Study On Coupling Characteristics Of Thermal System Between Internal Combustion Engine And Coal-fired Generator

Developing renewable energy and greatly improving the peak-regulating capacity of coal-fired generator to build a clean,low-carbon,safe and efficient modern energy system,which is the research hotspots.The flexible energy facilities is coupled to coal-fired system are important measures to improve the flexibility of coal-fired system and efficiently absorb renewable energy.This paper aimed to develop an efficient and flexible thermal system for coupling internal combustion engine and coal-fired generator.Using theory and numerical simulation method to optimize internal combustion engine and coal-fired generator coupled system.The output performance of the internal combustion engine and coal-fired generator coupled system under rated load and variable load conditions was also studied in this study.The theoretical model of internal combustion engine and coal-fired generator coupled system was established.Based on EBSILON Professional thermodynamic simulation software,the physical and mathematical model of the coupling system including the steam turbine,condenser,regenerative heater and flue gas waste heat exchanger of internal combustion engine were established.The thermal economy of the coupled system is evaluated in view of the thermodynamics analysis.This study provided a basis to design and application for the coupling system.To improve the flexible ability and economic performance for the coupled system,Different combustion engines and coal-fired generator coupled systems were proposed.We integrated internal combustion engine into coal-fired generator.Using waste heat of internal combustion engine and cylinder liner cooling water to reduce system consumption and improve the economic performance.Appling high pressure heat exchanger to heat high pressure feed water of coal-fired generator.In addition,low pressure heat exchanger heat low pressure condensing water of coal-fired generator.Meanwhile,the waste heat of cylinder liner cooling water was used to heat the low-pressure condensing water of coal-fired generator.The exhausted temperature of internal combustion engine was ranged from 372 ~oC to 446 ~oC.After waste heat recovery,the outlet temperature of exhausted gas decreased to 110 ~oC.According to the different temperature of the heated water,six coupled systems were proposed in the high-pressure heat exchanger of flue gas.Ten coupled systems in the low-pressure heat exchanger of flue gas were proposed.Meanwhile,nine coupled systems in the waste heat of cooling water of internal combustion engine were also proposed and compared.The output characteristics of different internal combustion engines and coal-fired generator coupled system were studied under rated load.After comparing economic performance of different coupled system,the optimal coupled system was obtained based on the lowest system heat consumption rate.The optimal system had following characteristics:(1)The flue gas waste heat high pressure heat exchanger was in parallel with all the high-pressure heaters of the coal-fired generator.(2)The flue gas waste heat low pressure heat exchanger was in parallel with the low-pressure heater with high extraction temperature of the coal-fired generator.(3)The cooling water waste heat is coupled with the low-pressure heater with small heat transfer temperature difference.Under optimal condition,when the outlet temperature of flue gas waste heat high-pressure heat exchanger was 187.9 ~oC,the heat consumption rate of the coal-fired generator was reduced by 6.62%.Power generation efficiency increased by3.39%.The output characteristics of coupled systems were studied in variable load conditions.When the load rate of coal-fired generator set is 75%and 100%and eight working conditions where the load rate of internal combustion engine is 30%,50%,70%and 100%,the economic performance of different coupled system was compared.When the load of internal combustion engine increased from 30%to 100%and load rate of coal-fired generator are 100%and 75%,compared with uncoupled internal combustion engine,the heat consumption rate of coupled system was reduced by 3.23%-6.62%and 4.15%-8.73%,respectively.Power generation efficiency increased by 1.6%-3.39%and 2.03%-4.48%,respectively.This study provides theoretical support for optimization of flexible energy facilities and coal-fired generator coupled system.