Combustion of Ecodiesel - kerosene mixtures in gasturbine testing rig

Iva Ozana Prah1, Andreea Cristina Petcu2*, Razvan Carlanescu2, Cornel Sandu2, , Milan Ermacora3 , Morana Jaganjac1, Franz Tatzber4, Neven Zarkovic1

1 Division of Molecular Medicine, Laboratory for Oxidative Stress,Rudjer Boskovic Institute, Bijenicka 54, HR-10000, Zagreb Croatia

2 National Research and Development Institute for Gas Turbines COMOTI220D, Iuliu Maniu Boulevard, sector 6, 061126, Bucharest, Romania

3Obrt Ermacora, Zapresic, Nova cesta 25, Croatia4Dr Tatzber KEG, Vienna, Austria

*Andreea Cristina Petcu: andreea.petcu@comoti.ro

Abstract— One of nowadays major preoccupations is to diminish greenhouse gases and to find the best kind of biofuel. It should be from renewable, environmental friendly, not food feedstock and if possible, production of such fuel should be waste recycling and not producing more nus-products. This relates especially to fastest growing transport sector, air-transport. Ecodiesel is fuel additive made from waste cooking oil (WCO) and it is a renewable, but also sustainable fuel additive. It is produced without methanol, sodium hydroxide (NaOH) or any other toxic substance. The experiments were done on the Garrett 30-67 turbo-engine, poly-carburant engine which can operate using different fuel mixtures. In this research kerosene was supplemented with 10%, 20% and 40% of Ecodiesel. Based on the results in this paper, one can draw the conclusion that for a proper running of gas-turbine with Ecodiesel-kerosene mixtures, the injection system and/or the design of the combustion chamber should be modified. Significant carbonic and tar deposits were found in the combustion chamber. They can cause damage of various components in the turbo-engine. One possibility to resolve this problem is to preheat Ecodiesel to decrease its viscosity. Experiments regarding the use of biofuels on micro gas turbine have been done before, but running with biofuel has not come in commercial stage yet. If Ecodiesel could be used as kerosene additive it would be very beneficial for pollution caused by air-traffic and for expenses after initial investment in the necessary modifications.Keywords- gasturbine, biofuel, waste cooking oil, Ecodiesel,

exhaust gases.

I. INTRODUCTION

Current estimations are that aviation is using approximately about 3% of total fossil fuel consumption [1]. Predictions for the future fuel consumption are that it will grow with about 5% per year until 2027 [2] or 3% [3]. Forecasts are also that global oil consumption will increase from 85 million barrels a day in 2006 to 118 million barrels per day in 2030 [4], projected that aviation traffic growth will increase by 4.5% to 6% every year over the next 20 years, and that traffic will be doubling, every 15 years [5]. There is a consensus within the literature that fossil fuel resources for the production of kerosene and diesel fuel are disappearing.

So production and utilization of biofuels is and will be the key priority, to fulfill the goal of reducing greenhouse gas emissions and decrease the dependence of fossil derived fuel.

Road vehicles running on biofuels and its performances have been tested and monitored extensively and many reviews are available [6–9], but using biofuels in micro gas turbines is still in an experimental and not yet commercial stage [10]. Furthermore climate perturbations attributable to airplanes emissions has been extensively studied, but impact of aviation on air quality and human health globally was not researched a lot, so there is a real need for research about the subject.

Chronic exposure to CO may increase the severity of cardiovascular symptoms, persistent headaches, light-headedness, depression, confusion and nausea [11]. It was reported recently that exposure to CO can lead to damage to the heart muscle [12]. It was reported that cca.8000 [13] premature mortalities per year globally are caused by aviation transport emissions.

II. THE EXPERIMENT SETUP

A. Ecodiesel descriptionEcodiesel is fuel additive made from waste cooking oil

(WCO). It is a renewable, sustainable and biodegradable fuel additive. Ecodiesel is prepared as described in Austrian and Croatian patents, AT502540A12007-04-15, respectively, HRP20070130A2. The procedure for Ecodiesel oil processing differs from standard procedures used for biodiesel production. Namely, instead of toxic methanol used for the biodiesel production, the Ecodiesel was produced using ethanol, which is further recycled. This procedure includes catalysts like sodium and potassium hydroxide, carbonates and alkoxides, which need short times, 30 min., to complete the reaction even at room temperature, while homogeneous acid catalysts, commonly used catalysts, which include sulphuric acid, need higher temperatures (100ºC) and longer reaction times 3 to 4h [14]. Furthermore, neither additional heating nor sodium hydroxide (NaOH), which can pollute environment, are needed in Ecodiesel production, while they are normally used for biodiesel manufacturing.

WCO was collected in Zapresic, Croatia and processed at “Obrt Ermacora” company on the mini plant which was designed and built specially for producing Ecodiesel, following patented procedure. (fig. 1).

Figure 1.Prototype of mini plant for Ecodiesel processing

B. Micro gasturbine testing rigThe experiments were done on a Garrett 30-67 turbo-

engine, because this it is a poly-carburant engine and can operate using different mixtures for a short period of time (30 min). During each experiment, the following values have been recorded: battery amperage, and idling temperature, provided by the engine control system, and the CO, CO2, NO, NOx, O2

and SO2 percentage in the exhaust gas, by means of a gas analyser placed at the exit of the micro gasturbine.

The combustion experiment with Garrett gasturbine was started with 10% Ecodiesel – kerosene mixture and then followed 20% and 40% mixtures. Temperature, pressure and exhaust gases CO, CO2, NOx, O2 were measured and showed significant changes. In each experiment the micro gas turbine was started on kerosene, brought to a stable regime of functioning and then switched to function on the Ecodiesel/ kerosene mixture. After a quantity of 1 liter of this mixture has been consumed the micro gas turbine was switched back to kerosene and then stopped.

Figure 2. Micro gasturbine testing rig

Figure 3. Instrumentation of the gasturbine

III. RESULTS AND DISCUSSION

C. Results of pressure and temperatureDuring the experiments the function regime was:

Figure 4. Presure results from Garrett gasturbine combustion chamber.

From fig. 4 it can be observed that the pressure in the combustion chamber is the same during all tests. The Ecodiesel/kerosene mixture did not cause pressure changes. The 100% kerosen test’s duration was shorter because this test was done only to get a reference point.

Figure 5. Temperature results from Garrett gas turbine exhaust gases.

It was observed that during the starting phase (first 80 seconds) and the stopping phase the temperature evolution was the same because during all experiments in these phases the gasturbine functioned using only kerosene. When it was switched to Ecodiesel/kerosene mixtures, it had been noticed that the temperature has increased due to higher fuel consumption caused by lower combustion effiency.

D. Carbonic and tar depositsTo assess the combustion process, pictures of the gas

turbine combustion chamber were taken after running on kerosene supplemented with Ecodiesel in 10%, 20% and 40% percentages.

After each experiment the combustion chamber has been disassembled. Significant carbonic and tar deposits have been observed on the fire tube (fig. 6, fig. 7). These observations showed that the injection system or the combustion chamber geometry should be modified in the gas-turbine to function properly when using Ecodiesel/ kerosene blends.

Figure 6. Garrett gasturbine flametube after combustion with Ecodiesel (20%)

Figure 7. Garrett gasturbine flametube after combustion with Ecodiesel (40%)

E. Results of exhaust gases measurement It can be noted in fig. 8 that for low amount of ecodiesel

(10%, 20%), the time for the oxidation of CO to CO2 increases, in good correlation with the decrease of the lower energy content of the ecodiesel with respect to the kerosene. However, for larger amounts of ecodiesel (over 20 %), this trend is reversed. Also, as the percentage of ecodiesel in the mixture is increasing, the initial levels of CO tend to decrease. It has been

expected that with the increase of biofuel percentage in the mixture there will be also more carbonic and tar deposits on the flametube.

Figure. 8. CO concetrations (ppm) in exhaust gases.

The above observations correlate properly with the CO2

levels presented in fig. 9. As the amount of Ecodiesel in the mixture increases, the resulting CO2 concentration decreases, due to the lower CO oxydation rates observed earlier.

Figure 9. CO2 concentration (vol%) in exhaust gases.

It was reported that biofuels usually caused slight increase in NOx concentaions. Another explanation could be the random movement of the flame front (maximum temperature region, most likely to produce Nitrogen oxydation), due to turbulent fluctuations and the instabilities due to incomplete vaporization (fig.10).

In previous research diesel, biodiesel, vegetable oil and different blends of those were tested [15]. Researchers came up with a conclusion that alternative fuels additives in gas turbine offered few advantages, such as: 1) possibility of fuel preheating temperature higher than in diesel engines, 2) no possibility for fuel /lubricating oil mixing due to the presence of air-lubrication of the rotating parts, 3) continuous injection and combustion and lower pollutant emission [15].

Figure 10 NOx concentration (ppm) in exhaust gases

Figure 11. O2 concentration (vol%) in exhaust gases.

The oxygen concentration in the exhaust provides an inverse correlation of the combustion efficiency and that is consistent with the results in this experiment for temeprature in combustion chamber.

IV. CONCLUSION Based on these results one can draw the conclusion that, for

a proper functioning using Ecodiesel-kerosene mixtures, some changes regarding the injection system and/or the design of the combustion chamber of the gas turbine will have to be done. The resulted significant carbonic and tar deposits can cause damage to various components of the turbo-engine. Also the Ecodiesel should be preheated to decrease its viscosity.

Using Ecodiesel as additive to kerosene has few advantages. Because of processing with ethanol moisture is negligible and does not contain salt substances, proteins or carbohydrates that are detrimental for engines. Also supplementing diesel fuel with Ecodiesel showed less acrolein-protein adducts [16]. Considering higher temperature in combustion chamber and slightly lower combustion efficiency, using Ecodiesel still would be very cost effective, because feedstock is waste

material and together with production process, financial costs for this fuel additive are very low.

ACKNOWLEDGEMENTSThe authors wish to thank to Dr Frederique Battin Leclerc as this

work was supported within COST Action 0901 in the form of STSM (Short Research Scientific Mission).

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