Effect of solid fuel characteristics on operating conditions of low-temperature gas generator for high-speed flying vehicle

Realistic compressor maps are the key to high quality gas turbine performance calculations. When modeling the performance of an existing engine then these maps are usually not known and must be approximated by adapting maps from literature to either measured data or to other available information. There are many publications describing map adaptation processes, simple ones and more sophisticated physically based scaling rules. There are also reports about using statistics, genetic algorithms, neural networks and even morphing techniques for re-engineering compressor maps. This type of methods does not consider the laws of physics and consequently the generated maps are valid at best in the region in which they have been calibrated. This region is frequently very narrow, especially in case of gas generator compressors which run in steady state always on a single operating line. This paper describes which physical phenomena influence the shape of speed and efficiency lines in compressor maps. For machines operating at comparatively low speeds (so that the flow into each stage is subsonic), there is usually considerable range between choke and stall corrected flow. As the speed of the machine is increased the range narrows. For high-speed stages with supersonic relative flow into the rotor the efficiency maximum is where the speed line turns over from vertical to lower than maximum corrected flow. At this operating condition the shock is about to detach from the leading edge of the blades. The flow at a certain speed can also be limited by choking in the compressor exit guide vanes. For high pressure ratio single stage centrifugal compressors this is a normal case, but it can also happen with low pressure ratio multistage boosters of turbofan engines, for example. If the compressor chokes at the exit, then the specific work remains constant along the speed line while the overall pressure ratio varies and that generates a very specific shape of the efficiency contour lines in the map. Also in other parts of the map, the efficiency varies along speed lines in a systematic manner. Peculiar shapes of specific work and corrected torque lines can reveal physically impossibilities that are difficult to see in the standard compressor map pictures. Compressor maps generated without considering the inherent physical phenomena can easily result in misleading performance calculations if used at operating conditions outside of the region where they have been calibrated. Whatever map adaptation method is used: the maps created in such a way should be checked thoroughly for violations of the underlying laws of compressor physics.

Download Full-text

Feasibility of Gas Bearings for Small High-Performance Aircraft Gas Turbines

ASME 1969 Gas Turbine Conference and Products Show ◽

10.1115/69-gt-60 ◽

1969 ◽

Author(s):

P. W. Curwen

Keyword(s):

Gas Turbines ◽

High Speed ◽

High Performance ◽

High Stress ◽

Construction Materials ◽

Operating Conditions ◽

System Stability ◽

Gas Generator ◽

Gas Bearings ◽

Thrust Bearings

High temperatures, pressures, and speeds of future Army propulsion systems will impose severe, perhaps intolerable, operating requirements on oil-lubricated engine bearings. Accordingly, air-lubricated (gas) bearings are being investigated as a possible approach to alleviating the lubrication problems. This paper presents results of a study to apply gas bearings to a two-spool gas generator for an advanced 4.5-lb/sec engine. It is shown that gas-lubricated journal and thrust bearings can be designed to carry the maximum loads imposed by flight and landing conditions. Additionally, the resulting engine configuration has promising attributes of compactness and mechanical simplicity. Potential problem areas are identified to be rotor-bearing system stability, LP-spool balancing, and LP-spool seal leakage. One area where feasibility has not been established is durability of the bearing construction materials. Material testing at the high-temperature, high-stress operating conditions of the bearings, including the effects of momentary high-speed bearing contacts, is urgently needed so that the question of material feasibility can be critically assessed.

Download Full-text

A Model of Solid-Fuel Gasification in the Combined Charge of a Low-Temperature Gas Generator of a Flying Vehicle

Doklady Physics ◽

10.1134/s1028335818090057 ◽

2018 ◽

Vol 63 (9) ◽

pp. 375-379 ◽

Cited By ~ 3

Author(s):

V. A. Levin ◽

N. A. Lutsenko ◽

E. A. Salgansky ◽

L. S. Yanovskiy

Keyword(s):

Low Temperature ◽

Solid Fuel ◽

Gas Generator

Download Full-text

ALMAR 20

Alloy Digest ◽

10.31399/asm.ad.sa0162 ◽

1964 ◽

Vol 13 (4) ◽

Keyword(s):

Corrosion Resistance ◽

Low Temperature ◽

Solid Fuel ◽

Precipitation Hardening ◽

Martensitic Steel ◽

Heat Treating ◽

Aircraft Landing ◽

Temperature Performance ◽

Aircraft Landing Gear ◽

High Nickel

Abstract ALMAR 20 is a high nickel martensitic steel which is strengthened by precipitation hardening. It has excellent combination of strength and toughness particularly in the presence of notches and cracks. It is recommended for applications such as solid fuel rocket cases and aircraft landing gear. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on low temperature performance and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SA-162. Producer or source: Allegheny Ludlum Corporation.

Download Full-text

Low-temperature f.e.t. for low-power high-speed logic

Electronics Letters ◽

10.1049/el:19770111 ◽

1977 ◽

Vol 13 (6) ◽

pp. 156 ◽

Cited By ~ 15

Author(s):

H. Rees ◽

G.S. Sanghera ◽

R.A. Warriner

Keyword(s):

Low Temperature ◽

Low Power ◽

High Speed

Download Full-text

Research on Performance Test System of Space Harmonic Reducer in High Vacuum and Low Temperature Environment

Machines ◽

10.3390/machines9010001 ◽

2020 ◽

Vol 9 (1) ◽

pp. 1

Author(s):

Jing Wang ◽

Zhihua Wan ◽

Zhurong Dong ◽

Zhengguo Li

Keyword(s):

Low Temperature ◽

High Speed ◽

Performance Test ◽

High Reliability ◽

High Vacuum ◽

Test System ◽

Low Noise ◽

Speed Ratio ◽

Space Harmonic ◽

Temperature Environment

The harmonic reducer, with its advantages of high precision, low noise, light weight, and high speed ratio, has been widely used in aerospace solar wing deployment mechanisms, antenna pointing mechanisms, robot joints, and other precision transmission fields. Accurately predicting the performance of the harmonic reducer under various application conditions is of great significance to the high reliability and long life of the harmonic reducer. In this paper, a set of automatic harmonic reducer performance test systems is designed. By using the CANOpen bus interface to control the servo motor as the drive motor, through accurately controlling the motor speed and rotation angle, collecting the angle, torque, and current in real time, the life cycle test of space harmonic reducer was carried out in high vacuum and low temperature environment on the ground. Then, the collected data were automatically analyzed and calculated. The test data of the transmission accuracy, backlash, and transmission efficiency of the space harmonic reducer were obtained. It is proven by experiments that the performance data of the harmonic reducer in space work can be more accurately obtained by using the test system mentioned in this paper, which is convenient for further research on related lubricating materials.

Download Full-text