Enhancement of Efficiency and Environmental Friendliness of Driving Gas Turbines by Integrating of Existing Turbomachine and High Temperature Ceramic Overstructure

Abstract

Gas turbine engines have been widely applied to pipeline systems to drive pumping equipment (gas compressors, oil pumps, etc) and electric generators. Thus, there are over 4000 units involved into the gas industry operation in Russia. Nearly 90% of machines of around 60 models are running as gas pumping units. E.g. eight types of gas turbine engines of power ranging 1 500 to 4 300 KW are operated at the electric stations to supply electric power for gas pipeline’s own needs (ONS). The bulk (over 30%) of the standard units were designed during the 60s of the past century and, therefore, their efficiency is rather low (23–28%) with the running time mounting to 60 000–80 000 hours. A good number of the existing units do not meet the international norms in terms of admissible toxic emissions (NOx, CO, etc). At the same time, the state of the basic hardware (casing, rotors, bearings, combustors, heat exchangers, etc) is, in fact, not bad, i.e. all these devices and systems could operate for, at least, 100 thousand hours more. This is an industrially well matured and thoroughly mastered, reparable and relatively inexpensive equipment. Therefore, it is of a real practical interest to implement an upgrade of the “old” machines which would allow provision of both using the existing hardware under standard operating conditions and their efficiency increasing (by 6–10% abs) and the NOx emissions reduction (up to 12.5–37.5 ppm) and CO emissions (up to 50 ppm). The like upgrade could be put into effect on the basis of integration of the existing turbomachines of gas pumping units or ONS and the ceramic overstructure — a high pressure unit. The Research–Engineering “Ceramic Heat Engines” Center (NIZ KTD) jointly with the JSC “Proletarsky Works” (St. Petersburg) has developed an ONS gas turbine drive on the base of the 1.5 MW gas turbine engine with a high temperature ceramic overstructure made as a high pressure turbocompressor with a lox-toxic combustor installed between its compressor and turbine. As a result of such modification, a pilot GTE was produced with the initial gas temperature of 1050°C instead of 827°C but of the same power and with the efficiency of 28% instead of 22%, the NOx emissions being 12.5 ppm instead of 50 ppm. The main design modifications of the base-line engine first and foremost were linked with the standard compressor (4 last stages are envisaged to be removed) and the combustor. The independent high pressure unit, at the same time, must be designed and manufactured anew. Given an effective small-size ceramic airheater is applied, you can increase its initial gas temperature (up to 1350°C with the GTE efficiency increased up to 42–47%.