Showing papers on "Thermal efficiency published in 1988"

The Application of Availability and Energy Balances to a Diesel Engine

Abstract: The maximum power that can be extracted from an engine operating at a given condition was determined by means of analyses based on the first and second laws of thermodynamics. These analyses were applied to a heavy-duty single-cylinder open-chamber diesel engine operated at constant speed. Over the range of operating conditions investigated, the second-law efficiency (ratio of brake power to maximum extractable power) of the engine, which increased with engine load, was found to vary from 22 to 50 percent. It was concluded that besides heat transfer, the combustion process was the most important source of irreversibility and accounted for 25 to 43 percent of the lost power.

Rankine-diesel integrated system

Abstract: A system is provided for increasing the efficiency of internal combustion engines operating at high loads and more particularly to a multi-cylinder engine in which at least one cylinder is used as the power recovery device The waste heat generated during operation of the engine is utilized for producing an amount of energy to perform the work by means of a Rankine cycle

Direct-Contact Heat Transfer

Abstract: Direct-Contact Heat Transfer Processes.- Industrial Practices and Needs.- Computational Techniques for Two-Phase Flow and Heat Transfer.- Industrial Practices and Two-Phase Transport.- Mass Transfer Effects in Heat Transfer Processes.- Liquid-Liquid Processes.- Discussion of Mass Transfer Effects and Liquid-Liquid Transport.- Solids Motion and Heat Transfer in Gas Fluidized Beds.- High-Temperature Solids-Gas Interactions.- Direct-Contact Heat Transfer in Solid-Gas Systems.- Direct-Contact Evaporation.- Direct-Contact Condensation.- Discussion of Direct Contact Condensation and Evaporation.- Research Needs in Direct-Contact Heat Exchange.

A Modified, High-Efficiency, Recuperated Gas-Turbine Cycle

Abstract: The thermal efficiency of an intercooled/recuperated cycle may be increased by: (a) evaporatively aftercooling the compressor discharge; and (b) injecting and evaporating an additional amount of water in the recuperator. Comparative computations of such a modified cycle and intercooled/recuperated cycles carried out over a wide range of pressure ratios and turbine inlet temperatures and at two different levels of component technologies show an advantage of over five percentage points in efficiency for the modified cycle. About 60 percent of this improvement results from modification (a) and 40 percent from modification (b). The modified intercooled/recuperated cycle is compared with nonintercooled steam-injected gas turbine systems at each component technology level. The present cycle is found to be superior by about 2.75 percentage points in efficiency and to require a substantially smaller water flow rate. To assist in interpreting those differences, the method of available-work analysis is introduced and applied. This is identical to exergy analysis for systems with a pure-substance working fluid, but differs from the latter for systems using a mixture of pure substances insofar as the thermodynamic dead state is defined for the chemical and phase composition realized at the exhaust conditions of practical engineering devices and systems. This analysismore » is applied to the heat-recovery processes in each of the three systems considered. It shows that the substantial, fundamental available-work loss incurred by mixing steam and gases in the steam-injected system is the main reason for the superior efficiency of the precent cycle.« less

Self-powered gas appliance

Abstract: Embodiments of gas-fired appliances which generate sufficient electricity to be self-powered include water heaters, space heaters, air conditioning units, and electric power and steam cogeneration systems. In such apparatus, gas is burned in a porous ceramic surface combustion burner. The high temperature surface of the burner includes a narrow band quantum emitting substance such as a rare earth metal oxide and preferably ytterbium oxide. Relatively shorter wavelength radiation from this quantum emitting surface illuminates photovoltaic cells having an absorption spectrum matched to the emission spectrum of the burner surface for generating sufficient electricity for powering the appliance. An infrared absorbing filter removes relatively longer wavelength radiation which would otherwise heat the photovoltaic cells. The cells are cooled, preferably by a portion of the utility fluid heated by the appliance. This enhances both the thermal efficiency of the appliance and the photovoltaic conversion efficiency of the cells.

Oxygen enriched combustion

Abstract: A process and apparatus for oxygen-rich combustion wherein a first portion of about 5 to about 40 percent of the total fuel to be cracked and combusted is introduced to a cracking chamber where it is combusted and cracked at a temperature below about 2200° C. to produce a cracked products mixture. Oxygen-rich gas of greater than about 30 volume percent oxygen is introduced to the cracking chamber in about 5 to about 50 percent of the stoichiometric requirement for complete combustion of the first portion of fuel introduced to that chamber. Cracked products mixture, a second remaining portion of fresh fuel and oxidizer having sufficient oxygen for substantially complete combustion of the combustible portion of the cracked products mixture and the fresh fuel is introduced to a combustion chamber wherein the combustible portion of the cracked products mixture and the fresh fuel is combusted. The process and apparatus provide a controllable, highly luminous, high temperature and high kinetic energy flame in the combustion chamber resulting in enhanced heat transfer rate to the furnace load, increased furnace specific production rate, increased furnace thermal efficiency, and reduced nitrogen oxides pollutant emissions.

Liquid‐sodium thermoacoustic engine

Abstract: We have constructed a thermoacoustic engine that uses liquid sodium as its working substance. The engine generates acoustic power using heat flowing from a high‐temperature source to a low‐temperature sink. The measured performance of this engine disagrees significantly with numerical calculations based on our theory of thermoacoustic engines. The efficiency of the engine is a substantial fraction of Carnot’s efficiency, and its power density is comparable to that of the conventional heat engines in widespread use. Thus we expect this type of engine to be of practical, economic importance.

Cogeneration by combining gas turbine engine with organic rankine cycle

Abstract: The gas turbine engine is known by its relatively low efficiency especially at part load. Therefore, to conserve energy and reduce the operating cost, waste heat is recovered by combining a heat-exchange gas turbine cycle with closed organic Rankine cycle. A computer programme was made to calculate parametrically the individual and combined cycle performances, namely the work and efficiency of each. The parameters considered were: gas turbine pressure ratio; maximum cycle temperature; fluid-air mass ratio; and type of working fluid. This analytical study shows that R113 is the optimum choice because it gives the smallest, hence the most economical, size of turbo-expander. Maximum cycle temperature and pressure ratio are relatively the most important parameters. Economic analysis indicates very good rate of return on investment, related with heat recovery by cogeneration.

Method and apparatus for heat carrier circulation for a vehicle heating system having a heater independent of the engine

Abstract: A heat carrier circulation for a vehicle heating system includes a heater independent of the engine. The heat carrier circulation contains a forward line which leads from the internal combustion vehicle drive engine to a heating system heat exchanger for the vehicle interior and which has a parallel branch in which the heater is disposed; and a return line leading from the heating system heat exchanger back to the internal combustion engine. The heat exchanger circulation contains a connection which goes from the return line to the part of the forward line located ahead of the heater. Installed in the heat carrier circulation is a settable valve which controls the ratio at which heat carrier flows to the heater from the connecting line and from the internal combustion engine.

Reformer for fuel cell

Abstract: PURPOSE:To provide the title reformer so designed that catalyst beds are arranged among heating beds and a plurality of heating means extending from the heating beds are inserted, in a dispersed manner, into the catalyst beds, thereby improving thermal efficiency and catalyst packing efficiency CONSTITUTION:A heating gas generated by a burner 2 rises dividedly up through respective heating beds 5a, 5b inside and outside the reaction vessel 3, making a heating while being put to parallel flow with the reaction gas flowing a catalyst bed 4, and is exhausted via an exhaust pipe 12 at the upper part A plurality of thermal conductors 13 as heating means are inserted in a dispersed manner into the catalyst bed 4 in the reaction vessel 3 and also extend vertically The lower ends of the thermal conductors 13 are integrally connected an annular fixed plate 14 exposed into the heating bed outside the reaction vessel 3, heat being conducted through this fixed plate 14; thereby facilitating thermal feed into the depth of the catalyst bed, improving thermal efficiency, enabling the sectional area of the catalyst bed for passing the reaction gas to be increased, and improving catalyst packing efficiency

Gas turbine power plant fired by a water-bearing fuel and method for utilizing the heat value of said fuel

Abstract: This publication discloses a method and an apparatus for the utilization of the heat value of a water-bearing fuel in a gas turbine power plant. The apparatus comprises a high-pressure combustion unit (7), a gas turbine (15), a generator (16), and heat recovery units, the latter connected the system close to the gas turbine (15) outlet. According to the invention the water-bearing fuel is dried in a high pressure by the heat energy of the turbine exhaust gases, and the steam generated in the dryer stage is fed to the high-pressure section of the combustion process, at a point between a compressor (9) and the turbine (15), that is, for instance, into the combustion or gasification unit (7). The system in accordance with the invention provides for the utilization of the heat value of fuels having a high moisture content.

Steam turbine generating device

Abstract: PURPOSE:To obtain a steam turbine generating device enabling generating facilities to improve thermal efficiency during low load operation by directly coupling an auxiliary low pressure turbine through a clutch to a main shaft side directly coupled with a high pressure turbine, an intermediate pressure turbine, a main low pressure turbine and a generator. CONSTITUTION:During the normal operation of a steam turbine, a clutch 6 engages mutually to couple an auxiliary low pressure turbine 7 to a generator 5. A closing valve 10 therefore opens to supply steam to steam turbines on a main shaft side and auxiliary shaft one, and then the steam turbines drive the generator 5 to generate electric power. When an exhaust loss level, namely shell pressure at a turbine first stage, becomes lower than its fixed value to issue a low load operation command, the closing valve 10 is closed to disengage the clutch 6, stopping the auxiliary low pressure turbine 7. Consequently, the full closing of the closing valve 10 causes the whole steam to advance into a main low pressure turbine 4, and steam flow quantity through the turbine 4 becomes, twofold in comparison with its usual quantity, resulting in sharp reduction in exhaust loss and effective improvement of thermal efficiency.

Progress on the Investigation of Coal-Water Slurry Fuel Combustion in a Medium-Speed Diesel Engine: Part 5—Combustion Studies

Abstract: This paper reports that in the GE 7FDL single-cylinder research diesel engine, coal-water slurry (CWS) fuel combustion optimization studies were conducted using electronically controlled CWS and pilot accumulator injectors. The most important performance parameters of peak firing pressure, combustion efficiency (coal burnout) and specific fuel consumption were evaluated in relationship to CWS and pilot injection timing, CWS injector hole size, shape, and number, CWS fuel injection spray angles and injection pressure. Heat release diagrams, as well as exhaust samples (gaseous and particulate), were analyzed for each case. Interesting effects of fuel spray impingement and CWS fuel Delayed Ignition were observed. With the engine operating at 2.0 MPa IMEP and 1050 rpm, it was able to obtain over 99.5 percent combustion efficiency while holding the cylinder firing pressure below 17 MPa and thermal efficiency equivalent to diesel fuel operation.

Electronic control system for internal combustion engine

Abstract: An electronic control system for an internal combustion engine, in which parameters necessary for the engine control are found by use of auxiliary quantities to thereby control the operating characteristic quantities of the internal combustion engine, the electronic control system comprising: a memory device for storing in advance, in the form of a two-dimensional map, a charging efficiency per se or related values of the charging efficiency corresponding to a degree of opening of the throttle valve and a number of engine revolution under the reference atmospheric condition; and a computing device for computing atmospheric pressure related values which include therein at least the atmospheric pressure value and are dependent on the atmospheric pressure, in accordance with a predetermined computation equation which takes a ratio of the charging efficiency per se or related values of the charging efficiency to be found out by selective use of signals of the intake air flow rate and a number of revolution of the internal combustion engine.

Output power and efficiency upper bound of real solar heat engines

Abstract: SYNOPSIS Maximum power and efficiency at the maximum power of an irreversible solar heat engine are treated. When time is explicitly considered in the energy exchanges between the solar heat engine and its surroundings, it is found that there is a bound on the efficiency of the real solar heat engine at the maximum power condition. This bound can guide the evaluation of existing solar power generating systems or influence design of future solar heat engines.

A theoretical analysis of a solar-fuel assisted absorption power cycle (SFAPC)

Abstract: This study presents a novel power generating cycle suitable for solar energy applications. A modified version of the conventional LiBr-H2O absorption refrigerating machine is used for the proposed cycle. The condenser, expansion valve and evaporator are replaced by a superheater and a steam turbine, while a flashing tank replaces the generator. The cycle is powered by medium concentrators with a solar collecting temperature of 165°C. Steam generated in the flashing tank (100 kPa) is superheated (using fuel) to 600°C before it expands in the turbine down to 1.25 kPa. This is maintained by the equilibrium conditions in a water cooled absorber, LiBr-H2O solution is directly circulated in the solar collectors and the non-solar energy input to the system is 23% of its total requirements. Results showed that using a 710 ton refrigeration absorption machine, the SFAPC would generate 960 kW shaft power at a system thermal efficiency of 25% which is 44% higher than the available systems. Moreover, when the SFAPC is combined with a vapour compression refrigerator, an overall COP of 1.4 is obtained. This is 72% higher than that of the absorption machine alone at the expense of 23% non-solar energy supply.

Internal combustion engine injection superheated steam

Abstract: A method and apparatus for superheating steam and for injection of same into the air supply of an internal combustion engine are disclosed. A disc-shaped heat exchanger in direct contact with hot exhaust gases is utilized to vaporize and superheat a liquid, particularly water, into superheated steam.

Method of and apparatus for recovering exhaust gas energy of internal combustion engine

Abstract: Disclosed is a type of an exhaust gas energy recovery method for an internal combustion engine of a type which incorporates a turbine generator driven by the exhaust gas energy of the internal combustion engine and in which the driving power of a motor driven by the power generated by the generator is added to the driving power of the internal combustion engine. The method also incorporates a control device for controlling the output torque of the motor in different forms at low and high speed areas within a variable control range of the rotation speed of the internal combustion engine. The motor is operated with constant torque characteristics at the low speed area and with reduced torque characteristics at the high speed area thereby enabling the exhaust gas energy to be efficiently recovered at an engine speed area where the ratio of engine-operating time is high.

Apparatus for heat recovery by using a heat-pump system

Abstract: An apparatus for heat recovery by using a heat-pump system comprising an evaporator (14) configured as an air, water and/or earth collector and an internal combustion engine (2) as drive means, the exhaust gases from the internal combustion engine (2) being subjected to post-combustion in a separate post-combustion unit (3). The waste heat from the internal combustion engine (2) and the heat liberated upon post-combustion of the exhaust gases therefrom is supplied to a heat energy carrying medium, especially water of a heating system or the like, which has already been preheaed by the heat-pump system (5, 6). To this end the internal combustion engine (2) and the post-combustion unit (3) have heat exchangers (4, 15) cooperating therewith, respectively. Furthermore, measures are provided (exhaust gas coolers 7, 8, 9) for cooling the exhaust gases escaping to the atmosphere.

Protection of gas engine or turbine from damage by changes in operating characteristics

Abstract: Apparatus and method are provided to protect a gas engine or turbine used to generate electric power against damage that would otherwise result from changes in the operating characteristics of the engine, for example, changes caused by fluctuation in the heat content of the gaseous fuel. To effect such protection, the engine or turbine is controlled by adjusting the supply of fuel gas to the engine or turbine in response to changes in the output of the electric power generated.

Waste heat steam supercharger

Abstract: A system for supercharging an internal combustion engine. In the present invention, waste heat from an internal combustion engine heats surrounding coolant water to make steam. Steam then passes through a steam compressor, which feeds a high-velocity stream of steam to the intake manifold of the combustion chamber of the engine. This stream draws air and fuel vapor to it, and the resulting supercharged mixture is injected into the combustion chamber of the engine. The high-pressure super-charged mixture exerts pressure on the piston during the intake stroke, increases the pressure inside the combustion chamber, absorbs more heat during combustion, and gathers the engine's waste heat into a high-energy exhaust stream. As a result, the fuel burns more efficiently, less heat is lost from the combustion chamber, engine knocking decreases, thermal stress is reduced, fewer nitrogen oxide pollutants are produced, and the exhaust stream may be used for by-product power generation. In sum, the engine's power output is increased without a corresponding increase in fuel input.

Thermodynamic availability analysis for maximizing a system's efficiency

Abstract: The creation of more efficient chemistry for synthetic fuels and for other needs of the future demands an increased attention to thermodynamics. However, the standard engineering heat, mechanical, and electric energy balances are not well suited to this kind of chemistry screening/system creation task. This article describes a method of tracking work capability losses, which allows screening the various chemistry and unit operation components of a system on the basis of the impact on the overall system efficiency. As will be shown in the work loss analysis for a coal gasification followed by Fischer/Tropsch synthesis plant, the so-called indirect route to liquefication, the choice of chemistry can lock a system into an inherently low efficiency.

Reciprocating engine with rotary cylinder

Abstract: The utility model discloses a reciprocating engine with a rotary cylinder, which belongs to an internal combustion engine of small volume, light weight and high thermal efficiency. On the basis of a star-shaped reciprocating engine, a cylinder is added with a rotary movement, so the cylinder is changed to a rotary cylinder. Because the rotary cylinder does a rotary movement in a fixed cylinder, the phase difference generated between the rotary cylinder and the fixed cylinder when the rotary cylinder rotates can be used for finishing the open and the close of a gas inlet and a gas outlet; thereby, a four-stroke working cycle can be maintained, and a gas valve type gas distribution mechanism in the prior art can be spared. By making use of the utility model, a diesel engine or a gasoline engine can be manufactured. The utility model can be used as motive power for loading motorcars, cars, railway motor cars, ships and other mechanical vehicles.