4. Analysis programs.These include aerothermal and mechanical ana-lysis programs， with diagnostics and optimization programs.
a. Aero-thermal analysis: Typical aero-thermal performance calcula-tions involve the evaluation of component unit power， polytropicand adiabatic head， pressureratio， temperatureratio， polytropicand adiabatic efficiencies， temperature profiles， and a host of other machine specific conditions under steady state as well as during transients.startups and shutdowns. This program must be tai-lored to individual machinery and to the instrumentation avail-able. Data must be corrected to a base condition， so that it can be compared and trended. The base condition can vary from IS.ambient conditions， to design conditions of a compressor or pump if those conditions are very different from IS. ambient conditions.To analyze off-design operation， it is necessary to transpose values from the operating points back to the design point for comparison of unit degradation.
b. Mechanical analysis: This program must be tailored to the mechan-ical properties of the machine train under consideration. It shouldinclude bearing analysis， seal analysis， lubrication analysis， rotordynamics， and vibration analysis. This includes the evaluation andcorrelation of bearing metal temperatures， shaft orbits， vibration
velocity， spectrum snapshots， waterfall plots， stress analysis， and material properties.
c. Diagnostic analysis: This program can be part of an expert systemor consist of an operational matrix， which can point to various problems. The program must include comparison of both perfor-mance and mechanical health parameters to a machine specific fault matrix to identify if a fault exists. Expert analysis modules can in many cases aid to faster fault identification but are usually more difficult to integrate into the system.
d. .ptimi.ation analysis: .ptimization programs take into accountmany variables， suchas， deterioration rate; overhaul costs， interest， and utilization rates. These programs may also be dependent on more than one machine train if the process is interrelated between various trains.
e. Li e cycle analysis: The determination of the effect of the material， the temperatureexcursions， the number of startups and shutdowns， and the type of fuel all relate to the life of hot section components.
5. .istorical data management.This includes the data acquisition and storage capabilities. Present-day prices of storage mediums have beendroppingrapidly， and systems with 80 gigabyte hard disks are avail-able. These disks could store a minimum of five years of one-minute data for most plants. .ne-minute data is adequate for most steadystate operation， while start-ups and shutdowns or other non steady state operation should be monitored and stored at an interval of onesecond. To achieve these time rates， data for steady state operation canbe obtained from most plant-wide D-CS systems， and for unsteadystate conditions， data can be obtained from control systems.
Implementation of a Condition .onitoringSystem
The implementation of a condition monitoring system in a major utilities plant requires a great deal of forethought. A major utilities plant will havea number of varied， large rotating equipment. This will consist usually ofvarious types of prime movers such as large gas turbines， steamturbines，compressors，pumps， electric generators， and motors. The following are someof the majorsteps， which need to be taken to ensure a successful system installation:
1. The first decision is to decide on what equipment should be monitored on line and what systems should be monitored off-line. This requires
an assessment of the equipment in terms of both first cost and oper-ating costs， redundancy， reliability， efficiency， and criticality.
2. .btain all pertinent data of the equipment to be monitored. This would include details of the mechanical design and the performance design. Some of this information may be difficult to obtain from the manufacturer and will have to be calculated from data being obtained in the field or after installation during commissioning tests in a new installation. .btaining baseline data is critical in the installation of any condition monitoring system.In most systems， it is the rate of change of parameters that are being trended not the absolute values of these points. It is also important to decide what type of alarms will be attached to the various points. .ate of change alarms must be for bearing metal temperatures especially for thrust bearings where temperature changes are critical. Prognostic alarms should be applied to critical points. Alarms randomly applied tend to slow down the system and do not provide added protection. The following are some of the basic data that would be necessary in setting up a system: 中國航空網 m.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：燃氣渦輪工程手冊 Gas Turbine Engineering Handbook 3(43)
