Engine device

Abstract

An engine device includes a main throttle valve disposed at a portion where an outlet of a supercharger and an inlet of an intercooler are coupled to each other, an exhaust bypass flow path configured to couple an outlet of an exhaust manifold to an exhaust outlet of the supercharger, an exhaust bypass valve disposed in the exhaust bypass flow path, an air supply bypass flow path configured to bypass a compressor of the supercharger, and an air supply bypass valve disposed in the air supply bypass flow path. Within a low load range of a load on the engine device, when the load is lower than a predetermined load, feedback control is performed on the main throttle valve, and when the load is higher than the predetermined load, map control based on a data table is performed on the main throttle valve.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application is a continuation application of International Application No. PCT / JP2015 / 065455, filed May 28, 2015, which claims priority to Japanese Patent Application No. 2014-118036, filed Jun. 6, 2014, Japanese Patent Application No. 2014-118037, filed Jun. 6, 2014. The contents of these applications are incorporated herein by reference in their entirety.BACKGROUND OF THE INVENTION[0002]The present invention relates to an engine device.[0003]Heretofore, in ships, such as a tanker and a transport ship, and land-based power generation facilities, diesel engines have been used as their driving sources. Exhaust gas discharged from such a diesel engine, unfortunately, contains a large number of exhaust emissions, such as oxides of nitrogen, oxides of sulfur, and particulate matter, that are likely to become harmful substances that impede environmental preservation. For this reason, recently, a gas engine, one of engines each serv...

AI Technical Summary

Benefits of technology

[0005]In such a dual fuel engine, for a diesel mode and a gas mode, there is a difference in a required air-fuel ratio, and further, an air flow amount required in the gas mode is small compared with the diesel mode relative to the same load. For this reason, a supercharger is required to meet a specification in the diesel mode, whereas, when operated in the gas mode, the supercharger is required to be capable of providing air amount appropriate to an air-fuel ratio in the gas mode. Further, in conventional dual fuel engines, when operated in the gas mode, there is room for improvement to realize sufficient responsiveness in air flow amount control, and high trackability and appropriateness relative to a load variation in air-fuel ratio control.

[0012]According to the embodiment of the present invention, an engine device includes at least one cylinder; an intake manifold configured to supply air into the at least one cylinder; an exhaust manifold configured to discharge exhaust gas from the at least one cylinder; at least one main fuel injection valve configured to inject liquid fuel into the at least one cylinder to cause combustion of the liquid fuel; at least one gas injector configured to mix gas fuel with the air supplied by the intake manifold; a supercharger including a compressor and configured to compress air through a use of the exhaust gas from the exhaust manifold; an intercooler configured to cool compressed air resulting from the compression by the supercharger and supply resultant cooled air to the intake manifold; a main throttle valve disposed at a portion where an outlet of the supercharger and an inlet of the intercooler are coupled to each other; an exhaust bypass flow path configured to couple an outlet of the exhaust manifold to an exhaust outlet of the supercharger; an exhaust bypass valve disposed in the exhaust bypass flow path; an air supply bypass flow path configured to bypass the compressor of the supercharger; and an air supply bypass valve disposed in the air supply bypass flow path. Further, within a low load range of a load on the engine device, when the load is lower than a predetermined load, feedback control is performed on the main throttle valve, and when the load is higher than the predetermined load, map control based on a data table is performed on the main throttle valve. Thus, in a state in which the supercharger is optimized in accordance with a combustion mode specification for liquid fuel, in a combustion mode using gas fuel, control of each of the opening degree of the exhaust bypass valve and the opening degree of the air supply bypass valve in accordance with the variation of the engine load also realizes an air-fuel ratio optimized to the engine load. During a load variation, therefore, the deficiency of the amount of air needed for the combustion is eliminated or minimized, and as a result, the engine device also operates in a suitable condition in the gas mode in a state in which the supercharger optimized for use in the diesel mode is used.

[0013]Further, within the low load range, when the engine load is higher than the predetermined load, feedback control on the exhaust bypass valve and map control on the air supply bypass valve are concurrently performed, and thus, the responsiveness of flow amount control by the exhaust bypass valve is complemented by the air supply bypass valve, and a control range of the air supply bypass valve is complemented by the exhaust bypass valve. Moreover, within the low load range, in the case where the engine load is lower than the predetermined load, even when air pressure inside the intake manifold becomes negative during a low load operation, concurrent control of causing the exhaust bypass valve to fully open and of causing the air supply bypass valve to be fully closed realizes securing an air amount needed for the combustion.

[0014]Further, according to the embodiment of the present invention, within a medium and high load range, each of the exhaust bypass valve and the air supply bypass valve is controlled so as to allow pressure inside the intake manifold to be adjusted to a target value appropriate to the load. Thus, in a state in which the supercharger is optimized in accordance with a combustion mode specification for liquid fuel, in a combustion mode using gas fuel, the air-fuel ratio is controlled so as to be responsive to the variation of the engine load. In this regard, during a load variation, the deficiency of the amount of air needed for the combustion is eliminated or minimized, and as a result, the engine device also operates in a more suitable condition in the gas mode in a state in which the supercharger is optimized for use in the diesel mode is used.

[0015]Further, within the medium and high load range, feedback control on the air supply bypass valve and map control on the exhaust bypass valve that are concurrently performed realize supplying the engine device with air adapted to an air-fuel ratio needed for the combustion of the gas fuel. Control of the opening degree of the exhaust bypass valve in accordance with the variation of an engine load realizes supplying the engine with air adapted to an air-fuel ratio needed for the combustion of the gas fuel. Further, a combination with responsive control operation by the air supply bypass valve increases trackability relative to a load variation in the gas mode. Moreover, control of air pressure by both of the air supply bypass valve and the exhaust bypass valve realizes expansion of a control range of the control of air pressure.

Problems solved by technology

Exhaust gas discharged from such a diesel engine, unfortunately, contains a large number of exhaust emissions, such as oxides of nitrogen, oxides of sulfur, and particulate matter, that are likely to become harmful substances that impede environmental preservation.

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