Abstract:
A heat engine unit has a combustion chamber, the combustion chamber being in communication with a previous component of the heat engine unit, e.g., a compressor, a heat exchanger or a recuperator, at a first end, and in communication with subsequent stages of the heat engine unit at a second end. The combustion chamber comprises at least one part, and is allowed to expand when exposed to heat by being movably engaged at the first end. The combustion chamber is supported at the second end by way of a contact surface formed between the second end of the combustion chamber and supporting means to allow tilting of the combustion chamber.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a combustion chamber for a heat engine unit, the combustion chamber being in communication with a previous component of the heat engine unit, e g a compressor, a heat exchanger or a recuperator, at a first end, and in communication with subsequent stages of the heat engine unit at a second end.  
         PRIOR ART  
         [0002]    A gas turbine can be of an axial or radial type with one or more compressor and/or turbine stages, depending on the power and heat requirement, and available space. Different power requirements and heat outputs lead to different sizes and types of gas turbines. One feature often common for the different types of gas turbines is that a combustion chamber is provided either inside the gas turbine or externally. The most common way of increasing the efficiency of the gas turbine is to raise the temperature of the combustion air before it enters the combustion chamber, this is often done by interchanging the excess heat in the exhaust gas. The temperature in the combustion chamber is often high, whereby demands on sealings and heat expansion durability is high. The sealing problem during uneven heat expansion and heat distribution may be solved in many ways, one way is to design the combustion chamber with overlapping ends, wherein each end is designed with for example bulges corresponding to grooves in the adjacent surrounding surface allowing some movement before the sealing vanishes.  
           [0003]    This solution of a combustion chamber has a disadvantage, it does not allow any tilting of the combustion chamber, i e the overlapping parts has to keep an essentially parallel relation for ensuring a sufficient sealing. This allows only small movements for the combustion chamber for reducing gas leakage, when the combustion chamber is thermally strained, i e by heat expansion, during operation of the gas turbine unit.  
         SUMMARY OF THE INVENTION  
         [0004]    The main objects of the present invention are to simplify the construction, assembly and maintenance of combustion chambers in heat engine units, reduce the number of working moments during the assembly, and enhance the sealing of the combustion chambers during thermal strain.  
           [0005]    These objects are achieved for heat engine units by providing them with an combustion chamber according to the invention. The present invention relates to a combustion chamber for a heat engine unit, the combustion chamber being in communication with a previous component of the heat engine unit, e g a compressor, a heat exchanger or a recuperator, at a first end, and in communication with subsequent stages of the heat engine unit at a second end. The combustion chamber comprises at least one part, and the combustion chamber is allowed to expand when exposed to heat by being movably engaged at said first end. Furthermore, the combustion chamber is supported at said second end by way of a contact surface formed between said second end of the combustion chamber and supporting means to allow tilting of the combustion chamber.  
           [0006]    By providing a heat engine unit with a combustion chamber according to the invention, a simpler construction reduces associated working moments during assembly. Moreover, the contact surface formed between the combustion chamber and the supporting means permits tilting of the combustion chamber. Also, the installation and maintenance of the combustion chamber are simplified due to an easier procedure when changing combustion chambers.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    The present invention will now be described in further detail, reference being made to the accompanying drawings, in which:  
         [0008]    [0008]FIG. 1 is a side view in section showing a preferred embodiment of a combustion chamber according to the invention mounted in a heat engine unit. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0009]    [0009]FIG. 1 shows a combustion chamber  10  according to the invention mounted in a heat engine unit  20 . In this embodiment the heat engine is in the form of a gas turbine and is described as a gas turbine in the following. The combustion chamber comprises at least one exhaust gas outlet  30 , a housing  40 , at least one air intake  50 , a connecting member  60 , and supporting means  70 .  
         [0010]    The combustion chamber  10  is shown assembled between the connecting member  60  of the gas turbine unit  20  and the supporting means  70  located before a subsequent gas turbine stage (not shown). The combustion chamber has two ends, a first end  10   a  and a second end  10   b , wherein the housing  40  of the combustion chamber comprises two parts, a first part  80  and a second part  90 . The centre of the first part  80  coincides with the centre of the second part  90 , and the first part  80  and the second part  90  also form the second end  10   b  of the combustion chamber. The inner diameter of the first part  80  is larger than the outer diameter of the second part  90  for containing a portion of the second part, preferably a main portion. The difference in diameter forms a space between the first and second part, which creates the at least one air intake  50 . The air intake receives air, shown by an arrow C, from a compressor stage (not shown).  
         [0011]    The combustion chamber has its first end  10   a  in engagement with a suspension, arrangement  100  placed in the connecting flange  60 , and its second end  10   b  in engagement with and supported by the supporting means  70  in the form of a gas channel. The suspension arrangement comprises three symmetrically spaced springs, which are detachably attached to the first end  10   a  of the combustion chamber, but may have any number of springs, the most important is that the force of the springs on the combustion chamber is evenly transferred. The connecting flange  60  is rotary symmetrical and holds support members  110 , at least one gas inlet  120 , and at least one ignition member  130 , these parts point in the axial direction towards the combustion chamber  10  and are in engagement thereto. The support members  110  are attached to and holds a gas combustion part  140  in which, for example natural gas is delivered through the at least one gas inlet  120  and mixed with air delivered from the at least one air intake  50 , whereby the gas mixture is ignited by the at least one ignition member  130  and then delivered through the at least one gas outlet  30  into the supporting means  70  for further delivery to the gas turbine stage. The first part  80  of the combustion chamber  10  and the second part  90  are attached together by a detachable arrangement  180  at the second part  10   b  of the combustion chamber.  
         [0012]    The combustion chamber  10  may be manufactured in many ways, for example by wrapping a plate into a cylindrical shape, whereby the joint along its length is welded tight, here, the combustion chamber is preferably made by casting.  
         [0013]    The combustion chamber  10  preferably has a cylindrical cross-section but may have any other shape of the cross-section, which is obvious to a person skilled in the art. These different shapes depend on, e g available space in the gas turbine unit  20  or the design of the surrounding area delivering the combustion air and/or receiving the exhaust gas, for example the area receiving the exhaust gas may have a non-symmetrical shape, whereby the cross-section of the combustion chamber must have a cross-section that varies along its length in the radial direction, i e transversally in relation to its length, e g from a cylindrical shape at its first end  10   a  into an oval shape at its second end  10   b . Moreover, the cross-section of the combustion chamber  10  could have a quadratic or rectangular shape or even a cross-section with  5  sides forming a pentagon-shaped cross-section at one end or both ends, if required according to the demands described above. In order to improve the cooling of the combustion chamber, i e enhance the turbulence around the outer shape, any of the two parts  80  or  90  could have a rough inner or outer surface in the radial direction, i e transversally in relation to its centre axis, for example ribs, bulges or grooves extending radially around the whole periphery or portions of it.  
         [0014]    The supporting means  70  has a rotary symmetrical shape, preferably a cylindrical shape extending towards the combustion chamber  10  at one end and extending in the opposite direction towards the gas turbine stage at a second end. The combustion chamber may have a non-symmetrical shape if required, for example the two parts  80  and  90  of the housing  40  could have their centre axis displaced in relation to each other.  
         [0015]    The combustion chamber  10  is supported by the supporting means  70  by way of a spherical outer surface  150  provided at its second end  10   b  being in contact with a conical inner surface  160  of the supporting means during operation of the gas turbine unit  20 . The contact surface or support surface formed between the spherical outer surface and the conical inner surface has the shape of a tangential circumferential contact surface  170 , which allows tilting of the combustion chamber. FIG. 1 also shows an enlargement of the spherical outer surface  150  and the conical inner surface  160  for clarity reasons. The radius of the spherical outer surface is designated with an arrow R. The radius R is defined so that it fulfills the condition that the contact point between the spherical outer surface and the conical inner surface always is in a position on the conical inner surface which gives the largest moving area for the combustion chamber in both directions independently of how the combustion chamber tilts.  
         [0016]    The radius R may be in the interval of about 50-150 mm but the size of the radius R depends on several factors, e g the dimensions of the associated parts, especially the diameter of the combustion chamber  10  and also the conical angle of the conical inner surface. In this case, the preferred radius R for the spherical outer surface  150  is about 75-85 mm and most preferred about 80-85 mm when the conical angle at the conical inner surface  160  is 45°. Other conical angles is conceived by a man skilled in the art , e g a conical angle of 30° in combination with other dimensions of the combustion chamber would give another radius, i e these parameters depend on each other.  
         [0017]    The tilting function for the combustion chamber  10  is required as the combustion chamber  10  may, in some cases, have an askew position, due to an uneven thermal expansion and/or a non-uniform distribution of the surrounding pressure from adjacent parts expanding in different directions both radially and axially due to high temperatures, e g the supporting means  70  in the form of a gas conduit, which has to be compensated for by tilting the combustion chamber.  
         [0018]    Still, a sufficient sealing has to be maintained between the gas inside the combustion chamber  10  and the surrounding both in the possible askew position for the combustion chamber and during thermal expansion for associated parts and the combustion chamber. This is achieved by way of the suspension system  100  provided at the first end  10   a  of the combustion chamber  10 . The suspension system  100  in the form of springs bias the combustion chamber in the axial direction towards the supporting means  70 , whereby the second end  10   b  of the combustion chamber, i e the spherical outer surface  150 , is in contact with associated sealing surfaces, i e the conical inner surface  160 , at all times even though it tilts. The suspension system also permits movement of the combustion chamber during expansion or shrinking due to cooling in the axial direction.  
         [0019]    The first end  90   a  of the second part  90  of the combustion chamber  10  extends over a portion of the gas combustion part  140 , which has an outer guiding surface  170  in the direction towards the gas turbine stage. This guiding surface works as an axial expansion space when the combustion-chamber  10  expands axially due to thermal strain, i e heat expansion, when the gas turbine unit is operated. The main thermal axial expansion for the second part  90  of the combustion chamber  10  occurs in the direction towards the connecting flange  60 , i e in the expansion space of the guiding surface  170 , the second part  90  always overlapping the maximum distance that may be covered by the first end  90   a  of the second part  90  when shrinking due to cooling, whereby any build-up of strain or forces in the axial or radial direction is eliminated.  
         [0020]    The contact surface  170  created between the spherical outer surface  150  at the second end of the combustion chamber  10  and the conical inner surface  160  of the supporting means ensures that a sufficient sealing always is maintained independently of how much the exhaust diffusor  10  tilts. A sufficient sealing may also be achieved by placing the spherical surface on the supporting means  70  and the conical surface in the combustion chamber or designing both surfaces with a spherical shape. The conical inner surface  160  could also be placed on the outside of the supporting means  70  and the spherical surface  150  on the inside of the second end  10   b  of the combustion chamber.  
         [0021]    The spherical or conical surfaces may also be placed on an outer portion of the combustion chamber  10  between the first end  90   a  of the second part  90  of the combustion chamber and the second end  10   b  of the combustion chamber.  
         [0022]    The combustion chamber  10  is made of a heat resistant metal but can of course be made of any other material fulfilling the thermal demands, e g ceramics.