DIRECT FUEL INJECTION DIESEL ENGINE APPARATUS

The efficiency of a direct-injection diesel engine system that uses a low-temperature liquid fuel, such as LNG is improved by effectively utilizing the cooling energy of a high-pressure low-temperature liquid fuel. The system that uses high-pressure natural gas and combusts the engine fuel with intake air pressurized by a supercharger 30 includes a booster pump 3 that injects the high-pressure natural gas into a cylinder of the direct-injection diesel engine and pressurizes low-pressure liquefied natural gas introduced from an LNG tank 1; a cooling-energy recovery heat exchanger 51 that conducts heat exchange between a heat medium in a closed circuit and the high-pressure liquefied natural gas pressurized by the booster pump; and an air-cooling heat exchanger 54 that conducts heat exchange with the heat medium downstream of the cooling-energy recovery heat exchanger to cool air to be introduced into the supercharger and/or intake air compressed by the supercharger.