Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
2001-03-14
2003-01-28
Denion, Thomas (Department: 3748)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C123S563000, C123S559100
Reexamination Certificate
active
06510690
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a diesel engine with a supercharger.
BACKGROUND ART
A diesel engine with a supercharger generally includes a heat exchanger in a supercharged air passage from an outlet port of the supercharger to an inlet port of a cylinder, and cools supercharged air that has pressure and temperature increased by the supercharger. As the heat exchanger, an air cooling type of heat exchanger with outside air as a heat exchange medium, or a water cooling type of heat exchanger with the cooling water as a heat exchange medium is generally used.
For example, Japanese Patent Laid-open No. 57-35116 and Japanese Patent Publication No. 3-4731 disclose “a hybrid type of heat exchanger including a water cooling type of heat exchanger at an upstream side, and an air cooling type of heat exchanger at a downstream side, which has a bypass supercharged air passage with an on-off valve, in the order from an outlet port of a supercharger to an inlet port of a cylinder”. It should be noted that the latter is an improvement over the former, and the latter has the configuration in which the water cooling type of heat exchanger at the upstream side together with the on-off valve is housed in an upper tank of the air cooling type of heat exchanger at the downstream side. This configuration provides the operation and effects that the upper tank is also used as the bypass supercharged air passage and thereby the compact diesel engine with the supercharger is provided.
The above conventional configurations, however, have the following disadvantages, which cannot make the engine as compact as expected.
(1) The temperature of cylinder intake air varies to a large extent according to the driving conditions (atmosphere temperature, engine load, and the like). The temperature of the cylinder intake air becomes extremely cold due to low-temperature atmosphere in cold regions, severely cold regions, and the winter season, and, for example, under medium and heavy load, an excess air ratio increases, whereby combustion efficiency increases, thereby producing excessive output power contrary to the intention. Further, since the temperature is low inside the cylinder under light load, poor ignition easily occurs, and thus it is difficult to operate engine with stability. On the other hand, in tropical regions and in the summer season, the temperature of exhaust gas rises due to high-temperature atmosphere under heavy load, thereby decreasing durability of the components constructing the engine. In addition to the above disadvantages, there is a heat balance problem of the engine main body corresponding to a change in engine load. Accordingly, with only an air cooling type of heat exchanger, the heat exchanger itself increases in size and the heat exchanger needs to be provided with an air flow adjusting mechanism such as a large shutter or the like, thus making the heat exchanger system itself larger in size. Meanwhile, with only a water cooling heat exchanger, a large quantity of cooling water is needed, thus making a cooling system such as a cooling radiator and the like larger in size. Specifically, the water cooling type of heat exchanger alone or the air cooling type of heat exchanger alone is unfavorable in making the engine compact.
(2) As for the temperatures of outside air, cooling water, and supercharged air at the supercharger outlet port during normal rotation of the engine, the temperature is higher in the order of “the outside air temperature<the cooling air temperature<the supercharged air temperature at the supercharger outlet port”. The aforementioned “during normal rotation of the engine” means “after the starting of the engine, and during the rotation of the engine after the completion of warming-up, that is, during rotation of the engine irrespective of a low idle or a high idle, and the magnitude of load”. In the aforesaid conventional hybrid type of heat exchanger, the water cooling type of heat exchanger is provided at the upstream side, and therefore the engine cooling water is heated by a high-temperature supercharged air. Consequently, a large amount of cooling water is required to secure heat balance of the engine body corresponding to a change in engine load, whereby the radiator for cooling water and the like are made larger in size and the cooling system increases in size. Namely, even with the aforesaid conventional hybrid type of heat exchanger, the engine cannot be made as compact as expected.
(3) As for a diesel fuel, light oil is generally used, but fuels inferior to light oil in ignitability with normal compression ratio, for example, fuel oil A, a waste plastic oil fuel, a water emulsion fuel (fuel made by mixing fuel and water and emulsifying the same) and the like are sometimes used. Explaining with the water emulsion fuel as an example, as seen from the actual measurement results of the three types of engines shown in
FIG. 10
, this fuel has an effect of reducing injurious materials such as nitrogen oxides, black lead and the like, which are exhausted from a diesel engine, as a result of increasing content of water in the fuel. However, if the amount of water is increased in the above fuel, the aforesaid disadvantage (specifically, “abnormal combustion easily occurs in the cylinder, which makes it difficult to operate the engine with stability”) is promoted when the temperature of intake air of the cylinder is low (in cold regions, in severely cold regions, in the winter season, and under light load, etc.). When the content of water reaches 50%, the operation becomes unstable even at a room temperature. This is because water in the water emulsion fuel injected during the compression stroke of the engine vaporizes and the temperature inside the cylinder is reduced by the latent heat, whereby ignition and combustion of the water emulsion fuel (that is, engine performance) are hindered.
SUMMARY OF THE INVENTION
The present invention is made in view of the aforesaid disadvantages, and its object is to provide a diesel engine with a supercharger, which is capable of contributing to reduced engine in size, and which hardly has an adverse effect on the engine performance even with use of a fuel inferior to light oil in ignitability with a normal compression ratio.
In order to attain the above object, a first configuration of a diesel engine with a supercharger according to the present invention is
a diesel engine with a supercharger including a supercharger for taking in and pressurizing outside air and supplying the pressurized supercharged air into a cylinder, and a heat exchanger, which is provided in a supercharged air passage from an outlet port of the supercharger to an inlet port of the cylinder and cools the supercharged air from the supercharger, and
the heat exchanger is a hybrid type of heat exchanger including
a first heat exchanger for carrying out heat exchange between the supercharged air from the outlet port of the supercharger and a first heat exchange medium, and
a second heat exchanger for carrying out heat exchange between the supercharged air from an outlet port of the first heat exchanger and a second heat exchange medium having higher temperature than the first heat exchange medium, and supplying the supercharged air after the heat exchange with the second heat exchange medium to the cylinder.
As a second configuration of the diesel engine with the supercharger, a fuel used may be a water emulsion fuel.
As a third configuration of the diesel engine with the supercharger, the engine may be a water cooling type of engine with use of cooling water,
the first heat exchange medium is outside air, and
the second heat exchange medium is cooling water from the water cooling type of engine.
As a fourth configuration of the diesel engine with the supercharger, it may be suitable to further include load detecting means for detecting load of the engine, and
control means for receiving a detection signal from the load detecting means and controlling flow of the second heat exchange medium or flow of cooling water from the water
Furukawa Hideo
Satou Hiroyasu
Armstrong Westerman & Hattori, LLP.
Denion Thomas
Komatsu Ltd.
Trieu Thai-Ba
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