John N. Harman

Bio: John N. Harman is an academic researcher from University of California, Irvine. The author has contributed to research in topics: High-temperature electrolysis & Nuclear engineering. The author has an hindex of 1, co-authored 1 publications receiving 7 citations.

Chemical transformations of nitrogen oxides while sampling combustion products

Abstract: The study reviews the sampling environments and chemical transformations of nitrogen oxides that may occur within probes and sample lines while sampling combustion products. Experimental data are presented for NO/sub x/ transformations in silica and 316 stainless steel tubing when sampling simulated combustion products in the presence of oxygen, carbon monoxide, and hydrogen. A temperature range of 25 to 400/sup 0/C is explored. In the absence of CO and H/sub 2/, 316 stainless steel is observed to promote the reduction of nitrogen dioxide to nitric oxide at temperatures in excess of 300/sup 0/C, and silica is found to be passive to chemical transformation. In the presence of CO, reduction of NO/sub 2/ to NO is observed in 316 stainless steel at temperatures in excess of 100/sup 0/C, and reduction of NO/sub 2/ to NO in silica is observed at 400/sup 0/C. In the presence of H/sub 2/, NO/sub 2/ is reduced to NO in 316 stainless steel at 200/sup 0/C and NO/sub x/ is removed at temperatures exceeding 200/sup 0/C. In silica, the presence of H/sub 2/ promotes the reduction of NO/sub 2/ to NO at 300/sup 0/C and the removal of NO/sub x/ above 300/sup 0/C.

Current Status of Ceres Electrolysis Programme

Abstract: This paper reports on experimental testing and verification of Ceres solid oxide technology in electrolysis mode at all levels from small single cells to a 100-kW module. This programme has demonstrated that the electrochemical performance of Ceres core cell technology is broadly the same in fuel cell and electrolysis modes suggesting no fundamental difference when reversing the direction of current. Additionally, lifetime predictors such as degradation rate and resilience to thermal cycles and emergency stops, measured at stack level, show an equally high level of real-world robustness in electrolysis mode as in fuel cell mode. Finally, results from testing our first-of-a-kind 100kW electrolysis module show reliable operation, high electrical efficiency of >87% (LHV) or 38kWh/kgH2 and stacks performing at the same level as measured on test stands.

Measurement of fuel mixing and transport processes in gas turbine combustion

Abstract: The measurement techniques for delineating fuel-air mixing and transport in gas turbine combustion, as well as examples of representative results, are provided in this overview. The summary is broken into applications for gaseous fuels and liquid fuels since many diagnostics which are specific to the phase of the fuel have been developed. Many possible methods for assessing the general mixing have been developed, but not all have been applied to practical systems either under scaled or under actual conditions. With respect to gaseous mixing processes, planar laser-induced fluorescence (PLIF) based on acetone is now starting to be successfully applied to actual systems and conditions. In spray-fired systems, the need to discriminate between phases leads to considerable complication in delineating fuel-air mixing. Methods that focus on the discrete phase have successfully provided details relative to the droplets. These include phase Doppler interferometry (PDI), which is becoming ubiquitous in application to practical devices and under practical conditions. PDI is typically being applied to quantify droplet sizes, although the volume flux, which is relevant to fuel-air mixing, in practical systems is also being reported. In addition, PLIF strategies that focus upon the behaviour of the droplets are now being developed. However, PLIF strategies that can discriminate between phases either in the fuel or with respect to the liquid fuel and combustion air are also being developed. In terms of characterizing the vector fields associated with the mixing process, laser anemometry (LA), although it is tedious to apply, has proven reliable even in the presence of droplets. Newer methods such as DPIV and FRS have seen only limited application in practical systems but appear promising. In terms of scalar fields, LIF and PLIF have also been applied successfully to these systems, and examples of the measurements of concentrations of various radical species such as OH are found throughout the literature.

On the Formation of Nitrogen Oxides During the Combustion of Partially Pre-Vaporized Droplets

Abstract: This study contributes to the topic of nitrogen oxide (NOx) formation at the level of single droplet and droplet array combustion The results show that the trade-off between ambient temperature and available oxygen determines the NOx formation of droplets burning in hot exhaust gas The degree of droplet vaporization has an effect on flame stabilization around the droplet and on NOx formation In the ignition model, the NOx production rate turns out to be very sensitive against the ignition position

Probe Measurements of Scalar Properties in Reacting Flows

Abstract: This paper presents a review of the capabilities of probe techniques for combustion diagnostic and outlines the most significant sources of error inherent to their use. The emphasis of the search is on measurements of temperature and on those of major species and ion concentrations in combusting environments, and attention is focused to elucidate the importance of probe measurements to improve understanding of turbulent combustion.

Fuel-rich, catalytic reaction experimental results

Abstract: Future aeropropulsion gas turbine combustion requirements call for operating at very high inlet temperatures, pressures, and large temperature rises. At the same time, the combustion process is to have minimum pollution effects on the environment. Aircraft gas turbine engines utilize liquid hydrocarbon fuels which are difficult to uniformly atomize and mix with combustion air. An approach for minimizing fuel related problems is to transform the liquid fuel into gaseous form prior to the completion of the combustion process. Experimentally obtained results are presented for vaporizing and partially oxidizing a liquid hydrocarbon fuel into burnable gaseous components. The presented experimental data show that 1200 to 1300 K reaction product gas, rich in hydrogen, carbon monoxide, and light-end hydrocarbons, is formed when flowing 0.3 to 0.6 fuel to air mixes through a catalyst reactor. The reaction temperatures are kept low enough that nitrogen oxides and carbon particles (soot) do not form. Results are reported for tests using different catalyst types and configurations, mass flowrates, input temperatures, and fuel to air ratios.