AIR HANDLING SYSTEM CONSTRUCTIONS WITH EXTERNALLY-ASSISTED BOOSTING FOR TURBOCHARGED OPPOSED-PISTON ENGINES
The air handling system of an opposed-piston engine is equipped with an externally-assisted pumping element such as an electrically-assisted compressor, an electrically-assisted supercharger, or an electrically-assisted turbocharger.
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This application claims priority to U.S. Patent Application Ser. No. 62/143,917, filed in the United States Patent Office on Apr. 7, 2015 and U.S. Patent Application Ser. No. 62/171,918, filed in the United States Patent Office on Jun. 15, 2015. This application contains subject matter related to the subject matter of commonly-owned U.S. patent application Ser. No. 13/782,802, filed Mar. 1, 2013 for “EGR For A Two-Stroke Cycle Engine Without A Supercharger”, which was published as US 2013/0174548 A1 on Jul. 11, 2013. This application also contains subject matter related to the subject matter of commonly-owned U.S. patent application Ser. No. 13/891,622, filed May 10, 2013 for “Air Handling Constructions With Turbo-Compounding For Opposed-Piston Engines”, which was published as US 2014/0331656 A1 on Nov. 13, 2014.
FIELD OF THE DISCLOSUREThe field is two-stroke cycle internal combustion engines. Particularly, the field relates to uniflow-scavenged, opposed-piston engines with air handling systems that provide pressurized charge air for combustion and transport the products of combustion. In some aspects, the field relates to uniflow-scavenged, opposed-piston engines with air handling systems that recirculate and mix exhaust gas with the pressurized charge air in order to lower combustion temperatures.
BACKGROUND OF THE DISCLOSUREA two-stroke cycle engine is an internal combustion engine that completes a power cycle with a single complete rotation of a crankshaft and two strokes of a piston connected to the crankshaft. One example of a two-stroke cycle engine is an opposed-piston engine in which two pistons are disposed in opposition in the bore of a cylinder for reciprocating movement in opposing directions. The cylinder has longitudinally-spaced inlet and exhaust ports located near respective ends of the cylinder. Each of the opposed pistons controls one of the ports, opening the port as it moves to a bottom center (BC) location, and closing the port as it moves from BC toward a top center (TC) location. One of the ports provides passage of the products of combustion out of the bore, the other serves to admit charge air into the bore; these are respectively termed the “exhaust” and “intake” ports. In a uniflow-scavenged opposed-piston engine, charge air enters a cylinder through its intake port as exhaust gas flows out of its exhaust port. Thus gas flows through the cylinder in a single direction (“uniflow”)—from intake port to exhaust port—to both vacate the cylinder of exhaust gas and to resupply it with charge air (“scavenging”).
In
As the pistons 60 and 62 of a cylinder 50 near TC, a combustion chamber is defined in the bore 52 between the end surfaces 61 and 63 of the pistons. Fuel is injected directly into the combustion chamber through at least one fuel injector nozzle 70 positioned in an opening through the sidewall of a cylinder 50. The fuel is mixed with charge air compressed between the end surfaces, and it ignites in response to the heat and pressure of the compressed charge air. Combustion follows.
With further reference to
In greater detail, the air handling system 80 includes a turbocharger 120 with a turbine 121 and a compressor 122. The turbine 121 and compressor 122 rotate on a common shaft 123. The turbocharger 120 extracts energy from exhaust gas that exits the exhaust ports 54 and flows into an exhaust passage 124 directly from the exhaust ports 54, or from an exhaust manifold 125 that collects exhaust gasses output through the exhaust ports 54. In this regard, the turbine 121 is rotated by exhaust gas passing through it. This rotates the compressor 122, causing it to generate charge air by compressing fresh intake air that flows into it from a charge air channel inlet. The charge air generated by the compressor 122 flows through a charge air passage 126 to a charge air cooler 127. Presuming the addition of the supercharger 110, cooled charge air is pumped by the supercharger 110 to the intake ports. Air compressed by the supercharger 110 may be output through a second charge air cooler 129 to an intake manifold 130. The intake ports 56 receive charge air pumped by the supercharger 110, through the intake manifold 130. Preferably, in multi-cylinder opposed-piston engines, the intake manifold 130 is coupled to an intake plenum that communicates with the intake port or ports 56 of the engine 10.
The air handling system shown in
The EGR loop construction shown in
A low pressure EGR loop (also called a “long loop”) circulates exhaust gas obtained from a source downstream of the turbine outlet to a mixing point upstream of the compressor intake. Typically, a short loop EGR configuration is favored for fast response, low complexity, and high durability, at the cost of pumping loss, high concentration of exhaust products in the charge air channel, and turbine lag. A long loop configuration is favored for lower pumping loss, higher mass flow through the turbocharger, and higher cooling capacity, at the cost of even slower turbine response and greater complexity.
Exhaust gas from the exhaust ports of the cylinders 50 flows from the exhaust manifold 125 into the inlet 121i of the turbine 121, and from the turbine's outlet 1210 into the exhaust outlet passage 128. A turbine bypass channel 143 including a wastegate valve 144 runs in parallel with the turbine 121, between its inlet 121i and outlet 121o. The valve 144 is operated to control the amount of exhaust gas flowing from the engine into the turbine 121. Fully opening the valve 144 to bypass the turbine 121 allows exhaust energy to be transported into the exhaust outlet passage 128 without operating the turbine 121 and compressor 122. In some instances, the turbine 121 may comprise a variable-geometry turbine (VGT) device, which would afford further control of gas flow (and pressure) in the exhaust channel. In these aspects, the turbine 121 will have an effective opening size that may be varied in response to changing speeds and loads of the engine. In some instances, one or more after-treatment devices 162 are provided in the exhaust channel, downstream of a backpressure valve 170. Exhaust is recirculated through the EGR passage 131, under control of the EGR valve 138. The EGR passage 131 is in fluid communication with the charge air channel via an EGR mixer 163. In some instances, although not necessarily, an EGR cooler (“EGR cooler 164”) is provided in the EGR passage 131, in series with the EGR valve 138 and the EGR mixer 163. In other instances, there may be no cooler in the EGR passage 131.
With further reference to
Without a supercharger in the air handling system, a turbocharged two-stroke cycle engine can perform poorly in response to a demand for a sudden increase in engine speed. In this regard, when the engine starts, or when it operates at low loads and/or low speeds, the flow of exhaust may be insufficient to enable the compressor to achieve the speed necessary to increase the flow of charge air (“boost”) to a level that is adequate to achieve the requested engine speed. Further, the turbine operation may lag in response to an increasing exhaust flow. In order to reduce the transient response time imposed by the turbocharger, a mechanically-driven supercharger may be added to the charge air channel, downstream of the compressor outlet, so as to quickly provide the boost needed for the demanded increase. However, the supercharger and its associated coupling mechanism bring additional weight and size to the engine and so constitute significant impediments to downsizing.
Further, in the face of requirements for increased efficiency of engine operation, it becomes ever more important to quickly and precisely control gas flow (exhaust and charge air) through the engine in response to changes in speed and load. The control mechanization of the air handling system illustrated in
It is desirable to equip the air handling system of a turbocharged opposed-piston engine for quick, yet smooth charge air flow acceleration while starting the engine, and in response to acceleration demands encountered during low speed and light load conditions, without sacrificing the engine's efficiency and/or power density. These and other goals and objectives may be realized by use of an externally-assisted pumping element for the charge air channel of the air handling system. Such an externally-assisted pumping element may include an electrically-assisted compressor, an electrically-assisted supercharger, or an electrically-assisted turbocharger.
Desirably, external assistance of the very elements that create charge air flow in a turbocharged, opposed-piston engine provides the basis for finer control of charge air flow over a broader range of effectiveness than is achievable with currently-available air handling constructions.
This disclosure is directed to aspects of air handling system construction and operation for turbocharged opposed-piston engines with the understanding that these aspects may be combined with other opposed-piston engine systems and functions such as fuel injection, cooling, lubrication, and so on. In this disclosure, an air handling system for a turbocharged opposed-piston engine according to
Electrically-Assisted Compressor:
An air handling system for a turbocharged opposed-piston engine in which an electrically-assisted compressor provides boost during engine startup and acceleration is illustrated by respective embodiments shown in
In this disclosure, and with reference to
With reference to
With reference to
With reference to
With reference to
With reference to the air handling system illustrated in
Electrically-Assisted Supercharger:
An air handling system for a turbocharged opposed-piston engine in which an electrically-assisted supercharger provides boost during engine startup and acceleration is illustrated by respective embodiments shown in
In this disclosure, and with reference to
With reference to
With reference to the embodiment illustrated in
One of the exhaust outlets is coupled to provide exhaust gas to the turbine inlet 122i via the manifold 262; the other exhaust outlet is coupled to the input of a short EGR loop 260 by an exhaust manifold 264. The output of the short EGR loop 260 is placed in the charge air channel via the mixer 265, downstream of the compressor 122, between the compressor outlet 122o and the charge air cooler 266. The charge air cooler 266 is placed in the charge air channel, downstream of the mixer 265, between the mixer 265 and the inlet 250i of the electrically-assisted supercharger 250.
In order to serve the charge air inlets, the charge air channel includes first and second branches 270 and 272 downstream of the electrically-assisted supercharger 250. The first and second branches 270 and 272 have a common input 273 coupled to the outlet 250o of the electrically-assisted supercharger 250, and each of the branches includes a respective charge air cooler 274 and 276 placed between the common input 273 and a respective one of the charge air inlets. The turbine 121 may comprise a VGT device.
Although not shown in
Referring to
Electrically-Assisted Turbocharger:
In an air handling system for a turbocharged opposed-piston engine, the turbocharger comprises an electrically-assisted turbocharger as illustrated by respective embodiments shown in
In this disclosure, and with reference to
With reference to
In the embodiment illustrated in
In
With reference to
In some instances, when excessive power is generated by the turbine 321, the motor 325 can act as a generator and provide electric power for use or storage.
Although this disclosure describes particular embodiments for air handling systems with externally-assisted boosting for turbocharged opposed-piston engines, these embodiments are set forth merely as examples of underlying principles of this disclosure. Thus, the embodiments are not to be considered in any limiting sense.
Claims
1. An air handling system for an opposed-piston engine, including at least one cylinder with piston-controlled exhaust and intake ports, comprising:
- a charge air channel coupled to provide charge air to at least one intake port of the opposed-piston engine;
- an exhaust channel coupled to transport exhaust gas from at least one exhaust port of the opposed-piston engine;
- a turbocharger with a turbine in the exhaust channel and a first compressor in the charge air channel; and,
- an electrically-assisted compressor in the charge air channel upstream of the first compressor, between a fresh air inlet of the charge air channel and an inlet of the first compressor.
2. The air handling system of claim 1, further including an EGR loop including an inlet coupled to the exhaust channel, downstream of an outlet of the turbine, and an outlet coupled to the charge air channel, upstream of the electrically-assisted compressor.
3. The air handling system of claim 2, further including a charge air cooler in the charge air channel between an outlet of the electrically-assisted compressor and the inlet of the first compressor.
4. The air handling system of claim 2, further including an aftertreatment device in the exhaust channel, between an outlet of the turbine and the EGR loop inlet.
5. (canceled)
6. The air handling system of claims 1-4, in which the charge air channel includes first and second branches downstream of the first compressor, the first and second branches have a common input coupled to an outlet of the first compressor, and each branch includes a respective charge air cooler.
7. The air handling system of claim 1, without an EGR loop.
8. The air handling system of claim 7, further comprising:
- a valve-controlled bypass loop including an inlet in the charge air channel, between the fresh air inlet and an inlet of the electrically-assisted compressor, and an outlet in the charge air channel, between the outlet of the electrically-assisted compressor and the inlet of the first compressor; and
- a back pressure valve in the exhaust channel, downstream of the turbine.
9. An air handling system for an opposed-piston engine including at least one cylinder with piston-controlled exhaust and intake ports, comprising:
- a charge air channel coupled to provide charge air to at least one intake port of the opposed-piston engine;
- an exhaust channel coupled to transport exhaust gas from at least one exhaust port of the opposed-piston engine;
- a turbocharger with a turbine in the exhaust channel and a first compressor in the charge air channel; and,
- an electrically-assisted compressor in the charge air channel downstream of the first compressor, between an outlet of the first compressor and the at least one intake port.
10. The air handling system of claim 9, without an EGR loop.
11. The air handling system of claim 10, further comprising at least one charge air cooler in the charge air channel, downstream of the first compressor.
12. The air handling system of claim 11, in which the at least one charge air cooler is in a portion of the charge air channel between the outlet of the first compressor and an Inlet of the electrically-assisted compressor.
13. The air handling system of claim 10, further comprising a valve-controlled back flow prevention loop including an inlet in the charge air channel, in common with an intake of the electrically-assisted compressor, and an outlet in the charge air channel, in common with the outlet of the electrically-assisted compressor.
14. An air handling system for an opposed-piston engine including at least one cylinder with piston-controlled exhaust and intake ports, comprising:
- a charge air channel coupled to provide charge air to at least one intake port of the opposed-piston engine;
- an exhaust channel coupled to transport exhaust gas from at least one exhaust port of the opposed-piston engine;
- a turbocharger with a turbine in the exhaust channel and a compressor in the charge air channel;
- an electrically-assisted supercharger in the charge air channel downstream of the compressor, between an outlet of the compressor and the at least one intake port; and,
- an EGR loop including an inlet coupled to an exhaust port manifold in direct fluid communication with at least one exhaust port and an outlet coupled to the charge air channel, upstream of the electrically-assisted supercharger.
15. The air handling system of claim 14, in which the charge air channel includes first and second branches downstream of the electrically-assisted supercharger, the first and second branches have a common input coupled to an outlet of the electrically-assisted supercharger, and each branch includes a respective charge air cooler.
16. An air handling system for an opposed-piston engine, in which the engine has no supercharger and includes at least one cylinder with piston-controlled exhaust and intake ports, the air handling system comprising:
- a charge air channel coupled to provide charge air to at least one intake port of the opposed-piston engine;
- art exhaust channel coupled to transport exhaust gas from at least one exhaust port of the opposed-piston engine;
- an electrically-assisted turbocharger with a turbine in the exhaust channel and a compressor in the charge air channel;
- at least one charge air cooler in the charge air channel, downstream of the compressor.
17. The air handling system of claim 16, further comprising a back pressure valve in the exhaust channel, downstream of the turbine.
18. The air handling system of claim 17, further including an EGR loop including an inlet coupled to the exhaust channel, between the back pressure valve and an outlet of the turbine, and an outlet coupled to the charge air channel, upstream of the compressor.
19. The air handling system of claim 18, in which the turbine is a variable geometry turbine.
20. The air handling system of claim 18, in which the charge air channel includes first and second branches downstream of the compressor, the first and second branches have a common input coupled to an outlet of the compressor, and each branch includes a respective charge air cooler.
21. The air handling system of claim 16, without an EGR loop.
Type: Application
Filed: Mar 22, 2016
Publication Date: Oct 25, 2018
Applicant: ACHATES POWER, INC. (San Diego, CA)
Inventors: FABIEN G. REDON (SAN DIEGO, CA), SURAMYA D. NAIK (SAN DIEGO, CA)
Application Number: 15/562,374