The present disclosure pertains to electric machines and turbochargers, and more particularly, to electric machines for operating in connection with turbochargers on internal combustion engines.
A turbocharger or exhaust driven supercharger is a device, driven at least partially off the combustion exhaust of an internal combustion engine, that boosts the pressure and throughput of combustion air into the engine. The turbocharger has a compressor, typically a centrifugal compressor, for compressing the combustion air. The compressor resides on a common shaft with a turbine, typically a radial or axial turbine, for receiving the combustion exhaust and driving the compressor via the common shaft. The compressor, turbine and shaft define the rotating assembly of the turbocharger.
Like reference symbols in the various drawings indicate like elements.
A turbocharger system on an engine can include an electric machine coupled to the rotating assembly of the turbocharger. The electric machine can assist driving the compressor to create higher supercharging pressure for engine operation, without having to rely on a supply of exhaust from the engine. The electric machine can also be used to recover energy from the engine, output by the engine in the form of excess exhaust. The energy recovered by the electric machine can be stored and used in powering the electric machine and/or can supplement other systems, including supplementing power to a power distribution grid. Other uses than those identified above for this power can be envisioned based on the specific application of the engine.
The electric machine 202 includes a rotor 208 and a stator 210. The rotor 208 is configured to rotate within the stator 210, as described in more detail below. In certain instances, the electric machine 202 is a permanent magnet, synchronous, multiphase alternating current (A/C) motor/generator, where the magnetic field of the rotor 208 is generated entirely or in part by one or more permanent magnets. To this end, in
The stator 210 includes a winding 226 that can carry electrical current and either generate an electromagnetic field to drive the rotor 208 to rotate or, when the rotor 208 is rotated by the shaft 204, receive an induced current (i.e., generate electrical power). The stator 210 is contained (at least partially, or as shown in
Although described herein as a permanent magnet AC electric machine 202, the electric machine 202 can take other forms, AC or DC, with or without permanent magnets, and/or other variations.
The electric machine 202 is electrically coupled to a power electronics module 230. In certain instances, the power electronics module 230, as will be discussed in more detail below, is bidirectional and conditions the electrical power to and from the electric machine 202 to specified parameters (e.g., specified voltage and/or frequency). In other instances, the power electronics module 230 is unidirectional. To enable driving the electric machine 202, the power electronics module 230 can include a variable frequency drive. The power electronics module 230 is coupled to a controller 232 that operates in controlling the electric machine 202 and/or the power electronics 230. For example, the controller 232 can control the power electronics module 230 to control the rate at which the electric machine 202 rotates when operating as a motor, as well as change the electric machine 202 between motoring and generating. The controller 232 can be separate from the engine's engine control unit (ECU) and communicate with the ECU and/or the controller 232 can be integrated with the engine's ECU.
The electric machine 202 is carried in the turbocharger system housing assembly 214. In certain instances, as shown in
Although shown in
The turbine of the turbocharger system 200 is coupled to receive combustion exhaust from combustion of fuel and air within the internal combustion engine via the engine's exhaust manifold. The engine can be a reciprocating internal combustion engine powered by heavy fuel oil, diesel, gasoline, natural gas and/or other fuel. In other instances, the engine could be another type of engine. For example, the engine could be a non-piston type engine, such as a Wankel rotary engine and/or other type of engine. The exhaust output from the engine passes through the turbine and drives the turbine to rotate, and in turn, rotate the compressor 206. As the compressor 206 rotates, it draws in air from the intake portion 218, compresses the air and outputs that compressed air to the engine for use in combusting fuel. The amount of exhaust available to drive the turbine and, thus the compressor 206, is dependent on engine operation. For example, the engine produces more exhaust under high load and/or at high operational speeds, and less exhaust under low load and/or at low operational speeds. Greater amounts of exhaust typically enable driving the compressor 206 to rotate more quickly. The flow and pressure of air output by the compressor 206, in turn, is dependent on the speed at which the compressor 206 rotates and the efficiency of the compressor at the rotational speed. Therefore, the flow and pressure output from the compressor 206, to the extent the compressor 206 is driven by the turbine, is tied to the engine operating conditions.
At some engine operating conditions, the engine does not produce enough exhaust to rotate the compressor 206 at a rate that produces a desired or specified flow and pressure of air to the engine and/or a desired or specified compressor efficiency. The electric machine 202 can be used to electro assist operation of the turbocharger, i.e., drive the electric machine 202 to assist the turbine in rotating the shaft 204 and/or brake the shaft 204 with the electric machine 202 to achieve the desired or specified engine operating efficiency and/or desired or specified compressor efficiency. For example, at a given engine operating condition, the available exhaust alone may not be enough to rotate the compressor 206 fast enough to achieve a desired or specified (e.g., maximum) engine efficiency. The electric machine 202 may be powered to assist the turbine in rotating the compressor 206 faster, and fast enough to achieve the desired or specified engine efficiency at the given operating condition. In another example, at a given engine operating condition, the available exhaust alone may operate the compressor 206 in stall. Power can be supplied to the electric machine 202 or the electric machine 202 operated to generate power to brake the rotating compressor 206 to a rotational rate that produces stable pressure generation. In yet another example, power can be supplied to the electric machine 202 to assist or brake rotation of the compressor 206 to maintain the compressor at a desired or specified (e.g., maximum) compressor efficiency over different exhaust production of the engine and/or different ambient conditions. By assisting or braking the rotation of the compressor 206 using the electric machine 202, the engine and/or the compressor 206 can be maintained at desired or specified operational efficiencies regardless of the exhaust produced by the engine and ambient conditions. In instances where an auxiliary blower is provided to supply additional compressed air to the engine (beyond what the turbocharger would normally), the electric machine 202 can operate the compressor 206 to supplement the operation of the auxiliary blower or can enable omitting the auxiliary blower.
Some engines with turbochargers are optimized to run for extended periods of time at a specified steady state engine operating conditions. When the engine operation departs from the specified, optimum steady state engine operating conditions, the efficiency of the engine operation drops and in some cases, drops substantially. Some examples of engines optimized to run for extended periods of time at specified steady state operating conditions include engines used for marine propulsion, engines used for generating power in rail applications, stationary engines such as used for running generators, pumps or compressors, and/or other engines. By assisting or braking the rotation of the compressor 206 using the electric machine 202, the amount of air supplied by the turbocharger system 200 can be adjusted based on engine requirements, rather than based on available exhaust for operating the turbine, to improve (and sometimes maximize) engine operating efficiency at operating conditions different from the specified, optimum steady state engine operating conditions. For example, in the context of a marine propulsion engine, the turbocharger system 200 described above would allow the vessel to cruise at differing speeds above and below the cruising speed associated with the specified, optimum steady state engine operating conditions while still maintaining a high engine operating efficiency. One measure of engine operating efficiency is fuel efficiency. Operating the turbocharger system 200 as described above can improve fuel efficiency of the engine operation across multiple operating conditions of the engine above and below the specified, optimum engine operating conditions. In improving fuel efficiency, emissions can also be decreased.
During transient operation, the exhaust to the turbocharger system 200 lags, in time, the engine loading and speed events that cause the engine to generate exhaust. This lag, together with a lag resulting from accelerating the inertial mass of the rotating assembly, delays the operation of the compressor 206 in generating a desired or specified flow and pressure of air to the engine. Power can be supplied to the electric machine 202 to assist in accelerating the compressor 206 and/or brake the compressor 206 more quickly and independently from the exhaust production to reduce lag.
At startup, power can be supplied to the electric machine 202 to turn the compressor 206 to supply compressed air to the engine to facilitate start-up, even though little or no exhaust is being produced. In instances where a supplemental start-up booster compressor is used to facilitate engine start-up, the electric machine 202 rotating the compressor 206 can supplement, and in some instances, supplant the supplemental start-up booster.
In certain instances, a controller 232 can include a control algorithm for controlling the turbocharger system 200 to supply air to the engine based on engine demands, for example, to achieve a desired or specified engine operation (e.g., maximum efficiency), regardless of the exhaust available to operate the turbocharger system 200. The controller 232 can include a number of inputs, including one or more engine operating parameters (e.g., engine speed, throttle position, engine load, compressor speed and/or other operating parameters). The control algorithm can cover start-up, transient operation and/or steady state operation. The controller 232 can be pre-programmed with a map of compressor 206 operation to engine operating condition and/or the controller 206 can adaptively derive the operation of the compressor 206 based on engine operating conditions. The controller 232 can be coupled to the power electronics 230 to operate the power electronics 230 in operating the electric machine 202.
In certain instances, the electric machine 202 can be powered by excess exhaust to generate power. For example, at some engine operating conditions, typically high load and high speed, the amount of exhaust available to drive the compressor 206 is more than is needed to operate the engine at the operating conditions. As mentioned above, this excess exhaust is normally vented by a wastegate valve (e.g., wastegate valve 20 of
As discussed above, in certain aspects, the turbocharger system can be operated to decrease fuel consumption and emissions across multiple operating conditions of the engine above and below the engine's optimum engine operating conditions. For example, the engine can be operated at part load, yet with higher fuel efficiency and lower emissions that it would have with a conventional turbocharger.
In certain aspects, the turbocharger system can be controlled to control back pressure of the engine. For example, the turbocharger system can be operated to reduce back pressure of the engine. Reducing back pressure helps with a cleaner scavenge cycle in a two stroke engine.
In certain aspects, the turbocharger system can supplement or eliminsate the need for auxiliary blowers or compressors that supply air to the engine, including auxiliary blowers used to supplement turbocharger operation and/or start-up booster compressors used to facilitate engine start-up.
In certain aspects, the electric machine can be provided without any bearings, making it easier to incorporate an electric machine to an existing turbocharger design and making the system lower cost than if a bearing were provided in the electric machine. Furthermore, the electric machine efficiency can be higher because there are no bearing frictional losses.
In certain aspects, the electric machine enables rotating the rotating assembly of the turbocharger system so that it can be balanced without having to remove the turbocharger system from the engine. Further, rotating the rotating assembly when the engine is not in use can clean the compressor and/or turbine blades, and can pressurize the engine to clean deposits from inside the engine. Even during operation, the rotating speed of the turbocharger system can be controlled to promote cleaning the compressor and/or turbine blades. Also, motoring the rotating assembly can smooth out cyclical operating speeds that fatigue the compressor and turbine, and therefore, reduce fatigue stresses.
In certain aspects, the electric machine can be cooled without any active cooling, only by the intake air flowing through and/or around the electric machine and the conductive heat transfer with the housing of the turbocharger system. In certain aspects, additional liquid cooling can be provided in the housing of the electric machine.
A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made. Accordingly, other implementations are within the scope of the following claims.
This application claims the benefit under 35 U.S.C. §119(e) of U.S. Patent Application No. 61/611,809, entitled “Turbo Assist,” filed Mar. 16, 2012, which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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61611809 | Mar 2012 | US |