Prediction of Compressible Flow Pressure Losses in 30–150 Deg Sharp-Cornered Bends

1995 ◽  
Vol 117 (4) ◽  
pp. 589-592 ◽  
Author(s):  
Nia Haidar
Keyword(s):  
Compressible Flow ◽  
Turbine Engines ◽  
Air Cooling ◽  
Gas Turbine Engines ◽  
Pressure Losses ◽  
Flow Pressure ◽  
Secondary Air ◽  
Limiting Condition ◽  
Experimental Findings ◽  
Wide Speed Range

This paper considers the measurement and prediction of the additional total pressure losses of subsonic steady air flow in sharp-cornered bends, similar to those present in the secondary air cooling systems of gas turbine engines. The bends examined ranged between 30 to 150 in 30 deg increments and were circular in cross section. Experimental results covering a wide speed range up to choking are presented for five different bend geometries. An analytical flow model provided results in fairly good agreement with the measurements obtained and equally compared favourably with the experimental findings of other researchers at low Mach numbers. The highest attainable upstream Mach number (MU) of the average upstream flow was 0.57 for the 30 deg bend. The maximum possible values of MU represent a limiting condition dictated by downstream choking of the flow. The compressible flow coefficients, caused by the presence of the bends, can be expected to be between 10 to 20 percent higher than those for incompressible flow.

scholarly journals Compressible Flow Pressure Losses in Wye-Junctions

1992 ◽  
Author(s):  
N. I. Abou-Haidar ◽  
S. L. Dixon
Keyword(s):  
Mach Number ◽  
Compressible Flow ◽  
Incompressible Flows ◽  
Separate Flow ◽  
Working Fluid ◽  
Flow Visualisation ◽  
Vena Contracta ◽  
Pressure Losses ◽  
Flow Pressure ◽  
Limiting Condition

This paper considers the compressible flow pressure losses in sharp cornered wye-junctions with symmetrical branches under dividing and combining flow conditions. Determination of the additional total pressure losses occurring in flow through several three-leg junctions, using dry air as the working fluid, has been made experimentally. Results covering a wide speed range up to choking are presented for three different wye-junction geometries. Separate flow visualisation Schlieren tests detected the presence of normal shock waves, located at up to one duct diameter downstream of the junction, and therefore confirmed the choking of the flow at the vena contracta. The highest attainable Mach number (M3) of the averaged whole flow was 0.9 for one of the dividing flow geometries and 0.65 for several of the combining flow cases. These values of M3 were the maximum possible and hence represent a limiting condition dictated by choking. In general, the compressible flow loss coefficients, caused by the presence of the wye-junctions, can be expected to be higher for dividing flows and lower for combining flows than would be the case for incompressible flows because of the influence of Mach number (M3) on the magnitude of the denominator.

Measurement of Compressible Flow Pressure Losses in Wye-Junctions

1994 ◽  
Vol 116 (3) ◽  
pp. 535-541 ◽  
Author(s):  
N. I. Abou-Haidar ◽  
S. L. Dixon
Keyword(s):  
Mach Number ◽  
Compressible Flow ◽  
Incompressible Flows ◽  
Separate Flow ◽  
Working Fluid ◽  
Vena Contracta ◽  
Pressure Losses ◽  
Flow Loss ◽  
Flow Pressure ◽  
Limiting Condition

This paper considers the compressible flow pressure losses in sharp-cornered wye-junctions with symmetric branches under dividing and combining flow conditions. Determination of the additional total pressure losses occurring in flow through several three-leg junctions, using dry air as the working fluid, has been made experimentally. Results covering a wide speed range up to choking are presented for 30, 60, and 90 deg wye-junctions. Separate flow visualization schlieren tests detected the presence of normal shock waves, located at up to one duct diameter downstream of the junction, and therefore confirmed the choking of the flow at the vena contracta. The highest attainable Mach number (M3) of the averaged whole flow was 0.9 for one of the dividing flow geometries and 0.65 for several of the combining flow cases. These values of M3 were the maximum possible and hence represent a limiting condition dictated by choking. In general, the compressible flow loss coefficients, caused by the presence of the wye-junctions, can be expected to be higher for dividing flows and lower for combining flows than would be the case for incompressible flows because of the influence of Mach number, M3.

Thermodynamic Performance of Complex Gas Turbine Cycles

2002 ◽  
Author(s):  
Sanjay ◽  
Onkar Singh ◽  
B. N. Prasad
Keyword(s):  
Gas Turbine ◽  
Specific Power ◽  
Turbine Engines ◽  
Inlet Temperature ◽  
Air Cooling ◽  
Gas Turbine Engines ◽  
Current State ◽  
Thermodynamic Performance ◽  
Internal Convection ◽  
Plant Efficiency

This paper deals with the thermodynamic performance of complex gas turbine cycles involving inter-cooling, re-heating and regeneration. The performance has been evaluated based on the mathematical modeling of various elements of gas turbine for the real situation. The fuel selected happens to be natural gas and the internal convection / film / transpiration air cooling of turbine bladings have been assumed. The analysis has been applied to the current state-of-the-art gas turbine technology and cycle parameters in four classes: Large industrial, Medium industrial, Aero-derivative and Small industrial. The results conform with the performance of actual gas turbine engines. It has been observed that the plant efficiency is higher at lower inter-cooling (surface), reheating and regeneration yields much higher efficiency and specific power as compared to simple cycle. There exists an optimum overall compression ratio and turbine inlet temperature in all types of complex configuration. The advanced turbine blade materials and coating withstand high blade temperature, yields higher efficiency as compared to lower blade temperature materials.

Relative Cooling: Part II — Design Considerations and Efficiency

2001 ◽  
Author(s):  
Sandu Constantin ◽  
Dan Brasoveanu
Keyword(s):  
Gas Turbine ◽  
Thermal Efficiency ◽  
Cooling System ◽  
High Reliability ◽  
Difficult Problem ◽  
Turbine Engines ◽  
Air Cooling ◽  
Gas Turbine Engines ◽  
Coolant Pump ◽  
Cooling Systems

Abstract Cooling systems with liquid for gas turbine engines that use the relative motion of the engine stator with respect to the rotor for actuating the coolant pump can be encapsulated within the engine rotor. In this manner, the difficult problem of sealing stator/rotor interfaces at high temperature, pressure and relative velocity is circumvented. A first generation of such cooling systems could be manufactured using existing technologies and would boost the thermal efficiency of gas turbine engines by more than 2% compared to recent designs that use advanced air-cooling methods. Later, relative cooling systems could increase the thermal efficiency of gas turbine engines by 8%–11% by boosting the temperatures at turbine inlet to stoichiometric levels and recovering most of the heat extracted from turbine during cooling. The appreciated high reliability of this cooling system will allow widespread use for aerospace propulsion.

Using a Tracer Gas to Quantify Sealing Effectiveness for Engine Realistic Rim Seals

2016 ◽  
Author(s):  
Kenneth Clark ◽  
Michael Barringer ◽  
Karen Thole ◽  
Carey Clum ◽  
Paul Hiester ◽  
...  
Keyword(s):  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Tracer Gas ◽  
Engine Efficiency ◽  
Hot Gas ◽  
Area Of Interest ◽  
Sensitivity Studies ◽  
Secondary Air ◽  
Effective Use ◽  
Validation Experiments

As overall pressure ratios increase in gas turbine engines, both the main gas path and cooling temperatures increase leading to component durability concerns. At the same time effective use of the secondary air for both cooling and sealing becomes increasingly important in terms of engine efficiency. To fully optimize these competing requirements, experiments at engine-relevant conditions are required to validate new designs and computational tools. A test turbine has been commissioned in the Steady Thermal Aero Research Turbine (START) lab. The test turbine was designed to be a 1.5 stage turbine operating under continuous flow simulating engine-relevant conditions including Reynolds and Mach numbers with hardware true to engine scale. The first phase of research conducted using the test turbine, which was configured for a half-stage (vane only), was to study hot gas ingestion through turbine rim seals. This paper presents a series of facility benchmarks as well as validation experiments conducted to study ingestion using a tracer gas to quantify the performance of rim seals and purge flows. Sensitivity studies included concentration levels and sampling flow rates in flow regimes that ranged from stagnant to compressible depending upon the area of interest. The sensitivity studies included a range of purge and leakage flow conditions for several locations in the rim seal and cavity areas. Results indicate reasonable sampling methods were used to achieve isokinetic sampling conditions.

scholarly journals Experimental Deposition of NaCl Particles From Turbulent Flows at Gas Turbine Temperatures

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
Peter R. Forsyth ◽  
David R. H. Gillespie ◽  
Matthew McGilvray
Keyword(s):  
Gas Turbine ◽  
Turbulent Flows ◽  
Size Range ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Horizontal Pipe ◽  
Experimental Campaign ◽  
System Temperature ◽  
Secondary Air

The ingestion and deposition of solid particulates within gas turbine engines has become a very significant concern for both designers and operators in recent times. Frequently aircraft are operated in environments where sand, ash, dust, and salt are present, which can drive damage mechanisms from long term component degradation to in-flight flame-out. Experiments are presented to assess deposition characteristics of sodium chloride (NaCl) at gas turbine secondary air system temperature conditions in horizontal pipe flow. Monodisperse NaCl particles were generated in the size range 2.0–6.5 µm, with gas temperatures 390–480 °C, and metal temperatures 355–730 °C. Two engine-representative surface roughnesses were assessed. An experimental technique for the measurement of deposited NaCl based on solution conductivity was developed and validated. Experiments were carried out under isothermal and nonisothermal/thermophoretic conditions. An initial experimental campaign was conducted under ambient and isothermal conditions; high temperature isothermal results showed good similarity. Under thermophoretic conditions, deposition rates varied by up to several orders of magnitude compared to isothermal rates.

Effects of Purge Jet Momentum on Sealing Effectiveness

2016 ◽  
Author(s):  
Kenneth Clark ◽  
Michael Barringer ◽  
Karen Thole ◽  
Carey Clum ◽  
Paul Hiester ◽  
...  
Keyword(s):  
Flow Rate ◽  
Momentum Flux ◽  
Reynolds Numbers ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Swirl Velocity ◽  
Purge Flow ◽  
Secondary Air ◽  
Flow Tracer ◽  
Mach And Reynolds Numbers

Driven by the need for higher cycle efficiencies, overall pressure ratios for gas turbine engines continue to be pushed higher thereby resulting in increasing gas temperatures. Secondary air, bled from the compressor, is used to cool turbine components and seal the cavities between stages from the hot main gas path. This paper compares a range of purge flows and two different purge hole configurations for introducing the purge flow into the rim cavities. In addition, the mate face gap leakage between vanes is investigated. For this particular study, stationary vanes at engine relevant Mach and Reynolds numbers were used with a static rim seal and rim cavity to remove rotational effects and isolate gas path effects. Sealing effectiveness measurements, deduced from the use of CO2 as a flow tracer, indicate that the effectiveness levels on the stator and rotor side of the cavity depend on the mass and momentum flux ratios of the purge jets relative to the swirl velocity. For a given purge flow rate, fewer purge holes resulted in better sealing than the case with a larger number of holes.

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