Purpose – The purpose of this paper is to examine the effects of heat capacity and density of biofuels on aircraft engine performance indicated by thrust and fuel consumption. Design/methodology/approach – The influence of heat capacity and density was examined by simulating biofuels in a two-spool high-bypass turbofan engine running at cruise condition using a Cranfield in-house engine performance computer tool (PYTHIA). The effect of heat capacity and density on engine performance was evaluated through a comparison between kerosene and biofuels. Two types of biofuels were considered: Jatropha Bio-synthetic Paraffinic Kerosene (JSPK) and Camelina Bio-synthetic Paraffinic Kerosene (CSPK). Findings – Results show an increase in engine thrust and a reduction in fuel consumption as the percentage of biofuel in the kerosene/biofuel mixture increases. Besides a low heating value, an effect of heat capacity on increasing engine thrust and an effect of density on reducing engine fuel consumption are observed. Pr...

Passive control is a method used to control the base pressure of the convergent-divergent nozzle for high speed vehicles. The passive control contributes significant reduction of base pressure which mainly depending on many factors such as number of ribs, flow Mach number and rib’s size. The flow behaviour inside the nozzle at the respected factors still unknown. Therefore, this study aims to assess the effect of ribs in a suddenly expanded flow to control the base pressure at sonic Mach numbers. The study is performed using ANSYS Fluent. The flow expands in a duct with 18 mm diameter and 108 mm length. The ribs have aspect ratios of 3:1 to 3:3 which were fixed to the duct circumferentially. The position of the rib varies from 1D (duct diameter) to 4D and having different aspect ratios. The level of expansion varies from 1.5 to 5 while the rib is fixed at a 3:3 aspect ratio. The variation of pressure and velocity contours of the flow inside the nozzle are presented. The simulation analysis indicates that the flow expansion with the presence of ribs considerably improves the base pressure. It is concluded that at the flow with sonic Mach number, the rib with a 3:3 aspect ratio located at 4D has shown the highest improvement in base pressure.

Awareness of environmental and economic issues associated with fossil fuel has led to the exploration of alternative fuels for aviation. Analysis and measurements of alternative fuel using real aircraft engines are complex and costly. Thus, evaluation only through computation is an option at present. This paper presents an analysis of aircraft engine emissions, particularly NO_x and CO, from the blend of bio-synthetic paraffinic kerosene (bio-SPK) fuel with kerosene using a simplified gas emission model. Three different fuels, namely, a conventional aviation fuel Jet-A, Jatropha bio-SPK and Camelina bio-SPK were tested as pure and as blends with Jet-A. Chemical properties of the tested fuels were introduced into HEPHAESTUS, an in-house gas emission software developed in Cranfield University. HEPHAESTUS was developed based on the physics-based approach by incorporating a number of stirred reactors to predict NO_x, CO, UHC and soot. Gaseous emissions generated from kerosene were observed to follow the trends provided by the ICAO databank. The capability of HEPHAESTUS in predicting the NO_x and CO level from biofuel is yet to be explored. The level of NO_x and CO predicted in this study followed the trends shown in the literature, although they quantitatively differed. Compared to Jet-A, NO_x decreased and CO increased as the percentage of Jatropha bio-SPK and Camelina bio-SPK in the mixture increased. NO_x reduction was consistent with the reduction in flame temperature because NO_x generation considered in the model was dominantly based on thermal NO_x. In contrast, increases in CO were due to low flame temperature that led to incomplete combustion. The consistency of the results obtained showed that the computational work performed in this study as an initial step toward the prediction of emission level of biofuels was successful. However, further studies on the experimental work or computational fluid dynamic simulation is essential.