System and method for comprehensively utilizing residual heat of compressed natural gas engine (CNGE)

Abstract

The invention discloses a system and a method for comprehensively utilizing residual heat of a compressed natural gas engine (CNGE), which relates to a novel energy-saving technology of an engine. In the method, high-pressure fuel gas output by a high-pressure gas cylinder is heated with tail gas and/or the residual heat of water in a cylinder sleeve by using a residual heat exchanger, and the high-pressure fuel gas is depressurized and treated by using two stages of expansion machine devices (a variable-expansion-ratio expansion machine serving as one stage and a fixed-expansion-ratio expansion machine serving as the other stage), so that the fuel gas pressure needed by engine combustion is reached; meanwhile, pressure energy and residual heat are utilized comprehensively by using the expansion machines, so that the output shaft power of the engine is increased, the system efficiency of the engine is increased, the driving mileage is increased, and natural gas consumption is reduced. The device disclosed by the invention is compact in structure, and is reliable in performance; 80 percent of energy consumed in a natural gas compressing process is recovered, so that the advantage of natural gas serving as engine fuel gas is improved remarkably.

Description

technical field [0001] The invention relates to the technical field of waste heat comprehensive utilization and energy saving, in particular to a waste heat comprehensive utilization system and method using a compressed natural gas engine (Compressed Natural Gas Engine, CNGE). Background technique [0002] With the rapid development of the world economy, the number of cars has increased sharply. Cars have brought great convenience to people's travel and made great contributions to human development. However, at the same time, they consume a lot of oil resources and emit a lot of harmful gases. important source. Statistics show that in the air pollution of large and medium-sized cities in western developed countries, about 54% of carbon monoxide CO and 41% of nitrogen oxides NO X , 28% carbon oxide CO X from car exhaust. In my country, automobile exhaust has also become the chief culprit of air pollution. Studies have shown that the main sources of air pollution in Guangz...

AI Technical Summary

Problems solved by technology

Due to the high energy consumption (0.3-0.5kWh / kg) in the process of producing compressed natural gas for vehicles, the high-pressure gas output by the conventional engine through the gas cylinder is depressurized through the pressure reducing valve, resulting in serious throttling loss

In the prior art, a CNGE residual pressure energy recovery device has also appeared. Although the pressure energy of the CNGE has been utilized to a certain extent, there are a series of problems in the process of use. The temperature is low, which is not conducive to making full use of the pressure energy. The other is that there are major defects in the pressure energy release process of CNG. The expander is directly used for decompression. There are no pressure stabilization measures during the decompression process, and the pressure of the pressure source is gradually decaying, resulting in The expander is always working at a variable expansion ratio, which makes the energy output by the expander unstable, and makes the outlet pressure of the expander unstable, which affects the normal and stable operation of the downstream CNGE

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