Thermal efficiency of the regenerative cycle of the Stirling engine scheme gamma

The paper presents a theoretical model of the Stirling engine-gamma scheme, based on thermodynamic dependencies describing the working process taking into account the efficiency of the regenerator. The measurement of the gas pressure in the cycle, due to which its operation was carried out, is carried out by means of a plunger moving along the cylinder. Cooling in the working cylinder circuit is carried out at the expense of the environment. Due to the movement of the working fluid between the cylinders, there is an increase or decrease in pressure, which requires energy costs that affect the operation of the engine. An increase in the energy efficiency of the Stirling engine is achieved by introducing a regenerator into it, which helps to minimize heat losses. This device is located between the hot and cold cylinder, it is a cavity that contains a porous material that receives heat flowing with hot gas into the cold area, when it is moved back before entering the heater, the regenerator returns the stored heat. Due to the introduction of the regenerator in the model, the engine increases energy efficiency, and the efficiency of its cycle reaches the efficiency of the Carnot cycle. In this paper, the authors apply thermodynamic laws to represent the processes that underlie the functioning of the Stirling machine, not only in its cylinders, but also in the battery, the analysis of thermal inertia of which confirms the above study.

Thermal performance comparison of Rankine cycle, reheat cycle and regenerative cycle with the same initial and final parameters

The conversion between thermal energy and mechanical energy can be realized through the thermal cycle of working medium in a series of power plants. For the thermodynamic analysis of the thermal cycle, it mainly analyzes the thermal efficiency and steam consumption rate of the cycle to analyze the main factors affecting the thermal efficiency of the cycle, and the measures to improve the thermal efficiency, in order to reduce the fuel consumption and reduce the power generation cost.

Synthetic connectivity, emergence, and self-regeneration in the network of prebiotic chemistry

The challenge of prebiotic chemistry is to trace the syntheses of life’s key building blocks from a handful of primordial substrates. Here we report a forward-synthesis algorithm that generates a full network of prebiotic chemical reactions accessible from these substrates under generally accepted conditions. This network contains both reported and previously unidentified routes to biotic targets, as well as plausible syntheses of abiotic molecules. It also exhibits three forms of nontrivial chemical emergence, as the molecules within the network can act as catalysts of downstream reaction types; form functional chemical systems, including self-regenerating cycles; and produce surfactants relevant to primitive forms of biological compartmentalization. To support these claims, computer-predicted, prebiotic syntheses of several biotic molecules as well as a multistep, self-regenerative cycle of iminodiacetic acid were validated by experiment.

Use of LNG Cold Potential in the Cogeneration Cycle of Ship Power Plants

This paper presents the results of a numerical study on the parameters that affect the efficiency of the cogeneration cycle of a ship’s power plant. The efficiency was assessed based on the excess power (Ngen.) of a free turbine, operated with the inflow of gaseous nitrogen, which was used to generate electricity. A mathematical model and simulation of the regenerative cycle were created and adjusted to operate with a dual-fuel (diesel-liquid natural gas (LNG)) six-cylinder four-stroke engine, where the energy of the exhaust gas was converted into mechanical work of the regenerative cycle turbine. The most significant factors for Ngen. were identified by parametrical analysis of the cogeneration cycle: in the presence of an ‘external’ unlimited cold potential of the LNG, Ngen. determines an exhaust gas temperature Teg of power plant; the pressure of the turbo unit and nitrogen flow are directly proportional to Ngen. When selecting the technological units for cycle realization, it is rational to use high flow and average πT pressure (~3.0–3.5 units) turbo unit with a high adiabatic efficiency turbine. The effect of the selected heat exchangers with an efficiency of 0.9–1.0 on Ngen. did not exceed 10%. With LNG for ‘internal’ use in a ship as a fuel, the lowest possible temperature of N2 is necessary, because each 10 K increment in N2 entering the compressor decreases Ngen. by 5–8 kW, i.e., 5–6%.

DEGREE OF REGENERATION OPTIMIZATION FOR CYCLES OF MICROGAS TURBINE PLANTS

A consideration subject in article is the mathematical model of pressure recovery factor of microgas turbine plants (MGTP) regenerators which considers dependence of hydraulic resistance of the heat–exchanger on the its surface area. Optimization of a regenerative cycle of MGTP and a cycle with regeneration and the turbocompressor utilizer for the purpose of further increase in their profitability is performed. It is established that use of the offered model of pressure recovery factor on the air and gas side allows to find degree of regeneration heattechnical optimum. This model can be used at simplified and predesign of MGTP.

MATHEMATICAL MODELING OF THE PROCESS OF LOW TEMPERATURE DRYING IN THE INSTALLATION WITH REGENERATIVE CYCLE

Рассмотрено применение в установках низкотемпературной сушки (УНТС) с регенеративным циклом компрессорных термотрансформаторов (тепловых насосов). На основании выбранной модели выполнено математическое моделирование процессов в виде системы уравнений. Получены аналитические расчеты зависимости тепломассообменных процессов. Установлено, что в интервале изменений параметров работы сушильной установки более эффективной является УНТС с расположением регенеративного теплообменника до конденсатора. The application of compressor thermotransformers (heat pumps) in installations of low temperature drying (LTD) plants is considered. Considerable attention is paid to LTD with regenerative cycle. On the basis of the selected model, mathematical modeling of processes in the form of a system of equations, the solution of which allowed obtain analytical calculations of the dependence of heat and mass transfer processes was received. It was found that in the range of parameters of the drying plant LTD with the location of the regenerative heat exchanger to the condenser is more effective.

The Use of Air Turbine Heat Recovery Units for the Mod-ernization of Gas Pumping Units with Gas Turbine Drive

One of the urgent tasks of further developing natural gas transportation systems is the need to increase fuel efficiency and to improve environmental performance of the gas turbine units (GTU) that are used to drive superchargers of gas pumping units. Outdated GTUs with low efficiency are being replaced by units of a new generation, including those of the regenerative cycle. However, this requires significant capital expenditures, thus, the possibilities of upgrading the existing units are also being investigated. A significant proportion of the energy generated by the gas combusted in driven GTUs is lost in the form of heat of the exhaust combustion products. These gases have a temperature not lower than 670 K. To utilize the heat of the exhaust combustion products, it is proposed to compliment the main GTU by an air turbine heat recovery unit (ATU) that is simple in design and inexpensive in production. This well-known idea has not yet been realized in practice, thus there are no recommendations on the use of a GTU-ATU as a drive for natural gas superchargers. It is shown that to ensure the possibility of upgrading drive gas turbines at a minimum cost, it is advisable to use an ATU that is kinematically independent of the GTU. The ATU’s power is used to cover the own needs of the compressor station and other purposes. The calculations show that under equal conditions, the combined GTU-ATU is inferior in efficiency to the GTU of the regenerative cycle. However, it provides a much smoother flow of the efficiency parameter depending on the operation mode, which is important for gas pumping units. The potential of using the ATU for the modernization of drive GTUs is estimated. It is noted that in addition to generating additional power, the use of ATU’s can decrease the flue gas temperature and the mass concentration of harmful emissions.