The Study of Compression Engine Cycle Behavior in Terms of Variable Gazodynamic and Geometrical Configuration. Regime of the Maximum Economy

2013 ◽  
Vol 837 ◽  
pp. 147-151
Author(s):  
Ion Omocea
Keyword(s):  
Pressure Drop ◽  
Maximum Efficiency ◽  
Combustion Gas ◽  
Low Dissipation ◽  
Pressure Cycle ◽  
Excess Air Coefficient ◽  
Variable Configuration ◽  
Cycle Efficiency ◽  
Filling Coefficient ◽  
Dimensionless Heat

In this analysis, the variable configuration requires a variable distribution. This takes account of the areas offered by the valves and resistance gazodynamic coefficients. All at once the law of efficiency variation describes the variation of the power law. Cycle behavior was analyzed for the following values of the pressure drop coefficient on admission: 5%, 10%, 20% and 40%. For the calculations is necessary to determine the dimensionless heat developed by combustion. I used the following values: for the pressure drop coefficient on admission I use ψa=10 % and for the share of gazodynamic on the suction route conductance in total conductance I use .With this configuration imposed and with (dimensionless heat developed by combustion) resulted: (mean indicated pressure cycle) ; ηv = 0,876 (cylinder filling coefficient) ; α = 1,515 (excess air coefficient) and ηi = 0,499 (indicated cycle efficiency) ; (dimensionless indicated power ); (dimensionless heat taken combustion gas) ; (dimensionless heat taken environment). After numerical analysis result a maximum efficiency with relatively low dissipation.

scholarly journals Thermodynamic Analysis of Different Configurations of Combined Cycle Power Plants

2015 ◽  
Vol 5 (2) ◽  
pp. 89
Author(s):  
Munzer S. Y. Ebaid ◽  
Qusai Z. Al-hamdan
Keyword(s):  
Gas Turbine ◽  
Power Plants ◽  
Combined Cycle ◽  
Cycle Performance ◽  
Maximum Efficiency ◽  
Specific Work ◽  
Slight Effect ◽  
Turbine Engine ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency

<p class="1Body">Several modifications have been made to the simple gas turbine cycle in order to increase its thermal efficiency but within the thermal and mechanical stress constrain, the efficiency still ranges between 38 and 42%. The concept of using combined cycle power or CPP plant would be more attractive in hot countries than the combined heat and power or CHP plant. The current work deals with the performance of different configurations of the gas turbine engine operating as a part of the combined cycle power plant. The results showed that the maximum CPP cycle efficiency would be at a point for which the gas turbine cycle would have neither its maximum efficiency nor its maximum specific work output. It has been shown that supplementary heating or gas turbine reheating would decrease the CPP cycle efficiency; hence, it could only be justified at low gas turbine inlet temperatures. Also it has been shown that although gas turbine intercooling would enhance the performance of the gas turbine cycle, it would have only a slight effect on the CPP cycle performance.</p>

Primary Study on Carbon Dioxide Power Cycle of HTGR

2008 ◽  
Author(s):  
Chengjie Duan ◽  
Xiaoyong Yang ◽  
Jie Wang ◽  
Suyuan Yu
Keyword(s):  
Carbon Dioxide ◽  
High Temperature ◽  
Physical Properties ◽  
Critical Pressure ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Power Cycle ◽  
Pressure Cycle ◽  
Cycle Efficiency ◽  
Thermal Physical Properties

At present, power cycles used in HTGR are indirect steam Rankine cycle and helium Brayton cycle. Using water or helium as working fluid which transform thermal energy into mechanical energy for HTGR power cycle has many disadvantages. Steam cycle could choose steam system which is similar to conventional coal-fired power plant, but because of the limit of material and equipments, there is big temperature difference between the steam and the helium, that makes big loss of thermal power and lowers the cycle efficiency. Helium can reach a high temperature in HTGR Brayton cycle and it has good stability, but because of helium has big isentropic exponent and low density, it is difficult to compress and makes helium turbine has shorter blades and more stages than normal gas turbine. Carbon dioxide has good thermal stability and physical properties. To avoid the reaction of CO2 with graphite and canning of fuel element at high temperature, it should be used in an indirect cycle as second loop working fluid. CO2 has appropriate critical pressure and temperature (7.38MPa, 304.19K) and can choose three types of cycle: supercritical cycle, subcritical-pressure cycle and trans-critical-pressure cycle (CO2 sometimes works under supercritical pressure, some times under subcritical-pressure). Carbon dioxide cycle works in a high pressure, so it makes pressure loss lower. When CO2 works close to its critical point, its density become larger than other conditions, and not change very much, this permits to reduce compress work. The thermal physical properties of carbon dioxide are totally different from helium due to CO2 works as real gas in the cycle. That causes the calculation of CO2 thermal physical properties, heat transfer and power cycle efficiency become difficult and need to be iterated. A systematic comparison between helium and carbon dioxide as working fluid for HTGR has been carried out. An empirical equation had been selected to estimate the thermal physical properties of carbon dioxide. Three types of carbon dioxide power cycle have been analyzed and the thermal efficiency has been calculated. A detailed introduction to the basic calculation process of the CO2 cycle thermal efficiency had been presented in the paper.

scholarly journals Effects of Pressure Drops on the Performance Characteristics of Air Standard Otto Cycle

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
Mahmoud Huleihil
Keyword(s):  
Pressure Drop ◽  
Constant Pressure ◽  
Performance Characteristics ◽  
Maximum Efficiency ◽  
Maximum Pressure ◽  
Otto Cycle ◽  
Pressure Drops ◽  
Internal Irreversibility ◽  
Expansion Model ◽  
Engine Size

The effects of pressure drops on the performance characteristics of the air standard Otto cycle are reported. The pressure drops are assumed as constant values independent of the engine size. It has been shown that the pressure drops to about 60% of the maximum pressure in the ideal cycle (Curto-Risso et al., 2008). Three different models are studied: constant pressure model, reversible adiabatic expansion model and polytropic expansion model. The findings of this study show that, at this level of pressure drop, the maximum efficiency of the Otto cycle is reduced by 15% approximately based on the constant pressure model. The combined effect of pressure drop with other modes of irreversibility, for example, internal irreversibility and heat leaks, could reduce the maximum efficiency into very low values (approximately 30%). The reversible adiabatic model predicts reduction of 13% in efficiency at 40% pressure drop levels but at the price of zero power production. On the other hand, the polytropic expansion model predicts 40% reduction in efficiency for the same level of pressure drop (40%). All three models show that the power output is very sensitive to pressure drop.

Investigation of laminar fluid flow and heat transfer of nanofluid in trapezoidal microchannel with different aspect ratios

2019 ◽  
Vol 29 (5) ◽  
pp. 1680-1698 ◽  
Author(s):  
Hesam Bakhshi ◽  
Erfan Khodabandeh ◽  
Omidali Akbari ◽  
Davood Toghraie ◽  
Mohammad Joshaghani ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Transfer Rate ◽  
Hydraulic Diameter ◽  
Content Type ◽  
Trapezoidal Microchannel ◽  
Dimensionless Heat Flux ◽  
Dimensionless Heat

Purpose In the present study, laminar steady flow of nanofluid through a trapezoidal channel is studied by using of finite volume method. The main aim of this paper is to study the effect of changes in geometric parameters, including internal and external dimensions on the behavior of heat transfer and fluid flow. For each parameter, an optimum ratio will be presented. Design/methodology/approach The results showed that in a channel cell, changing any geometric parameter may affect the temperature and flow field, even though the volume of the channel is kept constant. For a relatively small hydraulic diameter, microchannels with different angles have a similar dimensionless heat flux, while channels with bigger dimensions show various values of dimensionless heat flux. By increasing the angles of trapezoidal microchannels, dimensionless heat flux per unit of volume increases. As a result, the maximum and minimum heat transfer rate occurs in a trapezoidal microchannel with 75° and 30 internal’s, respectively. In the study of dimensionless heat flux rate with hydraulic diameter variations, an optimum hydraulic diameter (Dh) was observed in which the heat transfer rate per unit volume attains maximum value. Findings This optimum state is predicted to happen at a side angle of 75° and hydraulic diameter of 290 µm. In addition, in trapezoidal microchannel with higher aspect ratio, dimensionless heat flux rate is lower. Changing side angles of the channels and pressure drop have the same effect on pressure drop. For a constant pressure drop, if changing the side angles causes an increase in the rectangular area of the channel cross-section and the effect of the sides are not felt by the fluid, then the dimensionless heat flux will increase. By increasing the internal aspect ratio (t_2/t_3), the amount of t_3 decreases, and consequently, the conduction resistance of the hot surface decreases. Originality/value The effects of geometry of the microchannel, including internal and external dimensions on the behavior of heat transfer and fluid flow for pressure ranges between 2 and 8 kPa.

Analysis of pressure drop in T-junction and its effect on thermodynamic cycle efficiency

2018 ◽  
Vol 231 ◽  
pp. 468-480 ◽  
Author(s):  
Pei Lu ◽  
Shuai Deng ◽  
Li Zhao ◽  
Yawei Shao ◽  
Dongpeng Zhao ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Thermodynamic Cycle ◽  
Cycle Efficiency

Heat Transfer and Pressure Drop Characteristics of Water in the Transitional Flow Regime of Horizontal Smooth Tubes at Constant Wall Temperature

2010 ◽  
Author(s):  
J. P. Meyer ◽  
A. Du Preez
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Regime ◽  
Wall Temperature ◽  
Reynolds Numbers ◽  
Transitional Flow ◽  
Maximum Efficiency ◽  
Constant Wall Temperature ◽  
Pressure Losses ◽  
Nusselt Numbers

Owing to design limitations, heat exchangers are frequently forced to operate in the transitional flow regime, however, there exists no accurate measurements for both heat transfer and pressure drop in this region. In order to optimize a heat exchanger for maximum efficiency and minimum pressure losses, it is required to design it for the transitional flow regime. Therefore, the purpose of this study is to obtain accurate Nusselt numbers and pressure drop coefficients for water flowing through a horizontal smooth tube with a constant wall temperature. Heat transfer and pressure drop measurements were conducted on a 5.33 mm tube at Reynolds numbers ranging from 1 000 to 5 000.

Tests on Transport Producer-Gas Units

1943 ◽  
Vol 149 (1) ◽  
pp. 34-47
Author(s):  
Harold Heywood
Keyword(s):  
Pressure Drop ◽  
Peak Power ◽  
Calorific Value ◽  
Maximum Efficiency ◽  
Experimental Plant ◽  
Producer Gas ◽  
Research Association ◽  
High Speeds ◽  
Excess Air ◽  
Full Throttle

The experimental plant installed by the British Coal Utilisation Research Association for testing gas-producers, filters, and engines is described in detail. The results of tests on the engine bench show that a petrol engine converted to use producer gas will only develop about one-half of the normal brake horse-power; moreover, the peak power with gas occurs at a lower speed than with petrol, due to the decrease in volumetric efficiency at high speeds. The effect of increasing the compression ratio was not investigated by the author, but tests by other workers have shown that the gain in power obtained by this means is proportional to the increase in the air standard efficiency. Producer gas-driven engines are very sensitive to mixture strength, and maximum power is obtained with mixtures of gas and air in the proportions theoretically required for the combustion of the gas. Maximum efficiency is obtained with a mixture containing 10 per cent of excess air. Engine tests have also been made to investigate the effect of gas calorific value, of the pressure drop through the producer system, and of petrol addition. Special tests were made to determine the flexibility characteristics of the engine and producer, and the effect of running with various throttle openings, as in actual road operation. Fuel consumption under the latter conditions is about 35 per cent greater than that determined under full-throttle and constant-speed conditions.

scholarly journals Performance evaluation of hydrocyclone filter for microirrigation

2007 ◽  
Vol 27 (2) ◽  
pp. 373-382 ◽  
Author(s):  
Damodhara R . Mailapalli ◽  
Patricia A. A. Marques ◽  
Kochukaleepkal J. Thomas
Keyword(s):  
Pressure Drop ◽  
Filtration Efficiency ◽  
Maximum Efficiency ◽  
Maximum Pressure ◽  
Small Particles ◽  
Pressure Drops ◽  
Elapsed Time ◽  
Solid Suspension ◽  
Discharge Pressure ◽  
Time Of Operation

In this study a hydrocyclone filter of 20 cm was selected and its performance was evaluated by studying the variation of discharge, pressure drop, influent concentration, and filtration efficiency with elapsed time of operation. The filter was tested with clean water to determine clean pressure drop and later it was tested with four concentrations of solid suspension, viz. 300; 600; 900 and 1,200 mg L-1. In the concentration of 300 mg L-1, the variation of pressure drop was low. But for the other concentrations of solid suspension, the variation was significant. The maximum pressure drops obtained were 41.19, 45.11, 50.01 and 52.95 kPa at 350, 390, 280 and 190 minutes of elapsed time, respectively. The maximum efficiency of solid suspension was 30.3, 32.96, 43.89 and 52.5% where as the minimum efficiencies were 9.91, 9.93, 9.62 and 9.9%, respectively. The hydrociclone tested presented inefficiency to filter small particles as clay. The initial removal efficiency of higher concentration was bigger than for lower concentration but, the final efficiency are almost the same irrespective of the concentration of solid suspension. The present tested hydrocyclone could be used as a pre-filter microirrigation to prevent emitter clogging.

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