AU5005297A

AU5005297A - Air to air aftercooler heated bypass with load sensing switching valve

Info

Publication number: AU5005297A
Application number: AU50052/97A
Authority: AU
Inventors: James C. Gilles; Andrew D. Rockwell
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 1996-12-02
Filing date: 1997-10-29
Publication date: 1998-06-29
Also published as: WO1998025012A1

Description

AIR TO AIR AFTERCOOLER HEATED BYPASS WITH LOAD SENSING SWITCHING VALVE

TECHNICAL FIELD

The invention relates to a turbocharger compression ignition engine with an after cooler and more particularly to such an engine that burns a low cetane fuel emulsion and has a heated aftercooler bypass with a load sensing switching valve.

BACKGROUND ART

When controlling the temperature of a fluid passing through a heat exchanger it is common practice to bypass some of the fluid so that a portion of the fluid does not go through the heat exchanger and then blend the bypassed and heated fluid to control the temperature. U.S. Patent 4,086,956 describes a heat exchanger having a bypass between the inlet and outlet chambers and the outlet chamber has a thermostat to control the flow of the heated fluid through the heat exchanger and thus control the temperature of the blended fluid leaving the heat exchanger.

SUMMARY OF THE INVENTION

Among the objects of the invention may be noted the provision of a compression ignition engine that is started and run on low cetane fuel emulsion and has an aftercooler heated bypass which is utilized during startup and when operating at low loads to prevent misfiring and poor performance.

In general, a compression ignition engine comprising a turbocharger, an air to air aftercooler and an intake air manifold disposed in series to supply compressed combustion air to the engine, when made in accordance with this invention, is characterized by a bypass heat exchanger, a modulating bypass valve adapted to respond to intake manifold pressure to control the amount of combustion air bypassing the aftercooler.

The method of operating a turbocharged, compression ignition engine with an air to air aftercooler on a low cetane fuel is characterized by providing a bypass heat exchanger, and providing a modulating bypass valve that responds to intake manifold pressure to pass all of the combustion air through the bypass heat exchanger, when the intake manifold pressure is below a low predetermined pressure. The modulating bypass valve also responds to an increase in manifold pressure above the low predetermined manifold pressure to increase the flow of combustion air through the aftercooler and reduce the flow of combustion air through the bypass heat exchanger as the intake manifold pressure increases above the low predetermined pressure. The modulating bypass valve also responds to pass all of the combustion air through the aftercooler, when the intake manifold exceeds a predetermined high intake manifold pressure. Whereby the engine performance is improved at light loads and high speed and at higher loads the fuel economy, performance and emissions are enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention as set forth in the claims will become more apparent by reading the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts throughout the drawings and in which:

Fig. 1 is a schematic view of a compression ignition engine with an aftercooler and a heated aftercooler bypass controlled by a modulating bypass valve.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings in detail and in particular to Fig. 1 there is shown a water cooled, turbocharged, compression ignition or a diesel engine 1 comprising a intake manifold 3 for supplying combustion air to the engine 1, and an exhaust manifold 5. A turbocharger 7 is disposed in fluid communication with the exhaust manifold 5 which supplies pressurized, heated exhaust gases to drive a turbine portion 9 of the turbocharger 7. Directly connected to the turbine portion 9 of the turbocharger 7 is a compressor portion 11 which takes combustion air from the atmosphere and compresses it. The compressed combustion air is directed from the compressor portion 11 of the turbocharger 7 through a conduit 13 to an air to air aftercooler 15, wherein the compressed combustion air is cooled by ambient air indicated by the arrows A. From the aftercooler 15 the combustion air is then directed via a conduit 17 to the intake manifold 3. An air to air aftercooler bypass heat exchanger 19 is disposed in parallel with the aftercooler 15 to bypass combustion air around the aftercooler 15. An adjustable, modulating bypass valve 21 is disposed in the conduit 17 and is connected to the bypass heat exchanger 19 by a conduit 23. The bypass heat exchanger 19 is also disposed in fluid communication with the conduit 13 via a conduit 25. The bypass heat exchanger 19 is also disposed in fluid communication with an engine cooling water system (not shown) , which supplies heated water to the bypass heat exchanger 19 through the inlet and outlet conduits 27 and 29, respectively. The modulating bypass valve 21 is responsive to inlet manifold pressure, to show this schematically an inlet manifold pressure sensor 31 is shown connected to the modulating bypass valve 21 by a dotted line 33. The modulating bypass valve 21 is adapted to respond to inlet manifold pressure to shut off the aftercooler 15 and pass all of the combustion air through the bypass heat exchanger 19, when the inlet manifold pressure is below a low predetermined pressure. The adjustable modulating bypass valve 21 also adapted to responds to an increase in manifold pressure above the low predetermined manifold pressure to decrease the flow of combustion air from the bypass heat exchanger 19 and increase the flow of combustion air from the aftercooler 15 as the inlet manifold pressure increases above the low predetermined pressure. The adjustable modulating bypass valve 21 is further adapted to respond to reaching and exceeding a high predetermined inlet manifold pressure by shutting off the bypass heat exchanger 19 and passing all of the combustion air through the aftercooler 15. The adjustable modulating bypass valve 21 has an adjustment screw 35, which compresses a spring (not shown) within the valve to adjust a low predetermined pressure below, which the aftercooler 15 is shut off and all of the combustion air passes through the bypass heat exchanger 19.

A method of operating the water cooled, turbocharged, compression ignition or diesel engine 1 with the air to air aftercooler 5 on a low cetane fuel emulsions comprises providing the bypass heat exchanger 19 to heat combustion air that bypasses the aftercooler 15, providing the modulating bypass valve 21 that responds to intake manifold pressure to shut off the aftercooler 15 and pass all of the combustion air through the bypass heat exchanger 19 , when the intake manifold pressure is below a low predetermined pressure, which for a typical engine 1 is generally about 14.5 psia. The modulating bypass valve 21 responds to an increase in manifold pressure above the low predetermined pressure to increase the flow of combustion air through the aftercooler 15 and reduce the flow of combustion air through the bypass heat exchanger 19 as the intake manifold pressure increases above the low predetermined intake manifold pressure. The modulating bypass valve 21 responds to the intake manifold pressure reaching and exceeding a predetermined high intake manifold pressure to shut off the bypass heat exchanger 19 and pass all of the combustion air through the aftercooler 15. The high predetermined inlet manifold pressure for a typical engine 1 is generally about 21 psia. The engine 1 startup and light load high speed performance on low cetane fuel emulsions is improved and higher load fuel economy, performance and emissions are enhanced. The adjustment screw 35 of the modulating bypass valve 21 is also adjustable to compress the spring in the modulating bypass valve to vary the low predetermined inlet manifold pressure to compensate for variations in an individual engine.

While the preferred embodiments described herein set forth the best mode to practice this invention presently contemplated by the inventors, numerous modifications and adaptations of this invention will be apparent to others skilled in the art. Therefore, the embodiments are to be considered as illustrative and exemplary and it is understood that the claims are intended to cover such modifications and adaptations as they are considered to be within the spirit and scope of this invention.

INDUSTRIAL APPLICABILITY The turbocharged compression ignition or diesel engine 1 herein before described advantageously overcomes the poor combustion and misfiring problems encountered by turbocharged compression ignition engines when run on low cetane fuel emulsions during startup and when operated at light loads and high speed by passing the combustion air through the bypass heat exchanger 19 and completely bypassing the aftercooler 15. As the load on the engine 1 increases the bypass valve 21 gradually switches to passing less and less combustion air through the heated bypass heat exchanger 19 and more and more combustion air through the aftercooler 15 promoting better fuel efficiency and performance, and lower emissions.

Claims

1. A water cooled compression ignition engine (1) comprising a turbocharger (7) , an air to air aftercooler (15) and an intake air manifold (3) disposed in series to supply compressed combustion air to the engine (1) characterized by a bypass heat exchanger (19) disposed to bypass the aftercooler (15) , a modulating bypass valve (21) adapted to respond to intake manifold pressure to control the amount of combustion air bypassing the aftercooler (15).

2. The engine (1) as set forth in claim 1 further characterized in that the engine (1) is adapted to run on a low cetane fuel emulsion.

3. The engine (1) as set forth in claim 2 further characterized in that the modulating bypass valve (21) is adapted to respond to the inlet manifold pressure to pass all of the combustion air through the bypass heat exchanger (19) when the intake manifold pressure is below a low predetermined pressure, when the intake manifold pressure increases above the low predetermined pressure the modulating bypass valve (21) is adapted to pass combustion air through the aftercooler (15) in quantities that increase as the intake manifold pressure increases, and when the inlet manifold pressure is higher than a high predetermined inlet manifold pressure, the modulating bypass valve (21) is adapted to pass all of the combustion air through the aftercooler (15) .

4. The engine (1) as set forth in claim 1 further characterized in that the modulating bypass valve (21) is adapted to pass all of the combustion air through the bypass heat exchanger (19) , when the intake manifold pressure is below a low predetermined pressure, when the intake manifold pressure increases above the low predetermined pressure the modulating bypass valve (21) is adapted to pass combustion air through the aftercooler (15) in quantities that increase as the intake manifold pressure increases, and when the inlet manifold pressure is higher than a high predetermined inlet manifold pressure, the modulating bypass valve (21) is adapted to pass all of the combustion air through the aftercooler (15) .

5. The engine (1) as set forth in claim 4 further characterized in that the air passing through the bypass heat exchanger (19) is heated by water from the engine (1) .

6. The engine (1) as set forth in claim 1 further characterized in that the bypass heat exchanger (19) is disposed in parallel with the aftercooler (15) .

7. The engine (1) as set forth in claim 1 further characterized in that the modulating bypass valve (21) can be easily adjusted to vary the low predetermined pressure below which the modulating valve (21) will pass all of the combustion air through the bypass heat exchanger (19) to compensate for variations in various engines (1) .

8. A method of operating a turbocharged, water cooled, compression ignition engine (1) with an air to air aftercooler (15) on a low cetane fuel emulsion characterized by providing a bypass heat exchanger (19) that bypasses the aftercooler (15) , providing a modulating bypass valve (21) that responds to intake manifold pressure to pass all of the combustion air through the bypass heat exchanger (19) , when the intake manifold pressure is below a low predetermined pressure, the modulating bypass valve (21) responding to an increase in manifold pressure above the low predetermined pressure to increase the flow through the aftercooler (15) and reduce the flow through the bypass heat exchanger (19) as the intake manifold pressure increases above the low predetermined pressure and the modulating bypass valve (21) responding to an increase in intake manifold pressure above a high predetermined pressure to pass all of the combustion air through the aftercooler (15) , whereby the engine performance is improved during startup and at light loads and high speed and at higher loads the fuel economy, performance and emissions are enhanced.

9. The method set forth in claim 8 further characterized in that the low predetermined pressure below which the modulating bypass valve (21) passes all combustion air through the bypass heat exchanger (19) can be easily adjusted to compensate for variations different engines.

10. The method set forth in claim 9 further characterized in that the bypass heat exchanger (19) utilized heated water for the engine (1) to heat the combustion air.