An improved, lightweight, turbine housing unit for an intermittent combustion reciprocating internal combustion engine turbocharger is prepared from a lay-up or molding of carbon-carbon composite materials in a single-piece or two-piece process. When compared to conventional steel or cast iron, the use of carbon-carbon composite materials in a turbine housing unit reduces the overall weight of the engine and reduces the heat energy loss used in the turbocharging process. This reduction in heat energy loss and weight reduction provides for more efficient engine operation

Northam, G. Burton

Ransone, Philip O.

Rivers, H. Kevin

English

NASA Technical Reports Server

I11111 111ll Il1 Il11 III III III Il11 III III 1ll111111 
US005 8 1055 6A 
United States Patent [19] [ i l l  Patent Number: 5,810,556 
Northam et al. [45] Date of Patent: Sep. 22,1998 
[54] CARBON-CARBON TURBOCHARGER 
HOUSING UNIT FOR INTERMITTENT 
COMBUSTION ENGINES 
[75] Inventors: G. Burton Northam, Carrollton; Philip 
0. Ransone, Gloucester; H. Kevin 
Rivers, Hampton, all of Va. 
[73] Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 811,378 
[22] Filed: Mar. 4, 1997 
Related U.S. Application Data 
[60] Provisional application No. 601012,940 Mar. 6, 1996. 
[51] Int. C1.6 ...................................................... F04D 29/44 
[52] U.S.Cl. .............................................................. 415/200 
[58] Field of Search ............................................... 4151200 
~561 References Cited 
U.S. PATENT DOCUMENTS 
4,683,809 811987 Taylor . 
4,736,676 411988 Taylor . 
4,909,133 311990 Taylor. 
5,083,537 111992 Onofrio et al. . 
5,370,087 1211994 Guimond et al. . 
Primary Examiner-John T. Kwon 
Attorney, Agent, or F i r m q e r o g e  F. Helfrich 
[571 ABSTRACT 
An improved, lightweight, turbine housing unit for an inter- 
mittent combustion reciprocating internal combustion 
engine turbocharger is prepared from a lay-up or molding of 
carbon-carbon composite materials in a single-piece or 
two-piece process. When compared to conventional steel or 
cast iron, the use of carbon-carbon composite materials in a 
turbine housing unit reduces the overall weight of the engine 
and reduces the heat energy loss used in the turbocharging 
process. This reduction in heat energy loss and weight 
reduction provides for more efficient engine operation. 
6 Claims, 2 Drawing Sheets 
20 
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https://ntrs.nasa.gov/search.jsp?R=19990008549 2020-06-18T00:40:25+00:00Z
U S .  Patent Sep. 22, 1998 Sheet 1 of 2 
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FIG. la  
PRIOR ART 
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5,810,556 
FIG. l b  
PRIOR ART 
U S .  Patent Sep. 22, 1998 Sheet 2 of 2 
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FIG. 2a 
5,810,556 
FIG. 2b 
5,810,556 
1 
CARBON-CARBON TURBOCHARGER 
HOUSING UNIT FOR INTERMITTENT 
COMBUSTION ENGINES 
C W M  OF BENEFIT OF PROVISIONAL 
APPLI CAT1 ON 
Pursuant to 35 U.S.C. $119, the benefit of priority from 
provisional application No. 601012,940, with a filing date of 
Mar. 6, 1996 is claimed for this non-provisional application. 
ORIGIN OF THE INVENTION 
The invention described herein was made by an employee 
of the United States Government and may be manufactured 
and used by or for the Government for governmental pur- 
poses without the payment of any royalties thereon or 
therefor. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an improvement in a turbo- 
charger for an intermittent combustion (IC) internal com- 
bustion engine and a process therefor, and more specifically 
to an improved turbine housing unit for said turbocharger 
which is fabricated from a lay-up or molding of carbon- 
carbon composite materials. 
2. Description of the Related Art 
Many intermittent combustion (IC) reciprocating engines 
are equipped with turbochargers, to improve engine effi- 
ciency. Typically, turbochargers consist of three principal 
components: a turbine, a compressor, and a turbine housing 
unit. In operation, the turbine captures high-temperature 
gases coming from the engine exhaust manifold. These 
exhaust gases then are used to drive a compressor which, in 
turn, pumps high pressure air into the engine’s inlet and 
compression chambers. 
The effect of this process in a gasoline engine is to 
increase the volume of air available for combustion. Because 
more air is available, a correspondingly greater amount of 
fuel can be consumed, or burned, per cycle. In theory, the 
greater the fuel burned, the greater the horsepower. For 
diesel engines, the expansion of the high-temperature 
exhaust gases through the turbine connected to the com- 
pressor leads to more efficient operation because the inlet air 
charge is also increased leading to a higher compression 
ratio in the compression chambers. As these high- 
temperature exhaust gases would otherwise be expelled 
from the engine through an exhaust system, capturing and 
using the kinetic and thermal energy from the exhaust gases 
increases overall engine efficiency and horsepower. In an 
expansion cycle, the exhaust gas turbine can also be coupled 
to the engine drive train to increase cycle efficiency. 
Internal combustion reciprocating engines used for 
aerospace, military, and transportation applications must be 
lightweight and capable of operating at elevated tempera- 
tures and pressures. Under the current state-of-the-art, tur- 
bocharger turbine housing units and gas exhaust manifolds 
for gasoline and diesel engines are made of steel, cast iron, 
Ni-resistant iron, or ductile iron with ceramic liners. Turbo- 
charger turbine housing units fabricated from steel or iron 
are relatively heavy. Excessive weight is detrimental to 
engine efficiency and prohibitive in aerospace applications. 
Hence, a lightweight alternative to steel or iron turbine 
housing units would be a highly desired improvement in the 
prior art. 
Likewise, steel and iron inherently possess excessive 
thermal conductivity which increases heat energy loss. As 
2 
the captured gas heat energy dissipates, less energy is 
available to drive the turbocharger turbine, thereby reducing 
the performance and efficiency of the turbine. In addition, in 
compound diesel engines, the heat energy loss of the high- 
s temperature exhaust gases reduces cycle efficiency. 
Consequently, a less thermally conductive substitute for 
steel or iron would be a highly-desired improvement in the 
prior art. 
While Ni-resistant iron is lighter than steel or cast iron, it 
is very expensive. Likewise, ductile iron is lighter than steel 
or cast iron, yet it remains relatively heavy overall. Afurther 
disadvantage of ductile iron turbocharger turbine housing 
units is disclosed in U.S. Pat. No. 5,456,578 (Honda et al.). 
According to Honda et al., “[wlhen ductile iron material is 
used for a turbine housing [I, the surface of the ductile 
housing is oxidized and deteriorated by the heat of the 
high-temperature exhaust gas.” In some instances such dete- 
rioration exerts “an especially great influence on [engine] 
efficiency” either because the clearance between the turbine 
rotors and the turbine housing unit allows the high- 
temperature gases to escape, or because the turbine housing 
unit itself is “insufficiently sealed.” Therefore, a lightweight 
alternative to steel and iron turbine housing units which is 
neither oxidized nor deteriorated by the heat of the high- 
temperature engine exhaust gases would be a highly-desired 
improvement in the prior art. 
SUMMARY OF THE INVENTION 
Accordingly, an object of this invention is to reduce the 
weight of an IC internal combustion reciprocating engine. 
It is another object of the present invention to minimize 
the loss of engine exhaust gas heat energy, to improve the 
engine cycle efficiency. 
It is still another object of the present invention to coat the 
surface or near surface of a turbine housing unit and/or the 
surface or near surface of any exhaust gas ducting with a 
sealant, to provide protection from oxidation. 
It is a further object of the present invention to provide a 
process for fabricating a turbine housing unit and exhaust- 
According to the present invention, the foregoing and 
additional objects are attained by fabricating a turbocharger 
turbine housing unit and exhaust gas duct-work for an 
internal combustion engine from a lay-up or molding of 
Carbon-carbon composite materials were developed for 
high temperature and high strength aerospace applications. 
Carbon-carbon composites are inherently lightweight; main- 
tain their strength at elevated temperatures (i.e. up to 2500 
so degrees Fahrenheit); and can be manufactured with low 
coefficients of thermal expansion, low specific heat, and 
tailorable thermal conductivity. 
Carbon-carbon composite materials, as used herein, refer 
to a predominantly carbon matrix material reinforced with 
5s predominantly carbon fibers, and are well known to the art. 
The properties of these materials may be tailored to produce 
the desired mechanical and physical properties by preferred 
orientation of the continuous or staple fibers in the compos- 
ite; and/or by the selection of additives or metric precursors; 
60 and/or by thermal treatment of the fibers and matrix before, 
during, or after fabrication. Carbon-carbon composite mate- 
rials may be cast, molded, or laid up, and are machineable. 
The surface or near-surface of carbon-carbon composite 
materials also can be treated and/or coated with a sealant or 
The use of low thermal inertia carbon-carbon composite 
materials for turbocharger turbine housing units and exhaust 
1s 
20 
2s . 
30 
3s 
4o gas duct-work. 
4s carbon-carbon composite materials. 
65 coating, to protect against oxidation. 
5,810,556 
3 
duct piping, i.e. the duct-work between the engine exhaust 
valves and the turbocharger as well as the duct-work 
between the turbocharger and the engine intake valves, in IC 
internal combustion reciprocating engines reduces engine 
weight and reduces exhaust gas heat. It is also possible to 
improve the response time of the turbocharger. 
Consequently, use of carbon-carbon composite materials in 
fabricating IC internal combustion reciprocating engines 
significantly improves engine cycle efficiency and poten- 
tially produces a more responsive turbocharger by minimiz- 
ing heat energy loss. 
By coating the surface or near-surface of the turbine 
housing unit, which is subject to the high-temperature 
engine exhaust gases, protection from oxidation and dete- 
rioration is detected. Metallic coatings of silicon, or ceramic 
coatings of silicon carbide or silicon nitride effectively 
protect carbon-carbon composite materials from oxidation. 
BRIEF DESCRIPTION OF THE DRAWINGS 
FIGS. 1A and 1B are the illustration of a turbocharger of 
the prior art which are fabricated from steel or cast-iron; and 
FIGS. 2A and 2B are the illustration of a turbocharger 
according to the present invention which are fabricated from 
carbon-carbon composite materials 
DETAILED DESCRIPTION OF THE 
INVENTION 
A typical steel or cast-iron turbocharger turbine housing 
unit 10 for a gasoline or diesel engine of the prior art is 
depicted in FIG. 1 in both plan 11 and side 12 views. 
Typically, the turbine housing unit 10  consists of a single 
piece which is either cast or molded. The turbine housing 
unit 10 is internally contoured to provide the required gas 
flow vector to the turbine compressor and to reduce pressure 
losses which decrease efficiency. 
In contrast, FIG. 2 depicts a turbocharger turbine housing 
unit 20 fabricated from carbon-carbon composite materials 
according to the present invention. Turbine housing unit 20 
consists either of a single- or a two-piece configuration. The 
single-piece configuration differs from the prior art only in 
the materials used and by the process of manufacture. The 
two-piece configuration, however, is new to the art and 
involves joining a right turbine housing unit half 2 1  to a left 
turbine housing unit half 22 at a parting line 25. The turbine 
housing unit halves 21,22 are clamped, banded, or bonded 
to form an integral unit. 
One embodied method of manufacture according to the 
present invention consists of laying up carbon-carbon com- 
posite materials about an internal mandrel. Internal mandrels 
are designed to provide any desired aerodynamic shape to 
the inside of the turbine housing unit and are known to the 
art. Internal mandrels should be fabricated from materials 
which retain their shape during the lay-up or molding 
process, but which also can be burned out or washed out 
once the turbine housing unit has been formed. For this 
purpose, internal mandrels of wood sand, and/or Styro- 
foam@ are suitable. 
The lay-up process is performed manually, to produce a 
single-piece or a two-piece turbine housing unit. The manual 
lay-up process involves stacking prepregged carbon fabric 
layers over an internal mandrel to form a laminated turbine 
housing unit preform; heating the laminated preform to fuse 
the fabric layers together and to cure the carbonaceous 
matrix resin; pyrolizing the laminated preform to drive off 
hydrocarbons and to burn-out the internal mandrel; and 
S 
10 
1s 
20 
2s 
30 
3s 
40 
4s 
so 
5s 
60 
65 
4 
re-impregnating the preform with a carbonaceous resin 
system as necessary to achieve the desired density. The 
density is also improved by vapor deposition. 
To protect against oxidation, the inside surfaces of turbine 
housing unit are sealed or coated with a ceramic, such as 
silicon carbide or silicon nitride, or a metallic material. 
During the initial step of stacking the prepregged carbon 
fabric layers over the internal mandrel, the molded preform 
is most effective when the fabric layers are densifed as they 
are laid-upon during this initial step as with a vacuum bag. 
As an alternate to a vacuum bag for a two-piece turbine 
housing unit, a rubber plug may be used to densify the 
prepregged carbon fabric layers. After the prepregged car- 
bon fabric layers are stacked over the internal mandrel, a 
rubber plug is placed over the fabric layers and a steel or cast 
iron plate is secured to the internal mandrel so as to confine 
the prepregged carbon fabric layers and the rubber plug 
therebetween. When this preform is heated to cure the 
matrix resin, the rubber plug expands and compresses the 
prepregged carbon fabric layers together, i.e. densifies the 
prepregged carbon fabric layers. 
A more economical, and a more preferred embodiment of 
the present process of manufacture consists of a two-piece 
turbine housing unit which is fabricated by molding carbon- 
carbon composite materials. The two-piece molding process 
is preferred over manual laying-up as it eliminates time- 
consuming manual fabrication and because additional 
re-densification is not necessary. In the molding process, the 
steps of manufacture include molding carbon-carbon about 
an internal mandrel to form a laminated turbine housing unit 
preform; heating the laminated preform to fuse the fabric 
layers together and to cure the carbonaceous matrix resin; 
and pyrolizing the laminated preform to drive off hydrocar- 
bons. To protect against oxidation, the inside and/or outside 
surfaces of turbine housing unit are sealed or coated with a 
ceramic, such as silicon carbide or silicon nitride, or a 
material, such as silicon. 
The invention can be practiced in other manners than are 
described herein without departing from the spirit and the 
scope of the appended claims. 
What is claimed is: 
1 .  In a turbocharger which is operatively associated with 
an intermittent combustion reciprocating engine for enhanc- 
ing the efficiency thereof, the turbocharger including a 
housing unit for a turbine, a turbine which captures high 
temperature gases coming from an exhaust manifold of the 
engine, and a compressor which is driven by the high 
temperature gases and which pump high pressure air into an 
inlet and compression chambers of the engine; the improve- 
ment therein which comprises employing a turbine housing 
unit which is fabricated from carbon-carbon composite 
materials. 
2. The turbocharger of claim 1,  wherein the turbine 
housing unit fabricated from carbon-carbon composite 
materials has an inside surface and an outside surface which 
are coated with a sealant to provide protection from oxida- 
tion. 
3. The turbocharger of claim 2, wherein the sealant is a 
ceramic coating. 
4. The turbocharger of claim 3, wherein the ceramic 
coating consists of silicon carbide. 
5 .  The turbocharger of claim 3, wherein the ceramic 
coating consists of silicon nitride. 
6. The turbocharger of claim 2, wherein said sealant is a 
metallic coating. 
* * * * *  


Carbon-Carbon Turbocharger Housing Unit for Intermittent Combustion Engines

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