Cyclic stress analysis of an air-cooled turbine vane

The effects of gas pressure level, coolant temperature, and coolant flow rate on the stress-strain history and life of an air-cooled vane were analyzed using measured and calculated transient metal temperatures and a turbine blade stress analysis program. Predicted failure locations were compared to results from cyclic tests in a static cascade and engine. The results indicate that a high gas pressure was detrimental, a high coolant flow rate somewhat beneficial, and a low coolant temperature the most beneficial to vane life

Use of cooling air heat exchangers as replacements for hot section strategic materials

Because of financial and political constraints, strategic aerospace materials required for the hot section of future engines might be in short supply. As an alternative to these strategic materials, this study examines the use of a cooling air heat exchanger in combination with less advanced hot section materials. Cycle calculations are presented for future turbofan systems with overall pressure ratios to 65, bypass ratios near 13, and combustor exit temperatures to 3260 R. These calculations quantify the effect on TSFC of using a decreased materials technology in a turbofan system. The calculations show that the cooling air heat exchanger enables the feasibility of these engines

Comparison of cooling effectiveness of turbine vanes with and without film cooling

The cooling effectiveness of three film-cooled vanes were compared to the cooling effectiveness of two non-film-cooled vanes. The comparison indicated that, for the vane configurations and test conditions examined, film cooling had an adverse effect near the suction-surface trailing edge of the vanes. Film cooling was found to be beneficial on the pressure surface of the vanes

Experimental transient vane temperatures in a cascade for gas stream temperature cycling between 922 and 1644 K (1200 and 2500 F)

Experimental transient turbine vane metal temperatures were obtained from tests conducted on air-cooled vanes installed in a four-vane cascade for a gas temperature cycled between 922 and 1644 K (1200 and 2500 F). Transient data were recorded by a high-speed data acquisition system. Temperatures at the same phase of each transient cycle were repeatable between cycles to within 11 kelvins (20 F), simulated cruise and idle steady-state readings were repeated by the cruise and idle readings taken from the ends of a transient half-cycle at low pressure to within 17 kelvins (30 F). The tests were conducted at pressure levels of 31 and 83 N-sq cm (45 and 120 psia) with coolant temperatures of 811 and 589 K (1000 and 600 F), respectively

An adverse effect of film cooling on the suction surface of a turbine vane

Film-cooling-air ejection from the suction surface of a turbine vane was investigated. This investigation was conducted in a four-vane cascade on a J75 size turbine vane which had a row of holes near the leading edge. The experimental data are presented. It was found that a small amount of film-cooling air has a detrimental effect on the downstream vane wall cooling effectiveness. It was also shown that the presence of the film-cooling holes, without blowing, also cause an increase in vane wall temperatures. These results came from an increase in the gas-side heat transfer coefficient that was apparently caused by a laminar or transitional boundary layer becoming transitional or turbulent

Algorithm for calculating turbine cooling flow and the resulting decrease in turbine efficiency

An algorithm is presented for calculating both the quantity of compressor bleed flow required to cool the turbine and the decrease in turbine efficiency caused by the injection of cooling air into the gas stream. The algorithm, which is intended for an axial flow, air routine in a properly written thermodynamic cycle code. Ten different cooling configurations are available for each row of cooled airfoils in the turbine. Results from the algorithm are substantiated by comparison with flows predicted by major engine manufacturers for given bulk metal temperatures and given cooling configurations. A list of definitions for the terms in the subroutine is presented

Comparison of temperature data from an engine investigation for film-cooled and non-film-cooled, panwise-finned vanes incorporating impingement cooling

The experimental temperature characteristics of two spanwise-finned, impingement-cooled vanes, one with film cooling and one without film cooling, were investigated in a modified J-75 research turbojet engine. Values of maximum temperature, average temperature, and maximum chordwise temperature difference were compared for the two vanes at the midspan. An analytical redesign of the two vane configurations indicated that the maximum and average temperatures and the maximum chordwise temperature difference could be significantly lowered. The experimental tests indicated that suction-surface film cooling may cause increased heat transfer near the trailing edge of the vane

Interhemispheric survey of minor upper atmospheric constituents during October - November 1976

The CV-990 aircraft coordinated several flights with a NASA U-2 aircraft, NOAA ground station measurements in Alaska, Hawaii, and American Samoa, and with Australian and New Zealand ground stations, aircraft, and a balloon experiment in the Southern hemisphere. Data were obtained for species including ozone, total ozone, the oxides of nitrogen, the chlorofluoromethanes, water vapor, nitric acid, carbon monoxide, carbon dioxide, hydrogen chloride, Aitken nuclei, ammonia, aerosols, temperatures, and winds. Individual experiment results and selected analyses are presented. The experimental data include total column densities, latitude variations, interhemisphere differences, and vertical profiles

Film cooling on the pressure surface of a turbine vane

Film-cooling-air ejection from the pressure surface of a turbine vane was investigated, and experimental data are presented. This investigation was conducted in a four-vane cascade on a J75-size turbine vane that had a double row of staggered holes in line with the primary flow and located downstream of the leading edge region. The results showed that: (1) the average effectiveness of film-convection cooling was higher than that of either film cooling or convection cooling separately; (2) the addition of small quantities of film-cooling air always increased the cooling effectiveness relative to the zero-injection case; however, (3) the injected film must exceed a certain threshold value to obtain a beneficial effect of film cooling relative to convection cooling alone

Crossflow effects on impingement cooling of a turbine vane

An air-cooled turbine vane was tested in a four-vane cascade. Heat transfer characteristics of the impingement cooled midchord region are reported. Experimental Nusselt numbers of six midchord locations are examined for the effect of crossflow and compared to those predicted by impingement correlations found in the literature