburned and burned mixture, and then form the specific heat ratio, which renders a small enough modeling error in γ. The specific heats for the unburned mixture is captured within 0.2 % by a linear function, and the specific heats for the burned mixture is captured within 1 % by a higher-order polynomial for the major operating range of a spark ignited (SI) engine.

Double-Wiebe function: An approach for single-zone HCCI engine modeling

“…Within this type of zero-dimensional model, combustion progress can be described by a Wiebe function fitted as far as possible to the accumulated heat release derived from the measured cylinder pressure [24]. The Wiebe method can describe the engine operating conditions for which it has been tuned and is often accurate enough to be used for semi-predictive modeling if care is taken when analyzing the results [25].…”

Enhanced heat release analysis for advanced multi-mode combustion engine experiments

“…Thermo-physical gas properties Thermo-physical gas properties are calculated based on the thermodynamic data in the JANAF tables [54] and Burcat's Thermodynamic Database [55], along with a 15-species equilibrium model. This approach avoids potential shortcomings associated with simple correlations for specific heat ratio, c, commonly used in heat release analysis [11,12,16,[56][57][58][59]. The species included in the gas properties routines are: H, O, N, H 2 , OH, CO, NO, O 2 , H 2 O, CO 2 , N 2 , Ar, NO 2 , HO 2 and fuel.…”

Homojen Karışımlı Sıkıştırma Ateşlemeli (HCCI) Bir Motorun Tek Bölgeli Modelleme Yöntemi Kullanılarak Analizi

“…Bununla birlikte, en basit yaklaşım tek-bölgeli model olup bu yöntemle de oldukça iyi sonuçlar alınmaktadır. Tek-bölgeli 0-Boyutlu modellerde yanma olayı Wiebe fonksiyonu ile tanımlanabilir [30,31]. Bununla birlikte, HCCI motorlarda yanma olayının standart Wiebe fonksiyonu ile modellenmesi ile iki sorun ortaya çıkmaktadır.…”