BACKGROUND: Modern micro gas turbine units (MGTUs) with the power of dozen of kilowatts are single-shaft and recuperative. Being in the position where improvement of new MGTU cycles is being studied, it is necessary to choose optimal parameters of the MGTU cycle according to the scheme with regeneration when developing such simple units with the aim of ensuring small size and efficiency. Nevertheless, there are several practical restrictions for the development of recuperators, related to the issue of complicated designs together with pressure losses increase caused by regeneration degree increase and to the restriction of materials quality. AIMS: Study of influence of a recuperator on efficiency of the MGTU, as it is essential for the development of MGTUs. METHODS: As a part of the study, the overall assessment of the influence of recuperators on parameters of an ordinary Brayton cycle with recuperation is presented in the article. The influence of main parameters, including degree of pressure increase in a compressor, inlet gas temperature and regeneration degree, on MGTU efficiency is considered in depth in the article. RESULTS: According to the study results, it is revealed that the use of the regeneration degree of over 0,9 with low coefficient of pressure losses in recuperators for the development of modern recuperative MGTUs leads to the unit effective efficiency not exceeding 3840% because of certain restrictions of gas temperature at the MGTU turbine inlet caused by difficulties with cooling and ensuring small size and efficiency of the unit. CONCLUSIONS: Use of new heatproof materials is to become an important part of improvement of MGTU in future, therefore it is necessary to study new technical solution when using prospective materials of recuperators for choosing optimal parameters of the MGTU cycle with regeneration. In addition, the option of using bimetallic recuperators is considered.

BACKGROUND: Gas turbine units (GTU) are widely used in power plants, shipbuilding, aerospace and other industry sectors. Main performance indicators of units are effective cycle efficiency and useful internal power. It is known that gas turbine power grows on 1525% for each 100C of turbine inlet temperature increases in range of 10001400 K, which makes it possible to save fuel significantly. Further growth of turbine inlet temperature demands more drastic increase of cooling air flow rate for the sake of cooling of the GTU flow channel, that leads to decrease of effective efficiency of a GTU. Consequently, the research of cooling and heat capacity properties influence needs to be done in order to improve gas turbine unit performance in the turbine inlet temperature range of 10001400 K. AIMS: Issues of influence of cooling of high temperature GTUs as well as issues of influence of working substance specific heat capacity dependence on temperature are studied in the article. METHODS: The study contains comparative analysis of four gas turbine units (GTU) such as: the 3,13 MW Teeda GTU (Iran), the 4,13 MW UEC Perm Engines GTU-4P (Russia), the 5,1 MW Siemens SGT-100 (Germany) and the 5,67 MW Solar Turbines TAURUS 60 (USA). RESULTS: As a result, dependencies of efficiency, specific effective work and GTU useful work coefficient on cooling were obtained. Working substance specific heat capacity dependence on temperature was considered in order to increase accuracy of calculations. CONCLUSIONS: The completed calculation study allows judging on perfection of the heat layout of GTU, the flow channel of GTU and making a comparison of them for the sake of further optimization of operational processes.

The article is dedicated to the study of the feasibility of increasing the efficiency, reliability and manufacturability of existing gas turbine power plants with additive technologies that allow creating recuperators with regeneration degrees of 90...95%. The characteristics are presented for the following gas turbine power plants: TEEDA (Iran) 3.13 MW, ODK Perm Motors GTU-4P (Russia) 4.13 MW, Siemens SGT-100 (Germany) 5.1 MW, Solar Turbines Taurus 60 (USA) 5.67 MW. The research was carried out using the methods and programs of the Higher School of Power Engineering for the calculation of thermal circuits of GTPP. The dependences of effective efficiency, work ratio, effective specific work and specific consumption of conventional fuel of GTPPs under examination on compressor pressure ratio and regeneration factor are obtained. Solving the problem of increasing the regeneration factor in GTPP (above 0.9) requires the development of special designs of heat exchanger matrices of the recuperator, which is only possible with the use of additive technologies and new heat-resistant materials. Promising recuperators have a more complex design of heat exchange matrices, which ensures their being very compact. Such technical solutions can ensure the development and creation of fundamentally new designs of GTPP heat exchangers and significantly improve their technical characteristics.