Improved model for the analysis of the Heat Release Rate (HRR) in Compression Ignition (CI) engines

Abstract

The accuracy of the Heat Release Rate (HRR) model of Internal Combustion Engines (ICEs) is highly depended on the ratio of specific heats, gamma ( ). Previous models were largely expressed as functions of temperature only. The effects of the excess air ratio ( ) and the Exhaust Gas Recirculation (EGR) rate on were neglected in most of the existing functions. Furthermore, previous HRR models were developed for stoichiometric or nearstoichiometric air -fuel mixtures in an engine condition. However, Compression Ignition (CI) engines operate over a wide range of . No work has been done to model the HRR of CI engines under nonstoichiometric conditions. Also, no work has been done to investigate the accuracy of existing functions specifically with respect to the modelling of the HRR of CI engines for nonstoichiometric conditions. The aim of this work was to develop an improved HRR model for the analysis of the HRR of CI engines for nonstoichiometric conditions ( > 1). In this work, a modified ( , ), was used to model the HRR of a 96 kW, multiple fuel injection, Euro V, Direct Injection (DI) engine. The modified HRR model (Leeds HRR model) predicted the fuel consumption of the engine with an average error of 1.41% confirming that the accuracy of the HRR model of CI engines is improved by using ( , ). The typical average error in the prediction of the other models was 16%. The much improved HRR model leads to more accurate prediction of fuel consumption, which enables the development of and enhances better fuel consumption management strategies for engines and fuels. It was also ascertained in this work that EGR has insignificant effect on the HRR of CI engines at low and medium loads.

An Improved Heat Release Rate (HRR) Model for the Analysis of Combustion Behaviour of Diesel, GTL, and HVO Diesel

“…Therefore, it can be concluded that has a significant effect on when alternative fuels are used in CI engines. Olanrewaju, F.O., et al, [2] also showed that had a significant effect on when the engine was run on off-road diesel.…”

“…In this work, the modified function, ( , ) and the Leeds HRR model developed by Olanrewaju, F.O., et al, [2] were used to investigate the combustion behaviour of standard diesel (ULSD), GTL diesel, and (HVO) diesel. At low and medium loads, the effect of EGR rate on the HRR of a CI engine was found to be insignificant [2]. Therefore, EGR rate was not considered in this work.…”

“…The Leeds CI engine HRR model of Olanrewaju, F.O., et al, [2] (Eq. ( 8)) was used in this investigation.…”

“…Complete combustion of the evaporated fuel mass per injection 7. The unburned fuel mass was negligible owing to lean combustion and auto-ignition of compressed charge in diesels [2].…”

“…The existing models of were largely expressed in terms of the temperature of the gases in the cylinder even though is known to be strongly depended on the excess air ratio ( ) of the engine. The authors of the current work have developed an HRR model, Leeds HRR, [2] that has a better accuracy in terms of the prediction of the fuel consumption compared to the experimental results (measurement). The aim of this work was to apply and validate the model to alternative fuels: Gas-to-Liquid (GTL) diesel, and Hydrotreated Vegetable Oil (HVO) diesel.…”