Blade Vibration on Centrifugal Compressors: Fundamental Considerations and Initial Measurements

Blade vibration has to be considered in the design of high pressure ratio / high mass flow centrifugal compressors with increasing rotational speed values due to the reduced blade thickness. Results of a theoretical and experimental investigation concerning this problem are described. FE calculations of the stress distribution on the blade for the lower natural frequencies and various vibration tests at rest were carried out to investigate resonance and damping effects. This preparatory work was aimed at determining blade vibration behavior and acquiring fundamental experience for measurements on compressors in operation. Results of blade vibration measurements on compressors with a vaneless diffuser carried out with semiconductor strain gages and an 8-channel telemetry system are presented for constant rotational speed and for constant throttle valve position, and indicate considerable blade excitation during stall effects. Simultaneous flow measurements complete the investigation to determine the causes of blade vibration. For example, investigations were made of the extent of blade resonance excitation due to non-uniformity of the flow downstream of the impeller or due to flow disturbances caused by carrier blades for bearings in the compressor inlet and simulated by spoilers.

Gas Turbine Heat Recovery Systems: Evaluation Criteria for the Unfired Systems

The design of a gas turbine exhaust heat recovery system (HRS) depends upon evaluating various parameters. Basically for an unfired heat recovery system the heat contained in the gas turbine exhaust is fixed and output is determined based on the system’s effectiveness. One of the design objectives is to maximize the output and thus maximize the effectiveness. However, increase in effectiveness will increase required heat transfer surface and thus the cost of the HRS. The increased cost (and benefits) must be evaluated to establish whether the higher effective system is economically justifiable. The evaluation criteria of a heat recovery system involves analysis of various design parameters. This paper presents the general design procedure, the effect of each parameter on the design and basic criteria used to develop the HRS design.

Vacuum Plasma Spray Turbine Bucket Coating Development

This paper describes the vacuum plasma spray (VPS) turbine bucket coating development work conducted by the General Electric Company, Gas Turbine Division. The potential for corrosion in gas turbine buckets is described, and examples of the different types of hot corrosion are shown. Development of the first VPS coating (PLASMAGUARD* GT-29) is discussed, and corrosion laboratory burner test and field test results are presented. Coating development work aimed at low-temperature hot-corrosion conditions is also summarized. Laboratory test results on a new PLASMAGUARD coating (GT-43) developed for low-temperature hot corrosion are presented. The new General Electric Gas Turbine Division VPS coating manufacturing facility used to apply these coatings is also described.

Oxidation Resistance of Gas Turbine Combustion Materials

The oxidation behavior of five different gas turbine combustor alloy materials has been characterized in both combustion burner rig environments and in flowing air. The alloys are compared in terms of resistance to weight loss, or thinning, and also in terms of resistance to subsurface internal attack. Burner rig exposures were performed at 1095°C (2000°F) for 100, 200 and 300 hours under combustion conditions involving an air to fuel ratio of about 50:1. Results are also presented for similar exposures where the burner rig air lines were unintentionally plugged-up, yielding a low air:fuel ratio and severe carbon deposition on the samples. In addition to the burner rig studies, results are presented for 1008 hour flowing-air oxidation exposures over the temperature range from 980°C (1800°F) to 1205°C (2200°F).

Directionally Solidified DS CM 247 LC—Optimized Mechanical Properties Resulting From Extensive γ′ Solutioning

Complete coarse γ′ and greater than 90% eutectic γ-γ′ solutioning, without incipient melting, is demonstrated for the DS CM 247 LC superalloy. This unusual capability for this advanced Ni-base turbine blade and vane material results in considerable mechanical properties enhancement, with the DS alloy capability being near to current single crystal superalloys in the 345–207 MPa, 871°C–982°C (50–30 ksi, 1600°F–1800°F) operating condition. Microstructural features are detailed correlating strength and alloy stability.

Design of a 465 MW Combined Cycle Cogeneration Plant

In June 1983 Power Systems Engineering, Inc. began engineering of a base loaded 465 MW (net) combined cycle cogeneration plant (Figure 1) designed to sell up to 1,150,000 lb/hr (145.0 kg/s) of steam to a chemical plant in Houston, Texas, and sell up to 550,000 kW of electric power to the local electric utility (Houston Lighting & Power). Power Systems designed the plant, specified and procured equipment, arranged $220 million of project financing, will manage the construction of the plant, and will operate the plant. Power Systems negotiated the long-term steam contract with the chemical company and the power contract with HL&P. In addition, Power Systems obtained all permits and contracted for a long-term fuel supply.

Strain Isolated Ceramic Coatings for Gas Turbine Engines

Plasma sprayed ceramic coatings are used in gas turbine engines to improve component temperature capability and cooling air efficiency. Strain isolated ceramic coatings offer improved coating life and increased insulating capability. A low modulus fiber metal strain isolator between ceramic and metal backing acts to reduce the stress on the ceramic during thermal cycling. Strain isolated coatings can tolerate greater ceramic thickness and broader operating conditions than nonstrain isolated coatings when subjected to thermal shock. Ceramic coatings are durable only within a narrow range of operating conditions. Coating designs should be based on real operating conditions for success. Thermal shock testing is useful for evaluating ceramic coatings if test and sample design are representative of the intended application.

A Low-Cost Undergraduate Test Rig for Heat Transfer in Turbine Blade Cooling

Although turbine blade cooling has consistently led to the use of higher turbine inlet temperatures leading to improved cycle efficiencies, very little of this technology has found its way into undergraduate laboratory work. The cost of modern blade heat transfer research rigs virtually rules out the possibility of introducing this topic in undergraduate teaching laboratories of Universities or Polytechnics in the UK operating within tight budgetary constraints. However, the underlying principles of blade cooling heat transfer may be demonstrated quite easily by using inlet temperatures about half those existing in the actual turbine and the paper describes the design and development of a low-cost blade cooling heat transfer rig. Test results obtained on the ‘model’ rig enable an appreciation of the problems encountered in turbine blade cooling to be made and may serve as a basis for the design and development of more complicated blade cooling systems.

Gas Turbine Retrofit With Modern Control Systems

The rapid advances in technology of control systems precipitated by the development of microprocessors has made retrofit of older type controls an attractive alternative for many gas turbine owners. High reliability, enhanced operator interface, and optimized maintenance planning are some of the tangible benefits that can accrue from these retrofits. The design and features of the new equipment are discussed, and some of the complexities of changing out control systems and their associated instrumentation in field units are reviewed.

Dynamic Analysis of Complex Composite Rotor Systems With Substructure Transfer Matrix Method

A substructure transfer matrix method for the dynamic analysis of multi-Rotor systems and complex composite systems is presented. When calculating, the rotor system should be decomposed into several single rotor shafts (substructures). Corresponding unknown external loads and deflections are applied to the separated surfaces, rigid support sections and ball joint sections respectively to replace the original connections. According to the connective and boundary conditions of the whole rotor system, a system of equations is established, from which the frequency equation results. The calculating formulas of vibration modes and of unbalanced response will be easily formed by linear combination method. All computations are performed with the transfer matrix method. This method is intelligible, readily programmed and much simpler than the current transfer matrix method and modal synthesis method.