A study of heat release rate distribution in a gas turbine combustor by acoustic measurements

Ph.D.Warren C. Strahl

Characterization of Performance of Short Stroke Engines with Valve Timing for Blended Bioethanol Internal Combustion

The present study provides a feasible strategy for minimizing automotive CO2 emissions by coupling the principle of the Atkinson cycle with the use of bioethanol fuel. Motor cycles and scooters have a stroke to bore ratio of less than unity, which allows higher speeds. The expansion to compression ratio (ECR) of these engines can be altered by tuning the opening time of the intake and exhaust valves. The effect of ECR on fuel consumption and the feasibility of ethanol fuels are still not clear, especially for short stroke engines. Hence, in this study, the valve timing of a short stroke engine was tuned in order to explore potential bioethanol applications. The effect of valve timing on engine performance was theoretically and experimentally investigated. In addition, the application of ethanol/gasoline blended fuels, E3, E20, E50, and E85, were examined. The results show that consumption, as well as engine performance of short stroke motorcycle engines, can be improved by correctly setting the valve controls. In addition, ethanol/gasoline blended fuel can be used up to a composition of 20% without engine modification. The ignition time needs to be adjusted in fuel with higher compositions of blended ethanol. The fuel economy of a short stroke engine cannot be sharply improved using an Atkinson cycle, but CO2 emissions can be reduced using ethanol/gasoline blended fuel. The present study demonstrates the effect of ECR on the performance of short stroke engines, and explores the feasibility of applying ethanol/gasoline blended fuel to it

The Reattachment Process of a Lifted Jet Diffusion Flame by Repetitive DC Pulse Discharges

On research of plasma assisted combustion, effects of electric and plasma discharges in DC, AC and pulse forms on reattachment of a lifted flame have attracted extensive attention. However, the detailed plasma assisted reattachment process and mechanism and roles of induced corona discharge and corona-induced ozone on the reattachment process are still unclear and undocumented. The forced reattachment process of a lifted diffusion jet flame by repetitive DC electric pulse discharges was experimentally investigated in this study using high-speed flame imaging, conditioned particle image velocimetry (PIV), and planar ozone concentration imaging. The forced reattachment process can be divided into three stages in sequence: ionic wind prior to corona initiation, corona initiation, and corona enhancement propagation. The conditioned PIV results showed that the instantaneous flame base propagation velocity is sufficiently enhanced beyond the laminar burning velocity for high pulse-repetition-frequency (PRF) cases at the instant of pulse discharge (on pulse) due to the enhanced oxidation of the corona induced ozone. By observing the dynamic flame-base behavior and evolution characteristics of the short-lived corona induced ozone for various PRFs, the novel forced reattachment process and mechanism of a lifted jet flame induced by repetitive DC electric pulse discharges is proposed

The effect of initial pressure on detonation propagation across a mixture

This study determines the effect of the initial pressure on the propagation of a Chapman–Jouguet detonation wave from a stoichiometric C 3 H 8 /O 2 mixture (donor) to a stoichiometric C 3 H 8 /air mixture (acceptor). Depending on the initial pressure ratio in the donor and the acceptor, the result can be a smooth transmission, a re-initiated detonation wave, or a transmitted shock wave. When the donor is divided into a driver donor and a driven donor, the degree of overdrive in a driven donor varies with the donor pressure ratio. There must be a greater degree of overdrive in the driven donor for re-initiation of a detonation wave in the acceptor, particularly if the initial pressure in the driven donor is lower than the Chapman–Jouguet pressure in the acceptor. The bi-dimensional effect is also another major factor

Effects Of Lewis Number On The Blowout Process Of Jet Flames

The effect of Lewis number on blowout process of jet flames was studied experimentally. Various fuels (H2, CH4, and C3H8) and diluents (Ar, N2, and CO2) were used to vary the Lewis number of fuel. For H2 and CH4 flames, the blowout velocity increased linearly with the fuel Lewis number (LeF) in LeF \u3c 1 and LeF \u3e 1 regions, respectively. However, for the C3H8 flame, the blowout velocity decreased linearly with increasing LeF in the LeF \u3c 1 region. The large discrepancies found between the measured blowout parameters and the theoretical critical values proposed by Broadwell et al. indicated that Lewis number effects must be included in the theoretical models. Local effective Lewis number affected flame structures during blowout process. The Lewis number affected the stability characteristics and the instability modes in the lifted flame base that may modify the blowout process leading to the onset of flame receding and consequently change the blowout velocity

Co-torrefaction of rice straw and waste medium density fiberboard: A process optimization study using response surface methodology

Co-torrefaction is a flexible way of improving the properties of various kinds of waste biomass for utilization as a clean solid fuel. Rice straw (RS) and medium density fiberboard (MDF) were used as feedstock for the torrefaction. Three input parameters were evaluated to determine the optimum conditions: rice straw ratio (RSR), torrefaction temperature and residence time. A response surface method based on a Box-Benhken design was used to achieve the optimum conditions (maximizing torrefied heating value and energy yield). Main and interaction effects for the independent variables on the responses were investigated based on analysis of variance (ANOVA). The findings revealed that temperature was the main effect and that there was no interaction effect between the inputs. Thus, a lower temperature optimized co-torrefaction. The optimum conditions for maximizing the heating value (22.13 MJ/kg) and energy yield (99.60%) were an RSR of 25%, a temperature of 208.10 °C and a residence time of 50 min. The experimental values were in good agreement with the corresponding predicted values. These findings should provide guidelines for the thermal pretreatment of mixed waste material for co-firing or co-gasification

A Study of the Production and Combustion Characteristics of Pyrolytic Oil from Sewage Sludge Using the Taguchi Method

Sewage sludge is a common form of municipal solid waste, and can be utilized as a renewable energy source. This study examines the effects of different key operational parameters on sewage sludge pyrolysis process for pyrolytic oil production using the Taguchi method. The digested sewage sludge was provided by the urban wastewater treatment plant of Tainan, Taiwan. The experimental results indicate that the maximum pyrolytic oil yield, 10.19% (18.4% on dry ash free (daf) basis) by weight achieved, is obtained under the operation conditions of 450 °C pyrolytic temperature, residence time of 60 min, 10 °C/min heating rate, and 700 mL/min nitrogen flow rate. According to the experimental results, the order of sensitivity of the parameters that affect the yield of sludge pyrolytic oil is the nitrogen flow rate, pyrolytic temperature, heating rate and residence time. The pyrolysis and oxidation reactions of sludge pyrolytic oil are also investigated using thermogravimetric analysis. The combustion performance parameters, such as the ignition temperature, burnout temperature, flammability index and combustion characteristics index are calculated and compared with those of heavy fuel oil. For the blend of sludge pyrolytic oil with heavy fuel oil, a synergistic effect occurs and the results show that sludge pyrolytic oil significantly enhances the ignition and combustion of heavy fuel oil