Methodology for the numerical solution of problems in relation to the coil-type electric heat exchangers for heating fuel

The specificity of the operating conditions of agricultural tractors in the agro-industrial complex requires the provision of reliable engine start at low ambient temperatures. Improving the starting qualities of a diesel engine and reducing incomplete combustion in the post-start period can be achieved by increasing the exergy of the air charge at the end of the compression stroke or increasing the exergy of the fuel injected into the combustion chamber. The purpose of the study is to reduce the expenditure of exergy for prestarting a diesel engine, improve starting qualities and reduce incomplete combustion in the post-start period.

To achieve this goal, the design of an electric heat exchanger was developed in the form of a coil from a high-pressure fuel line, into which a heating element is inserted. A method for calculating its main parameters was developed. Calculations showed that in order to ensure reliable start-up of a diesel engine in winter, it is necessary to heat the fuel in the nozzle to a temperature of 240 °C in the thermal boost mode. A heater of about 98 Watts is required to reach this temperature within 270 seconds of priming. However, in order to maintain such a fuel temperature during the start-up process, it is necessary to make changes in the nozzle design in order to minimize heat losses into the walls of the fuel channel by applying a heat-insulating coating. With further engine operation in the post-start heating mode, the fuel temperature in the injector is reduced to 85–95 °C.