Patent Application
20240425192
This application relates to providing acoustic arrangements to reduce exhaust noise in a turbo-compounded engine.
Engines for aircraft applications typically include a propulsor. In some engines a fan is used and in others a propeller.
One type of engine that is showing some promise is a turbo-compounded engine. In a turbo-compounded engine there is typically a piston engine driving the propulsor. Exhaust products downstream of the piston engine pass across a turbine. The rotation of the turbine drives a shaft that also provides propulsion to the propulsor.
Such engines are provided with relatively long exhaust ducts to handle the noise that will be created. Further, the exhaust duct shape needs to fit particular installation challenges for a turboprop.
Another engine type is an auxiliary power unit (“APU”). These engines do not have a propulsor, but may use turbo-compounded engines. Such APU engines also have noise challenges.
In one type of turbo-compounded engine an electric motor also supplements the piston engine. The exhaust noise challenges in such engines are particularly acute.
A turbo-compounded engine includes a piston engine connected to drive a propulsor. An outlet of the piston engine is operable to connect products of combustion from the piston engine to pass over a turbine. The turbine is connected to drive a turbine shaft also connected to drive the propulsor. An outlet of the turbine is connected into an exhaust duct configured to exhaust the products of combustion. The exhaust duct is provided with an exhaust duct outer wall defining an exhaust chamber. A further cooling air outer wall is positioned outwardly of the exhaust duct. Flow dividers are received within an exhaust chamber inward of the exhaust duct outer wall. The exhaust duct outer wall has an inner surface and the flow dividers have an outer surface. Acoustic treatment is provided on both the inner surface of the exhaust duct outer wall and the outer surface of the flow dividers.
These and other features will be best understood from the following drawings and specification, the following is a brief description.
A turbo-compounded engine 100 is illustrated in
An electric motor 114 optionally drives a shaft 112 to provide rotational force into the compound gearbox 108.
A piston engine 116 drives a shaft 118 to also provide a source of rotation into the gearbox 108. It is known that the electric motor can provide additional power in combination with the piston engine 116 under certain operational conditions such as high power conditions. As an example, at takeoff both the electric motor 114 and the piston engine 116 may be utilized. At lower power conditions, such as cruise, perhaps only the electric motor 114 is used.
A compound gearbox 123 receives rotation from a shaft 121. An exhaust 120 from the piston engine 116 passes across a turbine 122. The turbine 122 drives the shaft 121 through the gearbox 123 to provide additional rotational force to shaft 118. The turbine 122 is also shown driving a compressor 124. The compressed air from compressor 124 passes through a heat exchanger 125 and then to the piston engine 116 through line 127.
The operation of the engines 100 and 116 may be as known.
It is also known that a turbo-compounded engine could have a piston engine with a plurality of engines such as engine 116 as shown in
As mentioned above, there are challenges with exhaust noise in such engines, because of the pulsation nature of the rotary core.
While a propulsor is shown, the teachings of this disclosure extends to turbo-compounded engines in non-propulsor applications, such as APUs.
Another portion of the air is pumped into an inlet 148 defined between the housing 144 and an outer exhaust housing 146. That air passes downstream and through an ejector opening 158.
The products of combustion leaving the engine 100 enter a chamber 161 inward of housing 146 and provide a jet pump at an exit 156 of the housing 146.
The housing 146 may be thought of as an S-duct arrangement. There is a radially inner first generally axially extending portion 150 leading into a radially outwardly extending portion 152, which then merges into a second generally axially extending portion 154.
The first generally axially extending portion 150 extends axially away from the engine 100 with a component in an axial direction defined by the rotational axis X of the engine. The axial component is greater than a radial component of its direction.
The first generally axially extending portion 150 merges into radially extending portion 152. The radially extending portion 152 merges into the second generally axially extending portion 154.
Portion 154 extends along a direction with a component in an axial direction that is greater than a radial component.
The radially extending portion 152 extends with an axial component but also having a radial component that is greater than the radial component in both the first and second axially extending portion 150/154.
In an engine such as engine 100, the S-duct must be made relatively long to provide sufficient area for exhaust noise mitigation and reduce exhaust noise. This is particularly true when an electric motor 114 is utilized in the engine 100.
Applicant has recognized that breaking the exhaust gas flow in chamber 161 in subportions will help reduce the noise leaving the exhaust duct exit 156.
Thus, a flow divider is provided by a center bullet 160 and struts 162.
As shown in
Alternatively,
An acoustic treatment 370 as shown in
The treatments provided on the inner surface 147 may be any of these acoustic treatments, or any other acoustic treatments.
Possible wall treatments include passive types, such as fibrous, foam, ceramic, and filled cavity with a special handling of the treatment in a package.
Further, quarter-wavelength resonator type, Helmholtz resonators, single and double degree of freedom liners, made up of a perforated skin on honeycomb or partitions, volume tune liner types made up with fined tuned limited volumes on a top of which a perforated skin is bonded, where the perforations have a tuned size and number may all be used.
As shown in
The distance or the length of acoustically treated walls is a function of the level of attenuation needed. The total length is optimized along with the number of splitters and type of acoustic treatment.
A turbo-compounded engine 100 under this disclosure could be said to include a piston engine 116 connected to drive a propulsor 106. An outlet 120 of the piston engine is operable to connect products of combustion from the piston engine 116 to pass over a turbine 122. The turbine 122 is connected to drive a turbine shaft 121 also connected to drive the propulsor 106. An outlet of the turbine is connected into an exhaust duct 146 configured to exhaust the products of combustion. The exhaust duct 146 is provided with an exhaust duct outer wall 146 defining an exhaust chamber 161. A further cooling air outer wall 144 is positioned outwardly of the exhaust duct wall 146. Flow dividers are received within an exhaust chamber inward of the exhaust duct outer wall. The exhaust duct outer wall has an inner surface and the flow dividers have an outer surface. Acoustic treatments are provided on both the inner surface of the exhaust duct outer wall and the outer surface of the flow dividers.
Although an embodiment has been disclosed, a worker of ordinary skill in this art would recognize that modifications would come within the scope of this disclosure. Thus, the following claims should be studied to determine the true scope and content of this disclosure.
