Abstract:
In accordance with various embodiments of the present invention, a system and method are provided for converting a conventional automobile engine into a gas compressor. In various embodiments, the system and method may provide an economical and efficient gas compressor by modification of a balance-opposed internal-combustion engine to provide a balance-opposed gas compressor. More specifically, in some embodiments, the modification may include a uniquely designed cylinder head adapted to convert an automobile engine into a gas compressor for the recovery, gathering, transfer, or staged compression of natural gas. In one embodiment, a four-cylinder balance-opposed engine is utilized.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/290,742, filed Dec. 29, 2009, the entire contents of which are hereby incorporated by reference as if fully disclosed herein. 
    
    
     BACKGROUND 
     1. Technical Field 
     This invention relates in general to the field of compressors, and more particularly, but not by way of limitation, to systems and methods for utilizing and/or modifying portions of a conventional automobile engine for use as a gas compressor. 
     2. Background 
     Gas compressors are used in various applications where either higher pressures or lower volumes of gas are needed, such as, for example, in petroleum refineries, natural gas processing plants, petrochemical and chemical plants, and similar large industrial plants for compressing intermediate and end product gases, and in pipeline transport of purified natural gas from the production site to the consumer. Often, compressors in these environments are driven by a gas turbine which may be fueled by a gas bled from the pipeline, thus, no external power source is necessary. 
     Pumps for liquid pipelines and compressors for gas pipelines are often located at compressor stations along the pipeline to facilitate the transportation of product through the pipelines. The location of these stations may be defined by the topography of the terrain, the type of product being transported, and/or operational conditions of the network. For example, natural gas, while being transported through a gas pipeline, needs to be constantly pressurized, requiring compressor stations to be located in certain distance intervals along the pipe ranging anywhere from 40 to 100 miles or more. Oftentimes, specially customized turbines, motors, and/or engines are required in each of these compressor stations, which may be in remote locations. 
     One type of compressor often used along a gas pipeline is a reciprocating compressor. A reciprocating compressor or piston compressor is a positive-displacement compressor that uses pistons driven by a crankshaft to deliver gases at high pressure. The intake gas enters a suction manifold, then flows into the compression cylinder where it is compressed by a piston driven in a reciprocating motion via a crankshaft before being discharged back into the pipeline. Reciprocating compressors can be either stationary or portable, can be single or multi-staged, and can be driven by electric motors or internal combustion engines. Small reciprocating compressors from 5 to 30 horsepower (hp) are commonly seen in automotive applications and are typically limited to intermittent duty. Larger reciprocating compressors, well over 1,000 hp (750 kW) and capable of very high discharge pressures (e.g., &gt;6000 psi or 41.4 MPa), are commonly found in large industrial and petroleum applications. 
     In the past, these types of large industrial compressors have been utilized for the compression of gas for use in recovery, gathering, transfer, and/or storage of natural gas. There are various potential benefits to using these large industrial compressors including accessibility to the interior areas of the compressor for maintenance purposes such as, for example, removable access panels and/or easily removable major components. Oftentimes, maintenance access options are not available in smaller compressors. However, these large industrial compressors are not practical for field use for various reasons, including, for example, cost, weight, size, and hp requirements. 
     Various prior art devices currently in use for gas compression include modified devices from other industries. In some devices, industrial compressors, such as industrial horizontal compressors, are converted for use in natural gas compression. One drawback to the use of this type of compressor for natural gas compression is that it requires a specialized manufacturer to manufacture modified parts for conversion to a natural gas compressor. In addition, the extensive modifications also require specially manufactured components for use, maintenance, and repairs, which greatly increases the operating cost of such devices. 
     In other prior art devices, compressors have been formed utilizing modified automotive engines to provide both power to the device and compression. However, utilization of such mono-block designs to compress natural gas may be considered to involve some operational risks because of the proximity of the cylinders having combustion therein and the cylinders having a flammable material such as natural gas flowing therethrough. One prior art device, as disclosed in U.S. Pat. No. 5,267,843, which is hereby incorporated by reference, attempts to overcome this danger with a complicated venting systems to vent any gas that might build up in the compressor. 
     Many of the prior art devices for utilizing an internal combustion engine as a compressor contemplate converting an automobile engine having a V-shaped configuration, such as for example, a V-8 engine, into a compressor. However, there are various deficiencies inherent to the V-shaped orientation of the cylinders of, for example, a V-8 engine relative to use as a compressor. One prior art device, as disclosed in U.S. Pat. No. 4,700,663, which is hereby incorporated by reference, attempts to overcome some of these deficiencies by utilizing a modified horizontally opposed engine, such as the Type-1 VOLKSWAGEN internal combustion engine, to form an air compressor. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a system and method are provided for utilizing and/or modifying a conventional automobile engine into a gas compressor. In various embodiments, the system and method may provide an economical and efficient gas compressor by modification of a balance-opposed internal-combustion engine to provide a balance-opposed gas compressor. For example, in one embodiment, the balance-opposed engine may be a VOLKSWAGEN engine, such as a Type 1, 1600 cc, four cylinder engine. More specifically, in some embodiments, the modification may include a uniquely designed cylinder head adapted to convert an automobile engine into a gas compressor for the recovery, gathering, transfer, or staged compression of natural gas. 
     The above summary of the invention is not intended to represent each embodiment or every aspect of the present invention. Particular embodiments may include one, some, or none of the listed advantages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the method and apparatus of the present invention may be obtained by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings wherein: 
         FIGS. 1A-1C  are various views of a gas compressor formed from a balance-opposed automobile engine; 
         FIG. 2  is a cut-away side view of a cylinder assembly of the gas compressor of  FIGS. 1A and 1B ; 
         FIGS. 3A-3C  are various views of a cylinder head of the cylinder assembly of  FIG. 2 ; 
         FIGS. 4A and 4B  are front and back perspective views of the cylinder head of the cylinder assembly of  FIG. 2 ; and 
         FIGS. 5A and 5B  are perspective views of a suction and a discharge valve of the cylinder assembly of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments of the present invention will now be described more fully with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, the embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
     Referring now to  FIGS. 1A-1C  collectively, various views of an embodiment of a gas compressor  100  are shown in accordance with the present invention. In the embodiment shown, the gas compressor  100  has been formed from a four-cylinder balance-opposed internal-combustion engine having pistons that reciprocate in cylinders disposed in a horizontal plane. A flat engine, or horizontally-opposed engine, is an internal combustion engine with multiple pistons that all move in the horizontal plane. A four-cylinder horizontally opposed is a flat engine with four cylinders arranged horizontally in two banks of two cylinders on each side of a central crankcase. As will be explained in more detail below, the automobile engine from which the gas compressor  100  has been formed has four cylinders  102 A- 102 D, where a first bank of two cylinders  102 A and  102 B is disposed on one side of the gas compressor  100  and a second bank of two cylinders  102 C and  102 D is disposed on an opposite side of the gas compressor  100  with a crankshaft  107  (shown in  FIG. 1B ) disposed therebetween. The pistons are usually mounted on the crankshaft such that opposing pistons move back and forth in opposite directions at the same time. The configuration results in inherently good balance of the reciprocating parts. 
     It should be noted that the crankshaft may be coupled and or adapted to be coupled to an external power source in a number of ways. For example, one method of coupling a compressor to an external power source, such as an internal combustion engine, is disclosed in U.S. Pat. No. 6,176,690, which is hereby incorporated by reference. 
     Still referring to  FIGS. 1A-1C  collectively, in various embodiments, the gas compressor  100  may utilize a modified head assembly  104  in conjunction with various unmodified components from the original automobile engine for ease of maintenance and parts replacement. As can be seen, the original engine block  101  may be maintained with the modified head assembly  104  mounted peripheral to the cylinders  102  allowing ease of conversion from an internal combustion engine to a gas compressor. During maintenance, this configuration allows ease of disassembly and access to all major components of the gas compressor  100  for inspection, maintenance, and repair. While modification of an automobile engine via, among other things, replacing a head thereof may be economical in limited production, in large production, it may be economical to utilize an engine block or portions thereof designed for use as a gas compressor. 
     Still referring to  FIGS. 1A-1C  collectively, the gas compressor  100  may be adapted to utilize all four of the cylinders  102 A- 102 D of the automobile engine for compression. In prior art embodiments, one or more cylinders of an internal combustion engine were used to power the gas compressor, leaving less than all of the cylinders available for gas compression. To increase the volume of gas capable of being compressed, the gas compressor  100  utilizes an external power source to rotate the crankshaft rather than using any of the cylinders to provide power. In the embodiment shown, the gas compressor  100  may include two modified head assemblies  104 , wherein each of the first bank of cylinders ( 102 A and  102 B) and second bank of cylinders ( 102 C and  102 D) are coupled to a common modified head assembly  104 . While various embodiments may utilize some of the cylinders for gas compression and some to power the gas compressor  100 , utilizing a separate power source may be beneficial in some embodiments to increase the volume of gas capable of being compressed and/or to keep the natural gas being compressed separate from sparks or other flames of a typical internal combustion engine. 
     Referring now to  FIG. 2 , a side view of one cylinder  102  of the gas compressor  100  of  FIGS. 1A and 1B  is shown having a modified head assembly  104  mounted thereto. In the embodiment shown, the cylinder  102  includes a piston  106  reciprocally disposed therein, the piston  106  having a first end  106 A adapted to be connected to the crankshaft and a piston head disposed at a second end  106 B thereof. As explained in more detail below, in various embodiments, the modified head assembly  104  may include a head  108  having an inlet port disposed on a top surface thereof and an outlet port disposed on a bottom surface thereof. The modified head assembly  104  may also include a suction valve  110  disposed therein, which is secured in place by a suction valve chair  111  and a discharge valve  112 , which is secured in place by a discharge valve chair  113 . The suction valve chair  111  and the discharge valve chair  113  may be mounted to the head  108  via mounting studs and nuts  114 . 
     Still referring to  FIG. 2 , as known to those skilled in the art of internal combustion engines, the rotation of the crankshaft  107  (shown in  FIG. 1B ) produces a reciprocating motion to the connecting rods of the piston  106 . When the piston  106  travels away from the head  108 , a vacuum is formed inside of the cylinder  102 . This vacuum effect sucks gas through an opening in the suction valve chair  111  which is mounted at the top of the head  108  and past the suction valve  110  and into the cylinder  102 . The suction valve  110  may be, for example, a one-way spring-actuated disc valve. Upon the return travel of the piston  106  towards the modified assembly head  104 , the gas is compressed and forced out of the cylinder  102  through the discharge valve  112  and through an opening in the discharge valve chair  113 . Upon the clearance of the opening in the discharge valve chair  113 , the gas continues its exhaust path out of the modified head assembly  104  via the outlet port. 
     Referring now to  FIGS. 3A-3C , various views of head  108  of  FIG. 2  are shown. Referring specifically to  FIG. 3A , a view of an inside surface of the head  108  can be seen. When mounted to the engine block  101 , the inside surface of the head  108  is adapted to abut the cylinders  102  and the two piston receiving bores (marked as “E”) are adapted to align with the piston  106  disposed therein. Referring now specifically to  FIG. 3B , a view of an outside surface of the head  108  can be seen. Suction valve receiving bores (marked as “C”) and discharge valve receiving bores (marked as “D”) can be seen disposed on an outside surface of the head  108 . Referring now to  FIG. 3C , a side view along line A-A of  FIG. 3B  is shown. As can be seen from this view and as will be described in more detail below, a flowpath can be seen from suction valve receiving bore C through piston receiving bore E to discharge valve receiving bore D. In various embodiments, the head  108  has been designed to be able to handle more than 500 psi as compared to various other prior art devices that typically can only handle up to 120 psi. In some embodiments, two modified head assemblies  104  may be utilized in conjunction with a four-cylinder engine, where the discharge port B of one modified head assembly  104  is coupled to the suction port A of the other modified head assembly  104 . In that way, additional compression may be provided via the two stages of compression. 
     Referring now to  FIGS. 4A-4B , various views of head  108  of  FIG. 2  are shown. As can be seen from these view in combination, when the piston (not shown) retreats from the head  108 , gas from, for example, a gas supply line enters the head  108  via a single suction port (marked as “A”) disposed on a top surface thereof. The gas then flows from the suction port and into the two suction valve receiving bores C. From there, the gas then passes through each suction valve  110  (shown in  FIG. 2 ) and into the corresponding cylinder  102  (not shown). When the piston advances towards the head  108 , the gas is compressed and the compressed gas flows out of the cylinder  102  through the corresponding discharge valves (not shown) and into the discharge valve receiving bores D. The gas then flows from the discharge valve receiving bores D and out the single discharge port (marked “B”) disposed on a bottom surface of the head  108 . In various embodiments, the discharge valves location is such that it enables the cylinder to discharge condensation during run time and eliminates buildup of condensate in the cylinders during down time. This is achieved by the natural gas exiting the cylinders at a lower level than the cylinder creating a venturi effect on any fluid contained therein, thus any condensate is carried out with the gas. 
     Referring now to  FIGS. 5A and 5B , perspective views of a suction chair  111  and a discharge chair  113  are shown. The chairs  111  and  113  may be disposed in the head  108  to secure the suction and discharge valves disposed therein. 
     Although various embodiments of the method and apparatus of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications, and substitutions without departing from the spirit and scope of the invention.