Fuel Inlet Temperatures Research Articles

Comparative study of combustion processes generated by the use of different fuels: energy and exergy analysis

Through energy and exergy analysis, the present work revisits the combustion processes generated using different fuels (CH4, C3H8, H2, LPG, Natural gas and Biogas) under the same operating conditions. First, numerical computations, in which the turbulent dynamic k-ϵ model coupled with a probability density function (PDF) approach together with different sub-models that ensure the reliability of the results, are used. Then, the First and Second Laws of thermodynamics are applied to all fuel combustion cases considered previously to predict the energy loss, exergy destruction and their corresponding efficiencies. Next, variations in the air factor, the air inlet temperature and the fuel inlet temperatures are considered to analyse the response of combustion system performance as well as energy and exergy losses for the different fuels under investigation. The results show an amelioration of combustion parameters for the mixture of fuel and air using values of λ greater than 1. Also, the preheating of the inlet air temperature has a positive effect on energetic parameters. However, preheating the inlet fuel does not take a considerable role in the efficiency amelioration and loss reduction of the combustion system. It further turns out that biogas features higher energy efficiency compared to other fuels, at approximately 89.64%, while hydrogen fuel exhibits higher exergy efficiency at around 78.70% followed by biogas with 74.96%.

Investigation of preheated Dhupa seed oil biodiesel as an alternative fuel on the performance, emission and combustion in a CI engine

The present study investigates the suitability of preheated Vateria indica methyl ester (VIME) as an alternative fuel for a diesel engine. VIME is a renewable, non-toxic and sustainable alternative biodiesel obtained from Dhupa fat by transesterification. This study aims to evaluate the combustion, performance, and emission characteristics of four different blends such as B0 (0% VIME and 100% mineral diesel), B30, B50 and B100 at elevated fuel inlet temperatures ranging from 35 °C to 95 °C. The tests are carried out in a single cylinder diesel engine at optimum loading condition and fixed speed. Results are obtained in terms of brake thermal efficiency (BTE), brake specific fuel consumption (BSFC), in-cylinder pressure, heat release rate and exhaust emissions (CO, HC, NOX, CO2 and soot). It is observed that the preheating of blends decreases the viscosity which enhances fuel spray characteristics, leading to higher engine performance, lower CO and HC emissions with a slight increase in NOX and CO2 emissions. BTE and peak in-cylinder pressure for B100 at 95 °C and 75% load are increased by 7.44%, 2.97% respectively compared to unheated B100 biodiesel. BSFC, CO, HC emissions at 75% load for B100 at 95 °C are reduced by 26.73%, 28.08%, 42.7% respectively compared to unheated B100.

Thermoacoustic Oscillations in Multipath Heated Fuel Circuits

Pressure oscillations in supercritical jet-A fuel flowing through four parallel heated tubes connected to common manifolds have been observed in this study. Tests were performed with fuel inlet temperatures ranging from 70 °F to 700 °F, and fuel pressures ranging from 360 to 700 psi. Total fuel flow rate ranged from 5 to 55 lb/h. Tubes were heated by blowing 800–950 °F nitrogen over them. Acoustic-mode oscillations, typically ranging from 100 to 500 Hz, occurred only when a large temperature gradient was created inside the heated fuel tubes. Pressure oscillation amplitudes ranged from 0.1 to 1.0 psi. Oscillations at the inlet and outlet manifolds that were caused by a mode with the characteristic length of a single fuel tube were separated by a phase lag that was a function of the manifold cross-passage diameter. A lower frequency mode was also observed, which had a characteristic length based on the summed lengths of a single fuel tube and a single manifold passage. An acoustic simulation using the comsol acoustics module was performed to predict frequencies based on geometry and flow conditions of the experiment.

Effect of the fuel type on the performance of an externally fired micro gas turbine cycle

Externally fired gas turbines open the possibility of using fuels of lower quality than conventional gas turbines and internal combustion engines. This is because in externally fired gas turbines, the flue gases heat the compressed air in a high temperature heat exchanger. This heat exchanger can more easily deal with contaminants present in the flue gases. In this regard, the configuration of externally fired gas turbines represents an interesting option for biomass gasification gas. The contaminants and low heating value (LHV) of this fuel have made it difficult to find a conversion technology for heat and power generation. For this reason, it is important to study the influence of biomass derived gas as fuel on the performance of this system and consider the effects of the contaminants in the high temperature heat exchanger. This is studied in this work through simulations using Aspen Plus and Matlab. The test data of an externally fired micro gas turbine prototype was used to validate the simulation. The fuel considered was biomass gasification gas with varying concentrations of benzene 100, 10 and 1 g/Nm3 (hereafter named m100, m10, and m1 respectively). Additionally, mixtures of biomass derived gas and methane were studied for 10 and 50% of the thermal power of the combustor. The fuel inlet temperature to the combustor varied from 150 °C to 750 °C in order to represent the fuel gas after removal of particles by a cyclone and a filter. The results showed that the electrical power output increases when high fuel inlet temperatures to the combustor are used. Additionally, although it would be expected that fuels with higher LHV (lower heating value) show higher temperatures and higher output power, this does not always occur because of the composition of the fuels and their respective flue gas temperatures. The addition of methane does not have a large effect on the electrical power output. For a fixed temperature limit in the heat exchanger, the composition of the fuels does not play an important role. However, high fuel inlet temperatures to the combustor show slightly higher efficiencies. Additionally, the effect on the electrical power output of increasing the pressure drop as a result of increased thickness of deposit materials in the heat exchanger was analyzed.

Analysis of Residual and Operational Thermal Stresses in a Planar SOFC

A structural model has been developed for analysis of residual stresses for anode- and electrolyte-supported planar solid oxide fuel cells (SOFC). This model was also used for analysis of thermally induced stresses during operation for three different case studies with the electrolyte-supported geometry. Temperature distribution in the solid parts of the cell was modeled by means of an in-house electrochemical model, and the results were exported to the structural model. In the case studies, the impact of air and fuel inlet temperatures, steam reforming, and operation voltages on thermal stresses were studied. Weibull statistics were used for the prediction of failure probabilities and design considerations. Base case geometry for the electrolyte-supported cell was 50, 150, and 50 μm for anode, electrolyte, and cathode thicknesses, respectively, and for the anode-supported cell 1000, 20, and 50 μm, respectively. Analysis of residual stresses showed that, compared with the anode-supported cell, the electrolyte-supported cell experienced considerably higher stress levels in the anode and cathode due to the thick electrolyte, while the stress levels in the electrolyte were lower. For the anode-supported cell, maximum stress levels were 57, −12, and −678 MPa in the anode, cathode, and electrolyte, respectively, with negative values indicating compressive and positive values, tensile stresses. For the electrolyte-supported geometry, the corresponding levels were 282, 100, and −308 MPa, respectively. With a failure probability of 1E-6 and an electrolyte thickness of 10 μm, the minimum allowable anode thickness was estimated to be 1000 μm. For an electrolyte-supported cell, optimal thicknesses of electrolyte and anode were considered to be 100 and 100 μm, respectively, while the thickness of the cathode showed low impact. During operation, the stress levels were reduced considerably, since high operating temperatures reduce the temperature difference to the sintering temperature (1250 °C). Concerning the presence of methane in the fuel and the effect of steam reforming, small amounts of methane—as low as 10% of molar mass—were found to induce a cooling effect with correspondingly high gradients. With 45% methane in the fuel, the tensile stress level in the anode was about 130 MPa; the impact of thermal gradients was considered to be 40 MPa and the cooling effect also 40 MPa.

Experiments on behaviour of preheated rubber seed oil in a direct injection diesel engine

Rubber seed oil (RSO) is one of the vegetable oils that has potential for use as a fuel for diesel engines. Owing to the high viscosity of RSO, its performance is slightly inferior to diesel fuel. Preheating of RSO reduces its viscosity to the level of diesel fuel that improves the fuel spray and atomisation characteristics, leading to complete combustion. In this experimental work, the effect of various fuel inlet temperatures on the performance, emission and combustion characteristics of a single cylinder diesel engine was evaluated. The experimental results show that the brake thermal efficiency increases from 26˙6 to 28˙4% when the fuel is preheated to a temperature of 150°C. It also indicates that there is a reduction in the CO and smoke emissions with preheated RSO. The reduced ignition delay and combustion duration with RSO at 150°C indicates faster heat release and leads to higher thermal efficiency. It is concluded that the performance, combustion and emission characteristics are improved for preheated RSO compared to raw RSO, but it is still inferior to diesel.

Experimental investigations on the use of preheated animal fat as fuel in a compression ignition engine

The effect of fuel inlet temperature on performance, emission and combustion characteristics of a diesel engine is evaluated. A single cylinder direct injection diesel engine developing a power output of 2.8 kW at 1500 rev/min is tested using preheated animal fat as fuel. Experiments are conducted at the fuel inlet temperatures of 30, 40, 50, 60 and 70 °C. Animal fat at low temperature results in higher ignition delay and combustion duration than diesel. Preheated animal fat shows reduced ignition delay and combustion duration. Peak pressure and rate of pressure rise are found as high with animal fat at high fuel inlet temperatures. Heat release pattern shows reduced premixed combustion phase with animal fat as compared to neat diesel at normal temperature. Preheating improves the premixed combustion rate. At low temperature, animal fat results in lower smoke emissions than diesel. The maximum smoke density is K=6.5 m −1 with diesel and K=3.6 m −1 with animal fat at 30 °C. Preheated animal fat further reduces smoke levels at all temperatures. The smoke level is reduced up to K=1.7 m −1 with preheated animal fat at the temperature of 70 °C. Hydrocarbon and carbon monoxide emissions are higher with animal fat at low temperature as compared to diesel. Fuel Preheating reduces these emissions. NO emission is found as low with animal fat at low temperature. Fuel preheating results in increased NO emission. However, the level is still lower than diesel even at high temperature (i.e. 70 °C). On the whole it is concluded that preheated animal fat can be used in diesel engines with reduced smoke, hydrocarbon and carbon monoxide emissions with no major detoriation in engine performance.

The influence of the fuel inlet temperature on diesel engine exhaust gas emissions

The performance levels of diesel engines are influenced by a changing fuel inlet temperature. Investigations in this field have been carried out by Perkins [1]. Modern engine concepts are based on a standard and specific fuel inlet temperature, and a fuel temperature control system is often incorporated in order to maintain and optimise engine performance. A second test project by Perkins investigated what happens to exhaust gas emissions at different fuel inlet temperatures.